Patent Publication Number: US-11380568-B2

Title: Transfer method and transfer system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 16/710,985 filed Dec. 11, 2019, which is based on and claims the benefit of priority from Japanese Patent Application No. 2018-234265 filed on Dec. 14, 2018 the entire contents of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Exemplary embodiments of the present disclosure relate to a transfer method and a transfer system. 
     BACKGROUND 
     Japanese Unexamined Patent Publication No. 2006-196691 discloses a semiconductor manufacturing apparatus. The apparatus includes a substrate processing chamber, a focus ring standby chamber, and a transfer mechanism. An electrode is disposed inside the substrate processing chamber. A substrate is placed on the electrode. The focus ring standby chamber accommodates a plurality of focus rings. The transfer mechanism transfers the focus ring accommodated in the focus ring standby chamber to the substrate processing chamber without opening the substrate processing chamber to the atmosphere. The focus ring is disposed so as to surround the periphery of the substrate placed on the electrode. 
     SUMMARY 
     In one exemplary embodiment, a transfer method is provided. The transfer method is a transfer method in a transfer system of a focus ring, and the transfer system includes a processing system and a measuring instrument. The processing system includes a processing apparatus and a transfer unit. The processing apparatus has a chamber body and a stage including an electrostatic chuck provided in the chamber provided by the chamber body. The transfer unit transfers a workpiece into the inner region surrounded by the focus ring disposed on the stage and onto the electrostatic chuck based on transfer position data. The measuring instrument includes a sensor that acquires a measurement value group for obtaining a first amount of deviation which is an amount of deviation of a central position of the focus ring with respect to the central position of the focus ring and a second amount of deviation which is an amount of deviation of the central position of the measuring instrument with respect to a central position of the electrostatic chuck, in a state where the measuring instrument is positioned in the inner region and on the electrostatic chuck. The method includes: a step of transferring the focus ring onto the stage by the transfer unit; a step of transferring the measuring instrument by the transfer unit into the inner region of the transferred focus ring and onto the electrostatic chuck; a step of acquiring the measurement value group by the transferred measuring instrument; a step of obtaining the first amount of deviation and the second amount of deviation based on the measurement value group; a step of obtaining a third amount of deviation which is an amount of deviation of the central position of the focus ring with respect to the central position of the electrostatic chuck based on the first amount of deviation and the second amount of deviation; and a step of adjusting a transfer position of the focus ring by the transfer unit such that the central position of the electrostatic chuck and the central position of the focus ring coincide with each other based on the third amount of deviation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating an exemplary processing system. 
         FIG. 2  is a perspective view illustrating an exemplary aligner. 
         FIG. 3  is a view illustrating an example of a plasma processing apparatus. 
         FIG. 4  is a plan view illustrating an exemplary measuring instrument viewed from an upper surface side. 
         FIG. 5  is a plan view illustrating an exemplary measuring instrument viewed from a bottom surface side. 
         FIG. 6  is a perspective view illustrating an example of a first sensor. 
         FIG. 7  is a sectional view taken along line VII-VII in  FIG. 6 . 
         FIG. 8  is an enlarged view of a second sensor in  FIG. 5 . 
         FIG. 9  is a view illustrating a configuration of a circuit board of the measuring instrument. 
         FIG. 10  is a view schematically illustrating an example of a positional relationship between a focus ring and the measuring instrument. 
         FIG. 11  is a sectional view schematically illustrating an electrostatic chuck. 
         FIGS. 12A to 12C  are a sectional view schematically illustrating an example of a positional relationship between the electrostatic chuck and the measuring instrument. 
         FIG. 13  is a graph illustrating an example of a relationship between an overlap length and a measurement value. 
         FIG. 14  is a view schematically illustrating an example of a positional relationship between the electrostatic chuck and the measuring instrument. 
         FIG. 15  is a view schematically illustrating an example of a positional relationship of the electrostatic chuck, the focus ring, and the measuring instrument. 
         FIG. 16  is a flowchart illustrating an example of a method for transferring the focus ring. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, various embodiments will be described in detail with reference to the drawings. 
     In one exemplary embodiment, a transfer method is provided. The transfer method is a transfer method in a transfer system of a focus ring, and the transfer system includes a processing system and a measuring instrument. The processing system includes a processing apparatus and a transfer unit. The processing apparatus has a chamber body and a stage including an electrostatic chuck provided in the chamber provided by the chamber body. The transfer unit transfers a workpiece into the inner region surrounded by the focus ring disposed on the stage and onto the electrostatic chuck based on transfer position data. The measuring instrument includes a sensor that acquires a measurement value group for obtaining the first amount of deviation and the second amount of deviation in a state where the measuring instrument is positioned in the inner region and on the electrostatic chuck. The first amount of deviation is an amount of deviation of a central position of the measuring instrument with respect to a central position of the focus ring. The second amount of deviation is an amount of deviation of a central position of the measuring instrument with respect to a central position of the electrostatic chuck. The method includes a step of transferring the focus ring onto the stage by a transfer unit. The method includes a step of transferring the measuring instrument by the transfer unit into the inner region of the transferred focus ring and onto the electrostatic chuck. The method includes a step of acquiring a measurement value group by the transferred measuring instrument. The method includes a step of obtaining a first amount of deviation and a second amount of deviation based on the measurement value group. The method includes a step of obtaining a third amount of deviation which is an amount of deviation of a central position of the focus ring with respect to a central position of the electrostatic chuck based on the first amount of deviation and the second amount of deviation. The method includes a step of adjusting the transfer position of the focus ring by the transfer unit such that the central position of the electrostatic chuck and the central position of the focus ring coincide with each other based on the third amount of deviation. 
     In the transfer method of the above-described embodiment, after the focus ring is transferred onto the stage, the measuring instrument is transferred to the inner region of the focus ring. The measuring instrument acquires the measurement value group for obtaining the first amount of deviation and the second amount of deviation. In the method, the third amount of deviation which is an amount of deviation of the central position of the focus ring with respect to the central position of the electrostatic chuck is obtained from the first amount of deviation and the second amount of deviation which are obtained based on the measurement value group. The transfer position of the focus ring is adjusted such that the central position of the electrostatic chuck and the central position of the focus ring coincide with each other based on the third amount of deviation. In this manner, after the focus ring is transferred onto the stage, the focus ring can be transferred with high accuracy by adjusting the transfer position of the focus ring based on the third amount of deviation. 
     In one exemplary embodiment, the transfer unit may be disposed in a space airtightly connected to the chamber body. In this configuration, a focus ring FR can be transferred in the space airtightly connected to the chamber body. In this case, the focus ring can be transferred and the position of the focus ring can be adjusted without opening the chamber body to the atmosphere. 
     In one exemplary embodiment, the method may further include a step of determining whether or not the third amount of deviation exceeds a threshold value. In this case, in the step of adjusting the transfer position of the focus ring, the position of the focus ring may be adjusted when it is determined that the third amount of deviation exceeds the threshold value. 
     In one exemplary embodiment, the method may further include a step of confirming whether or not the third amount of deviation exceeds the threshold value in the focus ring of which the transfer position has been adjusted after the step of adjusting the transfer position of the focus ring. 
     In another exemplary embodiment, there is provided a system that transfers a focus ring. The system includes a processing system and a measuring instrument. The processing system includes a processing apparatus and a transfer unit. The processing apparatus has a chamber body and a stage including an electrostatic chuck provided in the chamber provided by the chamber body. The transfer unit transfers the focus ring onto the stage, and transfers the measuring instrument into an inner region surrounded by the focus ring and onto the electrostatic chuck. The measuring instrument obtains a third amount of deviation based on the first amount of deviation and the second amount of deviation in a state where the measuring instrument is positioned in the inner region and on the electrostatic chuck. The first amount of deviation is an amount of deviation of a central position of the measuring instrument with respect to a central position of the focus ring. The second amount of deviation is an amount of deviation of a central position of the measuring instrument with respect to a central position of the electrostatic chuck. The third amount of deviation is an amount of deviation of the central position of the focus ring with respect to the central position of the electrostatic chuck. The transfer unit adjusts a transfer position of the focus ring such that the central position of the electrostatic chuck and the central position of the focus ring coincide with each other based on the third amount of deviation. 
     Hereinafter, various embodiments will be described in detail with reference to the drawings. In the drawing, the same or equivalent portions are denoted by the same reference symbols. 
     A transfer system S 1  of a focus ring FR in one exemplary embodiment executes transfer of the focus ring FR, for example, to replace the focus ring FR that has been consumed due to use with a new focus ring FR. The transfer system S 1  includes a processing system  1  and a measuring instrument  100 . First, the processing system having a processing apparatus for processing a workpiece, and a transfer unit for transferring a workpiece to the processing apparatus will be described.  FIG. 1  is a view illustrating an exemplary processing system. The processing system  1  includes stands  2   a  to  2   d , containers  4   a  to  4   d , a loader module LM, an aligner AN, load lock modules LL 1  and LL 2 , process modules PM 1  to PM 6 , a transfer module TF, and a controller MC. The number of the stands  2   a  to  2   d , the number of the containers  4   a  to  4   d , the number of the load lock modules LL 1  and LL 2 , and the number of the process modules PM 1  to PM 6  are not limited and can be any number of one or more. 
     The stands  2   a  to  2   d  are arranged along one edge of the loader module LM. The containers  4   a  to  4   d  are respectively mounted on the stands  2   a  to  2   d . For example, each of the containers  4   a  to  4   d  is a container referred to as a front opening unified pod (FOUP). Each of the containers  4   a  to  4   d  is configured to accommodate a workpiece W therein. The workpiece W has a substantial disk shape such as a wafer. 
     The loader module LM has a chamber wall which defines a transfer space in an atmospheric pressure state therein. A transfer unit TU 1  is provided in the transfer space. For example, the transfer unit TU 1  is an articulated robot which is controlled by the controller MC. The transfer unit TU 1  is configured to transfer the workpiece W between the containers  4   a  to  4   d  and the aligner AN, between the aligner AN and the load lock modules LL 1  and LL 2 , and between the load lock modules LL 1  and LL 2  and the containers  4   a  to  4   d.    
     The aligner AN is connected to the loader module LM. The aligner AN is configured to adjust the position (to calibrate the position) of the workpiece W.  FIG. 2  is a perspective view illustrating an exemplary aligner. The aligner AN has a support stand  6 T, a driving unit  6 D, and a sensor  6 S. The support stand  6 T is a stand capable of rotating around an axis that extends in a vertical direction and is configured to support the workpiece W thereon. The support stand  6 T is rotated by the driving unit  6 D. The driving unit  6 D is controlled by the controller MC. When the support stand  6 T rotates due to power from the driving unit  6 D, the workpiece W placed on the support stand  6 T also rotates. 
     The sensor  6 S is an optical sensor and detects an edge of the workpiece W while the workpiece W is rotated. From the detection result of the edge, the sensor  6 S detects the amount of deviation of an angle position of a notch WN (or different type of marker) of the workpiece W with respect to a reference angle position, and the amount of deviation of a central position of the workpiece W with respect to a reference position. The sensor  6 S outputs the amount of deviation of the angle position of the notch WN and the amount of deviation of the central position of the workpiece W to the controller MC. The controller MC calculates the rotation amount of the support stand  6 T for correcting the angle position of the notch WN to the reference angle position based on the amount of deviation of the angle position of the notch WN. The controller MC controls the driving unit  6 D such that the support stand  6 T is rotated by the rotation amount. Accordingly, the angle position of the notch WN can be corrected to the reference angle position. The controller MC controls the position of an end effector of the transfer unit TU 1  when receiving the workpiece W from the aligner AN, based on the amount of deviation of the central position of the workpiece W. Accordingly, the central position of the workpiece W coincides with a predetermined position on the end effector of the transfer unit TU 1 . 
     Referring to  FIG. 1  again, each of the load lock module LL 1  and the load lock module LL 2  is provided between the loader module LM and the transfer module TF. Each of the load lock module LL 1  and the load lock module LL 2  provides a preliminary depressurization chamber. 
     The transfer module TF is airtightly connected to the load lock module LL 1  and the load lock module LL 2  via gate valves. The transfer module TF provides a depressurization chamber capable of being depressurized. A transfer unit TU 2  is provided in the depressurization chamber. For example, the transfer unit TU 2  is an articulated robot having a transfer arm TUa and is controlled by the controller MC. The transfer unit TU 2  is configured to transfer the workpiece W between the load lock modules LL 1  and LL 2  and the process modules PM 1  to PM 6 , and between any two process modules among the process modules PM 1  to PM 6 . 
     The process modules PM 1  to PM 6  are airtightly connected to the transfer module TF via gate valves. Each of the process modules PM 1  to PM 6  is a processing apparatus configured to perform dedicated processing such as plasma processing with respect to the workpiece W. 
     A series of operations at the time of processing the workpiece W in the processing system  1  is exemplified as follows. The transfer unit TU 1  of the loader module LM takes out the workpiece W from any of the containers  4   a  to  4   d  and transfers the workpiece W to the aligner AN. Subsequently, the transfer unit TU 1  takes out the workpiece W of which the position has been adjusted from the aligner AN and transfers the workpiece W to one load lock module out of the load lock module LL 1  and the load lock module LL 2 . Subsequently, in the one load lock module, the pressure in the preliminary depressurization chamber is depressurized to a predetermined pressure. Subsequently, the transfer unit TU 2  of the transfer module TF takes out the workpiece W from the one load lock module and transfers the workpiece W to any of the process modules PM 1  to PM 6 . The workpiece W is processed by one or more process modules among the process modules PM 1  to PM 6 . The transfer unit TU 2  transfers the processed workpiece W from the process module to one load lock module out of the load lock module LL 1  and the load lock module LL 2 . Subsequently, the transfer unit TU 1  transfers the workpiece W from the one load lock module to any of the containers  4   a  to  4   d.    
     As described above, the processing system  1  includes the controller MC. The controller MC can be a computer including a processor, a storage device such as a memory, a display device, an input/output device, a communication device, and the like. A series of the above-described operations of the processing system  1  is realized by the controller MC controlling each portion of the processing system  1  in accordance with a program stored in the storage device. 
       FIG. 3  is a view illustrating an example of a plasma processing apparatus which can be employed as any of the process modules PM 1  to PM 6 . A plasma processing apparatus  10  illustrated in  FIG. 3  is a capacitive coupling-type plasma etching apparatus. The plasma processing apparatus  10  includes a substantially cylindrical chamber body  12 . For example, the chamber body  12  is formed of aluminum, and an inner wall surface thereof can be subjected to anodic oxidation. 
     The chamber body  12  is protected and grounded. A substantially cylindrical support portion  14  is provided on a bottom portion of the chamber body  12 . For example, the support portion  14  is formed of an insulating material. The support portion  14  is provided inside the chamber body  12  and extends upward from the bottom portion of the chamber body  12 . In addition, a stage ST is provided inside a chamber S provided by the chamber body  12 . The stage ST is supported by the support portion  14 . 
     The stage ST has a lower electrode LE and an electrostatic chuck ESC. The lower electrode LE includes a first plate  18   a  and a second plate  18   b . For example, the first plate  18   a  and the second plate  18   b  are formed of metal such as aluminum and have substantial disk shapes. The second plate  18   b  is provided on the first plate  18   a  and is electrically connected to the first plate  18   a.    
     The electrostatic chuck ESC is provided on the second plate  18   b . The electrostatic chuck ESC has a structure in which an electrode (conductive film) is disposed between a pair of insulating layers or insulating sheets and has a substantial disk shape. A DC power source  22  is electrically connected to the electrode of the electrostatic chuck ESC via a switch  23 . The electrostatic chuck ESC attracts the workpiece W by an electrostatic force such as a Coulomb force generated by a DC voltage from the DC power source  22 . Accordingly, the electrostatic chuck ESC can hold the workpiece W. 
     The focus ring FR is provided on a circumferential edge portion of the second plate  18   b . The focus ring FR is provided to surround the edge of the workpiece W and the electrostatic chuck ESC. The focus ring FR has a first portion P 1  and a second portion P 2  (refer to  FIG. 7 ). The first portion P 1  and the second portion P 2  have annular plate shapes. The second portion P 2  is a portion outside the first portion P 1 . The second portion P 2  has a greater thickness in the height direction than the first portion P 1 . An inner edge P 2   i  of the second portion P 2  has a diameter greater than the diameter of an inner edge P 1   i  of the first portion P 1 . The workpiece W is placed on the electrostatic chuck ESC such that an edge region thereof is positioned on the first portion P 1  of the focus ring FR. The focus ring FR can be formed of any of various types of materials such as silicon, silicon carbide, and silicon oxide. 
     A refrigerant flow channel  24  is provided in the second plate  18   b . The refrigerant flow channel  24  configures a temperature control mechanism. A refrigerant is supplied to the refrigerant flow channel  24  via a pipe  26   a  from a chiller unit provided outside the chamber body  12 . The refrigerant supplied to the refrigerant flow channel  24  returns to the chiller unit via a pipe  26   b . In this manner, the refrigerant circulates between the refrigerant flow channel  24  and the chiller unit. The temperature of the workpiece W supported by the electrostatic chuck ESC is controlled by controlling the temperature of the refrigerant. 
     A plurality (for example, three) of through holes  25  penetrating the stage ST are formed in the stage ST. The plurality of through holes  25  are formed inside the electrostatic chuck ESC in a plan view. In each of the through holes  25 , lift pins  25   a  are inserted.  FIG. 3  depicts one through hole  25  in which one lift pin  25   a  is inserted. The lift pin  25   a  is provided in the through hole  25  so as to be movable up and down. As the lift pins  25   a  are moved up, the workpiece W supported on the electrostatic chuck ESC is moved up. 
     The stage ST is formed with a plurality of (for example, three) through holes  27  penetrating the stage ST (lower electrode LE) at a position outside the electrostatic chuck ESC in a plan view. In each of the through holes  27 , lift pins  27   a  are inserted.  FIG. 3  depicts one through hole  27  in which one lift pin  27   a  is inserted. The lift pin  27   a  is provided in the through hole  27  so as to be movable up and down. The upward movement of the lift pin  27   a  moves up the focus ring FR supported on the second plate  18   b.    
     In addition, a gas supply line  28  is provided in the plasma processing apparatus  10 . The gas supply line  28  supplies heat transfer gas, for example, He gas, from a heat transfer gas supply mechanism to a space between the top surface of the electrostatic chuck ESC and the back surface of the workpiece W. 
     In addition, the plasma processing apparatus  10  includes an upper electrode  30 . The upper electrode  30  is disposed above the stage ST to face the stage ST. The upper electrode  30  is supported by an upper portion of the chamber body  12  via an insulation shielding member  32 . The upper electrode  30  can include a top plate  34  and a support body  36 . The top plate  34  faces the chamber S. A plurality of gas discharge holes  34   a  are provided in the top plate  34 . The top plate  34  can be formed of silicon or quartz. Otherwise, the top plate  34  can be configured by forming a plasma resistant film such as yttrium oxide on the outer surface of an aluminum-made base material. 
     The support body  36  detachably supports the top plate  34 . For example, the support body  36  can be formed of a conductive material such as aluminum. The support body  36  may have a water-cooling structure. A gas diffusion chamber  36   a  is provided inside the support body  36 . A plurality of gas flow holes  36   b  communicating with the gas discharge holes  34   a  extend downward from the gas diffusion chamber  36   a . In addition, a gas introduction port  36   c  introducing processing gas to the gas diffusion chamber  36   a  is formed in the support body  36 . A gas supply pipe  38  is connected to the gas introduction port  36   c.    
     A gas source group  40  is connected to the gas supply pipe  38  via a valve group  42  and a flow-rate controller group  44 . The gas source group  40  contains a plurality of gas sources for plural types of gases. The valve group  42  includes a plurality of valves. The flow-rate controller group  44  includes a plurality of flow-rate controllers such as mass-flow controllers. Each of the plurality of gas sources of the gas source group  40  is connected to the gas supply pipe  38  via the corresponding valve of the valve group  42  and the corresponding flow-rate controller of the flow-rate controller group  44 . 
     In addition, in the plasma processing apparatus  10 , a deposit shield  46  is detachably provided along an inner wall of the chamber body  12 . The deposit shield  46  is also provided on the outer periphery of the support portion  14 . The deposit shield  46  prevents by-products (deposits) of etching from adhering to the chamber body  12 . The deposit shield  46  can be configured by covering an aluminum material with ceramics such as yttrium oxide. 
     An exhaust plate  48  is provided on the bottom portion side of the chamber body  12 , that is, between the support portion  14  and a side wall of the chamber body  12 . For example, the exhaust plate  48  can be configured by covering an aluminum material with ceramics such as yttrium oxide. A plurality of holes penetrating the exhaust plate  48  in the plate-thickness direction is formed in the exhaust plate  48 . An exhaust port  12   e  is provided below the exhaust plate  48 , that is, in the chamber body  12 . An exhaust unit  50  is connected to the exhaust port  12   e  via an exhaust pipe  52 . The exhaust unit  50  has a pressure adjustment valve and a vacuum pump such as a turbo-molecular pump and can depressurize the space inside the chamber body  12  to a desired vacuum degree. In addition, an opening  12   g  for transfer-in and transfer-out of the workpiece W is provided in the side wall of the chamber body  12 . The opening  12   g  can be opened and closed by a gate valve  54 . 
     In addition, the plasma processing apparatus  10  further includes a first high frequency power source  62  and a second high frequency power source  64 . The first high frequency power source  62  is a power source which generates a first high frequency wave for generating plasma, and generates, for example, a high frequency wave having a frequency ranging from 27 to 100 MHz. The first high frequency power source  62  is connected to the upper electrode  30  via a matching unit  66 . The matching unit  66  has a circuit for matching output impedance of the first high frequency power source  62  and input impedance on a load side (upper electrode  30  side) together. The first high frequency power source  62  may be connected to the lower electrode LE via the matching unit  66 . 
     The second high frequency power source  64  is a power source which generates a second high frequency wave for attracting ion to the workpiece W, and generates, for example, a high frequency wave having a frequency within a range of 400 kHz to 13.56 MHz. The second high frequency power source  64  is connected to the lower electrode LE via a matching unit  68 . The matching unit  68  has a circuit for matching output impedance of the second high frequency power source  64  and input impedance on the load side (lower electrode LE side) together. 
     In the plasma processing apparatus  10 , a gas from one or more gas sources selected from the plurality of gas sources is supplied to the chamber S. In addition, the pressure of the chamber S is set to a predetermined pressure by the exhaust unit  50 . Moreover, a gas inside the chamber S is excited by the first high frequency from the first high frequency power source  62 . Accordingly, plasma is generated. The workpiece W is processed by the generated active species. As necessary, ion may be attracted to the workpiece W due to a bias based on the second high frequency wave of the second high frequency power source  64 . 
     Hereinafter, the measuring instrument will be described.  FIG. 4  illustrates a plan view of the measuring instrument viewed from an upper surface side.  FIG. 5  illustrates a plan view of the measuring instrument viewed from a bottom surface side. The measuring instrument  100  illustrated in  FIGS. 4 and 5  includes a base substrate  102 . For example, the base substrate  102  is formed of silicon and has a shape which is the same as that of the workpiece W, that is, a substantial disk shape. The diameter of the base substrate  102  is a diameter which is the same as that of the workpiece W, for example, 300 mm. The shape and the size of the measuring instrument  100  are defined by the shape and the size of the base substrate  102 . Therefore, the measuring instrument  100  has the shape which is the same as that of the workpiece W, and has the size which is the same as that of the workpiece W. In addition, a notch  102 N (or different type of marker) is formed at the edge of the base substrate  102 . 
     A plurality of first sensors  104 A to  104 C for measuring electrostatic capacities are provided in the base substrate  102 . The plurality of first sensors  104 A to  104 C are arranged along the edge of the base substrate  102 , for example, at equal distances in the whole periphery of the edge. Specifically, each of the plurality of first sensors  104 A to  104 C is provided along the edge of the upper surface side of the base substrate  102 . The front side end surface of each of the plurality of first sensors  104 A to  104 C is along the side surface of the base substrate  102 . 
     In addition, a plurality of second sensors  105 A to  105 C for measuring electrostatic capacities are provided in the base substrate  102 . The plurality of second sensors  105 A to  105 C are arranged along the edge of the base substrate  102 , for example, at equal distances in the whole periphery of the edge. Specifically, each of the plurality of second sensors  105 A to  105 C is provided along the edge of the bottom surface side of the base substrate  102 . Each sensor electrode  161  of the plurality of second sensors  105 A to  105 C is along the bottom surface of the base substrate  102 . The second sensors  105 A to  105 C and the first sensors  104 A to  104 C are alternately arranged in the peripheral direction at intervals of 60°. 
     A circuit board  106  is provided at the center of the upper surface of the base substrate  102 . Between the circuit board  106  and the plurality of first sensors  104 A to  104 C, wiring groups  108 A to  108 C for electrically connecting the circuit board  106  and the plurality of first sensors  104 A to  104 C to each other are provided. In addition, between the circuit board  106  and the plurality of second sensors  105 A to  105 C, wiring groups  208 A to  208 C for electrically connecting the circuit board  106  and the plurality of second sensors  105 A to  105 C to each other are provided. The circuit board  106 , the wiring groups  108 A to  108 C, and the wiring groups  208 A to  208 C are covered with the cover  103 . 
     Hereinafter, the first sensor will be described in detail.  FIG. 6  is a perspective view illustrating an example of the sensor.  FIG. 7  is a sectional view taken along line VII-VII in  FIG. 6 . The first sensor  104  illustrated in  FIGS. 6 and 7  is a sensor utilized as the plurality of first sensors  104 A to  104 C of the measuring instrument  100  and is configured as a chip component in an example. In the description below, an XYZ orthogonal coordinate system will be adopted as a reference, as necessary. An X-direction indicates the forward direction of the first sensor  104 . A Y-direction indicates a direction orthogonal to the X-direction, that is, the width direction of the first sensor  104 . A Z-direction indicates a direction orthogonal to the X-direction and the Y-direction, that is, the upward direction of the first sensor  104 .  FIG. 7  illustrates the focus ring FR together with the first sensor  104 . 
     The first sensor  104  includes an electrode  141 , a guard electrode  142 , a sensor electrode  143 , a substrate portion  144 , and an insulation region  147 . 
     The substrate portion  144  is made of, for example, borosilicate glass or quartz. The substrate portion  144  has a top surface  144   a , a lower surface  144   b , and a front side end surface  144   c . The guard electrode  142  is provided below the lower surface  144   b  of the substrate portion  144  and extends in the X-direction and the Y-direction. In addition, the electrode  141  is provided below the guard electrode  142  via the insulation region  147  and extends in the X-direction and the Y-direction. For example, the insulation region  147  is formed of SiO 2 , SiN, Al 2 O 3 , or polyimide. 
     The front side end surface  144   c  of the substrate portion  144  is formed in a stepped shape. A lower portion  144   d  of the front side end surface  144   c  protrudes toward the focus ring FR side beyond an upper portion  144   u  of the front side end surface  144   c . The sensor electrode  143  extends along the upper portion  144   u  of the front side end surface  144   c . In one exemplary embodiment, the upper portion  144   u  and the lower portion  144   d  of the front side end surface  144   c  are curved surfaces each having a predetermined curvature. In other words, the upper portion  144   u  of the front side end surface  144   c  has a constant curvature at any position of the upper portion  144   u , and the curvature of the upper portion  144   u  is a reciprocal of the distance between a central axis AX 100  of the measuring instrument  100  and the upper portion  144   u  of the front side end surface  144   c . In addition, the lower portion  144   d  of the front side end surface  144   c  has a constant curvature at any position of the lower portion  144   d , and the curvature of the lower portion  144   d  is a reciprocal of the distance between the central axis AX 100  of the measuring instrument  100  and the lower portion  144   d  of the front side end surface  144   c.    
     The sensor electrode  143  is provided along the upper portion  144   u  of the front side end surface  144   c . In one exemplary embodiment, a front surface  143   f  of the sensor electrode  143  is also curved. In other words, the front surface  143   f  of the sensor electrode  143  has a constant curvature at any position of the front surface  143   f , and the curvature is a reciprocal of the distance between the central axis AX 100  of the measuring instrument  100  and the front surface  143   f.    
     In a case where the first sensor  104  is used as the sensor of the measuring instrument  100 , the electrode  141  is connected to a wiring  181 , the guard electrode  142  is connected to a wiring  182 , and the sensor electrode  143  is connected to a wiring  183 . 
     In the first sensor  104 , the sensor electrode  143  is shielded from the lower portion of the first sensor  104  by the electrode  141  and the guard electrode  142 . Therefore, according to the first sensor  104 , the electrostatic capacity can be measured with high directivity in a particular direction, that is, in a direction in which the front surface  143   f  of the sensor electrode  143  is oriented (X-direction). 
     Hereinafter, the second sensors will be described in detail.  FIG. 8  is a partially enlarged view of  FIG. 5  and illustrates one second sensor. The edge of the sensor electrode  161  has a partially arc shape. In other words, the sensor electrode  161  has a planar shape which is defined by an inner edge (second edge)  161   a  and an outer edge (first edge)  161   b  which are two arcs having radiuses different from each other around the central axis AX 100 . The outer edge  161   b  on the outer side in the radial direction in each sensor electrode  161  of the plurality of second sensors  105 A to  105 C extends on a common circle. In addition, the inner edge  161   a  on the inner side in the radial direction in each sensor electrode  161  of the plurality of second sensors  105 A to  105 C extends on another common circle. The curvature of a part of the edge of the sensor electrode  161  coincides with the curvature of the edge of the electrostatic chuck ESC. In one exemplary embodiment, the curvature of the outer edge  161   b  forming the edge on the outer side in the radial direction in the sensor electrode  161  coincides with the curvature of the edge of the electrostatic chuck ESC. In addition, the curvature center of the outer edge  161   b , that is, the center of a circle on which the outer edge  161   b  extends shares the central axis AX 100 . 
     In one exemplary embodiment, each of the second sensors  105 A to  105 C further includes a guard electrode  162  that surrounds the sensor electrode  161 . The guard electrode  162  has a frame shape and surrounds the sensor electrode  161  over the whole periphery. The guard electrode  162  and the sensor electrode  161  are separated from each other such that an insulation region  164  is interposed therebetween. In addition, in one exemplary embodiment, each of the second sensors  105 A to  105 C further includes an electrode  163  that surrounds the guard electrode  162  on the outside of the guard electrode  162 . The electrode  163  has a frame shape and surrounds the guard electrode  162  over the whole periphery. The guard electrode  162  and the electrode  163  are separated from each other such that an insulation region  165  is interposed therebetween. 
     Hereinafter, the configuration of the circuit board  106  will be described.  FIG. 9  is a view illustrating a configuration of the circuit board of the measuring instrument. The circuit board  106  has a high frequency oscillator  171 , a plurality of C/V conversion circuits  172 A to  172 C, a plurality of C/V conversion circuits  272 A to  272 C, an A/D converter  173 , a processor (arithmetic unit)  174 , a storage device  175 , a communication device  176 , and a power source  177 . 
     Each of the plurality of first sensors  104 A to  104 C is connected to the circuit board  106  via the corresponding wiring group among the plurality of wiring groups  108 A to  108 C. In addition, each of the plurality of first sensors  104 A to  104 C is connected to the corresponding C/V conversion circuit among the plurality of CN conversion circuits  172 A to  172 C via several wirings included in the corresponding wiring group. Each of the plurality of second sensors  105 A to  105 C is connected to the circuit board  106  via the corresponding wiring group among the plurality of wiring groups  208 A to  208 C. In addition, each of the plurality of second sensors  105 A to  105 C is connected to the corresponding C/V conversion circuit among the plurality of C/V conversion circuits  272 A to  272 C via several wirings included in the corresponding wiring group. Hereinafter, one first sensor  104  having the same configuration as each of the plurality of first sensors  104 A to  104 C will be described. Similarly, one wiring group  108  having the same configuration as each of the plurality of wiring groups  108 A to  108 C will be described. One C/V conversion circuit  172  having the same configuration as each of the plurality of C/V conversion circuits  172 A to  172 C will be described. One second sensor  105  having the same configuration as each of the plurality of second sensors  105 A to  105 C will be described. One wiring group  208  having the same configuration as each of the plurality of wiring groups  208 A to  208 C will be described. One C/V conversion circuit  272  having the same configuration as each of the plurality of CN conversion circuits  272 A to  272 C will be described. 
     The wiring group  108  includes the wirings  181  to  183 . One end of the wiring  181  is connected to a pad  151  which is connected to the electrode  141 . The wiring  181  is connected to a ground potential line GL which is connected to a ground G of the circuit board  106 . The wiring  181  may be connected to the ground potential line GL via a switch SWG. In addition, one end of the wiring  182  is connected to a pad  152  which is connected to the guard electrode  142 , and the other end of the wiring  182  is connected to the C/V conversion circuit  172 . In addition, one end of the wiring  183  is connected to the pad  153  which is connected to the sensor electrode  143 , and the other end of the wiring  183  is connected to the C/V conversion circuit  172 . 
     The wiring group  208  includes the wirings  281  to  283 . One end of the wiring  281  is connected to the electrode  163 . The wiring  281  is connected to the ground potential line GL which is connected to the ground G of the circuit board  106 . The wiring  281  may be connected to the ground potential line GL via the switch SWG. In addition, one end of the wiring  282  is connected to the guard electrode  162 , and the other end of the wiring  282  is connected to the C/V conversion circuit  272 . In addition, one end of the wiring  283  is connected to the sensor electrode  161 , and the other end of the wiring  283  is connected to the C/V conversion circuit  272 . 
     The high frequency oscillator  171  is connected to the power source  177  such as a battery and is configured to receive electric power from the power source  177  to generate a high frequency signal. The power source  177  is also connected to the processor  174 , the storage device  175 , and the communication device  176 . The high frequency oscillator  171  has a plurality of output lines. The high frequency oscillator  171  applies the generated high frequency signal to the wiring  182 , the wiring  183 , the wiring  282 , and the wirings  283  via the plurality of output lines. Therefore, the high frequency oscillator  171  is electrically connected to the guard electrode  142  and the sensor electrode  143  of the first sensor  104 , and the high frequency signal from the high frequency oscillator  171  is applied to the guard electrode  142  and the sensor electrode  143 . In addition, the high frequency oscillator  171  is electrically connected to the sensor electrode  161  and the guard electrode  162  of the second sensor  105 , and the high frequency signal from the high frequency oscillator  171  is applied to the sensor electrode  161  and the guard electrode  162 . 
     The wiring  182  and the wiring  183  are connected to an input of the C/V conversion circuit  172 . That is, the guard electrode  142  and the sensor electrode  143  of the first sensor  104  are connected to the input of the C/V conversion circuit  172 . In addition, the sensor electrode  161  and the guard electrode  162  are connected to the inputs of the C/V conversion circuits  272 , respectively. The C/V conversion circuit  172  and the C/V conversion circuit  272  are configured to generate a voltage signal having an amplitude that corresponds to the potential difference at the input and output the voltage signal. As the electrostatic capacity of the sensor electrode connected to the CN conversion circuit  172  becomes greater, the magnitude of the voltage of the voltage signal output by the C/V conversion circuit  172  increases. Similarly, as the electrostatic capacity of the sensor electrode connected to the C/V conversion circuit  272  becomes greater, the magnitude of the voltage of the voltage signal output by the C/V conversion circuit  272  increases. The high frequency oscillator  171 , the wiring  282 , the wiring  283 , and the C/V conversion circuit  272  are connected in the same manner as the high frequency oscillator  171 , the wiring  182 , the wiring  183 , and the C/V conversion circuit  172 . 
     The outputs of the C/V conversion circuit  172  and the C/V conversion circuit  272  are connected to the input of the A/D converter  173 . In addition, the A/D converter  173  is connected to the processor  174 . The A/D converter  173  is controlled based on a control signal from the processor  174 , converts the output signal (voltage signal) of the C/V conversion circuit  172  and the output signal (voltage signal) of the C/V conversion circuit  272  to digital values, and outputs the converted digital values to the processor  174  as detection values. 
     The storage device  175  is connected to the processor  174 . The storage device  175  is a storage device such as a volatile memory and is configured to store measurement data, which will be described later. In addition, another storage device  178  is connected to the processor  174 . The storage device  178  is a storage device such as a non-volatile memory and stores a program which is read and executed by the processor  174 . 
     The communication device  176  is a communication device that is compliant with any wireless communication standard. For example, the communication device  176  is compliant with Bluetooth (registered trademark). The communication device  176  is configured to wirelessly transmit the measurement data stored in the storage device  175 . 
     The processor  174  is configured to control each part of the measuring instrument  100  by executing the above-described program. For example, the processor  174  controls the supply of the high frequency signal from the high frequency oscillator  171  to the guard electrode  142 , the sensor electrode  143 , the sensor electrode  161 , and the guard electrode  162 . The processor  174  controls power supply from the power source  177  to the storage device  175 , power supply from the power source  177  to the communication device  176 , and the like. Furthermore, the processor  174  acquires the measurement value of the first sensor  104  and the measurement value of the second sensor  105  based on the detection value input from the A/D converter  173  by executing the above-described program. 
     In the above-described measuring instrument  100 , in a state where the measuring instrument  100  is disposed in a region surrounded by the focus ring FR, the plurality of sensor electrodes  143  and guard electrodes  142  face the inner edge of the focus ring FR. The measurement values generated based on the voltage difference between the signal of the sensor electrode  143  and the signal of the guard electrode  142  represents the electrostatic capacities that reflect the distances between each of the plurality of sensor electrodes  143  and the focus ring. An electrostatic capacity C is represented by C=εS/d. ε is a dielectric constant of a medium between the front surface  143   f  of the sensor electrode  143  and the inner edge of the focus ring FR. S indicates the area of the front surface  143   f  of the sensor electrode  143 . d can be regarded as the distance between the front surface  143   f  of the sensor electrode  143  and the inner edge of the focus ring FR. Therefore, according to the measuring instrument  100 , the measurement data that reflects a relative positional relationship between the measuring instrument  100  copying the workpiece W, and the focus ring FR can be obtained. For example, the plurality of measurement values acquired by the measuring instrument  100  become smaller as the distances between the front surfaces  143   f  of the sensor electrode  143  and the inner edge of the focus ring FR increases. 
     Further, in a state where the measuring instrument  100  is placed on the electrostatic chuck ESC, the plurality of sensor electrodes  161  face the electrostatic chuck ESC. Considering one sensor electrode  161 , in a case where the sensor electrode  161  is deviated radially outward with respect to the electrostatic chuck ESC, the electrostatic capacity measured by the sensor electrode  161  becomes smaller than the electrostatic capacity in a case where the measuring instrument  100  is transferred at a predetermined transfer position. In addition, in a case where the sensor electrode  161  is deviated radially inward with respect to the electrostatic chuck ESC, the electrostatic capacity measured by the sensor electrode  161  becomes greater than the electrostatic capacity in a case where the measuring instrument  100  is transferred at a predetermined transfer position. 
     Hereinafter, a method for obtaining a first amount of deviation which is an amount of deviation of the central position (central axis AX 100 ) of the measuring instrument  100  disposed in the region with respect to the central position (central axis AXF) of the region surrounded by the focus ring FR, will be described. 
       FIG. 10  schematically illustrates the positional relationship between the focus ring FR and the measuring instrument  100  disposed inside the focus ring FR. In  FIG. 10 , the inner periphery of the focus ring FR and the edge of the measuring instrument  100  are illustrated. In  FIG. 10 , an orthogonal coordinate system based on the X axis and the Y axis with the central axis AXF of the focus ring FR as the origin, and an orthogonal coordinate system based on an X′ axis and a Y′ axis with the central axis AX 100  of the measuring instrument  100  as the origin, are illustrated. In the illustrated example, the Y′ axis is set to pass through the first sensor  104 A. 
     As illustrated in the drawing, the amount of deviation between the central axis AXF of the focus ring FR and the central axis AX 100  of the measuring instrument  100  is represented by ΔXa and ΔYa. Hereinafter, a method for deriving ΔXa and ΔYa will be described. In one exemplary embodiment, three first sensors  104 A,  104 B, and  104 C are equally provided on the peripheral edge of the base substrate  102  at intervals of 120° in the peripheral direction. Accordingly, a sum A of each shortest distance from the plurality of sensor electrodes  143  to the inner peripheral surface of the focus ring FR is a constant value. In the illustrated example, the inner diameter D f  of the focus ring FR is 302 mm, and the diameter D w  of the measuring instrument  100  is 300 mm. The shortest distance from the first sensor  104 A to the inner peripheral surface of the focus ring FR is G A . The shortest distance from the first sensor  104 B to the inner peripheral surface of the focus ring FR is G B . The shortest distance from the first sensor  104 C to the inner peripheral surface of the focus ring FR is G C . In this case, Equation (3) below is established.
 
(( D   f   −D   w )/2)×3= G   A   +G   B   +G   C =3.00 mm  Equation (3)
 
     Here, as described above, since the electrostatic capacity C is represented by C=εS/d, the distance d is represented by d=εS/C. When “εS” is a constant a, the distance d is d=a/C. The distance d corresponds to G A , G B , and G C  in the equation above. When the measurement value (electrostatic capacity) by the first sensor  104 A is C A , the measurement value by the first sensor  104 B is C B , and the measurement value by the first sensor  104 C is C C , G A =a/C A , G B =a/C B , and G C =a/C C  is established. In other words, Equation (3) is converted into Equation (4) below.
 
( a/C   A )+( a/C   B )+( a/C   C )=3.00 mm  (4)
 
     In addition, Equation (4) can be generalized similar to Equation (5) below. In other words, when the measurement values by the N first sensors  104  are Ci (i=1, 2, 3, . . . , and N), Equation (5) is established. In a case where the sum A of the shortest distances from the N first sensors  104  to the inner peripheral surface of the focus ring FR is a constant value, the sum A can be calculated by ((D f −D w )/2)×N. 
     
       
         
           
             
               
                 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         1 
                       
                       N 
                     
                     ⁢ 
                     
                       a 
                       
                         C 
                         i 
                       
                     
                   
                   = 
                   A 
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     In a case of deriving ΔXa and ΔYa, first, the respective measurement values C A , C B , and C C  of the first sensors  104 A,  104 B, and  104 C are acquired. By substituting the measurement values C A , C B , and C C  into Equation (4) above, the constant a can be obtained. The distances G A , G B , and G C  are derived based on the constant a and each of the measurement values C A , C B , and C C . 
     As described in one exemplary embodiment, in a case where the difference between the inner diameter D f  of the focus ring FR and the diameter D w  of the measuring instrument  100  is sufficiently smaller than the inner diameter D f  of the focus ring FR, Expression (6) below is established. In other words, the magnitude of G A  can be approximated as a distance Y 1  from the inner periphery of the focus ring FR on the Y axis to the edge of the measuring instrument  100 .
 
 G   A   ≈Y   1   (6)
 
     When the distance from the position symmetrical to the first sensor  104 A around the origin (central axis AX 100 ) to the inner periphery of the focus ring FR is G A ′, similarly, Expression (7) below is established. In other words, the magnitude of G A ′ can be approximated to a distance Y 2  from the inner periphery of the focus ring FR on the Y axis to the edge of the measuring instrument  100 .
 
 G   A   ′≈Y   2   (7)
 
     Here, both Y 1  and Y 2  are distances on the Y axis. Therefore, the sum of Y 1  and Y 2  can be approximated as the difference between the inner diameter D f  of the focus ring FR and the diameter D w  of the measuring instrument  100 . In other words, Expression (8) below is established based on Expressions (6) and (7).
 
 Y   1   +Y   2   ≈G   A   +G   A ′≈2  (8)
 
     Since ΔYa can be defined as ½ of the difference between Y 2  and Y 1 , ΔYa can be obtained from the distance G A  as illustrated in Equation (9) below.
 
Δ Ya =( Y   2   −Y   1 )/2=1− G   A   (9)
 
     Similarly, when the distances from the edge of the measuring instrument  100  to the inner periphery of the focus ring FR on the X axis are X 1  and X 2 , respectively, Expression (10) below is established.
 
 X   1   +X   2 ≈2  (10)
 
     Further, the ratio of the shortest distance G B  from the first sensor  104 B to the focus ring FR and the shortest distance G C  from the first sensor  104 C to the focus ring FR is represented by Equation (11) below.
 
 X   1   :X   2   =G   B   :G   C   (11)
 
     Here, assuming that G C +G B =Z, X 1  and X 2  are represented by Equations (12) and (13) below from Equations (10) and (11), respectively.
 
 X   1 =2 G   B   /Z= 2 G   B /( G   C   +G   B )  (12)
 
 X   2 =2 G   C   /Z= 2 G   C /( G   C   +G   B )  (13)
 
     Accordingly, since ΔXa can be defined as Equation (14) below, ΔXa can be obtained from the distances G C  and G B .
 
Δ Xa =( X   2   −X   1 )/2=( G   C   −G   B )/( G   C   +G   B )  (14)
 
     As described above, in one exemplary embodiment, the first amount of deviation which is an amount of deviation between the central axis AXF of the focus ring FR and the central axis AX 100  of the measuring instrument  100  disposed inside the focus ring FR, is obtained. The first amount of deviation can be calculated as the amount of deviation ΔXa in the direction along the X axis and the amount of deviation ΔYa in the direction along the Y axis. 
     Next, a method for obtaining the second amount of deviation which is an amount of deviation between the central position (central axis AXE) of the electrostatic chuck ESC and the central axis AX 100  of the measuring instrument  100  disposed on the electrostatic chuck ESC will be described. 
       FIG. 11  illustrates a sectional view of the electrostatic chuck and illustrates a state where the workpiece is placed on the electrostatic chuck. In one exemplary embodiment, the electrostatic chuck ESC has a ceramic body and an electrode E provided in the body. The body has a disc shape and has a peripheral edge that extends in the peripheral direction with respect to the center of the electrostatic chuck ESC. The electrode E has a disk shape and has a peripheral edge that extends in the peripheral direction with respect to the center of the electrostatic chuck ESC inside the peripheral edge of the body. The electrostatic chuck ESC has a placement region R on which the workpiece W and the measuring instrument  100  are placed. The placement region R has a circular edge. The workpiece W and the measuring instrument  100  have diameters greater than the diameter of the placement region R. 
       FIGS. 12A to 12C  are a view illustrating the transfer position of the measuring instrument with respect to the placement region of the electrostatic chuck.  FIG. 12A  illustrates an arrangement in a case where the central position of the measuring instrument  100  and the central position of the electrostatic chuck coincide with each other.  FIGS. 12B and 12C  illustrate an arrangement in a case where the central position of the measuring instrument  100  and the central position of the electrostatic chuck are deviated from each other. In  FIG. 12C , the focus ring FR and the measuring instrument  100  interfere with each other. In other words, in practice, the arrangement illustrated in  FIG. 12C  is achieved. 
     As illustrated in  FIG. 12A , in a case where the central axis AX 100  of the measuring instrument  100  and the central axis AXE of the electrostatic chuck ESC coincide with each other, the outer edge  161   b  (refer to  FIG. 8 ) of the sensor electrode  161  and the outer edge of the electrostatic chuck ESC coincide with each other. In this case, the inner edge  161   a  (refer to  FIG. 8 ) of the sensor electrode  161  may coincide with the outer edge of the electrode E. In other words, the outer edge  161   b  of the sensor electrode  161  extends on a first circle around the central axis AX 100 , and the first circle has the same radius as the radius of the peripheral edge of the body of the electrostatic chuck ESC. The inner edge  161   a  of the sensor electrode  161  extends on a second circle around the central axis AX 100 , and the second circle has the same radius as the radius of the peripheral edge of the electrode E of the electrostatic chuck ESC. 
     As described above, the electrostatic capacity C is represented by C=εS/d. Here, the distance d is a distance from the sensor electrode  161  to the surface of the electrostatic chuck ESC and is constant. Meanwhile, S is the area of a part where the sensor electrode  161  and the electrostatic chuck ESC face each other. Therefore, the S varies depending on the positional relationship between the measuring instrument  100  and the electrostatic chuck ESC. For example, as illustrated in  FIG. 12B , in the arrangement where an overlap length W X  between the sensor electrode  161  and the electrostatic chuck ESC is small, S is small. Here, the overlap length can be defined as the shortest distance from the peripheral edge of the electrostatic chuck ESC to the inner edge  161   a  of the sensor electrode  161 . 
     The shape of the sensor electrode  161  can be approximated by a rectangle having sides in a radial direction of a circle around the central axis AX 100  and a direction orthogonal to the radial direction. In this case, S is represented by the product of the length of the side in the direction orthogonal to the radial direction and the overlap length W X . When the length of the side in the direction orthogonal to the radial direction is Sa, S is represented by the product of Sa and W X . In this case, C=εS/d can be transformed as C=E·Sa·W X /d. Accordingly, the overlap length W X  is represented by Equation (15) below.
 
 W   X =( d /(ε· Sa )) C   (15)
 
     Here, by setting d/(ε·Sa) as a constant b, Equation (16) below is derived.
 
 W   X   =b·C   (16)
 
     As illustrated in  FIG. 12C , the overlap length W X  is zero in a state where the inner edge  161   a  of the sensor electrode  161  and the outer edge of the electrostatic chuck ESC coincide with each other. In this case, theoretically, the electrostatic capacity C measured by the sensor electrode  161  is zero. Therefore, in one exemplary embodiment, the second sensor  105  is calibrated such that the electrostatic capacity C becomes zero when the overlap length W X  is zero. Meanwhile, in a case where the sensor electrode  161  moves to the central axis AXE side of the electrostatic chuck ESC from the state illustrated in  FIG. 12A , the overlap length W X  becomes larger than the length of the sensor electrode  161  in the radial direction. In this case, even when the overlap length W X  increases, the value of S does not change. However, since the electrode E is disposed on the electrostatic chuck ESC, the electrostatic capacity C can be increased as the overlap length W X  increases. 
       FIG. 13  is a graph illustrating a relationship between the overlap length and the measurement value that represents the electrostatic capacity C. In the graph of  FIG. 13 , for example, the measurement values measured by the second sensors  105 A to  105 C are plotted for each overlap length W X . The measurement values of the second sensors  105 A to  105 C are ch.01 to ch.03, respectively. Moreover, in  FIG. 13 , an ideal line that represents the relationship between the overlap length and the electrostatic capacity is illustrated. The measurement values (electrostatic capacities) measured by the three second sensors rise substantially the same as the ideal line even when the overlap length W X  is larger than the length of the sensor electrode  161  in the radial direction. In one exemplary embodiment, the difference between the inner diameter of the focus ring FR and the diameter of the measuring instrument  100  is 2 mm. Therefore, in the actual operation region, the overlap length W X  is between 1.00 mm and 3.00 mm. 
       FIG. 14  schematically illustrates the positional relationship between the electrostatic chuck ESC and the measuring instrument  100  disposed at a position on the electrostatic chuck ESC. In  FIG. 14 , an outer edge of the electrostatic chuck ESC and a circle (second circle  100 N) along the inner edge of the sensor electrode  161  in the measuring instrument  100  is illustrated. In  FIG. 14 , an orthogonal coordinate system based on the X axis and the Y axis with the central position of the electrostatic chuck ESC as the origin, and an orthogonal coordinate system based on the X′ axis and the Y′ axis with the central axis AX 100  of the measuring instrument  100  as the origin, are illustrated. In the illustrated example, the Y′ axis is set to pass through the second sensor  105 A and the central position. 
     As illustrated in the drawing, the amount of deviation between the central position of the electrostatic chuck ESC and the central axis AX 100  of the measuring instrument  100  is represented by ΔXb and ΔYb. Hereinafter, a method for deriving ΔXb and ΔYb will be described. In one exemplary embodiment, the three second sensors  105 A,  105 B, and  105 C are equally disposed at intervals of 120° in the peripheral direction at the circumferential edge of the base substrate  102  such that a sum B of the shortest distances from the outer edge of the electrostatic chuck ESC to the inner edges of the plurality of sensor electrodes  161  has a constant value. In the illustrated example, a diameter D e  of the electrostatic chuck ESC is 297 mm, a diameter D w  of the circle along the inner edge of the sensor electrode  161  is 297 mm, and the length W s  of the sensor electrode  161  in the radial direction is 2.00 mm. When the overlap length of the sensor electrode  161  of the second sensor  105 A is W A , the overlap length of the sensor electrode  161  of the second sensor  105 B is W B , and the overlap length of the sensor electrode  161  of the second sensor  105 C is W C , Equation (17) below is established.
 
( W   s −( W   d   −D   e )/2)×3= W   A   +W   B   +W   C =6.00 mm   Equation (17)
 
     Here, since Equation (16) is established as described above, when the measurement value (electrostatic capacity) by the second sensor  105 A is D A , the measurement value by the second sensor  105 B is D B , and the measurement value by the second sensor  105 C is D C , W A =b·D A , W B =b·D B , and W C =b·D C  are established. In other words, Equation (17) is converted into Equation (18).
 
( b·D   A )+( b·D   B )+( b·D   C )=6.00 mm  (18)
 
     The Equation (18) can be generalized similar to Equation (19) below using M measurement values Di (i=1, 2, 3, . . . , and M) in a case where the sum B of the overlap lengths of each sensor electrode  161  is a constant value. 
     In other words, when the measurement values by the M second sensors  105  are Di (i=1, 2, 3, . . . , and M), Equation (19) is established. In a case where the sum B of the overlap lengths of each sensor electrode  161  has a constant value, the sum B can be calculated by (W s −(W d −D e )/2)×M. 
     
       
         
           
             
               
                 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         1 
                       
                       M 
                     
                     ⁢ 
                     
                       b 
                       · 
                       
                         D 
                         i 
                       
                     
                   
                   = 
                   B 
                 
               
               
                 
                   ( 
                   19 
                   ) 
                 
               
             
           
         
       
     
     In a case of deriving ΔXb and ΔYb, first, the respective measurement values D A , D B , and D C  of the second sensors  105 A,  105 B, and  105 C are acquired. By substituting the measurement values D A , D B , and D C  into Equation (18) above, the constant b can be obtained. Then, W A , W B , and W e  are derived from the constant b and the respective measurement values D A , D B , and D C . 
     The magnitude of W A  can be approximated to the distance Y 1  from the outer edge of the electrostatic chuck ESC on the Y axis to the second circle  100 N. In other words, Equation (20) below is established.
 
 W   A   ≈Y   1   (20)
 
     When the distance from the position symmetrical to the second sensor  105 A around the origin (central axis AX 100 ) to the second circle  100 N to the outer edge of the electrostatic chuck ESC is W A ′, similarly, Expression (21) below is established. In other words, the magnitude of W A ′ can be approximated to the distance Y 2  from the outer edge of the electrostatic chuck ESC on the Y axis to the second circle  100 N.
 
 W   A   ′≈Y   2   (21)
 
     Here, both Y 1  and Y 2  are distances on the Y axis. Therefore, the sum of Y 1  and Y 2  can be approximated to the difference between the diameter of the electrostatic chuck ESC and the diameter of the second circle  100 N. In other words, Expression (22) below is established.
 
 Y   1   +Y   2   ≈W   A   +W   A ′≈4  (22)
 
     Since ΔYb can be defined as ½ of the difference between Y 2  and Y 1 , ΔYb can be obtained from the distance W A  as illustrated in Equation (23) below.
 
Δ Yb =( Y   1   −Y   2 )/2= W   A −2  (23)
 
     Similarly, when the distances from the second circle  100 N to the outer periphery of the electrostatic chuck ESC on the X axis are X 1  and X 2 , respectively, Expression (24) below is established.
 
 X   1   +X   2 ≈4  (24)
 
     Further, the ratio between the overlap length W B  in the second sensor  105 B and the overlap length W C  in the second sensor  105 C is represented by Equation (25) below.
 
 X   1   :X   2   =W   B   :W   C   Equation (25)
 
     Here, assuming that W C +W B =Z, X 1  and X 2  are represented by Equations (26) and (27) below, respectively.
 
 X   1 =4 W   B   /Z= 4 W   B /( W   C   +W   B )  (26)
 
 X   2 =4 W   C   /Z= 4 W   C /( W   C   +W   B )  (27)
 
     Accordingly, since ΔXb can be defined as Equation (28) below, ΔXb can be obtained from the overlap lengths Wc and W B .
 
Δ Xb =( X   1   −X   2 )/2=2( W   B   −W   C )/( W   B   +W   C )  (28)
 
     As described above, in one exemplary embodiment, the second amount of deviation which is an amount of deviation between the central axis AXE of the electrostatic chuck ESC and the central axis AX 100  of the measuring instrument  100  disposed on the electrostatic chuck ESC is obtained. The second amount of deviation can be calculated as the amount of deviation ΔXb in the direction along the X axis and the amount of deviation ΔYb in the direction along the Y axis. 
     Next, a method for obtaining the third amount of deviation which is an amount of deviation of the central position of the focus ring with respect to the central position of the electrostatic chuck ESC will be described. In addition, in one exemplary embodiment, by using the third amount of deviation, the transfer position data of the focus ring FR by the transfer unit is calibrated.  FIG. 15  is a view schematically illustrating an example of a positional relationship of the electrostatic chuck ESC, the focus ring FR, and the measuring instrument  100 . In  FIG. 15 , the peripheral edge of the electrostatic chuck ESC, the inner edge of the focus ring FR, and the peripheral edge of the measuring instrument  100  are illustrated. As illustrated in  FIG. 15 , the electrostatic chuck ESC and the measuring instrument  100  are disposed in the inner region FRI of the focus ring FR. The measuring instrument  100  is disposed at a position on the electrostatic chuck ESC. 
     The first amount of deviation described above can be expressed as a vector VA from the central axis AXF of the focus ring FR toward the central axis AX 100  of the measuring instrument  100 . The vector VA is represented by VA=(ΔXa, ΔYa). Similarly, the second amount of deviation can be expressed as a vector VB from the central axis AXE of the electrostatic chuck ESC toward the central axis AX 100  of the measuring instrument  100 . The vector VB is represented by VB=(ΔXb, ΔYb). In this case, a vector VC from the central axis AXF of the focus ring FR to the central axis AXE of the electrostatic chuck ESC is VA−VB, and is represented by VC=(ΔXa−ΔXb, ΔYa−ΔYb). In other words, in a case where the third amount of deviation is obtained from the amount of deviation ΔXc in the direction along the X axis and the amount of deviation ΔYc in the direction along the Y axis, ΔXc is ΔXa−ΔXb, and ΔYc is ΔYa−ΔYb. As described above, in one exemplary embodiment, the third amount of deviation which is an amount of deviation between the central axis AXE of the electrostatic chuck ESC and the central axis AXF of the focus ring FR is obtained based on the first amount of deviation and the second amount of deviation. 
     Hereinafter, a transfer method of the focus ring FR in the transfer system S 1  will be described.  FIG. 16  is a flowchart illustrating a transfer method of the focus ring FR according to one exemplary embodiment. In a method MT illustrated in  FIG. 16 , as an example, a flow in a case of replacing the focus ring FR that has been consumed due to use with a new focus ring FR is illustrated. In a semiconductor manufacturing apparatus, such as the processing system  1 , since the focus ring is consumed due to use, periodic replacement is necessary. When replacing the focus ring, it is important to dispose the workpiece W and the focus ring FR in an optimal positional relationship in order to stabilize the productivity. In a case of confirming the installation position of the replaced focus ring, it is generally necessary to open the chamber. Therefore, the replacement work can be complicated. Here, it is desired to transfer the focus ring with high accuracy by a simple method. 
     As described above, the transfer unit TU 2  in the processing system  1  is controlled by the controller MC. In one exemplary embodiment, the transfer unit TU 2  can transfer the focus ring FR onto the second plate  18   b  based on the transfer position data transmitted from the controller MC. In addition, the transfer unit TU 2  can transfer the workpiece W and the measuring instrument  100  onto the placement region R of the electrostatic chuck ESC based on the transfer position data transmitted from the controller MC. 
     In one example, any of the process modules PM 1  to PM 6  may be used as a storage location for the focus ring FR. As described above, the process modules PM 1  to PM 6  are airtightly connected to the transfer module TF via gate valves. In this case, the focus ring FR can be replaced by the transfer unit TU 2  without opening the process module to the atmosphere. 
     In the method MT illustrated in  FIG. 16 , first, a step ST 1  is executed. In step ST 1 , the focus ring FR consumed due to use is transferred out from the process module. The focus ring FR is supported on the second plate  18   b . The upward movement of the lift pin  27   a  moves up the focus ring FR. By inserting the transfer arm TUa of the transfer unit TU 2  into the gap between the raised focus ring FR and the second plate  18   b , the focus ring FR is placed on the transfer arm TUa. The focus ring FR placed on the transfer arm TUa can be transferred to a predetermined position in the process module used as a storage location by the operation of the transfer unit TU 2 . 
     In subsequent step ST 2 , a new focus ring FR is transferred into the process module. For example, the transfer unit TU 2  transfers the new focus ring FR onto the second plate  18   b  such that the electrostatic chuck ESC is positioned inside the region surrounded by the focus ring FR. The new focus ring FR is transferred by the transfer unit TU 2  based on the transfer position data in a state of being placed on the transfer arm TUa. For example, the transfer position data may be coordinate data which is set in advance such that the central position of the focus ring FR coincides with the central position of the electrostatic chuck ESC. The transferred focus ring FR is supported by the lift pins  27   a , and is placed at a position surrounding the electrostatic chuck ESC as the lift pins  27   a  are lowered. 
     In the subsequent step ST 3 , the measuring instrument  100  is transferred to the inner region FRI of the transferred focus ring FR. Specifically, the transfer unit TU 1  transfers the measuring instrument  100  to one of the load lock module LL 1  and the load lock module LL 2 . The transfer unit TU 2  transfers the measuring instrument  100  to the process module from the load lock module based on the transfer position data, and the measuring instrument  100  is placed on the placement region R of the electrostatic chuck ESC. For example, the transfer position data is coordinate data which is set in advance such that the position of the central axis AX 100  of the measuring instrument  100  coincides with the central position of the placement region R. Any of the process modules PM 1  to PM 6  may be used as a storage location for the measuring instrument  100 . 
     In subsequent step ST 4 , the measurement value is acquired by the measuring instrument  100 . Specifically, the measuring instrument  100  acquires the plurality of digital values (measurement values) depending on the magnitude of the electrostatic capacities between the focus ring FR and each sensor electrode  161  of the first sensors  104 A to  104 C, and stores the plurality of digital values in the storage device  175 . In addition, the measuring instrument  100  acquires the plurality of digital values (measurement values) depending on the magnitude of the electrostatic capacities between the placement region R of the electrostatic chuck ESC and each sensor electrode  161  of the second sensors  105 A to  105 C, and stores the plurality of digital values in the storage device  175 . The plurality of digital values can be acquired at timing set in advance under the control of the processor  174 . 
     In subsequent step ST 5 , the measuring instrument  100  is transferred out from the process module and returns to any of the transfer module TF, the load lock modules LL 1 , LL 2 , the loader module LM, and the containers  4   a  to  4   d.    
     In subsequent step ST 6 , the first amount of deviation and the second amount of deviation are obtained using the above-described method for obtaining the amount of deviation based on the plurality of measurement values (measurement value group). In subsequent step ST 7 , the third amount of deviation which is an amount of deviation of the central axis AXF of the focus ring FR with respect to the central axis AXE of the electrostatic chuck ESC is obtained based on the first amount of deviation and the second amount of deviation which are obtained in step ST 6 . In steps ST 6  and ST 7  of one exemplary embodiment, first, the plurality of digital values stored in the storage device  175  are transmitted to the controller MC. The plurality of digital values may be transmitted from the communication device  176  to the controller MC in accordance with a command from the controller MC. Otherwise, the plurality of digital values may be transmitted to the controller MC at predetermined timing in accordance with the control of the processor  174  performed based on counting of a timer provided in the circuit board  106 . Subsequently, based on the received plurality of digital values, the controller MC obtains the first amount of deviation, the second amount of deviation, and the third amount of deviation. In addition, the first amount of deviation, the second amount of deviation, and the third amount of deviation may be obtained by the processor  174  of the measuring instrument  100 . In this case, the obtained first amount of deviation, the second amount of deviation, and third amount of deviation are transmitted to the controller MC. 
     In subsequent step ST 8 , it is determined whether or not the third amount of deviation exceeds a predetermined threshold value. In a case where it is determined that the third amount of deviation is equal to or less than the predetermined threshold value, it is confirmed that the focus ring FR has been accurately transferred. In this case, the method MT ends. Meanwhile, in a case where it is determined that the amount of deviation is larger than the threshold value, the process proceeds to step ST 9 . In step ST 9 , the transfer position of the focus ring FR is adjusted such that the central position of the electrostatic chuck ESC and the central position of the focus ring FR coincide with each other based on the third amount of deviation. For example, the transfer position data is revised by the controller MC such that the third amount of deviation is eliminated. In addition, the focus ring FR is transferred again by the transfer unit TU 2  such that the central position of the focus ring FR coincides with the central position of the electrostatic chuck ESC based on the revised transfer position data. In this case, for example, the focus ring FR is once transferred out from the second plate  18   b  to the process module used as a storage location. The focus ring FR is supported again by the transfer arm TUa, and the focus ring FR is transferred onto the second plate  18   b . At this time, the transfer position of the focus ring FR is adjusted by adjusting the transfer position data of the transfer arm TUa based on the third amount of deviation. In addition, in the position adjustment of the focus ring FR, the focus ring FR may not be returned to the storage location. For example, the focus ring may be supported by the transfer arm TUa, and the transfer position of the focus ring FR may be adjusted by moving the transfer arm TUa by the third amount of deviation. 
     As described above, when the position of the focus ring FR is adjusted in step ST 9 , the transfer position is subsequently confirmed. In other words, by executing the above-described steps ST 3  to ST 8  again, it is confirmed whether or not the third amount of deviation in the focus ring FR of which the transfer position has been adjusted exceeds a predetermined threshold value. In a case where it is confirmed that the focus ring FR has been transferred correctly, the method MT ends. Meanwhile, in a case where it is determined that the amount of deviation is larger than the threshold value, the process proceeds to step ST 9  again. 
     As described above, in the transfer method of one exemplary embodiment, after the focus ring FR is transferred onto the second plate  18   b , the measuring instrument  100  is transferred to the inner region FRI of the focus ring FR. The measuring instrument  100  acquires the plurality of measurement values (measurement value group) for obtaining the first amount of deviation and the second amount of deviation. In the method, the third amount of deviation which is an amount of deviation of the central position of the focus ring FR with respect to the central position of the electrostatic chuck ESC is obtained from the first amount of deviation and the second amount of deviation which are obtained based on the measurement value group. In addition, the transfer position of the focus ring FR is adjusted such that the central position of the electrostatic chuck ESC and the central position of the focus ring FR coincide with each other based on the third amount of deviation. In this manner, after the focus ring FR is transferred onto the second plate  18   b , the focus ring FR can be transferred with high accuracy by adjusting the transfer position of the focus ring FR based on the third amount of deviation. 
     In one exemplary embodiment, the transfer unit TU 2  may be disposed in the transfer module TF which is a space airtightly connected to the chamber body  12 . In this configuration, a focus ring FR can be transferred in the space airtightly connected to the chamber body  12 . In this case, the focus ring FR can be transferred and the position of the focus ring FR can be adjusted without opening the chamber body  12  to the atmosphere. 
     In one exemplary embodiment, step ST 8  of determining whether or not the third amount of deviation exceeds the threshold value is provided. In this case, when the third amount of deviation exceeds the threshold value, in step ST 9  of adjusting the transfer position of the focus ring FR, the position of the focus ring FR may be adjusted. By providing the threshold value for the third amount of deviation, unnecessary position adjustment can be omitted. 
     In one exemplary embodiment, it is confirmed whether or not the third amount of deviation exceeds the threshold value in the focus ring FR of which the transfer position has been adjusted after step ST 9  of adjusting the transfer position of the focus ring FR. Accordingly, the accuracy of transfer of the focus ring FR can further be improved. 
     Although various exemplary embodiments have been described above, various omissions, substitutions, and changes may be made without being limited to the above-described exemplary embodiments. In addition, other embodiments can be formed by combining elements in different embodiments. 
     For example, the number of first sensors and second sensors mounted on the measuring instrument is not limited to the above-described embodiments. The number of first sensors and second sensors may be any number of three or more. Further, in a case where it is desired to acquire only the amount of deviation in the uniaxial direction, the number of sensors may be two. 
     Further, although an example in which one of the process modules is used as a storage location for the focus ring FR has been described, the present disclosure is not limited thereto. For example, one of the containers (FOUP) for accommodating the workpiece W may be used as a storage location for the focus ring FR. 
     In addition, although the aspect in which the position adjustment of the focus ring is performed in the process module has been illustrated, the method of position adjustment is not limited thereto. For example, a module for position adjustment may be provided at a location adjacent to the transfer module. The module for position adjustment has a placing table for placing the focus ring and the measuring instrument. In one example, after the focus ring is transferred onto the placing table of the module, the measuring instrument is transferred into the inner region of the focus ring placed on the placing table. The transfer position data of the measuring instrument is adjusted in advance such that the measuring instrument can be transferred to the center of the electrostatic chuck of the process module. Subsequently, the mutual positional relationship between the focus ring and the measuring instrument is acquired, and the measuring instrument and the focus ring are transferred out from the module for position adjustment. Subsequently, based on the acquired positional relationship, the position where the focus ring is transferred into the target process module is adjusted, and the focus ring is transferred to the process module. In addition, when the focus ring is transferred out from the module for position adjustment, the focus ring receiving position by the transfer arm may be adjusted based on the acquired positional relationship. In this case, since the central position of the focus ring on the transfer arm is adjusted, the focus ring may be transferred to the target process module in that state. In this manner, the transfer position of the focus ring in the process module may be adjusted by grasping the mutual positional relationship between the focus ring and the measuring instrument at a location other than the process module. Accordingly, the focus ring can be transferred to a desired position in the target process module. 
     In addition, an example in which the first amount of deviation which is an amount of deviation of the central axis of the measuring instrument from the central axis of the focus ring, and the second amount of deviation that is an amount of deviation of the central axis of the measuring instrument from the central axis of the electrostatic chuck are obtained, has been described, but the present disclosure is not limited thereto. The first amount of deviation may be an amount of deviation of the central position of the focus ring from the central axis of the measuring instrument  100 . Further, the second amount of deviation may be an amount of deviation of the central axis of the electrostatic chuck from the central axis of the measuring instrument. 
     From the description above, various embodiments of the present disclosure have been described in the present specification for purposes of description, and it is possible to understand that various modifications can be made without departing from the scope and spirit of the present disclosure. Therefore, the various embodiments disclosed in the present specification are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.