JP2021142628A - Thickness measurement device for polishing pad - Google Patents

Abstract

To provide a thickness measurement device which measures thickness of a polishing pad by wear thereof, thereby enabling wear of the polishing pad to be confirmed by a direct method.SOLUTION: A thickness measurement device 10 is provided which measures thickness of a polishing pad 13 for use in polishing of a polishing object such as a wafer W. The thickness measurement device 10 comprises: a polishing pad holding plate 31 that is mounted with a polishing pad 32 and rotates together with the pad, and can move in vertical direction; a sensor 14 for measuring polishing pad thickness that is pressed at a nearly right angle against the polishing pad holding plate 31 through the polishing pad 32 and outputs an electric signal corresponding to a distance up to the polishing pad holding plate 31; and a control unit 15 having measuring means 36 that measures a thickness of the polishing pad 32 on the basis of the electric signal from the sensor 14 for measuring the polishing pad thickness.SELECTED DRAWING: Figure 1

Description

The present invention relates to a polishing pad thickness measuring device, and more particularly to a polishing pad thickness measuring device for use in determining the life of the polishing pad.

Conventionally, a polishing device that polishes a polishing pad and an object to be polished while applying a load between the polishing pad and the object to be polished has been known (see, for example, Patent Document 1).

Examples of such a polishing device include a polishing device that performs chemical mechanical polishing (hereinafter referred to as “CMP”) used for flattening the surface of a semiconductor device wafer or the like. can. CMP uses a polishing agent called a slurry in the process of removing surface irregularities of a wafer by using a chemical action (polishing agent, dissolution with a solution) in combination with physical polishing, and is an appropriate polishing pad. Then, the surface of the wafer is pressurized and moved relative to each other to promote polishing so that uniform polishing can be performed on the surface of the wafer.

In such a polishing device, the polished surface of the polishing pad is clogged and deteriorated according to the polishing time. Therefore, dressing is performed regularly and maintenance is performed so that good processing can be continued.

This dressing is performed by bringing the polishing surface of the polishing pad into contact with the dressing surface of the dressing and moving the polishing pad and the dressing relative to each other. As the dressing, for example, a tool in which abrasive particles such as diamond particles are distributed over the entire annular or circular dressing surface is used. The relative movement is performed, for example, by rotating both the polishing pad and the dressing.

The thickness of the polishing pad becomes thin due to wear due to polishing of an object to be polished such as a wafer and wear due to dressing. Eventually, the desired polishing characteristics cannot be obtained, and the life of the product expires. Therefore, it is necessary to replace the polishing pad with a new polishing pad. Therefore, conventionally, the life of the polishing pad is determined based on the cumulative time of polishing by the polishing pad, the cumulative time of dressing, the number of objects to be polished, the number of times of dressing, etc., and it is determined that the life of the polishing pad has expired (use limit). Occasionally, I was replacing the polishing pad with a new one.

JP-A-2015-134383

However, the life of the polishing pad differs depending on the characteristics of each polishing pad (initial thickness, elastic modulus, hardness, etc.). In a method of ignoring the characteristics of each polishing pad and determining the life of the polishing pad based on the cumulative time of polishing by the polishing pad, the cumulative time of dressing, the number of objects to be polished, the number of times of dressing, etc. There is a possibility that polishing itself may occur with a polishing pad in an overwear state. Therefore, in order to prevent damage to the wafer, there is a need for a more direct method for confirming accurate wear of the polishing pad.

Therefore, in order to provide a polishing pad thickness measuring device that measures the wear of the polishing pad by the thickness and enables the wear of the polishing pad to be confirmed by a direct method, a technical problem to be solved arises. , The present invention aims to solve this problem.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is a polishing pad thickness measuring device for measuring the thickness of a polishing pad used for polishing an object to be polished. The polishing pad is attached and rotates integrally, and the polishing pad holding plate that can move horizontally in the vertical direction and the polishing pad holding plate are pressed at a substantially right angle via the polishing pad to reach the polishing pad holding plate. A polishing pad thickness measuring sensor that outputs an electric signal according to the distance of the polishing pad, and a control unit having a measuring means for measuring the thickness of the polishing pad based on the electric signal from the polishing pad thickness measuring sensor. Provided is a polishing pad thickness measuring device comprising the above.

According to this configuration, the polishing pad thickness measuring sensor is pressed substantially vertically against the polishing pad holding plate so as to sandwich the polishing pad attached to the polishing pad holding plate, and the polishing pad thickness measuring sensor to the polishing pad holding plate are reached. The distance is measured as the thickness of the polishing pad. In this way, when the distance between the polishing pad thickness measuring sensor and the polishing pad holding plate is measured as the thickness of the polishing pad, the thickness of the polishing pad at the time of measurement can be known directly and accurately.

In the invention according to claim 2, in the configuration according to claim 1, the polishing pad is made of a non-conductor material, the polishing pad holding plate is made of a conductor material, and the polishing pad thickness measuring sensor. Provides an apparatus for measuring the thickness of a polishing pad, which is an eddy current type displacement sensor.

According to this configuration, an eddy current displacement sensor is used to measure the distance to the polishing pad holding plate to which the polishing pad is attached from above the polishing pad. The eddy current type displacement sensor measures the distance based on the change in the magnetic field affected by the induced current generated in the polishing pad holding plate which is a conductor, but the polishing pad which is not a conductor does not change the sensor magnetic field. Therefore, when the eddy current type displacement sensor measures the distance from the top of the polishing pad to the polishing pad holding plate, the distance to the polishing pad holding plate can be accurately obtained as the thickness of the polishing pad.

According to a third aspect of the present invention, in the configuration according to the first or second aspect, the control unit includes a polishing pad for determining the life of the polishing pad from the measured thickness of the polishing pad. To provide a thickness measuring device for the above.

According to this configuration, when the life of the polishing pad is determined from the thickness of the polishing pad, the life at the time of measurement can be known directly and accurately.

According to the invention, the polishing pad holding plate is pressed against the polishing pad thickness measuring sensor so as to sandwich the polishing pad attached to the polishing pad holding plate, and the thickness of the polishing pad is measured. The distance from the sensor to the polishing pad holding plate can be obtained as the thickness of the polishing pad. Therefore, the thickness of the polishing pad at the time of measurement can be known directly and accurately. In addition, it is possible to directly determine whether or not the polishing pad is at the limit of use, and to quickly perform the necessary processing. As a result, damage to the wafer can be prevented.

It is a schematic configuration side view of the polishing apparatus equipped with the polishing pad thickness measuring apparatus shown as the Example which concerns on embodiment of this invention. It is the schematic block side view of the thickness measuring apparatus of the polishing pad of the same as above. It is the operation explanatory drawing of the thickness measuring apparatus of the polishing pad of the same as above. Same as above It is a time chart explaining the operation of the thickness measuring apparatus of a polishing pad.

The present invention achieves the object of providing a polishing pad thickness measuring device that measures the wear of a polishing pad by the thickness and enables the wear of the polishing pad to be confirmed by a direct method. A polishing pad thickness measuring device for measuring the thickness of the polishing pad used in the above, wherein the polishing pad is attached and rotates integrally, and the polishing pad holding plate that can move horizontally in the vertical direction and the polishing pad holding plate. To the polishing pad thickness measuring sensor that is pressed substantially at right angles through the polishing pad and outputs an electric signal according to the distance to the polishing pad holding plate, and the electric signal from the polishing pad thickness measuring sensor. Based on this, it was realized by providing a control unit having a measuring means for measuring the thickness of the polishing pad.

Hereinafter, an embodiment according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following examples, when referring to the shape and positional relationship of components, etc., they are substantially approximated to the shape, etc., except when explicitly stated or when it is considered that it is not apparent in principle. Or similar ones are included.

In addition, the drawings may be exaggerated by enlarging the characteristic parts in order to make the features easy to understand, and the dimensional ratios and the like of the components are not always the same as the actual ones.

Further, the expressions indicating the directions such as up and down and left and right are not absolute, and are appropriate when each part of the thickness measuring device of the polishing pad of the present invention is drawn, but the posture changes. If so, it should be changed and interpreted according to the change in posture.

FIG. 1 is a side view schematically showing the configuration of a polishing device 11 equipped with the polishing pad thickness measuring device 10 according to the present invention, and FIG. 2 is a side view schematically showing the polishing pad thickness measuring device 10. Is.

In FIG. 1, the polishing apparatus 11 is a CMP apparatus for flattening the surface of a semiconductor substrate in semiconductor manufacturing. The polishing apparatus 11 includes a rotary chuck table 12 capable of holding a wafer W which is an example of an object to be polished, a polishing head 13 which supports a polishing pad 32 and is arranged above the rotary chuck table 12, and a rotary chuck table 12. It is composed of a polishing pad thickness measuring sensor 14 arranged side by side in the polishing pad, and a control unit 15 and the like that control the overall operation of the polishing device 11 by a predetermined procedure.

The rotary chuck table 12 has a chuck surface 12a on the upper surface that sucks and holds the wafer W with a negative pressure. Further, the rotary chuck table 12 is connected to a table motor 16 arranged below the table shaft 12b via a table shaft 12b, and can rotate around the table shaft 12b by the driving force of the table motor 16. A polishing liquid supply nozzle (not shown) is installed above the rotary chuck table 12, and the polishing liquid (for example, slurry) is supplied onto the polishing surface of the wafer W by the polishing liquid supply nozzle. ..

The polishing head 13 is detachably attached to the lower end of the polishing head shaft 17. The polishing head shaft 17 is moved up and down integrally with the polishing head 13 in a state of being substantially horizontal to the head arm 19 by the actuator 18. By the vertical movement of the polishing head shaft 17, the entire polishing head 13 can be moved up and down in a substantially horizontal state with respect to the head arm 19 so that the polishing head 13 can be positioned at a predetermined position. The polishing head 13 is supported by the head arm 19 via a polishing head shaft 17 and an actuator 18. The polishing head shaft 17 extends through the head arm 19.

The actuator 18 can move the polishing head 13 and the polishing head shaft 17 relative to the head arm 19. The direction of the polishing head 13 moved by the actuator 18 is perpendicular to the chuck surface 12a (vertical direction).

The actuator 18 that moves the polishing head shaft 17 and the polishing head 13 in the vertical direction is fixed to the support base 20. The support base 20 is fixed to the upper surface of the head arm 19. The actuator 18 includes a bearing 21 that rotatably supports the polishing head shaft 17, a bridge 22 that holds the bearing 21, a ball screw mechanism 23 connected to the bridge 22, and a servo fixed on the support base 20. It is equipped with a motor 24.

The ball screw mechanism 23 includes a screw shaft 23a connected to the servomotor 24 and a nut 23b into which the screw shaft 23a is screwed. The nut 23b is held by the bridge 22.

The polishing head shaft 17 can move up and down integrally with the bearing 21 and the bridge 22. That is, when the servomotor 24 is driven, the bridge 22 moves up and down via the ball screw mechanism 23, whereby the polishing head shaft 17 and the polishing head 13 move up and down in a substantially horizontal state. The polishing head 13 is connected to the head arm 19 via a polishing head shaft 17, an actuator 18, and a support base 20.

The polishing head shaft 17 is supported by the ball spline bearing 25 so as to be movable in the axial direction thereof. A pulley 26 is fixed to the outer peripheral portion of the ball spline bearing 25.

A polishing head rotation motor 27 is fixed to the head arm 19, and the pulley 26 is connected to a pulley 28 attached to the polishing head rotation motor 27 via a belt 29. Therefore, when the polishing head rotation motor 27 is rotationally driven, the ball spline bearing 25 and the polishing head shaft 17 rotate integrally via the pulley 28, the belt 29, and the pulley 26, and the polishing head 13 is centered on the polishing head shaft 17. Rotate. The pulleys 26 and 28, the belt 29, and the ball spline bearing 25 are arranged in the head arm 19.

The head arm 19 is supported by a swivel shaft 30 supported by a frame (not shown).

The polishing head 13 can detachably hold a disk-shaped polishing pad 32 having a size substantially the same as the outer diameter of the polishing pad holding plate 31 via a disk-shaped polishing pad holding plate 31 on the lower surface thereof. It has become like. The polishing pad holding plate 31 is made of a conductor material (for example, stainless steel), and the polishing pad 32 is made of a non-conductor material (for example, polyester fiber).

The head arm 19 is configured to be swivelable about a swivel shaft 30. The polishing head 13 holding the polishing pad 32 on the lower surface can be switched between an upper position of the chuck surface 12a of the rotary chuck table 12 and an upper position of the polishing pad thickness measurement sensor 14 by turning the head arm 19. ..

The polishing pad thickness measuring sensor 14 is fixedly mounted on the sensor holding table 33 in a state of protruding upward from the sensor holding table 33. The sensor holding base 33 is connected to the sensor elevating cylinder 34 via a rod 34a, and can be reciprocated in the vertical direction by driving the sensor elevating cylinder 34. In this embodiment, an eddy current type displacement sensor is used as the polishing pad thickness measurement sensor 14. When a vortex current type sensor is used as the polishing pad thickness measuring sensor 14, when the polishing pad thickness measuring sensor 14 comes into contact with the polishing pad holding plate 31 with the polishing pad 32 sandwiched between them, the polishing pad holding plate 31 The measuring means 36 in the control unit 15 measures the distance to the polishing pad holding plate 31 from the magnitude of the eddy current generated between the two, and recognizes this distance as the thickness of the polishing pad 32. ..

The control unit 15 calculates the electric signal from the polishing pad thickness measuring sensor 14 to measure the thickness of the polishing pad 32, and the thickness of the polishing pad 32 measured by the measuring means 36 is an appropriate thickness. In addition to having a determination means 37 for determining whether or not the polishing device is possessed, that is, whether or not the polishing process is hindered even if the use is continued, overall operation control of the polishing device 11 and the thickness measuring device 10 is performed. It is what you do. The control unit 15 is composed of, for example, a microcomputer, and controls the polishing device 11 and the thickness measuring device 10 in a predetermined procedure while performing necessary arithmetic processing according to a program incorporated in the microcomputer. Therefore, the control unit 15 includes a polishing pad thickness measuring sensor 14, a table motor 16, an actuator 18, a servomotor 24, a polishing head rotation motor 27, a sensor elevating cylinder 34, an upper position detection sensor 35a, a lower position detection sensor 35b, and the like. Is connected.

Polishing of the wafer W is performed as follows. In a state where the polishing head 13 is raised to a predetermined reference height and separated from the rotary chuck table 12, the wafer W placed on the chuck surface 12a of the rotary chuck table 12 is vacuum-sucked onto the chuck surface 12a. Chuck. Next, the rotary chuck table 12 and the polishing head 13 are rotated relative to each other, and the polishing liquid (slurry) is supplied onto the wafer W surface from a polishing liquid supply nozzle (not shown). In this state, the polishing head 13 is lowered to a predetermined reference height, and the polishing pad 32 is pressed onto the surface to be processed of the wafer W. As a result, in the wafer W, the polished surface of the polishing pad 32 is in sliding contact with the surface of the wafer W in the presence of the polishing liquid, and the surface of the wafer W is polished.

In such a polishing device 11, the polished surface of the polishing pad 32 is deteriorated due to clogging progressing according to the polishing time. Therefore, dressing is performed regularly and maintenance is performed so that good processing can be continued. Further, the thickness of the polishing pad 32 becomes thin due to wear due to polishing of the wafer W and wear due to dressing. Eventually, the desired polishing characteristics cannot be obtained, and the life of the product expires. Therefore, it is necessary to replace the polishing pad with a new polishing pad. Therefore, the thickness measuring device 10 detects the thickness of the polishing pad 32, determines the life of the polishing pad 32 from the thickness, and when it is determined that the life of the polishing pad 32 has expired (use limit), the polishing pad 32 is replaced with a new one. Encourage to exchange for. The thickness of the polishing pad 32 is generally about 6 mm, and when it is worn to about 2 mm, it needs to be replaced.

In the thickness measuring device 10, the thickness of the polishing pad 32 is measured as follows. FIG. 3 is an operation explanatory view of the thickness measuring device 10, and the thickness measuring device 10 is operated in the order of (a), (b), (c), and (d) of FIG. Further, FIG. 4 is a timing chart of the thickness measuring device 10. Therefore, the measurement of the thickness of the polishing pad 32 will be described according to the operation diagrams (a) to (d) of FIG. 3 and together with the timing charts (steps Sa to Sd) of FIG.

When measuring the thickness of the polishing pad 32, first, the head arm 19 is swiveled according to the instruction of the control unit 15, and the polishing head 13 is moved from the position above the chuck surface 12a of the rotary chuck table 12 to the polishing pad thickness measurement sensor 14. Move to a position above. FIG. 3A shows a state in which the polishing head 13 has moved to a position above the polishing pad thickness measuring sensor 14. This state corresponds to the state of step Sa in FIG. 4, and the polishing pad thickness measuring sensor 14 and the polishing pad 32 are separated from each other. Then, the signal of the upper position detection sensor 35a is output OFF, and the signal of the lower position detection sensor 35b is output ON.

Then, according to the instruction of the control unit 15, the transition from step Sa to step Sb in FIG. 4 is started. In the transition to step Sb, the sensor elevating cylinder 34 is driven, and the polishing pad thickness measuring sensor 14 is raised toward the polishing head 13 by driving the sensor elevating cylinder 34. Further, when the polishing pad thickness measuring sensor 14 rises by a predetermined amount, the signal of the lower position detection sensor 35b is switched from ON to OFF. The signal of the lower position detection sensor 35b is switched from OFF to ON just before the polishing pad thickness measurement sensor 14 reaches step Sb as the polishing pad thickness measurement sensor 14 rises further. Then, the drive of the sensor elevating cylinder 34 is stopped by the instruction of the control unit 15, and the polishing pad thickness measuring sensor 14 is stopped at the raised position. FIG. 3B shows a state in which the polishing pad thickness measuring sensor 14 has been moved to an upper position. This state corresponds to the state of step Sb in FIG. 4, and the polishing pad thickness measuring sensor 14 and the polishing pad 32 are still separated from each other.

Then, according to the instruction of the control unit 15, the transition from step Sb in FIG. 4 to step Sc is started. In the transition to step Sb, the servomotor 24 is driven, and the polishing head 13 starts descending by the driving force of the servomotor 24. Then, in the middle of the descent, the lower surface of the polishing pad 32 and the upper surface of the polishing pad thickness measuring sensor 14 come into contact with each other. FIG. 3C shows a state in which the polishing pad holding plate 31 is loosely in contact with the upper surface of the polishing pad thickness measuring sensor 14 with the polishing pad 32 sandwiched between them. Further, the polishing head 13 is further lowered, and the polishing pad holding plate 31 of the polishing head 13 is strongly pressed against the upper surface of the polishing pad thickness measuring sensor 14 with the polishing pad 32 interposed therebetween. The signal T in FIG. 4 is a signal of the thickness of the polishing pad 32 measured by the measuring means 36 by the signal from the polishing pad thickness measuring sensor 14 just before the end of the transition from step Sb to step Sc. ..

Subsequently, according to the instruction of the control unit 15, the transition from step Sc to step Sd in FIG. 4 is started. The transition from step Sc to step Sd is continuously performed in the transition from step Sb to step Sc. That is, even if the lower surface of the polishing pad 32 comes into contact with the upper surface of the polishing pad thickness measuring sensor 14, the servomotor 24 is driven without being stopped. Then, the polishing pad holding plate 31 of the polishing head 13 is strongly pressed against the upper surface of the polishing pad thickness measuring sensor 14 with the polishing pad 32 sandwiched therein, and further, for polishing pad thickness measurement against the pushing force of the sensor elevating cylinder 34. Push down the sensor 14. As a result, the polishing pad 32 is sandwiched between the polishing pad holding plate 31 and the polishing pad thickness measuring sensor 14, and the polishing head 13 is strongly pressed against the upper surface of the polishing pad thickness measuring sensor.

In FIG. 3D, the lower surface of the polishing pad holding plate 31 is strongly pressed against the upper surface of the polishing pad thickness measuring sensor 14 with the polishing pad 32 sandwiched therein, and the polishing head 13 presses the polishing pad thickness measuring sensor 14. It shows the pushed down state. Just before the transition from step Sc to step Sd is completed, the signal of the upper position detection sensor 35a is switched from ON to OFF, and the polishing pad thickness measurement sensor 14 is pushed down to a predetermined position by the polishing head 13. Is output to the control unit 15. Then, in the control unit 15, the measuring means 36 acquires an electric signal from the polishing pad thickness measuring sensor 14 when the polishing head 13 is strongly pressed against the polishing pad thickness measuring sensor 14, and the signal is obtained by the polishing pad. It is possible to know the thickness of the polishing pad 32 based on the electric signal by converting it into the thickness amount of 32. As a result, the measuring means 36 detects the thickness of the polishing pad 32. Further, the determination means 37 determines the life of the polishing pad 32 from the thickness of the polishing pad 32 measured here. Then, when the replacement life has come to an end, the control unit 15 prompts the replacement of the polishing pad 32. After the measurement, the servomotor 24 and the sensor elevating cylinder 34 are controlled by the instruction of the control unit 15, the polishing head 13 is raised, and the polishing pad thickness measuring sensor 14 is lowered, and (a) in FIG. ) Return to the position. After that, the head arm 19 is swiveled according to the instruction of the control unit 15, the polishing head 13 is moved to a position above the chuck surface 12a of the rotary chuck table 12, and the polishing process is started again.

In the polishing pad thickness measuring device 10 in the polishing device 11 according to the configuration of this embodiment, when measuring the thickness of the polishing pad 32 of the polishing head 13, the polishing pad holding plate 31 is sandwiched between the polishing pads 32 and the polishing pad thickness. It is pressed against the measurement sensor 14 to measure the thickness of the polishing pad 32. When the distance between the polishing pad thickness measuring sensor 14 and the polishing pad holding plate 31 is measured with the polishing pad 32 sandwiched in this way, the distance between the polishing pad thickness measuring sensor 14 and the polishing pad holding plate 31 is measured. Can be obtained as the thickness of the polishing pad 32. Thereby, the thickness of the polishing pad 32 at the time of measurement can be known directly and accurately.

Further, since the polishing pad 32 is made of a non-conductor material, the polishing pad holding plate 31 is made of a conductor material, and the eddy current type displacement sensor is used as the polishing pad thickness measurement sensor 14, it is not. An eddy current is not generated on the polishing pad 32 of the conductor material, and an eddy current is generated only on the polishing pad holding plate 31 which is a conductor. Therefore, when the distance from the top of the polishing pad 32 to the polishing pad holding plate 31 is measured, the distance to the polishing pad holding plate 31 is accurately obtained as the thickness of the polishing pad 32 without being affected by the polishing pad 32. be able to.

Further, since the control unit 15 includes a determination means 37 for determining the life of the polishing pad 32 from the measured thickness of the polishing pad 32, it is possible to directly and accurately know the life at the time of measurement. can.

Although the case where the eddy current type sensor is used as the polishing pad thickness measuring sensor 14, the case where the eddy current type sensor is used, the linear scale, the laser type sensor, the ultrasonic sensor, the proximity sensor and the like are used as the eddy current type sensor. It can be used as 14.

In addition, the present invention can be modified in various ways as long as it does not deviate from the spirit of the present invention, and it is natural that the present invention extends to the modified ones.

10: Thickness measuring device 11: Polishing device 12: Rotating chuck table 12a: Chuck surface 12b: Table shaft 13: Polishing head 14: Polishing pad thickness measuring sensor 15: Control unit 16: Table motor 17: Polishing head shaft 18: Actuator 19: Head arm 20: Support base 21: Bearing 22: Bridge 23: Ball screw mechanism 23a: Screw shaft 23b: Nut 24: Servo motor 25: Ball spline bearing 26: Pulley 27: Polishing head rotation motor 28: Pulley 29: Belt 30: Swing shaft 31: Polishing pad holding plate 32: Polishing pad 33: Sensor holding base 34: Sensor elevating cylinder 34a: Rod 35a: Upper position detection sensor 35b: Lower position detection sensor 36: Measuring means 37: Judgment means Sa: Step Sb: Step Sc: Step Sd: Step T: Signal W: Bearing

Claims (3)

A polishing pad thickness measuring device that measures the thickness of the polishing pad used to polish the object to be polished.
A polishing pad holding plate to which the polishing pad is attached and rotates integrally and can be moved in the vertical direction,
A polishing pad thickness measurement sensor that is pressed against the polishing pad holding plate at a substantially right angle via the polishing pad and outputs an electric signal according to the distance to the polishing pad holding plate.
A control unit having a measuring means for measuring the thickness of the polishing pad based on the electric signal from the sensor for measuring the thickness of the polishing pad, and a control unit.
A polishing pad thickness measuring device comprising. The polishing pad is made of a non-conductive material and is made of a non-conductive material.
The polishing pad holding plate is made of a conductor material and is made of a conductor material.
The sensor for measuring the thickness of the polishing pad is an eddy current type displacement sensor.
The polishing pad thickness measuring device according to claim 1. The control unit includes a determination means for determining the life of the polishing pad from the measured thickness of the polishing pad.
The polishing pad thickness measuring device according to claim 1 or 2.

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