US20090236043A1 - Plasma processing apparatus - Google Patents

Abstract

A plasma processing apparatus includes a processing gas supplying unit for supplying a desired processing gas to a processing space between an upper electrode and a lower electrode which are disposed facing each other in an evacuable processing chamber. The plasma processing apparatus further includes a radio frequency (RF) power supply unit for applying an RF power to one of the lower and the upper electrode to generate plasma of the processing gas by RF discharge and an electrically conductive RF ground member which covers a periphery portion of the electrode to which the RF power is applied to receive RF power emitted outwardly in radial directions from the periphery portion of the electrode to which the RF power is applied and send the received RF power to a ground line.

Description

FIELD OF THE INVENTION
• The present invention relates to a technique for performing a plasma processing on a substrate to be processed, and more particularly, to a capacitively coupled plasma processing apparatus.
BACKGROUND OF THE INVENTION
• In a manufacturing process of a semiconductor device or an FPD (flat panel display), a plasma is often used in the process, e.g., etching, deposition, oxidation, sputtering or the like, in order to allow a processing gas to react efficiently at a relatively low temperature. Conventionally, a capacitively coupled plasma processing apparatus is mainly used to easily realize a plasma having a large diameter for a single-wafer plasma processing apparatus.
• In general, in a capacitively coupled plasma processing apparatus, an upper electrode and a lower electrode are disposed in parallel with each other in a vacuum processing chamber, and a target substrate (e.g., a semiconductor wafer, a glass substrate or the like) is mounted on the lower electrode, while a radio frequency (RF) power is applied between both electrodes. Then, electrons accelerated by an RF electric field formed between the electrodes, electrons emitted from the electrodes, or heated electrons collide with molecules of a processing gas to ionize them to thereby generate plasma of the processing gas, and accordingly, a desired microprocessing, e.g., etching, is performed on a substrate surface by radicals and ions in the plasma.
• Here, the electrode to which the RF power is applied serves as a cathode (negative pole) that is connected to an RF power supply via a blocking capacitor in a matching unit. A cathode coupling type in which an RF power is applied to the lower electrode which mounts thereon a substrate and serves as a cathode can perform a well directed anisotropic etching by substantially vertically attracting ions in the plasma toward the substrate by using a self-bias voltage generated in the lower electrode.
• Along with the recent trend for miniaturization of a design rule in manufacturing a semiconductor device or the like, an ever increasingly high dimensional accuracy is required especially in the plasma etching and, hence, selectivity against an etching mask and an underlying layer and/or in-plane uniformity in the etching has to be improved. Accordingly, there arises a demand for lowering ion energy as well as pressure in a processing region inside the chamber. For that reason, an RF power of about 40 MHz or greater has been applied, which is significantly higher than that applied in a conventional case.
• Here, it becomes difficult to make a plasma of a uniform density in a processing space of the chamber (particularly in a radial direction). In other words, when the frequency of the RF power for plasma generation is increased, the plasma density becomes non-uniform by having a mountain-shaped profile in which the plasma density is maximized mostly above a central portion of a substrate and is minimized mostly above an edge portion of the substrate by a wavelength effect by which a standing wave is produced in the chamber and/or a skin effect by which the RF power is concentrated on a central portion of an electrode surface. If the plasma density is non-uniform above the substrate, a plasma process also becomes non-uniform, which leads to a reduced production yield of devices.
• Various studies on electrode structures have been made to overcome such a problem. For example, Japanese Patent Laid-open Application No. 2004-363552 (Corresponding to U.S. Patent Application Publication No. 2005/0276928 A1) discloses a plasma processing apparatus in which a dielectric material is embedded at a main surface of an electrode facing a processing space and impedance of the RF power emitted from the electrode main surface to the processing space is made to be relatively large at a central portion of the electrode and relatively small at an edge portion of the electrode, thereby improving uniformity of a plasma density distribution.
• At a certain frequency range, the method of embedding the dielectric material at the electrode main surface as described above can be employed to effectively transform, to a flat (uniform) profile, a mountain-like profile of the plasma density distribution on a subject substrate, which has its peak at the central portion of the substrate and becomes gradually getting low toward an edge portion of the substrate. However, if a frequency of the employed RF power is increased further, variation of the plasma density distribution (altitude difference in the mountain-like distribution) becomes larger in proportion to the increased frequency, thereby making it difficult to flattening the plasma density distribution. In addition, a cathode-coupled plasma processing apparatus is disadvantageous in that, if a frequency of the RF power exceeds about 80 MHz, a plasma density distribution produced by an RF power of a certain power level becomes to have a W-like profile in which the plasma density is high above the central portion and the edge portion of a substrate and low above the portion therebetween. Such a W-like profile cannot be dealt with the method of flattening the mountain-like profile.
SUMMARY OF THE INVENTION
• In view of the above, the present invention provides a plasma processing apparatus capable of improving in-plane uniformity of a plasma process in wide RF frequency and power ranges.
• In accordance with a first aspect of the invention, there is provided a plasma processing apparatus including: an evacuable processing chamber; a lower electrode for mounting thereon a substrate in the processing chamber; an upper electrode facing the lower electrode in parallel in the processing chamber; a processing gas supplying unit for supplying a processing gas to a processing space between the upper electrode and the lower electrode; a radio frequency (RF) power supply unit for applying an RF power to one of the lower and the upper electrode to generate a plasma of the processing gas by RF discharge; and an electrically conductive RF ground member which covers a periphery portion of the electrode to which the RF power is applied to receive RF power emitted outwardly in radial directions from the periphery portion of the electrode to which the RF power is applied and send the received RF power to a ground line.
• The electrode to which the RF power is applied may be the lower electrode.
• In this configuration, when the RF power from the RF power supply unit goes around into the electrode main surface (top surface) along a surface layer of the lower electrode, a part of the RF power is emitted out of the periphery portion of the top surface of the electrode. Since the RF ground member receives the part of the RF power and sends it to the ground line, the part of the RF power makes no contribution to discharge of the processing gas, i.e., plasma generation. Thus, a plasma generation region in the processing space is confined to a region right above or near the substrate to be processed and a profile of the plasma density distribution on the substrate can be stabilized.
• In accordance with a second aspect of the invention, there is provided a plasma processing apparatus including: an evacuable processing chamber; a lower electrode for mounting thereon a substrate in the processing chamber; an upper electrode facing the lower electrode in parallel in the processing chamber; a processing gas supplying unit for supplying a processing gas to a processing space between the upper electrode and the lower electrode; a radio frequency (RF) power supply unit for applying an RF power to one of the lower and the upper electrode to generate a plasma of the processing gas by RF discharge; and a grounded electrically conductive RF ground member which covers a periphery portion of a top or a bottom surface and a side surface of the electrode to which the RF power is applied.
• The electrode to which the RF power is applied may be the lower electrode.
• In this configuration, when the RF power from the RF power supply unit goes around into the electrode main surface (top surface) along a surface layer of the lower electrode, a part of the RF power is emitted out of the periphery portion of the top surface and a side surface of the electrode. Since the RF ground member receives the part of the RF power and sends it to the ground line, the part of the RF power makes no contribution to discharge of the processing gas, i.e., plasma generation. Thus, a plasma generation region in the processing space is confined to a region right above or near the substrate to be processed and a profile of the plasma density distribution on the substrate can be stabilized. In addition, the RF ground member may preferably covers a substantially entire region of the top surface of the lower electrode projecting outwardly in radial directions from the substrate.
• A dielectric material may be interposed between the lower electrode and the RF ground member. Further, a surface of the RF ground member is covered by an insulating film.
• It is preferable that an annular gas exhaust path for connecting the processing space to a gas exhaust port provided at a bottom portion of the processing chamber may be formed between the RF ground member and an inner wall of the processing chamber, and a plurality of conductive fin members, which is electrically grounded and vertically extending, for promotion of extinction of a plasma diffused from the processing space is provided at an upper region of the gas exhaust path. This plasma extinction promotion function of the fin members may reduce plasma existing near or above the entrance of the gas exhaust path, thereby relatively increasing the plasma density of a region right above the wafer while reducing altitude differences in the plasma density distribution.
• The plurality of fin members may be seamlessly molded as a single unit with or attached to an electrically conductive exhaust ring provided annularly at the upper region of the gas exhaust path and surfaces of the fin members are covered by insulating films. Further, the fin members are radially disposed at regular intervals in a circumferential direction of the gas exhaust path.
• Further, by providing the RF ground member, a plasma density distribution on the substrate can have the mountain-like profile in a wide RF power range. In order to correct the profile to make it more flattened, it is preferable that a dielectric material having a thickness distribution in which the dielectric material is thickest in the central portion of the lower or the upper electrode and is thinnest in an edge portion of the lower or the upper electrode may be prepared at a top surface region of the lower electrode or a bottom surface region of the upper electrode.
• The RF power may have a frequency equal to or higher than 80 MHz. With such configuration, it is possible to improve in-plane uniformity of a plasma density and a plasma process in wide RF power ranges. Further, another RF power is applied to the lower electrode to attract ions in the plasma mainly towards the substrate disposed on the lower electrode from another RF power supply unit.
• In accordance with the plasma processing apparatus of the present invention with the above-described configuration and operation, it is possible to improve in-plane uniformity of a plasma process in wide RF frequency and power ranges.
BRIEF DESCRIPTION OF THE DRAWINGS
• The objects and features of the present invention will become apparent from the following description of embodiments, given in conjunction with the accompanying drawings, in which:
• FIG. 1 is a vertical cross sectional view showing a configuration of a capacitively coupled plasma etching apparatus in accordance with an embodiment of the present invention;
• FIG. 2 is a partially-enlarged sectional view showing an enlarged configuration of a main part in the capacitively coupled plasma etching apparatus in accordance with the embodiment of the present invention;
• FIG. 3 is a view for explaining operation and function of an RF ground member in accordance with the embodiment of the present invention;
• FIG. 4 is a perspective view showing an example of a configuration of a fin member in accordance with the embodiment of the present invention;
• FIG. 5 is a partially-enlarged sectional view of a comparative example showing a main part of a configuration with no RF ground member and no fin member in the plasma etching apparatus shown inFIG. 1;
• FIGS. 6A to 6C show an example of an etching rate distribution characteristic obtained from the configuration of the apparatus in accordance with the embodiment of the present invention;
• FIGS. 7A to 7C show an etching rate distribution characteristic of a comparative example obtained from the configuration of the apparatus shown inFIG. 5;
• FIG. 8 is a partially-enlarged sectional view showing a configuration of a main part of a modification of the plasma etching apparatus in accordance with the embodiment of the present invention;
• FIG. 9 is a partially-enlarged sectional view showing a configuration of a main part of another modification of the plasma etching apparatus in accordance with the embodiment of the present invention; and
• FIG. 10 is a partially-enlarged sectional view showing a configuration of a main part of still another modification of the plasma etching apparatus in accordance with the embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
• Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings which form a part hereof.
• FIG. 1 shows a configuration of a plasma etching apparatus in accordance with an embodiment of the present invention. The plasma processing apparatus is configured as a capacitively coupled plasma etching apparatus of a cathode coupling type (lower electrode dual frequency application type) in which dual radio frequency (RF) powers are applied to a lower electrode, and includes a cylindrical chamber (processing chamber)10 made of metal such as aluminum, stainless steel or the like. Thechamber10 is frame grounded.
• A circular plate-shaped lower electrode or asusceptor12 for mounting thereon a substrate to be processed, e.g., a semiconductor wafer W, is installed in thechamber10. Thesusceptor12 is made of a conductive material, e.g., aluminum, and is supported by the bottom wall of thechamber10 through acylindrical support14 made of an insulating material, e.g., alumina.
• AnRF ground member18 is vertically extended from a bottom wall of thechamber10. TheRF ground member18 covers a side surface, preferably the entire side surface, and a periphery portion (edge portion) of a top surface (hereinafter, referred to as “top periphery portion”) of thesusceptor12 with adielectric material16 interposed therebetween. Thedielectric material16 is made of, e.g., quartz. A lower portion of thedielectric material16 is connected to an upper portion of the cylindrical insulatingsupport14, while an upper portion thereof is bent approximately at a right angle toward the center of thesusceptor12 so as to cover the top periphery portion of thesusceptor12. TheRF ground member18 is made of aluminum whose surface is covered by an anodic oxide film or an insulating film19 (seeFIG. 2, illustration of the insulatingfilm19 will be omitted in other figures.) such as Y₂O₃or the like. A lower portion of theRF ground member18 is connected to the bottom wall of thechamber10 and an upper portion of theRF ground member18 is bent approximately at a right angle toward the center of thesusceptor12 so as to cover the top periphery portion of thesusceptor12 via thedielectric material16.
• Agas exhaust path20 is annularly formed between theRF ground member18 and the inner wall of thechamber10. In addition, an exhaust ring (baffle plate)22 of a conical shape is annularly attached near the entrance or at an upper portion of thegas exhaust path20 and agas exhaust port24 is provided at a bottom portion of thegas exhaust path20. Further, agas exhaust unit28 is connected to thegas exhaust port24 via agas exhaust pipe26. Thegas exhaust unit28 has a vacuum pump so that a processing space in thechamber10 can be depressurized to a desired vacuum level. Attached to an outer sidewall of thechamber10 is agate valve30 for opening and closing a loading/unloading port for the semiconductor wafer W.
• A firstRF power supply32 for RF discharge is electrically connected to thesusceptor12 via afirst matching unit34 and apower feed rod36. The firstRF power supply32 applies a first RF power having a relatively high frequency appropriate for plasma generation, e.g., 100 MHz, to the lower electrode, i.e., thesusceptor12. Ashower head38 to be described later, serving as an upper electrode of a ground potential, is provided in a ceiling portion of thechamber10. With this configuration, the first RF power from the firstRF power supply32 is capacitively applied between the susceptor12 and theshower head38.
• Moreover, a secondRF power supply70 is electrically connected to thesusceptor12 via a second matching unit72 and thepower feed rod36. The secondRF power supply70 outputs a second RF power having a relatively low frequency appropriate for ion attraction, e.g., 3.2 MHz.
• Anelectrostatic chuck40 for attracting and holding the semiconductor wafer W by an electrostatic attractive force is provided on the top surface of thesusceptor12. Theelectrostatic chuck40 is formed by embedding an electrode made of a sheet or mesh-like conductive material in an insulating film. This electrode is electrically connected with aDC power supply42 via aswitch43 and an electric wire. By a Coulomb force generated by a DC voltage from theDC power supply42, the semiconductor wafer W can be attracted to be held by theelectrostatic chuck40.
• Installed in thesusceptor12 is acoolant chamber44 extended in, e.g., a circumferential direction. In thecoolant chamber44, a coolant of a predetermined temperature, e.g., cooling water, from achiller unit46 is circulated vialines48 and50. A process temperature of the semiconductor wafer W on theelectrostatic chuck40 can be controlled based on the temperature of the coolant. Further, a heat transfer gas, e.g., He gas, from a heat transfergas supply unit52 is supplied between the top surface of theelectrostatic chuck40 and the backside of the semiconductor wafer W via agas supply line54.
• Theshower head38 on the ceiling portion includes anelectrode plate56 having a plurality ofgas injection holes56a in the bottom surface and anelectrode support58 for detachably supporting theelectrode plate56. Abuffer chamber60 is provided within theelectrode support58, and agas supply line64 extending from a processinggas supplying unit62 is connected to agas inlet port60aof thebuffer chamber60.
• Tworing magnets66aand66bannularly or concentrically extending are disposed around thechamber10 and magnetic fields are generated at a peripheral region of a processing space PS between the susceptor12 and theupper electrode38. Thesering magnets66aand66bare arranged to be rotated by a rotation mechanism (not shown).
• Acontroller68 is provided to control operation of each unit in the plasma etching apparatus such as thegas exhaust unit28, the firstRF power supply32, thefirst matching unit34, theswitch43 for the electrostatic chuck, thechiller unit46, the heat transfergas supply unit52, the processinggas supplying unit62, the secondRF power supply70, the second matching unit72 and the like. In addition, thecontroller68 is connected to a host computer (not shown) and the like.
• To carry out an etching process in the plasma etching apparatus, first, thegate valve30 is opened. Next, the semiconductor wafer W to be processed is loaded into thechamber10 to be mounted on theelectrostatic chuck40. Thereafter, an etching gas (generally a gaseous mixture) is introduced at a predetermined flow rate from the processinggas supplying unit62 into thechamber10 and the internal pressure of thechamber10 is set to a preset value by thegas exhaust unit28. Moreover, the first RF power is supplied with a predetermined power from the firstRF power supply32 to thesusceptor12 while the second RF power is supplied with a predetermined power from the secondRF power supply70 to thesusceptor12. Further, a DC voltage is applied from theDC power supply42 to the electrode of theelectrostatic chuck40, thus attracting and holding the semiconductor wafer W on theelectrostatic chuck40. The etching gas injected through theshower head38 is converted to a plasma between bothelectrodes12 and38 by the first RF discharge, and the main surface of the semiconductor wafer W is etched into a desired pattern by radicals or ions generated by the plasma.
• In the plasma etching apparatus, by applying the first RF power having a radio frequency (preferably80 MHz or higher) significantly higher than that applied in the conventional techniques from the firstRF power supply32 to the susceptor (lower electrode)12, a high-density plasma in a desirable dissociated state can be generated even at a lower pressure. At the same time, by applying the second RF power having a relatively low frequency (e.g., 3.2 MHz) appropriate for ion attracting to thesusceptor12, an anisotropic etching with high selectivity for a film to be processed on a semiconductor wafer W can be performed. While the first RF power for plasma generation is always used in all plasma processes, the second RF power for ion attraction may or may not be used depending on a process.
• The main feature of this capacitively coupled plasma etching apparatus lies in the configuration that the electrically conductiveRF ground member18 covers the side surface and the top periphery portion of thesusceptor12 via thedielectric material16, as shown in an enlarged partial view inFIG. 2.
• Now, operation and function of theRF ground member18 will be described with reference toFIG. 3. The ion attraction by the second RF power has no particular relation to the operation of theRF ground member18, and therefore, the secondRF power supply70 is not shown inFIG. 3.
• InFIG. 3, the first RF power outputted from the firstRF power supply32 is transmitted to the bottom center of thesusceptor12 through a surface layer of the circumferential surface of thepower feed rod36 to propagate outwardly in radial directions along a surface layer of the bottom surface of the susceptor therefrom, and reaches to the top surface of the susceptor by flowing through the outer circumferential surface (side surface) of the susceptor. At the top surface of thesusceptor12, the first RF power goes out of the semiconductor wafer W and is emitted into the processing space PS while propagating inwardly in the inverse radial directions from the top periphery portion to the central portion of the top surface (hereinafter, referred to as “top central portion”) of the susceptor. The first RF power emitted into the processing space PS collides with molecules of the processing gas, thereby ionizing or dissociating the gas molecules. Here, if the frequency of the first RF power exceeds about 80 MHz, a percentage of the first RF power escaping through the outer circumferential surface (side surface) or the top periphery portion of thesusceptor12 before the first RF power reaches to a portion below the semiconductor wafer W, i.e., the top surface of thesusceptor12 is measurably increased.
• In the present embodiment, the RF′, the part of the first RF power escaping through the outer circumferential surface (side surface) or the top periphery portion of thesusceptor12, enters into theRF ground member18 immediately after escaping from thedielectric material16, propagates to the bottom wall of thechamber10 along a surface layer of the inner side of theRF ground member18, and then flows into a ground line therefrom.
• Therefore, among the first RF power supplied to thesusceptor12, only the power emitted from the top surface of thesusceptor12 into the processing space PS through the semiconductor wafer W contributes effectively to the ionization or dissociation of the processing gas, i.e., the plasma generation, and a region for plasma generation in the processing space PS is ideally confined to a region right above the semiconductor wafer W. In other words, plasma generation in a region at an outer side in a radial direction other than the region right above the semiconductor wafer W in the processing space PS is extremely limited, and any influence from adjacent regions on the plasma density distribution of the region right above the wafer is suppressed. Accordingly, the plasma density distribution on the semiconductor wafer W mounted on thesusceptor12 can hardly have a W-like profile in which the plasma density distribution is increased at its edge portion as well as its central portion and is sunk at the portion therebetween.
• Further, another feature of the capacitively coupled plasma etching apparatus to improve a plasma density distribution characteristic is a plurality of plate-like fin members25 each having vertical flat surfaces. Thefin members25 are seamlessly molded as a single unit with or attached to thebaffle plate22 disposed near the entrance of thegas exhaust path20. As shown inFIG. 4, thefin members25 are radially disposed at regular intervals in the circumferential direction of thebaffle plate22. Moreover, ventholes22a are formed in the bottom wall of thebaffle plate22. Each of thefin members25 and thebaffle plate22 is made of an electrically conductive material, e.g., aluminum whose surface is covered by an anodic oxide film or an insulating film23 (seeFIG. 2, illustration of the insulatingfilm23 in other figures is omitted) such as Y₂O₃and is electrically grounded via thechamber10 or theRF ground member18.
• Thefin members25 have no effect on inherent functions (vacuum exhaust stabilization function and processing space pressure control function) of thebaffle plate22 and have a function to promote extinction of plasma being diffused from the processing space PS to thegas exhaust path20. This plasma extinction promotion function of thefin members25 may reduce the amount of the plasma existing near or above the entrance of thegas exhaust path20, thereby relatively increasing the plasma density of a region right above the wafer while reducing altitude differences in a mountain-like profile.
• FIGS. 6A to 6C show an example of an in-plane distribution characteristic of an etching rate obtained in the etching process using the plasma etching apparatus shown inFIG. 1 in accordance with the embodiment. The main etching conditions are as follows:
• Wafer diameter: 300 mm
• Film to be etched: photoresist (blanket film)
• Processing gas:O₂100 sccm
• Internal pressure of chamber: 5 mTorr
• RF power: 100 MHz/3.2 MHz=500 to 2000/0 W
• Temperature: upper electrode/sidewall of chamber/lower electrode=60/60/20° C.
• Heat transfer gas (He gas) supply pressure: central portion/edge portion=10/50 Torr
• FIGS. 7A to 7C show a comparative example of an in-plane distribution characteristic of an etching rate under the same etching conditions as the above for a configuration having neitherRF ground member18 norfin members25 in the plasma etching apparatus shown inFIG. 1, that is, the configuration of surrounding of thesusceptor12, as shown inFIG. 5.
• InFIG. 5, adielectric material16′ covers the top periphery portion of thesusceptor12 and is exposed to oppositely face theupper electrode38, the ceiling or inner wall of thechamber10. Afocus ring80 made of, e.g., Si, SiC or the like is mounted on thedielectric material16′ so as to surround a wafer mount region on the top surface of thesusceptor12. A groundedcylindrical conductor82 covering a side surface of thedielectric material16′ forms a wall of thegas exhaust path20, but does not cover the top of thesusceptor12 and thedielectric material16′.
• When theRF ground member18 and thefin members25 are not provided, as shown inFIGS. 7A to 7C, in-plane uniformity of an etching rate is significantly deteriorated from ±28.8% to ±39.6% and ±46.5% respectively as the first RF (100 MHz) power for plasma generation is increased from 500 W to 1000 W and 2000 W. On the other hand, an etching rate distribution for a low power level of 500 W is increased in an edge portion as well as a central portion on the substrate so that the etching rate distribution in a middle portion between the edge and central portion is sunk. Therefore, a W-like profile is produced.
• On the contrary, in the present embodiment, as shown inFIGS. 6A to 6C, even when the first RF (100 MHz) power is increased from 500 W to 1000 W and 2000 W, the in-plane uniformity of the etching rate is stable with no significant change, changing from ±15.8% to ±20.7% and ±20.1%, respectively. Further, a mountain-like profile is constantly produced in any power level even though each has a different altitude, and a W-like profile is not produced.
• Since an etching rate of a photoresist generally depends on electron density, the etching rate distribution characteristics shown inFIGS. 6A to 6C andFIGS. 7A to 7C may be evaluated by substituting them with electron density distribution characteristics.
• As described above, in accordance with the present invention, even when the RF power for plasma generation has a substantially high frequency (80 MHz or above), it is possible to stabilize the in-plane uniformity of the electron density distribution in a wide RF power range while preventing an irregular change of an electron density distribution profile (particularly generation of a W-like electron density distribution profile). Accordingly, the in-plane uniformity of the plasma etching can be improved.
• Further, since the electron density distribution has the mountain-like profile in any RF power level in the plasma etching apparatus of the above-described embodiment, a configuration in which adielectric material84 is embedded at the top surface of the susceptor13 as shown inFIG. 8 may be preferably used to flatten the mountain-like profile. In this case, thedielectric material84 may be prepared such that it has the largest thickness at the center of thesusceptor12 and is gradually getting thinner from the center (or from a point off the center) toward an edge portion of thesusceptor12.
• To the same purpose, adielectric material86 may be embedded at the bottom of theupper electrode38 as shown inFIG. 9. In this case, similarly, thedielectric material86 may be prepared such that it has the largest thickness at the center of thesusceptor12 and is gradually getting thinner from the center (or from a point off the center) toward an edge portion of thesusceptor12.
• Although the embodiment of the present invention has been illustrated in the above, the present invention is not limited to the above embodiment, and may be variously modified. Particularly, various selections and modifications for theRF ground member18 and thefin members25 may be made such that they are optimally combined with other mechanisms in the apparatus.
• For example, as shown inFIG. 9, an appropriate gap may be prepared between an edge portion of the semiconductor wafer W and theRF ground member18 on the top surface of thesusceptor12 and acover88 made of an appropriate material (e.g., Si, SiC or the like) is provided in the gap in an electrically floating state. In this case, the RF power is emitted from the top surface of thesusceptor12 into the processing space PS through thedielectric material16 and thecover88, and plasma is also generated in a region above thecover88. Further, thebaffle plate22 may be configured to have other shape than the conical shape, e.g., a flat annular shape having a main surface horizontally oriented, and the upper surfaces of thefin members25 may be configured to be tilted as shown inFIG. 9. Further, although not shown, thefin members25 may be configured to be separated from thebaffle plate22.
• Further, as shown inFIG. 10, the upper surface of theRF ground member18 may be covered by acover90.
• Moreover, the present invention is not limited to lower electrode dual frequency application type as in the above embodiment but may be, e.g., applied to a lower electrode single frequency application type in which a single RF power is applied to the susceptor (lower electrode) or a type in which an RF power for plasma generation is applied to the upper electrode.
• Further, although not shown, in an apparatus in which the RF power for plasma generation is applied to the upper electrode, an RF ground member having the same configuration and function as theRF ground member18 described in the above embodiment may be provided in the peripheral region of the upper electrode. By providing the RF ground member covering a side surface and a periphery portion of a bottom surface of the upper electrode, even when a part of the RF power applied to the upper electrode is emitted or leaked outwardly in radial directions at the side surface and the periphery portion of the bottom surface of the upper electrode, the RF ground member can receive the leaked RF power and send it to the ground line such that a plasma generation region in the processing space can be confined to a region right above and near a substrate to be processed.
• The present invention is not limited to a plasma etching apparatus but may be applied to other plasma processing apparatuses for performing plasma CVD, plasma oxidation, plasma nitridation, sputtering and the like. Furthermore, the substrate to be processed in the present invention is not limited to the semiconductor wafer but may be various substrates for flat panel displays, photo masks, CD substrates, printed substrates and so forth.
• While the invention has been shown and described with respect to the embodiments, it will be understood by those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

Claims (20)

1. A plasma processing apparatus comprising:

an evacuable processing chamber;

a lower electrode for mounting thereon a substrate in the processing chamber;

an upper electrode facing the lower electrode in parallel in the processing chamber;

a processing gas supplying unit for supplying a processing gas to a processing space between the upper electrode and the lower electrode;

a radio frequency (RF) power supply unit for applying an RF power to one of the lower and the upper electrode to generate a plasma of the processing gas by RF discharge; and

an electrically conductive RF ground member which covers a periphery portion of the electrode to which the RF power is applied to receive RF power emitted outwardly in radial directions from the periphery portion of the electrode to which the RF power is applied and send the received RF power to a ground line.

2. The plasma processing apparatus ofclaim 1, wherein the electrode to which the RF power is applied is the lower electrode.

3. The plasma processing apparatus ofclaim 2, wherein a dielectric material is interposed between the lower electrode and the RF ground member.

4. The plasma processing apparatus ofclaim 2, wherein a surface of the RF ground member is covered by an insulating film.

5. The plasma processing apparatus ofclaim 2, wherein an annular gas exhaust path for connecting the processing space to a gas exhaust port provided at a bottom portion of the processing chamber is formed between the RF ground member and an inner wall of the processing chamber, and

wherein a plurality of conductive fin members, which is electrically grounded and vertically extending, for promotion of extinction of a plasma diffused from the processing space is provided at an upper region of the gas exhaust path.

6. The plasma processing apparatus ofclaim 5, wherein the plurality of fin members is seamlessly molded as a single unit with or attached to an electrically conductive exhaust ring provided annularly at the upper region of the gas exhaust path.

7. The plasma processing apparatus ofclaim 6, wherein surfaces of the fin members are covered by insulating films.

8. The plasma processing apparatus ofclaim 5, wherein the fin members are radially disposed at regular intervals in a circumferential direction of the gas exhaust path.

9. The plasma processing apparatus ofclaim 2, wherein a dielectric material having a thickness distribution in which the dielectric material is thickest in the central portion of the lower or the upper electrode and is thinnest in an edge portion of the lower or the upper electrode is prepared at the top surface region of the lower electrode or a bottom surface region of the upper electrode.

10. The plasma processing apparatus ofclaim 1, wherein the RF power has a frequency equal to or higher than 80 MHz.

11. A plasma processing apparatus comprising:

an evacuable processing chamber;

a lower electrode for mounting thereon a substrate in the processing chamber;

an upper electrode facing the lower electrode in parallel in the processing chamber;

a processing gas supplying unit for supplying a processing gas to a processing space between the upper electrode and the lower electrode;

a radio frequency (RF) power supply unit for applying an RF power to one of the lower and the upper electrode to generate a plasma of the processing gas by RF discharge; and

a grounded electrically conductive RF ground member which covers a periphery portion of a top or a bottom surface and a side surface of the electrode to which the RF power is applied.

12. The plasma processing apparatus ofclaim 11, wherein the electrode to which the RF power is applied is the lower electrode.

13. The plasma processing apparatus ofclaim 12, wherein the RF ground member covers a substantially entire region of the top surface of the lower electrode projecting outwardly in radial directions from the substrate.

14. The plasma processing apparatus ofclaim 12, wherein a dielectric material is interposed between the lower electrode and the RF ground member.

15. The plasma processing apparatus ofclaim 12, wherein a surface of the RF ground member is covered by an insulating film.

16. The plasma processing apparatus ofclaim 12, wherein an annular gas exhaust path for connecting the processing space to a gas exhaust port provided at a bottom portion of the processing chamber is formed between the RF ground member and an inner wall of the processing chamber, and

wherein a plurality of conductive fin members, which is electrically grounded and vertically extending, for promotion of extinction of a plasma diffused from the processing space is provided at an upper region of the gas exhaust path.

17. The plasma processing apparatus ofclaim 16, wherein the plurality of fin members is seamlessly molded as a single unit with or attached to an electrically conductive exhaust ring provided annularly at the upper region of the gas exhaust path.

18. The plasma processing apparatus ofclaim 17, wherein surfaces of the fin members are covered by insulating films.

19. The plasma processing apparatus ofclaim 16, wherein the fin members are radially disposed at regular intervals in a circumferential direction of the gas exhaust path.

20. The plasma processing apparatus ofclaim 12, wherein a dielectric material having a thickness distribution in which the dielectric material is thickest in the central portion of the lower or the upper electrode and is thinnest in an edge portion of the lower or the upper electrode is prepared at the top surface region of the lower electrode or a bottom surface region of the upper electrode.

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