Polishing apparatus and method for detecting the end point of polishing in the polishing apparatus

Abstract

To accurately detect a polishing end point.SOLUTION: A polishing device includes: a polishing table for holding a polishing pad; a holding part for holding a polishing object so as to be opposite to the polishing pad; at least one of a motor for driving and rotating the polishing table, a motor for rotating the holding part holding the polishing object, and a motor for swinging the holding part holding the polishing object; a driver which is one or a plurality of drivers structured to supply a drive current to at least the one motor and is structured to further output a digital signal according to a load of at least the one motor; and an end point detection part which detects a polishing end point indicating end of polishing of the polishing object according to the digital signal output from the driver.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a polishing apparatus and a method for detecting a polishing end point in the polishing apparatus.

Background Art

[0002] One of the manufacturing apparatuses for semiconductor devices is a CMP (Chemical Mechanical Polishing) apparatus. A typical CMP apparatus includes a polishing table to which a polishing pad is attached and a polishing head to which a substrate to be polished is attached. In a typical CMP apparatus, a polishing liquid is supplied to the polishing pad, and at least one of the polishing table and the polishing head is rotated while the polishing pad and the substrate are in contact with each other, so that the substrate is polished.

[0003] In the polishing process of a polishing apparatus such as a CMP apparatus, it is important to accurately detect the polishing end point at which the film to be removed by polishing has been removed. As a method for detecting the polishing end point, a method of detecting a change in the polishing frictional force when the material on the surface of the object to be polished changes to a different material by polishing is known (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, the drive current supplied to the motor that rotates the polishing table, etc., is measured by a current sensor in order to detect changes in polishing friction force. Therefore, if noise is mixed into the measured signal, or due to errors caused by the accuracy of the current sensor itself, the accuracy of detecting the polishing endpoint may decrease. In Patent Document 2, an analog current command value is output from the driver that supplies drive current to the motor and this is used to determine the polishing endpoint, but this command value signal needs to be processed by AD conversion, amplification, rectification, etc. Furthermore, the analog signal from the driver before AD conversion is susceptible to noise, and by amplifying and rectifying the signal, there is a possibility that information necessary for detecting the polishing endpoint (minute changes in the signal) may be lost from the signal. Moreover, in both configurations of cited documents 1 and 2, it is difficult to synchronize the signals obtained from multiple motors (or drivers), so it was not possible to detect the polishing endpoint using multiple types of signals. [Means for solving the problem]

[0006] [Embodiment 1] According to Embodiment 1, a polishing apparatus is provided comprising: a polishing table for holding a polishing pad; a holding unit for holding an object to be polished so as to face the polishing pad; at least one motor selected from a motor for rotationally driving the polishing table, a motor for rotating the holding unit holding the object to be polished, and a motor for oscillating the holding unit holding the object to be polished; one or more drivers configured to supply drive current to the at least one motor, and further configured to output a digital signal corresponding to the load of the at least one motor; and an endpoint detection unit that detects a polishing endpoint indicating the end of polishing of the object to be polished based on the digital signal output from the driver.

[0007] [Form 2] According to Form 2, in the polishing apparatus of Form 1, the digital signal corresponding to the load of the at least one motor is the rotational speed or rotation of the at least one motor. This is a signal indicating an angle.

[0008] [Embodiment 3] According to Embodiment 3, in the polishing apparatus of Embodiment 1, the driver is configured to control the drive current based on the rotational speed or rotational angle of the at least one motor, and the digital signal corresponding to the load of the at least one motor is a digital signal representing a command value for generating the drive current based on the rotational speed or rotational angle of the at least one motor.

[0009] [Embodiment 4] According to Embodiment 4, in the polishing apparatus of Embodiment 1, the digital signal corresponding to the load of the at least one motor is both a signal indicating the rotational speed or rotational angle of the at least one motor and a digital signal representing a command value for generating the drive current, and the endpoint detection unit is configured to detect the polishing endpoint indicating the end of polishing of the object to be polished based on both of the digital signals.

[0010] [Embodiment 5] According to Embodiment 5, in the polishing apparatus of Embodiment 4, the endpoint detection unit is configured to determine that the polishing endpoint has been reached when both of the digital signals show a predetermined change.

[0011] [Embodiment 6] According to embodiment 6, the polishing apparatus of any one of embodiments 2 to 5 is further provided with an encoder for detecting the rotational speed or rotational angle of the at least one motor.

[0012] [Embodiment 7] According to Embodiment 7, in any one of Embodiments 1 to 6, the endpoint detection unit is configured to detect the polishing endpoint indicating the end of polishing of the object to be polished based on a plurality of digital signals output from a plurality of drivers.

[0013] [Embodiment 8] According to Embodiment 8, in the polishing apparatus of Embodiment 7, the endpoint detection unit is configured to determine that the polishing endpoint has been reached when the multiple digital signals output from the multiple drivers each show a predetermined change.

[0014] [Embodiment 9] According to Embodiment 9, a method is provided for detecting a polishing endpoint indicating the end of polishing in a polishing apparatus, wherein the polishing apparatus comprises a polishing table for holding a polishing pad, a holding unit for holding an object to be polished facing the polishing pad, at least one motor from among a motor for rotationally driving the polishing table, a motor for rotating the holding unit holding the object to be polished, and a motor for oscillating the holding unit holding the object to be polished, one or more drivers, and an endpoint detection unit, and the method is provided comprising the steps of: the driver supplying a drive current to the at least one motor; the driver further outputting a digital signal corresponding to the load of the at least one motor; and the endpoint detection unit detecting a polishing endpoint indicating the end of polishing the object to be polished based on the digital signal output from the driver. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram showing the overall configuration of a polishing apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the overall configuration of a polishing apparatus according to one embodiment of the present invention. [Figure 3] This is a block diagram showing the components related to motor control and polishing endpoint detection in a polishing apparatus according to one embodiment of the present invention. [Figure 4] This flowchart shows an example of the polishing endpoint detection process in the endpoint detection unit of a polishing apparatus according to one embodiment of the present invention. [Figure 5] This flowchart shows an example of the polishing endpoint detection process in the endpoint detection unit of a polishing apparatus according to one embodiment of the present invention. [Figure 6] This flowchart shows an example of the polishing endpoint detection process in the endpoint detection unit of a polishing apparatus according to one embodiment of the present invention. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted.

[0017] FIG. 1 and FIG. 2 are schematic views showing the overall configuration of a polishing apparatus 10 according to an embodiment of the present invention. As shown, the polishing apparatus 10 includes a polishing table 30 for holding a polishing pad 31, a top ring 40 (holding portion) for holding a polishing object (e.g., a substrate 100 such as a semiconductor wafer shown in FIG. 2) so as to face the polishing pad 31 and pressing it against the polishing surface of the polishing pad 31, a table drive motor 33 for rotating the polishing table 30, a top ring drive motor 43 for rotating the top ring 40, a driver 34 for supplying a drive current to the table drive motor 33, and a driver 44 for supplying a drive current to the top ring drive motor 43.

[0018] The polishing table 30 is connected to a table drive motor 33 disposed below it via a table shaft 32. When the table drive motor 33 is rotationally driven, the polishing table 30 can rotate around the axis of the table shaft 32. A polishing pad 31 is attached to the upper surface of the polishing table 30. The surface 311 of the polishing pad 31 constitutes a polishing surface for polishing the substrate 100. A polishing liquid supply nozzle (not shown) is installed above the polishing table 30, and the polishing liquid is supplied from the polishing liquid supply nozzle to the polishing pad 31 on the polishing table 30.

[0019] The top ring 40 is supported by the arm 50 via the top ring shaft 42. The top ring shaft 42 can move up and down with respect to the arm 50 by a vertical movement mechanism (not shown). By the vertical movement of the top ring shaft 42, the top ring 40 can be lifted and lowered with respect to the arm 50 and positioned. The top ring 40 is configured to be able to hold a substrate 100 such as a semiconductor wafer on its lower surface. Specifically, as shown in FIG. 2, the top ring 40 includes a retainer ring 41A that holds the outer peripheral edge of the substrate 100 so that the substrate 100 does not protrude from the top ring 40, and a top ring body 41B that presses the substrate 100 against the polishing surface 311.

[0020] A top ring drive motor 43 is fixed to the arm 50 that supports the top ring 40. Also, as shown in FIG. 2, the top ring shaft 42 is connected to a rotating cylinder 61, and a timing pulley 62 provided on the outer peripheral portion of this rotating cylinder 61 is connected via a timing belt 63 to a timing pulley 64 provided on the top ring drive motor 43. Thereby, when the top ring drive motor 43 rotates, the rotating cylinder 61 and the top ring shaft 42 rotate integrally via the timing pulley 64, the timing belt 63, and the timing pulley 62, and the top ring 40 rotates around the axis of the top ring shaft 42.

[0021] The arm 50 is connected to an arm drive motor 53 fixed to the arm shaft 52. A drive current is supplied to the arm drive motor 53 from a driver 54. By driving the arm drive motor 53, the arm 50 and the top ring 40 supported by the arm 50 can swing around the axis of the arm shaft 52.

[0022] When the polishing apparatus 10 operates, first, the substrate 100 conveyed by a transport mechanism (not shown) is received and held by the top ring 40 at a predetermined receiving position. The top ring 40, having received the substrate 100 at the receiving position, is moved from the receiving position to above the polishing table 30 by the rotation of the arm 50. Next, the top ring shaft 42 and the top ring 40 descend, and the substrate 100 is pressed against the polishing surface 311 of the polishing pad 31. The table drive motor 33 and the top ring drive motor 43 rotate, causing the polishing table 30 and the top ring 40 to rotate respectively, and at the same time, polishing fluid is supplied onto the polishing pad 31 from a polishing fluid supply nozzle located above the polishing table 30. As a result, the substrate 100 slides against the polishing surface 311 of the polishing pad 31, and the surface of the substrate 100 is polished. During the polishing of the substrate 100, the arm drive motor 53 may periodically rotate the arm 50 from side to side, causing the top ring 40 to oscillate relative to the polishing pad 31 (i.e., to reciprocate on the polishing pad 31) while polishing is performed.

[0023] The polishing apparatus 10 further includes a control unit 20 for controlling each driver 34, 44, 54, and an endpoint detection unit 25 configured to detect a polishing endpoint indicating the end of polishing based on signals indicating the polishing status provided by each driver 34, 44, 54.

[0024] Here, the substrate 100 (e.g., a semiconductor wafer), which is the object to be polished, has a laminated structure composed of multiple different materials such as semiconductors, conductors, and insulators, and the coefficient of friction differs between the layers of different materials. Therefore, as polishing progresses from one layer of the laminated structure to another layer of different materials, a change occurs in the polishing friction force when polishing the object to be polished. The polishing friction force appears as the driving load of each motor 33, 43, 53 that rotates or oscillates the polishing table 30 or top ring 40. Consequently, the current flowing through each motor 33, 43, 53 and the rotational speed of each motor 33, 43, 53 change according to the polishing friction force, that is, according to the material of the surface being polished, and this can be used to detect the end point of polishing. Detection of the polishing end point can be based on either the driving current or the rotational speed of each motor 33, 43, 53, or on both.

[0025] The control unit 20 and the endpoint detection unit 25 may be configured as a computer equipped with a processor and memory, for example. The memory may store a program (software) containing one or more computer executable instructions, and the processor may read this program from the memory and execute it to perform the processing that realizes the respective functions of the control unit 20 and the endpoint detection unit 25. For example, the endpoint detection unit 25 may acquire signals from each driver 34, 44, 54 indicating the motor drive current and / or signals indicating the rotation state of the motor, perform calculations (data processing) on ​​these signals to identify changes in polishing friction force, and operate to detect the polishing endpoint based on the identification result.

[0026] Figure 3 is a block diagram showing the components involved in motor control and polishing endpoint detection in the polishing apparatus 10. Each driver 34, 44, and 54 includes a current command value generation unit 102, a current generation circuit 104, a rotation speed acquisition unit 106, and a signal output unit 108. Each driver 34, 44, and 54 has the same configuration, and Figure 3 shows only one of the systems consisting of a driver and the motor connected to that driver, omitting the other two systems. The operation related to driver 34 will be described below, but the same applies to drivers 44 and 54.

[0027] The control unit 20 outputs a rotation speed command value 202 for the table drive motor 33 to the driver 34. The rotation speed command value 202 is data that indicates the rotation speed (also called rotational velocity) of the table drive motor 33, that is, the amount of rotation of the table drive motor 33 per unit time. An encoder 200 is attached to the table drive motor 33. The encoder 200 is a sensor that detects the rotation of the table drive motor 33 and outputs a signal 208 corresponding to the rotation speed as the table drive motor 33 rotates. For example, the encoder 200 outputs a pulse signal each time the table drive motor 33 rotates by a predetermined angle (for example, 8 times during one rotation). The device may be configured to output the following. The rotation speed acquisition unit 106 obtains a measured value of the rotation speed of the table drive motor 33 based on the signal 208 from the encoder 200 (for example, by counting the number of pulse signals received per unit time), and outputs data 210 indicating this measured value.

[0028] The rotational speed command value data 202 from the control unit 20 and the rotational speed measurement value data 210 from the rotational speed acquisition unit 106 are input to the current command value generation unit 102. The current command value generation unit 102 generates a current command value 204 of the drive current to be supplied to the table drive motor 33 based on the deviation between the rotational speed command value 202 and the rotational speed measurement value 210. For example, the current command value generation unit 102 may be configured to determine the next new current command value 204 by adjusting the previous current command value 204 by an amount corresponding to the deviation between the rotational speed command value 202 and the rotational speed measurement value 210. The generated current command value data 204 is input to the current generation circuit 104, and the current generation circuit 104 generates a drive current 206 to the table drive motor 33 according to this current command value 204 and supplies it to the table drive motor 33. The current generation circuit 104 may be configured to generate a drive current 206 by pulse width modulation (PWM) with a duty cycle corresponding to the current command value 204, for example.

[0029] In the polishing apparatus 10 of this embodiment, the signal output unit 108 acquires current command value data 204 from the current command value generation unit 102 and rotation speed measurement value data 210 from the rotation speed acquisition unit 106, and provides these acquired data 204 and 210 to the control unit 20. The current command value data 204 output from the current command value generation unit 102 and the rotation speed measurement value data 210 output from the rotation speed acquisition unit 106 are digital data. Therefore, the control unit 20 can obtain the current command value 204 and the rotation speed measurement value 210 from the driver 34 in the form of digital data.

[0030] The current command value data 204 and rotational speed measurement value data 210 from the driver 34 are temporarily stored in the data storage unit 22 within the control unit 20. The data storage unit 22 may be a separate storage device located outside the control unit 20. The endpoint detection unit 25 retrieves the current command value data 204 and / or rotational speed measurement value data 210 from the data storage unit 22 and detects the end point of polishing based on the retrieved data. For example, the current command value data 204 and rotational speed measurement value data 210 may be output from the driver 34 every 1 ms (milliseconds) and temporarily stored in the data storage unit 22, and the endpoint detection unit 25 may retrieve the data from the data storage unit 22 in batches at predetermined time intervals (for example, retrieving 30 ms worth of data every 30 ms) to detect the end point of polishing. The sampling period for outputting the current command value data 204 and rotational speed measurement value data 210 from the driver 34 is preferably 1 ms or less. By having a sampling period of 1 ms or less, the continuous changes in the state of the motor 33 (rotation speed and current) can be reproduced with high accuracy, and the changes contained in data 204 and 210 can be determined in the shortest possible time. Furthermore, even when filtering such as moving averages is used in combination, the time required to detect the endpoint can be shortened.

[0031] The current command value data 204 used by the endpoint detection unit 25 to detect the end point of polishing is data generated internally in the driver 34 as a command value for the table drive motor 33. Therefore, the end point of polishing can be detected without using a sensor to measure the actual drive current 206 supplied from the driver 34 to the table drive motor 33. Furthermore, since the current command value data 204 and the rotation speed measurement value data 210 output from the driver 34 are digital data and are time-synchronized, it is possible to detect the end point of polishing using both the current command value data 204 and the rotation speed measurement value data 210 without any special processing (for example, processing to synchronize the timing of the current command value and the rotation speed measurement value).

[0032] Figure 4 is a flowchart showing an example of the polishing endpoint detection process in the endpoint detection unit 25. In step 402, the endpoint detection unit 25 retrieves current command value data 204 or rotation speed measurement value data 210 from the data storage unit 22. In step 404, the endpoint detection unit 25 calculates the amount of change in the current command value over time or the amount of change in the rotation speed measurement value over time, and determines whether the absolute value of this change is greater than a predetermined threshold. As described above, as polishing progresses, the material of the surface of the object to be polished (i.e., the substrate 100) changes, which changes the polishing friction force, and the motor's rotation speed and drive current also change. In step 406, if the absolute value of the calculated change is greater than the threshold, the endpoint detection unit 25 determines that the object being polished has reached the end point of polishing.

[0033] The criteria for determining when the polishing endpoint has been reached are not limited to those described above. For example, in step 404, the endpoint detection unit 25 may calculate the amount of change in the current command value and the rotational speed measurement value after averaging them with respect to time. Alternatively, in steps 404 and 406, the endpoint detection unit 25 may calculate the differential value of the current command value and the rotational speed measurement value with respect to time and determine when the polishing endpoint has been reached based on the change in this differential value.

[0034] Alternatively, the driver 34 may output data indicating the rotation angle of the motor 33 to the control unit 20 instead of data 210 regarding the rotation speed (rotational velocity) of the motor 33, and the endpoint detection unit 25 may determine the polishing endpoint based on this motor rotation angle data. The data indicating the rotation angle of the motor 33 can be obtained, for example, based on the reception time of the pulse signal output from the encoder 200.

[0035] When the polishing endpoint is reached, the endpoint detection unit 25 decides in step 408 to terminate the polishing of the object being polished. Upon receiving the decision to terminate polishing, the polishing table 30 and the top ring 40 stop rotating, the top ring 40 rises from the polishing table 30, and the substrate 100 is removed from the top ring 40 and passed on to the next process (e.g., the cleaning process). On the other hand, if the polishing endpoint has not yet been reached, the endpoint detection unit 25 returns to step 402 to continue detecting the polishing endpoint and repeats the steps from step 402 onward using the new time data.

[0036] Figure 5 is a flowchart showing another example of the polishing endpoint detection process in the endpoint detection unit 25. In this example, the endpoint detection unit 25 determines the polishing endpoint based on both the current command value and the rotational speed measurement value.

[0037] In step 502, the endpoint detection unit 25 retrieves the current command value data 204 and the rotational speed measurement value data 210 from the data storage unit 22. In step 504, the endpoint detection unit 25 calculates the amount of change in the current command value over time and determines whether the absolute value of this change is greater than a predetermined first threshold. If the absolute value of the change is greater than the first threshold, the process proceeds to step 506; if the absolute value of the change is less than the first threshold, the process returns to step 502. In step 506, the endpoint detection unit 25 further calculates the amount of change in the rotational speed measurement value over time and determines whether the absolute value of this change is greater than a predetermined second threshold. If the absolute value of the change is greater than the second threshold, in step 508, the endpoint detection unit 25 determines that the polishing endpoint has been reached.

[0038] As shown above, the polishing endpoint detection method in the example of Figure 5 allows for more accurate detection of the polishing endpoint by using both the current command value and the rotational speed measurement value as criteria for determining when the polishing endpoint is reached. Here, since the current command value data 204 and the rotational speed measurement value data 210 output from the driver 34 are digital data and are time-synchronized, polishing endpoint detection can be performed using both the current command value data 204 and the rotational speed measurement value data 210 without any special processing (for example, processing to synchronize the timing of the current command value and the rotational speed measurement value).

[0039] Figure 6 is a flowchart showing yet another example of the polishing endpoint detection process in the endpoint detection unit 25. In this example, the endpoint detection unit 25 determines the polishing endpoint based on data acquired from multiple drivers.

[0040] In step 602, the endpoint detection unit 25 retrieves from the data storage unit 22 the current command value data and rotational speed measurement data provided by the driver 34 (i.e., for the table drive motor 33) and the current command value data and rotational speed measurement data provided by the driver 44 (i.e., for the top ring drive motor 43). In step 604, the endpoint detection unit 25 calculates the amount of change over time of the current command value and / or rotational speed measurement value for the table drive motor 33 and determines whether the absolute value of this change is greater than a predetermined first threshold. If the absolute value of the change is greater than the first threshold, the process proceeds to step 606; if the absolute value of the change is less than the first threshold, the process returns to step 602. In step 606, the endpoint detection unit 25 further calculates the amount of change over time of the current command value and / or rotational speed measurement value for the top ring drive motor 43 and determines whether the absolute value of this change is greater than a predetermined second threshold. If the absolute value of the change is greater than the second threshold, in step 608, the endpoint detection unit 25 determines that the polishing endpoint has been reached.

[0041] As shown above, the polishing endpoint detection method in the example in Figure 6 allows for more accurate detection of the polishing endpoint by using data acquired from multiple drivers as the criteria for determining when the polishing endpoint has been reached. Since the data from each driver is digital data and is temporally synchronized, polishing endpoint detection using data from multiple drivers can be performed without any special processing (for example, processing to synchronize the timing of data from one driver with that of another). Although the flowchart in Figure 6 uses only data from two drivers, 34 and 44, it is of course possible to also use data from driver 54 to determine the polishing endpoint.

[0042] While embodiments of the present invention have been described above based on several examples, the embodiments described above are intended to facilitate understanding of the present invention and do not limit it. The present invention can be modified and improved without departing from its spirit, and of course, its equivalents are included. Furthermore, any combination or omission of the components described in the claims and specification is possible to the extent that at least some of the above-mentioned problems can be solved or at least some of the effects can be achieved. [Explanation of Symbols]

[0043] 10 Polishing equipment 20 Control Unit 22 Data Storage Unit 25. End point detection unit 30 polishing tables 31 polishing pads 311 Polished surface 32 Table Shaft 33 Table drive motor 34 drivers 40 Top Ring 41A Retainer Ring 41B Top Ring Body 42 Top Ring Shaft 43 Top ring drive motor 44 drivers 50 Arm 52 Arm Shaft 53 Arm drive motor 54 drivers 61 Rotating Cylinder 62 Timing Pulley 63 Timing belt 64 Timing Pulley 100 circuit boards 102 Current command value generation unit 104 Current generation circuit 106 Rotation speed acquisition unit 108 Signal Output Section 200 encoders

Claims

1. A polishing table for holding the polishing pad, A holding part for holding the object to be polished, facing the polishing pad, At least one of the following motors: a motor for rotating the polishing table, a motor for rotating the holding part that holds the object to be polished, and a motor for oscillating the holding part that holds the object to be polished. One or more drivers configured to supply drive current to at least one motor, and further configured to output a digital signal corresponding to the load of the at least one motor, An endpoint detection unit detects the end point of polishing, which indicates the end of polishing of the object to be polished, based on the digital signal output from the driver. Equipped with, The digital signal corresponding to the load of the at least one motor is a signal indicating the rotational speed or rotational angle of the at least one motor, and a digital signal representing a command value for generating the drive current. The endpoint detection unit is configured to detect the polishing endpoint, which indicates the end of polishing of the object to be polished, based on the amount of change over time between both digital signals. Polishing equipment.

2. The polishing apparatus according to claim 1, wherein the endpoint detection unit is configured to determine that the polishing endpoint has been reached when both of the digital signals show a predetermined change.

3. The polishing apparatus according to claim 1 or 2, further comprising an encoder for detecting the rotational speed or rotational angle of at least one of the motors.

4. The polishing apparatus according to any one of claims 1 to 3, wherein the endpoint detection unit is configured to detect a polishing endpoint indicating the end of polishing of the object to be polished based on a plurality of digital signals output from a plurality of drivers.

5. The polishing apparatus according to claim 4, wherein the endpoint detection unit is configured to determine that the polishing endpoint has been reached when the plurality of digital signals output from the plurality of drivers each show a predetermined change.

6. A method for detecting the end point of polishing in a polishing apparatus, The polishing apparatus is A polishing table for holding the polishing pad, A holding part for holding the object to be polished, facing the polishing pad, At least one of the following motors: a motor for rotating the polishing table, a motor for rotating the holding part that holds the object to be polished, and a motor for oscillating the holding part that holds the object to be polished. One or more drivers, End point detection unit, Equipped with, The aforementioned method, The driver supplies drive current to at least one motor, The driver further outputs a digital signal corresponding to the load of the at least one motor, wherein the digital signal corresponding to the load of the at least one motor includes both a signal indicating the rotational speed or rotational angle of the at least one motor and a digital signal representing a command value for generating the drive current. The endpoint detection unit detects the polishing endpoint indicating the end of polishing of the object to be polished based on the amount of change over time of both digital signals output from the driver, Methods that include...

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