Grinding device and grinding method

Abstract

The present invention is a polishing apparatus and a polishing method for detecting a change in friction between a wafer and a polishing pad when a swing arm is swung with improved accuracy compared to the past, to improve the accuracy of polishing endpoint detection. A polishing apparatus (34) for polishing between a polishing pad (10) and a semiconductor wafer disposed opposite the polishing pad has a polishing table (30) for holding the polishing pad, a top ring (31) for holding the semiconductor wafer, a swing arm (110) for holding the top ring, and a swing shaft motor for swinging the swing arm. The polishing apparatus further has an arm torque detection section (26) for detecting an arm torque (26a) applied to the swing arm when the swing arm is swung through a prescribed angular range, and an endpoint detection section (28) for detecting an endpoint indicating the end of polishing, in accordance with the arm torque detected by the arm torque detection section.

Description

Technical Field

[0001] This invention relates to a grinding apparatus and a grinding method. Background Technology

[0002] In recent years, with the advancement of high integration in semiconductor devices, circuit wiring has become increasingly miniaturized, and the distance between wirings has become narrower. During the manufacturing of semiconductor devices, multiple materials are repeatedly formed in film on a silicon wafer to create a multilayer structure. To form this multilayer structure, the technique of planarizing the wafer surface is crucial. This method of planarizing the wafer surface widely utilizes chemical mechanical polishing (CMP) equipment (also known as chemical mechanical polishing equipment).

[0003] This chemical mechanical polishing (CMP) apparatus generally includes: a polishing table on which a polishing pad for polishing the object to be polished (a substrate such as a wafer); and a top ring for holding the object to be polished and pressing it against the polishing pad. The polishing table and the top ring are each driven to rotate by a drive unit (e.g., a motor). Furthermore, the polishing apparatus includes nozzles for supplying polishing slurry to the polishing pad. Polishing slurry is supplied from the nozzles to the polishing pad, and the wafer is pressed against the polishing pad by the top ring. The wafer is further polished by moving the top ring relative to the polishing table, thus flattening its surface. The top ring and its drive unit are held in two ways: by holding the top ring and its drive unit at the end of a swing arm (single arm); and by holding the top ring and its drive unit on a rotary conveyor belt (carousel).

[0004] If the polishing device does not sufficiently polish the object being polished, insulation between circuits may not be achieved, potentially leading to a short circuit. Furthermore, over-polishing can cause problems such as increased resistance due to reduced wiring cross-sectional area, or complete removal of the wiring itself, preventing the formation of a proper circuit. Therefore, the polishing device must be able to detect the optimal polishing endpoint.

[0005] As a method for detecting the end point of grinding, there are known methods for detecting changes in grinding friction as the grinding process transfers to different materials. The semiconductor wafer being ground has a layered structure composed of different materials such as semiconductors, conductors, and insulators, and the coefficients of friction between these different material layers are different. Therefore, the method involves detecting changes in grinding friction as the grinding process transfers to different material layers. Using this method, the grinding endpoint is defined as the point where the grinding reaches the next different material layer.

[0006] In addition, the grinding device can also detect the grinding endpoint by detecting the change in grinding friction when the grinding surface of the object being ground changes from an uneven state to a flat state.

[0007] Here, the grinding friction generated when grinding the object is represented as the driving load of the drive unit of the rotary grinding table or top ring. For example, if the drive unit is an electric motor, the driving load (torque) can be measured as the current flowing into the motor. Therefore, the motor current (torque current) can be detected by a current sensor, and the grinding endpoint can be detected based on the detected change in the motor current.

[0008] Japanese Patent Application Publication No. 2004-249458 discloses a method for detecting the grinding endpoint by measuring the grinding friction force using the motor current of a motor driving a grinding table, in a method of holding a top ring at the end of a swing arm. In a method of holding multiple top rings on a rotary conveyor belt, there is an endpoint detection method by detecting the torque current (motor current) of the rotary conveyor belt's rotating motor (Japanese Patent Application Publication No. 2001-252866, US Patent No. 6293845). Furthermore, there is a method of driving the top rings in the lateral direction using a linear motor mounted on the rotary conveyor belt. This method discloses an endpoint detection method by detecting the torque current (motor current) of the linear motor (US Patent Application Publication No. 2014 / 0020830).

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2004-249458

[0012] Patent Document 2: Japanese Patent Application Publication No. 2001-252866

[0013] Patent Document 3: US Patent No. 6,293,845

[0014] Patent Document 4: U.S. Patent Application Publication No. 2014 / 0020830

[0015] (The problem the invention aims to solve)

[0016] In a polishing process executed by a polishing apparatus, various polishing conditions exist depending on the combination of factors such as the type of object being polished, the type of polishing pad, the type of polishing slurry (slurry), and whether or not a oscillating arm is used. For example, during polishing, the oscillating arm is used to oscillate for the purpose of improving the uniformity (profile) of the polishing. In this case, when the polishing friction force is measured using the motor current of the motor driving the polishing table (rotary motor), the distance between the rotation center of the polishing table and the rotation center of the wafer changes due to the oscillation of the oscillating arm. Therefore, the change in the rotational torque of the polishing table causes the change in the oscillation period of the oscillating arm to manifest as the motor current of the rotary motor. As a result, it becomes difficult to detect the polishing endpoint from the motor current of the rotary motor.

[0017] There is also a method that detects the arm torque applied to the swing arm based on the current value of the motor (swing motor) used to swing the swing arm, and then uses the detected arm torque to detect the grinding endpoint indicating the end of grinding (hereinafter referred to as the "arm torque method"). In the arm torque method, the arm torque changes due to the rotation of the swing motor when the swing arm swings. In the arm torque method, compared with the torque used to rotate the swing motor when the swing arm swings, the change in torque caused by the change in the grinding friction between the wafer and the grinding pad is small. Therefore, if the influence of the torque used to rotate the swing motor is not eliminated, the torque change cannot be detected, and the grinding endpoint may not be properly detected, resulting in problems such as over-grinding. That is, it is advisable to accurately detect the change in arm torque to achieve higher accuracy in detecting the film change of the grinding object and / or the grinding endpoint compared to the past.

[0018] In addition, it is necessary to properly check the grinding endpoint when grinding and dressing the grinding pad are performed simultaneously. Dressing is done by pressing a pad dresser, on which abrasive stones such as diamonds are placed, against the grinding pad. The pad dresser cuts or roughens the surface of the grinding pad, ensuring good retention of the grinding pad slurry before grinding begins, or restoring the retention of the grinding pad slurry during use, in order to maintain grinding capability. Summary of the Invention

[0019] Therefore, one objective of this invention is to detect, with improved accuracy than in the past, the change in friction between the wafer and the polishing pad, i.e., the change in arm torque, when the top ring is held in the swing arm and the swing arm swings, thereby improving the accuracy of polishing end point detection.

[0020] (Solutions)

[0021] To address the aforementioned problems, a first approach employs a grinding device structure for grinding between a grinding pad and a grinding object, the grinding object being disposed opposite to the grinding pad. This grinding device is characterized by comprising: a grinding table for holding the grinding pad; a holding portion for holding the grinding object; a swing arm for holding the holding portion; an arm drive portion for swinging the swing arm; an arm torque detection portion for directly or indirectly detecting the arm torque applied to the swing arm when the swing arm swings within a specified angle range; and an endpoint detection portion for detecting a grinding endpoint indicating the end of the grinding process based on the arm torque detected by the arm torque detection portion.

[0022] The second method adopts the structure of the grinding device of the first method, characterized in that when the swing arm swings in a specified direction, the arm torque detection unit detects the arm torque within the specified angle range.

[0023] The third method adopts the structure of the grinding device of the first method, characterized in that, when the swing arm swings in two directions, the arm torque detection unit detects the arm torque within the specified angle range.

[0024] The fourth method adopts the structure of a grinding device from the first to the third method, characterized in that the arm torque detection unit detects the arm torque at a specified angle within the specified angle range.

[0025] The fifth method adopts the structure of a grinding device of any one of the first to third methods, characterized in that the arm torque detection unit detects the arm torque at multiple angles within the specified angle range, and for at least one cycle of oscillation, the endpoint detection unit averages the arm torque obtained at the multiple angles, and detects the grinding endpoint indicating the end of the grinding based on the averaged arm torque.

[0026] The sixth method adopts the structure of a grinding device of any one of the first to fifth methods, characterized in that, at the connection part of the swing arm connected to the arm drive part, the arm torque detection part detects the arm torque applied to the swing arm.

[0027] The seventh method adopts the structure of a grinding device from any one of the first to the fifth methods, characterized in that the arm drive unit is a rotary motor that rotates the swing arm, and the arm torque detection unit detects the arm torque applied to the swing arm based on the current value of the rotary motor.

[0028] The eighth method employs the structure of a grinding device from the first to the fifth method, characterized in that the endpoint detection unit detects the grinding endpoint indicating the end of the grinding process based on the differential value of the current value of the rotating motor.

[0029] The ninth method adopts the structure of a grinding device from any of the first to the eighth methods, characterized in that the grinding device has a pad conditioner that conditions the grinding pad, and the pad conditioner performs the conditioner when the swing arm swings.

[0030] The tenth method adopts the structure of a grinding device from any of the first to the ninth methods, characterized in that the endpoint detection unit determines the swing angle of the swing arm and the arm torque corresponding to the swing angle.

[0031] The eleventh method employs a grinding structure in which grinding is performed between a grinding pad and a grinding object, the grinding object being disposed opposite to the grinding pad. The grinding method is characterized in that the grinding pad is held on a grinding table, a swing arm holds a holding part, the holding part holds the grinding object, an arm drive unit swings the swing arm, and when the swing arm swings within a specified angle range, the arm torque applied to the swing arm is detected directly or indirectly. Based on the detected arm torque, a grinding endpoint indicating the end of the grinding is detected. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the overall structure of a grinding apparatus according to one embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram showing the overall structure of a grinding apparatus according to one embodiment of the present invention.

[0034] Figure 3 This is a block diagram illustrating the method of detecting arm torque using an arm torque detection unit.

[0035] Figure 4 This is a diagram illustrating the swinging motion of the top ring.

[0036] Figure 5 This is an example diagram representing a specific range of swing angles where the torque is relatively stable.

[0037] Figure 6 This is another example diagram representing a specific range of swing angles where the torque is relatively stable.

[0038] Figure 7 This is another example of a diagram representing a specific range of swing angles where the torque is relatively stable.

[0039] Figure 8 It is a graph showing the relationship between the oscillation period and a specific angle.

[0040] Figure 9 This is a flowchart illustrating the processing performed by the endpoint detection unit.

[0041] Figure 10A , Figure 10B This is an example diagram showing the motor speed obtained by the endpoint detection unit.

[0042] Figure 11A , Figure 11B This is an example diagram showing the motor angle obtained by integrating the endpoint detection unit.

[0043] Figure 12 This is an example diagram showing the torque command value obtained by the endpoint detection unit.

[0044] Figure 13This is a graph representing the torque command value after moving average.

[0045] Figure 14 This is a diagram showing the torque command value divided into torque command values ​​for each angle.

[0046] Figure 15 It is a graph representing the torque command values ​​obtained through data interpolation.

[0047] Figure 16 This is a graph representing the torque command value obtained through moving average.

[0048] Figure 17 It is a graph representing the torque command value obtained by averaging over each oscillation cycle.

[0049] Figure 18 This is a graph representing the torque command value obtained through moving average.

[0050] Figure 19 It is a graph representing the differential value obtained through differentiation.

[0051] Figure 20 This is a graph showing the current of the motor and the torque of the arm in the grinding table.

[0052] Figure 21 This is a diagram showing the position of the pad dresser as it moves back and forth across a designated area on the grinding pad.

[0053] Figure 22 It is a graph showing the differential values ​​of the arm torque and the differential values ​​of the current.

[0054] Symbol Explanation

[0055] 10: Grinding pad

[0056] 14: Oscillating shaft motor

[0057] 16: Semiconductor wafers

[0058] 26: Arm Torque Detection Unit

[0059] 28: Endpoint Inspection Department

[0060] 30: Grinding table

[0061] 31: Top ring

[0062] 33: Pad Adjuster

[0063] 34: Grinding device

[0064] 50: Eddy current sensor

[0065] 52: Motor

[0066] 56: Current sensor

[0067] 58: Angle range

[0068] 110: Swing arm

[0069] 111: Top ring shaft

[0070] 117: Swing arm shaft

[0071] 120: One direction

[0072] 122: One direction

[0073] 124: Angle

[0074] 126: Torque Detection Unit

[0075] 158: Angle range

[0076] 174, 176: Torque command values

[0077] 180: Current

[0078] 182: Arm Torque

[0079] 184: Time

[0080] 18a: Current Command

[0081] 258: Angle range

[0082] 26a: Torque command value

[0083] 358: Angle range Detailed Implementation

[0084] Hereinafter, embodiments of the present invention will be described with reference to the figures. Furthermore, in the various embodiments described below, the same symbols are used to annotate the same or equivalent elements, and repeated descriptions are omitted. Moreover, the features shown in the various embodiments can be applied to other embodiments as long as they do not contradict each other.

[0085] Figure 1 This is a schematic diagram showing the overall structure of the grinding apparatus 34 according to one embodiment of the present invention. Figure 1 As shown, the polishing apparatus 34 performs polishing between the polishing pad 10 and the object to be polished, which is disposed opposite to the polishing pad 10. The polishing apparatus 34 includes: a polishing table 30 for holding the polishing pad 10; and a top ring 31 (holding part) for holding the substrate such as the semiconductor wafer 16 of the object to be polished and pressing it against the polishing surface on the polishing table.

[0086] The grinding apparatus 34 includes: a swing arm 110 for holding the top ring 31; a swing shaft motor 14 (arm drive unit) for swinging the swing arm 110; and a driver 18 for supplying drive power to the swing shaft motor 14. Furthermore, the grinding apparatus 34 includes: an arm torque detection unit 26 for directly or indirectly detecting the arm torque applied to the swing arm 110 when the swing arm 110 swings within a specified angle range; and an end point detection unit 28 for detecting the end point of grinding, indicating the end of grinding, based on the arm torque detected by the arm torque detection unit 26.

[0087] In this embodiment, when the top ring 31 is held in the swing arm 110, the change in friction between the semiconductor wafer 16 and the polishing pad 10, i.e., the change in arm torque, can be detected with improved accuracy compared to the past when the swing arm 110 swings. This improves the accuracy of polishing endpoint detection. In this embodiment, when the swing arm 110 of the top ring 31 swings to detect torque changes, the sensitivity for detecting torque changes is further improved compared to the past due to noise reduction and other factors described later. Compared to the arm torque method, where the torque used to rotate the swing motor is small when the swing arm swings, the torque change due to the change in polishing friction between the wafer and the polishing pad is minimal. Therefore, if the influence of the torque used to rotate the swing motor is not eliminated, the torque change cannot be detected, potentially leading to inappropriate detection of the polishing endpoint and problems such as over-polishing. This embodiment, as described later, solves this problem by detecting the polishing endpoint when the swing arm 110 swings within a specified angle range.

[0088] In this figure, the polishing table 30 is connected to the motor 52 of the drive unit located below it via a table shaft 102, and can rotate around the table shaft 102. A polishing pad 10 is attached to the upper surface of the polishing table 30, and the surface 101 of the polishing pad 10 forms the polishing surface for polishing the semiconductor wafer 16. A polishing slurry supply nozzle (not shown) is provided above the polishing table 30, through which polishing slurry Q is supplied to the polishing pad 10 on the polishing table 30.

[0089] The grinding apparatus 34 has a driver 118 in the motor 52 that supplies drive power. Furthermore, the grinding apparatus 34 may also have a torque detection unit 126 that detects the torque applied to the grinding table 30 when the grinding table 30 rotates. The endpoint detection unit 28 can also detect the grinding endpoint, indicating the end of grinding, based on the torque detected by the torque detection unit 126. Furthermore, as... Figure 2 As shown, an eddy current sensor 50, which generates eddy currents in the semiconductor wafer 16 and can detect the grinding endpoint by detecting these eddy currents, can also be embedded inside the grinding table 30. The endpoint detection unit 28 can also detect the grinding endpoint, indicating the end of grinding, based on the eddy currents detected by the eddy current sensor 50.

[0090] pass Figure 2Further explanation of grinding device 34. Figure 2 This is a schematic diagram showing the overall structure of the polishing apparatus 34 according to one embodiment of the present invention. The top ring 31 is composed of a top ring body 24 that presses the semiconductor wafer 16 against the polishing surface 101, and a retaining ring 23 that holds the outer periphery of the semiconductor wafer 16 and prevents the semiconductor wafer 16 from flying out of the top ring.

[0091] The top ring 31 is connected to the top ring shaft 111. The top ring shaft 111 moves up and down relative to the swing arm 110 via a vertical moving mechanism (not shown). The vertical movement of the top ring shaft 111 causes the entire top ring 31 to be positioned relative to the swing arm 110 by raising and lowering.

[0092] Furthermore, the top ring shaft 111 is connected to the rotating cylinder 112 via a key (not shown). The rotating cylinder 112 has a timing pulley 113 on its outer periphery. A top ring motor 114 is fixed on the swing arm 110. The aforementioned timing pulley 113 is connected to a timing pulley 116 provided on the top ring motor 114 via a timing belt 115. When the top ring motor 114 rotates, the rotating cylinder 112 and the top ring shaft 111 rotate together via the timing pulley 116, the timing belt 115, and the timing pulley 113, and the top ring 31 rotates as well.

[0093] The swing arm 110 is connected to the rotating shaft of the swing shaft motor 14. The swing shaft motor 14 is fixed to the swing arm shaft 117. Therefore, the swing arm 110 is rotatably supported relative to the swing arm shaft 117.

[0094] The top ring 31 holds a substrate such as a semiconductor wafer 16 on its lower surface. The swing arm 110 is rotatable about the swing arm shaft 117. The top ring 31, which holds the semiconductor wafer 16 on its lower surface, moves from the receiving position of the semiconductor wafer 16 to above the polishing table 30 by the rotation of the swing arm 110. Then, the top ring 31 is lowered, pressing the semiconductor wafer 16 against the surface (polishing surface) 101 of the polishing pad 10. At this time, the top ring 31 and the polishing table 30 are rotated respectively. At the same time, polishing slurry is supplied to the polishing pad 10 from the polishing slurry supply nozzle provided above the polishing table 30. In this way, the semiconductor wafer 16 slides into contact with the polishing surface 101 of the polishing pad 10 to polish the surface of the semiconductor wafer 16.

[0095] like Figure 1As shown, the grinding apparatus 34 has a stage drive unit (motor 52) that rotates and drives the grinding table 30. The grinding apparatus 34 may also have a torque detection unit 126 that detects the stage torque applied to the grinding table 30. The torque detection unit 126 can detect the stage torque based on the current of the stage drive unit of the rotating motor. The driver 118 supplies three-phase (UVW phase) current 54 to the motor 52. The current sensor 56 detects the current of one phase and transmits the detected current to the torque detection unit 126. The torque detection unit 126 transmits the detected current as the stage torque to the end detection unit 28. The end detection unit 28 may detect the grinding end point indicating the end of grinding only from the arm torque detected by the arm torque detection unit 26, or it may also detect the grinding end point indicating the end of grinding considering the stage torque detected by the torque detection unit 126.

[0096] Figure 2 In this embodiment, at the connection point of the swing arm 110 relative to the swing shaft motor 14, the arm torque detection unit 26 detects the arm torque applied to the swing arm 110. Specifically, the arm drive unit is the swing shaft motor (rotary motor) 14 that rotates the swing arm 110, and the arm torque detection unit 26 detects the arm torque applied to the swing arm 110 based on the current value of the swing shaft motor 14. The current value of the swing shaft motor 14 depends on the amount of arm torque in the connection point of the swing arm 110 relative to the swing shaft motor 14. In this embodiment, the current value of the swing shaft motor 14 is obtained from... Figure 3 The current value 18b supplied to the swing shaft motor 14 by the driver 18 shown, or the current command 18a (described later) generated in the driver 18, is as follows: The arm torque, referred to here, is the torque of the force acting on the swing arm 110 about the rotation axis 108, with the rotation axis 108 of the swing arm 110 as the center. The table torque, referred to here, is the torque of the force acting on the grinding table 30 about the rotation axis 192, with the rotation axis 192 of the grinding table 30 as the center.

[0097] use Figure 3 The method for detecting arm torque via arm torque detection unit 26 is explained. Driver 18 inputs a position command 65a regarding the position of the swing arm 110 from control unit 65. Position command 65a is data corresponding to the rotation angle of the swing arm 110 relative to the swing arm shaft 117. Driver 18 also inputs the rotation angle 36a of the swing arm shaft 117 from encoder 36, which is built into the swing shaft motor 14.

[0098] The encoder 36 can detect the rotation angle 36a of the rotating shaft of the swing shaft motor 14, which is also the rotation angle 36a of the swing arm shaft 117. Figure 3 The oscillating shaft motor 14 and encoder 36 are shown separately; however, in reality, the oscillating shaft motor 14 and encoder 36 are integrated. An example of such an integrated motor is a synchronous AC servo motor with a feedback encoder.

[0099] The driver 18 includes a deviation circuit 38, a current generation circuit 40, and a PWM circuit 42. The deviation circuit 38 calculates the deviation 38a between the position command 65a and the rotation angle 36a. The deviation 38a and the current value 18b are input to the current generation circuit 40. The current generation circuit 40 generates a current command 18a based on the deviation 38a and the current value 18b. The PWM circuit 42 receives the current command 18a and generates the current value 18b through PWM (Pulse Width Modulation) control. The current value 18b is a three-phase (U-phase, V-phase, W-phase) current that drives the oscillating axis motor 14. The current value 18b is supplied to the oscillating axis motor 14.

[0100] The current command 18a is a quantity that depends on the current value of the swing shaft motor 14 and also on the arm torque. The arm torque detection unit 26 performs at least one of the following processes on the current command 18a: AD conversion, amplification, rectification, and RMS conversion, and then outputs it as the arm torque 26a to the endpoint detection unit 28. A sensor 136 for detecting the motor's rotational speed is installed in the swing shaft motor 14. The rotational speed sensor 136 can be an electromagnetic, Hall effect, optical, or inductive sensor. The sensor 136 outputs the detected motor rotational speed 138 to the endpoint detection unit 28.

[0101] The current value 18b is the current value of the swing shaft motor 14, and it depends on the arm torque. The arm torque detection unit 26 can also detect the arm torque 26a applied to the swing arm 110 based on the current value 18b. When detecting the current value 18b, the arm torque detection unit 26 can use a current sensor such as a Hall sensor. The torque detection unit 126 for detecting the table torque of the grinding table 30 can also be configured in the same way as the arm torque detection unit 26.

[0102] In the arm torque method, the arm torque changes due to the rotation of the swing motor as the swing arm swings. To make the swing shaft motor 14 rotate, it is necessary to eliminate the influence of torque and detect the torque change caused solely by grinding friction. The following describes the method for detecting torque changes caused solely by grinding friction. Figure 4This diagram illustrates the situation where the top ring 31 and the swing arm 110 swing together. In this embodiment, the swing arm 110 swings within an angle range 58 as indicated by arrow 60. Here, the angle range refers to the entire range, or a portion thereof, of the swing arm 110's swing in degrees (°) when it swings around the rotation axis 108. In this embodiment, the angle range 58 is the maximum angle range of the swing arm 110's swing, and the angle range 58 is constant. That is, the swing ends 62 and 64 are usually fixed during grinding. The positions of the swing ends 62 and 64 can also be changed. The swing arm 110 reciprocates within the angle range 58. Furthermore, the angle range 58 can be expanded or reduced during grinding.

[0103] Within the angle range 58, the swing ends 62 and 64 cause the speed of the swing arm 110 to change the swing direction. Because acceleration occurs in the swing arm 110, it experiences some overshoot or undershoot. Thus, the torque used by the swing ends 62 and 64 to rotate the swing shaft motor 14 is not constant and undergoes significant variations. It is advisable to detect torque variations caused solely by grinding friction outside the vicinity of the swing ends 62 and 64. Furthermore, noise is prone to occur in specific areas during swing. Therefore, this embodiment calculates the arm torque within a specific swing angle range where the torque is relatively stable.

[0104] Figure 5 This is an example diagram representing a specific range of swing angles where the torque is relatively stable. Figure 5 When the swing arm 110 swings within a specified angle range 158, that is, when the swing arm 110 swings throughout the entire angle range 58 and passes through angle range 158, the arm torque detection unit 26 directly or indirectly detects the arm torque applied to the swing arm 110. The reason why the torque is stable in angle range 158 is that it is inside angle range 58 excluding swing ends 62, 64. Angle range 158 is, for example, the center line 128 of angle range 58 (see...). Figure 4 The range before and after. As the size of the angle range 158, when the size of the angle range 58 is set to 100%, the size of the angle range 158 is, for example, 50%. The endpoint detection unit 28 detects the grinding endpoint indicating the end of grinding based on the arm torque detected by the arm torque detection unit 26.

[0105] Figure 6 This is another example diagram representing a specific range of swing angles where the torque is relatively stable. Figure 6The arm torque detection unit 26 detects the arm torque within a specified angle range 258, located inside the angle range 58, when the swing arm 110 swings in a specified direction 120. That is, when the swing arm 110 swings throughout the entire angle range 58 and passes through the angle range 258 in one direction 120, the arm torque is detected within the angle range 258. The reason the arm torque is stable in the specified direction 120 is because the swing direction of the swing arm 110 is the same as (or different from) the rotation direction of the polishing table 30, thus stabilizing the arm torque. In other words, the arm torque varies depending on whether the swing direction of the swing arm 110 is the same as or different from the rotation direction of the polishing table 30. When only monitoring the arm torque when the swing arm 110 swings in the specified direction 120, the change in arm torque caused by the rotation of the polishing table 30 is reduced, making it easier to detect only the change in arm torque caused by the polishing friction between the polishing pad 10 and the semiconductor wafer 16.

[0106] When the swing arm 110 swings in a specified direction 122 opposite to a specified direction 120, the arm torque detection unit 26 can also detect the arm torque in a specified angle range 358 located inside the angle range 58.

[0107] Although the arm torque varies depending on whether the swing direction of the swing arm 110 is the same as or different from the rotation direction of the grinding table 30, the arm torque detection unit 26 can also detect the arm torque within a specified angle range 258 and 358 when the swing arm 110 swings in two directions 120 and 122. That is, when the swing arm 110 swings throughout the entire angle range 58, it passes through the angle range 258 in one direction 120 and then passes through the angle range 258 in one direction 122, the arm torque is detected within the angle ranges 258 and 358. This is because sometimes the change in torque is small depending on whether the swing direction of the swing arm 110 is the same as or different from the rotation direction of the grinding table 30.

[0108] Furthermore, the arm torque can be detected in both directions 120 and 122 to calculate the average value of the arm torque in both directions 120 and 122. By averaging, the variation in arm torque caused by the different rotation directions of the polishing table 30 is reduced, and only the variation in arm torque caused by the polishing friction between the polishing pad 10 and the semiconductor wafer 16 can be detected.

[0109] Figure 7 This is another example diagram showing a specific swing angle range where the torque is relatively stable. The arm torque detection unit 26 can also detect the arm torque at a specified angle 124 within a specified angle range 58. Here, angle 124 is the angle measured from one end (swing end 62) of the angle range 58. Angle 124 is not limited to one point within the angle range 58, but can be multiple points. The arm torque can also be calculated by averaging the arm torque from multiple points.

[0110] The specified angle 124 does not strictly need to be a single angle, such as 4 degrees. Setting the angle range 58 to 100% can also be centered at 4 degrees, for example, equivalent to 1% of the angle range. Furthermore, when the swing arm 110 swings in both directions 120 and 122, this includes when it rotates in one direction 120 to reach the 4-degree position, and when it rotates in the opposite direction 122 to reach the same position. Figure 6 Similarly, when explaining, one can consider only the position reached by rotating 120 degrees in one direction, or only the position reached by rotating 122 degrees in the opposite direction. One can also consider the position reached by rotating 122 degrees in both directions.

[0111] The reason why the arm torque is stable at a specified angle 124 is that the swing arm 110 swings at the same position on the polishing table 30, and therefore the torque borne by the swing arm 110 from the polishing table 30 is the same. Therefore, when monitoring the change in arm torque at the specified angle 124, it is easy to detect only the change in arm torque caused by the polishing friction between the polishing pad 10 and the semiconductor wafer 16. However, when only the change in arm torque at one angle 124 is used for endpoint detection, it is easily affected by noise included in the measured value, and noise reduction is necessary.

[0112] Figure 5 , Figure 6 , Figure 7 The angle range for detecting arm torque decreases sequentially. Because the influence of the grinding stage 30's rotation decreases as the angle range narrows, it's easier to detect only the change in arm torque caused by the grinding friction between the grinding pad 10 and the semiconductor wafer 16. However, as the angle range narrows, the number of detectable arm torque data points decreases. Consequently, the noise inherent in the data itself increases. Therefore, it's necessary to select an appropriate angle range.

[0113] Generally, when detecting arm torque within a specified angular range, the obtained arm torque usually contains noise. One method to reduce noise is to perform averaging. Averaging includes time averaging. For example, for multiple data points, the detected time series data can be subjected to a moving average to reduce noise.

[0114] Therefore, in this embodiment, the detected time series data can also be averaged over time for multiple data points. Alternatively, the detected time series data can be categorized into data for each swing angle and then averaged. This is because, as described, focusing on the arm torque change at a specific swing angle, the interaction between the rotation of the grinding table 30 and the swing of the swing arm 110 is least affected, thus showing the change in arm torque caused by the grinding friction between the grinding pad 10 and the semiconductor wafer 16.

[0115] Averaging time-series data as is also problematic. The swing arm 110 may experience some upward or downward movement. Furthermore, control to maintain a constant swing period is typically not implemented. Therefore, the swing period (the time it takes for the swing arm 110 to travel back and forth from a specified angular position once and return to that position) becomes variable and unpredictable. Because the swing period and the relationship between time and angular position are not fixed when averaging time-series data as is, the angular position of the swing arm 110 is unclear. Consequently, in the worst-case scenario, measurements with significant errors at the swing end are used, leading to reduced accuracy at the grinding endpoint.

[0116] use Figure 8 This illustrates the point. Figure 8 It is a graph showing the relationship between the oscillation period and a specific angle. Figure 8 The horizontal axis represents time (seconds), and the vertical axis represents the measured value of the arm torque (voltage, in volts). The solid circle is... Figure 7 The arm torque of the swing end 62 shown is in the hollow circle. Figure 7 The arm torque at angle 124 is shown. The swing arm 110 moves from one swing end 62 to the other swing end 194, and then returns from swing end 194 to swing end 62, completing one round trip in time 132, which is the swing period. The time 134 for the swing arm 110 to move from angle 124 to swing end 62 is as follows... Figure 8 The representation shown is not fixed.

[0117] Therefore, when averaging the time series data as is, as described, because the relationship between time and angular position is not fixed, the angular position of the swing arm 110 is unknown. Thus, the worst-case scenario is using a measurement value with significant error at the swing end. Therefore, it is advisable to classify the detected time series data into data for each swing angle and then average them. In the following embodiment, the endpoint detection unit 28 determines the swing angle of the swing arm 110 and calculates the arm torque corresponding to the swing angle.

[0118] Arm torque detection unit 26 Figure 5 The arm torque is detected at multiple angles within the specified angle range 158. For at least one cycle of oscillation, the endpoint detection unit 28 averages the arm torque obtained at multiple angles and detects the grinding endpoint indicating the end of grinding based on the averaged arm torque. That is, the detected time-series data is categorized into data for each oscillation angle and then averaged. In other words, this can be expressed as monitoring the arm torque at angular positions, i.e., the change in arm torque at the same angular position. Alternatively, it can be described as transforming the time-series data into data for each oscillation angle.

[0119] Figure 9 This is a flowchart illustrating the processing performed by the endpoint detection unit 28. The endpoint detection unit 28... Figure 5 When the swing arm 110 is within the specified angle range 158, the motor speed is obtained as a voltage signal from the sensor 136 (step S10). An example of the obtained motor speed 144 is shown in... Figure 10A , Figure 10B . Figure 10A , Figure 10B In the diagram, the horizontal axis represents time (sec) and the vertical axis represents voltage (V). Figure 10B Will Figure 10A A portion of 140 expands in the horizontal direction. Figure 10B In the middle, it does not expand in the vertical direction.

[0120] The endpoint detection unit 28 obtains a moving average over time to remove noise from the motor speed 144 (step S12). After obtaining the moving average, the motor speed 144 is integrated to calculate the motor angle 146 (step S14). The motor angle 146 is the rotational position of the swing arm 110. In this embodiment, the motor angle 146 is... Figure 5 The angle range shown is within 158 degrees. An example of a motor angle of 146 degrees obtained after integration is shown in [the figure]. Figure 11A , Figure 11B . Figure 11A , Figure 11B In the diagram, the horizontal axis represents time (sec) and the vertical axis represents angle (degree). Figure 11B Will Figure 11A A portion of 142 expands in the horizontal direction. Figure 11B In the middle, it does not expand in the vertical direction.

[0121] Endpoint testing section 28 only Figure 11B The arm torque 26a is obtained within the angle range 158 shown and used to detect the endpoint, or the arm torque 26a is obtained throughout the entire angle range 58, but only the arm torque 26a obtained within the angle range 158 is used to detect the endpoint. Similarly, the arm torque detection unit 26 may also obtain the arm torque 26a only within the angle range 158, or the arm torque 26a throughout the entire angle range 58, but only the arm torque 26a obtained within the angle range 158 is output to the endpoint detection unit 28.

[0122] At the same time that the endpoint detection unit 28 acquires the motor speed as a voltage signal (step S10), if Figure 5 When the swing arm 110 is within the specified angle range 158 shown, a torque command value 26a is obtained from the arm torque detection unit 26 as a voltage signal (step S16). An example of the obtained torque command value 26a is shown in... Figure 12 . Figure 12 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents voltage (V).

[0123] The endpoint detection unit 28 performs an autocorrelation (step S18) to determine the swing period of the swing arm 110 from the acquired torque command value 26a. The reason for performing the autocorrelation is to calculate the swing period. Knowing the swing period allows us to know the time at the swing end. Alternatively, sometimes at the swing end, the torque command value 26a is used to obtain a peak value, and the swing period is determined by detecting the peak value. However, the peak value of the torque command value 26a is not clear, so sometimes the period cannot be accurately detected. When the signal contains noise, generally speaking, the method of performing the autocorrelation can reliably detect the period. When knowing the time at the swing end, when obtaining the moving average of the torque command value 26a, it is possible to avoid performing a moving average near the swing end or a moving average across the swing end. This is because a moving average near the swing end or a moving average across the swing end is not suitable, as described above.

[0124] Next, the endpoint detection unit 28 obtains a moving average over time to remove noise from the acquired torque command value 26a (step S20). At this time, a moving average near the end of the swing or a moving average across the end of the swing is not performed. Figure 13 This indicates the torque command value of 196 after moving average. Figure 13 The horizontal axis represents time (sec), and the vertical axis represents voltage (V).

[0125] When the endpoint detection unit 28 obtains the motor angle and torque command values, it calculates the swing angle of the swing arm 110 and the torque command value corresponding to that angle from these data, and divides the torque command value into torque command values ​​for each angle (step S22). The reason for using the term "divided" is that in this embodiment, for the swing angle, Figure 5 The angle range of 158 shown is divided into 100. The method for calculating the torque command value corresponding to the angle is as follows: since the motor angle is the swing angle of the swing arm 110, and the torque command value obtained at the moment of obtaining the motor angle is the torque command value corresponding to the swing angle of the swing arm 110, the torque command value corresponding to the swing angle can be calculated.

[0126] Figure 14 This diagram shows the torque command value divided into torque command values ​​for each angle. One circle, 152, represents the torque command value divided into one angle of 100 degrees. Figure 14 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents voltage (V). The data 150 in the first column of the vertical direction represents the torque command value obtained when the swing arm 110 makes one round trip, within the angle range 158. However, because the data 150 in this first column of the vertical direction are obtained at different times, they are not strictly on the same time axis. Each data point is positioned on the time axis corresponding to the time at which it is obtained. This will be explained below. Figure 15 , Figure 16The same applies.

[0127] In the data 150 in column 1 of the vertical direction, the data 160 near the top is... Figure 5 The data is obtained near one of the ends 164 and 166 of the angle range 158 shown. In the data 150 of the vertical column portion, the data 162 near the bottom is... Figure 5 The data is obtained from one of the angle ranges of 158°, around 164° or 166°. This is based on the following... Figure 15 , Figure 16 Similarly, because the arm torque is larger or smaller when compared between ends 164 and 166 within the angle range of 158, it becomes... Figure 14 The distribution shown. From Figure 12 , Figure 13 Understand whether the arm torque is large or small when comparing the ends 164 and 166 within the angle range of 158.

[0128] Next, in order to determine the torque command value between the torque command values ​​divided into 100 segments, the endpoint detection unit 28 uses data interpolation to determine the torque command value between temporally adjacent torque command values ​​divided into 100 segments (step S24). The data interpolation method can be linear interpolation or quadratic function interpolation, etc. The torque command value obtained through interpolation is displayed on... Figure 15 . Figure 15 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents voltage (V). A single horizontal line, 154, represents the torque command value divided into 100° intervals. Interpolated data is not shown in the diagram. Figure 15 . Figure 15 In the middle, the ends of the horizontal lines 154 that are adjacent to each other at the same angle are connected by a straight line.

[0129] After interpolation, the endpoint detection unit 28 performs a moving average to remove noise (step S26). The torque command value obtained by the moving average is displayed. Figure 16 . Figure 16 In the graph, the horizontal axis represents time (sec) and the vertical axis represents voltage (V). A single point 156 represents the torque command value after being divided into 100 angular moving averages. The interpolated data is not shown in the graph. Figure 16 . Figure 15 Points 16 that are adjacent but not sharing the same angle are not connected. Therefore, in Figure 15 As can be seen, a continuous line in the horizontal direction can be regarded as an isolated point 156.

[0130] from Figures 14-16 Especially from Figure 16 Learn more about the following. Figure 16The image clearly shows multiple identical curves extending horizontally in a linear fashion, juxtaposed vertically. Alternatively, multiple horizontal stripes can be seen juxtaposed vertically. For example, each of the uppermost data points 160, each of the lowermost data points 162, and the data points between the uppermost and lowermost data points 160 and 162 can be seen to each constitute a stripe. In reality, a stripe is composed of multiple points 156, not a continuous sequence of points 156. However, Figure 16 The display shows that one stripe represents a gradual change in the arm torque at each swing angle during grinding, independent of the swing of the swing arm 110. Furthermore, Figure 16 It also shows that the arm torque changed significantly at 168 and 172 at the end of the grinding process.

[0131] return Figure 9 When processing the flowchart, the endpoint detection unit 28 calculates the average value for each oscillation cycle (each time) after obtaining the moving average (step S26) (step S28). This is for... Figure 16 The average value of the data 150 in the vertical column shown is calculated. The resulting averaged torque command value 174 is then displayed. Figure 17 . Figure 17 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents voltage (V). Because the torque command value of 174 is the average value for each oscillation cycle (each time), the time aspect is not calculated continuously. Figure 17 The torque command value 174 shown is a line graph obtained by connecting the time-discontinuous torque command value 174 with a straight line.

[0132] The endpoint detection unit 28 then calculates the moving average of the torque command value 174 over time (step S30). The torque command value 176 obtained by the moving average is displayed. Figure 18 . Figure 18 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents voltage (V).

[0133] Next, the endpoint detection unit 28 calculates the derivative of the torque command value 176 (step S32). Then, the endpoint detection unit 28 calculates the moving average of the differentiated torque command value 176 over time (step S34). The derivative value 178 obtained through the moving average is displayed... Figure 19 . Figure 19 In the graph, the horizontal axis represents time (sec) and the vertical axis represents voltage (V) / time (minutes).

[0134] The endpoint detection unit 28 then determines whether the grinding endpoint has been reached based on the differential value 178. This determination is made by checking whether the differential value 178 meets a specified detection condition for detecting the grinding endpoint (step S36). The specified detection condition is, for example, whether the differential value 178 is greater than a specified value. However, the specified detection condition is not limited to this. For example, other specified detection conditions may also be... Figure 18 Is the torque command value of 176 shown greater than the specified value?

[0135] Endpoint detection section 28 judged as Figure 19 The differential value is 178, or Figure 18 When the torque command value 176 meets the specified detection conditions for detecting the grinding endpoint, it is determined that the grinding endpoint has been detected (step S38). At this time, the grinding ends. Alternatively, if the endpoint detection unit 28 determines that the differential value 178 does not meet the specified detection conditions for detecting the grinding endpoint, it returns to steps S10 and S16 in order to continue detecting the grinding endpoint.

[0136] The above embodiment has a grinding apparatus with a pad conditioner 33 for conditioning the grinding pad. However, when the swing arm 110 swings for grinding, the pad conditioner 33 does not condition the pad. However, it is also possible for the pad conditioner 33 to condition the pad when the swing arm 110 swings for grinding.

[0137] When the swing arm 110 swings for grinding, and the pad dresser 33 is dressing, it may adversely affect the detection of arm torque. The results of an experiment investigating whether the dressing of the pad dresser 33 would adversely affect the detection of arm torque are shown in... Figures 20-22 .according to Figures 20-22 The experiment shown confirms that the trimming has a significant impact on the current of the motor 52 of the grinding table 30, but a very small impact on the arm torque.

[0138] Figure 20 The display shows the current of the motor 52 driving the grinding table 30 as 180 and the arm torque as 182. Figure 20 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents current (A). Figure 20 The image also shows the time 184 required for the pad dresser 33 to make one round trip across a designated area on the polishing pad 10 for dressing. The position 186 of the pad dresser 33 during its round trip across the designated area on the polishing pad 10 is shown in the image. Figure 21 . Figure 21 In the diagram, the horizontal axis represents time (sec) and the vertical axis represents distance (mm). Position 186 is the position of the pad conditioner 33, determined from a designated reference point on the abrasive pad 10.

[0139] Figure 22 The display shows the value of 188 for the arm torque (182 differentials) and the value of 190 for the current (180 differentials). Figure 22 In the graph, the horizontal axis represents time (sec), and the vertical axis represents current (A) / time (minutes). From... Figure 20 , 22 The noise from the current 180 of motor 52 synchronized with the oscillating motion of pad dresser 33 was observed. Additionally, the noise from the arm torque 182 synchronized with the oscillating motion of pad dresser 33 was observed. Therefore, when the swing arm 110 oscillates for grinding, the arm torque 182 can still be accurately detected even when the pad dresser 33 is dressing.

[0140] Alternatively, the method for detecting the arm torque can be other than monitoring the current of the swing shaft motor 14 that drives the swing arm 110. For example, a torque sensor for detecting torque variations in the swing arm 110 can be configured in the swing arm 110 by means of engagement or the like. The torque sensor can be a load sensor or a strain gauge.

[0141] The following describes a polishing method for polishing between a polishing pad 10 and a semiconductor wafer 16 disposed opposite to the polishing pad 10. Using... Figure 1 The polishing method of the polishing apparatus 34 shown is to hold the polishing pad 10 on the polishing table 30, and to hold the top ring 31 of the semiconductor wafer 16 held by the swing arm 110. The swing shaft motor 14 swings the swing arm 110. When the swing arm 110 swings at a specified angle range 158, the arm torque detection unit 26 directly or indirectly detects the arm torque 26a applied to the swing arm 110. The endpoint detection unit 28 detects the polishing endpoint indicating the end of polishing based on the detected arm torque 26a.

[0142] Furthermore, the operation of embodiments of the present invention can also be performed using the following software and / or systems. For example, the system (grinding apparatus) includes: a main controller (control unit) for controlling the entire system; and multiple sub-controllers for controlling the operation of each unit (drive unit, holding unit, end point detection unit). The main controller and sub-controllers each include a CPU, a memory, a recording medium, and software (program) for operating each unit and stored in the recording medium. The grinding method of embodiments of the present invention, such as the "method for detecting the grinding end point indicating the end of grinding based on the detected arm torque 26a" executed by the end point detection unit, can also be executed by software (program).

[0143] The above describes examples of embodiments of the present invention. However, the above embodiments are provided for ease of understanding of the present invention and are not intended to limit the present invention. The present invention can be modified and improved without departing from its spirit, and the present invention naturally includes its equivalents. Furthermore, within the scope of solving at least a portion of the above problems or achieving at least a portion of the effects, the structural elements described in the claims and specification can be arbitrarily combined or omitted.

Claims

1. A grinding apparatus for grinding between a grinding pad and a workpiece, the workpiece being disposed opposite to the grinding pad, the grinding apparatus characterized in that it comprises: A grinding table for holding the grinding pad; A holding part for holding the object to be ground; A swing arm for holding the holding part; An arm drive unit for swinging the swing arm; An arm torque detection unit directly or indirectly detects the arm torque applied to the swing arm within the angle range excluding the swing end of the maximum swing angle range of the swing arm. and The endpoint detection unit detects the grinding endpoint, indicating the end of the grinding process, based on the arm torque detected by the arm torque detection unit.

2. The grinding apparatus as described in claim 1, characterized in that, The arm torque detection unit detects the arm torque within the angular range excluding the swing end only when the swing arm swings in one direction.

3. The grinding apparatus as described in claim 1, characterized in that, When the swing arm swings in two directions, the arm torque detection unit detects the arm torque within the angle range excluding the swing end.

4. The grinding apparatus according to any one of claims 1 to 3, characterized in that, The arm torque detection unit detects the arm torque at a specified angle within the angular range excluding the swing end.

5. The grinding apparatus according to any one of claims 1 to 3, characterized in that, The arm torque detection unit detects the arm torque at multiple angles within the angle range excluding the swing end. For at least one cycle of oscillation, the endpoint detection unit averages the arm torque obtained at the plurality of angles and detects the grinding endpoint indicating the end of the grinding based on the averaged arm torque.

6. The grinding apparatus according to any one of claims 1 to 3, characterized in that, At the connection point of the swing arm that is connected to the arm drive unit, the arm torque detection unit detects the arm torque applied to the swing arm.

7. The grinding apparatus according to any one of claims 1 to 3, characterized in that, The arm drive unit is a rotary motor that rotates the swing arm. The arm torque detection unit detects the arm torque applied to the swing arm based on the current value of the rotary motor.

8. The grinding apparatus as described in claim 7, characterized in that, The endpoint detection unit detects the grinding endpoint, indicating the end of the grinding process, based on the differential value of the current value of the rotary motor.

9. The grinding apparatus according to any one of claims 1 to 3, characterized in that, The grinding device has a pad conditioner that conditions the grinding pad during the swinging of the swing arm.

10. The grinding apparatus according to any one of claims 1 to 3, characterized in that, The endpoint detection unit determines the swing angle of the swing arm and the arm torque corresponding to the swing angle.

11. A grinding method comprising grinding between a grinding pad and a grinding object disposed opposite to the grinding pad, the grinding method being characterized in that, Hold the abrasive pad on the abrasive table. The swing arm holds the holding part, which in turn holds the object to be ground. The arm drive unit swings the swing arm. Within the maximum angular range of the swing arm's swing, excluding the swing end, the arm torque applied to the swing arm is detected directly or indirectly. Based on the detected arm torque, the grinding endpoint, indicating the end of the grinding process, is detected.

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