Patent Publication Number: US-11398371-B2

Title: Plasma processing apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma processing technique. The present invention also relates to a technique for processing a sample such as a semiconductor wafer while attracting and holding the sample on the upper surface of a sample stage in the processing chamber. 
     2. Description of the Related Art 
     Conventionally, in the plasma processing apparatus, electrostatic attraction (may be described as Electro Static Chuck: ESC, etc.) system is used in order to hold the sample on the upper surface of the sample stage. The sample stage and the electrostatic attraction system generally have the following configuration. The sample stage includes an ESC base metal made of a conductor such as a metal, and a member made of dielectric (may be referred to as a dielectric membrane, a dielectric member, or the like) which constitutes the sample stage upper surface portion on the ESC base metal and has a predetermined thickness. The electrode for electrostatic attraction (may be referred to as an ESC electrode, for example) is disposed in the vicinity of the upper surface of the sample stage (that is, placement surface of the sample) in the sample stage. Electric power from a DC power supply is supplied to this electrode, electric charges are formed inside the dielectric membrane between the electrode and the sample and the sample, and as a result, an electrostatic force is generated between the electric charges. By the electrostatic force, the sample is held by being pressed against and attracted to the upper surface of the dielectric membrane, that is, the placement surface. 
     JP H10-150100 A and JP 2000-507745 A disclose examples of prior art related to the plasma processing apparatus and the electrostatic attraction system. 
     In JP H10-150100 A, a so-called bipolar ESC is disclosed. In the technique of JP H10-150100 A, a corresponding positive or negative DC voltage is applied to each of the plurality of electrodes embedded in the dielectric membrane from two DC power supplies where one output terminal of each DC power supply is grounded through a low pass filter. As a result, each electrode is set to a positive electrode and a negative electrode, and the sample is attracted by using an electrostatic force formed between the positive electrode and the negative electrode and the portion of the upper sample. In this technique, a low pass filter is provided, and the radio frequency power supplied to the ESC base metal from the radio frequency power supply electrically connected to the ESC base metal (that is, bias electrode) below the dielectric membrane of the sample stage is prevented from flowing to the DC power supply. 
     Furthermore, the technique of JP H10-150100 A discloses that the residual attraction of static electricity when the sample attracted on the upper surface of the dielectric membrane of the sample stage is detached upward and removed is suppressed. For that reason, any output terminal of the power supply path to the plurality of electrodes from the DC power supply is not grounded, and positive and negative voltages are directly applied to the electrodes of the positive polarity and the negative polarity from the positive and negative output terminals of the DC power supply completely brought to a floating potential. 
     Also, conventionally, a radio frequency bias technique is used. During the etching process of the sample using plasma, radio frequency power is applied from a radio frequency power supply to the ESC base metal (bias electrode) or the ESC electrode of the sample stage. In this case, a radio frequency bias potential of a predetermined magnitude is formed above the upper surface of the sample stage and above the upper surface of the sample thereon, and a voltage (referred to as a voltage Vdc) which can be regarded as the DC component thereof is generated. 
     SUMMARY OF THE INVENTION 
     In the prior art, since consideration has not been sufficient with respect to the following points, problems have occurred. In recent years, in the process of manufacturing a semiconductor device using a plasma processing apparatus, a multi-step etching process using a radio frequency bias technique and an electrostatic attraction technique or the like has been mainly offered. In this process, the voltage Vdc of the direct-current component of the radio frequency bias potential may fluctuate greatly between steps constituting the process. When this fluctuation occurs, the potential difference between the sample and the sample stage fluctuates, so that the amount of electric charge stored between them varies greatly. In addition, due to the effect of the voltage Vdc, the sum of the magnitudes of the positive and negative potentials of each pole of the ESC electrode does not become 0, and the electric charge induced inside the sample and the dielectric may be unbalanced in some cases. Due to this imbalance, the electrostatic attraction force is unstable. 
     For example, in the conventional etching process, a radio frequency bias potential is formed above the membrane structure in the upper surface of the sample attracted and held on the sample stage having the electrostatic attraction system. A variation of the amount of electric charge stored in the ESC electrode or the like is supplied as a current flowing from the plasma to the sample (sometimes referred to as an ESC current). The magnitude of the ESC current is larger as the amount of change of the voltage Vdc between the multiple steps is larger. Depending on the membrane structure exposed to the plasma, the ESC current may flow in a concentrated manner. When the radio frequency bias power is large between steps, a large ESC current transiently flows to the sample at the time of step change. This may cause damage to the membrane structure. 
     As described above, in the plasma processing apparatus using electrostatic attraction and radio frequency bias, etc. of the prior art example, the membrane structure of the sample may be damaged by the ESC current. In this case, there is a problem that the performance of the semiconductor device manufactured by performing the process using the plasma is impaired and the processing yield is lowered. 
     An object of the present invention is to provide a plasma processing apparatus capable of improving a processing yield. 
     A representative embodiment of the present invention is a plasma processing apparatus characterized by having the following structure. A plasma processing apparatus according to an embodiment includes a processing chamber which is disposed in a vacuum vessel and in which plasma is generated inside the vacuum vessel; a sample stage which is disposed inside of the processing chamber and on which a sample to be processed using the plasma is placed; a dielectric member forming an upper surface portion of the sample stage including a placement surface on which the sample is placed; a plurality of film-shaped electrodes which is disposed at a same height in a vertical direction inside the dielectric member, to which a DC power from a DC power supply is supplied, and which is electrically connected to the DC power supply via a low pass filter circuit including a first and a second low pass filter circuit, to which a DC power from the DC power supply is supplied, to which a predetermined polarity is imparted, and in which an electrostatic force for attracting the sample is formed; and a bias electrode made of a conductor, the bias electrode being disposed below the dielectric membrane in the sample stage and supplied with radio frequency power for forming a radio frequency bias potential from a radio frequency power supply during the processing of the sample, wherein the plurality of electrodes includes a first electrode to which a positive polarity is imparted and a second electrode to which a negative polarity is imparted based on the DC power, wherein the first electrode is electrically connected to a positive electrode terminal of the DC power supply via the first low pass filter circuit, and wherein the second electrode is electrically connected to a negative electrode terminal of the DC power supply through the second low pass filter circuit, and wherein power supply paths of the DC power between the first electrode and the positive electrode terminal of the DC power supply and between the second electrode and the negative electrode terminal of the DC power supply are not electrically connected to ground so that the positive electrode terminal and the negative electrode terminal of the DC power supply, and the plurality of electrodes, are brought into an electrically floating state during processing of the sample. 
     According to a representative embodiment of the present invention, it is possible to provide a plasma processing apparatus capable of improving processing yield. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross-sectional view schematically showing an outline of a configuration of a plasma processing apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a vertical cross-sectional view schematically showing an outline of a configuration example of a membrane structure on an upper surface of a sample in a plasma processing apparatus of an embodiment and a comparative example; 
         FIG. 3  is a vertical cross-sectional view schematically showing the outline of the configuration of a sample stage and an ESC system in the plasma processing apparatus of the first embodiment; 
         FIG. 4  is a graph showing a temporal change of an ESC current flowing into a sample when the membrane structure of  FIG. 2  is processed in the plasma processing apparatus of the first embodiment; 
         FIG. 5  is a graph showing a temporal change of the ESC current in the case where the membrane structure of  FIG. 2  is processed using an ESC system of a first comparative example of  FIG. 17 ; 
         FIG. 6  is a graph showing a temporal change in ESC current in a case where the membrane structure of  FIG. 2  is processed using the ESC system of a third comparative example; 
         FIG. 7  is a graph showing a temporal change in a predicted value and a detected value of a voltage Vdc during the process of  FIG. 6 ; 
         FIG. 8  is a view of an equivalent circuit related to an ESC system and plasma in the first embodiment; 
         FIG. 9  is a graph showing the relationship of Equation 2 using the ratio of the capacitance and the ratio of the ESC current of Equation 2 as parameters in the first embodiment; 
         FIG. 10  is a diagram schematically showing a configuration example of an LPF circuit connected to an ESC electrode in the plasma processing apparatus of the first embodiment; 
         FIG. 11  is a diagram schematically showing another configuration example of an LPF circuit connected to an ESC electrode in the plasma processing apparatus of the first embodiment; 
         FIG. 12  is a vertical cross-sectional view schematically showing a configuration outline of a mounting example of the ESC system in the plasma processing apparatus of the first embodiment; 
         FIG. 13  is a vertical cross-sectional view schematically showing a configuration outline of a sample stage and an ESC system in a plasma processing apparatus according to a second embodiment of the present invention; 
         FIG. 14A  is a vertical cross-sectional view schematically showing a configuration outline of a sample stage and an ESC system in a plasma processing apparatus according to a third embodiment of the present invention; 
         FIG. 14B  is an equivalent circuit of  FIG. 14A ; 
         FIG. 15A  is a vertical cross-sectional view schematically showing a configuration outline of a sample stage and an ESC system in a plasma processing apparatus according to a fourth embodiment of the present invention; 
         FIG. 15B  is an equivalent circuit of  FIG. 15A ; 
         FIG. 16A  is a vertical cross-sectional view schematically showing a configuration outline of a sample stage and an ESC system in a plasma processing apparatus of another comparative example with respect to the fourth embodiment; 
         FIG. 16B  is an equivalent circuit of  FIG. 16A ; and 
         FIG. 17  is a vertical cross-sectional view schematically showing a configuration outline of a sample stage and an ESC system in a plasma processing apparatus of a first comparative example with respect to the embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are attached in principle to the same parts, and a repeated description thereof will be omitted. In the drawings, cross-section hatching may be omitted for the sake of clarity. In the drawings, dimensions, shapes, and the like of the constituent elements are schematically shown as schematic diagrams, and they are not limited to the illustrated dimensions and the like. For the sake of explanation, X direction, Y direction, and Z direction are used as directions. The Z direction is the vertical direction, the height direction, the thickness direction, and the direction in which the center axis of the sample stage or the like extends. The X direction and the Y direction are two directions constituting the horizontal plane and correspond to the radial direction of the sample stage or the like. 
     [Problems and the Like] 
     Prerequisite technologies, problems, etc. will be supplementarily explained below. In the above-described prior art, problems have arisen because consideration on the following points is insufficient. In recent years, in the process of manufacturing a semiconductor device using a plasma processing apparatus, a multi-step etching process using a radio frequency bias technique or an ESC technique is mainly offered in order to process the membrane structure, etc. of the upper surface of a sample such as a semiconductor wafer with higher accuracy. In this multi-step etching process, the process condition is switched for each step of a plurality of steps constituting the process. Processing conditions include conditions for discharge of plasma formed by supplying a gas to the interior of the vacuum vessel and the magnitude of an RF bias potential formed by supplying radio frequency power (RF power) to the sample stage or sample (radio frequency: RF). 
     In such a process, there is a case where the voltage Vdc of the DC component of the RF bias potential due to the RF power varies greatly between steps performed consecutively. For example, in the technical example of JP H10-150100 A, when the voltage Vdc fluctuates, the potential difference between the sample and the sample stage fluctuates, so that the amount of electric charge stored therebetween fluctuates greatly. 
     With reference to  FIG. 17 , the ESC system of the plasma processing apparatus of the comparative example to the embodiment will be described as a prior art example corresponding to the above-mentioned JP H10-150100 A.  FIG. 17  is a vertical cross-sectional view schematically showing the configuration outline of the ESC system and the sample stage of the plasma processing apparatus of the first comparative example. A vertical cross section (X-Z plane) of a sample stage  190  and the like is shown. An ESC system  19  is a bipolar ESC system. In the ESC system  19  of the first comparative example, the sample stage  190  includes a metal ESC base metal  191  and a dielectric membrane (dielectric member)  192  disposed on the upper surface of the ESC base metal  191 . The ESC base metal  191  is a bias electrode to which RF bias electric power from an RF power supply  123  is applied. The dielectric membrane  192  is made of a ceramic material. A state where a sample  4  is placed on the upper surface (that is, a placement surface sf 1 ) of the sample stage  190  and the dielectric membrane  192  is shown. The sample  4  is, for example, a disk-shaped semiconductor wafer. 
     A plurality of electrodes  130 , which is electrodes for the ESC (ESC electrode), is embedded in portion of the dielectric membrane  192 . The electrode  130  is a membrane electrode having a predetermined thickness. The plurality of electrodes  130  has a pair of electrodes composed of an electrode  131  (first electrode) and an electrode  132  (second electrode). One electrode  131  is imparted the positive polarity (+), and the other electrode  132  is imparted the negative polarity (−). The two electrodes  131  and  132  are disposed at the same position in the thickness direction and away from each other with a predetermined distance. 
     The ESC base metal (bias electrode)  191  is electrically connected to a radio frequency power supply (RF power supply)  123  of a predetermined frequency via a matching unit  122 . RF power from the RF power supply  123  is supplied to the ESC base metal  191  during processing of the sample  4  held on the dielectric membrane  192 . By the RF power, an RF bias potential is formed above the upper surface of the sample  4 . 
     The ESC system  19  includes a first DC power supply  134 A and a second DC power supply  134 B (DC: direct current) as two DC power supplies (DC power supplies)  134  disposed outside the sample stage  190 . The two DC power supplies  134  are electrically connected to the corresponding electrodes  131  and  132  via corresponding low pass filters (LPF)  133 , respectively. The LPF  133  includes a first LPF  133 A and a second LPF  133 B. The electrode  131  is connected to the first DC power supply  134 A via the first LPF  133 A. The electrode  132  is connected to the second DC power supply  134 B via the second LPF  133 B. 
     One output terminal of each of the two DC power supplies  134  is grounded, and the other output terminal is electrically connected to the corresponding electrode  131  and  132  via the LPF  133 . The negative electrode terminal of the first DC power supply  134 A is grounded, and the positive electrode terminal is connected to the electrode  131  via the first LPF  133 A. The positive electrode terminal of the second DC power supply  134 B is grounded, and the negative electrode terminal is connected to the electrode  132  via the second LPF  133 B. The DC voltage is supplied from the DC power supply  134  to the electrode  130  via the LPF  133 . As a result, the two electrodes  131  and  132  are imparted different polarities of the positive electrode and the negative electrode. That is, at the time of electrostatic attraction, the electrode  131  functions as a positive electrode to which the positive polarity is imparted, and the electrode  132  functions as the negative electrode to which the negative polarity is imparted. An electrostatic force is generated inside the dielectric membrane  192  and the sample  4  based on the electric charge between the positive electrode  131  and the negative electrode  132 . 
     In the ESC system  19 , in a state where the sample  4  is placed on the placement surface sf 1 , the sample  4  is attracted to the placement surface sf 1  by the electrostatic force formed by using the ESC electrode  130  ( 131 ,  132 ). In this state, processing using plasma is performed on the sample  4 . 
     In such a configuration of the ESC system  19 , the variation in the amount of electric charge stored as ESC by the positive and negative electrodes  131  and  132  is supplied as a current (ESC current) flowing from the plasma to the sample  4 . The magnitude of this ESC current (referred to as J 0 ) is expressed by the following Equation 1. As the amount of change in the voltage Vdc between the steps of the multi-steps increases, a large value of the ESC current flows at the time of step change. In Equation 1, Cesc represents the capacitance of the portion of the dielectric membrane  192  between the ESC electrode  130  ( 131 ,  132 ) and the sample  4 . dVdc/dt represents the time differentiation of the voltage Vdc. 
     
       
         
           
             
               
                 
                   
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     Here, consider the case where a membrane structure  40  on the upper surface of the sample  4  as shown in  FIG. 2  is exposed to plasma during processing of the sample  4  using the ESC system  19  of the first comparative example.  FIG. 2  is a vertical cross-sectional view schematically showing an outline of a configuration example of a membrane structure on the upper surface of the sample  4  to be processed in the embodiment and the comparative example. The membrane structure  40  of  FIG. 2  has a substrate  202 , an insulating film  203 , and a conductor  201  in order from below. The conductor  201  has a portion A (membrane portion  201 A) and a portion B (through hole portion  201 B). 
     The ratio (antenna ratio) between the surface area of the portion A (membrane portion  201 A) facing the plasma and the area of the portion B (through hole portion  201 B) in the through hole in the conductor  201  is examined. When the antenna ratio is larger than a predetermined value, the ESC current concentrates in the portion B (through hole portion  201 B) and may damage the membrane structure  40   
     In the technique of JP H10-150100 A, any output terminal of the DC power supply is brought to a floating potential. Therefore, even when the voltage Vdc fluctuates, the potentials of the ESC electrode and the DC power supply fluctuate so that a large current does not flow in the DC power supply. Therefore, even when the voltage Vdc fluctuates between the steps of the multi-steps, it is expected that a large ESC current does not flow in the sample. However, in this technique, both output terminals of the DC power supply are directly connected to the positive electrode and the negative electrode of the ESC electrode. Therefore, when the RF power for forming the RF bias is supplied to the sample stage, the RF power leaks to the DC power supply and flows. As a result, the DC power supply generates heat and, in turn, a failure occurs. 
     JP 2000-507745 A describes a technical example relating to prevention of instability of electrostatic attraction force of the ESC. In the technique of JP 2000-507745 A, positive and negative voltages are applied via a radio frequency filter to the ESC electrode from a DC power supply whose output terminals are not grounded. Further, the voltage Vdc predicted from the magnitude of the amplitude of the radio frequency voltage (referred to as a voltage Vpp) generated on the sample stage is connected to the output terminal of the DC power supply via the resistor circuit. The predicted potential of the voltage Vdc is set to be the intermediate potential between both output terminals of the DC power supply. As a result, the electric power supplied to the ESC electrode is adjusted depending on the variation of the voltage Vdc to adjust the amount of electric charge to be generated. 
     In the technique of JP 2000-507745 A, prediction of the voltage Vdc is an issue. According to the study of the present inventors, the value of the voltage Vdc does not necessarily have a constant correlation with the value of the voltage Vpp. Therefore, practically, it is difficult to accurately predict the value of the voltage Vdc from the value of the voltage Vpp. Furthermore, there is a time lag between the change (temporal change) in the voltage Vpp with respect to time and the temporal change in the voltage Vdc. Therefore, if inclusive of the transient state, prediction of fluctuation in the voltage Vdc is even more difficult. 
     Furthermore, also in the configuration of the first comparative example ( FIG. 17 ), when the magnitude of the RF bias power is larger than the predetermined value between temporally consecutive steps, a large ESC current transiently flows into the sample  4  at the time of step change. Therefore, when there is a membrane structure  40  having a large antenna ratio as described above, the sample  4  is damaged. As a result, the performance of the semiconductor device manufactured by performing the process using the plasma is impaired, and there is a problem that the processing yield is lowered. Such a problem has not been considered in the prior art example. The plasma processing apparatus according to the first embodiment has a configuration including an ESC system devised in consideration of the above problem. This improves the processing yield. 
     First Embodiment 
     A plasma processing apparatus according to a first embodiment of the present invention will be described with reference to  FIGS. 1 to 12 . The plasma processing apparatus according to the first embodiment includes a sample stage disposed below the inside of the processing chamber and on which a sample is placed, a dielectric member forming an upper surface portion of the sample stage, a plurality of electrodes (ESC electrodes) for electrostatic attraction (ESC) which is disposed in the dielectric member, and to which DC power is supplied from a DC power supply and is imparted a predetermined polarity to form an electrostatic force for attracting the sample, and a bias electrode (ESC base metal) made of a conductor which is disposed below the dielectric member in the sample stage and to which radio frequency power is supplied from a radio frequency power supply for forming a bias potential during sample processing. The two electrodes (first electrode and the second electrode) of the plurality of electrodes are electrically connected to the positive electrode terminal and the negative electrode terminal of the DC power supply through a low pass filter circuit. 
     [Plasma Processing Apparatus] 
       FIG. 1  is a vertical cross-sectional view schematically showing the configuration outline of a plasma processing apparatus  1  according to the first embodiment. A vacuum vessel  101  and the like are shown in the vertical cross section (X-Z plane).  FIG. 3  shows the configuration of an ESC system  5 , a sample stage  10 , and the like in the plasma processing apparatus  1 . The plasma processing apparatus  1  of the first embodiment is a microwave ECR plasma processing apparatus. The microwave ECR supplies an electric field of a microwave having a predetermined frequency and a magnetic field whose intensity is adjusted according to the frequency to the processing chamber  106  disposed in the vacuum vessel  101  and decompressed, and uses electron cyclotron resonance (ECR) which is generated by the mutual interaction. In this method, plasma is generated by exciting gas for plasma formation supplied to the processing chamber  106  by using ECR, and the film layer to be processed in the sample  4  on the sample stage  10  is etched. The sample  4  is a substrate shaped sample to be processed using plasma and is, for example, a disk-shaped semiconductor wafer. The sample  4  is placed on a sample stage  10  disposed in the lower part of a processing chamber  106  and held by the ESC system  5 . The etching process includes processing of a film layer to be processed in a multilayer membrane structure including a mask on the surface of the sample  4  and a film layer to be processed. 
     The plasma processing apparatus  1  of  FIG. 1  roughly includes the vacuum vessel  101 , an electromagnetic field forming unit  2 , and a vacuum exhaust unit  3 . The vacuum vessel  101  has the processing chamber  106  in which plasma is formed. The vacuum vessel  101  and the like have an axially symmetrical shape such as cylinders or cylinders with respect to the center axis (indicated by the dashed line) in the vertical direction (Z direction). 
     The electromagnetic field forming unit  2  is disposed at the surroundings of the upper portion or the side portion of the upper part of the vacuum vessel  101 , and generates the electric field and the magnetic field of the ECR. The electromagnetic field forming unit  2  is composed of, for example, a magnetron  113 , a plurality of solenoid coils  114 , and the like. 
     The vacuum exhaust unit  3  has an exhaust port  109 , a vacuum pump  102 , an exhaust control valve  108 , and the like. The vacuum pump  102  is disposed below the bottom surface of the vacuum vessel  101  and includes a turbomolecular pump that communicates with the processing chamber  106  through the exhaust port  109  to exhaust the gas. 
     The vacuum vessel  101  has a cylindrical side wall portion  101 A in a part including a portion that surrounds the outer circumference of the processing chamber  106  where at least the plasma is formed. A window member  107  is provided above the upper end portion of the side wall portion  101 A of the vacuum vessel  101  and above the processing chamber  106 . The window member  107  is a disk-like (or columnar) member made of a dielectric material such as quartz through which an electric field is transmitted. The window member  107  has a planar shape of a circle or an approximate circle which can be regarded as a circle in planar view as viewed from the Z direction. The window member  107  is placed on the side wall portion  101 A with a sealing member (not shown) such as an O-ring or the like for hermetically sealing the inside and the outside of the processing chamber  106 , constituting a lid member on the top of the vacuum vessel  101 . 
     A gas introduction pipe  105  is connected to part of the side wall portion  101 A of the vacuum vessel  101 . A gas (processing gas) supplied to the inside in the processing chamber  106  from the upper portion flows in the gas introduction pipe  105 . 
     The sample stage  10  is disposed along the center axis position in the lower part of the inside of the processing chamber  106 . The sample stage  10  has a shape of a circle or an approximate circle which can be regarded as a circle in planar view as viewed from the Z direction, for example, has a columnar shape or a disk shape. The sample  4  is placed on the upper surface of the sample stage  10  through a transfer robot which will be described later. 
     As also shown in  FIG. 3 , the sample stage  10  has an ESC base metal (bias electrode)  11  which is the lower part of the sample stage  10  in the Z direction and a dielectric membrane  12  connected and disposed on the ESC base metal  11 . The ESC base metal  11  has a circular plate or cylindrical shape with a predetermined thickness and diameter, is made of a member made of a conductor such as a metal, and is a bias electrode to which RF power is applied. As in the ESC base metal  11 , the dielectric membrane  12  has a circular or cylindrical shape with a predetermined thickness and diameter, and is made of a substantially film-shaped member made of dielectric (dielectric member) covering the upper surface of the ESC base metal  11 . The dielectric membrane  12  constitutes the upper surface portion of the sample stage  10  and has a placement surface sf 1  on which the sample  4  is placed. A plurality of electrodes  30  is embedded as the membrane ESC electrode in the dielectric membrane  12 . 
     The ESC base metal  11  is electrically connected to a radio frequency power supply (RF power supply)  123  disposed outside the sample stage  10  via the matching unit  122  by a power supply path. The RF power supply  123  outputs a radio frequency power (RF power) of a predetermined frequency. During processing of the sample  4 , the RF power from the RF power supply  123  is supplied to the ESC base metal (bias electrode)  11  via the matching unit  122 . As a result, an RF bias potential is generated above the upper surface of the sample  4  through the ESC base metal  11  and the dielectric membrane  12 . 
     A waveguide  104 , which is a path through which an electric field of microwave propagates through a hollow portion  110 , is disposed above the window member  107 . The magnetron  113 , which oscillates and generates an electric field of microwaves, is disposed at one end of the upper portion (rectangular waveguide portion  104 B) of the waveguide  104 . The waveguide  104  has a circular waveguide portion  104 A and the rectangular waveguide portion  104 B. The circular waveguide portion  104 A extends in the Z direction and has a circular cross section. The rectangular waveguide portion  104 B is disposed and connected above the circular waveguide portion  104 A, and extends in one direction (X direction) in the horizontal direction, and has a rectangular or a squarer cross section. The other end portion of the rectangular waveguide portion  104 B is connected to the upper end of the circular waveguide portion  104 A. The diameter of the circular waveguide portion  104 A is smaller than the diameter of the window member  107 . 
     The hollow portion  110  is provided between the window member  107  and the waveguide  104  (circular waveguide portion  104 A). The hollow portion  110  is a cavity through which the microwave is propagated, has a substantially the same diameter as the vacuum vessel  101  and the window member  107 , and has a cylindrical shape having a predetermined height. The opening at the lower end of the circular waveguide portion  104 A is connected in communication with the opening of the center axis of the top surface portion of the hollow portion  110 . The lower surface of the hollow portion  110  corresponds to the upper surface of the window member  107 . 
     Further, in the electromagnetic field forming unit  2 , solenoid coils  114  wound in a plurality of stages are disposed as the plurality of solenoid coils  114 . The plurality of solenoid coils  114  include a solenoid coil  114  disposed above the top surface portion of the hollow portion  110  and around the side wall of the circular waveguide portion  104 A, and a solenoid coil  114  surrounding the outer periphery of the hollow portion  110 , the window member  107 , and the side wall portion  101 A of the vacuum vessel  101 . DC power is supplied to the solenoid coil  114 , and a magnetic field of a predetermined strength is formed. This magnetic field of the predetermined intensity is a magnetic field of intensity matching the frequency of the microwave that is generated by the magnetron  113  and propagates in the waveguide  104 . 
     The vacuum exhaust unit  3  is provided with the exhaust port  109 , as part of the bottom portion of the vacuum vessel  101 , which is disposed at a position lower than the upper surface of the sample stage  10 . The exhaust port  109  communicates the inside and the outside of the processing chamber  106 , and gas and particles therein are discharged. The exhaust port  109  is connected to the exhaust control valve  108  and the vacuum pump  102  through an exhaust pipe. The vacuum pump  102  is constituted by a turbomolecular pump. The exhaust control valve  108  is disposed on the way of an exhaust pipe connecting the exhaust port  109  and the vacuum pump  102 . The exhaust control valve  108  increases or decreases the flow path cross-sectional area inside the exhaust pipe to increase or decrease the flow rate and speed of the gas or plasma particles passing through the exhaust pipe. A roughing pump such as a rotary pump (not shown) is connected and disposed on the downstream side of the turbomolecular pump of the vacuum pump  102 . This pump serves to discharge the exhausted particles and the like out of a building such as a clean room where the plasma processing apparatus  1  is disposed. 
     A vacuum transfer container is connected to the side wall portion  101 A of the vacuum vessel  101 . The vacuum transfer container is another vacuum vessel (not shown), and has a transfer chamber which is a depressurized space inside. A transfer robot is disposed inside the transfer chamber. The transfer robot includes an arm portion including a plurality of arms rotatably connected at both end portions and configured to be expandable and contractible. The sample  4  is placed on the upper surface of the tip portion of the arm portion of the transfer robot and held and transported. Further, a passage through which the sample  4  placed on the arm portion of the transfer robot is transported inside is disposed on the side wall portion  101 A. At the same time, the side wall portion  101 A is connected to the vacuum transfer container so that the gate, which is the opening of the passage on the transfer chamber side, is airtightly partitioned from the inside and outside including the space around the gate. 
     The sample  4  held at the tip portion of the arm portion of the transfer robot is transported from inside the transfer chamber to above the sample stage  10  in the processing chamber  106  in the vacuum vessel  101  through the gate of the passage. Then, the sample  4  is delivered to the sample stage  10 . Specifically, although not shown in the figure, the sample stage  10  has a plurality of through holes penetrating the ESC base metal  11  and the dielectric membrane  12 , and a plurality of pusher pins disposed in the plurality of through holes. Upon delivery, a plurality of pusher pins is driven upward to pick up and receive the sample  4  held at the tip portion of the arm portion of the transfer robot. Thereafter, the arm portion of the transfer robot contracts and retreats from the processing chamber  106  into the transfer chamber. As a result, the sample  4  is delivered to the sample stage  10 . Thereafter, in a state where the sample  4  is placed on the tip portion of the plurality of pusher pins, the plurality of pusher pins is driven downward and stored in the through hole. Then, the sample  4  is placed on the upper surface of the dielectric membrane  12  of the sample stage  10  (placement surface sf 1 ). 
     In this state, the DC power from the DC power supply  34  is supplied to the ESC electrode  30  disposed in the dielectric membrane  12 , and an electrostatic force is generated. By the electrostatic force, the sample  4  is attracted to and held on the upper surface of the dielectric membrane  12 . 
     At the same time, the processing gas diluted with the rare gas is introduced into the processing chamber  106  through the gas introduction pipe  105 . The pressure inside the processing chamber  106  is controlled by the balance between the flow rate and the speed of the processing gas from the gas introduction pipe  105  and the flow rate and the speed of the exhaust gas from the exhaust port  109 , and is adjusted to a value within the range which is suitable for starting the plasma-generated processing. 
     On the other hand, a microwave electric field of, for example, 2.45 GHz, oscillated by the magnetron  113  propagates through the waveguide  104  and the hollow portion  110 , transmits through the window member  107 , and is supplied into the processing chamber  106 . At the same time, the magnetic field generated by the solenoid coil  114  based on the DC power is supplied into the processing chamber  106 . The ECR is generated by the interaction between the electric field and the magnetic field. By the ECR, atoms or molecules of the processing gas are excited, and ionized or dissociated, and plasma is generated in the discharge space above the sample stage  10  in the processing chamber  106 . 
     Thereafter, the RF power from the RF power supply  123  is supplied to the ESC base metal  11 , and the RF bias potential is formed above the sample  4  held on the upper surface of the dielectric membrane  12  of the sample stage  10 . Charged particles such as ions in the plasma are attracted toward the upper surface of the sample  4  according to the potential difference between the RF bias potential and the plasma. The charged particles collide with the film to be processed in the membrane structure of the sample  4  and the etching process of the film is promoted. 
     [Membrane Structure of Upper Surface of Sample] 
       FIG. 2  shows a configuration example of a membrane structure of the upper surface of the sample  4  to be etched in the plasma processing apparatus  1  of the first embodiment. The membrane structure  40  of  FIG. 2  includes the substrate  202  which can be regarded as a conductor, the insulating film  203  which is connected to and disposed on the upper surface of the substrate  202 , and a conductor  201  which is provided on part of the insulating film  203 . The conductor  201  has a portion A (membrane portion  201 A) and a portion B (through hole portion  201 B). The portion B (through hole portion  201 B) is a portion with which the through hole penetrating the insulating film  203  in the thickness direction is filled and is in contact with part of the upper surface of the substrate  202 . The portion A (membrane portion  201 A) is a part covering part of the upper surface of the insulating film  203  around the opening on the upper end of the through hole in the portion B in a film shape. 
     [ESC System] 
       FIG. 3  is a vertical cross-sectional view schematically showing the configuration outline of the sample stage  10  including the ESC system  5  in the plasma processing apparatus  1  according to the first embodiment. The X-Z plane of the sample stage  10  and the like is shown. The X direction is one direction in the radial direction with respect to the center axis (Z direction). 
     In the plasma processing apparatus  1  according to the first embodiment, the ESC system  5  is mainly configured in the upper portion of the sample stage  10  (including the placement surface sf 1  which is the upper surface of the dielectric membrane  12 ). The ESC system  5  includes a plurality of electrodes  30  in the dielectric membrane  12 , a low pass filter (LPF)  33  electrically connected to each of the plurality of electrodes  30  through a power supply path (electrical wiring), and a direct current power supply (DC power supply)  34  electrically connected to the LPF  33  through a power supply path. 
     The dielectric membrane  12  is a dielectric member made of a ceramic material such as aluminum oxide or yttrium oxide disposed to cover the upper surface of the upper part of the ESC base metal  11 . The sample stage  10  and the dielectric membrane  12  have a placement surface sf 1 , which is an upper surface, and the sample  4  is placed on the placement surface sf 1 . 
     The plurality of electrodes  30 , which is the ESC electrode, is a plurality of film-shaped electrodes made of metal such as tungsten where the electrodes  30  are embedded in portion of the dielectric membrane  12 . The plurality of electrodes  30  has a pair of electrodes composed of an electrode  31  (first electrode) and an electrode  32  (second electrode). The plurality of electrodes  30  is disposed at the same position (predetermined position z 1 ) in the thickness direction (Z direction) and is disposed away from each other at a predetermined distance in the X direction. The film of the electrode  30  has a predetermined thickness (distance in the Z direction). Different polarities (positive polarity, negative polarity) are imparted to the plurality of electrodes  30  by the supply of the DC voltage from the DC power supply  34 . At the time of the ESC, the positive polarity is imparted to the electrode  31  and the negative polarity is imparted to the electrode  32 . Each of the plurality of electrodes  30  is connected to a terminal of a corresponding polarity (positive electrode terminal, negative electrode terminal) of the DC power supply  34  via the LPF  33 , and is imparted respective polarities. 
     The LPF  33  includes a first LPF  33 A and a second LPF  33 B. The electrode  31  is connected to the positive electrode terminal of the DC power supply  34  in an electrode-like manner via the first LPF  33 A. The electrode  32  is connected to the negative electrode terminal of the DC power supply  34  in an electrode-like manner via the second LPF  33 B. 
     In the first embodiment, the two output terminals (positive electrode terminal and the negative electrode terminal) of the DC power supply  34  are not grounded, and are brought to an electrically floating potential at least during the processing of the sample  4 . Also, at least during the processing of the sample  4 , each of the electrodes  30  (electrodes  31 ,  32 ) is also brought to an electrically floating potential. 
     The dielectric membrane  12  includes, as a schematic part, in the Z direction, a portion including the plurality of electrodes  30  (a portion between the upper surface of the electrode  30  and the lower surface of the electrode  30 ), a first portion P 1  between the upper surface of the plurality of electrodes  30  and the lower surface (placement surface sf 1 ) of the sample  4 , and a second portion P 2  between the lower surface of the plurality of electrodes  30  and the upper surface of the ESC base metal  11 . The first portion P 1  and the second portion P 2  each have a predetermined thickness (distance in the Z direction). 
     In the first embodiment, the dielectric membrane  12  in the sample stage  10  and the ESC base metal  11  below the electrode  30  are, in other words, a bias electrode made of a conductor, to which the RF power for forming the RF bias potential formation is supplied from the RF power supply  123 . 
     The shape and position of the ESC electrode  30  in the X-Y plane of the sample stage  10  in planar view in the Z direction is not particularly limited, but it is, for example, as follows. When viewing the circular region on the upper surface of the sample stage  10  in planar view, one of the positive and negative electrodes  31  and  32  of the plurality of electrodes  30  is disposed in the circular region near the center axis and the other is disposed in the outer peripheral ring region. In another example, the positive and negative electrodes  31  and  32  are each disposed in the inner peripheral ring area and the outer peripheral ring area. In another example, the positive and negative electrodes  31  and  32  are disposed in a double spiral shape. In addition, the positive and negative electrodes  31  and  32  may be separated into a plurality of electrode portions in the circumferential direction. 
     [Etching Process] 
     The etching process of the sample  4  using the plasma processing apparatus  1  including the ESC system  5  and the sample stage  10  as described above will be described below. In the first embodiment, as an example, the membrane structure  40  on the upper surface of the sample  4  in  FIG. 2  is subjected to the etching process. The etching process of the membrane structure  40  of the sample  4  will be described with reference to  FIGS. 4 to 7  and the like. This etching process is a multi-step etching process including the following first step S 1 , second step S 2 , and third step S 3 . In this etching process, the magnitude of the RF bias potential and the like are switched for each step (corresponding process, time). As a result, the voltage Vdc, etc. of the DC component applied to the sample  4  can fluctuate between steps and every step. 
     At the first step S 1  (time T 1  in  FIG. 4 ), a gas in which SF 6  (sulfur hexafluoride) and CHF 3  (trifluoromethane) are mixed is supplied as a processing gas into the processing chamber  106  to form plasma, an RF power of 150 W is supplied to the ESC base metal  11  to form an RF bias potential, and the sample  4  is processed for 30 seconds (s). 
     Next, in the second step S 2  (time T 2 ), a plasma is generated using a processing gas in which Cl 2  (chlorine gas), HBr (hydrogen bromide), and O 2  (oxygen) are mixed, and the RF bias potential by an RF power of 30 W is formed, and the sample  4  is processed for 30 seconds. 
     Furthermore, in the third step S 3  (time T 3 ) which is the final step, plasma is generated using a processing gas in which HBr and O 2  are mixed and using the RF bias potential by RF power of 300 W, the sample  4  is processed for 30 seconds. 
     During the processing of the above plurality of steps, the voltage of the power output from the DC power supply  34  is set to have its amplitude fixed to 1200 V. 
     ESC Current—First Embodiment 
       FIG. 4  shows a graph representing the temporal change in the ESC current flowing into the sample  4  during the process (etching process) in which the above-described plurality of steps is performed when the plasma processing apparatus  1  according to the first embodiment performs the process on the membrane structure  40  of  FIG. 2  using the ESC system  5  and the like of  FIG. 3 . The horizontal axis is the processing time (second (s)), which represents the first step S 1  (time T 1 ), the second step S 2  (time T 2 ), and the third step S 3  (time T 3 ). The vertical axis shows the magnitude of the ESC current with 0 as the center. In the example of  FIG. 4 , although a very small ESC current flows during switching and shifting between steps, no damage to the sample  4  due to this processing is observed. That is, in the plasma processing apparatus  1  of the first embodiment, while the sample  4  is attracted and held by the ESC system  5 , damage to the sample  4  due to the ESC current during the etching process can also be prevented or suppressed. 
     ESC Current—Comparative Example (1) 
     Next, similarly to the membrane structure  40  of  FIG. 2 , the processing of the plurality of steps will be described using the ESC system  19  of the first comparative example of  FIG. 17  instead of the ESC system  5  of the first embodiment of  FIG. 3 . In the configuration of the ESC system  19  of  FIG. 17 , the electrode  131  is made positive and the electrode  132  is made negative based on the DC voltage from the DC power supply  134  during the ESC and the processing. During this processing, the output voltage of the DC power supply  134  is set to have its amplitude fixed to 600 V for both positive and negative. 
       FIG. 5  is a graph showing a temporal change of the ESC current in the case where the membrane structure  40  of  FIG. 2  is processed using the ESC system  19  of the first comparative example of  FIG. 17 . As shown in  FIG. 5 , it can be seen that a large ESC current flows before and after the time at which the processing conditions are changed by switching the preceding and succeeding steps. As a result of investigating the processed sample  4 , it has been acknowledged that the ESC current concentrates on the film-like portion A of the conductor  201  of the membrane structure  40  of  FIG. 2  and the portion B which is in contact with the substrate  202 , and due to the heat generated at this time, the portion B is completely melted and disappears, causing damage. 
     ESC Current—Comparative Example (2) 
     Next, a case where the above-described processing of the plurality of steps is similarly performed on the membrane structure  40  of  FIG. 2  using the bipolar ESC system as the ESC system of the second comparative example will be described. In the ESC system of the second comparative example, corresponding positive and negative voltages are applied to the respective electrodes of the positive electrode and the negative electrode for the ESC electrodes from the DC power supply whose output terminals are not grounded through an RF filter (radio frequency filter). 
     As a result of this processing, RF noise (radio frequency noise) occurred in the first step and the third step where the amplitude of the RF power for forming the RF bias potential is large, and the control system became unstable. In addition, when this process is repeated, the insulation coating between the output terminal of the DC power supply and the power supply housing is heated and burned. 
     ESC Current—Comparative Example (3) 
     Next, a case where the above-described processing of the plurality of steps is similarly performed on the membrane structure  40  of  FIG. 2  using the ESC system of the third comparative example will be described. In the ESC system of the third comparative example, corresponding positive and negative voltages are applied to the respective electrodes of the positive electrode and the negative electrode for the ESC electrodes from the DC power supply whose output terminals are not grounded through an RF filter. At the same time, in the ESC system of the third comparative example, the voltage Vdc predicted from the voltage Vpp is connected to the output terminal of the DC power supply via the resistor circuit. As a result, the predicted potential of the voltage Vdc is set to be the intermediate potential between the two output terminals of the DC power supply. The voltage Vpp is the magnitude of the amplitude of the RF voltage generated on the sample stage due to the supply of the RF power for forming the RF bias potential. The voltage Vdc is a voltage of the DC component generated in the sample  4  with the RF power. During this process, the voltage output from the DC power supply is set to be fixed at 1200 V. 
       FIG. 6  is a graph showing a temporal change of the ESC current in the case where the membrane structure  40  of  FIG. 2  is processed using an ESC system of the third comparative example. It has been found that, as shown in  FIG. 6 , in the first step to the third step, a large ESC current flows on the positive side and the negative side at the timing when the processing conditions change as the steps are switched. 
     Further,  FIG. 7  is a graph showing the temporal change in the predicted value of the voltage Vdc and the detected value (actually measured value) of the actual voltage Vdc during the process of  FIG. 6 . The vertical axis represents the voltage Vdc (V). The solid line indicates the detected value (measured value), and the broken line indicates the predicted value. As shown in  FIG. 7 , the ratio between the voltage Vpp and the voltage Vdc changes greatly depending on the conditions such as the potential value of the plasma during the processing. Therefore, the predicted value of the voltage Vdc obtained simply by multiplying the voltage Vpp by the coefficient does not match the actual voltage Vdc. That is, simple prediction of the voltage Vdc from the voltage Vpp is difficult. Further, from  FIG. 7 , it can be seen that there is a delay in the temporal change in the actual voltage Vdc with respect to the temporal change in the predicted value calculated based on the voltage Vpp. It has been found that according to the examination by the present inventors, a large ESC current flows by the time difference between the predicted value of the voltage Vdc and the detected value of the voltage Vdc when the step is switched. Furthermore, in the sample  4  after the process, it has been acknowledged that heat is generated due to the concentration of the current in the portion B (through hole portion  201 B), in particular, of the membrane structure  40  in  FIG. 2 , so that this portion B is melted and disappears, causing damage. 
     [Effects, Etc. (1-1)] 
     As described above, the plasma processing apparatus  1  according to the first embodiment supplies the RF power to the ESC base metal  11  serving as a bias electrode in the sample stage  10  on which the sample  4  is placed and which supports the sample  4  to form an RF bias potential and perform the process on the sample  4 . Further, in the plasma processing apparatus  1 , as the ESC, a positive and negative DC voltage is applied to a plurality of electrodes  30  for ESC in the dielectric membrane  12  from the DC power supply  34  where both output terminals are completely brought to a floating potential through the LPF  33  during the processing of the sample  4 . A positive DC voltage is applied to the electrode  31 , and is imparted the positive polarity, and a negative DC voltage is applied to the electrode  32 , and is imparted the negative polarity. As a result, while the sample  4  is attracted and held during the process, the ESC current flowing from the plasma to the sample  4  with the RF bias potential is suppressed. Thus, in the first embodiment, even in the case of multi-step etching process on the sample  4  having the membrane structure  40  with a large antenna ratio on the upper surface side as shown in  FIG. 2 , damage to the sample  4  is prevented or suppressed. In the first embodiment, even when the process is performed such that the voltage Vdc due to the RF power for forming the RF bias potential, which is one of the process conditions, greatly fluctuates between the consecutive steps constituting the process, the damage is suppressed. 
     [ESC System-Equivalent Circuit] 
       FIG. 8  shows an electrical equivalent circuit including only DC component corresponding to the ESC system  5  including the plasma in  FIG. 3  explained in the plasma processing apparatus  1  in the first embodiment. In the equivalent circuit of  FIG. 8 , a capacitor with a capacitance Cesc is connected to a voltage Vdc of the sample  4 , and a capacitor with the capacitance Cb and a capacitor with the capacitance Cf are connected in parallel to the capacitor with the capacitance Cesc. The capacitance Cesc of the capacitor indicates a capacitance of the portion of the dielectric between the ESC electrode and the sample. In  FIG. 3 , this capacitance Cesc corresponds to the capacitance of the first portion P 1  of the dielectric membrane  12  between the upper surface of the electrodes  30  ( 31 ,  32 ) and the rear surface (placement surface sf 1 ) of the sample  4 . The capacitance Cb of the capacitor indicates a capacitance of the portion of the dielectric between the ESC electrode and the ESC base metal (bias electrode) of the sample stage. In  FIG. 3 , this capacitance Cb corresponds to the capacitance of the second portion P 2  of the dielectric membrane  12  between the lower surface of the electrodes  30  ( 31 ,  32 ) and the upper surface of the ESC base metal  11 . The capacitance Cf the capacitor is a capacitance of the capacitor in the LPF circuit. In  FIG. 3 , this capacitance Cf is the sum of the capacitance of all the capacitors in the circuit of the LPF  33 . In the case where the ESC system  5  includes a plurality of LPF circuits as the LPF  33 , for example, a first LPF  33 A and a second LPF  33 B in  FIG. 3 , the capacitance Cf is a capacitance of the capacitor when the plurality of LPF circuits are regarded as one circuit as a whole. 
     During the process in which the plasma is generated and the sample  4  is processed using these parameters, the value J of the ESC current flowing into the sample  4  at the time of switching the consecutive steps in which the RF power for forming the RF bias potential differs is expressed as follows. That is, the value J of the ESC current is expressed by the following Equation 2 using, as a parameter, the ESC current value J 0  (Equation 1) in the ESC system  19  of the first comparative example in  FIG. 17 . 
     
       
         
           
             
               
                 
                   
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     The relationship represented by Equation 2 is shown in  FIG. 9 .  FIG. 9  is a graph representing the relationship of Equation 2 with the capacitance ratio ((Cf+Cb)/Cesc) and ESC current ratio (J/J 0 ) in Equation 2 as parameters. 
     [ESC-Condition] 
     From the above, the following conditions are required in order to suppress the ESC current. (1) The capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (capacitance of the first portion P 1 ) is set as a first capacitance C 1 . The first capacitance C 1  corresponds to Cesc. (2) The capacitance of the portion of the dielectric membrane between the ESC electrode and the ESC base metal (capacitance of the second portion P 2 ) is set as a second capacitance C 2 . The second capacitance C 2  corresponds to Cb. (3) The sum of the capacitance of the capacitors in the LPF circuit is set as a third capacitance C 3 . The third capacitance C 3  corresponds to Cf. 
     As the condition, the sum (C 2 +C 3 ) of the second capacitance C 2  and the third capacitance C 3  is set to a value smaller than the first capacitance C 1  ((C 2 +C 3 )&lt;C 1 , (Cb+Cf)&lt;Cesc). The ESC system  5  in the first embodiment is set so as to satisfy the above conditions. 
     In the case of the mounting example of the ESC system  5  used in the first embodiment, the diameter of the sample  4  is, for example, 300 mm. The diameter of the upper surface of the sample stage  10  is equal to or larger than the diameter of the sample  4 . The average value of the distance of the portion (first portion P 1 ) between the ESC electrodes  30  ( 31 ,  32 ) and the sample  4  is 0.3 mm. Alumina (aluminum oxide) having a relative dielectric constant of 9.8 is used as a material constituting the dielectric membrane  12 . In addition, the capacitance Csec (first capacitance C 1 ) of the capacitor is set to about 20 nF. In the first embodiment, in order to reduce the value of the capacitance Cb (second capacitance C 2 ) of the capacitor, the distance of the portion (second portion P 2 ) between the ESC electrodes  30  ( 31 ,  32 ) and the ESC base metal  11  is set to 2.1 mm. As a result, as a mounting example in the first embodiment, the value of the capacitance Cb (second capacitance C 2 ) is set to 2.9 nF which is about 1/7 of the value of the capacitance Cesc (first capacitance C 1 ). Further, the third capacitance C 3  (capacitance Cf) related to the LPF  33  is set as follows. 
     [LPF Circuit ( 1 )] 
     In the first embodiment, the circuit shown in  FIG. 10  can be used as a mounting example of the circuit of the LPF  33 .  FIG. 10  is a circuit diagram schematically showing a configuration example of a circuit of the LPF  33  constituting the ESC system  5  of  FIG. 3  in the plasma processing apparatus  1  of the first embodiment. In this circuit, a coil  1001  (inductance: Lf) and a capacitor  1002  are connected between the ESC electrode (electrode  30 ) and a DC power supply  34 . The capacitance of the capacitor  1002  corresponds to the above-mentioned capacitance Cf. 
     In the configuration example of the circuit of the LPF  33 , the attenuation factor of the LPF  33  with respect to the RF power of, for example, 400 kHz used as the RF bias power is set to 30 dB or more. Therefore, the product value (Lf×Cf) of the value of the inductance Lf of the coil  1001  and the value of the capacitance Cf of the capacitor  1002  that determine the attenuation factor is maintained at 5×10 −12  s 2  or more ((Lf×Cf)≥5×10 −12  s 2 ) In order to reduce the capacitance Cf while maintaining this value (Lf×Cf), a coil  1001  having a relatively large inductance of Lf=20 mH is used. Finally, the capacitance Cf of the capacitor  1002  can be set to 0.25 nF. The capacitance Cf (third capacitance C 3 ) of the LPF  33  satisfies the above condition. 
     The frequency which is a circuit constant of the LPF circuit (LPF  33 ) is represented by √(Lf×Cf). In the first embodiment, the LPF  33  and the RF power supply  123  are electrically connected via constituent elements. As a requirement in this configuration, this circuit constant is made sufficiently smaller than the frequency of the RF power of the RF power supply  123 . 
     In the configuration of  FIG. 3  of the first embodiment, the ESC system  5  of the sample stage  10  is provided with two LPF circuits ( 33 A,  33 B) having the same configuration as the LPF  33  on the power supply path of each of the two electrodes  31  and  32  as the ESC electrodes  30 . Therefore, the capacitance Cf, which is the third capacitance C 3  (sum of the capacitance of the capacitors in the LPF), is 0.25 nF×2=0.5 nF. 
     From this fact, according to the examination by the present inventors, the magnitude of the ESC current estimated from Equation 2 is about 1/7 of the magnitude of the ESC current of the first comparative example. As described above, according to the ESC system  5  of the plasma processing apparatus  1  of the first embodiment, the ESC current flowing in the sample  4  can be remarkably reduced, as shown in  FIG. 4 , between the steps in which the value of the RF bias power (corresponding voltage Vdc) is different, and the effect of suppressing damage to the sample  4  can be obtained. 
     [LPF Circuit ( 2 )] 
     As another comparative example, in order to investigate the influence of the capacitance of the capacitor in the LPF  33 , the value of the capacitance in the LPF  33  is set to 25 nF, which is larger than the value of the capacitance Cesc, and the evaluation is conducted for the case where the membrane structure  40  in  FIG. 2  is similarly processed. In this case, the capacitance Cf (third capacitance C 3 ), which is the sum of capacitance of the capacitors in the LPF, is 50 nF. In this case, it has been found that the magnitude of the ESC current J estimated by Equation 2 is 75% of the magnitude of the ESC current J 0  of the first comparative example. In the process of the membrane structure  40  using the LPF  33 , it has been acknowledged that since the ESC current is not sufficiently suppressed, part of the portion B (through hole portion  201 B) of the membrane structure  40  disappears, causing damage. 
     [LPF Circuit ( 3 )] 
     Next, as another comparative example, in order to investigate the influence of the capacitance of the portion (second portion P 2 ) of the dielectric membrane  12  between the ESC electrodes  30  ( 31 ,  32 ) and the upper surface of the ESC base metal  11 , the evaluation is carried out with the following constitution. With this configuration, the distance of the second portion P 2  between the electrodes  31  and  32  and the upper surface of the ESC base metal  11  is set to 0.1 mm. With this configuration, as in the mounting example of the LPF  33  of the first embodiment, the evaluation is carried out on the case where the membrane structure  40  of  FIG. 2  is processed. At this time, the capacitance Cb (second capacitance C 2 ) of the portion of the dielectric membrane  12  between the electrodes  31  and  32  and the upper surface of the ESC base metal  11  is 61 nF. The second capacitance C 2  is larger than the capacitance Cesc (first capacitance C 1 ) of the first portion P 1  of the dielectric membrane  12  between the electrodes  31  and  32  and the sample  4 . In this case, the magnitude of the ESC current J estimated by Equation 2 is 75% of the magnitude of the ESC current J 0  of the first comparative example. In the process of the membrane structure  40  using such a structure, it has been acknowledged that since the suppression of the ESC current is not sufficient, part of the portion B of the membrane structure  40  disappears, causing damage. 
     [Effects, Etc. (1-2)] 
     As described above, in the mounting example of the ESC system  5  in the first embodiment, the capacitance of the portion of the dielectric membrane between the ESC electrode and the ESC base metal (second capacitance C 2 , capacitance Cb) is set to a value smaller than the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 , capacitance Cesc) (C 2 &lt;C 1 , Cb&lt;Cesc). Moreover, the sum of the capacitance of the capacitors in the LPF circuit (third capacitance C 3 , capacitance Cf) is set to a value smaller than the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 , capacitance Cesc) (C 3 &lt;C 1 , Cf&lt;Cesc). As a result, the ESC current flowing into the sample  4  between steps in which the value of the RF bias power (voltage Vdc) differs is reduced, and damage to the sample  4  due to the ESC current can be suppressed. 
     [Modification-LPF Circuit] 
     In the circuit configuration example of the LPF  33  in  FIG. 10  of the first embodiment, a so-called single-stage filter circuit in which one coil  1001  and one capacitor  1002  are combined is used. In addition, as an LPF circuit, for example, as shown in  FIG. 11 , even when a multistage filter circuit in which a plurality of circuits each of which is constituted by a set of the coil  1001  and the capacitor  1002  is connected in series is used, a similar effect can be obtained.  FIG. 11  schematically shows a circuit configuration example of the LPF  33  in the plasma processing apparatus  1  according to the modification. In  FIG. 11  a plurality of circuits each of which is constituted by a set of the coil  1001  and the capacitor  1002  is serially connected in three stages between the electrode  30  and the DC power supply  34 . 
     Mounting Example 
     In the first embodiment, as a mounting example, in order to reduce the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 , the capacitance Cesc), as shown in  FIG. 12 , the distance of the second portion P 2  of the dielectric membrane  12  between the electrode  30  and the ESC base metal  11  is increased. 
       FIG. 12  shows a configuration example relating to the thickness of the dielectric membrane  12  in the ESC system  5  of the mounting example. In the dielectric membrane  12 , the plurality of electrodes  30  ( 31 ,  32 ) disposed at the position z 1  in the thickness direction (Z direction) has a predetermined thickness H 3 . The first portion P 1  of the dielectric membrane  12  between the upper surface of the electrode  30  and the rear surface (placement surface sf 1 ) of the sample  4  has a predetermined thickness H 1 . The second portion P 2  of the dielectric membrane  12  between the lower surface of the electrode  30  and the upper surface of the ESC base metal  11  has a predetermined thickness H 2 . 
     In this mounting example, the thickness H 2  of the second portion P 2  is larger than the thickness H 1  of the first portion P 1 . As a result, as described above, the first capacitance C 1  is reduced. 
     Not limited to such a mounting example, as an modification, even when a member made of a dielectric material having a low dielectric constant is disposed between the lower surface of the electrode  30  and the upper surface of the ESC base metal  11 , a similar effect can be obtained. 
     [Effects Etc. (1-3)] 
     As described above, according to the plasma processing apparatus  1  of the first embodiment, the processing of the sample  4  using the sample stage  10  having the ESC system  5  is performed, so that the processing yield can be improved. According to the plasma processing apparatus  1 , in the multi-step etching process in which the RF bias power varies, the ESC current flowing through the sample  4  can be significantly reduced when the voltage Vdc varies between steps as compared with the case of the prior art example. Therefore, according to the plasma processing apparatus  1 , even when there is the membrane structure  40  or the like having a high antenna ratio in the sample  4 , damage due to the ESC current can be suppressed. That is, according to the plasma processing apparatus  1 , the performance of a semiconductor device manufactured by performing a process using plasma is not impaired and the processing yield can be improved. 
     Second Embodiment 
     In addition to the plasma processing apparatus  1  of the first embodiment, a plasma processing apparatus of the other embodiments (modification) as described below can be also applied. Hereinafter, components in each embodiment different from those of the first embodiment will be described. 
     With reference to  FIG. 13 , the ESC system of the plasma processing apparatus according to the second embodiment of the present invention will be described. In the first embodiment, as shown in  FIG. 3 , the ESC system  5  including one positive electrode and one negative electrode as the ESC electrodes  30  and one DC power supply  34  has been described. The ESC system of the plasma processing apparatus of the second embodiment includes a plurality of pairs of electrodes to which the positive polarity and the negative polarity are imparted and a plurality of DC power supplies connected to the plurality of pairs of electrodes. 
       FIG. 13  is a vertical cross-sectional view schematically showing the outline of the configuration of the ESC system  52  in the second embodiment. The sample stage  10  is provided with the ESC system  52 . The ESC system  52  includes, as a plurality of ESC electrodes  30 , the positive polarity electrode  31  and the negative polarity electrode  32 . Furthermore, each polarity electrode is composed of a pair of electrodes. The electrode  31  has a pair of electrodes, which is an electrode  31 A and an electrode  31 B. The electrode  32  has a pair of electrodes, which is the electrode  32 A and the electrode  32 B. The respective electrodes  30  are electrically connected to the corresponding positive and negative output terminals of the DC power supply  34  via the LPF  33 . The LPF  33  includes an LPF  33   a , an LPF  33   b , an LPF  33   c , and an LPF  33   d  as a plurality of LPF circuits. A pair of LPF  33   a  and LPF  33   b , and a pair of LPF  33   c  and LPF  33   d  are provided. The DC power supply  34  has a first DC power supply  34 A and a second DC power supply  34 B as two DC power supplies. 
     In the X-Y plane of the sample stage  10  and the dielectric membrane  12  in planar view, for example, the electrode  31 A and the electrode  32 A on one side (outer side in the X direction in the figure) are electrically connected to the positive and negative electrode terminals of the first DC power supply  34 A via the LPF  33  (LPF  33   a ,  33   b ), respectively. The electrode  31 A is connected to the positive electrode terminal of the first DC power supply  34 A via the LPF  33   a , and is imparted the positive polarity. The electrode  32 A is connected to the negative electrode terminal of the first DC power supply  34 A via the LPF  33   b , and is imparted the negative polarity. The electrode  31 B and the electrode  32 B on the other side (inner side in the X direction shown in the figure) are electrically connected to the positive and negative electrode terminals of the second DC power supply  34 B via the LPF  33  (LPF  33   c ,  33   d ), respectively. The electrode  31 B is connected to the positive electrode terminal of the second DC power supply  34 B via the LPF  33   c , and is imparted the positive polarity. The electrode  32 B is connected to the negative electrode terminal of the second DC power supply  34 B via the LPF  33   d , and is imparted the negative polarity. 
     In the second embodiment, the configuration of the equivalent circuit for each of a pair of ESC electrodes is the same as that of the above ( FIG. 8 ). The positions and shapes of the plurality of electrodes  30  in the X-Y plane in planar view are not limited to the configuration shown in  FIG. 12 , and are not particularly limited. 
     In the ESC system  52  of  FIG. 13 , the distance of the first portion P 1  of the dielectric membrane  12  between the upper surface of the two pairs of electrodes  30  ( 31 ,  32 ) for the ESC and the rear surface (placement surface sf 1 ) of the sample  4  is set to 0.3 mm. The distance of the second portion P 2  of the dielectric membrane  12  between the lower surface of the electrode  30  and the upper surface of the ESC base metal  11  is set to 2.1 mm. In addition, the dielectric membrane  12  is made of aluminum oxide as a material. In this configuration, the capacitance Cesc corresponding to the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 ) is set to 20 nF. Further, the capacitance Cb corresponding to the capacitance of the portion of the dielectric membrane between the ESC electrode and the ESC base metal (second capacitance C 2 ) is set to 2.9 nF. 
     However, in this configuration, the positive and negative electrodes  31  and  32  have the following configuration, for example. That is, a pair of electrodes  31 B and  32 B to which positive and negative polarities are imparted is disposed near the center part of the upper portion of the sample stage  10  (near the center axis of the dashed line in  FIG. 1 ). In addition, another pair of electrodes  31 A and  32 A to which positive and negative polarities are imparted is disposed on the outer peripheral part of the upper portion of the sample stage  10 . That is, two pairs of electrodes, which means a total of four electrodes, are disposed. In other words, for example, a first pair of positive and negative electrodes is disposed on the inner peripheral portion and a second pair of positive and negative electrodes is disposed on the outer peripheral portion of the sample stage  10  in one direction (X direction). 
     Each of the electrodes of the plurality of pairs of electrodes to which positive and negative polarities are imparted is electrically connected via the LPF  33  to respective positive and negative electrode terminals of two DC power supplies  34  which are completely brought to a floating potential at least during the processing of the sample  4 . As a result, positive and negative DC voltages are applied to the respective electrodes of the plurality of electrodes  30  ( 31 ,  32 ) as shown in the figure. An electrostatic force is generated between the positive electrode  31  and the negative electrode  32 . 
     Further, in the second embodiment, the capacitance (third capacitance C 3 , capacitance Cf) of the capacitor of the circuit constituting the LPF  33  is set to 0.25 nF. The LPF  33  of the second embodiment includes a total of four LPF circuits (LPF  33   a  to LPF  33   d ) as shown in the figure. The capacitance Cf (third capacitance C 3 ), which is the sum of the capacitance of the capacitors in the LPF circuits as a whole, is 1 nF which is sufficiently smaller than the capacitance Cesc (first capacitance C 1 ). As a result, the value J of the ESC current calculated by Equation 2 is about 1/7 of the value J 0  of the ESC current in the ESC system  19  of the first comparative example in  FIG. 17 . 
     When the membrane structure  40  of the sample  4  in  FIG. 2  is processed using the ESC system  52  of the second embodiment, it has been acknowledged that no damage to the sample  4  occurs since the ESC current is sufficiently suppressed. 
     Next, as a comparative example in the second embodiment, a case where the capacitance of the capacitor disposed in the circuit constituting the LPF  33  is set to 25 nF is examined. In this case, the capacitance Cf (third capacitance C 3 ), which is the sum of the capacitance of the capacitors in the LPF  33  circuit, is 100 nF, which is larger than the capacitance Cesc (first capacitance C 1 ). The value J of the ESC current represented by Equation 2 is 83% of the value J 0  of the ESC current in the case of the first comparative example in  FIG. 17 . In addition, when the membrane structure  40  of  FIG. 2  is processed by using the ESC system of this comparative example, it has been acknowledged that the suppression of the ESC current J is insufficient, so that the portion B of the sample  4  disappears, causing damage. 
     As described above, in the configuration of the second embodiment, the capacitance of the portion of the dielectric membrane between the ESC electrode and the ESC base metal (second capacitance C 2 , capacitance Cb) is set to a value which is smaller than the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 , capacitance Cesc). Furthermore, the sum of the capacitance of the capacitors of the LPF circuit (third capacitance C 3 , capacitance Cf) is set to a value which is smaller than the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 , capacitance Cesc). As a result, it has been found that according to the second embodiment, the ESC current flowing into the sample  4  can be reduced and damage to the sample  4  due to the ESC current can be suppressed. In the ESC system  52  of  FIG. 13 , two pairs of positive and negative electrodes  31  and  32  and two pairs of DC power supplies  34  are used as an example. The embodiment is not limited to this. Even in a configuration in which three or more pairs are used, if the third capacitance C 3  is made smaller than the first capacitance C 1  in the same manner as described above, a similar effect can be obtained. 
     Third Embodiment 
     Next, with reference to  FIGS. 14A and 14B , the ESC system of the plasma processing apparatus according to the third embodiment of the present invention will be described.  FIG. 14A  is a vertical cross-sectional view schematically showing the configuration outline of the ESC system  53  according to the third embodiment.  FIG. 14B  shows an electrical equivalent circuit including the ESC system  53  of  FIG. 14A . 
     In the third embodiment, in order to reduce the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 , capacitance Cesc), instead of the configuration in which the distance of the second portion P 2  between the electrode  30  and the ESC base metal  11  is increased as in the above mentioned mounting example of  FIG. 12 , the following configuration is provided. That is, in the third embodiment, as shown in  FIG. 14A , a capacitor  1401  having a small capacitance is inserted and disposed at a position between the ESC base metal  11  and the matching unit  122  on the power supply path of the RF power for electrically connecting the sample stage  10  and the RF power supply  123 . As a result, the effective capacitance of the circuit constituting the ESC system  53  is lowered. Let the capacitance of the capacitor  1401  be capacitance Co. 
     In the ESC system  53  of the third embodiment, as a mounting example, the distance of the first portion P 1  between the upper surface of the electrode  30  ( 31 ,  32 ) and the rear surface (placement surface sf 1 ) of the sample  4  is set to 0.3 mm. The distance of the second portion P 2  between the lower surface of the electrode  30  and the upper surface of the ESC base metal  11  is set to 0.1 mm. Also, aluminum oxide is used as the dielectric material of the dielectric membrane  12  disposed in this distance relationship. In this configuration, the capacitance Cesc corresponding to the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 ) is 20 nF. Further, the capacitance Cb corresponding to the capacitance of the portion of the dielectric membrane between the ESC electrode and the ESC base metal (second capacitance C 2 ) is 61 nF. 
     In the configuration of the third embodiment, as in the configuration of the first embodiment shown in  FIG. 3 , a positive electrode terminal and a negative electrode terminal of the DC power supply  34  which are completely brought to a floating potential during at least processing are electrically connected to the corresponding positive and negative electrodes  31  and  32  via respective LPFs  33  ( 33 A,  33 B). A DC voltage is applied to these electrodes  31  and  32 , and positive and negative polarities are imparted. The capacitance Cf (third capacitance C 3 ) of the capacitors disposed in the circuit of the LPF  33  in the ESC system  53  as a whole circuit is set to 0.25 nF which is sufficiently smaller than the capacitance Cesc. 
       FIG. 14B  shows an equivalent circuit for the DC component concerning the LPF  33  in the third embodiment. This equivalent circuit is obtained by inserting the capacitance Co corresponding to the capacitor  1401  in series with the capacitance Cb between the capacitance Cb of the capacitor and the grounded portion in the circuit of  FIG. 8  described above. Therefore, the value J of the ESC current in this system is obtained by replacing Cb in Equation 2 with composite capacitance Cb′ expressed by Equation 3 below. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       Math 
                       . 
                       
                           
                       
                       ⁢ 
                       3 
                     
                     ] 
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     C 
                     b 
                     ′ 
                   
                   = 
                   
                     
                       
                         C 
                         b 
                       
                       ⁢ 
                       
                         C 
                         o 
                       
                     
                     
                       
                         C 
                         b 
                       
                       + 
                       
                         C 
                         o 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
               
             
           
         
       
     
     Here, when the value of the capacitance Co is 3 nF, the composite capacitance Cb′ is 2.9 nF from the Equation 3. The value of Cb′ is the same value as when the distance between the electrode  30  and the ESC base metal  11  in the ESC system  5  of  FIG. 3  is set to 2.1 mm. Therefore, the value J of the ESC current in the configuration of the third embodiment is reduced to about 1/7 of the value J 0  of the ESC current of the first comparative example in  FIG. 17 . In addition, when the processing of the membrane structure  40  of  FIG. 2  is performed using the ESC system  53  of the third embodiment, it is acknowledged that damage is reduced. 
     As described above, in the third embodiment, in the configuration of  FIG. 14A , the capacitor  1401  having a capacitance (capacitance Co) smaller than the capacitance of the portion of the dielectric membrane between the ESC electrode and the ESC base metal (second capacitance C 2 , capacitance Cb) is connected and disposed between the ESC base metal  11  and the matching unit  122  in series. As a result, it has been found that the ESC current flowing into the sample  4  can be suppressed and damage to the sample  4  by the ESC current can be suppressed. 
     In the third embodiment, the capacitor  1401  is disposed on the RF power supply path between the ESC base metal  11  and the matching unit  122 . The present invention is not limited to this, and as long as the capacitor  1401  is disposed at a position to represent the equivalent electrical circuit, a similar effect can be obtained, for example, even by a configuration in which the capacitor  1401  is disposed in the matching unit  122 . 
     Fourth Embodiment 
     Next, with reference to  FIGS. 15A and 15B and 16A and 16B , the ESC system of the plasma processing apparatus according to the fourth embodiment of the present invention will be described.  FIG. 15A  shows a configuration outline of the ESC system  54  and the like in the fourth embodiment.  FIG. 15B  shows an equivalent circuit including the ESC system  54  of  FIG. 15A . As shown in  FIG. 15A , the ESC system  54  according to the fourth embodiment includes a heater electrode  150  as a heater in the sample stage  10 , in particular, in the dielectric membrane  12 . In the fourth embodiment, a configuration example in the case of adding a heater system based on the ESC system  5  of the first embodiment will be described. Note that the heater electrode  150  itself is a known technique. It is possible to control the temperature of the sample stage  10  during processing and the like by controlling the temperature of the heater electrode  150 . 
     The ESC system  54  of  FIG. 15A  has the ESC electrodes  30  ( 31 ,  32 ) at a predetermined position z 1  closer to the placement surface sf 1  in the thickness direction (Z direction) within the dielectric membrane  12 . The DC power supply  34  is connected to the electrode  30  via the LPF  33  in the same manner as described above. 
     Further, a plurality of heater electrodes  150  is disposed at a predetermined position z 2  between the lower surface of the electrode  30  and the upper surface of the ESC base metal  11 . The plurality of heater electrodes  150  includes a pair of two heater electrodes, that is, a heater electrode  151  and a heater electrode  152 . The plurality of heater electrodes  150  is spaced apart from each other by a predetermined distance in one direction (X direction) in the horizontal direction. The heater electrode  150  is made of a tungsten material and has a film shape with a predetermined thickness. 
     In this example, the heater electrodes  151  and  152  provided as a pair of heater electrodes correspond to a pair of positive and negative electrodes  31  and  32 . The pair of the heater electrodes  151  and  152  is disposed at a further inner position than the pair of positive and negative electrodes  31  and  32 . The width of each of the plurality of heater electrodes  150  in the X direction is smaller than the width of the electrode  30  in the X direction. Various configurations are possible without being limited to the configuration in this example. 
     The ceramic dielectric membrane  12  is made of aluminum oxide. As a mounting example, the distance of the portion of the dielectric membrane  12  between the upper surface of the electrode  30  and the rear surface of the sample  4  is 0.3 mm. The distance of the portion of the dielectric membrane  12  between the lower surface of the electrode  30  and the upper surface of the heater electrode  150  is 0.3 mm. The distance of the portion of the dielectric membrane  12  between the lower surface of the heater electrode  150  and the upper surface of the ESC base metal  11  is 1.8 mm. 
     In the configuration of the ESC system  54  of the fourth embodiment, the capacitance Cesc corresponding to the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (first capacitance C 1 ) is set to 20 nF. The capacitance Ch corresponding to the capacitance of the portion of the dielectric membrane between the ESC electrode and the heater electrode (referred to as a fourth capacitance C 4 ) is set to 20 nF. The capacitance Cb corresponding to the capacitance of the portion of the dielectric membrane between the heater electrode and the ESC base metal (referred to as a fifth capacitance C 5 ) is set to 3.4 nF. 
     Each of the plurality of heater electrodes  150  ( 151 ,  152 ) is electrically connected to an alternating current power supply (AC power supply)  154  via a power supply path including an LPF  155  (LPF  155 A,  155 B), which is a heater LPF (AC: alternating current). The heater electrode  151  associated with the positive electrode  31  is connected to one end of an insulating transformer  153  via the LPF  155 A. The heater electrode  152  associated with the negative electrode  32  is connected to the other end of the insulating transformer  153  via the LPF  155 B. AC power from the AC power supply  154  is supplied to each of the heater electrodes  150 . The AC power supply  154  and the LPF  155  are electrically connected to each other via an insulating transformer  153  disposed therebetween. AC power from the AC power supply  154  is supplied to the LPF  155  and the heater electrode  150  in a state of being completely insulated in direct current manner. 
     Further, the capacitance of the capacitor disposed in the circuit constituting the LPF  155  is set to 0.25 nF. The capacitance Cf′, which is the sum of the capacitance of the capacitors in the LPF  155  on the circuit feeding electric power to the heater electrode  150 , is set to 0.5 nF, which is sufficiently smaller than the capacitance Cesc. 
     In the equivalent circuit of  FIG. 15B , the capacitance Cesc of the capacitance corresponding to the portion between the sample  4  and the electrode  30  is connected to the capacitor of the capacitance Ch corresponding to the portion between the electrode  30  and the heater electrode  150  and the capacitor of the capacitance Cf corresponding to the LPF  33  while the capacitor of the capacitance Ch and the capacitor of the capacitance Cf are connected in parallel. The capacitor of the capacitance Ch is connected to the capacitor of the capacitance Cb corresponding to the portion between the heater electrode  150  and the ESC base metal  11  and the capacitor of the capacitance Cf′ corresponding to the LPF  155  on the heater side while the capacitor of the capacitance Cb and the capacitor of the capacitance Cf′ are connected in parallel. 
     From this equivalent circuit, the value J of the ESC current flowing from the plasma through the sample  4  to the sample stage  10  when the voltage Vdc fluctuates in the fourth embodiment is expressed by the following Equation 4. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       Math 
                       . 
                       
                           
                       
                       ⁢ 
                       4 
                     
                     ] 
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   J 
                   = 
                   
                     
                       
                         
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                         + 
                         
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                           ″ 
                         
                       
                       
                         
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                         + 
                         
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                           b 
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                         + 
                         
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                           esc 
                         
                       
                     
                     ⁢ 
                     
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                       o 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   4 
                 
               
             
           
         
       
     
     In Equation 4, the capacitance Cb″, which is the composite capacitance, is expressed by the following Equation 5. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       Math 
                       . 
                       
                           
                       
                       ⁢ 
                       5 
                     
                     ] 
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     C 
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                         C 
                         h 
                       
                       ⁡ 
                       
                         ( 
                         
                           
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                             f 
                             ′ 
                           
                           + 
                           
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                         h 
                       
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                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   5 
                 
               
             
           
         
       
     
     In the ESC system  54  of the fourth embodiment having the above configuration, the value J of the flowing ESC current is reduced to about 1/7 of the ESC current value J 0  of the first comparative example in  FIG. 17 . In addition, when the membrane structure  40  of  FIG. 2  is processed using the plasma processing apparatus  1  including the ESC system  54  of the fourth embodiment, it has been acknowledged that the ESC current is sufficiently suppressed, and damage to the sample  4  is reduced. 
     Comparative Example (1) of Fourth Embodiment 
     Next, the following configuration is examined as the ESC system of the comparative example to the above-described the fourth embodiment. In this comparative example, the case where the capacitance of the capacitor in the circuit constituting the LPF  155  on the heater side in  FIGS. 15A and 15B  is set to a value larger than the capacitance Cesc, for example, 25 nF is examined. In this configuration, the sum of capacitance of the capacitors of the LPF  155  is 50 nF. In addition, the composite capacitance Cb″ represented by Equation 5 is 14.5 nF. In this case, the value J of the ESC current is 42% of the value J 0  of the ESC current of the first comparative example in  FIG. 17 . Meanwhile, when the membrane structure  40  of  FIG. 2  is processed using the plasma processing apparatus having the ESC system of this comparative example, suppression of the ESC current is insufficient, so that part of the portion B disappears, causing damage. 
     Comparative Example (2) of Fourth Embodiment 
     Next, the following configuration is examined as the ESC system of another comparative example to the above-described the fourth embodiment.  FIG. 16A  shows a configuration outline of the ESC system of the plasma processing apparatus of this comparative example.  FIG. 16B  shows an equivalent circuit for the DC component including the ESC system in  FIG. 16A . In the configuration of this comparative example, as shown in  FIG. 16A , the heater electrode  150  and the AC power supply  154  of  FIG. 15A  are electrically connected to each other via the LPF  155  without the insulating transformer  153  being interposed, and AC power is supplied to the heater electrode  150 . Except for the insulating transformer  153 , the ESC system of this comparative example has substantially the same configuration as the ESC system of the fourth embodiment of  FIG. 15A . 
     In the equivalent circuit of  FIG. 16B , the capacitance Cf and the capacitance Ch which are connected in parallel are connected to the capacitance Cesc. Based on this equivalent circuit, the value J of the ESC current flowing from the plasma through the sample  4  to the sample stage  10  when the voltage Vdc fluctuates is expressed by Equation 6 below. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       Math 
                       . 
                       
                           
                       
                       ⁢ 
                       6 
                     
                     ] 
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   J 
                   = 
                   
                     
                       
                         
                           C 
                           f 
                         
                         + 
                         
                           C 
                           h 
                         
                       
                       
                         
                           C 
                           f 
                         
                         + 
                         
                           C 
                           h 
                         
                         + 
                         
                           C 
                           esc 
                         
                       
                     
                     ⁢ 
                     
                       J 
                       o 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   6 
                 
               
             
           
         
       
     
     The value J of the ESC current in this comparative example is 50% of the ESC current value J 0  in the first comparative example in  FIG. 17 . Furthermore, when the membrane structure  40  of  FIG. 2  is processed by using the plasma processing apparatus having the ESC system of this comparative example, it has been acknowledged that suppression of the ESC current is insufficient, so that the sample is damaged. 
     In view of the above, when supplying AC power to the heater electrode  150  disposed in the dielectric membrane  12  of the ESC system, as shown in  FIG. 15A , AC power is supplied from the AC power supply  154  via the insulating transformer  153  and the LPF  155 . At the same time, the sum of the capacitance of the capacitors in the LPF  155  (capacitance Cf′) is set to be smaller than the capacitance of the portion of the dielectric membrane between the ESC electrode and the sample (capacitance Cesc) (Cf′&lt;Cesc). As a result, it has been found that the ESC current flowing into the sample  4  is suppressed, and damage to the sample  4  by the ESC current is suppressed. 
     In  FIGS. 15A and 15B and 16A and 16B , an example in which only one AC power supply for the heater electrode is used has been described. The present invention is not limited to this. Even in a configuration in which power is supplied to the heater electrode by using a plurality of AC power supplies, the insulating transformer  153  and the LPF  155  are used, and the above mentioned capacitance is set (Cf′&lt;Cesc), so that a similar effect can be obtained. 
     Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof. For example, in the electric circuit to which the electrode  30 , the LPF  33 , and the DC power supply  34  in  FIG. 3 , etc. are connected, it is of course possible to add a switch circuit or the like for controlling the electrical on/off.