Patent Publication Number: US-2010116436-A1

Title: Ring-shaped member and method for manufacturing same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2008-286686 filed on Nov. 7, 2008, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a ring-shaped member and a method for manufacturing the same; and, more particularly, to a ring-shaped member having a surface exposed to a plasma. 
     BACKGROUND OF THE INVENTION 
     In a substrate processing apparatus for performing a predetermined plasma processing on a disc-shaped semiconductor wafer, ring-shaped members shaped in harmony with the disc-shaped wafer are arranged in an accommodation chamber wherein the wafer is accommodated and a plasma is generated. 
     A focus ring is known as a typical example of the ring-shaped member. The focus ring is a ring-shaped member surrounding a periphery of the wafer, and is conventionally made of a dielectric material. Thus, the focus ring serves to confine the plasma generated in the accommodation chamber in a space above the wafer, thus facilitating the plasma processing. 
     With a recent trend towards a large diameter of a wafer, the uniformity of the plasma processing throughout the whole area of the wafer becomes more important than the facilitation of the plasma processing. In case that the focus ring is made of a dielectric material as described above, the plasma may concentrate along the boundary between the wafer and the focus ring and, thus, the uniformity of the plasma processing cannot be achieved in the peripheral portion of the wafer. Therefore, there is provided a focus ring which is partially or entirely made of an electrical conductor so that a plasma distribution region is extended from the space above the wafer to a space above the focus ring to maintain the uniformity of the plasma processing (see, e.g., Japanese Patent Application Publication No. 2002-246370 and its corresponding U.S. Patent Application Publication No. 20040074605). 
     In view of maintaining the uniformity of the plasma processing, a single crystalline silicon same as the material of the wafer is preferably used as the electrical conductor forming the focus ring. Moreover, a single crystalline silicon ingot is used in a method for manufacturing a focus ring same as in a method for manufacturing a wafer. 
       FIGS. 8A to 8D  present a processing sequence describing a general method for manufacturing a focus ring. 
     First, a single crystalline silicon ingot is shaped as a solid cylindrical member  80  having a predetermined diameter ( FIG. 8A ), and a plurality of circular plates  81  is obtained by slicing the solid cylindrical member  80  ( FIG. 8B ). Next, a peripheral portion of each circular plate  81  is cut to form a focus ring  82  ( FIGS. 8C and 8D ). 
     In that case, however, a circular plate  83  remains as a leftover from the cutting operation in which the focus ring  82  is cut from the circular plate  81 . The diameter of the circular plate  83  is smaller than that of the focus ring  82 , so that the peripheral portion of the circular plate  83  cannot be cut to from the focus ring  82 . This deteriorates the productivity for the manufacture of the focus ring  82 . 
     Further, when the focus ring  82  is cut as a single unit from the circular plate  81  made of single crystalline silicon, the degree of freedom of the cutting position is low. Therefore, an easily erodible crystal plane of single crystalline silicon may appear on the surface of the focus ring  82  to be exposed to the plasma. As a result, the consumption of the focus ring  82  by the plasma increases. 
     SUMMARY OF THE INVENTION 
     In view of the above, the present invention provides a ring-shaped member that reduces its erosion by a plasma and its productivity deterioration and a method for manufacturing the same. 
     In accordance with an aspect of the present invention, there is provided a ring-shaped member for use in a chamber of a substrate processing apparatus for performing a plasma processing on a substrate by generating a plasma in the chamber, the ring-shaped member including: a plurality of circular arc-shaped members made of single crystalline material and arranged along a circumferential direction of the ring-shaped member, wherein each of the circular arc-shaped members includes a surface exposed to the plasma when the plasma is generated in the chamber and an easily erodible crystal plane of the single crystalline material is not exposed at the surface. 
     In accordance with another aspect of the present invention, there is provided a method for manufacturing a ring-shaped member accommodated in a chamber of a substrate processing apparatus for performing a plasma processing on a substrate by generating a plasma in the chamber, the method including: fabricating a plurality of first ring-shaped members from a peripheral portion of a cylindrical member, which is made of a single crystalline material and has a predetermined diameter; cutting a plurality of circular arc-shaped members having a curvature identical to that of the first ring-shaped member from a member remaining as a leftover from the fabricating operation in which the first ring-shaped member is cut from the cylindrical member; and 
     arranging the circular arc-shaped members along a circumferential direction and bonding the arranged members one another to form a second ring-shaped member, wherein each of the circular arc-shaped members includes a surface exposed to the plasma when the plasma is generated in the chamber and an easily erodible crystal plane of the single crystalline material is not exposed at the surface in said cutting the plurality of circular arc-shaped members. 
    
    
     
       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 cross sectional view schematically showing a configuration of a substrate processing apparatus including a focus ring as a ring-shaped member in accordance with an embodiment of the present invention; 
         FIG. 2  depicts a perspective view for explaining a detailed configuration of the focus ring shown in  FIG. 1 ; 
         FIGS. 3A to 3C  provide a processing sequence presenting a method of manufacturing a focus ring as an example of manufacturing a ring-shaped member in accordance with the embodiment of the present invention; 
         FIGS. 4A to 4F  present a processing sequence showing a modification of the method of manufacturing a focus ring as the example of manufacturing a ring-shaped member in accordance with the embodiment of the present invention; 
         FIGS. 5A and 5B  schematically show a modification of a configuration around an electrostatic chuck and the focus ring in the substrate processing apparatus shown in  FIG. 1 , wherein  FIG. 5A  is a cross sectional view and  FIG. 5B  is a top view; 
         FIG. 6  presents a cross sectional view schematically illustrating a configuration of a substrate processing apparatus including a ground electrode as a ring-shaped member in accordance with an embodiment of the present invention; 
         FIG. 7  represents a cross sectional view schematically describing a configuration of a substrate processing apparatus including an outer electrode plate as a ring-shaped member in accordance with an embodiment of the present invention; and 
         FIGS. 8A to 8D  set forth a processing sequence showing a general method for manufacturing a focus ring. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings which form a part hereof. 
       FIG. 1  is a cross sectional view schematically showing a configuration of a substrate processing apparatus including a focus ring serving as a ring-shaped member in accordance with an embodiment. The substrate processing apparatus is configured to perform a plasma etching process on a wafer. 
     Referring to  FIG. 1 , a substrate processing apparatus includes a chamber  11  (accommodation chamber) that accommodates therein a wafer W, which is made of, e.g., single crystalline silicon and has a diameter of about 300 mm, and a cylindrical susceptor  12  on which the wafer W is mounted is disposed in the chamber  11 . Further, in the substrate processing apparatus  10 , a side exhaust passageway serving as a passageway for exhausting a gas present above the susceptor  12  to the outside of the chamber  11  is formed by an inner sidewall of the chamber  11  and a side surface of the susceptor  12 . A gas exhaust plate  14  is provided in the middle of the side exhaust passageway  13 . 
     The gas exhaust plate  14  is a plate-shaped member having a plurality of openings, and serves as a partition plate for partitioning the chamber  11  into an upper space and a lower space. A plasma is generated in the upper space (hereinafter, referred to as a “reaction chamber”)  17  of the chamber  11  partitioned by the exhaust plate  14 . Further, a gas exhaust pipe  16  for exhausting the gas in the chamber  11  is connected to the lower space (hereinafter, referred to as “exhaust chamber (manifold)”)  18  of the chamber  11 . The gas exhaust plate  14  traps or reflects the plasma generated in the reaction chamber  17  and hence prevents the plasma from leaking into the manifold  18 . 
     The gas exhaust pipe  16  is connected to a TMP (Turbo Molecular Pump) and a DP (Dry Pump) (both not shown) which evacuate and depressurize the chamber  11 . Specifically, the DP depressurizes the chamber  11  from the atmospheric pressure to a medium vacuum state (e.g., 1.3×10 Pa (0.1 Torr) or lower), and the TMP cooperates with the DP to depressurize the chamber  11  to a high vacuum state, the pressure in which is lower than that in the medium vacuum state, (e.g., 1.3×10 −3  Pa (1.0×10 −5  Torr) or lower). Further, the pressure in the chamber  11  is controlled by an APC valve (not shown). 
     The susceptor  12  in the chamber  11  is connected to a first high frequency power supply  19  via a first matching unit (MU)  20 , and is also connected to a second high frequency power supply  31  via a second matching unit (MU)  30 . The first high frequency power supply  19  supplies to the susceptor  12  a high frequency power of a relatively low frequency for ion attraction, and the second high frequency power supply  31  supplies to the susceptor  12  a high frequency power of a relatively high frequency for plasma generation. The susceptor  12  therefore functions as an electrode. Further, the first and the second matching unit  20  and  30  reduce reflections of the high frequency powers from the susceptor  12  to maximize the efficiency in supplying the high-frequency powers to the susceptor  12 . 
     An electrostatic chuck  22  having therein an electrostatic electrode plate  21  is disposed on an upper portion of the susceptor  12 . The electrostatic chuck  22  is configured to include a lower disc-shaped member having a certain diameter and an upper disc-shaped member mounted thereon and having a diameter smaller than that of the lower disc-shaped member. Further, the lower and the upper disc-shaped member are made of a ceramic material. When the wafer W is mounted on the susceptor  12 , the wafer W is mounted on the upper disc-shaped member of the electrostatic chuck  22 . 
     A DC power supply  23  is electrically connected to the electrostatic electrode plate  21  in the electrostatic chuck  22 . When a positive DC voltage is applied to the electrostatic electrode plate  21 , a negative potential is produced on the surface of the wafer W that faces the electrostatic chuck  22  (hereinafter referred to as a “backside”). A potential difference is thus generated between the electrostatic electrode plate  21  and the backside of the wafer W, and the wafer W is attracted to be held on the upper disc-shaped member of the electrostatic chuck  22  due to a coulomb force or a Johnsen-Rahbek force resulting from the potential difference. 
     Further, a ring-shaped member serving as a focus ring is directly disposed on the electrostatic chuck  22  to surround the wafer W attracted and held on the electrostatic chuck  22 . The focus ring  24  is made of an electrically conductive material, e.g., single crystalline silicon same as that forming the wafer W. Since the focus ring  24  is made of the electrical conductor, the plasma is distributed throughout a space above the wafer W and the focus ring  24  and the plasma density on the peripheral portion of the wafer W is made to be maintained at a level substantially equal to that on the central portion of the wafer W. Accordingly, the uniformity of the plasma etching processing on the entire of the wafer W can be maintained. 
     An annular coolant chamber  25  extending in, e.g., a circumferential direction of the susceptor  12 , is provided in the susceptor  12 . A low-temperature coolant, such as cooling water or Galden (registered trademark), is supplied from a chiller unit (not shown) to the coolant chamber  25  through a coolant line  26  to be circulated in the coolant chamber  25 . The susceptor  12  cooled by the low-temperature coolant cools the wafer W and the focus ring  24  via the electrostatic chuck  22 . 
     A plurality of heat-transfer gas supply holes  27  are formed in the portion of the upper disc-shaped member of the electrostatic chuck  22  where the wafer W is attracted and held (hereinafter referred to as an “attracting surface”). The heat-transfer gas supply holes  27  are connected to a heat-transfer gas supply unit (not shown) through a heat-transfer gas supply line  28 , and the heat-transfer gas supply unit supplies, e.g., helium (He) gas as a heat-transfer gas to a gap between the attracting surface and the backside of the wafer W through the heat-transfer gas supply holes  27 . The He gas supplied to the gap described above effectively transfers heat from the wafer W to the electrostatic chuck  22 . 
     A shower head  29  is disposed at the ceiling of the chamber  11  to oppositely face the susceptor  12 . The shower head  29  includes a disc-shaped ceiling electrode plate  33  having a plurality of gas holes  32 , a cooling plate  34  from which the ceiling electrode plate  33  is detachably suspended, and a cover  35  that covers the cooling plate  34 . Further, a buffer chamber  36  is provided inside the cooling plate  34 , and a processing gas inlet line  37  is connected to the buffer chamber  36 . In the shower head  29 , a processing gas supplied into the buffer chamber  36  through the processing gas inlet line  37  is supplied into the reaction chamber  17  through the gas holes  32 . 
     The operation of the components of the above-described substrate processing apparatus  10  is controlled by a CPU in a control unit (not shown) of the substrate processing apparatus  10  in accordance with a program for the plasma etching process. 
       FIG. 2  is a perspective view for explaining a detailed configuration of the focus ring shown in  FIG. 1 . 
     Referring to  FIG. 2 , the focus ring  24  is formed by, e.g., four circular arc-shaped members  24   a  to  24   d  having a same curvature. Preferably, the circular arc-shaped members  24   a  to  24   d  are arranged along a circumferential direction, and neighboring circular arc-shaped members are thermally bonded to each other through fusion bonding or diffusion bonding. Moreover, the thermally bonded portions between the circular arc-shaped members  24   a  to  24   d  are preferably amorphized, i.e., become an amorphous material. 
     The circular arc-shaped members  24   a  to  24   d  of the focus ring  24  respectively include top surfaces  24   a   1  to  24   d   1  that are parallel to the surface of the wafer W, which is mounted on the attracting surface of the electrostatic chuck  22  when the focus ring  24  is mounted on the electrostatic chuck  22 ; outer surfaces  24   a   2  to  24   d   2  perpendicularly adjoining to the top surfaces  24   a   1  to  24   d   1 ; and bottom surfaces  24   a   3  to  24   d   3  that are disposed opposite to the top surfaces  24   a   1  to  24   d   1 ; and come into contact with the electrostatic chuck  22  when the focus ring  24  is mounted on the electrostatic chuck  22 . 
     The top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  of the focus ring  24  are exposed to the inside of the reaction chamber  17  and, therefore, are exposed to the plasma when the plasma is generated from the processing gas in the reaction chamber  17 . Especially, when the plasma etching process is performed on the wafer W, the high frequency power for ion attraction is applied to the susceptor  12 . Accordingly, ions in the plasma are attracted to the top surfaces  24   a   1  to  24   d   1  of the focus ring  24  as well as to the surface of the wafer W, so that the top surfaces  24   a   1  to  24   d   1  of the focus ring  24  are sputtered. When the focus ring  24  is eroded by the sputtering, the plasma distribution above the focus ring  24  is disturbed, thereby making it difficult to maintain the uniformity of the plasma etching process on the wafer W. 
     Thus, in the present embodiment, easily erodible crystal planes of single crystalline silicon, e.g., a family of low-index crystal planes, such as (100), (010) or (001) plane which is denoted by Miller index {100} are prevented from appearing on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  exposed to the plasma. Specifically, the circular arc-shaped members  24   a  to  24   d  are cut from a bulk material of single crystalline silicon in such a way that the easily erodible crystal planes of single crystalline silicon are prevented from appearing on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2 . 
     Further, when the focus ring  24  is made of a material other than single crystalline silicon, e.g., a material of a hexagonal lattice system, e.g., SiC, low-index crystal planes which are denoted by Miller indices of four-index notation (Bravais-Miller indices) indicated by the following expression (1) and, more specifically, e.g., the following expression (2) are prevented from being exposed on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2 : 
       (1010), {01  1 0}  (1), and 
       (10  1 0), (01  1 0), (  1 100), (  1 010), (0  1 10) or (1  1 00)  (2). 
     In the focus ring  24 , the crystal planes exposed on the bottom surfaces  24   a   3  to  24   d   3  that are not exposed to the plasma may be denoted by the aforementioned Miller indices of low-index notation, whereas the crystal planes exposed on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  are denoted by Miller indices, e.g., (211), (118) and (131), or those of four-index notation indicated by the following expression (3): 
       (20  2 1), (3  3 02), (  1 108)  (3). 
     Further, in the focus ring  24 , the crystal planes exposed on the top surfaces  24   a   1  to  24   d   1  of the circular arc-shaped members  24   a  to  24   d  are preferably denoted by Miller indices of the same index notation. However, when the crystal planes are denoted by Miller indices of high-index notation, the crystal planes may be denoted by Miller indices of different index notation. 
       FIGS. 3A to 3C  provide a processing sequence showing a method for manufacturing a focus ring serving as a ring-shaped member in accordance with the present embodiment. 
     First, as shown in  FIGS. 8A to 8D , the circular plates  81  are sliced from the solid cylindrical member  80 , which is made of single crystalline silicon and has a predetermined diameter. The peripheral portion of each of the circular plates  81  is cut to obtain a focus ring  82  as a single unit (first ring-shaped member) (first cutting step). Next, by cutting the circular plate  83  that is a leftover from the cutting operation in which the focus ring  82  is cut from the circular plate  81 , a plurality of circular arc-shaped members  24   a  to  24   d  having a curvature same as that of the focus ring  82  can be produced (second cutting step) ( FIG. 3A ). In that case, the circular arc-shaped members  24   a  to  24   d  are cut in such a way that an easily erodible crystal plane of single crystalline silicon is not exposed on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  of the circular arc-shaped members  24   a  to  24   d , that is, the top surfaces  24   a   1  to  24   d   1  of the circular arc-shaped members  24   a  to  24   d  for example is not the easily erodible crystal plane. 
     Next, the circular arc-shaped members  24   a  to  24   d  are arranged along the circumferential direction ( FIG. 3B ). The neighboring circular arc-shaped members are thermally bonded to one another by, e.g., diffusion bonding, thereby forming a focus ring  24  (second ring-shaped member) ( FIG. 3C ) (bonding step). 
     A ring-shaped member serving as the focus ring  24  in accordance with an embodiment of the present invention can be made of the circular arc-shaped members  24   a  to  24   d  arranged along a circumferential direction. In other words, the focus ring  24  can be manufactured by using the circular arc-shaped members  24   a  to  24   d  obtained by cutting the circular plate  83 , which is a member remaining as a leftover from the cutting operation in which the focus ring  82  is cut from the solid cylindrical member  80 . Accordingly, the productivity for the manufacture of the focus ring  24  can be improved. 
     During the plasma etching process, the ions in the plasma are attracted to the surface of the wafer W and also the top surfaces  24   a   1  to  24   d   1  parallel to the surface of the wafer W. Since, however, each of the circular arc-shaped members  24   a  to  24   d  can be cut from various portions of the circular plate  83 , the circular arc-shaped members  24   a  to  24   d  can be cut without exposing an easily erodible crystal plane of single crystalline silicon, e.g., a low-index crystal plane, e.g., {100} on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  of the circular arc-shaped members  24   a  to  24   d . Accordingly, the erosion of the focus ring  24 , which is caused by the plasma, can be suppressed. As a result, the uniform distribution of the plasma on the peripheral portion of the wafer W can be prevented from being disturbed, and the uniformity of the plasma processing on the wafer W can be maintained for a long period of time. 
     In the above-described embodiment, the circular arc-shaped members  24   a  to  24   d  are cut from the circular plate  83 . However, the circular arc-shaped members  24   a  to  24   d  can be directly cut from the solid cylindrical member  80 . In that case, the circular arc-shaped members  24   a  to  24   d  are also cut in such a way that an easily erodible crystal plane of single crystalline silicon is not exposed on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  of the circular arc-shaped members  24   a  to  24   d.    
     In the above-described focus ring  24 , the single crystalline silicon forming the focus ring  24  is the same as the single crystalline silicon forming the wafer W. Therefore, the plasma distribution region is extended from a space above the wafer W to a space also including an additional area above the focus ring  24  and, hence, the plasma density on the peripheral portion of the wafer can be maintained at a level substantially equal to on the central portion of the wafer W. Accordingly, the uniformity of the plasma processing can be maintained on the peripheral portion of the wafer near the focus ring  24 . 
     Moreover, in the above-described focus ring  24 , when the circular arc-shaped members  24   a  to  24   d  are arranged such that the crystal planes denoted by the same Miller indices are exposed on the top surfaces  24   a   1  to  24   d   1  of the circular arc-shaped members  24   a  to  24   d , the top surfaces  24   a   1  to  24   d   1  can be uniformly eroded by the plasma etching process and, further, the uniform distribution of the plasma above the top surfaces  24   a   1  to  24   d   1  can be prevented from being disturbed. 
     Furthermore, in the above-described focus ring  24 , the circular arc-shaped members  24   a  to  24   d  are thermally bonded to each other, and the thermally bonded portions therebetween are amorphized. Therefore, crystal lattices between neighboring circular arc-shaped members can be continuously connected without grain interfaces or lattice defects. Accordingly, the strength of the focus ring  24  can be further increased, thereby facilitating the handling of the focus ring  24 . In addition, the thermally bonded portions are homogenized by amorphization, so that the uniform distribution of the plasma in area above the ring-shaped member can be prevented from being disturbed when the ring-shaped member is electrically charged. 
     In the aforementioned focus ring  24 , the circular arc-shaped members  24   a  to  24   d  are thermally bonded to one another. However, they may be adhered to one another by an adhesive agent. Therefore, the focus ring  24  can be easily formed and, further, the productivity for the manufacture of the focus ring  24  can be further improved. 
     Further, the manufacturing method of the focus ring  24  is not limited to the manufacturing method described in  FIGS. 3A to 3C . 
       FIGS. 4A to 4F  offer a processing sequence illustrating a modification of the method for manufacturing a focus ring as a method for manufacturing a ring-shaped member in accordance with another embodiment. 
     First, the peripheral portion of the solid cylindrical member  80 , which is made of single crystalline silicon and has a predetermined diameter, is cut to form a ring-shaped wall member (hollow cylindrical member) ( FIG. 4A ), and the focus ring  82  (first ring-shaped member) is sliced as a single unit from the ring-shaped wall member  40  thus obtained ( FIG. 4B ) (first cutting step). 
     Next, as a result of the cutting operation in which the ring-shaped wall member  40  is cut from the solid cylindrical member  80 , a solid cylindrical member  41  ( FIG. 4C ) remains to be a leftover therefrom. A side portion of the solid cylindrical member  41  is cut to have a flat surface  42  on the side surface of the solid cylindrical member  41 . A plurality of circular arc-shaped members  24   a  to  24   d  having a curvature same as that of the focus ring  82  is obtained by cutting the flat surface  42  ( FIG. 4D ) (second cutting step). In that case, as in the manufacturing method described in  FIGS. 3A to 3C , the circular arc-shaped members  24   a  to  24   d  are cut in such a way that an easily erodible crystal plane of single crystalline silicon is not exposed on the top surfaces  24   a   1  to  24   d   1  and the outer surfaces  24   a   2  to  24   d   2  of the circular arc-shaped members  24   a  to  24   d.    
     Thereafter, the circular arc-shaped members  24   a  to  24   d  are arranged along the circumferential direction ( FIG. 4E ), and the neighboring circular arc-shaped members are thermally bonded to each other by diffusion bonding, thereby forming the focus ring  24  (second ring-shaped member) ( FIG. 4F ) (bonding step). 
     Meanwhile, the trend towards a large diameter of the wafer W is likely to continue, and the wafer W having a diameter of about 450 mm is expected to be a mainstream in the near future. In that case, in order to manufacture the focus ring  82  as a single unit, there is required a cylindrical member (ingot) made of single crystalline silicon and having a diameter greater than or equal to about 500 mm. However, it is difficult to manufacture an ingot having such diameter. 
     In the manufacturing method shown in  FIGS. 4A to 4F , circular arc-shaped members  24   a  to  24   d  having a radius of curvature greater than that of the cylindrical ingot (solid cylindrical member  41 ) can be produced so that the focus ring  24  having a diameter greater than that of the ingot can be manufactured by cutting the ingot. Therefore, it is possible to deal with the trend towards a large diameter of the wafer W. 
     In the above substrate processing apparatus  10 , the focus ring  24  is directly mounted on the electrostatic chuck  22 . However, if the focus ring  24  is not firmly adhered to the electrostatic chuck  22 , a vacuum layer having a low thermal conductivity is formed between the focus ring  24  and the electrostatic chuck  22 , so that the focus ring  24  heated by impinging ions thereto cannot be effectively cooled by the electrostatic chuck  22  during the plasma etching process. In that case, the temperature of the focus ring  24  increases to about 500° C. and, thus, the peripheral portion of the wafer W is heated by radiant heat from the focus ring  24 , which makes it difficult to maintain the uniformity of the plasma etching process on the wafer W. 
     Therefore, as illustrated in  FIG. 5A , the adhesivity between the focus ring  24  and the electrostatic chuck  22  can be improved by inserting a heat transfer sheet  50  between the electrostatic chuck  22  and the focus ring  24 . Accordingly, the formation of the vacuum layer between the focus ring  24  and the electrostatic chuck  22  can be prevented, and the focus ring  24  can be effectively cooled through the electrostatic chuck  22 . 
     When a ring-shaped resin sheet having adhesivity is used as the heat transfer sheet  50 , the ring-shaped heat transfer sheet  50  is disposed first on the electrostatic chuck  22 , and the circular arc-shaped members  24   a  to  24   d  are arranged along the circumferential direction while adhering to the heat transfer sheet  50 . Accordingly, the circular arc-shaped members  24   a  to  24   d  form the focus ring  24  on the electrostatic chuck  22  without bonding each other. As a result, the productivity for the manufacture of the focus ring  24  can be further improved. 
     The ring-shaped member in accordance with the present embodiment can be applied to components of the substrate processing apparatus other than the aforementioned focus ring  24 . For example, in order to improve the performance of the plasma processing, there is developed a substrate processing apparatus  60  in which a DC voltage is applied from a DC power supply  61  connected to a ceiling electrode plate  33  into a reaction chamber  17  as shown in  FIG. 6 . In order to apply a DC voltage into the reaction chamber  17 , there is required a ground electrode  62  of a DC voltage, wherein a surface thereof is exposed to the inside of the reaction chamber  17 . 
     The ground electrode  62  is a ring-shaped member made of an electrically conductive material, e.g., silicon, and disposed at a bottom portion of the suscepter  12  to surround therearound. The outer surface of the ground electrode  62  is facing the side exhaust passageway  13 . Here, if the ground electrode  62  is formed by a plurality of circular arc-shaped members as in the case of the focus ring  24 , the productivity for the manufacture of the ground electrode  62  can be improved. Further, when the circular arc-shaped members forming the ground electrode  62  are cut, they are cut such that an easily erodible crystal plane of single crystalline silicon is not exposed on the outer surface facing the side exhaust passageway  13 . Accordingly, the erosion of the ground electrode  62 , which is caused by the plasma, can be suppressed. 
     Further, there is conventionally known a substrate processing apparatus  70  in which the second high frequency power supply  31  is connected to the ceiling electrode plate instead of the susceptor  12  as shown in  FIG. 7 , and a high frequency power for plasma generation is supplied to the ceiling electrode plate  33  from the second high frequency power supply  31 . 
     In this substrate processing apparatus  70 , an outer electrode plate  71  (upper electrode) as a ring-shaped member made of an electric conductor, e.g., silicon, is disposed to surround the disc-shaped ceiling electrode plate  33 . The outer electrode plate  71  has a bottom surface exposed to the inside of the reaction chamber  17 . 
     Here, if the outer electrode plate  71  is formed by a plurality of circular arc-shaped members as in the case of the focus ring  24 , the productivity for the manufacture of the outer electrode plate  71  can be improved. Moreover, when the circular arc-shaped members forming the outer electrode plate  71  are cut, they are cut such that an easily erodible crystal plane of single crystalline silicon does not surface on the bottom to be exposed to the inside of the reaction chamber  17 . Accordingly, the erosion of the outer electrode plate  71 , which is caused by the plasma, can be suppressed. 
     In the above-described embodiments, the substrate to which the plasma etching process is performed is a semiconductor wafer. However, the substrate to which the plasma etching process is performed is not limited thereto, and may be a glass substrate, e.g., an LCD (Liquid Crystal Display), an FPD (Flat Panel Display) or the like. 
     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.