US20090289035A1 - Plasma Processing Apparatus And Plasma Processing Method - Google Patents

Abstract

A plasma processing apparatus and method which includes a vacuum processing chamber, a plasma generating unit, a process gas supply unit, a specimen table, and a vacuum pumping unit. The specimen table includes an electrostatic arrangement for holding a specimen on a holding surface of the specimen table by electrostatic force, a specimen table cover arranged around the specimen table, and first and second heat transfer gas supply units. The first heat transfer gas supply unit has a main path for supplying a heat transfer gas to the specimen holding surface for cooling the specimen, and the second heat transfer gas supply unit has a branch path branched from the main path of the first heat transfer gas supply unit for supplying a part of the heat transfer gas to a gap between an outer portion of the specimen holding surface and the specimen table cover.

Description

CROSS REFERENCE TO RELATED APPLICATION
• This is a continuation of U.S. application Ser. No. 11/478,629, Jul. 3, 2006, which is a continuation of U.S. application Ser. No. 10/953,537, filed Sep. 30, 2004, now U.S. Pat. No. 7,208,422, which is a continuation of U.S. application Ser. No. 10/617,019, filed Jul. 11, 2003, now abandoned, which relates to U.S. application Ser. No. 10/617,020, filed Jul. 11, 2003, now abandoned which are continuations of U.S. application Ser. No. 09/983,946, filed Oct. 26, 2001, now U.S. Pat. No. 6,815,365, which relates to U.S. application Ser. No. 10/647,319, filed Aug. 26, 2003, now abandoned, which is a continuation of U.S. application Ser. No. 09/984,052, filed Oct. 26, 2001, now abandoned, which relates to U.S. application Ser. No. 10/441,009, filed May 20, 2003, which is a continuation of U.S. application Ser. No. 09/421,044, filed Oct. 20, 1999, now abandoned, which relates to U.S. application Ser. No. 10/253,862, filed Sep. 25, 2002, which is a continuation of U.S. application Ser. No. 09/984,052, filed Oct. 26, 2001, now abandoned, which relates to U.S. application Ser. No. 09/421,044, filed Oct. 20, 1999, now abandoned, which is a continuation of U.S. application Ser. No. 09/983,946, filed Oct. 26, 2001, now U.S. Pat. No. 6,815,365, which relates to U.S. application Ser. No. 09/984,052, filed Oct. 26, 2001, now abandoned, which is a continuation of U.S. application Ser. No. 09/421,043, filed Oct. 20, 1999, which is a continuation of U.S. application Ser. No. 09/227,332, filed Jan. 8, 1999, now U.S. Pat. No. 6,171,438, which is a continuation-in-part of U.S. application Ser. No. 08/611,758, filed Mar. 8, 1996, now U.S. Pat. No. 5,874,012, at least the subject matter of U.S. application Ser. No. 08/611,758 which is U.S. Pat. No. 5,874,012, and U.S. application Ser. No. 10/953,537, which is U.S. Pat. No. 7,208,422, being incorporated by reference herein.
BACKGROUND OF THE INVENTION
• The present invention relates to a plasma processing apparatus and a plasma processing method; and, more particularly, the invention relates to a plasma processing apparatus and a plasma processing method suitable for processing a specimen, such as etching a specimen using a high density plasma.
• In a conventional plasma processing apparatus, as described, for example, in Kanno, T., Semiconductor Plasma Processing Technology, Sangyou-Tosho Company (1980), page 139, using a microwave plasma processing apparatus, which has a quartz discharge chamber in a waveguide transmitting a microwave, plasma is generated in the discharge chamber by action of an outer magnetic field generated by a coil arranged outside of the discharge chamber and a microwave electric field. Thereby, processing, such as etching of a surface of a semiconductor wafer, can be performed using the plasma.
• For a processing chamber in such a microwave etching apparatus, a non-magnetic and conductive material used as the waveguide is necessary to guide the microwave energy and to introduce the outer magnetic field in the processing chamber. Therefore, a metal, such as aluminum (Al) or a stainless steel (SUS), is commonly used for the wall material of the processing chamber.
• However, a metal, such as a stainless steel or the like, composing the wall surface of the processing chamber, becomes worn and dispersed by the plasma, and the heavy weight metals contained in the material become a contamination source.
• A technology is disclosed in Japanese Patent Application Laid-Open No. 4-229619 (1992) where a conductive coating film capable of protecting a metallic surface from chemical corrosion by a reaction gas used in a processing chamber is formed on the metallic inner surface. In accordance with this technology, a protective film is formed on the metallic inner wall surface of the processing chamber through coating, since the metallic inner wall surface may be corroded when plasma etching is performed by using a halogen gas, such as chlorine, as the processing gas. Aluminum is used as the material for the processing chamber, and TiN, InSn, SiC, TiC, TaC or the like is used for the coating material. The thickness of the coating film is 0.2 μm to 1 μm.
• Further, a dry etching apparatus having opposed electrodes inside a chamber is disclosed in Japanese Patent Application Laid-Open No. 63-138737 (1988), wherein the inside surface of the chamber is covered with an insulator material detachable from the chamber in order to keep a contaminated inner surface of the chamber clean. As the insulator material, there is used alumite, alumina thermal spraying, Teflon, ceramic or the like.
• The above conventional technology disclosed in Japanese Patent Application Laid-Open No. 4-229619 (1992) can protect the metallic surface from chemical corrosion due to the reaction gas used in the processing chamber. However, as for the typical condition of the plasma etching process, it is clear that the temperature during plasma processing is limited to a relatively low temperature range of approximately 10° C. to approximately 70° C. The reason why this temperature limitation is set seems to be that cracks may occur in the coating film on the aluminum surface due to the thermal expansion of the aluminum if the temperature of the aluminum composing the process chamber rises above 100° C. during plasma processing. In order to avoid the occurrence of cracks, the thickness of the coating film must be reduced. However, if the thickness of the film is reduced, the coating film cannot perform its function, since it will be corroded out in a short time by the reaction gas generated during plasma etching. For example, data according to an experiment conducted by the inventors, shows that an SiC film is worn off at a speed of approximately 0.05 μm/minute during etching. This means that a coating film having a thickness of 0.2 μm to 1 μm is damaged and eliminated in several hours, that is, during a time when several hundreds of specimens have been processed. As a result, the metallic surface of the inner wall of the process chamber is exposed to the plasma and worn off by the plasma or has its quality altered due to chemical reaction. The worn-off metal becomes a heavy metal contamination source and the quality-altered metallic wall degrades the characteristic of the process chamber.
• On the other hand, in the invention disclosed in Japanese Patent Application Laid-Open No. 63-138737 (1988), a contaminated isolator member is dismounted from a chamber and cleaned, and then re-mounted in the chamber to be used again. However, in a system where an insulator member is mounted onto the inner surface of a chamber, there is a problem in that the plasma processing characteristic largely fluctuates because the temperature of the mounted insulator member fluctuates during plasma processing.
SUMMARY OF THE INVENTION
• An object of the present invention is to provide a plasma processing apparatus and a plasma processing method in which the characteristic of plasma processing is stabilized over time by preventing the inner surface of the process chamber from having its quality altered and from becoming a heavy metal contamination source, and by maintaining the temperature of the inner surface of the process chamber at a given temperature.
• The present invention is characterized by a plasma processing apparatus comprising a plasma generating unit, a process chamber capable of having its inside pressure reduced, a process gas supply unit for supplying a gas to the process chamber, a specimen table for holding a specimen, and a vacuum pumping unit, wherein
• the process chamber comprises an outer cylinder having the capability of withstanding a reduced pressure, an inner cylinder arranged inside the outer cylinder through a gap, and a temperature controlling means for maintaining the temperature of the inner cylinder within a given temperature range.
• The present invention is also characterized by a plasma processing apparatus as described above, wherein the process chamber comprises an outer cylinder having the capability of withstanding a reduced pressure, an inner cylinder arranged inside the outer cylinder through a gap, a temperature controlling means arranged in the outer cylinder, and a heat transmission means for transmitting heat between the outer cylinder and the inner cylinder arranged in the gap.
• Further, the present invention is characterized by a plasma processing method of processing a specimen using a plasma processing apparatus comprising a plasma generating unit, a process chamber capable of having its inside pressure reduced, a process gas supply unit for supplying a gas to the process chamber, a specimen table for holding a specimen, and a vacuum pumping unit, wherein the process chamber comprises an outer cylinder having the capability of withstanding a reduced pressure, an inner cylinder arranged inside the outer cylinder through a gap, a temperature controlling means arranged in the outer cylinder, and a heat transmission means for transmitting heat between the outer cylinder and the inner cylinder arranged in the gap, and wherein plasma processing is performed on the specimen while the temperature of the inner cylinder is being kept within a given temperature range.
• Still further, the present invention is characterized by a plasma processing method as described above, wherein the inner cylinder is made of a non-magnetic material not containing heavy metals, or is made of a material selected from a group of ceramic, carbon, silicon, quartz and metal materials, and plasma processing is performed on said specimen while the temperature of said inner cylinder is being kept within a given temperature range.
• According to the present invention, since the inner cylinder used as the inner wall of the process chamber, which is made of a material not containing heavy metals, such as a ceramic, a metallic surface such as aluminum composing the outer cylinder is not exposed during the processing of a wafer.
• Therefore, the wall never becomes a heavy metal contamination source by being worn or changed in quality by the plasma. On the other hand, since the thermal conductivity of the inner cylinder is lower than that of the outer cylinder, the temperature of the inner cylinder, that is, the surface temperature of the process chamber, may be raised up to 200° C. to 350° C. during etching process if the temperature is not controlled. In accordance with the present invention, since the temperature of the inner cylinder is controlled to a desired temperature, for example, a desired temperature between 100° C. to 350° C., the surface temperature of the process chamber can be kept to a desired temperature and the etching characteristic is also kept stable.
• Further, it is also possible to stabilize the process by controlling the surface temperature of the inner cylinder in a desired pattern.
• Furthermore, in a case of employing such a material composing the cylinder that the inner side surface of the material is worn bit by bit by plasma, since the inside surface of the inner cylinder is always renewed to a new surface, there is no worry about contamination due to a change in quality of the inside surface, and accordingly there is no time-change in the characteristic of the process chamber. In addition to this, since the inner cylinder does not contain any heavy metals, there is no worry that the inner cylinder becomes a contamination source even if it is worn.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a partial cross-sectional vertical front view showing an embodiment of a microwave plasma processing apparatus in accordance with the present invention.
• FIG. 2 is an enlarged view showing the main part of the temperature controller for the inner cylinder shown inFIG. 1.
• FIG. 3 is a graph showing the function of the temperature controller ofFIG. 1.
• FIG. 4 is a graph showing the relationship between gap pressure P and temperature difference in the temperature control.
• FIG. 5 is a vertical cross-sectional view showing a second embodiment of a microwave plasma processing apparatus in accordance with the present invention.
• FIG. 6 is a transverse cross-sectional view showing the main part of the plasma processing apparatus ofFIG. 5.
• FIG. 7 is a vertical cross-sectional view showing a third embodiment of a parallel plate plasma etching apparatus in accordance with the present invention.
• FIG. 8 is a cross-sectional view showing an example of a magnetron RIE apparatus to which the present invention is applied.
• FIG. 9 is a cross-sectional view showing an example of a plasma processing apparatus to which the present invention is applied, the plasma processing apparatus being of an external energy supplying discharge type, and particularly of an induction coupling discharge type and a non-magnetic field type.
• FIG. 10 is a cross-sectional view showing an example of a plasma processing apparatus to which the present invention is applied, the plasma processing apparatus being of an external energy supplying discharge type, and particularly of an induction coupling discharge type and a magnetic field type.
• FIG. 11 is a cross-sectional view showing an example of a plasma processing apparatus to which the present invention is applied, the plasma processing apparatus being of an external energy supplying discharge type, and particularly of an induction coupling discharge type and a magnetic field type.
• FIG. 12 is a vertical cross-sectional view showing an example of a sample to be processed with an apparatus in accordance of the present invention, the sample being a resist attached oxide film.
• FIG. 13 is a graph showing the relationship between a number of processed wafers and the temperature of the inner cylinder.
• FIG. 14 is a cross-sectional view showing an embodiment of a sample table cover portion of a plasma processing apparatus to which the present invention is applied.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Embodiments of the present invention will be described in detail below, referring to the accompanying drawings.
• FIG. 1 is a partial cross-sectional vertical front view showing an embodiment of a microwave plasma processing apparatus in accordance with the present invention, andFIG. 2 is an enlarged view showing the main part of the apparatus. Thereference character1 designates a magnetron operating as a microwave oscillator source, and thereference character2 designates a guide tube for microwave energy. Thereference character3 designates a quartz plate for permitting the supply of microwave energy to aprocess chamber4 while vacuum sealing theprocess chamber4. Theprocess chamber4 is composed of anouter cylinder5 made of, for example, high purity aluminum (Al) and is capable of withstanding depressurization, and aninner cylinder6 arranged inside the outer cylinder and made of ceramic, such as silicon carbide (SIC) or the like. Since the inside surface of the process chamber is formed of an insulator and the outer side is formed of a conductor, theprocess chamber4 also serves as a waveguide. The reference character7 designates a first solenoid coil for supplying a magnetic field, and the reference character8 (8A,8B) designates a second solenoid coil. Theprocess chamber4 is evacuated to vacuum by a vacuum pump connected to a vacuum chamber9. Thereference character10 designates a sample table for mounting awafer11 to be processed, for example, to be etched, and connected to a highfrequency power source12. Thereference character13 designates a process gas supplying system which supplies a process gas for performing processing, such as etching, film forming or the like, into theprocess chamber4.
• There is a gap G14 having an interval of nearly 0.1 to 2 mm between theinner cylinder6 and theouter cylinder5, and a heat transfer gas for temperature control is introduced into the gap through agas supply system15. Thegas supply system15 has agas source16, apressure control valve17, apressure detector18, a pressure command instruction means19 and acontroller20. The pressure P between thegap14 is detected by thepressure detector18 and the opening of thepressure control valve17 is controlled so as to keep the pressure P at a desired value.
• Theinner cylinder6 is supported by asupporter32. In order to replace the inner cylinder when its surface is worn a certain amount, the inner cylinder is detachably supported by the outer cylinder.
• Aheater21 for heating theprocess chamber4 is arranged around theouter cylinder5, and the temperature T of theinner cylinder6 is detected by atemperature detector23. Acontroller22 controls the temperature of theouter cylinder5 to a temperature T₀. Theheater21 works to maintain the temperature T of theinner cylinder6 by keeping the temperature T₀of theouter cylinder5 and the pressure of the gap at preset values.
• During plasma processing, the pressure of theprocess chamber4 is adjusted to a preset process pressure by introducing a process gas into theprocess chamber4 from thegas supply system13 at a given flow rate while vacuum evacuating the chamber using the vacuum pump. Further, the temperature T₀of theouter cylinder5, the temperature T of theinner cylinder6 and the pressure P of thegap14 are controlled by theheater21, thegas supply system15 and thetemperature controller22.
• Awafer11 to be processed is mounted so as to be held on the sample table10. Themagnetron1 and the first and the second coils7,8 are switched on, so that a microwave is guided to theprocess chamber4, and thenplasma100 is generated in theprocess chamber4 to etch thewafer11.
• According to the present invention, since no metallic surface, such as aluminum, forms an exposed inside wall of theprocess chamber4, there is no possibility that a metal part will become worn and varied in quality, and so the wall cannot become a heavy metal contamination source to thewafer11.
• On the other hand, the SiC inner surface of theinner cylinder6 is worn byplasma100 bit by bit. However, since the SiC cylinder does not contains any heavy metal, there is no worry that the cylinder becomes a contamination source even if it is worn. On the contrary, since the inner surface of the inner cylinder is always renewed to a new surface as it is being worn, there is no worry about contamination due to varying the quality of the inside surface, and accordingly the characteristic of theprocess chamber4 hardly varies with time. The worn SiC component is exhausted from theprocess chamber4 by the vacuum pump.
• The temperature of the inner cylinder is increased by heat generated in the process chamber during the etching process. If it is not controlled, the temperature T of the inner cylinder will reach up to 200° C. to 350° C. or higher. On the other hand, the etching characteristic in a plasma etching process is strongly affected by the temperature of the inside surface. In other words, since reaction between theinner cylinder6 and the etching gas varies depending on the change in the surface temperature of theinner cylinder6 and causes fluctuation in etching gas environment, the etching characteristic is not stabilized. For example, since the temperature change of theinner surface6 causes the component, to fluctuate and the amount of accumulated materials on the wall and the change in the reaction speed with the wall causes the component in the plasma to fluctuate, the etching characteristic is not stabilized.
• In accordance with the present invention, the surface temperature T of the inner cylinder is controlled to a desired value in the range of 100° C. to 350° C., preferably 150° C. to 300° C., by controlling the temperature T₀of theouter cylinder5 using theheater21 and the pressure P in thegap14. According to the present invention, since the surface temperature T of theinner cylinder6 is kept at a preset value, the etching characteristic becomes stable. Further, since the surface temperature T of theinner cylinder6 is kept at a preset value and the etching speed to the inside surface of theinner cylinder6 is stabilized, the wearing rate of the surface of theinner cylinder6, which is worn by the plasma, also becomes constant. Thereby, the characteristic of theprocess chamber4 becomes stable.
• FIG. 3 shows the function for controlling the temperature of theinner cylinder6 as carried out by thetemperature controller22. As an example, the figure shows a case where the temperature T of theinner cylinder6 is caused to approach T₀by keeping the temperature of theouter cylinder5 at T₀.
• In this case, as shown inFIG. 4, the temperature difference between T and T₀can be decreased by increasing the pressure P in thegap14. In more detail, in a case where the distance of thegap14 is 1 mm, He gas is supplied to thegap14 and the gas pressure is controlled to 10 Torr; and, when the heat input to theinner cylinder6 is 0 to 300 W, the temperature of theinner cylinder6 can be kept in 150° C.±20° C. for an outer cylinder temperature of 150° C.
• An optimum temperature for the inner cylinder differs depending on a combination of factors, including the kind of inner cylinder, the film quality to be processed, the kind of process gas being used, the discharge condition and so on.
• In a case where, for example, a resist attached oxide film sample as shown inFIG. 12 is processed by using a CF family gas as the process gas and quartz as the material for the inner cylinder, when the temperature of the inner cylinder is not controlled, the temperature of the inner cylinder gradually increases as it receives heat from the plasma and eventually levels off to a certain temperature as the number of processed samples is increased, as shown inFIG. 13. Therein, although the change in the etching speed of the oxide film is small, the etching speed of the resist gradually decreases as the temperature of the inner cylinder increases and then the etching speed of the resist is stabilized when the temperature of the inner cylinder becomes saturated.
• On the other hand, by maintaining the temperature of the inner cylinder at the saturating temperature ofFIG. 13 in advance, a stable etching speed for the resist can be obtained from the first sheet of the processed samples.
• In a case where the temperature of the inner cylinder is continuously being kept at an initial temperature, not at the saturating temperature shown inFIG. 13, the etching speed for the first sheet of the processed samples can be obtained.
• The heat transfer capability of the gap is higher when thegap14 is narrower, but the effect needed for the required temperature control can be achieved up to a gap of 2 mm.
• The material of theinner cylinder6 in this embodiment needs to be a non-magnetic material because of the microwave discharge using a magnetic field, and it should have the property that its quality will not be varied by plasma and it should not contain any heavy metals. As materials satisfying these conditions, there are carbon (C), silicon (Si), quartz (SiO), alumina (Al₂O₃) and so on. However, aluminum may be employed depending on the content of the plasma processing.
• Theinner cylinder6 is required to have a mechanical strength above a certain value and durability. That is, the SiC cylinder forming theinner cylinder6 in the embodiment must have sufficient a thickness to have a mechanical strength capable of withstanding an outer force acting during plasma processing, and it has to have a durability capable of withstanding a large amount of wafer processing while it is worn by plasma.
• On the presumption that the SiC wall is worn at the rate of approximately 0.05 μm every minute by etching and the practical number of wafers processed by one inner cylinder is several ten thousands, an Sic wall thickness of 2 to 10 mm is sufficient.
• In the embodiment shown inFIG. 1, it is preferable on the surface temperature of thequartz plate3 to be also controlled to 100° C. to 350° C. in the same manner as the temperature control of theinner cylinder6.
• FIG. 5 is a vertical cross-sectional view showing another embodiment of a microwave plasma processing apparatus in accordance with the present invention. Theprocess chamber4 is constructed with anouter cylinder5 formed of a highly pure aluminum and aninner cylinder6 formed of a ceramic and arranged within the outer cylinder. The inside surface of theprocess chamber4 is reversely taper shaped, and theinner cylinder6 is truncated cone shaped. There is agap14 between theouter cylinder5 and theinner cylinder6. In thegap14, acorrugated plate30 made of aluminum is arranged, and thecorrugated plate30 contacts theouter cylinder5 and theinner cylinder6 with a spring force, as seen inFIG. 6. Aheater21 for heating is arranged around the periphery of theouter cylinder5. The lower portion of theinner cylinder6 is supported on asupport member32 through aspring31. There is also aspring33 in the upper portion of theinner cylinder6. The contact force between theouter cylinder5 and theinner cylinder6 is increased by thesesprings31,33 and thecorrugated plate30. Thesprings31,33 also have a function to absorb any difference of thermal expansion between theouter cylinder5 and theinner cylinder6.
• In this embodiment, the function of theinner cylinder6 formed of SiC is the same as that in the previous embodiment. This embodiment is characterized by the fact that heat transmission between theouter cylinder5 and theinner cylinder6 is performed by a combination of contact heat transmission by thecorrugated plate31 and gas heat transmission by the gas inside thegap14. According to the embodiment, the etching characteristic can be stabilized since thesurface temperature52 of the process chamber, that is, the temperature of theinner cylinder6, can be kept at a temperature close to the temperature T₀of theouter cylinder5.
• In the embodiments inFIG. 1 toFIG. 5, the temperature of theinner cylinder6 may be detected indirectly, if it cannot be detected directly. However, the following effects can be obtained by attaching atemperature detector23 to theinner cylinder6.
• (1) By making the pressure in thegap14 variable or by finely adjusting the temperature of theouter cylinder5 in order to control the temperature of theinner cylinder6 more accurately, controllability of the inner cylinder temperature can be improved.
• (2) By monitoring the temperature of theinner cylinder6, it is possible to output an alarm signal, such as to indicate the need for stopping plasma processing or to quit plasma processing when the temperature of theinner cylinder6 exceeds a preset range.
• In the embodiments inFIG. 1 toFIG. 5, a heater is used as the temperature control function for the outer cylinder. However, by recirculating a temperature controlled liquid to the outer cylinder, it is possible to widen the temperature control range from a cooled state below room temperature to a heated state, and accordingly controllability of the inner cylinder temperature can be improved in this way.
• FIG. 7 shows another embodiment of a parallel plate plasma etching apparatus to which the present invention is applied. This apparatus has a vacuum chamber serving as aprocess chamber4, which is a substantially closedmetallic reaction chamber40 constructed by an upper plate41, aside wall42 forming an outer cylinder and abottom plate43. In the vacuum chamber there is provided a pair of parallel plate electrodes facing each other, the anode41 being grounded to the inside wall of thechamber40 and thecathode47 being mounted on thechamber40 through aninsulator46, and there is also provided a highfrequency power source48 for supplying high frequency energy to thecathode47. Further, there are provided a vacuumpump connecting part44 for partially evacuating theprocess chamber4 and a reaction gas supply source for supplying a reaction gas to theprocess chamber4 through a valve controlledpipe45. Awafer11 to be etched is mounted on thecathode47.
• Aninner cylinder49 made of SiC is formed on the inside surface of thechamber40, that is, on the upper plate41, theside wall42 and thebottom plate43. There is agap50 between theside wall42 and theinner cylinder49, and a heat transfer gas for temperature control is introduced in the gap from a gas supply system. The gas supply system has a gas source, a pressure control valve, a pressure detector, a pressure command instruction means and a controller, and operates so as to maintain the pressure P in thegap50 at a preset value, in the same manner as in the embodiment ofFIG. 1. Aheater51 for heating theprocess chamber4 is arranged around the outer periphery of thechamber40, and the temperature T₀of theside wall42 is controlled by a temperature controller through theheater51 and the temperature T of theinner cylinder49 can be kept to a desired value, as described in the embodiment ofFIG. 1. Atemperature detector23 may be attached to theinner cylinder49.
• With such a construction, by maintaining the temperature of theinner cylinder49 at a preset value during plasma etching, it is possible to obtain the effect that the metal is not worn nor is its quality varied by the plasma in the same manner as in the embodiments described above. Further, since the inside surface of theinner cylinder49 is always renewed to a new surface, there is no worry about contamination due to variation in the quality of the inside surface. Furthermore, since the temperature of theinner cylinder49 is maintained at a preset value, it is possible to carry out a stable plasma processing. Herein, in the case of a parallel plate type etching apparatus, it is not necessary to limit the material of the inner cylinder to a non-magnetic material.
• The present invention can be applied to other apparatuses having different plasma generating mechanisms. Examples of such applications are shown inFIG. 8 toFIG. 11.
• FIG. 8 shows an example of a magnetron RIE apparatus having amagnetron80 to which the present invention is applied. Aprocess chamber4 of a vacuum chamber has aside wall42, a sample table10 for mounting awafer11 and a highfrequency power source48 for supplying high frequency energy to the electrode of the sample table10. Further, there are a connection part to a vacuum pump for partially evacuating theprocess chamber4 and a reaction gas supply source for supplying a reaction gas to theprocess chamber4 through a valve controlledpipe13.
• Aninner cylinder49 made of SiC is disposed inside of thechamber4 adjacent the surface of theside wall42. There is a gap between theside wall42 and theinner cylinder49, and a heat transfer gas for temperature control is introduced in the gap from agas supply system15. The gas supply system has a gas source, a pressure control valve, a pressure detector, a pressure command instruction means and a controller, and operates so as to maintain the pressure P in thegap50 at a preset value, in the same manner as in the embodiment ofFIG. 1. Aheater51 for heating theprocess chamber4 is arranged around the outer periphery of theside wall42, the temperature T₀of theside wall42 being controlled by atemperature controller22 through theheater51 so that the temperature T of theinner cylinder49 can be kept to a desired value, as described in the embodiment ofFIG. 1.
• With such a construction, by maintaining the temperature of theinner cylinder49 at a preset value during plasma etching, it is possible to perform a stable plasma processing in the same manner as described in the above embodiment. Further, it is possible to obtain the effect that the metal is not worn nor varied in quality by the plasma. Further, since the inside surface of theinner cylinder49 is always renewed to a new surface, there is no worry about contamination due to variation in the quality of the inside surface.
• FIG. 9 shows an example of a plasma processing apparatus to which the present invention is applied, the plasma processing apparatus being of an external energy supplying discharge type, and particularly of an induction coupling discharge type and a non-magnetic field type. Aprocess chamber4 is formed by asilicon plate90 and aquartz chamber92. Thereference character91 denotes a heated antenna member and thereference character95 designates an upper heater. In this embodiment, by maintaining the temperature of thequartz chamber92 at a preset value during plasma etching, it is possible to perform a stable plasma processing by the same action described in the above embodiment. Further, it is possible to obtain the effect that the metal is not worn nor varied in quality by the plasma. Further, since the inside surface of thequartz chamber92 is always renewed to a new surface, there is no worry about contamination due to variation in the quality of the inside surface.
• FIG. 10 shows an example of a plasma processing apparatus to which the present invention is applied, the plasma processing apparatus being of an external energy supplying discharge type, and particularly of an induction coupling discharge type and a magnetic field type. Thereference character105 denotes a bell jar and thereference character110 designates an antenna. Aprocess chamber4 of a vacuum chamber has aninner cylinder112, anouter cylinder114, a sample table10 for mounting awafer11 and a highfrequency power source48 for supplying high frequency energy to the electrode of the sample table10. Further, there are a connection part to a vacuum pump for partially evacuating theprocess chamber4 and a reaction gas supply source for supplying a reaction gas to theprocess chamber4 through a valve controlled pipe. Furthermore, there are provided aheater116 and acooling water passage120 for performing temperature control by heating and cooling theouter cylinder114.
• There is a gap between theinner cylinder112 made of SiC and theouter cylinder114, and a heat transfer gas for temperature control is introduced in the gap from agas supply system15. The gas supply system has a gas source, a pressure control valve, a pressure detector, a pressure command instruction means and a controller, and operates so as to maintain the pressure P in the gap at a preset value. The temperature T₀of theouter cylinder114 is controlled by a temperature controller through theheater116 and the temperature T of theinner cylinder112 can be kept to a desired value.
• With such a construction, by maintaining the temperature of theinner cylinder112 at a preset value during plasma etching, it is possible to perform a stable plasma processing by the same action described in the above embodiment. Further, it is possible to obtain the effect that the metal is not worn nor varied in quality by the plasma. Further, since the inside surface of theinner cylinder49 is always renewed to a new surface, there is no worry about contamination due to variation in the quality of the inside surface.
• FIG. 11 shows an example of a plasma processing apparatus to which the present invention is applied, the plasma processing apparatus being of an external energy supplying discharge type, and particularly of an induction coupling discharge type and a magnetic field type. Thereference character120 denotes an electrode and thereference character48 designates a high frequency power source. Aprocess chamber4 of a vacuum chamber has aceramic plate124, aninner cylinder122, and a sample table10 for mounting awafer11. Further, there are provided a heater166 and agas flow passage130 for supplying a gas to the gap to perform temperature control by heating and cooling theceramic plate124. A gas supply system has a gas source, a pressure control valve, a pressure detector, a pressure command instruction means and a controller, and operates so as to maintain the pressure P in the gap at a preset value. The temperature T₀of theceramic plate124 is controlled by a temperature controller through theheater126 and the temperature T of theinner cylinder122 can be kept to a desired value.
• With such a construction, by maintaining the temperature of theinner cylinder122 at a preset value, it is possible to perform a stable plasma processing by the same action described in the above embodiment. Further, it is possible to obtain the effect that the metal is not worn nor varied in quality by the plasma. Further, since the inside surface of the inner cylinder is always renewed to a new surface, there is no worry about contamination due to variation in the quality of the inside surface.
• In each of the embodiments described inFIG. 8 toFIG. 11, it is preferable that a non-magnetic and non-metallic material be used for the material of the inner cylinder in order to decrease the effects of the magnetic field and the electric field.
• The present invention can be applied not only to a plasma etching apparatus but also to a CVD apparatus or a spattering apparatus.
• Further, application of the present invention is not limited to the case where a process is stabilized by maintaining the temperature of the inner cylinder to a preset value. The present invention can be also applied to, for example, a case where an initial process change for a lot is corrected by intentionally changing the temperature of the inner cylinder at the initial stage of the lot. That is, it is possible to stabilize a process by improving the temperature controllability for the inner cylinder.
• The apparatuses described inFIG. 1 toFIG. 11 are used as follows.
• Before starting operation of the apparatus, it is checked to determine whether or not the temperature of the inner cylinder can be controlled to a desired temperature.
• Firstly, the inside of theprocess chamber4 is evacuated to a preset pressure by action of the vacuum pump. Then, the heater is operated. The inner cylinder is heated by heat generation of the heater. During this period, a heat transfer gas is supplied to the gap and the gas pressure in the gap is adjusted to a preset pressure. That is, heating of the inner cylinder is performed by utilizing heat transfer of the heat transfer gas supplied to the gap. The temperature of the heated inner cylinder is directly or indirectly detected and controlled to a desired temperature. By doing so, it can be confirmed that the temperature of the inner cylinder can be controlled to the desired temperature. If the temperature of the inner cylinder cannot be controlled to the desired temperature, operation of the heater is stopped and supply of the heat transfer gas to the gap is stopped. Then, the cause of the trouble is checked and repaired.
• In the above case, one wafer is introduced into the process chamber using a transfer machine which is not shown in the figures. The introduced wafer is transferred from the transfer machine to the sample table and mounted on a sample mounting surface so that the surface opposite to the surface to be processed is facing the sample mounting surface. In the apparatuses described with reference toFIG. 1 toFIG. 11, a temperature control means having a cooling function is provided at the sample table. In a CVD apparatus or a spattering apparatus which requires to heat a wafer during processing, a temperature control means having a heating function is provided at the sample table. The wafer mounted on the sample mounting surface of the sample table is held on the sample table by a mechanical clamping means utilizing a spring force or gravitational force, an electrostatic attracting means, a vacuum sucking means or the like.
• Then, a process gas is introduced into the process chamber with a preset flow rate. A part of the process gas introduced in the process chamber is exhausted out of the process chamber by the operating vacuum pump. By doing so, the pressure inside the process chamber is adjusted to a processing pressure of the wafer.
• Under such a condition, the process gas in the process chamber is changed to a plasma by discharge. The surface of the wafer mounted on the sample table is processed by plasma. During processing, the temperature of the wafer is controlled at a preset temperature.
• During processing, the temperature of the inner cylinder is monitored continuously or when required. The monitored temperature is compared with a preset desired temperature, and the temperature of the inner cylinder is controlled to the desired temperature based on the result of the comparison. The temperature control of the inner cylinder is performed by adjusting the pressure of the heat transfer gas in the gap between the inner cylinder and the outer cylinder or by adjusting the temperature of the outer cylinder by adjusting the heat being generated by the heater. The pressure adjusting of the heat transfer gas in the gap between the inner cylinder and the outer cylinder is performed by adjusting the supply flow rate or the pressure of the heat transfer gas supplied to the gap.
• In general, plural wafers are continuously processed one by one. In such a case, the temperature of the inner cylinder is monitored while processing one wafer among them until processing for the all plural wafers is completed to control the temperature to the desired temperature. For example, when trouble occurs in the temperature monitoring of the inner cylinder or when the temperature of the inner cylinder cannot be controlled to the desired temperature, it is judged that the processing characteristic of the wafer cannot be maintained stable and the wafer processing is stopped. Then, an effort is made to solve the problem, and the successive process for plural wafers is re-started.
• The fact that trouble occurs in the temperature monitoring of the inner cylinder or that the temperature of the inner cylinder cannot be controlled to the desired temperature is indicated to an operator by output of some kind of alarm through the controller. In response to the alarm, the operator solves the trouble and re-starts the wafer processing. By monitoring the temperature control of the inner cylinder, the history of the processing up until the stopping of the wafer processing can be checked, and consequently the search of the cause and the repairing method can be performed properly and fast.
• A cleaning process is performed for the inside of the process chamber. The process is performed by wiping the inside surface of the process chamber, such as the surface of the inner cylinder, and the surfaces of parts arranged inside the process chamber, such as the sample table, or by utilizing a cleaning gas plasma. The process is performed before a wafer processing, in the intervals between processings, or after completion of a wafer processing.
• In a case of performing a cleaning process by wiping, it is checked whether the temperature of the inner cylinder can be controlled during a period after completion of the cleaning processing and before the starting of a wafer processing. On the other hand, in a case of performing a cleaning process by utilizing a plasma, it is checked whether the temperature of the inner cylinder can be controlled during the cleaning processing or during a period after the cleaning process and before starting of a wafer processing.
• Further, a discharge running-in (seasoning) process is performed for the inside of the process chamber. The seasoning process is performed before starting a wafer processing at the beginning of a day, or during a period after completion of a cleaning processing and before starting of a wafer processing. In this case, it may be checked during the seasoning process whether the temperature of the inner cylinder can be controlled or not.
• In order to stabilize the characteristic of plasma processing over time, it is necessary to control the temperature of the inner cylinder to a temperature corresponding to a wafer processing condition. Here, the wafer processing conditions include the quality of film to be processed, the kind of processing gas to be used, the condition of discharge, the type of discharge and so on.
• Therefore, wafer processing conditions are input to the controller of the processing apparatus from a higher level controlling unit or an operator. The controller has received an indication of the temperature of the inner cylinder corresponding to each of the wafer processing conditions. In the controller, the temperature of the inner cylinder corresponding to the input wafer processing condition is selected and set as a control temperature. On the other hand, a detected and monitored temperature of the inner cylinder is input to the controller. The detected and monitored temperatures are compared with the control temperature, and the temperature of the inner cylinder is controlled to the control temperature based on the result of comparison.
• Further, in a case where the wafer is, for example, of a multi-layer film structure, the temperature of the inner cylinder may be controlled to a temperature corresponding to that set for the quality of each film, the kind of process gas, the condition of discharge and so on. By doing so, the characteristic of plasma processing can be finely stabilized over time.
• In a case where a wafer processing performance is varied during one lot processing after a running-in discharge (seasoning) process, the temperature of the inner cylinder may be varied along a desired temperature pattern in order to make the processing performance uniform.
• Although the above description has been directed to the temperature control of the inner cylinder inside the chamber, the present invention can be similarly applied to the temperature control of the sample table cover arranged around the sample table.
• FIG. 14 is a cross-sectional view showing an embodiment of a sample table cover portion of a plasma processing apparatus to which the present invention is applied. A liquid for temperature control is recirculated inside a sample table10, so that an insulator applied onto the surface of the sample table will be maintained at a desired temperature, and asample11 is attracted to the sample table10 by an electrostatic force using an directcurrent power source54 for providing an electrostatic chuck under a condition wherein a discharge exists in the processing chamber. A heat transfer gas, for example, helium gas is introduced between thesample11 and the sample table10 in order to increase the thermal conductance. A sample table cover made of an insulator, such as alumina or the like, or a resistive material, such as SiC or the like, is arranged in the upper portion of the sample table10 to prevent discharge of undesired metals when the metallic sample table10 is exposed to a plasma. The temperature of the sample table cover is raised as ions and radicals in the plasma collide with the surface of thesample table cover50. When the temperature of thesample table cover50 near the sample is varied, there is a disadvantage in that chemical-physical reaction is varied, and consequently the processing characteristic of the sample is varied. Therefore, a gas sealing means55, for example, an O-ring, is provided between the sample table10 and thesample table cover50, and a heat transfer gas is introduced between the sample table10 and thesample table cover50. The pressure control and its related system are the same as in the case of the inner cylinder. Although the heat transfer gas for cooling a sample is also used for the heat transfer gas for cooling the sample table cover inFIG. 14, needless to say, the gas may be separately supplied.
• According to the present invention, the temperature of the inner cylinder which directly contacts the plasma can be controlled, and the change in the characteristic of the plasma processing can be controlled over time.
• Further, according to the present invention, it is possible to provide a plasma processing apparatus and a plasma processing method having a stable plasma processing characteristic which can avoid heavy metal contamination caused by use of a non-magnetic and conductive metallic material to form the process chamber, which is subjected to being worn and having its quality varied by plasma, and under a condition that the wall surface of the process chamber is not chemically corroded by the reaction gas used inside the process chamber.

Claims (5)

1. A plasma processing apparatus including a vacuum processing chamber, a plasma generating unit for generating a plasma in the vacuum processing chamber, a process gas supply unit for supplying gas to the vacuum process chamber, a metallic specimen table having a specimen holding surface for holding a specimen to be processed, and a vacuum pumping unit for evacuating the vacuum processing chamber;

wherein the metallic specimen table comprises:

electrostatic means for holding the specimen on a holding surface of the metallic specimen table by electrostatic force;

a specimen table cover insulator arranged in an upper portion of the metallic specimen table on an outer portion of the specimen holding surface so as to cover at least a part of an upper surface of the metallic specimen table disposed at a position facing and below the specimen for preventing discharge of undesired metals when the metallic specimen table is exposed to the plasma;

a first heat transfer gas supply unit having a main path inside of the metallic specimen table for supplying a heat transfer gas between the specimen holding surface and the specimen for cooling the specimen; and

a second heat transfer gas supply unit having a branch path formed inside of the metallic specimen table and branched from the main path inside of the metallic specimen table of the first heat transfer gas supply unit for supplying a part of the heat transfer gas from the main path directly to a closed gap between an outer portion of the upper surface of the specimen holding surface and the specimen table cover.

2. The plasma processing apparatus according toclaim 1, comprising a gas sealing unit arranged between the upper portion of the outer portion of the specimen holding surface and the specimen table cover which covers at least the part of the upper surface of the metallic sample table disposed at the position facing and below the specimen so as to form the closed gap.

3. A plasma processing method for processing a specimen by a plasma processing apparatus including a vacuum process chamber, a plasma generating unit for generating a plasma in the vacuum processing chamber, a process gas supply unit for supplying gas to the vacuum process chamber, a metallic specimen table including a specimen holding surface for holding a specimen to be processed, an electrostatic means for holding the specimen on the holding surface, and a specimen table cover arranged in an upper portion of the metallic specimen table on an outer portion of the specimen holding surface so as to cover at least a part of an upper surface of the metallic specimen table disposed at a position facing and below the specimen;

wherein the processing method comprises the steps of:

holding the specimen on the holding surface of the metallic specimen table by an electrostatic force generated by the electrostatic means;

supplying a heat transfer gas between the specimen holding surface and the specimen for cooling the specimen through a main path inside of the metallic specimen table of a first heat transfer gas supply unit; and

supplying a part of the heat transfer gas from the main path directly to a closed gap between the outer portion of the specimen holding surface and the specimen table cover through a branch path inside of the metallic specimen table of a second heat transfer gas supply unit and branched from the main path inside of the metallic specimen table of the first heat transfer gas supply unit;

whereby temperature fluctuation of the specimen table cover during processing of the specimen is restrained and discharge of undesired metals is prevented when the metallic specimen table is exposed to the plasma.

4. The plasma processing apparatus according toclaim 1, wherein the specimen table cover covers a portion of a sidewall surface of the metallic specimen table so as to delimit a portion of the closed gap thereat.

5. The plasma processing apparatus according toclaim 3, wherein the specimen table cover covers a portion of a sidewall surface of the metallic specimen table so as to delimit a portion of the closed gaps thereat.

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