US20130331004A1 - Semiconductor device manufacturing method and chemical mechanical polishing method - Google Patents

Abstract

According to one embodiment, a semiconductor device manufacturing method comprises forming a film to be polished on a semiconductor substrate, and performing a CMP method on the film to be polished. The CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-132383, filed Jun. 11, 2012, the entire contents of which are incorporated herein by reference.
FIELD
• Embodiments described herein relate generally to a semiconductor device manufacturing method and chemical mechanical polishing method.
BACKGROUND
• Semiconductor device manufacturing steps include shallow trench isolation (STI)-chemical mechanical polishing (CMP) and pre-metal dielectric (PMD)-CMP. In these CMP methods, a film to be polished such as a silicon oxide film formed on a semiconductor substrate is planarized.
• For example, a ceria-based slurry is used in the planarization (CMP) of a silicon oxide film. The ceria-based slurry has a high polishing rate for a silicon oxide film, and has a high planarization performance. Even when using the ceria-based slurry, however, many scratches are produced on the surface of a film to be polished (silicon oxide film) after CMP, depending on the surface state of a polishing pad. As a consequence, the yield and reliability decrease.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a view showing the arrangement of a CMP apparatus according to an embodiment;
• FIG. 2 is a plan view showing the CMP apparatus according to the embodiment;
• FIG. 3 is a flowchart showing a semiconductor device manufacturing method according to the embodiment;
• FIG. 4 is a view for explaining the Rsk value;
• FIG. 5 is a graph showing the relationship between the Rsk value on the surface of a polishing pad and the number of scratches on the surface of a film to be polished in a polishing experiment;
• FIG. 6 is a graph showing the relationship between the surface temperature and Rsk value of a polishing pad in a conditioning experiment; and
• FIGS. 7 and 8 are sectional views showing semiconductor device STI manufacturing steps according to the embodiment.
DETAILED DESCRIPTION
• In general, according to one embodiment, a semiconductor device manufacturing method comprises forming a film to be polished on a semiconductor substrate, and performing a CMP method on the film to be polished. The CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.
• This embodiment will be explained below with reference to the accompanying drawings. In these drawings, the same reference numbers denote the same parts. Also, a repetitive explanation will be made as needed.
Embodiment
• The embodiment will be explained with reference toFIGS. 1,2,3,4,5,6,7, and8. In this embodiment, in a CMP method of a semiconductor device manufacturing method, the surface of apolishing pad11 is conditioned such that the Rsk value becomes negative, and a film to be polished is brought into contact with (slid against) the rotatingpolishing pad11. This can reduce scratches on the surface of the film to be polished after CMP. The semiconductor device manufacturing method according to the embodiment will be explained in detail below.
[CMP Apparatus]
• First, a CMP apparatus according to this embodiment will be explained below with reference toFIGS. 1 and 2.
• FIG. 1 is a view showing the arrangement of the CMP apparatus according to the embodiment.FIG. 2 is a plan view showing the CMP apparatus according to the embodiment.
• As shown inFIG. 1, the CMP apparatus according to this embodiment includes aturntable10,polishing pad11,top ring12,slurry supply nozzle13, dressingliquid supply nozzle14,dresser15, and inlettemperature measurement device16.
• Thetop ring12 holding asemiconductor substrate20 is brought into contact with thepolishing pad11 attached to theturntable10. A film to be processed such as a silicon oxide film is formed on thesemiconductor substrate20. Theturntable10 can rotate at 1 to 200 rpm, and thetop ring12 can also rotate at 1 to 200 rpm. Theturntable10 andtop ring12 rotate in the same direction, for example, counterclockwise. Also, theturntable10 andtop ring12 rotate in a predetermined direction during CMP. The polishing load of these members is normally about 50 to 500 hPa.
• Theslurry supply nozzle13 is positioned above thepolishing pad11. Theslurry supply nozzle13 can supply a predetermined liquid chemical as a slurry at a flow rate of 50 to 1,000 cc/min. Note that theslurry supply nozzle13 is positioned near the center of theturntable10, but the position is not limited to this, and theslurry supply nozzle13 may also appropriately be positioned so as to supply the slurry on the entire surface of thepolishing pad11.
• Thedresser15 conditions the surface of thepolishing pad11 when brought into contact with thepolishing pad11. Thedresser15 can rotate at 1 to 200 rpm. Thedresser15 rotates, for example, counterclockwise. Also, theturntable10 anddresser15 rotate in a predetermined direction during conditioning. The dressing load of thedresser15 is normally about 50 to 500 hPa. The inlettemperature measurement device16 as an infrared radiation thermometer is attached to a pillar portion (dresser driving shaft) connected to thedresser15. Details of the inlettemperature measurement device16 will be described later.
• In addition, the dressingliquid supply nozzle14 is positioned above thepolishing pad11. The dressingliquid supply nozzle14 can supply a predetermined liquid as a dressing liquid at a flow rate of 50 to 1,000 cc/min. Note that the dressingliquid supply nozzle14 is positioned near the center of theturntable10, but the position is not limited to this, and the dressingliquid supply nozzle14 may also appropriately be positioned so as to supply the dressing liquid on the entire surface of thepolishing pad11.
• The dressing liquid is, for example, pure water, and the supply temperature of the liquid is appropriately set. By controlling this dressing liquid supply temperature, the inlet temperature to be measured by the inlettemperature measurement device16 can be adjusted.
• As shown inFIG. 2, the inlettemperature measurement device16 is installed upstream in the rotating direction of theturntable10 with respect to thedresser15. Therefore, the inlettemperature measurement device16 measures the surface temperature (inlet temperature) of thepolishing pad11 on the upstream side in the rotating direction of theturntable10 with respect to thedresser15.
• The inlettemperature measurement device16 measures the temperature of thepolishing pad11 on a circular orbit X passing a center O′ of thedresser15 and having a predetermined distance from a center O of theturntable10. This is so because the time during which thedresser15 andpolishing pad11 are in contact with each other is long on the circular orbit X, and so the highest temperature can be measured.
• Near the edge of thedresser15, the dressing liquid collides against thedresser15 and rises. When temperature measurement is performed near the edge of thedresser15, therefore, the inlettemperature measurement device16 may measure not the surface temperature of thepolishing pad11 but the temperature of the dressing liquid by mistake. To measure the surface temperature of thepolishing pad11, the inlettemperature measurement device16 desirably measures the temperature at an inlet temperature measurement point A positioned on the circular orbit X and spaced apart by a distance d (for example, 10 mm) from thedresser15.
• Note that when the dressing liquid is supplied to the entire surface of thepolishing pad11, it is possible to measure the temperature at any point on the surface of thepolishing pad11, including the inlet temperature measurement point A, as the surface temperature of thepolishing pad11. That is, the inlettemperature measurement device16 can be installed in any position as long as the temperature at any point on the surface of thepolishing pad11 can be measured.
[Manufacturing Method]
• Next, the semiconductor device manufacturing method according to this embodiment will be explained with reference toFIG. 3.
• FIG. 3 is a flowchart showing the semiconductor device manufacturing method according to the embodiment.
• As shown inFIG. 3, in step S1, a film to be polished is formed on thesemiconductor substrate20. This film to be polished is, for example, a silicon oxide film when forming an STI structure or PMD structure, but is not limited to this.
• Then, in step S2, a CMP method is performed on the film to be polished. In this step, the CMP method according to this embodiment is performed under the following conditions.
• First, in step S21, thepolishing pad11 is conditioned. More specifically, thedresser15 is brought into contact with the surface of thepolishing pad11, and slid against thepolishing pad11. In addition, the dressingliquid supply nozzle14 supplies the dressing liquid, for example, pure water to the surface of thepolishing pad11.
• As thepolishing pad11, a material mainly containing polyurethane and having a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa is attached to theturntable10. Also, the rate of rotation of theturntable10 is set at, for example, 10 (inclusive) to 110 (inclusive) rpm. As thedresser15, a material having a diamond roughness of #100 (inclusive) to #200 (inclusive) (manufactured by Asahi Diamond) is used. The rate of rotation of thedresser15 is set at 10 (inclusive) to 110 (inclusive) rpm, and the dressing load is set at 50 (inclusive) to 300 (inclusive) hPa. The conditioning time is set at 60 s.
• When supplying pure water, the supply temperature and supply flow rate of the pure water are controlled so that the surface temperature of the polishing pad11 (the temperature measured at the inlet temperature measurement point A by the inlet temperature measurement device16) is 23° C. or more. Consequently, the Rsk value of thepolishing pad11 can be set at −0.5 or less.
• Then, the film to be polished is polished in step S22. More specifically, the film to be polished held by thetop ring12 is brought into contact with theconditioned polishing pad11, and slid against thepolishing pad11. The rate of rotation of thetop ring12 is set at, for example, 120 rpm, and the polishing load is set at, for example, 300 gf/cm². Also, theslurry supply nozzle12 supplies the slurry at a flow rate of 100 cc/min. The slurry contains cerium oxide (DLS2 manufactured by Hitachi Chemical) as abrasive grains and ammonium polycarboxylate (TK75 manufactured by Kao).
• By thus polishing the film to be polished by bringing its surface into contact with the surface of therotating polishing pad11 having an Rsk value of −0.5 or less, the number of scratches on the surface of the polished film can be reduced. The basis for this will be described later.
• Note that the Rsk value on the surface of thepolishing pad11 is desirably −0.5 or less, and more desirably, −1.0 or less. However, the Rsk value on the surface of thepolishing pad11 is not limited to this, and need only be negative. As will be described later, when the surface temperature of thepolishing pad11 is raised during conditioning, the Rsk value of thepolishing pad11 decreases (i.e., the Rsk value becomes a negative value having a large absolute value). That is, the Rsk value is desirably decreased by raising the surface temperature of thepolishing pad11 during conditioning. However, the Rsk value of thepolishing pad11 may only be a negative value even when the surface temperature of thepolishing pad11 is less than 23° C.
• FIG. 4 is a view for explaining the Rsk value.
• The Rsk value (roughness curve skewness value) indicates the relativity of a probability density distribution with respect to the average line of a surface roughness profile.
• When the probability density distribution is biased below the average line of the surface roughness profile as indicated by (a) inFIG. 4, the Rsk value is positive. In this state, the number of projecting portions is large, and that of flat portions is small.
• On the other hand, when the probability density distribution is biased above the average line of the surface roughness profile as indicated by (b) inFIG. 4, the Rsk value is negative. In this state, the number of projecting portions is small, and that of flat portions is large.
• That is, the surface is smoother when the Rsk value is negative than when it is positive.
[Basis of CMP Conditions]
• The basis of the CMP conditions according to this embodiment will now be explained with reference toFIGS. 5 and 6.
• First, a polishing experiment for checking the relationship between the Rsk value on the surface of thepolishing pad11 and the number of scratches on the surface of a film to be polished was conducted.
• FIG. 5 is a graph showing the relationship between the Rsk value on the surface of thepolishing pad11 and the number of scratches on the surface of the film to be polished in the polishing experiment. The Rsk value herein mentioned was calculated from the roughness measured by a high-field laser microscope, for example, HD100D (manufactured by Lasertec). The number of scratches was counted by a KLA2815 (manufactured by KLA-Tencor, SEM Review) after the surface of the film to be polished was lightly etched with diluted hydrofluoric acid after CMP.
• As shown inFIG. 5, when the surface of a film to be polished is polished by bringing the surface into contact with the surface of thepolishing pad11, there is a positive correlation (correlation coefficient=0.71) between the Rsk value on the surface of thepolishing pad11 and the number of scratches produced by the polishing on the surface of the film to be polished. In other words, the number of scratches on the surface of the film to be polished increases when the Rsk value of thepolishing pad11 increases, and decreases when the Rsk value decreases.
• Also, as the Rsk value on the surface of thepolishing pad11 increases toward the negative side (as the absolute value of the negative Rsk value increases), the number of scratches on the surface of the film to be polished decreases, and the variation in number decreases. Especially when the Rsk value on the surface of thepolishing pad11 is −0.5 or less, more desirably, −1.0 or less, the number of scratches on the surface of the film to be polished further decreases, and the variation in number further decreases.
• As described above, the number of scratches on the surface of the film to be polished can be decreased by polishing the film by setting the Rsk value on the surface of thepolishing pad11 at a negative value having a large absolute value. Accordingly, the Rsk value on the surface of thepolishing pad11 is desirably set at a negative value having a large absolute value by conditioning.
• Then, a conditioning experiment for checking the relationship between the surface temperature and Rsk value of thepolishing pad11 was conducted. In this experiment, the surface temperature of thepolishing pad11 to be measured by the inlettemperature measurement device16 was adjusted by controlling the dressing liquid to be supplied from the dressingliquid supply nozzle14 in the above-described CMP apparatus. The conditioning experiment was conducted under the following conditions.
• Polishing pad: Polyurethane (Shore D hardness=60, modulus of elasticity=400 MPa)
  Turntable rate of rotation: 20 rpm
  Dresser: Diamond roughness=#100 (available from Asahi Diamond)
  Dresser load: 200 hPa
  Dresser rate of rotation: 20 rpm
• Conditioning experiments were conducted for 60 sec by using pure water as the dressing liquid, and setting the supply temperature at 5, 23 (room temperature), and 65° C. In these conditioning experiments, the surface temperatures of thepolishing pad11 measured by the inlettemperature measurement device16 were 9, 23, and 41° C.
• FIG. 6 is a graph showing the relationship between the surface temperature and Rsk value of thepolishing pad11 in the conditioning experiment.
• As shown inFIG. 6, when conditioning the surface of thepolishing pad11 by thedresser15, there is a negative correlation between the surface temperature of thepolishing pad11 during the conditioning, and the resultant Rsk value of thepolishing pad11. In other words, the Rsk value of thepolishing pad11 decreases when the surface temperature of thepolishing pad11 rises, and increases when the surface temperature decreases. More specifically, the Rsk values of thepolishing pad11 are −0.43, −0.56, and −0.78 when the surface temperatures of thepolishing pad11 are 9, 23, and 41° C., respectively.
• As described above, the Rsk value on the surface of thepolishing pad11 is desirably set at a negative value having a large absolute value by conditioning. The Rsk value on the surface of thepolishing pad11 can be set at a negative value having a large absolute value by increasing the surface temperature of thepolishing pad11 during conditioning. For example, when supplying pure water in conditioning, the Rsk value on the surface of thepolishing pad11 can sufficiently be set at −0.5 or less by setting the surface temperature of thepolishing pad11 at 23° C. or more.
• On the other hand, the polishing rate of thepolishing pad11 during conditioning depends on the surface temperature of thepolishing pad11. The polishing rate decreases when the surface temperature of thepolishing pad11 rises, and increases when the surface temperature decreases. More specifically, the polishing rates of thepolishing pad11 during conditioning are 0.9, 0.5, and 0.05 μm/min when the surface temperatures of thepolishing pad11 are 9, 23, and 41° C., respectively. This is so probably because when the surface temperature of thepolishing pad11 rises, thepolishing pad11 softens (the modulus of elasticity decreases), and polishing becomes difficult. That is, the useful life of thepolishing pad11 can be prolonged by raising the surface temperature of thepolishing pad11.
• As described above, when performing conditioning by raising the surface temperature of thepolishing pad11, it is possible to set the Rsk value of thepolishing pad11 at a negative value having a large absolute value, and decrease the polishing rate of thepolishing pad11.
• Note that the surface temperature of thepolishing pad11 is the inlet temperature of thepolishing pad11 measured by the inlettemperature measurement device16, and can be measured at any point on the surface of thepolishing pad11 when the dressing liquid is supplied on the entire surface of thepolishing pad11.
[Effects]
• In the CMP method of the semiconductor device manufacturing method according to the abovementioned embodiment, after the surface of thepolishing pad11 is conditioned at a high temperature, a film to be polished is polished by bringing its surface into contact with the surface of thepolishing pad11. This can achieve the following effects.
• Since the surface of thepolishing pad11 is conditioned at a higher temperature, the Rsk value on the surface of thepolishing pad11 can be set at a negative value having a larger absolute value. For example, when supplying pure water in conditioning, the Rsk value on the surface of thepolishing pad11 can be set at −0.5 or less by setting the surface temperature of thepolishing pad11 at 23° C. or more. When a film to be polished is polished by bringing its surface into contact with the surface of thepolishing pad11 having this negative Rsk value, the number of scratches on the surface of the film to be polished after CMP can be reduced. Consequently, it is possible to suppress the decrease in device yield and reliability.
• It is also possible to decrease the polishing rate of thepolishing pad11 by conditioning the surface of thepolishing pad11 at a higher temperature. This makes it possible to prolong the service life of thepolishing pad11, and reduce the cost of the CMP step.
Application Example
• An application example of the semiconductor device manufacturing method according to this embodiment will be explained below with reference toFIGS. 7 and 8. In this example, a method of manufacturing an STI structure in a semiconductor device will be explained.
• FIGS. 7 and 8 are sectional views showing semiconductor device STI manufacturing steps according to the embodiment.
• First, as shown inFIG. 7, asilicon nitride film21 functioning as a stopper film is formed on asemiconductor substrate20. After that,STI patterns22 are formed in thesemiconductor substrate20 by using a silicon oxide film or the like as an etching mask. Note that it is also possible to form, for example, a silicon oxide film between thesemiconductor substrate20 andsilicon nitride film21.
• Then, asilicon oxide film23 is formed on the entire surface by, for example, high-density plasma chemical vapor deposition (CVD). In this step, thesilicon oxide film23 is formed outside theSTI patterns22.
• Subsequently, as shown inFIG. 8, CMP is performed using thesilicon oxide film23 as a film to be processed, thereby polishing the surface of the film. The embodiment is applied to this CMP step. That is, after conditioning is performed such that the Rsk value on the surface of thepolishing pad11 becomes a negative value, thesilicon oxide film23 is polished by bringing its surface into contact with the surface of thepolishing pad11. Consequently, thesilicon oxide film23 outside theSTI patterns22 is removed, and an STI structure is formed.
• The present embodiment is not limited to this, and the CMP method according to this embodiment is applicable to CMP performed for various metal materials and various insulating materials as films to be processed.
• While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims (20)

What is claimed is:

1. A semiconductor device manufacturing method comprising:

forming a film to be polished on a semiconductor substrate; and

performing a CMP method on the film to be polished,

wherein the CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

2. The method ofclaim 1, wherein the Rsk value is not more than −0.5.

3. The method ofclaim 1, wherein the Rsk value is not more than −1.0.

4. The method ofclaim 1, wherein before the polishing the film to be polished, the CMP method further comprises conditioning the polishing pad by bringing a dresser into contact with the surface of the polishing pad while supplying pure water to the surface of the polishing pad.

5. The method ofclaim 4, wherein a surface temperature of the polishing pad is not less than 23° C. in the conditioning the polishing pad.

6. The method ofclaim 5, wherein

the polishing pad is rotated in the conditioning the polishing pad, and

the surface temperature of the polishing pad is an inlet temperature of the polishing pad on an upstream side in a rotating direction with respect to the dresser.

7. The method ofclaim 5, wherein the surface temperature of the polishing pad is controlled by a supply temperature and supply flow rate of the pure water.

8. The method ofclaim 4, wherein

the polishing pad is rotated in the conditioning the polishing pad, and

a rate of rotation of the polishing pad is 10 (inclusive) to 110 (inclusive) rpm.

9. The method ofclaim 4, wherein

the dresser is rotated in the conditioning the polishing pad, and

a rate of rotation of the dresser is 10 (inclusive) to 110 (inclusive) rpm.

10. The method ofclaim 4, wherein a load of the dresser to be brought into contact with the surface of the polishing pad is 50 (inclusive) to 300 (inclusive) hPa.

11. The method ofclaim 1, wherein the polishing pad contains polyurethane as a main material, and has a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa.

12. The method ofclaim 1, wherein the film to be polished is a silicon oxide film to be used as an STI structure.

13. A chemical mechanical polishing method comprises polishing a film to be polished formed on a substrate by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

14. The method ofclaim 13, wherein the Rsk value is not more than −0.5.

15. The method ofclaim 13, wherein the Rsk value is not more than −1.0.

16. The method ofclaim 13, further comprising, before the polishing the film to be polished, conditioning the polishing pad by bringing a dresser into contact with the surface of the polishing pad while supplying pure water to the surface of the polishing pad.

17. The method ofclaim 16, wherein a surface temperature of the polishing pad is not less than 23° C. in the conditioning the polishing pad.

18. The method ofclaim 17, wherein

the polishing pad is rotated in the conditioning the polishing pad, and

the surface temperature of the polishing pad is an inlet temperature of the polishing pad on an upstream side in a rotating direction with respect to the dresser.

19. The method ofclaim 17, wherein the surface temperature of the polishing pad is controlled by a supply temperature and supply flow rate of the pure water.

20. The method ofclaim 13, wherein the polishing pad contains polyurethane as a main material, and has a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa.

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