CROSS-REFERENCE TO RELATED APPLICATIONS: This document claims priority to Japanese Patent Application Number 2004-357292, filed Dec. 9, 2004 and U.S. Provisional Application No. 60/639,795, filed Dec. 29, 2004, the entire content of which are hereby incorporated by reference.
FIELD OF THE INVENTION The present invention relates to a gas supply unit for supplying a gas to a processing chamber, a substrate processing apparatus connected to the gas supply unit and a supply gas setting method.
BACKGROUND OF THE INVENTION In a manufacturing process of an electric device such as a semiconductor device or a liquid crystal display device, there are performed a film forming process for forming a conductive film or an insulating film on the surface of a substrate, an etching process for etching a film formed on the substrate and the like.
For example, a plasma etching apparatus is widely employed in the etching process, wherein the plasma etching apparatus includes a processing chamber for accommodating therein a substrate. In the processing chamber, there are installed a lower electrode for mounting the substrate thereon and a shower head, also serving as an upper electrode, for injecting a gas onto the substrate mounted on the lower electrode. In the etching process, while a specified gaseous mixture is injected through the shower head, a radio frequency power is applied between the electrodes. Accordingly, a plasma is generated in the processing chamber and a film formed on the substrate is etched by the plasma.
However, etching characteristics such as an etching rate and an etching selectivity are influenced by a concentration of a gas supplied onto the substrate. Further, conventionally, it has been a major challenge to improve a uniformity of etching in the surface of the substrate by making the etching characteristics uniform on the surface of the substrate. Thus, there is proposed a technique of dividing an inner space of the shower head into a plurality of gas chambers, wherein each gas chamber is independently connected to an individual gas introduction line such that a gaseous mixture containing gases whose kinds and flow rates are optionally chosen based on the necessity can be supplied to each portion in the surface of the substrate (see, e.g., Reference 1). Consequently, a partial gas concentration on a small part in the surface of the substrate can be locally controlled to thereby improve an etching uniformity on the surface of the substrate.
However, the gaseous mixture for use in the etching process contains various gases, for example, an etching gas, a gas for controlling deposits of reaction products, a carrier gas such as an inert gas, that are chosen depending on a material to be etched, process conditions and the like. Accordingly, for example, when an inner space of the shower head is divided into a plurality of gas chambers and a gas introduction line is independently connected to each of the gas chambers, as shown in FIG. 1 of Reference 2, each gas introduction line is connected to lines communicating with multiple gas supply sources and, further, a mass flow controller is provided in each line. Thus, a piping structure of a gas supply system becomes complicated and a control of gas flow rate is also complicated in each line. Therefore, for example, a large piping space is required, which in turn increases the expense of an apparatus control system.
[Reference 1] Japanese Patent Laid-open Application No. 8-158072
[Reference 2] Japanese Patent Laid-open Application No. 9-45624
SUMMARY OF THE INVENTION The present invention has been conceived from the above drawbacks; and it is, therefore, an object of the present invention to provide a gas supply unit capable of realizing a simple piping configuration when supplying optional gaseous mixtures to a plurality of places in a processing chamber in a substrate processing apparatus such as an etching apparatus, a substrate processing apparatus including a processing chamber connected to the gas supply unit and a supply gas setting method employing the gas supply unit.
To achieve the object, in accordance with one aspect of the present invention, there is provided a gas supply unit for supplying a gas into a processing chamber in which a substrate is processed, the gas supply unit including a plurality of gas supply sources; a mixing line for mixing a plurality of gases supplied from the gas supply sources to make a gaseous mixture; a multiplicity of branch lines for branching the gaseous mixture to be supplied to a multiplicity of places in the processing chamber; and an additional gas supply unit for supplying a specified additional gas to a gaseous mixture flowing in at least one branch line.
In accordance with the present invention, gases from a plurality of the gas supply sources are mixed in the mixing line to be branched into a multiplicity of the branch lines. Further, a specified additional gas is added to a specific branch line to adjust components or their flow rates in the gaseous mixture. In a branch line without being supplied with the additional gas, the gaseous mixture from the mixing line is supplied to the processing chamber as it is. In this case, a gaseous mixture containing common components is produced in, e.g., the mixing line and components and their flow rates in the gaseous mixture are adjusted in each branch line when necessary. Thus, the number of lines needed is minimized. As a result, optional gaseous mixtures are supplied to a plurality of places in the processing chamber by a simple piping configuration.
The gas supply unit may include pressure gauges and valves for adjusting gas flow rates in the branch lines, respectively, and a pressure ratio controller for controlling that gaseous mixtures branched into the branch lines to have a specified pressure ratio by adjusting opening degrees of the valves based on measurement results obtained by using the pressure gauges. In this case, since the flow rate in the branch line is controlled on the basis of a pressure ratio (partial pressure ratio), for example, even though a pressure in the branch line is low, the flow rate in the branch line can be adequately controlled.
In accordance with another aspect of the present invention, there is provided a substrate processing apparatus, including a processing chamber accommodating therein a substrate; a plurality of gas supply sources; a mixing line for mixing a plurality of gases supplied from the gas supply sources to make a gaseous mixture; a multiplicity of branch lines for branching the gaseous mixture to be supplied to a multiplicity of places in the processing chamber; and an additional gas supply unit for supplying a specified additional gas to a gaseous mixture flowing in at least one branch line.
In accordance with still another aspect of the present invention, there is provided a supply gas setting method using the gas supply unit which includes a plurality of gas supply sources; a mixing line for mixing a plurality of gases supplied from the gas supply sources to make a gaseous mixture; a multiplicity of branch lines for branching the gaseous mixture to be supplied to a multiplicity of places in the processing chamber; an additional gas supply unit for supplying a specified additional gas to a gaseous mixture flowing in at least one branch line; and valves and pressure gauges for adjusting gas flow rates in the branch lines, respectively, the method including the following sequential steps of controlling a pressure ratio of the gaseous mixtures branched into the branch lines to be a specified pressure ratio by adjusting the valves under a condition in which the additional gas is not supplied to said at least one branch line from the additional gas supply unit and, then, fixing opening degrees of the valves of the branch lines to values obtained under the condition; and supplying an additional gas of a specified flow rate to said at least one branch line from the additional gas supply unit.
In accordance with the present invention, a piping space and a cost of controlling flow rates can be reduced by a simple piping configuration.
BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
FIG. 1 is a longitudinal sectional view showing a schematic configuration of a plasma etching apparatus;
FIG. 2 shows a cross sectional view of an inner upper electrode;
FIG. 3 explains a schematic configuration of a gas supply unit;
FIG. 4 is a flowchart for setting a supply gas;
FIG. 5 shows a schematic configuration of a gas supply unit for supplying gaseous mixtures to three places in a processing chamber; and
FIG. 6 shows a schematic configuration of a gas supply unit for supplying a gaseous mixture from a side surface portion of a processing chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described.FIG. 1 is a longitudinal sectional view showing a schematic configuration of aplasma etching apparatus1 serving as a substrate processing apparatus including a gas supply unit in accordance with the preferred embodiment of the present invention.
Theplasma etching apparatus1 is a capacitively coupled plasma etching apparatus having a parallel plate type electrode structure. Theplasma etching apparatus1 includes an approximatelycylindrical processing chamber10 that is grounded. Theprocessing chamber10 is formed of, e.g., aluminum alloy and the inner wall surface thereof is covered by an alumina film or an yttrium oxide film.
A cylindrical susceptor supporting table14 is disposed in a central bottom portion of theprocessing chamber10 via aninsulating plate12. Asusceptor16, serving as a mounting table, for mounting thereon a wafer W, i.e., a substrate, is disposed on the susceptor supporting table14. Further, thesusceptor16 also serves as a lower electrode of the parallel plate type electrode structure and is formed of, e.g., aluminum alloy.
An electrostatic chuck18 for holding the wafer. W is disposed on thesusceptor16, and the electrostatic chuck18 has anelectrode20 therein. A DC power supply22 is electrically connected to theelectrode20. The wafer W can be adsorbed on the top surface of thesusceptor16 by Coulomb force generated by a DC voltage applied to theelectrode20 from the DC power supply22.
Afocus ring24 is disposed on thesusceptor16 to surround the electrostatic chuck18. A cylindricalinner wall member26 formed of, e.g., quartz is attached to an outer peripheral surface of thesusceptor16 and the susceptor supporting table14.
Anannular coolant chamber28 is formed inside the susceptor supporting table14. Thecoolant chamber28 communicates with a chiller unit (not shown) installed outside theprocessing chamber10 vialines30aand30b. A coolant or cooling water is supplied into thecoolant chamber28 through thelines30aand30bto be circulated therein, thereby controlling the temperature of the wafer W on thesusceptor16. Agas supply line32 passing through thesusceptor16 and the susceptor supporting table14 reaches a top surface of the electrostatic chuck18, whereby a thermally conductive gas such as He gas can be supplied between the wafer W and the electrostatic chuck18.
Anupper electrode34 is disposed above thesusceptor16 to face it in parallel. A plasma generation space PS is formed between thesusceptor16 and theupper electrode34.
Theupper electrode34 includes an annular outerupper electrode36 and an innerupper electrode38 of a circular plate that is disposed inwardly from the outerupper electrode36. An annulardielectric material42 is interposed between the outerupper electrode36 and the innerupper electrode38. An annular insulatingshield member44 formed of, e.g., alumina is airtightly interposed between the outerupper electrode36 and an inner peripheral wall of theprocessing chamber10.
A first radiofrequency power supply54 is electrically connected to the outerupper electrode36 via amatching unit46, an upper power supply rod48, aconnector50 and apower supply case52. The first radiofrequency power supply54 can output a radio frequency voltage having a frequency equal to or larger than 40 MHz, e.g., a frequency of 60 MHz.
Thepower supply case52 is shaped like, for example, a cylinder with its bottom surface removed. A lower end portion of thepower supply case52 is connected to the outerupper electrode36. A central portion of the top surface of thepower supply case52 is electrically connected to a lower end portion of the upper power supply rod48 via theconnector50. An upper end portion of the upper power supply rod48 is connected to an output side of thematching unit46. The matchingunit46 is connected to the first radiofrequency power supply54, thereby matching an inner impedance of the first radiofrequency power supply54 with a load impedance. Thepower supply case52 is surrounded by acylindrical ground conductor10awhose sidewall has a same diameter as a sidewall of theprocessing chamber10. A lower end portion of theground conductor10ais connected to an upper portion of the sidewall of theprocessing chamber10. The upper power supply rod48 passes through a central portion of the top surface of theground conductor10a, and aninsulation member56 is interposed in a portion where the upper power supply rod48 is in contact with theground conductor10a.
The innerupper electrode38 functions as a shower head for injecting a specified gaseous mixture toward the wafer W mounted on thesusceptor16. The innerupper electrode38 includes acircular electrode plate60 having a plurality ofgas injection openings60aand anelectrode supporting member62 capable of supporting theelectrode plate60 by being attached to or detached from the top surface of theelectrode plate60. Theelectrode supporting member62 is shaped as a disc having a same diameter as theelectrode plate60, and acircular buffer space63 is formed inside theelectrode supporting member62. In thebuffer space63, for example, as shown inFIG. 2, anannular partition member64 formed of an O-ring is disposed, whereby thebuffer space63 is divided into afirst buffer space63aof a central side and asecond buffer space63bof an outer peripheral side. The first and thesecond buffer space63aand63bface a central portion and an outer peripheral portion of the wafer W loaded on thesusceptor16, respectively. Thegas injection openings60aare formed in the bottom surfaces of thebuffer spaces63aand63bto communicate with the plasma generation space, whereby specified gaseous mixtures can be injected through the first andsecond buffer spaces63aand63btoward the central portion and the outer peripheral portion of the wafer W, respectively. Further, agas supply unit100 for supplying a specified gaseous mixture to each chamber in thebuffer space63 will be described later.
As depicted inFIG. 1, a lowerpower supply case70 coupled to the upper power supply rod48 is electrically connected to the top surface of theelectrode supporting member62. Avariable condenser72 is installed in the lowerpower supply case70. Thevariable condenser72 can adjust a relative ratio between an intensity of an electric field formed right under the outerupper electrode36 and that formed right under the innerupper electrode38, which are generated by a radio frequency voltage from the first radiofrequency power supply54.
Agas exhaust port74 is formed in a bottom portion of theprocessing chamber10. Thegas exhaust port74 is connected to thegas exhaust unit78 including a vacuum pump and the like via agas exhaust pipe76. Theprocessing chamber10 can be depressurized to a desired vacuum level by using thegas exhaust unit78.
A second radiofrequency power supply82 is electrically connected to thesusceptor16 via amatching unit80. The second radiofrequency power supply82 can output a radio frequency voltage having a frequency ranging from, e.g., 2 MHz to 20 MHz, for example, a frequency of 20 MHz.
Electrically connected to the innerupper electrode38 is alow pass filter84 for passing a radio frequency wave generated from the second radiofrequency power supply82 to ground by shielding a radio frequency wave generated from the first radiofrequency power supply54. Electrically connected to thesusceptor16 is ahigh pass filter86 for passing a radio frequency wave generated from the first radiofrequency power supply54 to ground.
Theplasma etching apparatus1 includes anapparatus controller90 for controlling operations of various components such as the DC power supply22, the first radiofrequency power supply54 and the second radiofrequency power supply82 to perform an etching.
Hereinafter, agas supply unit100 for supplying gaseous mixtures to the innerupper electrode38 in theplasma etching apparatus1 will be described.
Thegas supply unit100, as shown inFIG. 3, includes afirst gas box111 accommodating plural, e.g., three,gas supply sources110a,110band110cand asecond gas box113 accommodating plural, e.g., two, additionalgas supply sources112aand112b. In this embodiment, for instance, thegas supply source110ais sealed to contain therein fluorocarbon-based fluorine compound serving as an etching gas such as CxFygas (e.g., CF4, C4F6, C4F8and C5F8); thegas supply source110bis sealed to contain therein a gas for controlling deposits of CF-based reaction products, e.g., O2gas; and thegas supply source110cis sealed to contain therein a rare gas serving as a carrier gas, e.g., an Ar gas. Further, the additionalgas supply source112ais sealed to contain therein, e.g., CxFygas capable of accelerating an etching, and the additionalgas supply source112bis sealed to contain therein, e.g., O2gas capable of controlling deposits of CF-based reaction products.
Amixing line120 in which various gases from thegas supply sources110a,110band110care combined to be mixed is connected to each of thegas supply sources110a,110band110cof thefirst gas box111. In themixing line120,mass flow controllers121 are installed for thegas supply sources110ato110c, respectively, to control flow rates of gases supplied from thegas supply sources110ato110c. Themixing line120 is coupled to afirst branch line122 and asecond branch line123 for branching a gaseous mixture that is mixed in themixing line120. Thefirst branch line122 is connected to thefirst buffer space63ain the innerupper electrode38 of theprocessing chamber10. Thesecond branch line123 is connected to thesecond buffer space63bin the innerupper electrode38.
Apressure control unit124 is installed in thefirst branch line122. In the same manner, apressure control unit125 is installed in thesecond branch line123. Thepressure control unit124 is provided with apressure gauge124aand avalve124b. Similarly, thepressure control unit125 is provided with apressure gauge125aand avalve125b. Measurement results respectively obtained by the pressure gauges124aand125aof thepressure control units124 and125 can be outputted to apressure ratio controller126. Thepressure ratio controller126 can control a pressure ratio, i.e., a flow rate ratio of gaseous mixtures branched into thefirst branch line122 and thesecond branch line123 by adjusting respective opening degrees of thevalves124band125bbased on the measurement results obtained by using the pressure gauges124aand125a. Further, when setting a supply gas, while an additional gas is not supplied to thesecond branch line123 from asecond gas box113 which will be described later, thepressure ratio controller126 controls a pressure ratio of the gaseous mixtures flowing in thefirst branch line122 and thesecond branch line123 to be a target pressure ratio and fixes respective opening degrees of thevalves124band125bto values obtained under this condition.
An additionalgas supply line130 communicating with, e.g., thesecond branch line123 is connected to each of additionalgas supply sources112aand112bof thesecond gas box113. For example, respective lines of the additionalgas supply line130 connected to the additionalgas supply sources112aand112bare combined in the middle thereof and then connected to thesecond branch line123. The additionalgas supply line130 is connected to a downstream side of thepressure control unit125. In the additionalgas supply line130,mass flow controllers131 are installed for the additionalgas supply sources112aand112b, respectively, to control flow rates of additional gases supplied from the additionalgas supply sources112aand112b. In this configuration, an additional gas that is chosen among gases from thesecond gas box113 or obtained by mixing the gases can be supplied to thesecond branch line123. Further, in this embodiment, an additional gas supply unit includes thesecond gas box113, the additionalgas supply sources112aand112b, the additionalgas supply line130 and themass flow controller131.
The operations of themass flow controllers121 in thefirst gas box111 and themass flow controllers131 in thesecond gas box113 are controlled by, e.g., theapparatus controller90 of theplasma etching apparatus1. Thus, various gases from thefirst gas box111 and thesecond gas box113 can be started or stopped to be supplied under the control of theapparatus controller90 which also controls respective flow rates thereof.
Hereinafter, operations of thegas supply unit100 having the above-mentioned configuration will be described.FIG. 4 is a flowchart for setting components or their flow rates in gaseous mixtures to be supplied into theprocessing chamber10. First, a preset gas in thefirst gas box111 flows at a specified flow rate in themixing line120 based on instruction signals of the apparatus controller90 (step S1 inFIG. 4). For example, the CxFygas, O2gas and Ar gas, which are supplied at specified flow rates from thegas supply sources110ato110c, respectively, are mixed in themixing line120, thereby producing a gaseous mixture containing CxFygas, O2gas and Ar gas having a specified mixing ratio. Subsequently, thepressure ratio controller126 controls opening degrees of thevalves124band125bbased on the measurement results obtained by the pressure gauges124aand125a, whereby a pressure ratio of gaseous mixtures respectively flowing in thefirst branch line122 and thesecond branch line123 is adjusted to be a target pressure ratio (step S2 inFIG. 4). Accordingly, the components (mixing ratio) and their flow rates in the gaseous mixture supplied into thefirst buffer space63athrough thefirst branch line122 are set. Further, at this time, at least, the same gas as the gaseous mixture supplied to thefirst buffer space63a, i.e., a gaseous mixture for etching, is supplied into thesecond buffer space63bthrough thesecond branch line123.
Then, when the gaseous mixtures respectively flowing in thefirst branch line122 and thesecond branch line123 are controlled to have the target pressure ratio to be stable, the opening degrees of thevalves124band125bof thepressure control units124 and125 are fixed by the pressure ratio controller126 (step S3 inFIG. 4). By an instruction signal from theapparatus controller90 after respective opening degrees of thevalves124band125bbeing fixed, a preset additional gas in thesecond gas box113 flows at a specified flow rate in the additional gas supply line130 (step S4 inFIG. 4). An instruction signal for starting the supply of the additional gas from thesecond gas box113 is sent after a setting time that is set in advance in theapparatus controller90 elapses. The CxFygas, e.g., CF4gas, capable of accelerating an etching is supplied at a specified flow rate from, e.g., the additionalgas supply source112ato flow through the additionalgas supply line130 which is combined with thesecond branch line123. Accordingly, thesecond buffer space63bcommunicating with thesecond branch line123 is supplied with a gaseous mixture containing a larger amount of CF4gas than the gaseous mixture supplied to thefirst buffer space63a. In this manner, the components and their flow rates in the gaseous mixture supplied into thesecond buffer space63bare set. Further, although the pressure ratio between the pressure in thefirst branch line122 and that in thesecond branch line123 is changed by supplying the additional gas into thesecond branch line123, a gaseous mixture having an original flow rate is supplied into thefirst buffer space63abecause thevalves124band125bare fixed.
Further, in theplasma etching apparatus1 having therein a depressurized atmosphere, the gaseous mixture from thefirst buffer space63ais supplied to the central portion of the wafer W on thesusceptor16 and the gaseous mixture containing plenty of CF4gas from thesecond buffer space63bis supplied to the outer peripheral portion of the wafer W. Accordingly, the etching characteristics of the outer peripheral portion of the wafer W are adjusted relatively to those of the central portion of the wafer W, thereby achieving uniform etching characteristics on the surface of the wafer W.
In accordance with the preferred embodiment, plural kinds of gases from the first gas box are mixed to make a gaseous mixture in themixing line120 and, then, the gaseous mixture are branched into thefirst branch line122 and thesecond branch line123, which are supplied into the first and thesecond buffer space63aand63bof theprocessing chamber10, respectively. The additional gas for adjusting the etching characteristics is supplied to thesecond branch line123, and thesecond buffer space63bis supplied with a gaseous mixture having components and flow rates different from those in thefirst buffer space63a. Therefore, components and their flow rates in gaseous mixtures supplied into the first and thesecond buffer space63aand63bcan be optionally adjusted by a simple piping configuration.
Further, since flow rates in the first and thesecond branch line122 and123 are respectively adjusted by thepressure control units124 and125, even if the pressure of the gas supply source is very low as in theplasma etching apparatus1, gas flow rates in supply lines can be adequately adjusted.
In the preferred embodiment, CF4gas is supplied into thesecond branch line123 to accelerate an etching. However, for example, when a deposit amount of CF-based reaction products is large and an etching rate is slow in the outer peripheral portion of the wafer W compared to that of the central portion thereof, O2gas may be supplied to thesecond branch line123 to remove CF-based reaction products. Further, it is possible to feed a gaseous mixture containing CF4gas and O2gas having a specified mixing ratio into thesecond branch line123.
A timing of supplying the additional gas from thesecond gas box113 to thesecond branch line123 is preset based on the setting time of theapparatus controller90 in the preferred embodiment. However, it is also possible to start supplying the additional gas in the manner that theapparatus controller90 monitors the measurement results obtained by the pressure gauges124aand125avia thepressure ratio controller126 and sends an instruction signal to thesecond gas box113 when a stable, desired target pressure ratio is achieved.
Further, the additionalgas supply sources112aand112bof thesecond gas box113 may be connected to thefirst branch line122 via the additionalgas supply line130. By doing this, components or flow rates in the gaseous mixture supplied to thefirst buffer space63 can be minutely controlled when necessary.
Although the additional gas supply sources for supplying CF4gas and O2gas are installed in thesecond gas box113 in the preferred embodiment, additional gas supply sources may supply other additional gases capable of accelerating or suppressing an etching, e.g., CxHyFzgas such as CHF3, CH2F2, CH3F for accelerating an etching, N2gas or CO gas for controlling CF-based reaction products, Xe gas or He gas for a dilution gas and the like. Besides, the number or kinds of gases accommodated in the first and thesecond gas box111 and113 can be optionally chosen depending on a material to be etched, process conditions and the like.
Thegas supply unit100 supplies gaseous mixtures to two places, i.e., the first and thesecond buffer space63aand63b, in theprocessing chamber10 in the preferred embodiment, but gaseous mixtures may be supplied to three places or more in theprocessing chamber10.FIG. 5 shows such an example, wherein the innerupper electrode38 includes abuffer space63 having three buffer spaces concentrically disposed. That is, an annularthird buffer space63cis formed further outside thesecond buffer space63bof the innerupper electrode38. In this case, themixing line120 is branched into the first and thesecond branch line122 and123 and, further, athird branch line150. Thethird branch line150 is connected to thethird buffer space63c. Similarly to thebranch lines122 and123, thethird branch lime150 is provided with apressure control unit151, apressure gauge151aand avalve151b. Further, thegas supply unit100 in this example is provided with athird gas box152 for supplying a specified additional gas to thethird branch line150. For example, thethird gas box152 has a same configuration as thesecond gas box113 and includes an additionalgas supply source153aof CF4gas and an additional gas supply source153bof O2gas. Both of the additionalgas supply sources153aand153bare connected to thethird branch line150 via an additionalgas supply line154. Provided in the additionalgas supply line154 aremass flow controllers155 for the additionalgas supply sources153aand153b, respectively. Further, the other configuration is same as in the above-mentioned preferred embodiment and, thus, the description thereof will be omitted.
Further, when gaseous mixtures are respectively supplied into thebuffer spaces63ato63c, gases from, e.g., thegas supply sources110ato110cof thefirst gas box111 are supplied into themixing line120 to be mixed therein, thereby producing a gaseous mixture. The gaseous mixture is branched into threebranch lines122,123 and150. The gas pressure ratio of thebranch lines122,123 and150 is adjusted to be a specified target pressure ratio by thepressure ratio controller126 and, then, opening degrees of thevalves124b,125band151bare fixed. Accordingly, components and their flow rates in the gaseous mixture to be supplied to thefirst buffer space63acommunicating with thefirst branch line122 are set. Thereafter, an additional gas of a specified kind is supplied at a specified flow rate into thesecond branch line123 from thesecond gas box113 via the additionalgas supply line130. Further, an additional gas of a specified kind is supplied at a specified flow rate into thethird branch line150 from thethird gas box152 via the additionalgas supply line154. Accordingly, the components and flow rates in the gaseous mixtures supplied into the second and thethird buffer space63band63care set. Also in this case, optional gaseous mixtures can be supplied into three places in theprocessing chamber10 by a simple piping configuration.
In the preferred embodiment, the gaseous mixtures supplied from thegas supply unit100 are injected toward the wafer W through an upper portion of theprocessing chamber10. However, the gaseous mixtures may be injected through another portion of theprocessing chamber10, e.g., a side surface portion of the plasma generation space PS in theprocessing chamber10. In such a case, for example, as shown inFIG. 6, thethird branch line150 is connected to both side surfaces of theprocessing chamber10 and the gaseous mixtures are injected into the plasma generation space PS from nozzles connected to the both side surfaces of theprocessing chamber10. In this case, specified gaseous mixtures can be supplied through an upper portion and a side portion of the plasma generation space PS, respectively. Therefore, a gas concentration in the plasma generation space PS can be adjusted, whereby an in-surface uniformity of an etching characteristic can be further improved on the wafer.
Although a flow rate of the branch line is adjusted by a pressure control unit in the preferred embodiment, it is possible to employ a mass flow controller. Further, although thegas supply unit100 described in the preferred embodiment is for supplying the gaseous mixture to theplasma etching apparatus1, the present invention can be applied to another substrate processing apparatus into which a gaseous mixture is supplied, e.g., a film forming apparatus such as a plasma CVD apparatus, a sputtering device and a thermal oxidation apparatus. Further, the present invention can be also applied to an apparatus for processing a substrate other than a wafer, e.g., FPD (flat panel display) and a mask reticle for photomask, and MEMS (Micro Electro Mechanical System) manufacturing apparatus and the like.
While the invention has been shown and described with respect to the preferred embodiment, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.