JP2973404B2 - Wafer polishing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer polishing apparatus, and more particularly, to a chemical mechanical polishing method (CMP).
ical Polishing).

[0002]

2. Description of the Related Art In a wafer polishing apparatus using CMP, it is difficult to directly detect the polishing amount of a wafer during polishing. Therefore, conventionally, the polishing amount of a wafer has been controlled by controlling the polishing time. For this reason, conventionally, a dummy wafer is polished at regular intervals to obtain a polishing amount according to the polishing time, and this polishing amount is compared with a reference model polishing amount, and if the difference is within an allowable value, If the difference is out of the allowable range, the polishing is interrupted to dress the polishing cloth or replace the polishing cloth.

[0003] JP-A-6-79618 and JP-A-8-2298
In the wafer polishing apparatus disclosed in Japanese Patent Application Publication No. 08-203, a wafer is polished by holding a wafer in close contact with a carrier and then applying a pressing force to the carrier to press the wafer against a polishing cloth. Further, as a conventional wafer polishing apparatus using CMP, an apparatus has been proposed in which air is supplied between a carrier and a wafer, and the wafer is pressed against a polishing pad by the pressure of the air to polish the wafer. In such a wafer polishing apparatus, it has been difficult to directly detect the polishing amount of the wafer. Therefore, the fluctuation amount of the carrier is detected by a sensor based on the main body of the wafer polishing apparatus, and the output from the sensor is output. The polishing amount was regarded as the polishing amount, and the polishing amount of the wafer was indirectly detected.

[0004]

However, in the conventional wafer polishing apparatus, since the polishing time is managed to control the polishing amount of the wafer, the end point (target value) of the polishing amount cannot be accurately detected. There is a drawback that you can not. Also,
The conventional wafer polishing apparatus has a drawback that the yield of the wafer is deteriorated because the dummy wafer is polished to determine the dressing time and the replacement time of the polishing pad.

Further, during the polishing of the dummy wafer, the normal polishing is interrupted, so that there is a disadvantage that the throughput is reduced. In addition, JP-A-6-79618, and the wafer polishing apparatus disclosed in JP-A-8-229808,
Since the carrier directly presses the wafer against the polishing cloth, if there is foreign matter such as polishing debris between the carrier and the wafer, the pressing force from the carrier cannot be transmitted uniformly to the entire surface of the wafer, thereby There is a disadvantage that the entire surface of the wafer cannot be uniformly polished.

Further, in a conventional wafer polishing apparatus for detecting a polishing amount of a wafer with reference to a main body of the wafer polishing apparatus, the main body expands thermally due to heat generated during polishing, so that a fluctuation amount of a carrier is detected. However, there is a disadvantage that an accurate amount of polishing of the wafer cannot be obtained, and the end point of polishing of the wafer cannot be accurately detected.

The present invention has been made in view of such circumstances, and it is possible to automatically determine the dressing time and replacement time of a polishing pad during normal polishing, and to determine the end point of wafer polishing. It is an object of the present invention to provide a wafer polishing apparatus that can accurately detect, furthermore, can uniformly polish the entire surface of the wafer and can accurately detect the end point of the polishing amount.

[0008]

According to the present invention, in order to achieve the above object, a polishing cloth is provided on the surface, a polishing platen for rotating the polishing cloth, and a wafer holding and polishing the surface of the wafer. A wafer holding head that rotates while being pressed against the polishing cloth, wherein the wafer holding head contacts the polishing cloth at a predetermined pressure with a carrier that holds the wafer and contacts the polishing cloth at a predetermined pressure. A polishing surface adjustment ring provided around the wafer as described above, in a wafer polishing apparatus, detecting means for detecting the amount of change of the carrier with respect to the polishing surface adjustment ring on the central axis of the wafer by one detector. It is characterized by comprising a.

According to the present invention, in order to achieve the above object, a polishing cloth is provided on the surface, and a polishing platen for rotating the polishing cloth and a wafer holding the wafer and pressing the surface of the wafer against the polishing cloth. A rotating wafer holding head, wherein the wafer holding head is configured to hold the wafer and make contact with the polishing cloth at a predetermined pressure, and around the wafer to make contact with the polishing cloth at a predetermined pressure. In the wafer polishing apparatus provided with a polishing surface adjustment ring provided in the, while being provided between the polishing surface adjustment ring and the carrier, a plurality of surfaces or cylindrical end surfaces that contact the polishing cloth at a predetermined pressure. The formed pressing member and detecting means for detecting the relative displacement between the back surface of the wafer and the pressing member on the center position of the wafer with one detector are provided. It is characterized in that was. According to the present invention, in order to achieve the above object, a polishing cloth is provided on the surface, a polishing platen for rotating the polishing cloth, and a wafer holding and rotating while pressing the surface of the wafer against the polishing cloth. A wafer holding head, wherein the wafer holding head is provided around the wafer so as to hold the wafer and contact the polishing cloth at a predetermined pressure, and to contact the polishing cloth at a predetermined pressure. In the wafer polishing apparatus provided with a polishing surface adjustment ring is provided between the polishing surface adjustment ring and the carrier, a plurality of surfaces or a cylindrical end surface that contacts the polishing cloth at a predetermined pressure is formed. A pressing member, and detecting means for detecting a relative displacement between the carrier and the pressing member on a center position of the wafer with one detector. It is.

In order to achieve the above object, the present invention provides a wafer polishing apparatus for polishing a surface of a wafer by pressing the wafer against a rotating polishing cloth, and a polishing amount detecting means for detecting a polishing amount of the wafer; A storage unit in which a model polishing amount of the wafer according to the polishing time is stored; a polishing amount of the wafer detected by the polishing amount detecting unit; and a model polishing amount stored in the storage unit. It determines the replacement timing of dressing timing and polishing cloth of the polishing cloth on the basis of the difference in the amount, and control means for outputting the determination content, consisting of a display means for displaying the outputted the determination content from said control means It is characterized by:

According to the first aspect of the present invention, there is provided a polishing surface adjusting ring pressed against the polishing cloth together with the wafer,
The amount of polishing of the wafer is detected by detecting the amount of fluctuation of the carrier with respect to the polishing surface adjusting ring on the central axis of the wafer by the detector, so that the end point of polishing of the wafer can be accurately detected. According to the invention described in claim 2, the pressing member is pressed against the polishing pad together with the wafer, and the relative displacement between the pressing member and the back surface of the wafer or the relative displacement between the pressing member and the carrier is detected by a detector. Since the polishing amount of the wafer is detected, the polishing end point of the wafer can be accurately detected.

Further, since the detector detects the relative displacement between the back surface of the wafer and the pressing member at the center position of the wafer, the end point of the polishing of the wafer can be detected more accurately. That is, the center of the wafer has less vibration during polishing than any other part of the wafer.
Therefore, the present invention that detects the polishing amount of the back surface of the wafer on the center position of the wafer can more accurately detect the polishing amount of the wafer, and thus can more accurately detect the polishing end point of the wafer. . The same effect can be obtained by detecting the relative displacement between the carrier and the pressing member on the center position of the wafer by the detector.

According to the fourth aspect of the present invention, the polishing amount of the wafer during polishing is detected by the polishing amount detecting means, and the control means stores the polishing amount of the wafer detected by the polishing amount detecting means in the memory. Compare the model polishing amount stored in the means. Then, the control means determines the dressing time of the polishing cloth and the replacement time of the polishing cloth based on the difference in the polishing amount, and causes the display device to display the contents of the determination. As a result, the present invention can automatically determine the dressing time and replacement time of the polishing cloth during normal polishing.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer polishing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a wafer polishing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the wafer polishing apparatus 10 mainly includes a polishing platen 12 and a wafer holding head 14. The polishing platen 12 is formed in a disk shape, and a polishing cloth 16 is provided on an upper surface thereof. A spindle 18 is provided below the polishing platen 12.
The spindle 18 is connected to an output shaft (not shown) of the motor 20. The polishing platen 12 rotates in the direction of arrow A by driving a motor 20, and a slurry is supplied from a nozzle (not shown) onto the polishing cloth 16 of the rotating polishing platen 12. The wafer holding head 14 is provided to be vertically movable by an elevating device (not shown). The wafer holding head 14 is moved up when setting a wafer to be polished on the wafer holding head 14, and is moved down when polishing a wafer. It is pressed against the polishing cloth 16.

FIG. 2 is a longitudinal sectional view of the wafer holding head 14. The wafer holding head 14 shown in FIG. 1 includes a head body 22, a carrier 24, a guide ring 26, a polishing surface adjustment ring 28, a rubber sheet 30, and the like. The head body 22 is formed in a disk shape,
The motor 2 is rotated in the direction of arrow B by a motor (not shown) connected to the motor 2. The air supply path 3 is provided in the head body 22.
4 and 36 are formed. The air supply path 34 extends outside the wafer holding head 14 as shown by a two-dot chain line in FIG. 2 and has a regulator (R) 38A.
To an air pump (AP) 40. The air supply path 36 is connected to an air pump 40 via a regulator 38B.

The carrier 24 is formed in a substantially cylindrical shape, and is disposed coaxially with the head main body 22 below the head main body 22. Further, a concave portion 25 is provided on the lower surface of the carrier 24.
Are formed, and the porous plate 4 having air permeability is formed in the concave portion 25.
2 are stored. The air chamber 2 is located above the porous plate 42.
The air chamber 27 is communicated with an air suction path 44 formed in the carrier 24. The air suction path 44 extends outside the wafer holding head 14 as shown by a two-dot chain line in FIG.
suction pump) 46. Therefore, when the suction pump 46 is driven, the wafer 50 is sucked by the porous plate 42 and held by suction on the lower surface of the porous plate 42. The porous plate 42 has a number of air passages therein, and for example, a porous plate made of a sintered body of a ceramic material is used.

The carrier 24 has a plurality of air supply paths 48, 48,.
(Only two locations are shown in FIG. 2). The air supply paths 48 extend outside the wafer holding head 14 as shown by a two-dot chain line in FIG. 2 and are connected to the pump 40 via a regulator 38C. Therefore, the compressed air supplied from the air pump 40 through the regulator 38C is blown out into the air chamber 51 between the porous plate 42 and the wafer 50 through the air supply paths 48, 48. As a result, a pressurized air layer is formed in the air chamber 51, and the pressing force of the carrier 24 is transmitted to the wafer 50 via the pressurized air layer, and
Is pressed against the polishing pad 16. When the wafer 50 is directly pressed against the polishing pad 16 by the carrier 24, if there is dust between the carrier 24 and the wafer 50, the carrier 2
4 cannot be uniformly transmitted to the entire surface of the wafer 50, but if the wafer 50 is pressed through the pressurized air layer as described above, even if there is dust between the carrier 24 and the wafer 50, 24 pressing force to wafer 50
It can be transmitted uniformly over the entire surface.

The wafer holding head 14 controls the pressing force applied to the carrier 24 to move the carrier 24 up and down, thereby controlling the polishing pressure of the wafer 50 (the force pressing the wafer 50 against the polishing pad 16). Therefore, the control of the polishing pressure is easier than the control of the polishing pressure of the wafer 50 by controlling the pressure of the pressure air layer. That is, in the wafer holding head 14, the polishing pressure of the wafer 50 can be controlled only by controlling the vertical position of the carrier 24. The air supply paths 48, 4
8 are exhausted to the outside through exhaust holes (not shown) formed in the polishing surface adjusting ring 28.

The carrier 24 has a large number of air / water supply passages 5 each having an ejection port formed on the lower surface of the carrier 24.
2, 52... (Only two locations are shown in FIG. 2).
The air / water supply paths 52 extend outside the wafer holding head 14 as shown by a two-dot chain line in FIG. An air pump 40 is connected to one branch via a regulator 38D, and a water pump (WP) 56 is connected to the other branch. Therefore, the valve 54 opens the path on the air pump 40 side,
When the path on the water pump 56 side is closed, compressed air from the air pump 40 is supplied to the air / water supply paths 52, 52.
Are supplied to the air chamber 51 via the. When the valve 54 is switched to close the path on the air pump 40 side and open the path on the water pump 56 side, the water from the water pump 56 is supplied to the air / water supply paths 52, 52.
Are supplied to the air chamber 51 via the.

On the other hand, a rubber sheet 30 is arranged between the carrier 24 and the head body 22. This rubber sheet 30 is formed in a single disk shape with a uniform thickness. The rubber sheet 30 is fixed to the lower surface of the head body 22 by an annular stopper 58, and the rubber sheet 30 is divided into a center part 30 </ b> A and an outer peripheral part 30 </ b> B with the stopper 58 as a boundary. The center 30A of the rubber sheet 30 is the carrier 2
4, the outer peripheral portion 30B presses the polishing surface adjustment ring 28.

A rubber sheet 3 is provided below the head body 22.
A space 60 which is hermetically sealed by the central portion 30 </ b> A and the stopper 58 is formed. The air supply path 36 communicates with the space 60. Therefore, when compressed air is supplied from the air supply path 36 to the space 60, the central portion 30A of the rubber sheet 30 is elastically deformed by air pressure and presses the upper surface of the carrier 24. Thereby, a pressing force of the wafer 50 against the polishing pad 16 can be obtained. Further, if the air pressure is adjusted by the regulator 38B, the pressing force of the wafer 50 can be controlled.

The guide ring 26 is formed in a cylindrical shape, and is disposed coaxially with the head main body 22 below the head main body 22. In addition, the guide ring 26 is attached to the rubber sheet 3.
0 is fixed to the head main body 22. Further, a polishing surface adjusting ring 28 is disposed between the guide ring 26 and the carrier 24. This polishing surface adjustment ring 2
8, a retainer ring 62 for preventing the wafer 50 from jumping out is attached to an inner peripheral portion of the lower portion.

An annular space 64 is formed in the lower outer peripheral portion of the head main body 22 so as to be sealed by the outer peripheral portion 30B of the head main body 22 and the rubber sheet 30 and the like. This space 6
4 communicates with the air supply path 34. Therefore, when compressed air is supplied from the air supply path 34 to the space 64, the outer peripheral portion 30B of the rubber sheet 30 is elastically deformed by air pressure and presses the annular upper surface of the polishing surface adjustment ring 28. As a result, the annular lower surface of the polishing surface adjusting ring 28 is
Pressed to 6. The pressing force of the polishing surface adjusting ring 28 can be controlled by adjusting the air pressure with the regulator 38A.

The wafer holding head 14 is provided with a polishing amount detecting device for detecting the polishing amount of the wafer 50. This polishing amount detecting device includes a sensor 70 including a core 66 and a bobbin 68, a non-contact type sensor 72,
72, 72, and these sensors 7
CPU (shown in FIG. 3) 74 for performing arithmetic processing on detection signals output from 0, 72, 72, 72 is provided outside the wafer holding head 14.

The bobbin 68 of the sensor 70 is attached to the tip of an arm 76 extending from the inner surface of the polishing surface adjusting ring 28 in the direction of the rotation axis of the wafer holding head 14. The core 66 of the sensor 70 is provided at a position where the center axis of the core 66 is coaxial with the rotation axis of the wafer holding head 14. The sensor 70 detects the amount of vertical movement of the carrier 24 with respect to the lower surface of the polishing surface adjustment ring 28, that is, with respect to the polishing pad 16. The carrier 24 has a groove 7 for inserting the arm 76.
8 are formed.

Although the polishing amount of the wafer 50 can be generally detected by the sensor 70, in the present embodiment, the detection value detected by the sensor 70 is
The amount of polishing of the wafer 50 is accurately obtained by correcting with the detection values detected in steps 2 and 72. The sensor 72 is a non-contact sensor such as an eddy current sensor, and its detection surface 72 a is arranged flush with the lower surface of the porous plate 42, and detects the distance from the upper surface of the wafer 50 to form a pressure air layer. The amount of change in the layer thickness of the (air chamber 51) is detected.

The CPU 74 shown in FIG. 3 calculates the sensor 7 based on the fluctuation amount of the carrier 24 detected by the sensor 70.
The polishing amount of the wafer 50 is calculated by adding the fluctuation amount of the thickness of the pressure air layer detected in 2, 72, 72. That is, the CPU 74 calculates the polishing amount of the wafer 50 from the fluctuation amount with respect to the reference value stored in advance. For example, if the fluctuation amount detected by the sensor 70 is T1 and the average value of the fluctuation amounts detected by the sensors 72, 72, 72 is T2, the polishing amount of the wafer 50 at that time is calculated by T1 + T2. If the variation from the sensor 70 is T1 and the average value of the variations from the sensors 72, 72, 72 is O, the polishing amount of the wafer 50 at that time is calculated by T1-0. Further, the variation from the sensor 70 is T1, and the sensor 7
If the average value of the fluctuation amounts from 2, 72 and 72 is -T2, the polishing amount of the wafer 50 at that time is calculated by T1-T2. Thus, in the present embodiment, the sensors 70, 7
2, the polishing amount is calculated from the two fluctuation amounts, so that the polishing amount of the wafer 50 can be accurately detected.

In the wafer holding head 14,
The sensor 70 is arranged coaxially with the rotation axis of the wafer holding head 14. Since the arrangement position of the sensor 70 corresponds to the central axis of the wafer 50 being polished, the sensor 70 detects the polishing amount at the center of the wafer 50. The center of the wafer 50 has less vibration during polishing than any other part of the wafer 50. Therefore, the sensor 70 accurately detects the amount of polishing of the wafer 50.

In FIG. 3, an external input device 80 such as a keyboard is connected to the CPU 74.
Information indicating the model polishing amount of the wafer according to the polishing time is input from the external input device 80 to the CPU 74.
FIG. 4 shows the model polishing amount of the wafer and the actually measured polishing amount according to the polishing time. The vertical axis of the graph in FIG. 4 indicates the polishing amount and the polishing pressure, and the horizontal axis indicates the polishing time.

The model polishing amount (polishing target value: 5000 °) indicated by the two-dot chain line in FIG. 4 is set by inputting the polishing pressure during the polishing time with the external input device 80. That is, the polishing pressure from the start of polishing to t1 is set to P1,
After the elapse of t1, the polishing pressure until the polishing end time t2 is set to P2. When such a polishing pressure is set, the polishing amount per unit time is large from the start of polishing to t1, and after the elapse of t1, the polishing amount per unit time is small until the polishing end time t2, and the polishing is performed gently.

A graph showing the actual polishing amount indicated by the solid line in FIG. 4 shows the actual polishing amount when polishing is performed based on the polishing pressure (polishing pressure for obtaining the model polishing amount) set by the external input device 80. It is a graph shown. The CPU 74 determines the dressing time and the replacement time of the polishing pad 16 based on the difference δ between the polishing amount and the model polishing amount. That is, CPU
Reference numeral 74 has a first threshold value for determining the dressing time and a second threshold value for determining the replacement time, and determines whether to perform continuous polishing, dressing, or replacement according to the difference δ. This determination result is displayed on the display device 82 shown in FIG.

The polishing pressure set by the external input device 80 is stored in the RAM 84, and the actual polishing amount is also stored in the RAM 84. Further, the RAM 84 stores an actual polishing amount acquired last time and a plurality of histories of the actual polishing amount. Further, the CPU 74 reads the previously obtained actual polishing amount from the RAM 84, compares this polishing amount with the actual polishing amount obtained this time, calculates the fluctuation amount of the polishing amount, and continues from the magnitude of the fluctuation amount. It can also be determined whether to grind, dress, or replace.

Next, the operation of the wafer holding head 14 of the wafer polishing apparatus 10 configured as described above will be described with reference to FIG.
This will be described with reference to FIG. First, after raising the wafer holding head 14, the suction pump 46 is driven to suck and hold the wafer 50 to be polished on the porous plate 42. Next, the wafer holding head 14 is lowered, and the lower surface of the polishing surface adjustment ring 28 of the wafer holding head 14 is
The descending movement is stopped at the position where it comes into contact with 6. Then, the suction pump 46 is stopped to release the suction of the wafer 50, and the wafer 50 is placed on the polishing pad 16.

Next, the air pump 40 is driven to supply compressed air to the air chamber 51 via the air supply path 48, and a pressure air layer for uniformly transmitting the pressing force of the carrier 24 to the entire surface of the wafer 50 is formed. 51. Then, the compressed air from the air pump 40 is supplied to the space 60 via the air supply path 36, and the center 30A of the rubber sheet 30 is elastically deformed by the internal air pressure to press the carrier 24. Thus, the pressing force of the central portion 30A of the rubber sheet 30 is transmitted from the carrier 24 to the wafer 50 via the pressure air layer, and the wafer 50 is pressed against the polishing pad 16. Then, the air pressure is adjusted by the regulator 38B to control the internal air pressure to a desired pressure.
Is kept constant.

Next, compressed air from the air pump 40 is supplied to the space 64 through the air supply path 34,
The outer peripheral portion 30 </ b> B is elastically deformed by the internal air pressure to press the polishing surface adjustment ring 28 and press the polishing surface adjustment ring 28 against the polishing pad 16. And the regulator 38A
The air pressure is adjusted to control the internal air pressure to a desired pressure, and the pressing force of the polishing surface adjusting ring 28 against the polishing pad 16 is kept constant.

Then, a polishing pressure for obtaining a model polishing amount is input from the external input device 80 shown in FIG. 3 to the CPU 74, and thereafter, the polishing platen 12 and the wafer holding head 14 are rotated to remove the wafer 50. Start polishing. The setting time of the polishing pressure by the external input device 80 may be set immediately before the polishing or may be set in advance.

Next, when the polishing of the first wafer 50 is completed, the CPU 74 calculates a difference δ between the actual polishing amount according to the polishing time of the wafer 50 and the model polishing amount. Then, the CPU 74 compares the two threshold values stored in advance with the calculated difference δ, and determines whether to perform continuous polishing, dressing, or replacement based on the difference,
This determination result is displayed on the display device 82. Then, when “continuous polishing” is displayed on the display device 82, the next wafer is polished by the wafer polishing apparatus 10 without stopping the wafer polishing apparatus 10. When "dressing" is displayed, after temporarily stopping the wafer polishing apparatus 10, the dressing grindstone is brought into contact with the polishing pad 16 to perform dressing for a predetermined time. After that, the wafer polishing apparatus 10 is restarted to continue the wafer polishing. When "Replace" is displayed, after temporarily stopping the wafer polishing apparatus 10, the polishing cloth 16 is replaced with a new polishing cloth 16, and thereafter, the wafer polishing apparatus 10 is restarted to perform wafer polishing. Continue to do so.

As described above, in the present embodiment, the wafer 5
Since the actual polishing amount of 0 and the preset model polishing amount are compared, the dressing time of the polishing pad 16 and the replacement time of the polishing pad 16 are determined based on the difference δ of the polishing amount. The dressing time and replacement time of the polishing pad 16 can be automatically determined during normal polishing. FIG. 5 is an explanatory diagram showing the pressure applied to the wafer 50 from the polishing cloth 16 when the polishing surface adjustment ring 28 is pressed against the polishing cloth 16 with a predetermined pressing force.

As shown in FIG.
Polishing cloth 1 produced by pressing
The pressure of No. 6 is maximum at the outer peripheral portion of the polishing surface adjusting ring 28 in the region L1 where the polishing surface adjusting ring 28 is in contact, and decreases rapidly, and It tends to gradually increase as you go. The area L2 where the wafer 50 is in contact
At the edge portion of the wafer 50, there is a slight change in pressure, but the other pressures are uniform. Therefore, when the polishing surface adjustment ring 28 is used, the wafer 50
Swelling of the polishing pad 16 at the peripheral edge of the surface can be suppressed. As a result, the pressure applied to the wafer 50 from the polishing pad 16 can be made substantially uniform.
0 can be uniformly polished.

The thickness of the wafer 50 is a thickness known in advance, and the wafer processing surface and the polishing surface adjustment ring 28
Can also be detected with respect to the position of contact with the polishing cloth 16.
The pressing of the polishing surface adjusting ring 28 can also be accurately adjusted. Wafer holding head 1 using polishing surface adjusting ring 28
According to 4, the polishing pressure is set by the external input device 80 shown in FIG. 3, and the pressing force of the polishing surface adjusting ring 28 is set to a pressing force capable of suppressing the swelling of the polishing pad 16 at the peripheral edge of the wafer 50. I do. After this,
The polishing of the wafer 50 is started by rotating the polishing platen 12 and the wafer holding head 14.

The CPU 74 calculates the polishing amount of the wafer 50 during polishing based on the detection signals output from the sensors 70, 72, 72, 72. And C
When the polishing amount of the wafer 50 calculated by the PU 74 reaches a preset polishing target value shown in FIG.
4 outputs a polishing end signal and stops the wafer polishing apparatus 10. Thus, polishing of one wafer 50 is completed. When the second and subsequent wafers 50 are polished, the above-described steps may be repeated. FIG.
Is a graph showing a polishing amount with respect to a polishing time.

As described above, in this embodiment, the polishing amount of the wafer is detected, and a polishing end signal is output when the detected polishing amount of the wafer reaches a preset polishing target value. Therefore, the end point of the polishing amount can be accurately detected. Further, in the present embodiment, the pressure air layer is formed between the carrier 24 and the wafer 50 and the wafer 50 is polished.
Even when there is a foreign matter such as polishing dust between the wafer 50 and the surface of the wafer 50, the entire surface of the wafer 50 can be uniformly polished.

In the polishing apparatus disclosed in Japanese Patent Application Laid-Open No. 9-57613, the end point of polishing of a wafer is detected by using a single displacement detecting device. Since it is a device that directly holds and grinds, carrier 2
The configuration is completely different from the wafer polishing apparatus of the present invention in which a pressure air layer is formed between the wafer 4 and the wafer 50. When the wafer 50 is polished through the pressure air layer as in the present invention, a sensor 70 for detecting the displacement of the carrier 24 is used.
By using the sensor 72 for detecting the thickness of the pressure air layer, the polishing end point of the wafer 50 can be accurately detected.

FIG. 7 shows a second example of the wafer holding head 114.
FIG. 8 is a plan view showing the embodiment of FIG.
It is a longitudinal cross-sectional view along a line. 8 includes a head body 122, a carrier 124, a guide ring 126, a polishing surface adjustment ring 128, a retainer ring 130, a rubber sheet 132, and a differential transformer 13.
4 and a pressing member 136 and the like.

The head body 122 is formed in a disk shape, and has a rotating shaft 138 connected to the upper surface thereof, and is rotated in the direction of arrow B by a motor (not shown) connected to the rotating shaft 138. Further, air supply paths 140, 142, 144 are formed in the head main body 122.
The air supply path 140 extends outside the wafer holding head 114 as shown by a two-dot chain line in FIG. 8 and is connected to an air pump (AP) 148 via a regulator (R) 146A. . Similarly, the air supply paths 142 and 144 also
And the air supply path 142 is connected to the regulator 1
46B to the air pump 148, and the air supply path 144 to the air pump 1 via a regulator 146C.
48.

The carrier 124 is formed in a substantially columnar shape, and is arranged coaxially with the head main body 122 below the head main body 122. In addition, a concave portion 125 is formed on the lower surface of the carrier 124, and a porous plate 150 having air permeability is accommodated in the concave portion 125. In the porous plate 150, air passages 152, 152 formed in the carrier 124 are provided.
Are communicated with each other, and these air paths 152, 152 are
As shown by the two-dot chain line in FIG.
And is connected to an air pump 148 via a regulator 146D. Therefore, when the air pump 148 is driven, the compressed air from the air pump 148 is supplied to the space 15 between the porous plate 150 and the wafer 154 via the air passages 152 and 152 and the porous plate 150.
It is blown out to 6. As a result, a pressure air layer is formed in the space 156, and the carrier 12 is formed through the pressure air layer.
4 is transmitted to the wafer 154. Wafer 1
The polishing pad 54 is polished by being pressed against the polishing pad 116 by the pressing force transmitted through the pressure air layer. Further, a switching valve 180 is provided in the air passages 152, 152.
Suction pump (SP) 18
2 are connected. Therefore, the switching valve 18
When the suction pump 182 is driven by switching 0,
The wafer 154 is sucked by the porous plate 150 and held by the porous plate 150. The porous plate 150
Has a number of ventilation paths inside, for example,
What consists of a sintered body of a ceramic material is used.

On the other hand, the head body 122 and the carrier 124
A single rubber sheet 132 is disposed between the two. The rubber sheet 132 is formed in a disk shape with a uniform thickness. The rubber sheet 132 is fixed to the lower surface of the head main body 122 by two large and small annular stoppers 158 and 160. Thereby, the rubber sheet 132
The center part 132A and the middle part 1
32B and a middle part 132B and an outer peripheral part 132C with a stopper 158 as a boundary. That is, the rubber sheet 132 is divided into three parts by the stoppers 158 and 160, the central part 132A presses the carrier 124, the intermediate part 132B presses the pressing member 136, and the outer peripheral part 132C presses the polishing surface adjustment ring 128. Function as airbags for

Of the air bag, the rubber sheet 13
The air supply path 140 is communicated with an airbag 162 defined by the central portion 132A of the second airbag. Therefore, when compressed air is supplied from the air supply path 140 to the airbag 162, the central portion 132A of the rubber sheet 132 is elastically deformed by air pressure and presses the upper surface of the carrier 124. Thereby, the wafer 154 with respect to the polishing cloth 116 is formed.
Pressing force can be obtained. Further, if the air pressure is adjusted by the regulator 146A, the pressing force (polishing pressure) of the wafer 154 can be controlled.

The guide ring 126 is formed in a cylindrical shape, and is disposed coaxially with the head main body 122 below the head main body 122. The guide ring 126 is fixed to the head main body 122 via a rubber sheet 132. Between the guide ring 126 and the carrier 124,
A polishing surface adjustment ring 128 is provided. A retainer ring 130 for preventing the wafer 154 from jumping out is attached to the lower inner peripheral portion of the polishing surface adjusting ring 128.

At the lower outer peripheral portion of the head main body 122,
An annular airbag 164 defined by the outer peripheral portion 132C of the rubber sheet 132 and the stopper 158 is formed. The air bag 164 is connected to the air supply path 144.
Is communicated. Therefore, when compressed air is supplied from the air supply path 144 to the air bag 164, the outer peripheral portion 132 </ b> C of the rubber sheet 132 is elastically deformed by air pressure and presses the annular upper surface 128 </ b> A of the polishing surface adjustment ring 128, and Of the polishing cloth 11
Pressed to 6. The pressing force of the polishing surface adjusting ring 128 can be controlled by adjusting the air pressure with the regulator 146C.

A pressing member 136 is disposed between the carrier 124 and the polishing surface adjusting ring 128. The pressing member 136 includes the main body 136A, the head 13
6B, a support arm 136C, and a leg 136D. The head portion 136 of the pressing member 136
B, three support arms 136C, and three leg portions 136D are formed at regular intervals as shown by dotted lines in FIG. The legs 136D are not limited to three, and may be formed in a cylindrical shape so as to cover the entire circumference of the carrier 124.

The main body 13 of the pressing member 136 shown in FIG.
6A is an opening 1 formed in the polishing surface adjustment ring 128.
29. The head 136B of the pressing member 136 is formed integrally with the main body 136A, and is disposed in a gap between the carrier 124 and the polishing surface adjustment ring 128. Above the head 136B,
The intermediate portion 132B of the rubber sheet 132 and the stoppers 158, 1
60 form an annular airbag 166. The air supply path 142 communicates with the air bag 166. Therefore, the air supply path 1
When compressed air is supplied from 42 to the air bag 166,
The intermediate portion 132B of the rubber sheet 132 is elastically deformed by air pressure and presses the head 136B of the pressing member 136. Thereby, the lower surface 137 of the leg 136D of the pressing member 136 is formed.
Is pressed against the polishing pad 116. The pressing member 13
The pressing force of No. 6 can be controlled by adjusting the air pressure with the regulator 146B. The leg 136D is disposed in a through hole 128C formed in the polishing surface adjustment ring 128. Thereby, the leg 13
Since the surface of the polishing cloth 116 with which the lower surface 137 of the 6D abuts is leveled by the polishing surface adjusting ring 128,
The pressing member 136 is prevented from vibrating up and down by the uneven surface of the polishing pad 116.

The pressing member 138 is manufactured using a low thermal expansion material (amber) having a very low coefficient of thermal expansion as a base material in order to prevent thermal expansion due to polishing processing heat, and is pressed by the polishing cloth 116. The lower surface 137 is
Diamond coated so that it is not polished. The lower surface 137 is not limited to the diamond coating, and may be formed of a material (for example, ceramic) having a significantly lower processing rate than the wafer 154.

On the other hand, the support arm 1 of the pressing member 136
A differential transformer 134 for detecting the polishing amount of the wafer 154 is provided at the tip of 36C. The differential transformer 134 includes a core 170, a bobbin 172, and a contact 174. The bobbin 172 includes
An arithmetic unit (not shown) for calculating the polishing amount of the wafer 154 based on the vertical movement amount of the core 170 with respect to the bobbin 172 is connected.

The bobbin 172 is fixed to the distal end of the support arm 136C of the pressing member 136.
The core 170 is arranged in the inside 2 so as to be vertically movable. A rod 176 is fixed to the lower part of the core 170 coaxially with the core 70, and the contact 174 is fixed to a lower end of the rod 176. The rod 176
Are arranged in a through-hole 124 </ b> A formed in the carrier 124. Further, the contact 174 is provided on the porous plate 150.
And is brought into direct contact with the back surface 154A of the wafer 154 being polished. The carrier 124 is preferably provided with a stopper member for preventing the rod 176 from falling off, and a packing for preventing leakage of the air supplied to the space 156 is preferably provided in the through hole 124A.

Next, the operation of the wafer holding head 114 configured as described above will be described. First, after raising the wafer holding head 114, the suction pump 1
82 to drive the wafer 154 to be polished to the porous plate 1.
50 is held by suction. Next, the wafer holding head 11
4 is lowered, and the lowering movement of the wafer holding head 114 is stopped at a position where the contact surface of the polishing surface adjusting ring 128 of the wafer holding head 114 is in contact with the polishing pad 116.
Then, the suction pump 182 is stopped and the wafer 1 is stopped.
Then, the suction of the wafer 54 is released, and the wafer 154 is placed on the polishing pad 116. At this time, the contact 17 of the differential transformer 134
4 indicates that the wafer 15
4, and moves down (falls) to come into contact with the back surface 154A of the wafer 154 as shown in FIG. Then, the contact position is automatically set in the arithmetic unit as a zero point.

Next, the switching valve 180 is connected to the air pump 1
After switching to the 48 side, the air pump 148 is driven to supply compressed air to the space 156 via the air path 152, and a pressure air layer is formed in the space 156. At this time, the supply amount of compressed air is adjusted by controlling the regulator 146D, and the pressure P of the pressure air layer is set. That is, the pressure P (P> W / A) is set so that the pressing force W for pressing the wafer 154 against the polishing pad 116 by the rubber sheet 132 is larger than the pressure obtained by dividing the pressing force W by the wafer area A. Thus, the pressure air layer is formed stably without being crushed by the carrier 124.

Next, the compressed air from the pump 148 is supplied to the air bag 162 via the air supply path 140,
The central portion 132A of the rubber sheet 132 is elastically deformed by internal air pressure to press the carrier 124, and the wafer 154 is pressed against the polishing pad 116 via the pressure air layer. Then, the air pressure is adjusted by the regulator 146A to control the internal air pressure to a desired pressure, and the pressing force of the wafer 154 against the polishing pad 116 is kept constant.

At the same time, the compressed air from the pump 148 is supplied to the air bag 1 through the air supply path 144.
64, and the outer peripheral portion 132C of the rubber sheet 132 is elastically deformed by the internal air pressure to form the polishing surface adjusting ring 128.
Is pressed, and the lower surfaces of the polishing surface adjustment ring 128 and the retainer ring 130 are pressed against the polishing pad 116. Then, the compressed air from the pump 148 is supplied to the air bag 166 via the air supply path 142, and the intermediate portion 132B of the rubber sheet 132 is elastically deformed by the internal air pressure to press the pressing member 136. The lower surface 137 is pressed against the polishing pad 116. Thereafter, the polishing platen 112 and the wafer holding head 114 are rotated to start polishing the wafer 154.

The polishing amount of the wafer 154 during this polishing is determined by the fact that the contact 174 of the differential transformer 134
Since it is in direct contact with the back surface 154 </ b> A of the core 54, the calculation is performed by the arithmetic unit based on the descending amount of the contact 174, that is, the descending amount of the core 170. When the polishing amount calculated by the arithmetic unit reaches a preset polishing end point, the wafer polishing apparatus is stopped and the wafer 15 is stopped.
The polishing of No. 4 is completed. Thereby, one wafer 15
When the polishing of No. 4 is completed and the second and subsequent wafers 154 are polished, the above-described steps are repeated.

As described above, according to the wafer holding head 114 of the second embodiment, the differential transformer 134 is provided on the pressing member 136 pressed together with the wafer 154, and the contact 174 of the differential transformer 134 is attached to the wafer 154. Since the polishing amount of the wafer 154 is directly detected by contacting the back surface 154A of the wafer 154, the polishing end point of the wafer 154 can be accurately detected.

Further, according to the wafer holding head 114, since the pressing member 136 is disposed outside the retainer ring 130, the wafer 154 being polished does not collide with the pressing member 136. Therefore, according to the wafer holding head 114, the vibration of the pressing member 136 due to the collision of the wafer can be prevented, so that the polishing amount of the wafer can be more accurately detected.

The leg 136D of the pressing member 136 to which the bobbin 172 is attached is formed using an amber having a very small coefficient of thermal expansion as a base material in order to prevent thermal expansion due to polishing processing heat. Since the lower surface 137 pressed by 116 is coated with diamond so that the polishing pad 16 is not polished, the bobbin 172 does not fluctuate from the reference position (zero position). That is, since the differential transformer 134 detects the polishing amount of the wafer 154 based on the surface of the polishing cloth 116, the polishing amount of the wafer 154 can be accurately calculated only by detecting the descending amount of the core 170. . On the other hand, in the conventional apparatus for detecting the polishing amount of the wafer based on the main body of the wafer polishing apparatus, the main body thermally expands, so that the polishing amount of the wafer cannot be accurately detected.

The lower surface 137 of the pressing member 136 is flattened by the polishing surface adjusting ring 128.
16, the pressing member 136 is attached to the polishing cloth 11.
6 does not vibrate vertically. Thus, according to the differential transformer 134, the polishing amount of the wafer 154 can be detected more accurately. In the present embodiment, the differential transformer 134 is applied as the polishing amount detecting means of the wafer 154. However, the present invention is not limited to this, and the polishing amount of the wafer 154 is detected by directly contacting the back surface 154A of the wafer 154. Any means can be applied.

FIG. 9 shows a third example of the wafer holding head 214.
FIG. 9 is a longitudinal sectional view showing the embodiment of FIG.
The same or similar members as those of the wafer holding head 114 according to the embodiment are denoted by the same reference numerals, and description thereof will be omitted. The difference between the wafer holding head 214 in FIG. 9 and the wafer holding head 114 in FIG. 8 will be described.

The first difference is the structure of the differential transformer for detecting the polishing amount of the wafer 154. The differential transformer 134 of the wafer holding head 114 of FIG.
9, the differential transformer 234 of the wafer holding head 214 in FIG. 9 has the contact 274 in contact with the carrier 124. Thus, the contact 274 is moved to the carrier 124.
, The amount of polishing of the wafer 154 can be accurately detected. That is, the thickness of the pressure air layer in the space 156 hardly fluctuates.

Also, the differential transformer 234 detects the polishing amount of the wafer 154 based on the polishing pad 116 similarly to the differential transformer 134,
4 can accurately detect the polishing amount. Note that FIG.
Above, reference numeral 270 is a core, and reference numeral 272 is a bobbin. Next, the second difference is the function of the porous plate.
The porous plate 150 of the wafer holding head 114 in FIG.
While having both functions of wafer suction and air blowing, the porous plate 250 of the wafer holding head 214 shown in FIG.
Has only a wafer suction function. And FIG.
In the wafer holding head 214, a plurality of air blowing holes 278 and 278 are formed on the lower surface of the carrier 124 so as to surround the porous plate 250. These air outlets 278 and 278 are connected to an air pump 148 via a regulator 146D. Further, the porous plate 250 is connected to a suction pump 276.

Therefore, the wafer holding head 2 shown in FIG.
According to 14, if the suction pump 276 is driven,
The wafer 154 can be suction-held by the porous plate 250, and the air pump 148 is driven to drive the air blowing holes 278,
If air is blown out from 278, a pressure air layer can be formed in space 156. FIG. 10 is a longitudinal sectional view showing a fourth embodiment of the wafer holding head 314, and the wafer holding head 21 of the third embodiment shown in FIG.
The same or similar members as in FIG. 4 are denoted by the same reference numerals and description thereof is omitted.

The difference between the wafer holding head 314 in FIG. 10 and the wafer holding head 214 in FIG. 9 is the structure of the pressing member. The pressing member 136 of the wafer holding head 214 in FIG. 9 forms a head portion 136 </ b> B on the pressing member 136, and presses the head portion 136 </ b> B with the airbag 166 to press the lower surface 137 of the pressing member 136 against the polishing pad 112. It is configured as follows.

On the other hand, the pressing member 336 of the wafer holding head 314 in FIG. 10 does not form a head portion, and is configured to press the lower surface 337 of the pressing member 336 against the polishing pad 112 by the weight of the pressing member 336. ing. FIG.
When the pressing member 336 is a heavy object,
Alternatively, the present invention can be applied when the polishing cloth 112 is hard and does not require a pressing force. Note that, in FIG.
6A is a main body of the pressing member 336, 336C is a support arm of the pressing member 336, and 336D is a pressing member 3
36 legs.

FIG. 11 is a longitudinal sectional view showing a fifth embodiment of the wafer holding head 414, and the same or similar members as those of the wafer holding head 314 of the fourth embodiment shown in FIG. The same reference numerals are given and the description is omitted. A wafer holding head 414 of FIG.
The difference from the wafer holding head 314 of FIG.
11 is different from the differential transformer 234 in that the wafer holding head 314 of the wafer holding head 314 is the differential transformer 234, whereas the light wave interference device 500 is the wafer polishing amount detecting device of the wafer holding head 414 in FIG.

FIG. 12 is a structural view of the light wave interference device 500. The light wave interference device 500 shown in the figure is an infrared interference device, and includes a light source 502 for generating infrared light, a beam splitter 504, a photodiode 506, and the like. The infrared light 508 generated from the light source 502 is reflected downward by the beam splitter 504 toward the wafer 154. Then, the reflected infrared light 508 is
The light is reflected by the back surface 154 </ b> A of the wafer 154 and the polishing pad 116. Then, the back surface 154 of the wafer 154
The reflected light (reference light) 510 reflected by A is sent to the beam splitter 504. Further, the reflected light 512 reflected by the polishing cloth 112 is sent to the beam splitter 504 and is superimposed on the reflected light 510 to form an interference fringe. This interference fringe is reflected on the photodiode 506.
After that, the number of interference fringes is counted by a counter circuit (not shown). Then, based on the number of the interference fringes, an arithmetic circuit (not shown) detects the displacement of the polishing pad 112, that is, the polishing amount of the wafer 154.

[0073] Wafer holding head 414 of the present embodiment.
, A light wave interference device 5 as a wafer polishing amount detection device
Even if 00 is applied, the polishing amount of the wafer 154 can be accurately detected. This light wave interference device 500 has a first
-Wafer holding heads 14 and 11 of the fourth embodiment
4, 214, 314. In the present embodiment, an infrared interference device is illustrated as the light wave interference device 500, but a laser interference device may be used instead. Further, the light wave interference device 500 of the present embodiment
In the above, the reflected light 510 reflected on the back surface 154A of the wafer 154 is used as the reference light, but the reflected light reflected on the non-polished surface 514A of the silicon oxide film 514 may be used as the reference light.

[0074]

As described above, according to the wafer polishing apparatus of the present invention, the polishing surface adjusting ring which is pressed against the polishing pad together with the wafer is provided, and the amount of carrier fluctuation with respect to the polishing surface adjusting ring on the central axis of the wafer. Is detected by the detector, so that the polishing amount of the wafer is detected, so that the polishing end point of the wafer can be accurately detected.

According to the present invention, there is provided a pressing member pressed against the polishing pad together with the wafer, and the relative displacement between the back surface of the wafer and the pressing member at the center position of the wafer or the carrier and the pressing member at the center position of the wafer. Since the amount of polishing of the wafer is detected by detecting the relative displacement with respect to the member by the detector, the end point of the polishing of the wafer can be detected more accurately.

Further, according to the present invention, the polished amount of the wafer detected by the polished amount detecting means is compared with the model polished amount stored in the storage means. Since the dressing time and the replacement time of the polishing pad were determined and the determined content was displayed on the display device,
The dressing time and replacement time of the polishing cloth can be automatically determined during normal polishing.

[Brief description of the drawings]

FIG. 1 is an overall structural diagram of a wafer polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a first embodiment of a wafer holding head applied to the wafer polishing apparatus of FIG. 1;

FIG. 3 is a block diagram showing a control system of the wafer polishing apparatus of FIG. 1;

FIG. 4 is a graph comparing a model polishing amount and an actual polishing amount.

FIG. 5 is a diagram for explaining a pressure applied to a wafer from a polishing cloth.

FIG. 6 is a graph showing a relationship between a polishing amount and a polishing pressure according to a polishing time.

FIG. 7 is a plan view showing a second embodiment of the wafer holding head.

8 is a longitudinal sectional view of the wafer holding head taken along line 8-8 in FIG. 7;

FIG. 9 is a longitudinal sectional view showing a third embodiment of the wafer holding head.

FIG. 10 is a longitudinal sectional view showing a fourth embodiment of the wafer holding head.

FIG. 11 is a longitudinal sectional view showing a fifth embodiment of the wafer holding head.

FIG. 12 is a structural diagram of an infrared interference device provided in the wafer holding head of FIG. 11;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Wafer polishing apparatus 12 ... Polishing surface plate 14, 114, 214, 314, 414 ... Wafer holding head 16, 116 ... Polishing cloth 50, 154 ... Wafer 70, 72 ... Sensor 74 ... CPU 80 ... External input device 82 ... Display Device 84: RAM 136: Pressing member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Manabu Sato 9-7-1, Shimorenjaku, Mitaka-shi, Tokyo, Japan Tokyo Seimitsu Co., Ltd. (56) References JP-A-3-170265 (JP, A) JP-A Heihei 8-39424 (JP, A) JP-A-9-290363 (JP, A) JP-A-10-106981 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24B 37/04 B24B 37/00 H01L 21/304

Claims (4)

(57) [Claims] A polishing plate provided on a surface thereof, the polishing platen rotating the polishing cloth, and a wafer holding head rotating while holding a wafer and pressing the surface of the wafer against the polishing cloth; A wafer holding head includes a carrier that holds the wafer and contacts the polishing cloth at a predetermined pressure, and a polishing surface adjustment ring provided around the wafer so as to contact the polishing cloth at a predetermined pressure. A wafer polishing apparatus, comprising: a detector that detects a variation amount of the carrier with respect to the polishing surface adjustment ring on a central axis of the wafer with a single detector. 2. A polishing table provided with a polishing cloth on a surface thereof, the polishing platen rotating the polishing cloth, and a wafer holding head rotating while holding a wafer and pressing the surface of the wafer against the polishing cloth, The wafer holding head includes a carrier that holds the wafer and contacts the polishing cloth at a predetermined pressure, and a polishing surface adjustment ring provided around the wafer so as to contact the polishing cloth at a predetermined pressure. In the wafer polishing apparatus, a pressing member provided between the polishing surface adjustment ring and the carrier, and having a plurality of surfaces or cylindrical end surfaces that are in contact with the polishing cloth at a predetermined pressure, A wafer polishing apparatus comprising: a detector for detecting a relative displacement between a back surface of the wafer and the pressing member on a center position with a single detector. Location. 3. A polishing table provided with a polishing cloth on a surface thereof, the polishing table rotating the polishing cloth, and a wafer holding head rotating while holding a wafer and pressing the surface of the wafer against the polishing cloth; The wafer holding head includes a carrier that holds the wafer and contacts the polishing cloth at a predetermined pressure, and a polishing surface adjustment ring provided around the wafer so as to contact the polishing cloth at a predetermined pressure. In the wafer polishing apparatus, a pressing member provided between the polishing surface adjustment ring and the carrier, and having a plurality of surfaces or cylindrical end surfaces that are in contact with the polishing cloth at a predetermined pressure, A wafer polishing apparatus, comprising: a detector for detecting a relative displacement between the carrier and the pressing member at a center position with a single detector. 4. Pressing the wafer against a rotating polishing cloth,
In a wafer polishing apparatus for polishing a surface of a wafer, a polishing amount detecting means for detecting a polishing amount of the wafer, a storing means in which a model polishing amount of the wafer according to a polishing time is stored, and a detection by the polishing amount detecting means Polishing amount of the wafer
A control unit that compares the model polishing amount stored in the storage unit with a dressing time of the polishing pad or a replacement time of the polishing pad based on the difference in the polishing amount, and outputs a content of the determination; Display means for displaying the content of the judgment output from the means.