Detailed Description
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Fig. 1 is a plan view showing a polishing apparatus according to an embodiment of the present invention. The polishing apparatus is capable of performing a series of steps of polishing, cleaning, and drying a substrate surface such as a wafer. As shown in fig. 1, the polishing apparatus includes a substantially rectangular casing 60, and the interior of the casing 60 is divided into a loading/unloading section 61, a polishing section 63, and a cleaning section 70 by partition walls 60a and 60 b. The polishing device is provided with: a film thickness measuring device 80 for measuring the film thickness of the substrate; and an operation control unit 9 for controlling the operation of each constituent element of the polishing apparatus. The polishing section 63 is disposed between the loading/unloading section 61 and the cleaning section 70.
The film thickness measuring device 80 is configured to measure the film thickness of the substrate by utilizing interference of light, and can measure the film thickness profile of the substrate. The film thickness measuring device 80 of the present embodiment is a stand-alone film thickness measuring device. The film thickness measuring device 80 according to the present embodiment measures the film thickness of the substrate in a state where the substrate is stationary. One such film thickness measuring device is, for example, an ITM (In-line thickness monitor (In-line Thickness Monitor)).
The loading/unloading section 61 includes a plurality of load ports 65 for loading a substrate cassette accommodating a plurality of substrates therein. The loading/unloading section 61 is provided with a loader (transfer robot) 66 that is movable along the arrangement of the loading ports 65. The loader 66 is configured to access substrates mounted in the substrate cassette of the load port 65 and to convey the substrates to the film thickness measuring device 80. Further, the loader 66 has a function of reversing the substrate.
The polishing section 63 includes: a polishing member 1 for polishing a surface of a substrate; a first temporary placing table 67 and a second temporary placing table 68 for temporarily placing the substrate; and a transfer robot 69 for transferring the substrate among the polishing unit 1, the first stocker 67, and the second stocker 68. A swing conveyor 64 for conveying the substrate is disposed between the polishing section 63 and the cleaning section 70. The substrate polished by the polishing section 63 is transported to the cleaning section 70 by the swing conveyor 64.
The cleaning section 70 includes a first cleaning means 74, a second cleaning means 75, and a third cleaning means 76 for cleaning the substrate polished by the polishing section 63, and a drying means 77 for drying the substrate cleaned by the cleaning means 74, 75, 76. The cleaning section 70 further includes a linear conveyor 78 that conveys the substrate from the first cleaning module 74 to the second cleaning module 75, from the second cleaning module 75 to the third cleaning module 76, and from the third cleaning module 76 to the drying module 77.
Fig. 2 is a schematic diagram showing an embodiment of the polishing apparatus 1. As shown in fig. 1, the polishing unit 1 includes: a polishing table 3 for supporting the polishing pad 2; a polishing head 10 for pressing a substrate (e.g., a wafer) W against the polishing pad 2; a table motor 6 for rotating the polishing table 3; a polishing liquid supply nozzle 5 for supplying a polishing liquid such as slurry to the polishing pad 2; a film thickness sensor 20; a torque measuring device 8. The upper surface of the polishing pad 2 forms a polishing surface 2a for polishing the substrate W.
The polishing unit 1 further includes: a support shaft 14; a swing arm 16 coupled to an upper end of the support shaft 14; a head shaft 11 mounted to the free end of the swing arm 16; a polishing head motor 17 connected to the head shaft 11; and a swing motor 18 connected to the swing arm 16 for swinging the polishing head 10 along the polishing surface 2a. The polishing head 10 is connected to the lower end of the head shaft 11. The polishing head motor 17 of the present embodiment is disposed in the swing arm 16, but in one embodiment, the polishing head motor 17 may be disposed outside the swing arm 16.
The head shaft 11 is rotatably constituted by a polishing head motor 17. The polishing head 10 is connected to a swing arm 16 via a head shaft 11. The polishing head 10 is rotated by the head shaft 11, and the arrow indicates a direction to rotate around the head shaft 11 in the figure. The head shaft 11 is connected to a lifting mechanism, not shown. The polishing head 10 can be raised and lowered by a lifting mechanism via a head shaft 11. The swing motor 18 is disposed in the support shaft 14, and the swing arm 16 is configured to be rotatable (rotatable) about the support shaft 14. The polishing head 10 is moved between a receiving position, not shown, of the substrate W and an upper position of the polishing pad 2 by rotation of the swing arm 16. In one embodiment, the swing arm 16 may be fixed to the support shaft 14, and the swing motor 18 may be coupled to the support shaft 14, and the swing motor 18 may be configured to rotate the support shaft 14 and the swing arm 16 integrally with each other about the rotation axis of the support shaft 14.
The polishing table 3 is coupled to a table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in a direction indicated by an arrow in fig. 2. The rotation direction of the polishing head 10 and the polishing table 3 is not limited to this embodiment.
The polishing substrate W is as follows. While rotating the polishing table 3 and the polishing head 10 in the direction indicated by the arrow in fig. 2, the polishing liquid is supplied from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. The substrate W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 10 in a state where the polishing liquid is present on the polishing pad 2 while being rotated by the polishing head 10. The surface of the substrate W is polished by chemical action of the polishing liquid and mechanical action of the polishing particles or the polishing pad 2 contained in the polishing liquid.
In one embodiment, the polishing head 10 may be oscillated (i.e., reciprocated around the support shaft 14) along the polishing surface 2a by the oscillation motor 18 in a predetermined angular range to polish the substrate W. The swing motor 18 is mounted with an angle sensor 19 that detects the rotation angle of the swing arm 16 (i.e., the rotation angle of the polishing head 10 about the support shaft 14), and the operation control unit 9 controls the angle range of the swing motor 18 based on an angle signal from the angle sensor 19. The angle sensor 19 is, for example, a rotary encoder.
The operation control unit 9 includes: a storage device 9a storing a program; and a processing device 9b for executing an operation in accordance with a command included in the program. The processing device 9b includes a CPU (central processing unit), a GPU (graphics processing unit), or the like that performs operations in accordance with commands included in a program stored in the storage device 9 a. The storage device 9a includes: a main memory means (for example a random access memory) accessible to the processing means 9 b; and an auxiliary storage device (e.g., hard disk drive or solid state drive) storing data and programs. The operation control unit 9 is composed of at least 1 computer. However, the specific configuration of the operation control unit 9 is not limited to this example.
The film thickness measuring device 80, the table motor 6, the polishing liquid supply nozzle 5, the film thickness sensor 20, the torque measuring device 8, the polishing head motor 17, the swing motor 18, the angle sensor 19, and the lifting device (not shown) are electrically connected to the operation control unit 9. The operations of the film thickness measuring device 80, the table motor 6, the polishing liquid supply nozzle 5, the film thickness sensor 20, the torque measuring device 8, the polishing head motor 17, the swing motor 18, the angle sensor 19, and the lifting device are controlled by the operation control unit 9.
The torque measuring device 8 is connected to the table motor 6. The torque measuring device 8 of the present embodiment is configured to measure the torque for rotating the polishing table 3. During polishing of the substrate W, the polishing table 3 is driven by the table motor 6 to rotate at a constant speed. Therefore, when the torque required for rotating the polishing table 3 at a constant speed is changed, the drive current of the table motor 6 is changed.
The torque for rotating the polishing table 3 is a torque of a force for rotating the polishing table 3 around the axis CP. The torque for rotating the polishing table 3 corresponds to the drive current of the table motor 6. Therefore, the torque measuring device 8 of the present embodiment is a current measuring device for measuring the driving current of the table motor 6. In one embodiment, the torque measuring device 8 may be constituted by at least a part of a motor driver for driving the table motor 6. At this time, the motor driver determines a current value required for rotating the polishing table 3 at a constant speed, and outputs the determined current value. The determined current value corresponds to a torque for rotating the polishing table 3. The measured value of the torque (driving current of the table motor 6) for rotating the polishing table 3 is transmitted to the operation control unit 9.
The film thickness sensor 20 outputs a film thickness signal that varies according to the film thickness of the substrate W. The film thickness signal is a numerical value or data directly or indirectly indicating the film thickness. The film thickness sensor 20 of the present embodiment is an optical film thickness sensor. The optical film thickness sensor irradiates light on the surface of the substrate W, measures the intensity of the reflected light from the substrate W for each wavelength, and outputs intensity measurement data of the reflected light associated with the wavelength. The intensity measurement data of the reflected light associated with the wavelength is a film thickness signal that varies according to the film thickness of the substrate W.
The film thickness sensor 20 includes: a light source 24 that emits light; a beam splitter 27; an optical sensor head 21 coupled to the light source 24 and the beam splitter 27. The optical sensor head 21, the light source 24, and the beam splitter 27 are mounted on the polishing table 3, and rotate integrally with the polishing table 3 and the polishing pad 2. The position of the optical sensor head 21 is a position at which the polishing table 3 and the polishing pad 2 pass over the surface of the substrate W on the polishing pad 2 every one rotation.
Light emitted from the light source 24 is transmitted to the optical sensor head 21, and is guided from the optical sensor head 21 to the surface of the substrate W. The light is reflected by the surface of the substrate W, and the reflected light from the surface of the substrate W is received by the optical sensor head 21 and sent to the spectroscope 27. The beam splitter 27 splits the reflected light according to wavelength, and measures the intensity of the reflected light at each wavelength. The intensity measurement data of the reflected light is sent to the operation control unit 9. The operation control unit 9 generates a spectrum of the reflected light from the intensity measurement data of the reflected light, and determines the film thickness of the substrate W based on the spectrum. The spectrum of the reflected light is represented by a curve (i.e., a spectral waveform) representing the relationship between the wavelength and the intensity of the reflected light. The intensity of the reflected light can be expressed by a relative value such as a reflectance or a relative reflectance.
Fig. 3 is a diagram showing an example of a spectrum generated by the operation control unit 9. The spectrum is represented as a curve (i.e., a spectroscopic waveform) representing the relationship between the wavelength and the intensity of light. In fig. 3, the horizontal axis represents the wavelength of light reflected from the substrate, and the vertical axis represents the relative reflectance derived from the intensity of the reflected light. The relative reflectance is an index value indicating the intensity of reflected light, and is a ratio of the intensity of light to a predetermined reference intensity. By dividing the intensity of light (measured intensity) by a predetermined reference intensity at each wavelength, unnecessary noise such as intensity fluctuation inherent to the optical system of the device and the light source can be removed from the measured intensity.
The reference intensity is the intensity of light measured in advance for each wavelength, and the relative reflectance is calculated for each wavelength. Specifically, the relative reflectance is obtained by dividing the intensity of light of each wavelength (measured intensity) by the corresponding reference intensity. The reference intensity can be obtained by, for example, directly measuring the intensity of light emitted from the optical sensor head 21, or by irradiating light onto a silicon substrate (bare substrate) on which a film has not been formed, and measuring the intensity of reflected light from the bare substrate.
The actual polishing is performed to obtain a corrected measured intensity by subtracting a black level (background intensity obtained under light shielding conditions) from the measured intensity, and further to obtain a corrected reference intensity by subtracting the black level from the reference intensity, and then to obtain the relative reflectance by dividing the corrected measured intensity by the corrected reference intensity. Specifically, the relative reflectance R (λ) can be obtained by using the following formula (1).
[ formula 1]
Where λ is the wavelength λ of light reflected from the substrate, E (λ) is the intensity of the wavelength λ, B (λ) is the reference intensity of the wavelength λ, and D (λ) is the background intensity (black level) of the wavelength λ measured under the condition of shielding light.
The optical sensor head 21 guides light to the surface (surface to be polished) of the substrate W and receives reflected light from the substrate W every time the polishing table 3 rotates one revolution. The reflected light is sent to a beam splitter 27. The beam splitter 27 splits the reflected light according to wavelength, and measures the intensity of the reflected light at each wavelength. The intensity measurement data of the reflected light is sent to the operation control unit 9, and the operation control unit 9 generates a spectrum as shown in fig. 3 from the intensity measurement data of the reflected light. Further, the operation control unit 9 determines the film thickness of the substrate W from the spectrum of the reflected light. The spectrum of the reflected light varies with the film thickness of the substrate W. Therefore, the operation control unit 9 can determine the film thickness of the substrate W from the spectrum of the reflected light. In the following description, a spectrum generated by the reflected light from the substrate W to be polished is referred to as a measurement spectrum.
The film thickness sensor 20 of the present embodiment is configured to output a plurality of pieces of intensity measurement data at a plurality of measurement points on the substrate W. In the present embodiment, the optical sensor head 21 emits light to a plurality of measurement points on the substrate W and receives reflected light from the plurality of measurement points while the optical sensor head 21 passes through the substrate W once. In the present embodiment, only one optical sensor head 21 is provided in the polishing table 3, but a plurality of optical sensor heads 21 may be provided in the polishing table 3.
Fig. 4 is a schematic diagram showing an example of a plurality of measurement points on the surface (surface to be polished) of the substrate W. As shown in fig. 4, the optical sensor head 21 guides light to a plurality of measurement points MP each time it passes through the substrate W, and receives reflected light from the plurality of measurement points MP. Therefore, the operation control unit 9 generates a plurality of measurement spectra of the reflected light from the plurality of measurement points MP every time the optical sensor head 21 passes through the substrate W (that is, every time the polishing table 3 rotates one revolution), and determines (measures) the film thickness at each of the measurement points MP based on the plurality of measurement spectra. The position of each measurement point MP is determined based on the light irradiation timing, the rotation speed of the polishing table 3, the position of the polishing head 10, the rotation speed of the polishing head 10, and the like.
The operation control unit 9 is configured to determine (measure) the film thickness based on a comparison between a measured spectrum (also referred to as film measurement data) and a plurality of reference spectra (also referred to as reference film data). The operation control unit 9 compares a measured spectrum generated during polishing of the substrate W with a plurality of reference spectra to determine a reference spectrum having a shape closest to the measured spectrum, and determines a film thickness associated with the determined reference spectrum. The reference spectrum closest in shape to the measured spectrum is the spectrum with the smallest difference in relative reflectivity between the reference spectrum and the measured spectrum.
The plurality of reference spectra are obtained in advance by polishing a reference wafer (or a reference substrate) having the same laminated structure as a substrate W to be polished (hereinafter, referred to as a target wafer or a target substrate). Each reference spectrum is associated with the film thickness at the time of obtaining the reference spectrum. That is, each reference spectrum is acquired at different film thicknesses, and a plurality of reference spectra correspond to a plurality of different film thicknesses. Therefore, the current film thickness of the substrate W can be determined (measured) by the reference spectrum having a specific shape closest to the measured spectrum.
An example of a process for obtaining a plurality of reference spectra will be described. First, a reference wafer having the same laminated structure as the target substrate W is prepared. The reference wafer is conveyed to a film thickness measuring device 80 (see fig. 1), and the initial film thickness of the reference wafer is measured by the film thickness measuring device 80. The initial film thickness of the reference wafer is the film thickness of the reference wafer before polishing. Next, the reference wafer is transported to the polishing unit 1, and the reference wafer is polished while slurry as a polishing liquid is supplied onto the polishing pad 2. In reference wafer polishing, as described above, light is irradiated onto the surface of the reference wafer, and the spectrum of the reflected light from the reference wafer (i.e., the reference spectrum) is obtained. The reference spectrum is obtained for each rotation of the polishing table 3. Thus, a plurality of reference spectra are acquired in reference wafer polishing. After polishing of the reference wafer, the reference wafer is again conveyed to the film thickness measuring device 80, and the film thickness (i.e., the final film thickness) of the polished reference wafer is measured.
The operation control unit 9 calculates the film thickness corresponding to each reference spectrum based on a relational expression indicating the relationship between the film thickness of the reference wafer and the polishing time of the reference wafer. Since the reference spectrum is periodically obtained every one rotation of the polishing platen 3 as described above, the polishing time when each reference spectrum is obtained can be calculated from the rotation speed and the number of rotations of the polishing platen 3. That is, the operation control unit 9 uses the polishing time set for obtaining each reference spectrum in the above-described relational expression, thereby calculating the film thickness corresponding to each reference spectrum. Thus, a plurality of reference spectra corresponding to different film thicknesses are obtained.
FIG. 5 is a graph showing the relationship between the film thickness of a reference wafer and polishing time when the polishing rate is constant. When the polishing rate of the reference wafer is constant, as shown in fig. 5, the film thickness linearly decreases with the polishing time. That is, when the polishing rate of the reference wafer is constant, the above-described relational expression can be expressed using a linear function including the polishing rate. When the polishing rate is constant, the polishing rate can be calculated by dividing the difference between the initial film thickness Tini and the final film thickness Tfin by the polishing time t to reach the final film thickness Tfin. The operation control unit 9 determines the above-described relational expression based on the calculated polishing rate.
When the substrate W or the reference wafer to be polished has a step of roughness on its surface (surface to be polished), the polishing rate changes according to the state of the film to be polished. When the layer under the polishing target film has a step of irregularities, the polishing target film also has a step of irregularities according to the structure of the layer under the polishing target film. Fig. 6 is a cross-sectional view showing an embodiment of a substrate having a step of roughness. The substrate shown in FIG. 6 is a substrate in which a convex portion of a silicon (Si) layer 100 having a concave-convex step is formed of silicon nitride (Si)3 N4 ) A stop layer 101 is formed, and a polishing target film 102 having a step of roughness is formed on the stop layer 101. The film 102 to be polished of the present embodiment is made of silicon dioxide (SiO2 ) An insulating film is formed. The laminated structure shown in fig. 6 is, for example, shallow Trench Isolation (STI).
The polishing rates of the concave and convex portions are different, and the difference in the predicted polishing rate becomes smaller when the step is smaller.
As described above, since the convex portion is polished preferentially before the step eliminating film thickness Td is reached, the polishing rate of the polishing target film 102 before the step eliminating film thickness Td is reached is larger than the polishing rate after the step eliminating film thickness Td is reached. Therefore, the relation between the film thickness of the reference wafer (film thickness of the polishing target film) and the polishing time, which indicates that the polishing target film has the uneven level difference, is different before and after the level difference elimination point.
Fig. 7A and 7B are graphs showing the relationship between the film thickness of a reference wafer having a polishing target film with a rough level difference and the polishing time. As shown in fig. 7A and 7B, when the polishing target film has a step of roughness, a relational expression indicating a relation between the film thickness of the reference wafer (film thickness of the polishing target film) and the polishing time includes: a first relational expression indicating a relation between a film thickness of the reference wafer (film thickness of the polishing target film) and a polishing time in a period from the initial film thickness Tini to the step-elimination film thickness Td; and a second relation between the thickness of the reference wafer (the thickness of the polishing target film) and the polishing time in the period from the step-elimination film thickness Td to the final film thickness Tfin.
The film thickness corresponding to each reference spectrum is calculated based on the first relational expression and the second relational expression. The polishing rate is constant from the step-difference eliminating film thickness Td to the final film thickness Tfin in the present embodiment. In this case, the second relation may be expressed by using a linear function including the polishing rate. When the polishing rate is constant, the polishing rate of the second relational expression can be calculated by dividing the difference between the step-difference eliminating film thickness Td and the final film thickness Tfin by the polishing time t2 from the step-difference eliminating film thickness Td to the time when the final film thickness Tfin is reached. The operation control unit 9 determines a second relational expression based on the calculated polishing rate. The step-eliminating film thickness Td is measured by the film thickness measuring device 80 at the time when the step-eliminating point is reached.
In one embodiment, the step-difference eliminating film thickness Td is determined as follows. The film thickness profile of the reference wafer is measured by the film thickness measuring device 80 every constant time during the period until the film thickness of the reference wafer reaches the step difference eliminating film thickness Td. The operation control unit 9 compares the measured protrusion film thickness (average protrusion film thickness) of the film thickness profile with a predetermined protrusion threshold value, and determines the film thickness of the polishing target film when the protrusion film thickness (average protrusion film thickness) reaches the protrusion threshold value as the step-elimination film thickness Td. In one embodiment, the timing at which the film thickness of the reference wafer reaches the step-difference eliminating film thickness Td may be detected by a change in the torque current value (the drive current of the table motor 6, the drive current of the polishing head motor 17, or the drive current of the wobble motor 18 described later) by a method other than the above.
In the example shown in fig. 7A, the polishing rate is constant during the period from the initial film thickness Tini to the step-difference eliminating film thickness Td. Thus, the first relationship shown in FIG. 7A can be expressed using a linear function that includes the polishing rate. The polishing rate of the first relation shown in fig. 7A can be calculated by dividing the difference between the initial film thickness Tini and the step-difference eliminating film thickness Td by the polishing time t1 from the initial film thickness Tini to the time when the step-difference eliminating film thickness Td is reached. The operation control unit 9 determines a first relational expression based on the calculated polishing rate.
In the example shown in fig. 7B, the polishing rate gradually decreases until the step-difference eliminating film thickness Td is reached. An example of the method for determining the first relational expression in the example shown in fig. 7B is shown below. During the period until the step-difference eliminating film thickness Td is reached, a plurality of film thicknesses are measured by the film thickness measuring device 80 in polishing times different from each other. The measurement data of these plural film thicknesses are marked on a coordinate system having a vertical axis indicating the film thickness and a horizontal axis indicating the polishing time. Regression equations are determined by performing regression analysis on these multiple data points. The regression equation is the first relationship equation. The first relation in the example shown in fig. 7B may be expressed using, for example, a quadratic function.
In the example shown in fig. 7A and 7B, the polishing rate is constant from the step-difference eliminating film thickness Td to the final film thickness Tfin, but the polishing rate may not be constant from the step-difference eliminating film thickness Td to the final film thickness Tfin. Therefore, in one embodiment, a plurality of film thicknesses may be measured by the film thickness measuring device 80 at different polishing times from the step elimination film thickness Td to the final film thickness Tfin of the reference wafer. The measurement data of the plurality of film thicknesses may be labeled on a coordinate system having a vertical axis indicating the film thickness and a horizontal axis indicating the polishing time, and a regression equation may be determined by performing regression analysis on the plurality of data points, and the regression equation may be used as the second relational expression. One embodiment is that the second relation may be represented using, for example, a quadratic function.
One embodiment is that the film thickness sensor 20 may also be an eddy current sensor. The eddy current sensor generates an eddy current by passing a magnetic flux through a sensor coil of the eddy current sensor in a conductive film of the substrate W, detects the eddy current according to the film thickness of the substrate W, and outputs an eddy current signal. The eddy current signal is a film thickness signal that varies with the film thickness of the substrate W. The eddy current signal is sent to the operation control unit 9. The operation control unit 9 determines the film thickness of the substrate W based on the eddy current signal. The film thickness sensor 20 detects eddy currents every time the polishing table 3 rotates one revolution, and detects eddy currents at a plurality of measurement points MP during one pass through the substrate W, and outputs eddy current signals at the respective measurement points MP, as in the embodiment described with reference to fig. 4. The operation control unit 9 determines the film thickness at each measurement point MP based on the plurality of eddy current signals. Hereinafter, the present specification refers to a measured value of an eddy current signal (magnitude of an eddy current signal) detected from a target substrate as a measured eddy current value.
The operation control unit 9 is configured to determine the film thickness from a comparison between the measured eddy current value and the reference eddy current value. The operation control unit 9 compares the measured eddy current value measured during polishing of the substrate W with a plurality of reference eddy current values, specifies a reference eddy current value closest to the measured eddy current value, and determines a film thickness associated with the determined reference eddy current value. The reference eddy current value is a measured value of an eddy current signal detected from a reference wafer (reference substrate) having the same laminated structure as the target substrate, and a plurality of reference eddy current values are obtained in advance by grinding the reference wafer (reference substrate).
Hereinafter, the measured spectrum and the measured eddy current value will be collectively referred to as film measurement data, and the reference spectrum and the reference eddy current value will be collectively referred to as reference film data. In other words, the film measurement data is data including film thickness information of the target substrate obtained based on the film thickness signal from the film thickness sensor 20, and the reference film data is data including film thickness information of the reference substrate obtained based on the film thickness signal from the film thickness sensor 20. The step of obtaining the reference eddy current value is similar to the step of obtaining the reference spectrum described above unless otherwise specified. The reference spectrum acquisition step is also applicable to the reference eddy current value acquisition step by rewriting the reference spectrum to the reference eddy current value.
Each reference eddy current value is correlated with the film thickness at the time of obtaining the reference eddy current value. The operation control unit 9 calculates the film thickness corresponding to each reference eddy current value based on a relational expression indicating the relationship between the film thickness of the reference wafer and the polishing time of the reference wafer. When the polishing target film of the reference wafer has a step of roughness, the film thickness corresponding to each reference eddy current value is calculated based on the first relational expression and the second relational expression, as in the embodiment described with reference to fig. 6 to 7.
When the step-difference eliminating film thicknesses Td of the plurality of target substrates differ depending on variations in initial film thickness or different structures, a plurality of reference film data are obtained while polishing each reference wafer having the same structure as each target substrate before polishing each target substrate. The operation control unit 9 determines the film thickness of each target substrate by comparing the film measurement data obtained during polishing of each target substrate with a plurality of reference film data of each reference wafer corresponding to each target substrate.
Next, the polishing head 10 will be described in detail. Fig. 8 is a cross-sectional view of the polishing head 10 shown in fig. 2. As shown in fig. 8, the polishing head 10 includes: an elastic film 45 for pressing the substrate W against the polishing surface 2a of the polishing pad 2; a head main body 13 holding an elastic film 45; an annular drive ring 42 disposed below the head main body 13; and an annular retaining ring 40 fixed to the lower surface of the drive ring 42. The elastic membrane 45 is mounted on the lower portion of the head main body 13. The head main body 13 is fixed to an end portion of the head shaft 11, and the head main body 13, the elastic membrane 45, the drive ring 42, and the grommet 40 are integrally rotated by rotation of the head shaft 11. The clasp 40 and the drive ring 42 are configured to be movable up and down relative to the head main body 13. The head main body 13 is formed of a resin such as engineering plastic (for example, PEEK).
The lower surface of the elastic film 45 forms a substrate pressing surface 45a that presses the substrate W against the polishing surface 2a of the polishing pad 2. The retaining ring 40 is disposed so as to surround the substrate pressing surface 45a, and the substrate W is surrounded by the retaining ring 40. Four pressure chambers 46, 47, 48, 49 are provided between the elastic membrane 45 and the head main body 13. The pressure chambers 46, 47, 48, 49 are formed by the elastic membrane 45 and the head main body 13. The central pressure chamber 46 is circular and the other pressure chambers 47, 48, 49 are annular. The pressure chambers 46, 47, 48, 49 are arranged concentrically.
Gas delivery lines F1, F2, F3, F4 are connected to the pressure chambers 46, 47, 48, 49, respectively. One end of the gas delivery lines F1, F2, F3, F4 is connected to a compressed gas supply source (not shown) as a utility provided in a factory where the polishing apparatus is provided. Compressed gas such as compressed air is supplied to the pressure chambers 46, 47, 48, 49 through the gas delivery lines F1, F2, F3, F4, respectively. By supplying the compressed gas into the pressure chambers 46 to 49, the elastic membrane 45 expands, and the compressed gas in the pressure chambers 46 to 49 presses the substrate W against the polishing surface 2a of the polishing pad 2 via the elastic membrane 45.
The gas delivery line F3 communicating with the pressure chamber 48 is connected to a vacuum line, not shown, and a vacuum can be formed in the pressure chamber 48. An opening is formed in a portion of the elastic membrane 45 that constitutes the pressure chamber 48, and vacuum is formed in the pressure chamber 48, thereby holding the substrate W to the polishing head 10 by suction. Further, by supplying compressed gas into the pressure chamber 48, the substrate W is released from the polishing head 10. The elastic film 45 is formed of a rubber material having excellent strength and durability such as ethylene propylene rubber (EPDM).
The grommet 40 is an annular member that contacts the polishing surface 2a. The retaining ring 40 is disposed so as to surround the outer periphery of the substrate W, and prevents the substrate W from jumping out of the polishing head 10 during polishing of the substrate W.
The upper portion of the drive ring 42 is coupled to an annular buckle pressing device 52. The grommet pressing device 52 applies a downward load to the entire lower face of the grommet 40 via the drive ring 42, thereby pressing the lower face of the grommet 40 against the abrasive face 2a.
The buckle pressing device 52 includes: an annular piston 53 fixed to an upper portion of the drive ring 42; and an annular rolling diaphragm 54 connected to the upper surface of the piston 53. A grommet pressure chamber 50 is formed inside the rolling diaphragm 54. The grommet pressure chamber 50 is connected to the compressed gas supply source via a gas delivery line F5. The compressed gas is supplied into the grommet pressure chamber 50 through the gas delivery line F5.
When compressed gas is supplied from the compressed gas supply source to the grommet pressure chamber 50, the rolling diaphragm 54 presses the piston 53 downward. The piston 53 presses the drive ring 42 and the snap ring 40 downward. Thus, the clasp pressing device 52 presses the lower surface of the clasp 40 against the polishing surface 2a.
The gas delivery lines F1, F2, F3, F4, F5 extend through a rotary joint 15 attached to the head shaft 11. The polishing unit 1 further includes pressure regulators R1, R2, R3, R4, and R5, and the pressure regulators R1, R2, R3, R4, and R5 are provided in the gas delivery lines F1, F2, F3, F4, and F5, respectively. The compressed gas from the compressed gas supply source is supplied to the pressure chambers 46 to 49 and the grommet pressure chamber 50 independently through the pressure regulators R1 to R5, respectively. The pressure regulators R1 to R5 are configured to regulate the pressure of the compressed gas in the pressure chambers 46 to 49 and the grommet pressure chamber 50. The pressure regulators R1 to R5 are connected to the operation control unit 9.
The pressure regulators R1 to R5 can independently change the internal pressures of the pressure chambers 46 to 49 and the grommet pressure chamber 50, and thus can independently adjust the pressing force of the substrate W against the polishing surface 2a and the pressing force of the grommet 40 against the polishing pad 2 in four areas of the substrate W corresponding to the pressure chambers 46 to 49, that is, in the center portion, the inner middle portion, the outer middle portion, and the edge portion. The gas delivery lines F1, F2, F3, F4, and F5 are also connected to atmosphere opening valves (not shown), respectively, and may open the pressure chambers 46 to 49 and the grommet pressure chamber 50 to the atmosphere. In one embodiment, the elastic membrane 45 may form less than four or more than four pressure chambers.
Fig. 9 is a schematic diagram showing another embodiment of the polishing apparatus 1. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the embodiment shown in fig. 2, and thus, a repetitive description thereof will be omitted. As shown in fig. 9, in the present embodiment, the torque measuring device 8 is connected to the polishing head motor 17. The torque measuring device 8 of the present embodiment is configured to measure a torque for rotating the polishing head 10. During polishing of the substrate W, the polishing head 10 is driven by the polishing head motor 17 through the head shaft 11 so as to rotate at a constant speed. Therefore, when the torque required to rotate the polishing head 10 at a constant speed is changed, the drive current of the polishing head motor 17 is changed. In the present embodiment, the torque measuring device 8 is disposed in the swing arm 16, but in one embodiment, the torque measuring device 8 may be disposed outside the swing arm 16.
The torque for rotating the polishing head 10 is a torque of a force for rotating the polishing head 10 around the axis of the head shaft 11. The torque for rotating the polishing head 10 corresponds to the drive current of the polishing head motor 17. Therefore, the torque measuring device 8 of the present embodiment is a current measuring device for measuring the drive current of the polishing head motor 17. In one embodiment, the torque measuring device 8 may be constituted by at least a part of a motor driver for driving the polishing head motor 17. At this time, the motor driver determines a current value required for rotating the polishing head motor 17 at a constant speed, and outputs the determined current value. The determined current value corresponds to a torque for rotating the polishing head 10. The measured value of the torque (drive current of the polishing head motor 17) for rotating the polishing head 10 is sent to the operation control unit 9.
Fig. 10 shows a schematic view of still another embodiment of the polishing assembly 1. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the embodiment shown in fig. 2, and thus, a repetitive description thereof will be omitted. As shown in fig. 10, in the present embodiment, the torque measuring device 8 is connected to the swing motor 18. The torque measuring device 8 of the present embodiment is configured to measure torque for swinging the polishing head 10 along the polishing surface 2a, that is, torque for rotating the polishing head 10 about the support shaft 14. When polishing the substrate W while swinging the polishing head 10 in a predetermined angular range, the swing motor 18 swings the polishing head 10 on the polishing surface 2a at a constant speed (a reciprocating rotational motion about the support shaft 14 as a center) during polishing of the substrate W. Therefore, when the torque required for swinging the polishing head 10 at a constant speed (reciprocating around the support shaft 14) is changed, the driving current of the swing motor 18 is changed. In the present embodiment, the torque measuring device 8 is disposed in the support shaft 14, but in one embodiment, the torque measuring device 8 may be disposed outside the support shaft 14.
The torque for swinging the polishing head 10 along the polishing surface 2a is a force torque for reciprocating the polishing head 10 around the axis of the support shaft 14. The torque for swinging the polishing head 10 corresponds to the driving current of the swing motor 18. Therefore, the torque measuring device 8 of the present embodiment is a current measuring device for measuring the driving current of the swing motor 18. The current for reciprocating the swing motor 18 at a constant speed is an alternating current. Therefore, in one embodiment, the torque measuring device 8 may calculate an effective value of the driving current of the swing motor 18, which is an ac current, and output the calculated effective value as a measured value of the driving current of the swing motor 18.
In one embodiment, the torque measuring device 8 may be constituted by at least a part of a motor driver that drives the swing motor 18. At this time, the motor driver determines a current value required for reciprocating the swing motor 18 at a constant speed, and outputs the determined current value. The determined current value corresponds to a torque for swinging the polishing head 10. One embodiment may also determine an effective value of the current required to reciprocally rotate the swing motor 18 at a constant speed by a motor driver that drives the swing motor 18, and output the effective value as the current required to reciprocally rotate the swing motor 18 at a constant speed. The measured value of the torque (driving current of the swing motor 18) for swinging the polishing head 10 along the polishing surface 2a is sent to the operation control unit 9.
Next, a polishing method of a substrate having a surface (surface to be polished) with a step of roughness will be described. The polishing method described below is performed while estimating the step elimination point based on the torque waveform (the drive current waveform of the table motor 6, the drive current waveform of the polishing head motor 17, or the drive current waveform of the swing motor 18), but in order to perform this polishing method, it is necessary to store data of a lot of torque waveforms. In one embodiment, the substrate W is polished while the film thickness of the substrate W is measured by the film thickness measuring device 80 before storing data of a sufficient torque waveform in order to estimate the film thickness of the substrate W based on the current torque waveform.
Fig. 11 and 12 are flowcharts showing one embodiment of a polishing method for a reference substrate, and fig. 13 to 18 are flowcharts showing one embodiment of a polishing method for a substrate having a surface (surface to be polished) with a step of roughness. The flowcharts shown in fig. 13 to 18 show a polishing method of the substrate W in a state where data of a sufficient torque waveform has not been stored. The substrate W to be polished is, for example, the substrate shown in fig. 6, but the substrate to be polished is not limited to the substrate shown in fig. 6. In this embodiment, before the polishing step of the substrate W, a reference substrate having the same laminated structure as the substrate W as the target substrate is polished in order to obtain the reference film data and the first and second relational expressions. The polishing device polishes the reference substrate while acquiring a plurality of reference film data.
In the present embodiment, the polishing apparatus polishes the reference substrate and the target substrate W while measuring a torque (driving current of the table motor 6) for rotating the polishing table 3, a torque (driving current of the polishing head motor 17) for rotating the polishing head 10 around the axis thereof, or a torque (driving current of the swing motor 18) for swinging the polishing head 10 along the polishing surface 2 a. In the polishing step, the operation control unit 9 generates a torque waveform based on the measured value of the torque. The torque waveform is a waveform in which a driving current of a motor required for relatively moving the substrate with respect to the polishing surface 2a passes through with time so as to overcome friction between the substrate and the polishing surface 2a of the polishing pad 2. For example, the torque waveform is represented as a graph showing a relationship between torque for rotating the polishing table 3 (or the polishing head motor 17 or the swing motor 18) and polishing time. Hereinafter, in this specification, the torque waveform of the torque for rotating the polishing table 3, the torque waveform of the torque for rotating the polishing head 10 around the axis thereof, and the torque waveform of the torque for swinging the polishing head 10 along the polishing surface 2a are collectively referred to simply as torque waveforms.
An embodiment of a polishing method for a reference substrate is described below with reference to fig. 11 and 12. Step 1-1 to step 1-8 (refer to fig. 11) are polishing steps before step removal of the reference substrate is performed. Step 1-1 is to measure the initial film thickness (film thickness before polishing) of the reference substrate by the film thickness measuring device 80. The film thickness measuring device 80 measures a plurality of film thicknesses (film thickness profile) at a plurality of measurement points on the reference substrate before polishing. In step 1-2, the polishing apparatus starts polishing the reference substrate. That is, the platen motor 6 rotates the polishing platen 3 and the polishing pad 2 integrally at a constant rotational speed, and the polishing head 10 rotates the reference substrate at a constant rotational speed. The polishing head 10 further presses the reference substrate against the polishing surface 2a of the polishing pad 2, and starts polishing the reference substrate. In one embodiment, the polishing head 10 may be swung along the polishing surface 2a by the swing motor 18 in a predetermined angle range to polish the reference substrate.
In step 1-3, a plurality of reference film data (reference spectrum or reference eddy current value) at a plurality of measurement points on the reference substrate is acquired while grinding the reference substrate. The operation control unit 9 periodically acquires a plurality of pieces of reference film data from a plurality of measurement points each time the film thickness sensor 20 passes through the reference substrate (that is, each time the polishing table 3 rotates one revolution). The plurality of reference film data are stored in the memory device 9a of the operation control unit 9.
In step 1-4, it is determined whether or not it is time to measure the film thickness profile of the reference substrate. Specifically, the operation control unit 9 compares the current polishing time (the difference between the current polishing time and the polishing time when the film thickness profile of the reference substrate is finally measured after performing steps 1 to 5 described later) with a predetermined film thickness measurement time, and temporarily stops polishing the reference substrate when the current polishing time reaches the film thickness measurement time. Then, the reference substrate is conveyed to the film thickness measuring device 80, and the film thickness profile of the reference substrate is measured by the film thickness measuring device 80 (steps 1 to 5). The measurement data of the film thickness profile is transmitted to the operation control unit 9. And when the current polishing time does not reach the film thickness measuring time, executing the steps 1-3 again.
In steps 1 to 6, the operation control unit 9 determines whether or not the film thickness of the reference substrate corresponding to the measured film thickness profile has reached the step-difference eliminating film thickness. Specifically, the operation control unit 9 compares the measured convex portion film thickness (average film thickness of the convex portion) of the reference substrate with a predetermined convex portion threshold value, and determines that the film thickness of the reference substrate has reached the step-difference eliminating film thickness when the film thickness of the convex portion (average film thickness of the convex portion) has reached the convex portion threshold value. When the operation control unit 9 determines that the film thickness of the substrate W has reached the step-difference-eliminating film thickness, it ends polishing before step elimination, and performs steps 1 to 7 described later. When the operation control unit 9 determines that the film thickness of the substrate W has not reached the step-difference eliminating film thickness, the steps 1 to 3 and subsequent steps are executed again. The film thickness profile of the reference substrate is measured a plurality of times in different polishing times until the film thickness of the reference substrate reaches the step-difference eliminating film thickness.
In one embodiment, the operation control unit 9 may compare the measured recess film thickness (average recess film thickness) of the film thickness profile with a predetermined recess threshold value, and determine that the film thickness of the reference substrate has reached the step-difference-eliminating film thickness when the recess film thickness (average recess film thickness) reaches the recess threshold value. In one embodiment, the operation control unit 9 may calculate a difference between the convex portion film thickness (average film thickness of the convex portion) of the measured film thickness profile and the concave portion film thickness (average film thickness of the concave portion) of the measured film thickness profile, compare the calculated difference with a predetermined uneven difference threshold, and determine that the film thickness of the reference substrate reaches the step-difference eliminating film thickness when the difference reaches the uneven difference threshold.
In one embodiment, the operation control unit 9 may calculate a plurality of film thickness variations at a plurality of measurement points on the reference substrate measured in the steps 1 to 5, compare the variations with a predetermined variation threshold, and determine that the film thickness of the reference substrate has reached the step-difference-eliminating film thickness when the variations are equal to or greater than (or equal to) the variation threshold. The fluctuation is, for example, standard deviation of a plurality of film thicknesses at a plurality of measurement points.
As described above, the torque waveform is generated during polishing of the reference substrate. In one embodiment, the operation control unit 9 may determine whether or not the film thickness of the reference substrate has reached the step-elimination film thickness based on a change in the torque waveform (torque waveform of the torque for rotating the polishing table 3, torque waveform of the torque for rotating the polishing head 10 around the axis thereof, or torque waveform of the torque for swinging the polishing head 10 along the polishing surface 2 a). In this case, steps 1-4 and 1-5 may not be executed, or when the operation control unit 9 determines that the film thickness profile of the reference substrate is not measured in step 1-4, steps 1-6 may be executed (that is, it is determined whether the film thickness of the reference substrate reaches the step-difference-eliminating film thickness based on the change in the torque waveform).
Specifically, the operation control unit 9 calculates a differential value of the torque waveform, compares the differential value with a predetermined differential threshold value, and determines that the film thickness of the reference substrate reaches the step-difference-eliminating film thickness when the differential value is equal to or smaller than the differential threshold value. The differential value of the torque waveform is obtained by calculating the rate of change of the torque with respect to the polishing time (i.e., the rate of change of the torque).
Fig. 19 is an example of torque waveforms when a substrate having a rough surface is polished. Specifically, fig. 19 shows waveforms of driving currents of the table motor 6 when the substrate shown in fig. 6 is polished. As shown in fig. 19, the drive current of the table motor 6 starts to rise after a constant time elapses from the start of polishing. This is because the contact area between the concave portion and the polishing pad 2 increases when polishing the convex portion having the uneven step is performed. The timing at which the drive current of the table motor 6 starts to rise is defined as a start rising point a.
Further, when the convex portion is polished, the slope (differential value) of the torque waveform starts to gradually decrease. After the convex portion is completely polished (after the torque waveform reaches the step elimination point B), the drive current of the stage motor 6 does not rise. Therefore, the step-difference elimination point can be detected based on the differential value of the torque waveform. When the layer under the polishing target film (in the example shown in fig. 6, the stop layer 101) starts to be exposed, the drive current of the table motor 6 starts to decrease. The point at which the layer under the polishing target film starts to be exposed is defined as an exposure start point C.
The torque waveform has a different shape according to the structural difference and manufacturing variation of the substrate to be polished. Fig. 20 and 21 are other diagrams showing torque waveforms when a substrate having a step with a concave-convex surface is polished. Specifically, fig. 20 shows waveforms of driving currents of the stage motor 6 when polishing a substrate having a larger ratio of convex portions of the uneven steps than the substrate of fig. 6, and fig. 21 shows waveforms of driving currents of the stage motor 6 when polishing a substrate having a deeper depth of the uneven steps than the substrate of fig. 6.
For example, when the torque waveform has a shape as shown in fig. 20, it is difficult to detect the level difference elimination point only from the change in the differential value. Therefore, in one embodiment, the operation control unit 9 may determine whether or not the film thickness of the reference substrate reaches the step-difference-eliminating film thickness based on a combination of the film thickness profile measured by the film thickness measuring device 80 and the differential value. The following shows an example of determining whether the level difference eliminating film thickness is reached or not based on a combination of the film thickness profile and the differential value. Further, it is determined based on a film thickness profile shown below that the film thickness of the reference substrate has reached the step-difference-eliminating film thickness, for example, when the film thickness of the convex portion has reached the convex portion threshold value, when the film thickness of the concave portion has reached the concave portion threshold value, when the difference between the convex portion and the concave portion has reached the concave-convex difference threshold value, when the fluctuation of the film thicknesses at the plurality of measurement points is equal to or greater than (or equal to) the fluctuation threshold value, or the like.
When the differential value of the torque waveform is smaller than the differential threshold value and the film thickness of the reference substrate is determined to reach the step-difference-eliminating film thickness based on the film thickness profile measured immediately before the moment when the differential value of the torque waveform is smaller than the differential threshold value
When the differential value of the torque waveform is smaller than the differential threshold value and the film thickness of the reference substrate is determined to reach the step-difference-eliminating film thickness based on the film thickness profile measured immediately after the time when the differential value of the torque waveform is smaller than the differential threshold value
The differential value of the torque waveform is smaller than the differential threshold value, and the film thickness of the reference substrate is determined to reach the step-difference eliminating film thickness based on the film thickness profile measured immediately before the time when the differential value of the torque waveform is smaller than the differential threshold value, and the film thickness of the reference substrate is determined to reach the step-difference eliminating film thickness based on the film thickness profile measured immediately after the time when the differential value of the torque waveform is smaller than the differential threshold value
In one embodiment, the correction value of the level difference elimination point may be calculated from the measurement result of the film thickness measuring device 80. For example, although the differential value of the torque waveform is smaller than the differential threshold value, when it is not determined from the film thickness profile after the differential value that the film thickness of the reference substrate reaches the step eliminating film thickness, or the like, the difference between the polishing time at the measurement time of the film thickness profile when the film thickness of the reference substrate is determined to reach the step eliminating film thickness and the polishing time when the threshold value of the torque waveform is smaller than the differential threshold value may be calculated, and when the reference substrate is polished next and later, the polishing time when the threshold value of the torque waveform is smaller than the differential threshold value plus the difference is determined as the step eliminating point.
In one embodiment, the operation control unit 9 generates a reference film waveform from the reference film data (reference spectrum or reference eddy current value) in the polishing step of the reference substrate. The reference film waveform is represented as a graph showing a relationship between a physical quantity indirectly showing the film thickness of the reference substrate included in the reference film data and the polishing time. The operation control unit 9 generates a reference film waveform by labeling a physical quantity indirectly indicating the film thickness of the reference substrate on a coordinate system having a vertical axis indicating the physical quantity and a horizontal axis indicating the polishing time.
For example, the reference spectrum tends to have a decreasing peak and trough count as polishing proceeds, but a decreasing rate tends to be gentle as the step elimination point is approached. In one embodiment, the physical quantity indirectly indicating the film thickness of the reference substrate is the number of peaks and valleys of the reference substrate. In one embodiment, the physical quantity is a reference eddy current value.
One embodiment may also determine whether the film thickness of the reference substrate reaches the step-difference-eliminating film thickness based on the change in the reference film waveform. In this case, steps 1-4 and 1-5 may not be executed, or when the operation control unit 9 determines that the film thickness profile of the reference substrate is not measured in step 1-4, steps 1-6 may be executed (that is, it is determined whether or not the film thickness of the reference substrate reaches the step-difference-eliminating film thickness based on the change in the reference film waveform).
Specifically, the operation control unit 9 calculates a differential value of the reference film waveform, compares the differential value of the reference film waveform with a predetermined reference film threshold, and determines that the film thickness of the reference substrate reaches the step-difference-eliminating film thickness when the differential value of the reference film waveform is equal to or lower than (or equal to) the reference film threshold. The differential value of the reference film waveform is obtained by calculating the change rate of the physical quantity (that is, the change rate of the physical quantity) indirectly indicating the film thickness of the reference substrate included in the reference film data with respect to the polishing time.
In one embodiment, it may be determined whether or not the film thickness of the reference substrate has reached the step-difference-eliminating film thickness based on a combination of the film thickness profile measured by the film thickness measuring device 80 and the differential value of the reference film waveform. Details of the determination method based on the combination of the film thickness profile and the differential value of the reference film waveform, which is not described in detail, are the same as the determination method described above based on the combination of the film thickness profile and the differential value of the torque waveform, as to whether or not the film thickness of the reference substrate reaches the step-difference-eliminating film thickness. The determination method based on the combination of the film thickness profile and the differential value of the torque waveform can be applied to the determination method based on the combination of the film thickness profile and the differential value of the reference film waveform by rewriting the differential value of the torque waveform to the differential value of the reference film waveform and rewriting the differential threshold to the reference film threshold.
In one embodiment, machine learning may be applied to the step-difference-eliminating film thickness determination step based on the torque waveform and/or the reference film waveform. That is, the operation control unit 9 may determine the step-difference-eliminating film thickness by using a learning completion model constructed by performing machine learning.
Machine learning is performed by a learning algorithm of an algorithm of artificial intelligence (AI: artificial Intelligence), and a learning completion model of predicting a step difference elimination film thickness by machine learning is constructed. The learning algorithm for constructing the learning completion model is not particularly limited. For example, the learning algorithm may be a known learning algorithm such as "learning with teacher", "learning without teacher", "reinforcement learning", "neural network-like", or the like. The neural network is, for example, deep learning. Deep learning is a machine learning method based on a neural network in which hidden layers (also referred to as intermediate layers) are multilayered.
In steps 1 to 7, the operation control unit 9 generates a first relational expression indicating a relation between the film thickness of the reference substrate and the polishing time of the reference substrate up to the step elimination point. The operation control unit 9 calculates the difference between the average value of the initial film thicknesses measured in step 1-1 and the average value of the film thicknesses (the step-difference-eliminating film thicknesses) at the plurality of measurement points at the time when it is determined that the step-difference-eliminating film thickness is reached. The operation control unit 9 further divides the difference by a polishing time from the initial film thickness to the step-elimination film thickness, thereby calculating a polishing rate to the step-elimination point. The operation control unit 9 generates a first relational expression based on the polishing rate. At this time, the polishing rate up to the level difference elimination point is set to be constant, and a first relational expression is generated. In other words, the film thickness of the reference substrate can be obtained by multiplying the polishing time by a coefficient that is the polishing rate.
In one embodiment, the operation control unit 9 may generate the first relational expression based on the film thickness profile measured at different polishing times. Specifically, the operation control unit 9 calculates an index value of the film thickness of the reference substrate at each polishing time based on the film thickness profile measured at each polishing time. The index value is calculated, for example, by calculating an average value of a plurality of film thicknesses of the reference substrate at each polishing time. The operation control unit 9 marks the index value of each film thickness on a coordinate system having a vertical axis indicating the film thickness and a horizontal axis indicating the polishing time. The operation control unit 9 determines a regression expression by performing regression analysis on the plurality of index values. The regression expression may be expressed using, for example, a quadratic function. The operation control unit 9 generates a first relational expression based on the regression expression. The first relational expression is stored in the memory device 9a of the operation control unit 9.
In steps 1 to 8, the operation control unit 9 allocates film thicknesses to the plurality of reference film data based on the first relational expression. That is, the operation control unit 9 calculates film thicknesses corresponding to the plurality of reference film data based on the first relational expression. Specifically, the operation control unit 9 calculates the film thickness corresponding to each reference film data by applying the polishing time for which each reference film data is obtained to the first relational expression.
In steps 2-1 to 2-5 (see fig. 12), a polishing step is performed after the step is eliminated on the reference substrate. In step 2-1, the polishing apparatus starts polishing the reference substrate after the step is eliminated by the above method. In step 2-2, a plurality of reference film data at a plurality of measurement points on the reference substrate are obtained by polishing the reference substrate in the same manner as in step 1-3. The plurality of reference film data are stored in the memory device 9a of the operation control unit 9.
In step 2-3, the operation control unit 9 compares the current polishing time (from step 2-1 to the current polishing time) with a predetermined end polishing time. The operation control unit 9 determines that polishing of the reference substrate is completed when the current polishing time reaches the completion polishing time, and executes steps 2 to 4 described later. When the operation control unit 9 determines that the current polishing time has not reached the final polishing time, it executes the steps 2-2 and beyond again.
The end polishing time is a polishing time to reach the final film thickness, and is determined based on the step-removed film thickness, the final film thickness, and the polishing rate after the step removal. In one embodiment, the polishing rate of the reference substrate after the step is eliminated may be regarded as constant. In this case, since the polishing rate of the reference substrate after the step removal is the same as that of the reference substrate having no uneven step on the surface to be polished, the polishing rate of the reference substrate after the step removal can be found experimentally and stored in the storage device 9a in advance.
In step 2-4, the operation control unit 9 generates a second relational expression indicating a relation between the film thickness of the reference substrate after the step-difference eliminating point and the polishing time of the reference substrate. The operation control unit 9 generates a second relational expression based on the polishing rate after the step is removed, the step removal film thickness, and the final film thickness, which are obtained in advance. The second relational expression is stored in the memory device 9a of the operation control unit 9.
In step 2-5, the operation control unit 9 allocates the film thickness to the plurality of reference film data based on the second relational expression. That is, the operation control unit 9 calculates the film thicknesses corresponding to the plurality of reference film data based on the second relational expression. Specifically, the operation control unit 9 calculates the film thickness corresponding to each reference film data by applying the polishing time stamp from which each reference film data was obtained to the second relational expression.
The polishing rate from the step-out film thickness to the final film thickness is sometimes not constant. Therefore, polishing of the reference substrate may be temporarily stopped at each predetermined time between step 2-1 and step 2-4, and the film thickness profile of the reference substrate may be measured by the film thickness measuring device 80. Thus, a plurality of film thickness profiles were measured at different polishing times. In one embodiment, the operation control unit 9 may generate the second relational expression based on the film thickness profile measured at different polishing times. Specifically, the operation control unit 9 calculates the film thickness index value of the reference substrate at each polishing time based on the film thickness profile measured at each polishing time. The index value is calculated, for example, by calculating an average value of a plurality of film thicknesses of the reference substrate at each polishing time. The operation control unit 9 marks the index value of each film thickness on a coordinate system having a vertical axis indicating the film thickness and a horizontal axis indicating the polishing time. The operation control unit 9 determines a regression expression by performing regression analysis on the plurality of index values. The regression expression may be expressed using, for example, a quadratic function. The operation control unit 9 may generate the second relational expression based on the regression expression.
In one embodiment, the final film thickness of the reference substrate may be determined based on the film thickness profile measured by the film thickness measuring device 80. Specifically, the operation control unit 9 may compare the film thickness of the reference substrate (for example, an average value of a plurality of film thicknesses at a plurality of measurement points on the reference substrate) measured by the film thickness measuring device 80 with a predetermined target film thickness, and determine that the film thickness of the reference substrate has reached the final film thickness when the film thickness of the reference substrate has reached the target film thickness.
After the polishing step of the reference substrate, a polishing step of the substrate W as the target substrate is performed. Hereinafter, an embodiment of a polishing method for the substrate W in a state where data of a sufficient torque waveform is not stored will be described with reference to fig. 13 to 18. In steps 3-1 to 3-19 (refer to fig. 13 to 15), polishing is stopped at each constant time, and the film thickness of the reference substrate is measured by the film thickness measuring device 80. Step-difference polishing steps are performed in steps 3-1 to 3-19. The step polishing step is a step of polishing the substrate W before the film thickness of the substrate W reaches the step eliminating film thickness, and includes a step of determining a plurality of film thicknesses at a plurality of measurement points on the substrate W based on the film thickness of the reference film data calculated by the first relational expression. In the present embodiment, in the polishing step, a torque waveform is generated based on the measured value of the torque, and data of the torque waveform and/or a target film waveform described later is stored in the storage device 9a.
In step 3-1, the initial film thickness (film thickness before polishing) of the substrate W is measured by the film thickness measuring device 80. The film thickness measuring device 80 measures a plurality of film thicknesses (film thickness profile) at a plurality of measurement points on the substrate W before polishing. In step 3-2, the polishing apparatus starts polishing the substrate W by the above-described method. That is, the platen motor 6 rotates the polishing platen 3 and the polishing pad 2 integrally at a constant rotational speed, and the polishing head 10 rotates the substrate W at a constant rotational speed. The polishing head 10 further presses the substrate W against the polishing surface 2a of the polishing pad 2, and starts polishing the substrate W. In one embodiment, the polishing head 10 may be swung along the polishing surface 2a by the swing motor 18 in a predetermined angle range to polish the substrate W.
In step 3-3, a plurality of pieces of film measurement data (measurement spectrum or measurement eddy current value) at a plurality of measurement points on the substrate W are obtained while polishing the substrate W, and the plurality of pieces of film measurement data are compared with a plurality of pieces of reference film data, and the reference film data corresponding to each piece of film measurement data (that is, the reference spectrum having the shape closest to the measurement spectrum (reference spectrum having the smallest error from the measurement spectrum) or the reference eddy current value closest to the measurement eddy current value (reference eddy current value having the smallest error from the measurement eddy current value)) is determined (selected) based on the plurality of pieces of reference film data (reference spectrum or reference eddy current value).
In step 3-4, the operation control unit 9 determines the film thickness at each measurement point. That is, the operation control unit 9 sets the film thickness of the reference film data determined in step 3-3 and the film thickness of the reference film data calculated based on the first relational expression (film thickness corresponding to the reference film data) for the film thickness of each measurement point. That is, the operation control unit 9 determines the film thickness of the reference film data determined in step 3-3 and the film thickness of the reference film data calculated based on the first relational expression as the film thickness of the measurement point at which the film measurement data corresponding to the reference film data is obtained.
In steps 3-5 and 3-6, the operation control unit 9 instructs the pressure regulators R1 to R4 to adjust the polishing profile of the substrate W based on the film thicknesses at a plurality of measurement points on the substrate W. The specific procedure is as follows.
In steps 3 to 5, the operation control unit 9 calculates the average film thickness of each of the plurality of regions (in this embodiment, four regions, that is, the center portion, the inner middle portion, the outer middle portion, and the edge portion) of the substrate W, and the average film thickness of the entire substrate W. The average film thickness of each region is an average value of film thicknesses at a plurality of measurement points in each region, and the average film thickness of the entire substrate W is an average value of film thicknesses at the measurement points over the entire substrate W.
In steps 3 to 6, the operation control unit 9 instructs the pressure regulators R1 to R4 to independently adjust the pressing force of the substrate W against the polishing pad 2 in each of the corresponding regions of the substrate W so that the difference between the average film thickness of the entire substrate W and the average film thickness of each of the plurality of regions is reduced. For example, when the operation control unit 9 compares the average film thickness of each region with the average film thickness of the entire substrate W, and the film thickness of a certain region is larger than the average film thickness of the entire substrate W, the operation control unit 9 instructs the pressure regulator (for example, the pressure regulator R1 in the central portion) corresponding to the region to increase the internal pressure of the corresponding pressure chamber (for example, the pressure chamber 46).
In step 3-7, feature points of the torque waveform and/or the target film waveform are detected. The feature point is, for example, a point at which the slope of the waveform changes beyond a threshold value, and is a point B in fig. 19 to 21. In the polishing step of the substrate W, the operation control unit 9 generates a target film waveform from the film measurement data (measured spectrum or measured eddy current value). The target film waveform is represented as a graph showing a relationship between a physical quantity indirectly showing the film thickness of the substrate W included in the film measurement data and the polishing time. The operation control unit 9 generates a target film waveform by labeling a physical quantity indirectly indicating the film thickness of the substrate W on a coordinate system having a vertical axis indicating the physical quantity and a horizontal axis indicating the polishing time. For example, the measured spectrum tends to decrease in the number of peaks and valleys as polishing proceeds, but the decrease rate tends to be gentle as the step elimination point is approached. In one embodiment, the physical quantity indirectly indicating the film thickness of the substrate W is the number of peaks and valleys of the measured spectrum. The physical quantity of one embodiment is a reference eddy current value.
In step 3-8, polishing of the substrate W is temporarily stopped, and a film thickness profile of the substrate W is measured by the film thickness measuring device 80. The film thickness profile of the substrate W is measured a plurality of times at different polishing times before the film thickness of the substrate W reaches the step-elimination film thickness.
In step 3-9, the correlation between the film thickness profile of the substrate W and the torque waveform and/or the target film waveform is checked, and it is determined whether the film thickness of the substrate W has reached the step-difference eliminating film thickness. When the operation control unit 9 determines that the film thickness of the substrate W reaches the step eliminating film thickness, the step polishing process is ended (steps 3 to 10).
When the operation control unit 9 determines that the film thickness of the substrate W has not reached the step-difference-eliminating film thickness, the operation control unit 9 determines whether or not the film thickness profile (residual film profile) of the substrate W satisfies a predetermined criterion (specification) (steps 3 to 11).
And (3) continuing to polish the substrate W under the current polishing conditions when the residual film topography is judged to meet the specification in the steps 3-12. The same steps as those of steps 3-3 to 3-7 are performed in step 3-12.
In steps 3 to 13, polishing of the substrate W is temporarily stopped, and a film thickness profile of the substrate W is measured by the film thickness measuring device 80. In steps 3 to 14, it is determined whether or not the film thickness of the substrate W has reached the step-difference eliminating film thickness by the same method as in steps 3 to 9. When the operation control unit 9 determines that the film thickness of the substrate W has reached the step-difference-eliminating film thickness, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and the step-difference polishing process is terminated (steps 3 to 15).
In steps 3 to 11, when the operation control unit 9 determines that the residual film topography does not satisfy the specification, the polishing conditions are changed so as to improve the residual film topography (so as to satisfy the above-described reference), and the substrate W is polished (steps 3 to 16). The polishing conditions include, for example, the internal pressure of each pressure chamber. For example, the operation control unit 9 instructs at least one of the pressure regulators R1 to R4 to increase (or decrease) the internal pressure of the corresponding pressure chamber in order to improve the waveform profile.
In steps 3 to 17, polishing of the substrate W is temporarily stopped, and a film thickness profile of the substrate W is measured by the film thickness measuring device 80. In steps 3 to 18, it is determined whether or not the film thickness of the substrate W has reached the step-difference eliminating film thickness by the same method as in steps 3 to 9. When the operation control unit 9 determines that the film thickness of the substrate W has reached the step-difference-eliminating film thickness, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and the step-difference polishing process is terminated (steps 3 to 19). When the operation control unit 9 determines that the film thickness of the substrate W has not reached the step-difference eliminating film thickness in steps 3 to 18, it returns to steps 3 to 11. In one embodiment, after the polishing conditions are changed once, a step of determining whether or not the residual film topography satisfies the specification may be omitted (steps 3 to 11). That is, in steps 3 to 18, when the operation control unit 9 determines that the film thickness of the substrate W has not reached the step-difference eliminating film thickness, the process returns to steps 3 to 12.
After the step-difference polishing process is completed, the flat polishing process of steps 4-1 to 4-17 is performed (see fig. 16 to 18). The flat polishing step includes a step of determining a plurality of film thicknesses at a plurality of measurement points on the substrate W based on the film thicknesses of the reference film data calculated by the second relational expression. The steps of steps 4-1 to 4-17, which are not specifically described, are the same as those of steps 3-3 to 3-19.
In step 4-2, the operation control unit 9 uses the film thickness of the reference film data determined in step 4-1 and the film thickness of the reference film data calculated based on the second relational expression (film thickness corresponding to the reference film data) as the film thickness of each measurement point. That is, the operation control unit 9 determines the film thickness of the reference film data determined in step 4-1 and the film thickness of the reference film data calculated based on the second relational expression as the film thickness of the measurement point at which the film measurement data corresponding to the reference film data is obtained. The more specific procedure of step 4-2 is the same as that of step 3-4, except that the film thickness corresponding to the reference film data is determined based on the second relational expression.
In step 4-7, the operation control unit 9 compares the film thickness of the substrate W with a predetermined final film thickness (target film thickness). When the film thickness of the substrate W reaches the final film thickness, the polishing end point is determined at the time when the film thickness reaches the final film thickness, and polishing of the substrate W is completed (steps 4 to 8). Specifically, the operation control unit 9 compares the average film thickness of the entire substrate W with a predetermined final film thickness. When the average film thickness of the entire substrate W reaches the final film thickness, polishing of the substrate W is completed.
When the polishing rate of the substrate W in the flat polishing step is regarded as constant, in step 4-7, the operation control unit 9 may compare the current polishing time (from step 4-1 to the current polishing time) with a predetermined end polishing time, and may end polishing of the substrate W when it is determined that the current polishing time has reached the end polishing time. The end polishing time is a polishing time to reach the final film thickness, and is determined based on the step-removed film thickness, the final film thickness, and the polishing rate after the step removal. The steps 4-12 and 4-16 are also performed in the same manner as in the step 4-7, that is, the step of comparing the film thickness of the substrate W with a predetermined final film thickness. In steps 4 to 13 and 4 to 17, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and polishing of the substrate W is completed.
After the completion of the planarization step, during the step polishing step, or during the planarization step, the operation control unit 9 correlates the measured film thickness profile of the substrate W with the torque waveform and/or the target film waveform. In one embodiment, the operation control unit 9 may determine the level difference elimination point B based on the measured film thickness profile of the substrate W. That is, the operation control unit 9 may determine the step eliminating point B of the torque waveform based on the polishing time when the film thickness of the substrate W reaches the step eliminating film thickness.
The operation control unit 9 stores the torque waveform and/or the target film waveform in the storage device 9a in association with the initial film thickness data of the substrate W measured by the film thickness measuring device 80, the film thickness profile of the substrate W before polishing, the film thickness profile of the substrate W during polishing, the step-difference eliminating film thickness, and the like.
The polishing apparatus may polish a plurality of substrates of the same type and having varying initial film thickness and a plurality of substrates having different shapes of the uneven structure by the same method as in steps 3-1 to 3-19 and steps 4-1 to 4-17 while generating the torque waveform, and determine the step elimination point of each torque waveform based on the film thickness profile measured in the polishing step of each substrate. The operation control unit 9 may correlate each torque waveform and/or target film waveform generated during polishing of each substrate with film thickness data of the substrate to be polished. Examples of the film thickness data include the type of the substrate to be polished, initial film thickness data of the substrate to be polished, a film thickness profile of the substrate before polishing, a film thickness profile of the substrate during polishing, and step-difference-elimination film thickness data. Therefore, data of a plurality of torque waveforms (a drive current waveform of the table motor 6, a drive current waveform of the polishing head motor 17, or a drive current waveform of the swing motor 18) and/or a target film waveform associated with these film thickness data are stored in the storage device 9a.
In one embodiment, in the reference substrate polishing step (steps 1-1 to 1-8 and steps 2-1 to 2-5), the step-difference elimination point of the torque waveform may be determined based on the film thickness profile measured in the reference substrate polishing step. The operation control unit 9 correlates the torque waveform and/or the reference film waveform generated during polishing of the reference substrate with the film thickness data of the reference substrate. Data of a torque waveform (a driving current waveform of the table motor 6, a driving current waveform of the polishing head motor 17, or a driving current waveform of the swing motor 18) and/or data of a reference film waveform associated with the film thickness data are stored in the storage device 9a.
Fig. 22 to 27 are flowcharts showing an embodiment of a method for polishing a substrate having a surface with a step of roughness after a sufficient torque waveform is stored. In this embodiment, the substrate is polished while estimating the level difference elimination point based on the torque waveform. For example, the substrate W to be polished is as shown in fig. 6, but the substrate W to be polished is not limited to the substrate shown in fig. 6. In the present embodiment, the polishing apparatus polishes the reference substrate and the target substrate W while measuring the torque for rotating the polishing table 3 (the driving current of the table motor 6), the torque for rotating the polishing head 10 about the axis thereof (the driving current of the polishing head motor 17), or the torque for swinging the polishing head 10 along the polishing surface 2a (the driving current of the swing motor 18), and the operation control unit 9 generates a torque waveform based on the measured value of the torque in the polishing step. Hereinafter, the torque waveform acquired before polishing in the present embodiment and stored in the storage device 9a is referred to as a reference torque waveform. In one embodiment, the operation control unit 9 may generate the target film waveform in the polishing step of the substrate W. The reference film waveform and the target film waveform obtained before polishing in the present embodiment and stored in the storage device 9a are hereinafter referred to as storage film waveforms.
Step polishing steps 5-1 to 5-21 (see fig. 22 to 24) are performed. The steps of steps 5-1 to 5-6, which are not specifically described, are the same as those of steps 3-1 to 3-6.
In step 5-1, the initial film thickness of the substrate W to be polished (film thickness profile of the substrate W before polishing) is measured by the film thickness measuring device 80. The operation control unit 9 selects one reference torque waveform (or one stored film waveform) from a plurality of reference torque waveforms (or a plurality of stored film waveforms) based on measurement data (film thickness profile of the substrate W before polishing) of the film thickness measuring device 80 and the type of the substrate W. Specifically, the operation control unit 9 compares the measurement data of the film thickness measuring device 80 with the type of the substrate W, and the film thickness data and the type of the substrate associated with each reference torque waveform (or each storage film waveform). The operation control unit 9 selects, as the reference torque waveform, a reference torque waveform having the same substrate type and having measurement data of the film thickness measuring device 80 closest to the film thickness data (specifically, a film thickness profile before substrate polishing used for generating the reference torque waveform or the memory film waveform). In one embodiment, the operation control unit 9 may select, as the reference film waveform, a stored film waveform having the same substrate type and having measurement data of the film thickness measuring device 80 closest to the film thickness data (specifically, a film thickness profile before polishing of the substrate used for generating the stored film waveform). Hereinafter, in this specification, the torque waveform selected in step 5-1 will be referred to as a reference torque waveform, and the selected storage film waveform will be referred to as a reference film waveform.
In step 5-4, the operation control unit 9 determines the film thickness at each measurement point. That is, the operation control unit 9 sets the film thickness of the reference film data determined in step 5-3 and the film thickness of the reference film data calculated based on the first relational expression (film thickness corresponding to the reference film data) for the film thickness of each measurement point. That is, the operation control unit 9 determines the film thickness of the reference film data determined in step 5-3 and the film thickness of the reference film data calculated based on the first relational expression as the film thickness at the measurement point at which the film measurement data corresponding to the reference film data is obtained.
In step 5-7, feature points of the torque waveform and/or the target film waveform are detected. In step 5-8, it is confirmed whether the torque waveform and/or the target film waveform is abnormal. In one embodiment, in the steps 5 to 12, 5 to 17, and 5 to 21 described later, it is possible to determine whether or not the torque waveform and/or the target film waveform is abnormal by comparing the correlation between the stored film thickness profile and the torque waveform and/or the target film waveform. When the operation control unit 9 determines that the waveform is not abnormal, it ends the step polishing step (steps 5 to 9). When the operation control unit 9 determines that the waveform is abnormal, it executes steps 5 to 10 and subsequent steps.
In steps 5 to 10, polishing of the substrate W is temporarily stopped, and a film thickness profile of the substrate W is measured by the film thickness measuring device 80. In one embodiment, steps 5-11 may be performed after step 5-6 instead of steps 5-7 to 5-10. In one embodiment, steps 5-11 may also be performed after steps 5-7.
In steps 5 to 11, the operation control unit 9 determines whether or not the film thickness of the substrate W has reached the step eliminating film thickness, that is, whether or not the step polishing process should be completed. Specifically, the operation control unit 9 compares the torque waveform (or target film waveform) generated during polishing with the reference torque waveform (or reference film waveform) to determine whether or not the film thickness of the substrate W has reached the step-elimination film thickness, that is, whether or not the step polishing process should be terminated. When the operation control unit 9 determines that the step polishing process should be completed, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and the step polishing process is completed (steps 5 to 12). In one embodiment, when there is an abnormality in the torque waveform or the target film waveform, the profile of the waveform may be adjusted after the step polishing step is completed.
The details of steps 5-11 are as follows. Specifically, the operation control unit 9 determines that the step polishing process should be ended when the current torque (or the current physical quantity, that is, the physical quantity indirectly indicating the film thickness of the substrate W included in the film measurement data) of the generated torque waveform (or the target film waveform) reaches the step elimination point estimated from the reference torque waveform (or the reference film waveform).
In one embodiment, the step polishing process may be ended even when the current torque (or the current physical quantity) has not reached the step removal point. For example, the operation control unit 9 may determine that the step polishing process should be ended when the current torque (or the current physical quantity) is equal to or smaller than a predetermined ratio (for example, 130% or smaller) of the reference level of the reference torque waveform (or the reference film waveform) and/or when the current polishing time is equal to or longer than 90% of the polishing time at the step elimination point estimated from the reference torque waveform (or the reference film waveform). The reference level is a threshold value of the magnitude of the predetermined torque (or physical quantity).
In one embodiment, the operation control unit 9 may determine that the step polishing process should be ended when the current torque (or the current physical quantity) is equal to or less than a predetermined ratio of the reference level of the variation amount of the reference torque waveform differential value (or the reference film waveform differential value), and/or when the current polishing time is equal to or more than 90% of the polishing time at the step elimination point, which is estimated from the variation amount of the reference torque waveform differential value (or the reference film waveform differential value). The reference level is a threshold value of the variation amount of the predetermined torque waveform differential value (differential value of the physical quantity).
In one embodiment, the operation control unit 9 may compare the shape of the generated torque waveform (or target film waveform) with the shape of the reference torque waveform (or reference film waveform) corresponding to the polishing time of the current polishing time after the lapse of the predetermined time, and calculate the degree of coincidence between these shapes. The operation control unit 9 may compare the calculated degree of matching with a predetermined reference degree of matching, calculate a difference between the polishing time of the step elimination point estimated from the reference torque waveform (or the reference film waveform) and the current polishing time when the calculated degree of matching is equal to or higher than the predetermined reference degree of matching, and determine that the step polishing process should be ended when the polishing time of the substrate W reaches a time obtained by adding the difference to the current polishing time or adding a value obtained by multiplying the difference by a coefficient. The degree of coincidence is expressed by a numerical value of 0 to 1, and the degree of coincidence is higher as the degree of coincidence approaches 1. The reference degree of coincidence is, for example, 0.8.
In one embodiment, the operation control unit 9 may determine that polishing abnormality has occurred and temporarily stop polishing the substrate W when the degree of uniformity of the calculated shape is equal to or less than the reference degree of uniformity after a predetermined time has elapsed. Then, the substrate W may be conveyed to the film thickness measuring device 80, and the film thickness profile of the substrate W may be measured by the film thickness measuring device 80.
In one embodiment, the operation control unit 9 may instruct the polishing device to change the polishing conditions when the degree of uniformity of the shape is equal to or less than the reference degree of uniformity after a predetermined time has elapsed. For example, the operation control unit 9 may issue a command to at least one of the pressure regulators R1 to R4 to increase (or decrease) the internal pressure of the corresponding pressure chamber. As a result of changing the polishing conditions, when the degree of uniformity of the shape is equal to or greater than the reference degree of uniformity, a difference between the polishing time at the step elimination point estimated from the reference torque waveform (or the reference film waveform) and the current polishing time may be calculated, and when the polishing time of the substrate W reaches a time obtained by adding the difference to the current polishing time or adding the difference to the value obtained by multiplying the difference by a coefficient, the step polishing step may be ended. In one embodiment, it is also possible to determine whether the step polishing process should be ended by the method described in steps 3 to 9, that is, the same method as in steps 1 to 6.
When the operation control unit 9 determines in steps 5 to 11 that the film thickness of the substrate W has not reached the step-difference-eliminating film thickness, the operation control unit 9 determines whether or not the film thickness profile (residual film profile) of the substrate W satisfies a predetermined criterion (specification) (steps 5 to 13).
And (5) continuing to polish the substrate W under the current polishing conditions when the residual film topography is judged to meet the specification in the steps 5-14. The same steps as those of steps 5-3 to 5-7 are performed in step 5-14.
In steps 5 to 15, polishing of the substrate W is temporarily stopped, and a film thickness profile of the substrate W is measured by the film thickness measuring device 80. In steps 5 to 16, it is determined whether or not the film thickness of the substrate W has reached the step-difference eliminating film thickness in the same manner as in steps 5 to 11. When the operation control unit 9 determines that the film thickness of the substrate W has reached the step-difference-eliminating film thickness, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and the step-difference polishing process is terminated (steps 5 to 17).
When the operation control unit 9 determines that the residual film topography does not meet the specification in steps 5 to 13, the polishing conditions are changed so as to improve the residual film topography (so as to meet the above-described standard), and the substrate W is polished (steps 5 to 18). The polishing conditions include, for example, the internal pressure of each pressure chamber. For example, the operation control unit 9 instructs at least one of the pressure regulators R1 to R4 to increase (or decrease) the internal pressure of the corresponding pressure chamber in order to improve the waveform profile.
In steps 5 to 19, polishing of the substrate W is temporarily stopped, and a film thickness profile of the substrate W is measured by the film thickness measuring device 80. In steps 5 to 20, it is determined whether or not the film thickness of the substrate W has reached the step-difference eliminating film thickness by the same method as in steps 5 to 11. When the operation control unit 9 determines that the film thickness of the substrate W has reached the step-difference-eliminating film thickness, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and the step-difference polishing process is terminated (steps 5 to 21). When the operation control unit 9 determines that the film thickness of the substrate W has not reached the step-difference eliminating film thickness in steps 5 to 20, the process returns to steps 5 to 13. In one embodiment, after the polishing conditions are changed once, the step of determining whether the residual film topography satisfies the specification may be omitted (steps 5 to 13). That is, when the operation control unit 9 determines in steps 5 to 20 that the film thickness of the substrate W has not reached the step-difference eliminating film thickness, steps 5 to 14 and subsequent steps may be executed.
In one embodiment, steps 5-16, 5-20 may be performed after steps 5-14, 5-18 without performing steps 5-15 and 5-19. In one embodiment, when step 5-10 is not performed and when the operation control unit 9 determines in step 5-11 that the film thickness of the substrate W has not reached the step-elimination film thickness, steps 5-14 to 5-17 may be performed after step 5-11. In this case, steps 5 to 15 may be omitted.
After the step polishing process is completed, the flat polishing process of steps 6-1 to 6-19 (see fig. 25 to 27) is performed. The steps of steps 6-1 to 6-19, which are not specifically described, are the same as those of steps 5-3 to 5-21. The flat polishing step includes a step of determining a plurality of film thicknesses at a plurality of measurement points on the substrate W based on the film thicknesses of the reference film data calculated by the second relational expression.
In step 6-2, the operation control unit 9 uses the film thickness of the reference film data determined in step 6-1 and the film thickness of the reference film data calculated based on the second relational expression as the film thickness of each measurement point. That is, the operation control unit 9 determines the film thickness of the reference film data determined in step 6-1 and the film thickness of the reference film data calculated based on the second relational expression as the film thickness of the measurement point at which the film measurement data corresponding to the reference film data is obtained. The more specific procedure of step 6-2 is the same as that of step 5-4, except that the film thickness corresponding to the reference film data is determined based on the second relational expression.
In steps 6-9, 6-14, and 6-18, the operation control unit 9 compares the film thickness of the substrate W with a predetermined final film thickness (target film thickness). When the film thickness of the substrate W reaches the final film thickness, the polishing end point is determined at the time when the film thickness reaches the final film thickness, and polishing of the substrate W is completed. Specifically, the operation control unit 9 compares the average film thickness of the entire substrate W with a predetermined final film thickness. When the average film thickness of the entire substrate W reaches the final film thickness, polishing of the substrate W is completed.
When the polishing rate of the substrate W in the flat polishing step is regarded as constant, the operation control unit 9 may determine that the polishing of the substrate W is completed when the current polishing time (from step 6-1 to the current polishing time) is equal to the predetermined completion polishing time in steps 6-9, 6-14, and 6-18. The end polishing time is a polishing time to reach the final film thickness, and is determined based on the step-removed film thickness, the final film thickness, and the polishing rate after the step removal. In steps 6 to 10, 6 to 15, and 6 to 19, the correlation between the film thickness profile and the torque waveform and/or the target film waveform is stored in the memory device 9a of the operation control unit 9, and polishing of the substrate W is completed.
In one embodiment, steps 6-5 to 6-8 may not be performed, and step 6-9 may be performed after step 6-4. Furthermore, in one embodiment, step 6-9 may also be performed after step 6-5. Furthermore, in one embodiment, steps 6-14, 6-18 may be performed after steps 6-12, 6-16 instead of steps 6-13 and 6-17.
As described above, the polishing apparatus according to the present embodiment changes the relational expression used when determining the film thickness of the substrate W during polishing, according to the surface shape of the substrate W. The polishing apparatus compares the torque waveform generated during polishing with the reference torque waveform obtained before polishing to determine the timing of changing the relational expression. Thus, even when the substrate has a step of roughness on the surface, the film thickness of the substrate during polishing can be accurately measured. As a result, uniformity of film thickness and end point detection performance can be improved.
In one embodiment, when the first relational expression and/or the second relational expression need to be corrected, the first relational expression and/or the second relational expression may be corrected based on the results obtained in the steps described with reference to fig. 22 to 27. In one embodiment, the first relational expression and/or the second relational expression may be regenerated by polishing the reference substrate in the same process as described with reference to fig. 11 and 12.
The polishing method described above may also be applied to the substrates of fig. 28 to 30. Fig. 28 to 30 are cross-sectional views showing other embodiments of the substrate W having the uneven surface. Fig. 28A, 29A, and 30A show the state of each substrate before polishing, fig. 28B, 29B, and 30B show the state of polishing the uppermost film (tungsten (W) film 109, insulating film 111, or tungsten (W) film 117) to the step-difference-eliminating film thickness, and fig. 28C, 29C, and 30C show the state of polishing each substrate to the polishing end point.
Fig. 28 shows a cross section of a replacement gate. The substrate W shown in fig. 28 includes: a silicon layer (Si) 100 having a concave-convex step; an insulating film 105 formed over the silicon layer 100; a liner film 107 composed of titanium nitride (TiN) formed on the insulating film 105; and a tungsten (W) film 109 formed on the liner film 107. Since the tungsten (W) film 109 is a metal film, an eddy current sensor is used as the film thickness sensor 20 when polishing the substrate W shown in fig. 28.
Fig. 29 shows a cross section of SAC (self aligned contact) nitride. The substrate W shown in fig. 29 is etched from the substrate W shown in fig. 28 to form a tungsten (W) film 109, and then an insulating film (e.g., silicon nitride (Si)3 N4 )) 111. When polishing the substrate W shown in fig. 29, an optical film thickness sensor is used as the film thickness sensor 20.
Fig. 30 shows a cross section of the contact portion. The substrate W shown in fig. 30 includes: a silicon (Si) layer 100; an insulating film 113 formed over the silicon layer 100; a liner film 115 composed of titanium nitride (TiN) formed on the insulating film 113; and a tungsten (W) film 117 formed on the liner film 115.
Fig. 31 is a schematic view showing another embodiment of the polishing apparatus. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the embodiment shown in fig. 1 to 27, and thus, a repetitive description thereof will be omitted. Fig. 31 is a diagram in which some constituent elements are omitted. The film thickness measuring device 80 of the present embodiment is mounted on the polishing table 3. The film thickness measuring device 80 of the present embodiment is smaller than the film thickness measuring device 80 described with reference to fig. 1.
The film thickness measuring device 80 of the present embodiment includes: a light projecting section 82 for radiating light on the substrate W; and a light receiving unit 85 for receiving reflected light reflected by the surface (polished surface) of the substrate W. The light projecting section 82 includes a light source (not shown) that emits light. The light projecting section 82 of the present embodiment is disposed so as to radiate light from obliquely below to the substrate W, and the light receiving section 85 is disposed obliquely with respect to the surface of the substrate W, but the arrangement of the light projecting section 82 and the light receiving section 85 is not limited to this arrangement. In one embodiment, the film thickness measuring device 80 may be an eddy current type film thickness measuring device including an eddy current sensor instead of the light projecting section 82 and the light receiving section 85.
In the example shown in fig. 31, a polarization ellipsometer is used as the film thickness measuring device 80. The principle of a polarized ellipsometer is generally known. In order to apply the present embodiment to the substrate W supported by the polishing head 10, it is necessary to measure the deflection state of the reflected light by removing the liquid from the measurement portion. Thus, the film thickness measuring device 80 further includes: in order to dry the measuring unit, CDA (clean dry air) and nitrogen (N)2 ) A gas supply nozzle 87 for supplying a gas such as argon (Ar) or air to the front surface of the substrate W; and a waste liquid path 89 for discharging a liquid for polishing such as a polishing liquid (e.g., slurry). Since the substrate W is supported by the polishing head 10, the rotation and the X/Y direction operations can be performed, and the film thickness distribution can be obtained by measuring any point on the substrate W a plurality of times while rotating the substrate W. In order to protect the surface state of the substrate W, the substrate W may be immersed in a liquid except for the measuring section.
The light projecting section 82, the light receiving section 85, the gas supply nozzle 87, and the waste liquid path 89 are mounted on the polishing table 3, and rotate integrally with the polishing table 3 and the polishing pad 2. In the present embodiment, the light projecting section 82 emits light to a plurality of measurement points on the rotating substrate W while the film thickness measuring device 80 passes through the substrate W once, and the light receiving section 85 receives reflected light from the plurality of measurement points. When the film thickness measuring device 80 is an eddy current type film thickness measuring device, the eddy current sensor generates eddy currents at a plurality of measuring points on the substrate W, and detects the eddy currents at the plurality of measuring points. In one embodiment, as shown in fig. 32, the film thickness measuring device 80 may be disposed at the center of the polishing table 3.
In the present embodiment, the film thickness and the film thickness profile of the substrate W can be measured by the film thickness measuring device 80 without taking out the substrate W from the polishing head 10. This reduces the time loss for detaching the substrate W (improves the throughput), prevents the position and slope deviation of the substrate W due to the relocation, and provides advantages such as reduced measurement coordinate error, easiness in reworking after measurement, improved correction accuracy of the output of the end point detection sensor (film thickness sensor 20), and reduction of particles adhering to the substrate W due to loading, unloading, and transportation.
In the present embodiment, the film thickness measuring device 80 may be combined with detection of a step elimination point by the drive currents of the table motor 6, the polishing head motor 17, and the swing motor 18, and end point detection by the film thickness sensor 20. When the film thickness sensor 20 is used, correction of the film thickness sensor 20 is required. Therefore, correction of the relationship between the substrate W after film thickness measurement and the output of the end point detection sensor is required. When the film thickness measuring device 80 is an ITM (ex-situ film thickness measuring device) provided away from the polishing unit 1, the substrate W is removed from the polishing head 10 at the time of the correction, and is conveyed to the ITM by the conveyance robots 66, 69 or the like. When the film thickness measuring device 80 is an ITM provided away from the polishing unit 1, an error factor is generated due to a measurement position error of the film thickness and the need for polishing plural times to measure the film thickness of the ITM and to obtain the output of the film thickness sensor 20 at plural points. Therefore, the correction can be performed with higher accuracy than in the past, and thus the end point detection accuracy can be improved.
Further, in the present embodiment, the region of the high-density wiring portion of the substrate W can be specified, and the film thickness distribution and the accuracy can be determined based on the film measurement (film thickness measurement) result. Since the substrate W does not need to be removed from the polishing head 10, the correlation between the coordinates of the substrate W and the film thickness is measured, and then the output signal of the film thickness sensor 20 can be compared with the coordinate position of the substrate W and the film thickness in a state where the error in the coordinate position is small. The use is particularly effective when a wafer having a complicated pattern structure is used. For example, the present embodiment can also be applied to film measurement using only waveforms of the effective region.
The present embodiment is also applicable to various processing pattern films such as oxide films, nitride films, metal films, mixed pattern films thereof, STI processing films, SAC processing films, and the like. In one embodiment, the film thickness measuring device 80 described with reference to fig. 31 and 32 may be a film thickness measuring device, a multispectral camera, or a hyperspectral camera using a processing system of a camera image. In one embodiment, a film thickness measuring device using an image processing or optical interference method may be used as the film thickness measuring device 80.
As shown in fig. 33, in one embodiment, a film thickness measuring device 80 may be provided near (near) the polishing table 3. When the film thickness measuring device 80 is disposed near the polishing table 3, it can be measured without immersing in a liquid. Alternatively, in order to prevent surface oxidation, a liquid film may be formed on the surface of the substrate W by spraying or atomizing the liquid from the gas supply nozzle 87, and the substrate may be kept dry only in the vicinity of the measurement portion. In order to use a smaller membrane measurement device, a measurement device or mechanism may be constituted by MEMS (micro-electromechanical system (Micro Electro Mechanical Systems)). The light projecting section 82 and the light receiving section 85 may be connected by direct coupling or optical fiber connection.
As an advantage of providing the film thickness measuring device 80 in the polishing table 3 or in the vicinity of the polishing table 3, for example, the film thickness can be measured in a state where the substrate W is provided in the polishing head 10, without removing the substrate W from the polishing head 10. Other advantages are as follows: the polishing head 10 can reduce time loss (increase throughput) due to detachment of the substrate W from the polishing head 10, reduce positional deviation and slope deviation of the substrate W due to the repositioning of the substrate W to the polishing head 10, reduce measurement coordinate errors, facilitate the reworking of the substrate W after measurement, improve correction accuracy of the end point detection sensor, and reduce particles adhering due to attachment, detachment, and conveyance.
Fig. 34 is a cross-sectional view showing still another embodiment of the film thickness measuring device 80. In this embodiment, the film thickness measuring device 80 supplies a liquid (e.g., pure water, chemical solution, slurry) to a film thickness measuring portion through the liquid supply nozzle 90, and measures an interference state of reflected light from the substrate W in a state where the film thickness measuring portion is immersed in the liquid. While the liquid is supplied through the liquid supply nozzle 90, the liquid is discharged through the waste liquid path 89, and the liquid is renewed and impurities are removed. Since the substrate W is disposed on the polishing head 10, the substrate W can move rotationally and translationally. For example, the film thickness distribution can be obtained by measuring the film thickness at any plurality of points on the substrate W while rotating the substrate W by the polishing head 10. In one embodiment, the film thickness measuring device 80 shown in fig. 34 may be provided near (near) the polishing table 3.
Fig. 35 is a diagram illustrating an embodiment of a method for polishing a substrate having a step with irregularities on a surface. In general, polishing conditions of the substrate need to be changed when the state of the exposed surface of the substrate is changed (for example, when the exposed film is removed and the underlying film is exposed, or when a step of the exposed surface is eliminated). The polishing conditions of the substrate include, for example, a force pressing the substrate against the polishing surface of the polishing pad. In the embodiments described below, a method of determining a change point of polishing conditions based on a step-out point and a film thickness measurement point before or after the step-out point is provided. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the embodiment described above, and thus, the repetitive description thereof will be omitted.
The polishing apparatus starts polishing a reference substrate (or reference wafer) having the same laminated structure as the substrate W (target wafer or target substrate). The polishing of the reference substrate is temporarily interrupted at least 2 times from the start of polishing to the polishing end point, and the film thickness of the reference substrate is measured by the film thickness measuring device 80. More specifically, the film thickness measuring device 80 measures film thicknesses (i.e., film thickness profile) of the reference substrate at a plurality of measurement points. After the film thickness is measured by the film thickness measuring device 80, polishing of the reference substrate is started again, and the reference substrate is polished until the polishing end point is reached finally. Therefore, the reference substrate is subjected to film thickness measurement (i.e., film thickness profile) by the film thickness measuring device 80 a plurality of times.
The operation control unit 9 generates a first torque waveform as shown in fig. 35. The first torque waveform represents a change in torque required in the polishing apparatus (e.g., the polishing table 3 and/or the polishing head 10) with respect to polishing time when polishing the reference substrate. The operation control unit 9 determines the step elimination point B from the characteristic point of the first torque waveform. The feature point is, for example, a point at which the slope of the first torque waveform changes beyond a threshold value. The first torque waveform is stored in the memory device 9a of the operation control unit 9.
Reference numerals D and E in fig. 35 denote film thickness measurement points at which film thicknesses of the reference substrate are measured at a plurality of measurement points by the film thickness measuring device 80. The film thickness measurement point D is a time after the surface step of the reference substrate is eliminated, and the film thickness measurement point E is a time before the surface step of the reference substrate is eliminated. It is known from the film thickness profile of the reference substrate whether the surface step is eliminated.
The operation control unit 9 determines a polishing condition change point F between one of the film thickness measurement point D and the film thickness measurement point E and the step elimination point B. One example is that the polishing condition changing point F is determined based on a predetermined time from the step eliminating point B or a change in the first torque waveform.
Next, the substrate W of the target substrate is polished by the polishing apparatus. The operation control unit 9 generates a second torque waveform during polishing of the substrate W. The second torque waveform indicates a change in torque required in the polishing apparatus (e.g., the polishing table 3 and/or the polishing head 10) with respect to polishing time when polishing the substrate W. Since the substrate W has the same laminated structure as the reference substrate, the first torque waveform is similar in shape to the second torque waveform. The operation control unit 9 determines a point at which a point on the second torque waveform coincides with the polishing condition changing point F while generating the second torque waveform, and changes the polishing condition of the substrate W at the determined point. In the present embodiment, an optimal change point of the polishing conditions can be determined from the level difference elimination point and the film thickness measurement point of the reference substrate.
The embodiment of determining the polishing condition change point F between the film thickness measurement point D and the step removal point B, that is, after the step removal point B is effective in reducing the variation in the step. In other words, it is effective to eliminate the level difference state and the level of the film thickness distribution at the film thickness measurement point D (to completely eliminate the level difference or the high film thickness uniformity).
The embodiment of determining the polishing condition change point F between the film thickness measurement point E and the step removal point B, that is, before the step removal point B is effective in removing abrupt step changes. Further, when the non-uniformity of the film thickness distribution increases in the film thickness measurement point D or degradation in the specification is observed, the operation control unit 9 determines the polishing condition change point F between the film thickness measurement point E and the step elimination point B, that is, before the step elimination point B.
In this way, by changing the overall waveform and gradually changing the polishing conditions before and after the changing point, the changing point of the polishing conditions can be determined, and efficient polishing with good uniformity of film distribution can be performed.
AI (artificial intelligence) can also be used for waveform prediction. The polishing condition change point can be obtained by predicting the waveform using a learning completion model learned by using the data set of the stored data.
Next, an embodiment of a polishing method for predicting the step removal of the substrate W using the learning completion model will be described with reference to fig. 36. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the above embodiment, and thus, a repetitive description thereof will be omitted.
The motion control unit 9 has a level difference elimination prediction model M1 stored in a storage device 9a thereof. The polishing apparatus polishes the substrate W by pressing the substrate W against the polishing surface 2a of the polishing pad 2 by the polishing head 10 while rotating the polishing table 3 supporting the polishing pad 2, and the operation control unit 9 generates a torque waveform (a driving current waveform of the table motor 6, a driving current waveform of the polishing head motor 17, or a driving current waveform of the swing motor 18) indicating a driving current of a motor required for relatively moving the substrate W with respect to the polishing surface 2a during polishing of the substrate W, inputs the torque waveform into the level difference elimination prediction model M1, and outputs a level difference elimination index on the surface of the substrate W from the level difference elimination prediction model M1.
The level difference elimination index is the level difference elimination degree (expressed in%, level, time to level difference elimination point, etc.) calculated from the current torque waveform by the level difference elimination prediction model M1. Therefore, the motion control section 9 can calculate the difference between the current surface level difference of the substrate W and the level difference elimination point based on the level difference elimination degree. The operation control unit 9 may change the polishing conditions of the substrate W when the step removal point is reached.
The level difference elimination prediction model M1 may be configured to further output at least one of a plurality of indices shown below.
Point of polishing condition of strained substrate W
Predicted torque waveform before and after step elimination point
Alarm indicating abnormality of torque waveform
The difference (time, waveform) between the torque waveform at the step-difference eliminating time and the current time
Dressing advice for polishing pad 2
The level difference elimination prediction model M1 may be configured to further output at least one of a plurality of indices of the virtual metrology shown below.
Predicted film thickness profile when eliminating step
Predicted film thickness profile before and after step elimination
Predicting film thickness profile changes at current time and step elimination
Predicting time for switching grinding conditions based on film thickness profile change before and after eliminating concave-convex
The level difference elimination prediction model M1 is a learning completion model constructed by machine learning such as deep learning, reinforcement learning, quantum computing, and the like. The learning completion model is also referred to as an adjusted model or an adjusted neural-like network. The training data used for machine learning includes a plurality of training torque waveforms obtained when at least one training substrate is polished to eliminate a surface step thereof. More specifically, the motion control unit 9 generates a plurality of training torque waveforms indicating driving currents of motors (the table motor 6, the polishing head motor 17, or the swing motor 18) necessary for relatively moving the training substrate with respect to the polishing surface 2a while polishing the training substrate to eliminate the step difference on the surface. The motion control unit 9 performs machine learning using a plurality of training torque waveforms and training data including a plurality of level difference elimination levels as positive solution labels, thereby constructing a level difference elimination prediction model M1.
The torque waveform inputted to the learning completion model and the training torque waveform used for machine learning may be processed torque waveforms. Examples of the processed torque waveform include a torque waveform obtained by applying a filter to the torque waveform and a torque waveform obtained by amplifying the torque waveform by an amplifier.
In one embodiment, the training data may further include the number of substrates polished using the polishing pad 2 in the past. The operation control unit 9 may be configured to input the number of substrates polished by the polishing pad 2 in the past into the step elimination prediction model M1 in addition to the torque waveform. The number of substrates polished by using the polishing pad 2 in the past is related to the abrasion of the polishing pad 2, and affects the polishing time to reach the step elimination point. Therefore, the present embodiment can output a more accurate level difference elimination index.
The input data to the step-elimination prediction model M1 may further include at least one of the data shown below, in addition to the torque waveform.
Output signal of film thickness sensor 20
Processed output signal of film thickness sensor 20
Number of substrates polished by the polishing pad 2 after finishing in the past
The training data may also further comprise at least one of the input data shown below.
The number of substrates polished by the polishing pad 2 and the polishing rate of each substrate in the past
Map of the number of substrates polished by the polishing pad 2 and the polishing rate of each substrate in the past
Number of substrates polished by the polishing pad 2 after finishing in the past
Next, another embodiment of a polishing method for predicting step elimination of the substrate W using the learning completion model will be described with reference to fig. 37. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the embodiment described above with reference to fig. 36, and thus, a repetitive description thereof will be omitted.
As shown in fig. 37, the motion control unit 9 includes a polishing end point prediction model M2 stored in the storage device 9a in addition to the step elimination prediction model M1. The operation control unit 9 is configured to input a torque waveform to the polishing end point prediction model M2 during polishing of the substrate W, and to output a polishing end point index of the substrate W from the polishing end point prediction model M2. The torque waveform input to the polishing end-point prediction model M2 is the same as the torque waveform input to the step-difference elimination prediction model M1. The polishing end point index is an index indicating the difference between the current time and the polishing end point (expressed in% level, time to polishing end point, etc.).
The polishing endpoint prediction model M2 is a learning completion model constructed by machine learning such as deep learning, reinforcement learning, quantum computing, and the like. The learning completion model is also referred to as an adjusted model or an adjusted neural-like network. The training data used for machine learning includes a plurality of training torque waveforms (a driving current waveform of the table motor 6, a driving current waveform of the polishing head motor 17, or a driving current waveform of the swing motor 18) obtained when at least one training substrate is polished to reach the polishing end point thereof. More specifically, the motion control unit 9 represents a plurality of training torque waveforms of drive currents of motors (the table motor 6, the polishing head motor 17, or the swing motor 18) required for relatively moving the training substrate with respect to the polishing surface 2a while polishing the training substrate to the polishing end point. The motion control unit 9 performs machine learning using a plurality of training torque waveforms and training data including a plurality of polishing end point indices as positive labels, thereby constructing a polishing end point prediction model M2.
The polishing apparatus polishes the substrate W by pressing the substrate W against the polishing surface 2a of the polishing pad 2 by the polishing head 10 while rotating the polishing table 3 supporting the polishing pad 2, and the operation control unit 9 generates a torque waveform (a driving current waveform of the table motor 6, a driving current waveform of the polishing head motor 17, or a driving current waveform of the swing motor 18) indicating a driving current of a motor required for relatively moving the substrate W with respect to the polishing surface 2a during polishing of the substrate W, inputs the torque waveform into the step elimination prediction model M1 (learning completion model), outputs a step elimination index of the surface of the substrate W from the step elimination prediction model M1, further inputs the torque waveform into the polishing end prediction model M2 (learning completion model), and outputs a polishing end index of the substrate W from the polishing end prediction model M2.
The torque waveform of the polishing end point prediction model M2 input to the learning completion model and the training torque waveform used for machine learning may be processed torque waveforms. Examples of the processed torque waveform include a torque waveform obtained by applying a filter to the torque waveform and a torque waveform obtained by amplifying the torque waveform by an amplifier.
In one embodiment, the training data used in the machine learning for constructing the polishing endpoint prediction model M2 may further include the number of substrates polished using the polishing pad 2 in the past. The operation control unit 9 may be configured to input the number of substrates polished by the polishing pad 2 in the past into the polishing end point prediction model M2 in addition to the torque waveform. The number of substrates polished using the polishing pad 2 in the past correlates with the wear of the polishing pad 2 and affects the polishing time to reach the polishing end point. Therefore, the present embodiment can output a more accurate polishing endpoint index.
The input data to the polishing endpoint prediction model M2 may further include data shown below, in addition to the torque waveform.
Output signal of film thickness sensor 20
Processed output signal of film thickness sensor 20
Number of substrates polished by the polishing pad 2 after finishing in the past
The training data used in the machine learning for constructing the grinding endpoint prediction model M2 may further include input data shown below.
The number of substrates polished by the polishing pad 2 and the polishing rate of each substrate in the past
Map of the number of substrates polished by the polishing pad 2 and the polishing rate of each substrate in the past
Number of substrates polished by the polishing pad 2 after finishing in the past
Next, another embodiment of a polishing method for predicting step elimination of the substrate W using the learning completion model will be described with reference to fig. 38. The configuration and operation of the present embodiment, which are not particularly described, are the same as those of the embodiment described above with reference to fig. 37, and thus, a repetitive description thereof will be omitted. The polishing apparatus shown in fig. 38 further includes a virtual polishing apparatus 110 for virtually polishing the substrate W in the virtual space. The dummy polishing apparatus 110 is connected to the film thickness sensor 20, and receives a film thickness signal indicating the film thickness of the substrate W from the film thickness sensor 20 during polishing of the substrate W.
The virtual polishing apparatus 110 includes: a storage device 110a storing a program; and a processing device 110b for executing an operation in accordance with a command included in the program. The processing device 110b includes a CPU (central processing unit), a GPU (graphics processing unit), or the like that performs operations in accordance with commands included in a program stored in the storage device 110 a. The storage device 110a includes: a main memory device (e.g., random access memory) accessible to the processing device 110 b; and an auxiliary storage device (e.g., hard disk drive or solid state drive) storing data and programs. The virtual polishing apparatus 110 is composed of at least 1 computer. However, the specific configuration of the virtual polishing apparatus 110 is not limited to this example.
The virtual polishing device 110 is connected to the operation control unit 9. And is configured to send the level difference elimination index outputted from the motion control unit 9 to the virtual polishing apparatus 110. The polishing end point index outputted from the polishing end point prediction model M2 of the motion control unit 9 is sent to the virtual polishing apparatus 110.
The virtual polishing apparatus 110 has an initial film thickness profile model M3, a step-difference-eliminating film thickness profile model M4, and a polishing end film thickness profile model M5 stored in a storage device 110a thereof. The virtual polishing apparatus 110 receives a film thickness signal indicating the film thickness of the substrate W from the film thickness sensor 20, inputs the film thickness signal into the initial film thickness profile model M3, and outputs a virtual initial film thickness profile of the substrate W from the initial film thickness profile model M3.
When the level difference elimination index outputted from the motion control unit 9 indicates that the surface level difference of the substrate W is eliminated, the virtual polishing apparatus 110 inputs the film thickness signal received from the film thickness sensor 20 into the level difference elimination film thickness map model M4, and outputs a virtual level difference elimination film thickness map of the substrate W from the level difference elimination film thickness map model M4.
When the polishing end point index outputted from the polishing end point prediction model M2 of the operation control unit 9 indicates that the polishing end point of the substrate W has been reached, the virtual polishing apparatus 110 inputs the film thickness signal received from the film thickness sensor 20 into the polishing end point film thickness profile model M5, and outputs a virtual polishing end point film thickness profile of the substrate W from the polishing end point film thickness profile model M5.
The initial film thickness profile model M3, the step-difference-eliminated film thickness profile model M4, and the polishing end-point film thickness profile model M5 are learning completion models constructed by machine learning such as deep learning, reinforcement learning, quantum computation, and the like.
The motion control unit 9 and the virtual polishing apparatus 110 can execute processing in parallel. That is, the motion control unit 9 may calculate the step elimination index and the polishing end point index using the step elimination prediction model M1 and the polishing end point prediction model M2, respectively, and the virtual polishing apparatus 110 may generate a virtual initial film thickness profile, a virtual step elimination film thickness profile, and a virtual polishing end point film thickness profile using the initial film thickness profile model M3, the step elimination film thickness profile model M4, and the polishing end point film thickness profile model M5.
In one embodiment, the virtual polishing apparatus 110 may also have one of a step-difference-eliminating film thickness profile model M4 or a polishing endpoint film thickness profile model M5. In one embodiment, the virtual polishing apparatus 110 may be configured to calculate a virtual initial film thickness profile, a virtual step-elimination film thickness profile, and a virtual polishing end film thickness profile by simulation instead of the initial film thickness profile model M3, the step-elimination film thickness profile model M4, and the polishing end film thickness profile model M5.
The above-described embodiments are described with the object of enabling a person having ordinary skill in the art to which the present invention pertains to practice the present invention. Various modifications of the above embodiments can be made by those skilled in the art, and the technical idea of the present invention is applicable to other embodiments. Therefore, the present invention is not limited to the embodiments described above, but is to be interpreted in accordance with the broadest scope of the technical idea defined by the claims.
[ Industrial applicability ]
The present invention can be used for a polishing method and a polishing apparatus for polishing a substrate such as a wafer.
Symbol description
1 grinding assembly
2 polishing pad
2a grinding surface
3 grinding table
5 grinding fluid supply nozzle
6 motors
8 torque measuring device
9 action control part
10 grinding head
11-head shaft lever
13 head main body
14 support shaft
15 rotary joint
16 swing arm
17 grinding head motor
18 swing motor
19 angle sensor
20 film thickness sensor
21 optical sensor head
24 light source
27 beam splitter
40 clasp
42 drive ring
45 elastic film
46. 47, 48, 49 pressure chambers
50 clasp pressure chamber
52 clasp press
53 piston
54 rolling diaphragm
60 shell
61 loading/unloading section
63 grinding part
64 swing conveyer
65 load port
66 loader (carrying robot)
67 first temporary placing table
68 second temporary placing table
69 transfer robot
70 cleaning part
74 first cleaning assembly
75 second cleaning assembly
76 third cleaning assembly
77 drying assembly
78 linear conveyor
80 film thickness measuring device
82 light projecting part
85 light receiving section
87 gas supply nozzle
89 waste liquid path
90 liquid supply nozzle
100 silicon layer
101 stop layer
102 insulating film
110 virtual grinding device
R1, R2, R3, R4, R5 pressure regulators.