Abstract:
A substrate supportingstructure ( 50 ) for semiconductor processing, comprising a mounting table ( 51 ) for placing a processed substrate (W) disposed in a processing chamber ( 20 ), wherein temperature control spaces ( 507 ) for storing the fluid used as a heat exchange medium are formed in the mounting table ( 51 ), a conductive transmission path ( 502 ) is disposed to lead a high frequency power to the mounting table ( 51 ), and flow channels ( 505, 506 ) feeding or discharging the heat exchange medium fluid to or from the temperature control spaces ( 507 ) are formed in the transmission path ( 502 ).

Description:
This application is a Continuation-In-Part Application of PCT International Application No. PCT/JP03/016960 filed on Dec. 26, 2003, which designated the United States. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a substrate supporting structure and a plasma processing device. The term “semiconductor processing” used herein implies various processes to manufacture a semiconductor device and/or a structure including wiring, electrodes, and the like connected to the semiconductor device on a substrate to be processed, by forming a semiconductor layer, an insulating layer, a conductor layer, and the like, after a predetermined pattern, on the substrate to be processed, e.g., a semiconductor wafer, an LCD (Liquid Crystal Display) or an FPD (Flat Panel Display). 
     BACKGROUND OF THE INVENTION 
     With the recent trend of highly integrated and high-performance semiconductor device, improvement in productivity of manufacturing the semiconductor is very essential to realize cost reduction. As for a method for improving the productivity, increasing a diameter of a semiconductor substrate may be enumerated. Conventionally, a 200 mm substrate has been used as a semiconductor substrate (wafer), but, now, a 300 mm substrate is mainly used. If a semiconductor device is fabricated by using a 300 mm substrate of a large diameter, the number of semiconductor devices, which can be produced by using one sheet of substrate, is increased, thereby improving the productivity. 
     In case of using a 300 mm substrate, the conventional semiconductor device for processing a 200 mm substrate should be replaced with a device capable of processing a 300 mm substrate. In this case, a substrate supporting structure for supporting the substrate becomes scaled up, so that the semiconductor processing device such as plasma processing device or the like has to be also large-scaled. Thus, the footprint of the semiconductor processing device is increased, and the number of devices, which can be disposed in a semiconductor production factory, is accordingly decreased to thereby lower the productivity of the semiconductor device. Further, if components for a 200 mm substrate are scaled up to be used for a 300 mm substrate while employing the conventional substrate supporting structure as it is, a substantial cost increase is incurred. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a substrate supporting structure and a plasma processing device for semiconductor processing capable of realizing a scaling-down for miniaturization and reducing cost. 
     It is another object of the present invention to provide a plasma processing device capable of increasing at least inter-surface uniformity of a film formed on a substrate to be processed. 
     In accordance with the one aspect of the present invention, there is provided a substrate supporting structure for semiconductor processing including: a mounting table for mounting thereon a substrate to be processed; and a support part, disposed to be downwardly extended below the mounting table, for supporting the mounting table, wherein the mounting table contains an electrode part; a first insulating layer for covering a periphery of the electrode part; a second insulating layer for covering a bottom surface of the electrode part; and a first conducting layer covering the first and second insulating layers, wherein the support part contains a conductive transmission path for supplying a power to the electrode part; a third insulating layer for covering a periphery of the transmission path; and a second conducting layer for covering a periphery of the third insulating layer, and wherein the electrode part of the mounting table, the first and the second insulating layers and the first conducting layer are coaxially configured; the conductive transmission path of the support part, the third insulating layer and the second conducting layer are coaxially configured; the electrode part and the conductive transmission path are integrally formed; and the first and the second conducting layers are electrically connected to each other, and wherein a first channel for supplying a heat exchange medium into the electrode part is formed; and a second channel communicated with the first channel is formed in the conductive transmission path. 
     In accordance with another aspect of the present invention, there is provided a plasma processing device, including: an airtight processing chamber for accommodating therein a substrate to be processed; a gas supply unit for supplying a processing gas into the processing chamber; a gas pumping unit for exhausting the processing chamber; a mounting table, disposed in the processing chamber, for mounting thereon the substrate; and a support part, disposed to be downwardly extended below the mounting table, for supporting the mounting table, wherein the mounting table contains an electrode part; a first insulating layer for covering a periphery of the electrode part; a second insulating layer for covering a bottom surface of the electrode part; and a first conducting layer covering the first and second insulating layers, wherein the support part contains a conductive transmission path for supplying a power to the electrode part; a third insulating layer for covering a periphery of the transmission path; and a second conducting layer for covering a periphery of the third insulating layer, and wherein the electrode part of the mounting table, the first and the second insulating layers and the first conducting layer are coaxially configured; the conductive transmission path of the support part, the third insulating layer and the second conducting layer are coaxially configured; the electrode part and the conductive transmission path are integrally formed; and the first and the second conducting layers are electrically connected to each other, and wherein a first channel for supplying a heat exchange medium into the electrode part is formed, and a second channel communicated with the first channel is formed in the conductive transmission path. 
     In accordance with still another aspect of the present invention, there is provided a plasma processing device, including: an airtight processing chamber for accommodating therein a substrate to be processed; a gas supply unit for supplying a processing gas into the processing chamber; a gas pumping unit for exhausting the processing chamber; a mounting table, disposed in the processing chamber, for mounting thereon the substrate; and a conductive extension member for surrounding the substrate mounted on the mounting table, the extension member having a surface in parallel with that of the substrate, wherein the mounting table contains an electrode part to which a power is applied; a pedestal insulation layer for covering a bottom surface and a side of the electrode part; and a pedestal conduction layer, electrically connected to the support conduction layer, for covering at least a part of the bottom surface and the side of the pedestal insulation layer; and the electrode part, the pedestal insulation layer and the pedestal conduction layer are coaxially configured, and wherein the extension member is disposed on the pedestal insulation layer while being electrically insulated from the electrode part and the pedestal conduction layer; in the side of the pedestal insulation layer, a top end of the pedestal conduction layer is disposed to be placed below a bottom portion of the electrode part; and impedance between the extension member and the pedestal conduction layer is set to be greater than impedance between the electrode part and the pedestal conduction layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: 
         FIG. 1  offers a configuration view showing a plasma processing device containing a substrate supporting structure for semiconductor processing in accordance with a first embodiment of the present invention; 
         FIG. 2  describes a cross sectional view showing a magnified substrate supporting structure shown in  FIG. 1 ; 
         FIG. 3  sets forth a cross sectional view showing a part of the substrate supporting structure shown in  FIG. 1 ; 
         FIG. 4  presents a cross sectional view showing a magnified X part shown in  FIG. 3 ; 
         FIG. 5  provides a cross sectional view showing a magnified Z part shown in  FIG. 4 ; 
         FIG. 6  describes a transversal cross sectional view taken along Y-Y line shown in  FIG. 2 ; 
         FIGS. 7A and 7B  present partial cross sectional views showing a substrate supporting structure in accordance with a modified example of the first embodiment; 
         FIG. 8  is a graph showing a measurement result of self-bias potential in case of applying a high frequency power to a mounting table; 
         FIG. 9  presents a table showing process conditions; 
         FIG. 10  describes a schematic configuration cross sectional view showing a schematic configuration of a plasma processing device; 
         FIG. 11  offers a schematic configuration view showing a configuration of a main part of the plasma processing device shown in  FIG. 10 ; 
         FIG. 12  presents a magnified partial cross sectional view schematically showing a configuration of an outer periphery of the mounting table; 
         FIGS. 13A and 13B  are circuit diagrams showing equivalent circuits for a plasma in the plasma processing device and a lower electrode; and 
         FIG. 14  shows a magnified partial cross sectional view of the plasma processing device in accordance with a modified example of the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following discussion, identical reference numerals will be assigned for corresponding parts having substantially same functions and configurations, and redundant explanations will be omitted unless necessary. 
     First Embodiment 
       FIG. 1  is a configuration view showing a plasma processing device including a substrate supporting structure for semiconductor processing in accordance with a first embodiment of the present invention. A plasma processing device  10  is configured to perform a sputter etching or a reactive etching on a silicon oxide film, a metal oxide film or the like, which is formed on a semiconductor wafer as a substrate to be processed. 
     As shown in  FIG. 1 , the plasma processing device  10  includes a processing chamber  20  for receiving thereinto a substrate W to be processed. To the processing chamber  20 , a gas supply unit  30  for supplying a processing gas thereinto is coupled. An excitation mechanism  40  for converting the processing gas into a plasma is disposed at an outer upper side of the processing chamber  20 . A mounting table  51  of a substrate supporting structure  50  for supporting the substrate W to be processed is disposed at an inner lower side of the processing chamber  20 . 
     The processing chamber  20  is formed by combining a conductive cylindrical lower side vessel  201  with an insulating cylindrical upper vessel or bell jar  401 . In a center of a bottom portion of the lower side vessel  201 , there is formed an opening, to which a downwardly protruded cylindrical exhaust chamber  202  is airtightly coupled. The exhaust chamber  202  has a planar outline, which is sufficiently small, compared to the processing chamber  20 ; and it is concentrically placed with the processing chamber  20 . 
     At a bottom portion of the exhaust chamber  202 , a support part  52  of the substrate supporting structure  50  is attached. The support part  52  of the substrate supporting structure  50  is fixed to the bottom portion of the exhaust chamber  202  by using an attachment ring  221 , screw reception rings  220  and  222 , clamping screws  219  and the like. Detailed descriptions thereof will be explained later with reference to  FIG. 2 . The support part  52  is vertically elevated at a center of the exhaust chamber  202 , to thereby be coupled to the mounting table  51  through the opening of the bottom portion of the lower side vessel  201 . 
     An opening  218  is formed in a sidewall of the exhaust chamber  202 , and a gas pumping unit  204 , e.g., a turbo molecular pump or the like, is connected thereto through a gas exhaust line  203 . In case when performing an etching, particularly, a sputter etching, a space needs to be kept under a low pressure. For example, the processing space needs to be maintained at a low pressure in the range of 0.0133˜1.33 Pa, and preferably, 0.0133˜0.133 Pa, by using the gas pumping unit  204  such as a turbo molecular pump or the like. 
     An airtight processing space  402  in the processing chamber  20  is vacuum-exhausted by the gas pumping unit  204  through an exhaust space  202 A of the exhaust chamber  202 , which surrounds the support part  52 . Since the processing space  402  is exhausted through the exhaust space  202 A concentrically disposed therebelow, the processing space  402  can be uniformly exhausted compared to the case where the processing space  402  is exhausted through the side of the processing chamber  20 . Namely, the processing gas can be uniformly exhausted with respect to the substrate W as a center. Thus, the pressure in the processing space  402  becomes uniform, thereby producing the plasma uniformly. Hence, uniformity in etching rate while performing an etching on the substrate to be processed is enhanced. 
     At the bottom portion of the exhaust chamber  202 , there is disposed a shielding member or a shield cover  205  made of metal, e.g., aluminum, alloy thereof, that is grounded. An RF introducing component  206  for introducing an RF power into the mounting table  51  of the substrate supporting structure  50  is disposed in the shield cover  205 . The RF introducing component  206  is connected to a high frequency (RF) power supply  210  for a bias-applied through a matching unit  209 . 
     The mounting table  51  of the substrate supporting structure  50  has an electrode part  501  of a circular plate shape; and at the same time, the support part  52  of a columnar shape has a conductive RF transmission path  502 . The electrode part  501  and the transmission path  502  are formed as a unit by using a conductive material such as Al, alloy of Al, or the like, which are electrically connected to each other. A lower portion of the transmission path  502  is electrically connected to the RF introducing component  206 . Thus, the RF power is supplied to the electrode part  501  of the mounting table  51  from the RF power supply  210  though the transmission path  502 , and therefore, a bias voltage is applied to the substrate W to be processed. The shield cover  205  shields the RF to prevent any leakage thereof to the outside. 
     In the electrode part  501  of the mounting table  51 , there is formed a heat exchange medium chamber  507  (herein, a temperature control space, formed as a flow path) for accommodating therein a heat exchange medium, e.g., an insulating coolant fluid, for controlling temperature of the mounting table  51 . Meanwhile, in the transmission path  502  of the support part  52 , an introduction channel  215  and a discharge channel  216  are formed to supply the heat exchange medium into the temperature control space  507  and discharge it therefrom. 
     At a lower portion of the support part  52 , an insulation component  207  made of an insulating material such as ceramic, e.g., Al 2 O 3 , resin or the like, is disposed. The introduction channel  215  and the discharge channel  216  pass through the insulation component  207  to be coupled to metallic connection tubes  213  and  214 , respectively, that are attached to the insulation component  207 . Thus, the connection tubes  213  and  214  are electrically insulated from the RF transmission path  502  by the insulate component  207 . Peripheries of the insulation component  207  and the lower portion of the transmission path  502  are covered by a thermal insulator  217 . 
     The connection tubes  213  and  214  are coupled to a circulation unit (CU), e.g., a chiller, which functions to control the temperature. The heat exchange medium is circulated from the circulation unit (CU) to the temperature control space  507  through the introduction channel  215  and the discharge channel  216 , so that the temperature of the mounting table  51  is maintained at a predetermined temperature. 
     In a side of the lower side vessel  201 , there is formed a transfer port for substrate W, in which a gate valve  208  is disposed. While the gate valve  208  is opened, the substrate W to be processed can be loaded into the processing chamber  20  and unloaded therefrom. At that time, lift pins (e.g., three) of an elevation mechanism  211  are operated to assist transportation of the substrate W from the mounting table  51 . 
     A gas supply unit  30  includes an Ar gas supply source  305  connected to the gas supply line  311  through an Ar gas line  301 , and an H 2  gas supply source  310  connected thereto through an H 2  gas line  306 . Valves  302  and  304  and a mass flow controller  303  are disposed in the Ar gas line  301 . If the valves  302  and  304  are opened, Ar gas is supplied to the gas supply line  311 , wherein the flow rate of the gas to be supplied is controlled by the mass flow controller  303 . In the same manner, valves  307  and  309  and a mass flow controller  308  are disposed in the H 2  gas line  306 . If the valves  307  and  309  are opened, H 2  gas is supplied to the gas supply line  311 , wherein the flow rate of the gas to be supplied is controlled by the mass flow controller  308 . 
     The gas supply line  311 , through which Ar gas and H 2  gas are supplied, is connected to a gas supply ring  212 , which is annularly disposed on the lower side vessel  201  along the edge thereof. A gas supply groove  212 B is annularly formed in the gas supply ring  212  to discharge Ar gas or H 2  gas over the entire periphery of the gas supply ring  212 . Ar gas or H 2  gas is supplied towards the center of the processing space  402  through gas holes  212 A communicating with the gas supply groove  212 B. Ar gas or H 2  gas supplied to the processing space  402  turns into a plasma by an excitation mechanism  40  explained hereinafter. 
     An upper vessel, i.e., a bell jar  401 , is made of a dome shaped insulating material, e.g., quartz, ceramic (Al 2 O 3 , AlN) or the like. An antenna coil  404  of the excitation mechanism  40  is wound around the periphery of the bell jar  401 . The coil  404  is coupled to an RF power supply  403  through a matching unit  405 . The RF power supply  403  generates an RF power having a frequency in the range of, e.g., 450 kHz˜60 MHz (preferably, 450 kHz˜13.56 MHz). 
     If the RF power is supplied to the coil  404  from the RF power supply  403 , an induced magnetic field is formed in the processing space  402 . By the induced magnetic field, gas such as Ar, H 2  or the like, supplied into the processing space  402 , turns into a plasma. Such plasma is referred to as an inductively coupled plasma (ICP). With the plasma excited as above, a plasma processing, e.g., an etching, is performed on the substrate disposed on the mounting table  51 . 
     In the plasma processing device  10 , a diameter Da of the columnar support part  52  of the substrate supporting structure  50  can be made small. Thus, a diameter Db of the exhaust chamber  202  can be made small and the total plasma processing device  10  becomes small, to thereby reduce foot print (occupation area). Further, members such as the gas pumping unit  204 , e.g., turbo molecular pump, a pressure control valve (not shown) and the like are coupled through the gas exhaust line  203  to a gas exhaust port  218  formed on the sidewall of the exhaust chamber  202  (by using the space efficiently). Therefore, the gas exhaust line  203  or the gas pumping unit  204  can be disposed within the outline of the lower side vessel  201  or the excitation mechanism  40  (inside the range shown as the diameter Dc in  FIG. 1 ). 
       FIG. 2  is a cross sectional view showing a magnified substrate supporting structure  50  shown in  FIG. 1 . Hereinafter, the substrate supporting structure  50  will be discussed with reference to  FIG. 2 . As described above, the substrate supporting structure  50  includes the circular plate shaped mounting table  51  and the columnar support part  52  concentrically disposed therebelow. 
     The mounting table  51  contains the aforementioned electrode part  501  to which the RF power is applied. The side of the electrode part  501  is covered with a ring block  508  made of a dielectric material such as quartz or the like. A bottom surface of the electrode part  501  is covered with a plate block  509  made of a dielectric material, e.g., quartz, and having in the center thereof holes, through which the transmission path  502  passes. A pedestal insulation layer is formed of the ring block  508  and the plate block  509 . The bottom surfaces and sides of the insulation layers  508  and  509  are also coated with a pedestal cover (pedestal conduction layer)  514  made of a conductive material such as Al, Ti or the like. The electrode part  501 , the insulation layers  508  and  509  and the conduction layer  514  are coaxially configured. 
     Meanwhile, the support part  52  includes the aforementioned conductive transmission path  502  for introducing the RF power. The transmission path  502  is coated with an insulator (support insulation layer)  513  made of a dielectric material such as PTFE (polytetrafluoroethylene) or the like. The insulator  513  is also coated with a support cover (support conduction layer)  515  made of a conductive material such as Al, Ti or the like, which is grounded. The transmission path  502 , the support insulation layer  513  and the support conduction layer  514  are coaxially configured. 
     The electrode part  501  and the transmission path  502  are molded as a unit by using a conductive material such as Al, alloy thereof or the like, so that these are electrically connected to each other. The ring block and the plate block (pedestal insulation layers)  508  and  509  and the insulator (support insulation layer)  513  are formed individually. The pedestal cover (pedestal conduction layer)  514  and the support cover (support conduction layer)  515  are molded individually. However, they are unified by welding, and at the same time, electrically connected to each other. 
     As described above, the temperature control space  507  accommodating therein the heat exchange medium (fluid) for uniformly maintaining the substrate to be processed at a predetermined temperature is formed in the electrode part  501 . In the temperature control space  507 , the introduction channel  505  and the discharge channel  506 , which are formed in the transmission path  502 , are connected to each other; and a flow path, through which the heat exchange medium flows between the introduction channel  505  and the discharge channel  506 , is formed. 
       FIG. 3  is a cross sectional view showing a part of the substrate supporting structure shown in  FIG. 1 , which describes a cross section substantially normal to the cross section shown in  FIG. 2 . A dielectric layer  503  made of a dielectric material, e.g., alumina (Al 2 O 3 ) or the like, is disposed on a top surface (and a side) of the electrode part  501 , with which the substrate W makes a contact. An electrode  504  is inserted into the dielectric layer  503 , disposed on the top surface, to form an electrostatic chuck together with the dielectric layer  503 . The electrode  504  is connected to a DC power supply (not shown) disposed at the outside of the processing chamber  20  through a wiring  516 , which extends through the transmission path  502  while being insulated. If a voltage is applied to the electrode  504 , an electrostatic polarization is generated at the dielectric layer  502  below the substrate W such that the substrate W is electrostatically adsorbed. 
     The dielectric layer  503  is formed by, e.g., ceramic spraying or the like. Alternatively, the dielectric layer  503  may be formed by using a method wherein a ceramic of sintered body is formed in a thin film to be jointed. Further, the dielectric layer  503  may be formed as a dielectric film such as aluminum nitride (AlN), SiC, BN or the like, without using alumina. 
     As described above, the substrate supporting structure  50  is coaxially configured so that mushroom shaped (T-shaped) conductive cores  501  and  502  connected to the RF power supply  210  for a bias are coated with the insulation layers (dielectric layers)  508 ,  509  and  513 , and also, coated with conduction layers  514  and  515  that are grounded. By such a configuration, loss of the RF power is reduced; efficiency is improved; and the bias can be stably applied to the substrate to be processed. 
     In the first embodiment, PTFE is used as the support insulation layer (insulator)  513 . The reason is that PTFE has a low permittivity of about 2 and the loss of the RF power is reduced. That is, it is preferable that a low dielectric constant material is used for the support insulation layer  513 , taking the efficiency of RF power into consideration. In the same manner, it is preferable that pedestal insulation layers (ring block and plate block)  508  and  509  are formed by using a low dielectric constant material to reduce the loss in the RF power. However, followings should be noted. 
     In a region where the insulation layers (dielectric layers)  508 ,  509  and  513  of the substrate supporting structure  50  are disposed, sealing members  511  and  512  are disposed in the plated block  509  to airtightly separate the mounting table  51  side from the support part  52  side. Namely, the pedestal insulation layers  508  and  509  are placed in a space communicating with the processing space  402  where the plasma is generated in the depressurized state. For the same reason, it is not preferable to use as a material for the pedestal insulation layers  508  and  509  a medium which releases lots of gas. Further, the insulation layers  508  and  509  are greatly influenced by any temperature variation such as a rise or a fall in the temperature due to the generation of plasma. 
     PTFE is porous microscopically compared to a dense material such as quartz or the like, and releases lots of gas in the depressurized state. Thus, it is not preferable to use PTFE in a vacuum vessel. Further, it is problematic that PTFE deforms or has no plasma resistance, to thereby tend to be etched. 
     Accordingly, as for the pedestal insulation layers  508  and  509 , it is preferable to employ such a material that hardly releases any gas in a depressurized vessel and is resistant to a temperature hysteresis, and more preferably, to employ a low dielectric constant material as possible. As for a material satisfying these requirements mentioned above, quartz may be enumerated, and alternatively, e.g., a resin material or the like may be used. Namely, it is preferable to use quartz for the insulation layers  508  and  509 , and PTFE for the support insulation layer  513 . 
     A focus ring  510  made of quartz or the like is disposed on the ring block  508  and the top surface (on which the substrate W is mounted) of the peripheral portion of the electrode part  501 . The focus ring  510  focuses the plasma on a wafer side in the processing chamber, to thereby make the plasma uniform. Further, the focus ring  510  prevents the ring block  508  and the insulating layer  503  from being damaged due to the plasma. 
     As mentioned above, the introduction channel  505  and the discharge channel  506  for supplying the heat exchange medium to the electrode  501  and discharging it therefrom, respectively, are formed in the transmission path  502 . Hence, as described below, the configuration of the substrate supporting structure  50  is simplified, so that the number of components is reduced, and at the same time, scale-down can be realized. 
     In the conventional substrate supporting structure, the RF introduction path for applying a bias to the mounting table, and the channel for introducing the heat exchange medium into the mounting table or discharging it therefrom are formed individually. Therefore, there is required a space below the mounting table, where respective components are to be disposed. Further, components of the RF introduction path and the heat exchange medium path are needed, respectively, and the number of components is large to thereby make the configuration complicated. Still further, since the size of the entire mounting table should be large, a volume to be cooled is increased, and thus, resulting in deterioration of the cooling efficiency. 
     In the substrate supporting structure  50  in accordance with the first embodiment, the introduction channel  505  and the discharging channel  506  are formed in the transmission path  502 , so that the space for disposing the RF introduction path can be commonly shared for the heat exchange medium path. Accordingly, it is possible to reduce the number of components thereof to thereby simplify the configuration and make the space small, which in turn makes it possible to realize the scaling-down of the substrate supporting structure. For example, as shown in  FIG. 2 , it is possible to make the diameter Da of the support part  52  small, wherein the support part  52  contains the transmission path  502 , the introduction channel  505  and the discharging channel  506 . As a result, it is possible to make the diameter Db of the exhaust chamber  202  small, wherein the exhaust chamber  202  contains the support cover  515 , and thus, realizing the scaling-down of the substrate supporting structure  50 . 
     As for the heat exchange medium, an insulating fluid, e.g., fluorine based fluid (galden) or the like, may be used, since an RF current is applied to the electrode part  501 . Thus, the substrate to be processed is cooled through the mounting table  51  while securing insulation, so that the temperature of the substrate W to be processed can be maintained constant. 
     The substrate supporting structure  50  is fixed to the exhaust chamber  202  by using an attachment ring  221 , ring shaped screw reception rings  220  and  222 , and clamping screws  219 . The attachment ring  221  is of a substantially circular plate shape having in the center thereof a hole, through which the transmission path  502  passes. The attachment ring  221  is fixed to the transmission path  502  by a screw (not shown). The insulating screw reception ring  220  and metallic screw reception ring  222  are disposed between the attachment ring  221  and the support cover  515  such that they apply upward pressure to the support cover  515  by using the clamping screws  219 , which are screwed into screw holes formed in the attachment ring  221 . By clamping power of the clamping screws  219 , the transmission path  502  of the substrate supporting structure  50  is extended downward, i.e., towards the shield cover  205 . Therefore, the transmission path  502  and the electrode part  501 , as a unit, are pressurized to be adhered closely to the plate block  509 , and the plate block  509  is pressurized to be adhered closely to the cover  514 . As a result, the processing space  402  can be kept airtightly by the sealing ring  511  inserted between the electrode part  501  and the plate block  509  and the sealing ring  512  inserted between the plate block  509  and the pedestal cover  514 . 
     As mentioned above, it is possible to apply weight load needed for airtight sealing to the sealing rings  511  and  512  without using a metal screw. Hence, the processing space  402  can be assured to be airtightly kept in a state where there is no metal contamination source present in the processing space  402  where the plasma is excited. 
     Back to  FIG. 3  again, it describes a cross section substantially normal to the cross section shown in  FIG. 2 . As illustrated in  FIG. 3 , in the transmission path  502 , there is formed a gas flow passage  517  for introducing a gas, that transfers heat at a high rate between the surface of the dielectric layer  503  and the substrate W to be processed. During the plasma processing, the heat transfer gas is supplied to improve the thermal conductivity between the mounting table  51  and the substrate W to be processed, thereby efficiently cooling the substrate W to be processed. Further, as described above, the wiring  516  is disposed in the transmission path  502  to be extended therein while being insulated and is connected to a DC power supply (not shown) disposed outside the processing chamber  20 . The substrate W is electrostatically adsorbed by applying a voltage to the electrode  504  of the electrostatic chuck disposed on the mounting table  51  through the wiring  516 . 
       FIG. 4  is a cross sectional view showing a magnified X part shown in  FIG. 3 . As shown in  FIG. 4 , the gas flow passage  517  communicates with a plurality of grooves  517 A formed on the surface of the mounting table  51 . The heat transfer gas, e.g., Ar, He or the like, is introduced into the grooves  517 A through the gas flow passage  517 . The electrode  504  of the electrostatic chuck is made of metal, e.g., W or the like. The electrode  504  is embedded between the upper and lower dielectric layers  503  and  518  made of, e.g., a thermally sprayed film of Al 2 O 3  or the like. 
       FIG. 5  is a cross sectional view showing a magnified Z part shown in  FIG. 4 . As illustrated in  FIG. 5 , the wiring  516  is made of a metal, e.g., Ti or the like. The wiring  516  is introduced into an insertion hole  501   a  of a diameter La which is formed on the electrode part  501 . A ring  501   b  made of Al is disposed in the insertion hole  501   a  by, e.g., beam welding, and the wiring  516  is attached to a hole formed in the ring  501   b.    
     The wiring  516  has a bar-shaped wiring portion  516   a . On the bar-shaped wiring portion  516   a , there is formed a block-shaped step portion  516   b  having a diameter larger than that of the wiring portion  516   a . On the step portion  516   b , there is formed a block-shaped step portion  516   c  having a diameter smaller than that of the step portion  516   b . Further, on the step portion  516   c , there is formed a block-shaped step portion  516   d  having a diameter smaller than that of the step portion  516   c . At sidewalls of the step portions  516   b ,  516   c  and  516   d , and parts of the step portions  516   b  and  516   c  which face the electrode  504 , an insulating film  516   i  of thickness of 500 μm is formed by, e.g., Al 2 O 3  thermal spraying. In case of applying a DC voltage to the electrode  504 , the DC voltage introduced to the wiring  516  is applied through the step portion  516   d  that is making a contact with the electrode  504 . 
     The space of the insertion hole  501   a  between the wiring  516  and the electrode part  501  is filled with insulating layers  516   f  and  516   e  made of, e.g., an insulating resin, so that the wiring  516  is isolated from the electrode part  501 . The insulating layers  516   f  and  516   e  and the wiring  516  are fixed to the electrode part  501  by using, e.g., an epoxy-based adhesive. 
       FIG. 6  is a transversal cross sectional view taken along Y-Y line indicated in  FIG. 2 . As illustrated in  FIG. 6 , the introduction channel  505  and the discharging channel  506  are formed in the transmission path  502 . The introduction channel  505  and the discharging channel  506  are surrounded by thermal insulators  505 A and  506 A, e.g., a thermally insulating tube, to increase thermal insulating effect between the heat exchange medium and the transmission path  502 . Preferably, the thermal insulators  505 A and  506 A may be made of a material having low thermal conductivity, e.g., a fluorine based resin such as Teflon, Vespel or the like. The reason is as follows. 
     If the plasma processing is performed on the substrate to be processed in the processing chamber, heat is generated from the plasma. Hence, the heat exchange medium of low temperature, which is supplied into the temperature control space  507  through the introduction channel  505 , is heated to a high temperature and will be discharged through the discharge channel  506 . At this time, if heat is exchanged between the introduction channel  505  and the discharge channel  506  in the transmission path  502 , cooling efficiency of the electrode part  501  will be deteriorated. If the introduction channel  505  and the discharge channel  506  are surrounded by the thermal insulators  505 A and  506 A, the heat from the discharge channel  506  is prevented from being transferred to the introduction channel  505 , thereby efficiently cooling the substrate W to be processed. 
     As described above, the introduction channel  505 , the discharge channel  506 , the gas flow passage  517  and the DC voltage introduction wiring  506  are all disposed within the transmission path  502 . Therefore, the substrate supporting structure becomes small and the number of components is reduced, thereby simplifying the structure and realizing the production cost reduction. 
     The outline of a method for processing the substrate W is as follows. First, the substrate W is supported by the substrate supporting structure  50 . Subsequently, a processing gas is supplied into the processing space formed in the processing chamber  20  from the gas supply unit  30 . Further, the processing gas turns into a plasma by the excitation mechanism  40  to perform a plasma processing on the substrate W. 
     Specifically, first, the gate valve for transfer  208 , which is formed in the processing chamber  20 , is opened to load the substrate W to be processed which will mounted on the electrode part  501 . Thereafter, the gate valve  208  is closed and the processing space  402  is exhausted through the gas exhaust port  218  to be depressurized to be kept at a predetermined pressure. 
     Subsequently, the valves  304  and  302  are opened, and Ar gas is supplied form the Ar gas supply source  305  into the processing space  402  while the flow rate thereof is controlled by the mass flow controller  303 . In the same manner, the valves  309  and  307  are opened, and H 2  gas is supplied form the H 2  gas supply source  310  into the processing space  402  while the flow rate thereof is controlled by the mass flow controller  308 . Thereafter, an RF power from the RF power supply  403  through the matching unit  405 , e.g., RF matching network, is supplied to the coil  404  to excite an inductively coupled plasma in the bell jar  401 . 
     For example, in the manufacturing process of the semiconductor device, the plasma processing device  10  may be used in a processing for removing an impurity layer containing an oxide film formed on a metal film formed on the substrate to be processed, or an oxide film such as a native oxide film formed on a silicon. By removing such an impurity layer, adhesivity between a film to be formed thereafter and an underlayer may be improved, or sheet resistance of a film to be formed may be lowered. 
     Specific conditions under which the impurity layer is removed are given as follows. For example, the pressure is in the range of 0.1˜13.3 Pa, and preferably, 0.1˜2.7 Pa. The temperature of the wafer is 100˜500° C. As for the flow rate of gas, that for Ar gas is 0.001˜0.03 L/mim; and that for H 2  gas is 0˜0.06 L/min, and preferably, 0˜0.03 L/min. The frequency of the RF power supply  403  is in the range of 450 kHz˜60 MHz, and preferably, 450 kHz˜13.56 MHz. The power of the bias RF power supply is within the range of 0˜500 W, and bias potential is in the range of −20˜−200 V. By performing the plasma processing for about 30 seconds under such conditions, e.g., a silicon oxide film (SiO 2 ) is removed by about 10 nm. 
     Further, in case of removing a metal oxide film, e.g., Cu 2 O, specific conditions therefore are as follows. The pressure is within the range of 3.99×10 −2 ˜1.33×10 −1  Pa. The temperature of the wafer is in the range of 0˜200° C. As for the flow rate of gas, that for Ar gas is in the range of 0.001˜0.02 L/min, and preferably, 0.001˜0.03 L/min; and that for H 2  gas is in the range of 0˜0.03 L/min, and preferably, 0˜0.02 L/min. The frequency of the RF power supply  403  is in the range of 450 kHz˜60 MHz, and preferably, 45 kHz˜13.56 MHz. The power of the bias RF power supply is in the range of 50˜300 W, and the bias potential is in the range of −150˜−25 V. By performing the plasma processing for about 30 seconds under such conditions, e.g., a Cu 2 O film is removed by about 20˜60 nm. 
     Still further,  FIG. 9  shows the ranges of the frequencies of the plasma excitation RF and the bias RF and respective powers thereof, in the aforementioned process. Still further, in case of the bias RF, the range of the bias potential is also shown. 
     The substrate supporting structure  50  is not limited to those shown in  FIGS. 2˜6 , and it may be variously modified and changed.  FIGS. 7A and 7B  are partial cross sectional views of the substrate supporting structure in accordance with a modified example of the first embodiment. 
     In a substrate supporting structure  62  shown in  FIG. 7A , the dielectric layer  503  is formed only in a region that is not covered with the focus ring  510  on the top surface (to which the substrate W is contacted) of the electrode part  501 . As mentioned above, the part, in which the dielectric layer is formed, becomes simplified, so that the number of processings of, e.g., ceramic spraying, is reduced, and thus, lowering the production cost. Namely, the dielectric layer can be easily formed by such a method that ceramic powders are supplied into the plasma of an atmospheric pressure or vacuum to perform a plasma spraying coating on an object. Further, as described above, it is possible to variously change an area or a shape of the electrode part  501  to be coated with the dielectric layer, if necessary. 
     In a substrate supporting structure  64  shown in  FIG. 7B , a focus ring  510 A is thinner than the focus ring  510  of the substrate supporting structure  50 . The height of the top surface (to which plasma is exposed) of the focus ring  510 A coincides with that of the dielectric layer  503 . In this case, specifically, non-uniformity in the bias potential in the vicinity of edge of the substrate W is improved. As a result, an improvement in the uniformity in a sputter etching rate of in-surface of the substrate W can be realized. 
     Further, a material of the focus ring may be changed to change permittivity thereof. In this case, since the bias potential in the vicinity of the wafer edge is changed, the in-surface uniformity in a sputter etching rate may be improved. 
       FIG. 8  is a graph showing measurement results of the self-bias potential, in case where a high frequency power is applied to the mounting table. Herein, in the plasma processing device  10  having the substrate supporting structure  50  mounted thereon in accordance with the first embodiment, an RF power was applied to the substrate supporting structure  50 , and a self-bias voltage Vdc was measured at the substrate supporting table. Further, for comparison, the voltage Vdc for the conventional substrate supporting structure was measured. In the conventional substrate supporting structure, the RF transmission path was thin compared to the substrate supporting structure  50 , and a coaxial structure as described above was not formed. 
     As for conditions of Vdc measurement, the flow rate of Ar gas was 2.9 sccm. The pressure in the processing chamber was 0.5 mTorr. The temperature of the mounting table was room temperature (about 20˜30° C.) in case of using the substrate supporting structure  50 ; and it was 200° C. in the conventional case. The plasma density was set at 2.5×10 10  atoms/cm 3 . For this, the RF power for plasma excitation was 1000 W in case of using the substrate supporting structure  50 ; and it was 800 W in the conventional case. 
     As illustrated in  FIG. 8 , Vdc of the substrate supporting structure  50  in accordance with the first embodiment was higher, compared to the conventional case. For example, if the RF power applied to the mounting table was 300 W, Vdc was 126 V in the conventional case, and 162 V in case of using the substrate supporting structure  50 , corresponding to a potential of about 1.3 times. 
     The reason may be conjectured that, in the substrate supporting structure  50  in accordance with the first embodiment, the RF power is efficiently transferred by the coaxial structure using the transmission path  502  as a central conductor. Another reason may be considered that the introduction channel, the discharge channel, the DC wiring, the heat transfer gas path and the like are all disposed within the RF transmission path  502 , to thereby, lower impedance of the RF. That is, in the latter case, while the entire substrate supporting structure becomes small, the surface area of the transmission path  502  increases, and thus, lowering impedance of the RF. 
     Second Embodiment 
     In the aforementioned plasma processing device  10 , if the metal oxide formed on the surface of metal, e.g., copper, aluminum or the like, is etched, metal removed from the substrate W to be processed is scattered. Scattered metal is deposited onto the top surface of the insulating focus ring  510  around the substrate W to be processed, and thus, forming a metal film. If the metal film is grown, a discharge path may be formed between the substrate to be processed (semiconductor wafer) W and the conductive cover (pedestal conduction layer)  514 , which is grounded, through the metal film. In this case, since charged particles on the metal film flow on the cover  514  as a current, there may be incurred a loss of the RF power supplied to the electrode part  501 . For the same reason, the processing efficiency is lowered and the processing uniformity is deteriorated due to a decrease in the self-bias or abnormal discharge in the discharge path. 
     Further, an electromagnetic configuration on the surface of the mounting table  51  may be seriously changed due to the formation of a metal film. In this case, the change due to the aging of the plasma state on the mounting table  51  may occur, and reproducibility of processing will be deteriorated. Further, if a conductive metal film is formed in the focus ring  510 , the situation becomes practically same as the case where a lower electrode has an area larger than the substrate W to be processed. In this case, the self-bias is lowered; the etching rate is lowered; and hence, the processing uniformity (inter-surface uniformity) between plural substrates to be processed is deteriorated. 
     A second embodiment relates to a plasma processing device for resolving the aforementioned problems. Thus, a device in accordance with the second embodiment has an effective configuration for a case when processing a substrate having a conductive film. As for such a processing, there may be enumerated a processing for removing an oxide film formed on a surface of, e.g., Cu, Si, Ti, TiN, TiSi, W, Ta, TaN, WSi, poly-Si or the like. 
       FIG. 10  is a configuration diagram showing a plasma processing device including a substrate supporting structure for semiconductor processing in accordance with the second embodiment of the present invention. 
     As shown in  FIG. 10 , a plasma processing device  70  has a cylindrical processing chamber  710  in which a mounting table  720  is disposed. The processing chamber  710  is connected to a gas supply unit  740  for supplying a processing gas thereinto. To a gas exhaust port  711   c  formed in the center of bottom portion of the processing chamber  710 , there is airtightly connected a substantially cylindrical exhaust chamber  711 B, which is downwardly protruded. In the same manner as in the first embodiment, a support  730  for supporting the mounting table  720  is concentrically disposed in the exhaust chamber  711 B. 
     An exhaust unit (not shown) having a vacuum pump and the like is coupled to a sidewall of the exhaust chamber  711 B through a gas exhaust line  716 . By the exhaust unit, an inside of the processing chamber  710  is exhausted, and at the same time, it is set to be kept at a predetermined vacuum pressure, e.g., in the range of 0.1 mTorr˜1.0 Torr. 
     The processing chamber  710  is formed by combining a conductive cylindrical lower vessel  711  with an insulating cylindrical upper vessel or a bell jar  712 . The lower vessel  711  is made of a metal (conductor), e.g., aluminum, alloy thereof or the like. The bell jar  712  is made of an insulator, e.g., glass, ceramic (Al 2 O 3 , AlN) or the like. 
     Around the bell jar  712 , an induction coil  713  is wound. The induction coil  713  is connected to an RF power supply  751  through a matching unit  752 . From the RF power supply  751 , an RF power of, e.g., 450 kHz is supplied to the coil  713 , so that an induced electromagnetic field is formed in the bell jar  712 . Further, the lower vessel  711  and the coil  713  are grounded. 
     Between the lower vessel  711  and the bell jar  712 , a gas supply ring  714  is airtightly formed with a sealing material such as O-ring or the like. The gas supply ring  714  is connected to a gas source  741  (e.g., Ar gas) and a gas source  742  (e.g., H 2  gas) of the gas supply unit  740 , through valves and flow meters. The gas supply ring  714  has plural gas inlet openings disposed equi-spacedly around the processing chamber  710 . The gas inlet openings uniformly discharge a processing gas (plasma generation gas) supplied from the gas supply unit  740  towards the center of the bell jar  712 . 
     At a sidewall of the lower vessel  711 , there is formed an opening  711   a , in which a gate valve  715  is disposed. While the gate valve  715  is opened, the substrate W to be processed can be loaded into the processing chamber  710  and unloaded therefrom. 
     On a top portion of the bell jar  712 , an upper electrode  717 , which is grounded, is disposed to face in the direction toward the mounting table  720 . The upper electrode  717  is made of a conductive material such as aluminum, which is alumite processed. The upper electrode  717  serves as an electrode facing toward a lower electrode disposed on the mounting table  720 , and functions to prevent any failure of plasma ignition and to facilitate easy ignition. The upper electrode  717  fixes and assists the bell jar  712  through buffer members (plural pads, which are equi-spacedly disposed)  717   a  made of, e.g. a resin and the like. 
     An electrode part (lower electrode)  721  is disposed on the mounting table  720 . The lower electrode  721  is coupled to an RF power supply  753  through an RF transmission path  731  in the support  730 , a matching unit  754  and the like. From the RF power supply  753 , an RF power of, e.g., 13.56 MHz is supplied to the lower electrode  721 , and a bias potential is applied to the substrate W to be processed. Further, the lower electrode  721  and the transmission path  731  are molded as a unit in the same manner as in the first embodiment. 
     In the lower electrode  721 , there is formed a heat exchange medium channel (temperature control space)  721   a  as a flow path for flowing a heat exchange medium, e.g., an insulating cooling fluid, for adjusting the temperature of the mounting table  720 . Meanwhile, in the transmission path  731  of the support  730 , there are formed introduction channel  735  and discharge channel  736  for supplying the heat exchange medium in the temperature control space  721   a  and discharging it therefrom. 
     The introduction channel  735  and the discharge channel  736  are coupled to a circulation unit CU, e.g., a chiller or the like, which functions to control temperature. The heat exchange medium is circulated from the circulation unit CU to the temperature control space  721   a  of the mounting table  720  through the introduction channel  735  and the discharge channel  736 , so that the temperature of the mounting table  720  is maintained at a predetermined temperature. For example, the substrate W to be processed is controlled to be kept at a predetermined temperature in the range of −20˜10° C. Instead of the temperature control space  721   a , any temperature control means may be provided in the mounting table  720 . For example, a resistance heater may be built in the mounting table  720 . 
     The lower electrode  721  is covered with a dielectric layer (insulating layer)  722  such as alumina or the like, to be insulated from surroundings. The dielectric layer  722  forms a mounting surface of the mounting table  720  for mounting thereon the substrate W to be processed. An electrode  723  is inserted in the dielectric layer  722  of the mounting surface to form an electrostatic chuck therewith. The electrode  723  is connected to a DC power supply  755  disposed outside the processing chamber  720  through a wiring  737 , which extends through the transmission path  731  while being insulated. By applying a voltage to the electrode  723 , the substrate W to be processed is electrostatically adsorbed on the mounting table  720 . 
     Side and bottom surfaces of the lower electrode  721  are covered with an insulating layer  725  made of an insulating material such as quartz and the like. A part of the lower and side surfaces of the insulating layer  725  is also covered with a cover  726  made of a conductive material such as Al and the like. The lower electrode  721 , the insulating layer  725  and the conductive cover  726  are coaxially configured. 
     Meanwhile, the transmission path  731  of the support  730  is coated with an insulating layer  732 . The insulating layer  732  is also made of a conductive material such as Al and the like; electrically connected to the conductive cover  726 ; and coated with a cover  733  that is grounded. The transmission path  731 , the insulating layer  732  and the conductive cover  733  are coaxially configured. 
     Namely, the substrate supporting structure in accordance with the second embodiment also is coaxially configured such that the mushroom shaped conductive cores  721  and  731  connected to the RF power supply for the bias  753  are covered with the insulating layers (dielectric layers)  725  and  732 , and also, covered with the conductive covers  726  and  733  that are grounded. Since the conductive covers  726  and  733  are grounded, charges flow to the ground even though an induced electromagnetic field is formed in the covers  726  and  733 . For the same reason, a plasma is not produced in an exhaust space below the mounting table  720  when the RF power is applied to the lower electrode  721 . By such a configuration, the loss of the RF power is reduced, and the bias can be applied efficiently and stably to the substrate to be processed. 
     At an upper outer periphery of the mounting table  720 , there is disposed a conductive ring-shaped extension member  727  surrounding the substrate W to be processed. The extension member  727  has an exposed top surface in parallel with that of the substrate W to be processed (preferably, heights thereof are equal to each other) when the substrate W to be processed is mounted on the mounting table  720 . The extension member  727  is insulated from the electrode  721  by the dielectric layer  722 . Further, the extension member  727  is insulated from the conductive cover  726  by the insulating layer  725  or by having a sufficiently wide gap. In the second embodiment, the extension member  727  is insulated from all neighboring members, to which a potential is supplied. In other words, the extension member  727  is in a floating state where no potential is supplied. 
     It is preferable that the conductive extension member  727  is configured to totally surround the periphery of the substrate W to be processed. The extension member  727  is formed of various conductive materials such as metal, e.g., titanium, aluminum, stainless steel or the like, or low resistance silicon. Preferably, the extension member  727  is formed of titanium or alloy thereof that hardly produces particles and the like due to the peeling of conductor. Alternatively, the surface of the extension member  727  may be coated with titanium or alloy thereof. 
     Outside the processing chamber  720 , a driving source  761  formed of an electric motor, a fluid pressure cylinder and the like is disposed. The driving source  761  raises and lowers a plurality of lift pins  763  through a driving member  762 . By elevation of the lift pins  763 , the substrate W to be processed is elevated from the mounting surface of the mounting table  720 . By this, the lift pins  763  assists the substrate W to be transported to the mounting table  720 . 
       FIG. 11  is a schematic configuration view showing a configuration of a main part of the plasma processing device shown in  FIG. 10 . The plasma processing device  70  includes a conductive sealing box  719  coupled to the lower vessel  711  to cover the upper side thereof. The bell jar  712  and the induction coil  713  are accommodated in the sealing box  719 . The sealing box  719  is grounded, which functions to shut off any plasma emission (Ultra Violet or the like) or electromagnetic field. Further, the upper electrode  717  is supported by a member  718  in an upper part of the sealing box  719 . 
     In the aforementioned plasma processing device  70 , a processing gas (e.g., gaseous mixture of Ar gas and H 2  gas) from the gas supply unit  740  is introduced into the processing chamber  710  through the gas supply ring  714 . At this time, the processing chamber  710  is exhausted through the exhaust chamber  711 B and the gas exhaust line  716 ; and it is set to be maintained at a predetermined pressure (vacuum), e.g., in the range of 0.1 mTorr˜1.0 Torr. In such a state, an RF power, e.g., in the range of 100˜1000 W, is applied to the induction coil  713 . By this, the processing gas turns into a plasma in the bell jar  712 , and a plasma region (P) is formed above the substrate W to be processed (see  FIG. 10 ). 
     If an RF power is supplied to the electrode  721  of the mounting table  720 , a self-bias voltage is generated. By such a self-bias voltage, ions in the plasma are accelerated to collide with the surface of the substrate W to be processed, and etching is carried out. 
     In the plasma processing device  70 , a metal or an metal oxide on the surface of the substrate W to be processed, e.g., an oxide film on the surface of Cu, Si, Ti, TiN, TiSi, W, Ta, TaN, WSi, poly-Si or the like, is etched. In this case, as mentioned above, the metal is scattered from the substrate W to surroundings, so that a metal film may be formed in the surroundings. However, in the second embodiment, the aforementioned metal film is formed mainly on the exposed surface of the extension member  727 . 
       FIG. 12  is a magnified partial cross sectional view showing that a metal film M is formed on the extension member  727 , in the plasma processing device shown in  FIG. 10 . As illustrated in  FIG. 12 , a gap  728  for sufficiently insulating the discharge path is formed between the extension member  727  and the conductive cover  726 . For the same reason, even though the metal film M is formed on the extension member  727 , an electromagnetic environment at the outer periphery of the mounting table  720  is hardly changed. Namely, even though the metal film M is formed on the extension member  727 , currents does not flow to the ground, and an electrode area is not changed. Moreover, there is no problem that the discharge path is formed at the outer periphery of the mounting table  720 , or abnormal discharge occurs. 
     Further, since the conductive extension member  727  is sufficiently insulated from periphery members by the insulating layer  725 , there will be no current flow generated by the RF power supplied to the electrode  721  through the extension member  727 . Therefore, waste of processing power of the device resulting from a drift of the self-bias becomes reduced. 
     Namely, in the second embodiment, the conductive extension member  727  is disposed from the beginning, expecting the formation of the metal film M, so that electromagnetic situation around the substrate W is hardly changed although the metal film M is formed. Accordingly, the uniformity (inter-surface uniformity) in a processing performed on plurality of substrates can be improved, since the plasma is uniformly produced on the substrate. 
     One of the electromagnetic considerations is related with the insulation between the extension member  727  and the conductive cover  726 . If the upper portion of the cover  726  of the mounting table is close to the extension member  727 , a leakage in the power applied to the electrode  721  is increased and the processing cannot be performed efficiently and stably. In the configuration shown in  FIG. 12 , a sufficiently long distance S through the gap  728  between the cover  726  and the extension member  727  is secured. 
     Specifically, in the second embodiment, it can be configured that impedance Z 2  (a distance S between the extension member  727  and the cover  726 ) between the extension member  727  and the cover  726  is greater than impedance Z 1  (a thickness of the insulating layer  725 ) between the lower electrode  721  and the cover  726 . These impedance values are obtained by using as a reference frequency the RF applied to the lower electrode  721 . By such a configuration, it is possible to reduce (substantially suppress) the current due to the RF power applied to the electrode  721  that flows through the extension member  727 . In other words, an impedance change between the electrode  721  and the cover  726  due to the extension member  727  is hardly generated, and the discharge path is hardly formed. 
     Further, as for a method for securing a sufficiently high insulation resistance (impedance) between the conductive cover  726  and the extension member  727 , an insulator (dielectric material) is disposed in the gap  728  such that it can be used to obtain a desired resistance by making a change in permittivity or shape thereof by design. For example, a dielectric material is disposed in the gap  728  indicated by the dotted line in  FIG. 12 , so that substantial permittivity of the insulating material, disposed between the cover  726  and the extension member  727 , is changed. That is, impedance therebetween can be changed by disposing the insulator in the gap  728 , so that Z 2  may be designed to be greater than Z 1 . By doing this, the discharge path is not formed while the processing may be performed stably. 
     Further, in the second embodiment, an exposed surface of the conductive extension member  727  is configured in parallel with the surface of the substrate W to be processed (preferably, heights thereof are equal to each other), so that the surface area of the electrode  721  of the mounting table  720  is substantially increased. Namely, same electromagnetic environment is provided in case where a surface area of the electrode  721  becomes π·(D 2 )2 due to the extension member  727 , compared to the case where the surface area of the electrode  721  is π·(D 1 )2. Herein, D 1  is a radius of the electrode  721  (a radius of simulated circle having the same area as an object); and D 2  is a radius corresponding to an outer peripheral shape of the extension member  727 . 
       FIGS. 13A and 13B  show simplified equivalent circuits of the mounting table  720 , for the cases when the electrode area of the mounting table  720  is assumed to be A 1  and A 2  and respective self-bias voltages are assumed to be V 1  and V 2 . Herein, the electrode areas A 1  and A 2  are π·(D 1 )2 and π·(D 2 )2, respectively, wherein A 1 &lt;A 2 . In this case, following relationship is formed between the electrode area and the self-bias voltage.
 ( V 2/ V 1)=( A 1/ A 2) 4   (Relational equation 1) 
     Namely, as described above, in case when A 1 &lt;A 2 , and hence, V&gt;V 2 , as the electrode area is increased, the self-bias voltage is rapidly decreased. Therefore, if the extension member  727  is not disposed, the processing will proceed and the metal film M will be deposited, so that an effective electrode area of the mounting table will get increased. Accordingly, the self-bias voltage is gradually decreased, and the processing state will be changed. Contrary to this, in the second embodiment, there exists the extension member  727  from the beginning of the substrate processing, as shown in  FIG. 13B . Moreover, although the processing proceeds and the metal film M is adhered, the effective electrode area is hardly changed. Therefore, the self-bias voltage is hardly changed, and the processing can be performed stably. Further, the extension member  727  is configured to be attached to the mounting table  720  and detached therefrom freely, the extension member  727  can be readily replaced. In this case, maintenance of the device may be simply carried out. 
       FIG. 14  is a magnified partial cross sectional view of the plasma processing device in accordance with the modified example of the second embodiment. This modified example has a configuration such that, compared to the configuration shown in  FIG. 12 , the power leakage of the lower electrode  721  is reduced, and at the same time, it is unlikely to make the conductive cover  726  and the extension member  727  have a short circuit due to the metal film of by-product. 
     Specifically, as illustrated in  FIG. 14 , in the relationship between a thickness of the insulating layer  725  and a position of top end of the conductive cover  726 , it is configured to satisfy the relationship of L&lt;T. Here, L means a level difference between the bottom portion of the insulating layer  725  in the side thereof and the top end of the cover  726 . Further, T means the thickness of the insulating layer  725  between the lower electrode  721  and the cover  726 . In other words, in the side of the insulating layer  725 , the top end of the conductive cover  726  is configured to be placed below the bottom portion of the lower electrode  721 . 
     By this, it is possible to control impedances of Z 1  and Z 2 , thereby, improving uniformity of plasma. 
     While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. For example, in the first and second embodiments, the plasma etching device has been explained, but the present invention may be applicable to a plasma film forming device, a plasma ashing device or the like, in the same manner. The substrate to be processed is not limited to a semiconductor wafer, and a glass substrate, an LCD substrate or the like may be employed. 
     In accordance with the present invention, it is possible to provide a substrate supporting structure and a plasma processing device for semiconductor processing capable of realizing a scaling-down to reduce the overall size and reducing cost. 
     Further, in accordance with the present invention, it is possible to provide a plasma processing device capable of increasing at least inter-surface uniformity in a film formed on the substrate to be processed.