Measuring device

Abstract

To provide a technology to suppress damage of an operational amplifier caused by an ESD.SOLUTION: A measurement instrument according to an exemplary embodiment includes a base substrate, a sensor chip provided on the base substrate, and a circuit board provided on the base substrate. The sensor chip includes a sensor unit including a signal electrode having a front surface crossing a radial direction of the base substrate, a guard electrode arranged on a back side of the signal electrode, and a first ground electrode arranged on a back side of the guard electrode. The sensor chip includes a second ground electrode extending along a lower surface of the sensor unit. Only an insulating material is filled between the second ground electrode and the sensor unit.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] An exemplary embodiment of the present disclosure relates to a meter. [Background technology]

[0002] Patent Document 1 describes a measuring device having a sensor chip for measuring capacitance. The sensor chip includes a first electrode, a second electrode, and a third electrode. The first electrode has a first portion. The second electrode has a second portion extending over the first portion and is insulated from the first electrode within the sensor chip. The third electrode has a front surface extending in a direction intersecting the first and second portions, is provided over the first portion and over the second portion, and is insulated from the first and second electrodes within the sensor chip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-3557 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides techniques for suppressing damage to operational amplifiers caused by electro-static discharge (ESD). [Means for solving the problem]

[0005] In one exemplary embodiment, a measuring device is provided. The measuring device includes a disk-shaped base substrate, a sensor chip provided on the base substrate, and a circuit board provided on the base substrate. The sensor chip includes a sensor unit including a signal electrode having a front surface intersecting the radial direction of the base substrate, a guard electrode spaced from the signal electrode and disposed on the rear side of the signal electrode and extending along the signal electrode, and a first ground electrode disposed on the rear side of the guard electrode. The circuit board includes a high-frequency oscillator provided to provide high-frequency signals to the signal electrode and the guard electrode, respectively, and a C / V conversion circuit that generates a voltage signal according to the electrostatic capacitance formed by the signal electrode. The C / V conversion circuit has an amplifier circuit including an operational amplifier. The high-frequency oscillator is connected to the non-inverting input terminal of the operational amplifier so as to input the high-frequency signal provided to the signal electrode to the non-inverting input terminal, and is connected to the inverting input terminal of the operational amplifier so as to input the high-frequency signal provided to the signal electrode to the inverting input terminal. The sensor chip includes a second ground electrode extending along the lower surface of the sensor unit. The signal electrode, guard electrode, and first ground electrode of the sensor unit all extend to the bottom end of the sensor unit. The space between the second ground electrode and the sensor unit is filled with only an insulating material. Effect of the Invention

[0006] A measuring instrument according to an exemplary embodiment can suppress damage to an operational amplifier caused by ESD. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 illustrates a processing system. [Diagram 2] FIG. 2 is a perspective view illustrating an aligner. [Diagram 3] FIG. 1 illustrates an example of a plasma processing apparatus. [Figure 4] FIG. 2 is a plan view showing an example measuring device as viewed from the top side. [Diagram 5] FIG. 2 is a plan view showing an example measuring device as viewed from the bottom side. [Figure 6]FIG. 2 is a perspective view showing an example of a first sensor. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] FIG. 8 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 8 is a cross-sectional view taken along line XX in FIG. [Figure 11] FIG. 6 is an enlarged view of the second sensor of FIG. 5. [Figure 12] FIG. 2 is a diagram illustrating an example of the configuration of a circuit board of the measuring device. [Figure 13] FIG. 2 is a diagram illustrating an example of detailed configuration of a circuit board of the measuring device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Various exemplary embodiments are described below.

[0009] In one exemplary embodiment, a measuring device is provided. The measuring device includes a disk-shaped base substrate, a sensor chip provided on the base substrate, and a circuit board provided on the base substrate. The sensor chip includes a sensor unit including a signal electrode having a front surface intersecting the radial direction of the base substrate, a guard electrode spaced from the signal electrode and disposed on the rear side of the signal electrode and extending along the signal electrode, and a first ground electrode disposed on the rear side of the guard electrode. The circuit board includes a high-frequency oscillator provided to provide high-frequency signals to the signal electrode and the guard electrode, respectively, and a C / V conversion circuit that generates a voltage signal according to the electrostatic capacitance formed by the signal electrode. The C / V conversion circuit has an amplifier circuit including an operational amplifier. The high-frequency oscillator is connected to the non-inverting input terminal of the operational amplifier so as to input the high-frequency signal provided to the signal electrode to the non-inverting input terminal, and is connected to the inverting input terminal of the operational amplifier so as to input the high-frequency signal provided to the signal electrode to the inverting input terminal. The sensor chip includes a second ground electrode extending along the lower surface of the sensor unit. The signal electrode, guard electrode, and first ground electrode of the sensor unit all extend to the bottom end of the sensor unit. The space between the second ground electrode and the sensor unit is filled with only an insulating material.

[0010] In the measuring device of the above embodiment, the signal electrode is shielded backward by the guard electrode and the first ground electrode, and shielded downward by the second ground electrode. Therefore, this sensor chip makes it possible to measure capacitance with high directivity in a specific direction, i.e., in the direction in which the front surface of the signal electrode faces. In addition, ESD to the guard electrode is suppressed, so that ESD is prevented from passing through the guard electrode and destroying the operational amplifier.

[0011] In one exemplary embodiment, the guard electrode constituting the sensor portion may not include a portion extending along the lower surface of the sensor portion.

[0012] In one exemplary embodiment, in a plan view, the front surface of the signal electrode, the front surface of the guard electrode, and the front surface of the first ground electrode may all be curved surfaces parallel to the curved surface formed by the outer periphery of the base substrate.

[0013] In one exemplary embodiment, the sensor chip may include a first flexible substrate extending along a lower surface of the sensor portion and including a second ground electrode.

[0014] In one exemplary embodiment, the sensor chip may include a second flexible substrate extending along the top surface of the sensor portion.

[0015] In one exemplary embodiment, the front surface of the signal electrode may be covered with an insulating material having insulating properties.

[0016] In one exemplary embodiment, the insulating material covering the front surface of the signal electrode may be formed from borosilicate glass or quartz.

[0017] Various embodiments will be described in detail below with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0018] A measuring instrument according to an exemplary embodiment can be transported by a processing system 1 having a function as a transport system S1. First, a processing system having a processing device for processing a workpiece and a transport device for transporting the workpiece to the processing device will be described. FIG. 1 is a diagram illustrating a processing system. The processing system 1 includes stages 2a-2d, containers 4a-4d, a loader module LM, an aligner AN, load lock modules LL1 and LL2, process modules PM1-PM6, a transfer module TF, and a controller MC. Note that the numbers of stages 2a-2d, containers 4a-4d, load lock modules LL1 and LL2, and process modules PM1-PM6 are not limited and may be any number equal to or greater than one.

[0019] The stages 2a to 2d are arranged along one edge of the loader module LM. The containers 4a to 4d are mounted on the stages 2a to 2d, respectively. Each of the containers 4a to 4d is, for example, a container called a FOUP (Front Opening Unified Pod). Each of the containers 4a to 4d can be configured to accommodate a workpiece W. The workpiece W has a substantially disk shape, such as a wafer.

[0020] The loader module LM has a chamber wall that defines a transfer space therein under atmospheric pressure. A transfer device TU1 is provided in this transfer space. The transfer device TU1 is, for example, an articulated robot, and is controlled by a control unit MC. The transfer device TU1 is configured to transfer the workpiece W between the containers 4a-4d and the aligner AN, between the aligner AN and the load lock modules LL1-LL2, and between the load lock modules LL1-LL2 and the containers 4a-4d.

[0021] The aligner AN is connected to the loader module LM. The aligner AN is configured to adjust (calibrate) the position of the workpiece W. FIG. 2 is a perspective view illustrating the aligner. The aligner AN has a support table 6T, a drive unit 6D, and a sensor 6S. The support table 6T is a table that can rotate about an axis extending in the vertical direction, and is configured to support the workpiece W thereon. The support table 6T is rotated by the drive unit 6D. The drive unit 6D is controlled by the control unit MC. When the support table 6T rotates by the power from the drive unit 6D, the workpiece W placed on the support table 6T also rotates.

[0022] The sensor 6S is an optical sensor, and detects the edge of the workpiece W while the workpiece W is being rotated. From the edge detection result, the sensor 6S detects the amount of deviation of the angular position of the notch WN (or another marker) of the workpiece W relative to the reference angular position, and the amount of deviation of the center position of the workpiece W relative to the reference position. The sensor 6S outputs the amount of deviation of the angular position of the notch WN and the amount of deviation of the center position of the workpiece W to the control unit MC. Based on the amount of deviation of the angular position of the notch WN, the control unit MC calculates the amount of rotation of the support table 6T for correcting the angular position of the notch WN to the reference angular position. The control unit MC controls the drive unit 6D to rotate the support table 6T by this amount of rotation. This allows the angular position of the notch WN to be corrected to the reference angular position. The control unit MC also controls the position of the end effector of the transport device TU1 when receiving the workpiece W from the aligner AN, based on the amount of deviation of the center position of the workpiece W. As a result, the center position of the workpiece W coincides with a predetermined position on the end effector of the transport device TU1.

[0023] 1, each of the load lock modules LL1 and LL2 is provided between the loader module LM and the transfer module TF. Each of the load lock modules LL1 and LL2 provides a preliminary reduced pressure chamber.

[0024] The transfer module TF is airtightly connected to the load lock modules LL1 and LL2 via gate valves. The transfer module TF provides a decompression chamber capable of reducing pressure. A transfer device TU2 is provided in this decompression chamber. The transfer device TU2 is, for example, an articulated robot having a transfer arm TUa, and is controlled by a control unit MC. The transfer device TU2 is configured to transfer a workpiece W between the load lock modules LL1-LL2 and the process modules PM1-PM6, and between any two of the process modules PM1-PM6.

[0025] The process modules PM1 to PM6 are airtightly connected to the transfer module TF via gate valves. Each of the process modules PM1 to PM6 is a processing device configured to perform a dedicated process such as a plasma process on the workpiece W.

[0026] A series of operations when the workpiece W is processed in the processing system 1 is exemplified as follows. The transfer device TU1 of the loader module LM takes out the workpiece W from one of the containers 4a to 4d and transfers the workpiece W to the aligner AN. Then, the transfer device TU1 takes out the workpiece W whose position has been adjusted from the aligner AN and transfers the workpiece W to one of the load lock modules LL1 and LL2. Then, one of the load lock modules reduces the pressure in the preliminary decompression chamber to a predetermined pressure. Then, the transfer device TU2 of the transfer module TF takes out the workpiece W from one of the load lock modules and transfers the workpiece W to one of the process modules PM1 to PM6. Then, one or more of the process modules PM1 to PM6 process the workpiece W. Then, the transfer device TU2 transfers the processed workpiece W from the process module to one of the load lock modules LL1 and LL2. Next, the transfer device TU1 transfers the workpiece W from one of the load lock modules to any one of the containers 4a to 4d.

[0027] As described above, the processing system 1 includes a control unit MC. The control unit MC may be a computer including a processor, a storage device such as a memory, a display device, an input / output device, a communication device, etc. The series of operations of the processing system 1 described above are realized by the control unit MC controlling each part of the processing system 1 according to a program stored in the storage device.

[0028] Fig. 3 is a diagram showing an example of a plasma processing apparatus that can be employed as any one of the process modules PM1 to PM6. The plasma processing apparatus 10 shown in Fig. 3 is a capacitively coupled plasma etching apparatus. The plasma processing apparatus 10 includes a chamber body 12 having a substantially cylindrical shape. The chamber body 12 is made of, for example, aluminum, and an inner wall surface thereof may be anodized. The chamber body 12 is safety grounded.

[0029] A substantially cylindrical support 14 is provided on the bottom of the chamber body 12. The support 14 is made of, for example, an insulating material. The support 14 is provided within the chamber body 12 and extends upward from the bottom of the chamber body 12. A stage ST is provided within a chamber S provided by the chamber body 12. The stage ST is supported by the support 14.

[0030] The stage ST has a lower electrode LE and an electrostatic chuck ESC. The lower electrode LE includes a first plate 18a and a second plate 18b. The first plate 18a and the second plate 18b are made of a metal such as aluminum and have a substantially disk shape. The second plate 18b is provided on the first plate 18a and is electrically connected to the first plate 18a.

[0031] An electrostatic chuck ESC is provided on the second plate 18b. The electrostatic chuck ESC has a structure in which an electrode, which is a conductive film, is disposed between a pair of insulating layers or insulating sheets, and has a substantially disk shape. A DC power supply 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 electrostatic force such as Coulomb force generated by a DC voltage from the DC power supply 22. This allows the electrostatic chuck ESC to hold the workpiece W.

[0032] An edge ring ER is provided on the periphery of the second plate 18b. The edge ring ER is provided so as to surround the edge of the workpiece W and the electrostatic chuck ESC. The edge ring ER has a first portion P1 and a second portion P2 (see FIG. 7). The first portion P1 and the second portion P2 have an annular plate shape. The second portion P2 is a portion that is outer than the first portion P1. The second portion P2 has a thickness in the height direction that is greater than that of the first portion P1. The inner edge P2i of the second portion P2 has a diameter that is greater than the diameter of the inner edge P1i of the first portion P1. The workpiece W is placed on the electrostatic chuck ESC so that its edge region is located on the first portion P1 of the edge ring ER. The edge ring ER can be formed of any of various materials such as silicon, silicon carbide, and silicon oxide.

[0033] A coolant flow passage 24 is provided inside the second plate 18b. The coolant flow passage 24 constitutes a temperature adjustment mechanism. A coolant is supplied to the coolant flow passage 24 from a chiller unit provided outside the chamber body 12 via a pipe 26a. The coolant supplied to the coolant flow passage 24 is returned to the chiller unit via a pipe 26b. In this manner, the coolant is circulated between the coolant flow passage 24 and the chiller unit. By controlling the temperature of this coolant, the temperature of the workpiece W supported by the electrostatic chuck ESC is controlled.

[0034] A plurality of (for example, three) through holes 25 are formed in the stage ST and pass through the stage ST. The plurality of through holes 25 are formed inside the electrostatic chuck ESC in a plan view. A lift pin 25a is inserted into each of the through holes 25. Note that FIG. 3 illustrates one through hole 25 into which one lift pin 25a is inserted. The lift pin 25a is provided so as to be movable up and down within the through hole 25. As the lift pin 25a rises, the workpiece W supported on the electrostatic chuck ESC rises.

[0035] A plurality of (e.g., three) through holes 27 penetrating the stage ST (lower electrode LE) are formed in the stage ST at positions outside the electrostatic chuck ESC in a plan view. A lift pin 27a is inserted into each of the through holes 27. Note that FIG. 3 illustrates one through hole 27 into which one lift pin 27a is inserted. The lift pin 27a is provided so as to be movable up and down within the through hole 27. As the lift pin 27a rises, the edge ring ER supported on the second plate 18b rises.

[0036] The plasma processing apparatus 10 is also provided with a gas supply line 28. The gas supply line 28 supplies a heat transfer gas, for example, He gas, from a heat transfer gas supply mechanism to between the upper surface of the electrostatic chuck ESC and the back surface of the workpiece W.

[0037] The plasma processing apparatus 10 also includes an upper electrode 30. The upper electrode 30 is disposed above the stage ST and faces the stage ST. The upper electrode 30 is supported on the upper part of the chamber body 12 via an insulating shielding member 32. The upper electrode 30 may include a top plate 34 and a support 36. The top plate 34 faces the chamber S, and is provided with a plurality of gas ejection holes 34a. The top plate 34 may be made of silicon or quartz. Alternatively, the top plate 34 may be formed by forming a plasma-resistant film such as yttrium oxide on the surface of an aluminum base material.

[0038] The support 36 detachably supports the top plate 34 and may be made of a conductive material such as aluminum. The support 36 may have a water-cooled structure. A gas diffusion chamber 36a is provided inside the support 36. A plurality of gas flow holes 36b that communicate with the gas discharge holes 34a extend downward from the gas diffusion chamber 36a. The support 36 is also formed with a gas inlet 36c that introduces a process gas into the gas diffusion chamber 36a, and a gas supply pipe 38 is connected to the gas inlet 36c.

[0039] 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 includes a plurality of gas sources for a plurality of types of gas. The valve group 42 includes a plurality of valves, and the flow rate controller group 44 includes a plurality of flow rate controllers such as mass flow controllers. The plurality of gas sources in the gas source group 40 are connected to the gas supply pipe 38 via the corresponding valves in the valve group 42 and the corresponding flow rate controllers in the flow rate controller group 44.

[0040] Furthermore, in the plasma processing apparatus 10, a deposit shield 46 is detachably provided along the inner wall of the chamber body 12. The deposit shield 46 is also provided on the outer periphery of the support part 14. The deposit shield 46 prevents etching by-products (deposits) from adhering to the chamber body 12, and may be formed by coating an aluminum material with ceramics such as yttrium oxide.

[0041] An exhaust plate 48 is provided on the bottom side of the chamber body 12 and between the support 14 and the side wall of the chamber body 12. The exhaust plate 48 can be made, for example, by coating ceramics such as yttrium oxide on an aluminum material. A plurality of holes are formed in the exhaust plate 48, penetrating in the plate thickness direction. An exhaust port 12e is provided below the exhaust plate 48 and in the chamber body 12. An exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52. The exhaust device 50 has a pressure adjustment valve and a vacuum pump such as a turbo molecular pump, and can reduce the pressure of the space in the chamber body 12 to a desired vacuum level. In addition, a load / unload port 12g for the workpiece W is provided on the side wall of the chamber body 12, and the load / unload port 12g can be opened and closed by a gate valve 54.

[0042] The plasma processing apparatus 10 further includes a first high frequency power supply 62 and a second high frequency power supply 64. The first high frequency power supply 62 is a power supply that generates a first high frequency for generating plasma, and generates a high frequency having a frequency of, for example, 27 to 100 MHz. The first high frequency power supply 62 is connected to the upper electrode 30 via a matching device 66. The matching device 66 has a circuit for matching the output impedance of the first high frequency power supply 62 with the input impedance on the load side (upper electrode 30 side). The first high frequency power supply 62 may be connected to the lower electrode LE via the matching device 66.

[0043] The second high frequency power supply 64 is a power supply that generates a second high frequency for attracting ions into the workpiece W, and generates a high frequency with a frequency within a range of, for example, 400 kHz to 13.56 MHz. The second high frequency power supply 64 is connected to the lower electrode LE via a matching device 68. The matching device 68 has a circuit for matching the output impedance of the second high frequency power supply 64 with the input impedance on the load side (the lower electrode LE side).

[0044] In this plasma processing apparatus 10, gas is supplied to the chamber S from one or more selected gas sources among a plurality of gas sources. The pressure in the chamber S is set to a predetermined pressure by the exhaust device 50. The gas in the chamber S is excited by a first high frequency wave from a first high frequency power supply 62. This generates plasma. The workpiece W is then processed by the generated activated species. If necessary, ions may be attracted to the workpiece W by a bias based on the second high frequency wave from a second high frequency power supply 64.

[0045] The measuring instrument will be described below. FIG. 4 is a plan view showing the measuring instrument as viewed from the top side. FIG. 5 is a plan view showing the measuring instrument as viewed from the bottom side. The measuring instrument 100 shown in FIGS. 4 and 5 includes a base substrate 102. The base substrate 102 is made of, for example, silicon, and has a shape similar to that of the workpiece W, that is, a substantially disk shape. The diameter of the base substrate 102 is the same as that of the workpiece W, and is, for example, 300 mm. The shape and dimensions of the measuring instrument 100 are determined by the shape and dimensions of the base substrate 102. Therefore, the measuring instrument 100 has a shape similar to that of the workpiece W, and has dimensions similar to those of the workpiece W. In addition, a notch 102N (or another marker) is formed on the edge of the base substrate 102.

[0046] A plurality of first sensors 104A to 104C for measuring capacitance are provided on the base substrate 102. The plurality of first sensors 104A to 104C are arranged at equal intervals along the edge of the base substrate 102, for example, around the entire circumference of the edge. Specifically, each of the plurality of first sensors 104A to 104C is provided along the edge on the upper surface side of the base substrate 102. The front end surface of each of the plurality of first sensors 104A to 104C is aligned along the side surface of the base substrate 102.

[0047] In addition, the base substrate 102 is provided with a plurality of second sensors 105A to 105C for measuring capacitance. The second sensors 105A to 105C are arranged at equal intervals along the edge of the base substrate 102, for example, around the entire circumference of the edge. Specifically, each of the second sensors 105A to 105C is provided along the edge on the bottom side of the base substrate. The signal electrodes 161 of each of the second sensors 105A to 105C are arranged along the bottom surface of the base substrate 102. The second sensors 105A to 105C and the first sensors 104A to 104C are arranged alternately at 60° intervals in the circumferential direction.

[0048] 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 multiple first sensors 104A to 104C, wiring groups 108A to 108C are provided for electrically connecting the sensors to each other. Furthermore, between the circuit board 106 and the multiple second sensors 105A to 105C, wiring groups 208A to 208C are provided for electrically connecting the sensors to each other. The circuit board 106, the wiring groups 108A to 108C, and the wiring groups 208A to 208C are covered by a cover 103.

[0049] The first sensor will be described in detail below. Fig. 6 is a perspective view showing an example of a sensor. Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 6. Fig. 8 is a cross-sectional view of the first sensor taken along line VIII-VIII in Fig. 7. Fig. 9 is a cross-sectional view of the first sensor taken along line IX-IX in Fig. 7. Fig. 10 is a cross-sectional view of the first sensor taken along line XX in Fig. 7.

[0050] The first sensor (sensor chip) 104 is a sensor used as a plurality of first sensors 104A-104C of the measuring device 100, and in one example, is configured as a chip-shaped component. In the following description, an XYZ orthogonal coordinate system will be referred to as appropriate. The X direction indicates the front direction of the first sensor 104, the Y direction is a direction perpendicular to the X direction and indicates the width direction of the first sensor 104, and the Z direction is a direction perpendicular to the X direction and the Y direction and indicates the upward direction of the first sensor 104. In FIG. 7, an edge ring ER is shown together with the first sensor 104.

[0051] The first sensor 104 includes a sensor body 140 (sensor section), a first flexible substrate 146, and a second flexible substrate 149. The sensor body 140 includes a signal electrode 141, a guard electrode 142, and a first ground electrode 143. In one example, the sensor body 140 may be a MEMS chip manufactured using MEMS (Micro Electro Mechanical Systems) technology. For example, the signal electrode 141, the guard electrode 142, and the first ground electrode 143 may be formed of a conductive material such as copper, silicon, or the like.

[0052] The signal electrode 141 has a front surface 141a that intersects with the radial direction of the base substrate 101. That is, in the measuring device 100, the front surface 141a of the signal electrode 141 faces the outside in the radial direction of the base substrate. In one example, the front surface 141a of the signal electrode 141 is curved so as to fit along the outer periphery of the measuring device 100. For example, the front surface 141a of the signal electrode 141 has a constant curvature at any position on the front surface 141a, and the curvature may be the reciprocal of the distance between the central axis AX100 of the measuring device 100 and the front surface 141a. A pad 151 electrically connected to the signal electrode 141 is provided at the upper end of the sensor body 140.

[0053] The guard electrode 142 is disposed behind the signal electrode 141 and spaced apart from the signal electrode 141. The guard electrode 142 extends along the signal electrode 141. The guard electrode 142 in the illustrated example has an inner surface 142a curved along the signal electrode 141 and a side edge 142b surrounding the edge of the signal electrode 141 in the width direction. The inner surface 142a of the guard electrode 142 is curved, similar to the signal electrode 141. For example, the inner surface 142a of the guard electrode 142 has a constant curvature at any position of the inner surface 142a, and the curvature may be the reciprocal of the distance between the central axis AX100 of the measuring device 100 and the inner surface 142a. The side edge 142b of the guard electrode 142 protrudes forward from both ends of the inner surface 142a in the width direction. The side edge 142b is formed along and spaced from the edge in the width direction of the signal electrode 141. A pad 152 electrically connected to the guard electrode 142 is provided on the upper end of the sensor body 140.

[0054] First ground electrode 143 is disposed behind guard electrode 142 and spaced apart from guard electrode 142. In addition, front surface 143a of first ground electrode 143 extends along guard electrode 142. That is, front surface 143a of first ground electrode 143 is a curved surface parallel to guard electrode 142. For example, front surface 143a of first ground electrode 143 has a constant curvature at any position on the front surface, and the curvature may be the reciprocal of the distance between center axis AX100 of measuring device 100 and front surface 143a. In addition, first ground electrode 143 includes side edge portion 143b surrounding side edge portion 142b of guard electrode 142. Side edge portion 143b of first ground electrode 143 protrudes forward from both ends in the width direction of front surface 143a. The side edge 143b is formed along and spaced apart from the side edge 142b of the guard electrode 142. A pad 153 electrically connected to the first ground electrode 143 is provided on the upper end of the sensor body 140.

[0055] Moreover, an insulating material 145 having electrical insulation properties is disposed between the signal electrode 141, the guard electrode 142, and the first ground electrode 143, which are spaced apart from each other. As illustrated, the insulating material 145 includes a front portion 145a, a first intermediate portion 145b, and a second intermediate portion 145c. The front portion 145a constitutes the front surface of the sensor body 140. That is, the front portion 145a covers the front surface 141a of the signal electrode 141, the front portion of the side edge portion 142b of the guard electrode 142, and the front portion of the side edge portion 143b of the first ground electrode 143. The first intermediate portion 145b is disposed between the signal electrode 141 and the guard electrode 142. In the illustrated example, the first intermediate portion 145b is also disposed between the pad 151 connected to the signal electrode 141 and the pad 152 connected to the guard electrode 142. The second intermediate portion 145c is disposed between the guard electrode 142 and the first ground electrode 143. In the illustrated example, the second intermediate portion 145c is also disposed between a pad 152 connected to the guard electrode 142 and a pad 153 connected to the first ground electrode 143. The insulating material 145 may be formed of, for example, borosilicate glass, quartz, or the like.

[0056] Thus, in a plan view, the front surface 141a of the signal electrode 141, the front surface (inner surface portion 142a) of the guard electrode 142, and the front surface 143a of the first ground electrode 143 are all curved surfaces parallel to the curved surface formed by the outer periphery of the base substrate 101. Moreover, the signal electrode 141, the guard electrode 142, and the first ground electrode 143 all extend from the upper end to the lower end of the sensor body 140. The signal electrode 141, the guard electrode 142, and the first ground electrode 143 are arranged spaced apart from one another by the insulating material 145 that extends from the upper end to the lower end of the sensor body 140.

[0057] The first flexible substrate 146 extends along the lower surface of the columnar sensor body 140. For example, the first flexible substrate 146 is fixed to the lower surface of the sensor body 140 by an adhesive member such as an adhesive or adhesive sheet having electrical insulation properties. This electrically insulates the lower surface of the sensor body 140 from the outside. The first flexible substrate 146 includes a region having a planar shape similar to that of the sensor body 140 and a terminal region 146a protruding rearward from the center of the rear end of the region. The first flexible substrate 146 of an example includes a substrate body 147 and a second ground electrode 148. The substrate body 147 is formed of, for example, polyimide having electrical insulation properties. The second ground electrode 148 is formed in a plate shape one size smaller than the substrate body 147 and is covered by the substrate body 147. That is, the upper surface, lower surface, and side surface of the second ground electrode 148 are all covered by the substrate body 147. The second ground electrode 148 may be formed of a conductive metal such as copper.

[0058] The second ground electrode 148 extends along the lower surface of the sensor body 140. Therefore, the space between the second ground electrode 148 and the sensor body 140 is filled only with the electrically insulating substrate body 147. In the terminal region 146a, an opening 147a is formed in the substrate body 147, and a part of the second ground electrode 148 is exposed as a pad 148a. In addition, in the terminal region 146a, a pad 146c and a pad 146d corresponding to the signal electrode 141 and the guard electrode 142 are formed, respectively.

[0059] The second flexible substrate 149 has a planar shape similar to that of the sensor body 140, and extends along the upper surface of the sensor body 140. An example of the second flexible substrate 149 is formed of, for example, polyimide or the like having electrical insulation properties. The second flexible substrate 149 has openings 149a corresponding to the pads 151 to 153, respectively, so that the pads 151 to 153 are exposed to the outside. The second flexible substrate 149 may be fixed to the upper surface of the sensor body 140 by an adhesive member such as an adhesive or adhesive sheet having electrical insulation properties. In this case, the upper surface of the sensor body 140 is electrically insulated from the outside.

[0060] When first sensor 104 is used as a sensor of measuring device 100, signal electrode 141 is connected to wiring 181, guard electrode 142 is connected to wiring 182, and first ground electrode 143 is connected to wiring 183, as described below. In one example, the wiring connected to pad 151 of signal electrode 141 may be connected to wiring 181 via pad 146c. Furthermore, the wiring connected to pad 152 of guard electrode 142 may be connected to wiring 182 via pad 146d. Furthermore, the wiring connected to pad 153 of first ground electrode 143 may be connected to wiring 183 via pad 148a of second ground electrode 148.

[0061] The second sensor will be described in detail below. FIG. 11 is a partially enlarged view of FIG. 5, showing one second sensor. The second sensor 105 has a signal electrode 161. The edge of the signal electrode 161 is partially arc-shaped. That is, the signal electrode 161 has a planar shape defined by an inner edge 161a and an outer edge 161b, which are two arcs having different radii centered on the central axis AX100. The outer edge 161b on the radially outer side of the signal electrode 161 of each of the second sensors 105A to 105C extends on a common circle. Moreover, the inner edge 161a on the radially inner side of the signal electrode 161 of each of the second sensors 105A to 105C extends on another common circle. The curvature of a part of the edge of the signal electrode 161 coincides with the curvature of the edge of the electrostatic chuck ESC. In one exemplary embodiment, the curvature of the outer edge 161b forming the radially outer edge of the signal electrode 161 matches the curvature of the edge of the electrostatic chuck ESC. Note that the center of curvature of the outer edge 161b, i.e., the center of the circle on which the outer edge 161b extends, shares the central axis line AX100.

[0062] In one exemplary embodiment, the second sensor 105 further includes a guard electrode 162 surrounding the signal electrode 161. The guard electrode 162 has a frame shape and surrounds the signal electrode 161 over its entire periphery. The guard electrode 162 and the signal electrode 161 are spaced apart from each other such that an insulating region 164 is interposed between them. In one exemplary embodiment, the second sensor 105 further includes an electrode 163 surrounding 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 its entire periphery. The guard electrode 162 and the electrode 163 are spaced apart from each other such that an insulating region 165 is interposed between them.

[0063] The configuration of the circuit board 106 will be described below. FIG. 12 is a diagram illustrating the configuration of the circuit board of the measuring device. The circuit board 106 has a high-frequency oscillator 171, a plurality of C / V conversion circuits 172A-172C, a plurality of C / V conversion circuits 272A-272C, an A / D converter 173, a processor 174, a storage device 175, a communication device 176, and a power supply 177. In one example, the processor 174, the storage device 175, etc. configure a calculation device. The circuit board 106 also has a temperature sensor 179. The temperature sensor 179 outputs a signal according to the detected temperature to the processor 174. For example, the temperature sensor 179 can acquire the temperature of the environment around the measuring device 100.

[0064] Each of the first sensors 104A-104C is connected to the circuit board 106 via a corresponding one of the wiring groups 108A-108C. Also, each of the first sensors 104A-104C is connected to a corresponding one of the C / V conversion circuits 172A-172C via some wires included in the corresponding wiring group. Each of the second sensors 105A-105C is connected to the circuit board 106 via a corresponding one of the wiring groups 208A-208C. Also, each of the second sensors 105A-105C is connected to a corresponding one of the C / V conversion circuits 272A-272C via some wires included in the corresponding wiring group. Below, a description will be given of one first sensor 104 having the same configuration as each of first sensors 104A-104C, one wiring group 108 having the same configuration as each of wiring groups 108A-108C, and one C / V conversion circuit 172 having the same configuration as each of C / V conversion circuits 172A-172C. Also, a description will be given of one second sensor 105 having the same configuration as each of second sensors 105A-105C, one wiring group 208 having the same configuration as each of wiring groups 208A-208C, and a C / V conversion circuit 272 having the same configuration as each of C / V conversion circuits 272A-272C.

[0065] The wiring group 108 includes wirings 181 to 183. One end of the wiring 181 is electrically connected to the pad 151 connected to the signal electrode 141, and the other end of the wiring 181 is connected to the C / V conversion circuit 172. One end of the wiring 182 is electrically connected to the pad 152 connected to the guard electrode 142, and the other end of the wiring 182 is connected to the C / V conversion circuit 172. One end of the wiring 183 is electrically connected to the pad 153 electrically connected to the first ground electrode 143 and the second ground electrode 148. The wiring 183 is connected to a ground potential line GL connected to the ground GC of the circuit board 106. The wiring 183 may be connected to the ground potential line GL via a switch SWG.

[0066] The wiring group 208 includes wirings 281 to 283. One end of the wiring 281 is electrically connected to the signal electrode 161, and the other end of the wiring 281 is connected to the C / V conversion circuit 272. One end of the wiring 282 is electrically connected to the guard electrode 162, and the other end of the wiring 282 is connected to the C / V conversion circuit 272. One end of the wiring 283 is connected to the electrode 163. The wiring 283 is electrically connected to a ground potential line GL that is connected to the ground GC of the circuit board 106. The wiring 283 may be connected to the ground potential line GL via a switch SWG.

[0067] The high-frequency oscillator 171 is connected to a power source 177 such as a battery, and is configured to generate a high-frequency signal by receiving power from the power source 177. 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 is configured to provide the generated high-frequency signal to the wiring 181 and the wiring 182, and the wiring 281 and the wiring 282 through the plurality of output lines. Therefore, the high-frequency oscillator 171 is electrically connected to the signal electrode 141 and the guard electrode 142 of the first sensor 104, and the high-frequency signal from the high-frequency oscillator 171 is provided to the signal electrode 141 and the guard electrode 142. The high-frequency oscillator 171 is also electrically connected to the signal electrode 161 and the guard electrode 162 of the second sensor 105, and the high-frequency signal from the high-frequency oscillator 171 is provided to the signal electrode 161 and the guard electrode 162.

[0068] The input of the C / V conversion circuit 172 is connected to a wiring 181 connected to the pad 151 and a wiring 182 connected to the pad 152. That is, the input of the C / V conversion circuit 172 is connected to the guard electrode 142 and the signal electrode 141 of the first sensor 104. Also, the input of the C / V conversion circuit 272 is connected to the signal electrode 161 and the guard electrode 162, respectively. The C / V conversion circuit 172 and the C / V conversion circuit 272 are configured to generate voltage signals having amplitudes corresponding to the potential difference at their inputs and output the voltage signals. The C / V conversion circuit 172 generates a voltage signal corresponding to the capacitance formed by the corresponding first sensor 104. That is, the larger the capacitance of the signal electrode connected to the C / V conversion circuit 172, the larger the voltage of the voltage signal output by the C / V conversion circuit 172. Similarly, the larger the capacitance of the signal electrode connected to the C / V conversion circuit 272, the larger the voltage of the voltage signal output by the C / V conversion circuit 272.

[0069] The connection between the high-frequency oscillator 171 and the wiring 181, the wiring 182, and the C / V conversion circuit 172 will be described in more detail. FIG. 11 is a circuit diagram showing the connection between the high-frequency oscillator 171 and the wiring 181, the wiring 182, and the C / V conversion circuit 172. As shown in FIG. 13, a resistor 171a is connected between the high-frequency oscillator 171 and the wiring 182. A phase adjustment circuit 171d including a variable resistor 171b and a variable capacitor 171c is connected between the high-frequency oscillator 171 and the wiring 181. The C / V conversion circuit 172 has an amplifier circuit 172a including an operational amplifier and a resistor as a part thereof. In the amplifier circuit 172a, the wiring 181 is input to the inverting input of the operational amplifier, and the wiring 182 is input to the non-inverting input of the operational amplifier. The inverting input and the output of the operational amplifier are connected via a resistor. The amplifier circuit 172 a amplifies the potential difference between the signal from the signal electrode 141 and the signal from the guard electrode 142 that are input to the C / V conversion circuit 172 .

[0070] The high frequency oscillator 171 and the wiring 281, and the wiring 282 and the C / V conversion circuit 272 are connected in the same manner as the high frequency oscillator 171 and the wiring 181, and the wiring 182 and the C / V conversion circuit 172. That is, a resistor is connected between the high frequency oscillator 171 and the wiring 282. A variable impedance circuit including a variable resistor and a variable capacitor is connected between the high frequency oscillator 171 and the wiring 281. The C / V conversion circuit 272 has an amplifier circuit including an operational amplifier and a resistor as a part thereof. In the amplifier circuit, the wiring 281 is input to the inverting input of the operational amplifier, and the wiring 282 is input to the non-inverting input of the operational amplifier. Also, the inverting input and the output of the operational amplifier are connected via a resistor.

[0071] In the circuit configuration as described above, the resistance value of the variable resistor 171b of the phase adjustment circuit 171d is changed to change the amplitude of the signal from the signal electrode 141. Also, the capacitance value of the variable capacitor 171c of the phase adjustment circuit 171d is changed to change the phase of the signal from the signal electrode 141. In one exemplary embodiment, the resistance value of the variable resistor 171b and the capacitance value of the variable capacitor 171c are adjusted (controlled) by the processor 174 to adjust the admittance of the phase adjustment circuit 171d.

[0072] For example, as a so-called zero point adjustment, the resistance value of the variable resistor 171b and the capacitance of the variable capacitor 171c in the phase adjustment circuit 171d may be adjusted by the processor 174 so that the voltage signal output from the C / V conversion circuit 172 becomes zero. Also, the resistance value of the variable resistor 171b and the capacitance of the variable capacitor 171c in the phase adjustment circuit 171d may be adjusted so that the voltage signal output from the C / V conversion circuit 272 becomes zero.

[0073] 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. The A / D converter 173 is also connected to a processor 174. The A / D converter 173 is controlled by a control signal from the processor 174, and 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 into a digital value and outputs it to the processor 174 as a detection value.

[0074] A 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, for example, measurement data. Another storage device 178 is also connected to the processor 174. The storage device 178 is a storage device such as a non-volatile memory, and stores, for example, a program that is read and executed by the processor 174.

[0075] The communication device 176 is a communication device that complies with any wireless communication standard. For example, the communication device 176 complies with Bluetooth (registered trademark). The communication device 176 is configured to wirelessly transmit the measurement data stored in the storage device 175.

[0076] Processor 174 is configured to control each part of measuring device 100 by executing the above-mentioned program. For example, processor 174 controls the supply of high-frequency signals from high-frequency oscillator 171 to guard electrode 142, signal electrode 141, signal electrode 161, and guard electrode 162. Processor 174 also controls the power supply from power source 177 to storage device 175, the power supply from power source 177 to communication device 176, and the like. Furthermore, processor 174 executes the above-mentioned program to obtain the measurement value of first sensor 104 and the measurement value of second sensor 105 based on the detection value input from A / D converter 173. In one embodiment, when the detection value output from A / D converter 173 is X, processor 174 obtains the measurement value based on the detection value so that the measurement value is proportional to (a·X+b). Here, a and b are constants that change depending on the circuit state, etc. The processor 174 may have, for example, a predetermined arithmetic expression (function) that causes the measured value to be proportional to (a·X+b).

[0077] In the measuring device 100 described above, when the measuring device 100 is placed in an area surrounded by the edge ring ER, the multiple signal electrodes 141 and the guard electrode 142 face the inner edge of the edge ring ER. A measurement value generated based on the potential difference between the signal of the signal electrode 141 and the signal of the guard electrode 142 represents a capacitance reflecting the distance between each of the multiple signal electrodes 141 and the edge ring ER. The capacitance C is expressed as C=εS / d. ε can be considered to be the dielectric constant of the medium between the front surface 141a of the signal electrode 141 and the inner edge of the edge ring ER, S is the area of ​​the front surface 141a of the signal electrode 141, and d is the distance between the front surface 141a of the signal electrode 141 and the inner edge of the edge ring ER.

[0078] Therefore, the measuring device 100 can obtain measurement data reflecting the relative positional relationship between the measuring device 100 simulating the workpiece W and the edge ring ER. For example, the multiple measurement values ​​obtained by the measuring device 100 become smaller as the distance between the front surface 141a of the signal electrode 141 and the inner edge of the edge ring ER increases. Therefore, the amount of deviation of each signal electrode 141 in each radial direction of the edge ring ER can be obtained based on the measurement value representing the capacitance of each signal electrode 141 of the first sensors 104A-104C. Then, the error in the transport position of the measuring device 100 can be obtained from the amount of deviation of each signal electrode 141 of the first sensors 104A-104C in each radial direction.

[0079] Moreover, when the measuring device 100 is placed on the electrostatic chuck ESC, the signal electrodes 161 and the guard electrodes 162 face the electrostatic chuck ESC. As described above, the electrostatic capacitance C is expressed as C=εS / d. ε is the dielectric constant of the medium between the signal electrode 161 and the electrostatic chuck ESC, d is the distance between the signal electrode 161 and the electrostatic chuck ESC, and S can be regarded as the area where the signal electrode 161 and the electrostatic chuck ESC overlap each other in a plan view. The area S changes depending on the relative positional relationship between the measuring device 100 and the electrostatic chuck ESC. Therefore, the measuring device 100 can obtain measurement data that reflects the relative positional relationship between the measuring device 100 simulating the workpiece W and the electrostatic chuck ESC.

[0080] In one example, when the measuring device 100 is transported to a predetermined transport position, that is, a position on the electrostatic chuck ESC where the center of the electrostatic chuck ESC and the center of the measuring device 100 coincide with each other, the outer edge 161b of the signal electrode 161 may coincide with the edge of the electrostatic chuck ESC. In this case, for example, when the transport position of the measuring device 100 is shifted from the predetermined transport position, and the signal electrode 161 is shifted radially outward relative to the electrostatic chuck ESC, the area S becomes smaller. That is, the capacitance measured by the signal electrode 161 becomes smaller than the capacitance when the measuring device 100 is transported to the predetermined transport position. Therefore, the amount of deviation of each signal electrode 161 in each radial direction of the electrostatic chuck ESC can be obtained based on the measured value representing the capacitance of each signal electrode 161 of the second sensors 105A to 105C. Then, the error of the transport position of the measuring device 100 can be obtained from the amount of deviation of each signal electrode 161 of the second sensors 105A to 105C in each radial direction.

[0081] As described above, measuring device 100 includes disk-shaped base substrate 101, first sensor 104 provided on base substrate 101, and circuit board 106 provided on base substrate 101. First sensor 104 includes sensor body 140 including signal electrode 141, guard electrode 142, and first ground electrode 143. Signal electrode 141 has a front surface that intersects with the radial direction of base substrate 101. Guard electrode 142 is disposed behind signal electrode 141 at a distance from signal electrode 141 and extends along signal electrode 141. First ground electrode 143 is disposed behind guard electrode 142. Circuit board 106 includes high-frequency oscillator 171 provided to apply high-frequency signals to signal electrode 141 and guard electrode 142, respectively, and C / V conversion circuit 172 that generates a voltage signal according to the capacitance formed by signal electrode 141. The C / V conversion circuit 172 has an amplifier circuit 172a including an operational amplifier. The high-frequency oscillator 171 is connected to a non-inverting input terminal of the operational amplifier so as to input the high-frequency signal applied to the signal electrode 141 to the non-inverting input terminal. The high-frequency oscillator 171 is also connected to an inverting input terminal of the operational amplifier so as to input the high-frequency signal applied to the signal electrode 141 to the inverting input terminal. The first sensor 104 includes a second ground electrode 148 extending along the lower surface of the sensor body 140. The signal electrode 141, the guard electrode 142, and the first ground electrode 143 of the sensor body 140 all extend to the lower end of the sensor body 140. The space between the second ground electrode 148 and the sensor body 140 is filled with only an insulating material.

[0082] In measuring device 100 of the above embodiment, signal electrode 141 is shielded backward by guard electrode 142 and first ground electrode 143, and is shielded downward by second ground electrode 148. Therefore, first sensor 104 makes it possible to measure capacitance with high directivity in a specific direction, i.e., in the direction in which the front surface of signal electrode 141 faces.

[0083] For example, in order to improve the shielding effect for the lower part of the sensor body 140, it is conceivable to arrange a guard electrode also below the sensor body 140. However, if the guard electrode extends along the lower surface of the sensor body 140, the operational amplifier may be destroyed by ESD via the guard electrode. In one exemplary embodiment, a guard electrode is not arranged below the sensor body 140, and the guard electrode 142 constituting the sensor body 140 does not include a portion that extends along the lower surface of the sensor body 140. In other words, the space between the second ground electrode 148 and the sensor body 140 is filled only with an insulating material, so that the operational amplifier is prevented from being destroyed by ESD via the guard electrode.

[0084] In one exemplary embodiment, in a plan view, the front surface of the signal electrode 141, the front surface of the guard electrode 142, and the front surface of the first ground electrode 143 may all be curved surfaces parallel to the curved surface formed by the outer periphery of the base substrate 101. In this configuration, the signal electrode, the guard electrode, and the first ground electrode are each disposed parallel to the edge ring as well. Therefore, a measurement value that accurately indicates the distance between the edge ring can be obtained.

[0085] In one exemplary embodiment, the first sensor 104 may include a first flexible insulating substrate 146 that extends along the underside of the sensor body 140 and includes a second ground electrode 148. In this configuration, the second ground electrode 148 may be conveniently located below the sensor body 140.

[0086] In one exemplary embodiment, the first sensor 104 may include an insulating second flexible substrate 149 extending along the upper surface of the sensor body 140. In this configuration, the insulation on the upper surface of the sensor body 140 can be ensured.

[0087] In one exemplary embodiment, the front surface 141a of the signal electrode 141 is covered with an electrically insulating material 145. This configuration prevents ESD from passing through the signal electrode 141 and destroying the operational amplifier.

[0088] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims. [Explanation of symbols]

[0089] 100...measuring instrument, 102...base substrate, 104...first sensor (sensor chip), 140...sensor body (sensor portion), 141...signal electrode, 142...guard electrode, 143...first ground electrode, 148...second ground electrode, 171...high-frequency oscillator, 171d...phase adjustment circuit, 172...C / V conversion circuit, 172a...amplification circuit, ER...edge ring.

Claims

1. A sensor device comprising: a disk-shaped base substrate; a sensor chip provided on the base substrate; and a circuit board provided on the base substrate; The sensor chip includes: a sensor unit including: a signal electrode having a front surface intersecting a radial direction of the base substrate; a guard electrode spaced apart from the signal electrode and disposed rearward of the signal electrode and extending along the signal electrode; and a first ground electrode disposed rearward of the guard electrode; The circuit board includes: a high-frequency oscillator provided to apply high-frequency signals to the signal electrode and the guard electrode, respectively; a C / V conversion circuit that generates a voltage signal according to the capacitance formed by the signal electrode; the C / V conversion circuit has an amplifier circuit including an operational amplifier; the high frequency oscillator is connected to the non-inverting input terminal of the operational amplifier so as to input the high frequency signal applied to the guard electrode to the non-inverting input terminal thereof, and is connected to the inverting input terminal of the operational amplifier so as to input the high frequency signal applied to the signal electrode to the inverting input terminal thereof; the sensor chip includes a second ground electrode extending along a lower surface of the sensor portion, the signal electrode, the guard electrode, and the first ground electrode of the sensor unit all extend to a lower end of the sensor unit, A measuring instrument, wherein a space between the second ground electrode and the sensor portion is filled only with an insulating material.

2. The measuring device according to claim 1 , wherein the guard electrode constituting the sensor portion does not include a portion that extends along the lower surface of the sensor portion.

3. 3. The measuring instrument according to claim 1, wherein, in a plan view, a front surface of the signal electrode, a front surface of the guard electrode, and a front surface of the first ground electrode are all curved surfaces parallel to a curved surface formed by an outer periphery of the base substrate.

4. 4. The measuring instrument according to claim 1, wherein the sensor chip comprises a first flexible substrate having insulating properties, the first flexible substrate extending along a lower surface of the sensor portion and including the second ground electrode.

5. 5. The measuring instrument according to claim 1, wherein the sensor chip comprises a second flexible substrate having insulating properties and extending along an upper surface of the sensor portion.

6. 6. The measuring device according to claim 1, wherein the front surface of the signal electrode is covered with an insulating material having insulating properties.

7. The meter of claim 6 , wherein the insulating material covering the front surface of the signal electrode is formed from borosilicate glass or quartz.

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