Substrate processing apparatus, polishing member dressing control method, and storage medium

Abstract

A substrate processing apparatus that makes a substrate in sliding contact on a polishing member to polish the substrate is provided with: a dresser that trims the polishing member by oscillating on the polishing member, and that is able to adjust the oscillation speed in a plurality of scan regions set on the polishing member along the radial direction; a height detection section that generates a pad profile by measuring the surface height of the polishing member along the radial direction of the polishing member; a dresser load setting section that sets a dresser load that the dresser exerts on the polishing member; a pad height correction section that calculates a correction amount of the surface height of the polishing member corresponding to the variation of the dresser load from a reference load over the radial direction, and corrects the measured value of the surface height with the correction amount, thereby correcting the pad profile; and a movement speed calculation section that performs adjustment of the oscillation speed of the dresser in each scan region based on the corrected pad profile.

Description

Technical Field

[0001] This invention relates to a method for controlling the finishing of the grinding components of a grinding substrate and a substrate processing apparatus. Background Technology

[0002] One method for planarizing the surface of substrates used to form semiconductor devices is grinding using a chemical mechanical polishing (CMP) apparatus. A CMP apparatus includes a polishing component (polishing cloth, polishing pad, etc.) and a holding part (top ring, polishing head, chuck, etc.) for holding the substrate or other objects to be polished. The surface of the object to be polished (the surface to be polished) is pressed against the surface of the polishing component, and while a polishing fluid (abrasive slurry, chemical solution, paste, pure water, etc.) is supplied between the polishing component and the object to be polished, the polishing component and the object to be polished move relative to each other, thereby polishing the surface of the object to be polished until it is flat.

[0003] Materials used for grinding components typically include foamed resin and non-woven fabric. The surface of the grinding component has fine irregularities that act as chip channels to effectively prevent clogging and reduce grinding resistance. However, as the grinding component continuously grinds the object, these fine irregularities on the surface are damaged, leading to a decrease in grinding efficiency. Therefore, the surface of the grinding component is periodically dressed (reshaped) using a dresser with a large number of abrasive particles, such as electro-attached diamond particles, to re-form the fine irregularities on the surface.

[0004] As a method for dressing grinding components, for example, a dressing surface is pressed against a rotating grinding component while a rotating dressing device is moved (in an arc, a straight reciprocating motion, or an oscillating motion). During the dressing of the grinding component, although the amount is minute, the surface of the grinding component is still removed. Therefore, if proper dressing is not performed, unsuitable undulations will occur on the surface of the grinding component, potentially causing a deviation in the grinding ratio within the ground surface. This deviation in the grinding ratio can lead to poor grinding; therefore, proper dressing is necessary to prevent unsuitable undulations on the surface of the grinding component. By adjusting conditions such as the rotational speed of the grinding component, the rotational speed of the dressing device, and the moving speed of the dressing device (dressing conditions), deviations in the grinding ratio can be suppressed.

[0005] For example, in the grinding apparatus described in Japanese Patent Application Publication No. 2014-161944, multiple swing intervals are set along the swing direction of the dresser, and the difference between the current profile of the grinding pad obtained based on the measured value of the surface height of the grinding component in each swing interval and the profile of the target grinding pad is calculated. The moving speed of the dresser in each swing interval is then corrected so that the difference disappears.

[0006] In addition, in the grinding apparatus described in Japanese Patent Application Publication No. 2020-28955, when the load (dressing load) applied to the grinding pad during dressing is changed, a correction amount for the dresser height corresponding to the change in the dressing load relative to the reference dressing load is calculated, and the measured value of the dresser height (grinding pad height) is corrected.

[0007] When the dressing load is varied (e.g., when the dressing load is increased), the polishing pad is pressed down accordingly, and therefore the measured value of the polishing pad height decreases. However, the amount of variation in the polishing pad height is not constant across the entire surface of the polishing pad; for example, the amount of variation in height at the center of the polishing pad may differ from that at the outer periphery. Therefore, when the dressing load is varied, it may not be possible to obtain the desired height profile radially across the polishing component. Summary of the Invention

[0008] One aspect of the present invention is a substrate processing apparatus that grinds a substrate by sliding it against a grinding member. The substrate processing apparatus includes: a dresser that dresses the grinding member by oscillating on it, and the dresser is adjustable in oscillation speed across a plurality of scanning areas radially defined on the grinding member; a height detection unit that generates a pad profile by measuring the surface height of the grinding member radially along the grinding member; a dresser load setting unit that sets a dresser load applied by the dresser to the grinding member; a pad height correction unit that calculates a correction amount for the surface height of the grinding member corresponding to the variation of the dresser load relative to a reference load throughout the radial direction, and corrects the measured surface height using the correction amount, thereby correcting the pad profile; and a movement speed calculation unit that adjusts the oscillation speed of the dresser in each scanning area based on the corrected pad profile.

[0009] One aspect of the present invention is a method for dressing a grinding component, wherein a dresser is oscillating on a grinding component used in a substrate grinding apparatus to dress the grinding component. In this method, the dresser can adjust its oscillation speed in multiple scanning areas set on the grinding component along the oscillation direction. The method comprises: a measurement step, generating a pad profile by measuring the surface height of the grinding component along the radial direction of the grinding component; a dresser load setting step, setting a dresser load applied by the dresser to the grinding component; a pad height correction step, calculating a correction amount for the surface height of the grinding component corresponding to the variation of the dresser load relative to a reference load throughout the radial direction, and correcting the measured value of the surface height with the correction amount, thereby correcting the pad profile; and a movement speed calculation step, adjusting the oscillation speed of the dresser in each scanning area based on the corrected pad profile. Attached Figure Description

[0010] Figure 1 This is a top view that schematically illustrates the structure of a substrate processing apparatus according to one embodiment of the present invention.

[0011] Figure 2 This is a schematic diagram showing a grinding apparatus for grinding a substrate.

[0012] Figure 3 It is a schematic top view showing the dresser and grinding pad.

[0013] Figure 4 This is a diagram showing an example of a scanning area set on a polishing pad.

[0014] Figure 5 This is an explanatory diagram showing the relationship between the scanning area and the monitoring area of ​​the polishing pad.

[0015] Figure 6 This is a block diagram illustrating an example of the functional block structure of the trimmer control unit.

[0016] Figure 7 This is an illustrative diagram showing an example of the contour shift of the grinding pad height in each scanned area.

[0017] Figure 8 This is an explanatory diagram showing an example of the trimmer movement speed versus the reference value in each scanning area.

[0018] Figure 9 This is a graph illustrating an example of the relationship between the pad height and the radius position of the grinding pad when the load on the dresser changes.

[0019] Figure 10This is a graph illustrating an example of the relationship between the pad height relative to the radius position of the grinding pad when the set value (measured load) of the dressing load changes relative to the reference load.

[0020] Figure 11 This is a graph representing an example of the pad height correction amount relative to the radius of the grinding pad.

[0021] Figure 12 This is a flowchart illustrating an example of the operation of a substrate processing apparatus for an polishing pad.

[0022] Figure 13 This is a flowchart illustrating an example of a substrate processing procedure.

[0023] Figure 14 This is a flowchart illustrating an example of the calculation process for the reference load pad height.

[0024] Figure 15 This is a graph illustrating an example of the relationship between the pad height and the radius position of the grinding pad under varying conditions of the dresser load. Figure 15 (a) indicates the case where no pad height correction was performed. Figure 15 (b) indicates the case where pad height correction has been performed. Detailed Implementation

[0025] Figure 1 This is a top view showing the overall structure of the substrate processing apparatus. The substrate processing apparatus 10 is divided into a loading / unloading section 12, a polishing section 13, and a cleaning section 14, and these are disposed inside the housing 11. In addition, the substrate processing apparatus 10 includes an apparatus control section 15, which controls the operation of substrate handling, polishing, cleaning, and other processing.

[0026] The loading / unloading unit 12 includes: a front loading section 20 holding a substrate cassette storing multiple substrates W; a traveling mechanism 21; and a transport robot 22. The transport robot 22 has two robotic arms positioned above and below it. By moving along the traveling mechanism 21, it removes the substrates W placed in the substrate cassette of the front loading section 20 and transports them to the polishing section 13. It also performs the action of returning processed substrates from the cleaning section 14 back to the substrate cassette. Furthermore, the substrate W can be a typical circular wafer.

[0027] The polishing unit 13 is equipped with multiple polishing devices 13A to 13D for polishing (planarization) substrates, which are arranged along the long side of the substrate processing apparatus. A first linear conveying device 16 and a second linear conveying device 17, serving as a conveying mechanism for transporting substrates W, are provided between the polishing unit 13 and the cleaning unit 14. The first linear conveying device 16 can move freely between a first position receiving substrate W from the loading / unloading unit 12; a second and third position transferring substrate W between polishing devices 13A and 13B; and a fourth position transferring substrate W to the second linear conveying device 17.

[0028] The second linear conveying device 17 is movable between a fifth position for receiving substrate W from the first linear conveying device 16, and a sixth and seventh position for transferring substrate W between the polishing devices 13C and 13D. A swing conveying device 23 is provided between the first linear conveying device 16 and the second linear conveying device 17. This swing conveying device 23 is used to transport substrate W from the fourth and fifth positions to the cleaning unit 14, and to transport substrate W from the fourth position to the fifth position.

[0029] The cleaning unit 14 includes: a first substrate cleaning device 30; a second substrate cleaning device 31; a substrate drying device 32; and transport robots 33 and 34 for transferring substrates between these devices. The substrate W, which has undergone grinding treatment by the grinding device, is cleaned in the first substrate cleaning device 30 (primary cleaning), and then further cleaned in the second substrate cleaning device 31 (fine cleaning). The cleaned substrate is transferred from the second substrate cleaning device 31 to the substrate drying device 32 for rotary drying. The dried substrate W is removed by the transport robot 22 and returned to the substrate cassette placed in the front loading unit 20.

[0030] like Figure 2 As shown, each of the polishing devices 13A to 13D provided in the polishing section 13 includes: a polishing unit 40 for polishing the substrate W; and a trimming unit 41 for adjusting (adjusting) the polishing pad 43 used in polishing the substrate W. The polishing unit 40 and the trimming unit 41 are provided on the base 42.

[0031] The polishing unit 40 includes: a polishing pad (polishing component) 43; a polishing table 44 for holding the polishing pad 43; a top ring (substrate holding part) 45 connected to the lower end of the top ring shaft 46; and a polishing slurry supply nozzle 47 for supplying polishing slurry to the polishing pad 43.

[0032] The top ring 45 is configured to hold the substrate W on its lower surface by vacuum adsorption. The top ring shaft 46 is rotated by a motor (not shown), thereby rotating the top ring 45 and the substrate W. The top ring shaft 46 is connected to a rotatable top ring arm 48, which is also driven by a motor (not shown), causing the top ring 45 to move between a polishing position for polishing the substrate W and a loading / unloading position for loading and unloading the substrate W. Furthermore, the top ring 45 moves up and down relative to the polishing pad 43 via a vertical movement mechanism (not shown) (e.g., a vertical movement mechanism composed of a servo motor and a ball screw).

[0033] The grinding table 44 rotates about its axis via a motor (not shown) disposed below it. A grinding pad 43 is attached to the upper surface of the grinding table 44, and the upper surface of the grinding pad 43 forms the grinding surface 43a of the grinding substrate W. The grinding pad 43 is made of, for example, foamed resin or non-woven fabric, and its surface (grinding surface 43a) is formed with fine bumps and depressions to act as chip grooves that effectively prevent clogging and reduce grinding resistance.

[0034] Polishing of the substrate W based on the polishing pad 43 is performed as follows: The top ring 45 and the polishing table 44 are rotated respectively, and polishing slurry is supplied to the polishing pad 43 through the polishing slurry supply nozzle 47. In this state, the top ring 45 holding the substrate W is lowered, and the substrate W is pressed against the polishing surface 43a of the polishing pad 43 by a pressurizing mechanism (not shown) consisting of an air bladder provided in the top ring 45. The substrate W and the polishing pad 43 slide into contact with each other in the presence of polishing slurry, thereby polishing and planarizing the surface of the substrate W.

[0035] A film thickness sensor (film thickness measuring machine) 49 for measuring the film thickness of substrate W is disposed inside the polishing table 44. The film thickness sensor 49 can be a non-contact sensor such as an eddy current sensor or an optical sensor, and the detection surface of the film thickness sensor 49 is configured to face the surface of substrate W held in the top ring 45. The film thickness sensor 49 moves across the surface of substrate W while rotating with the polishing table 44, and measures the film thickness of substrate W. The measured film thickness value is sent to a polishing control unit (not shown) to generate a film thickness profile of substrate W (film thickness distribution along the radial direction of substrate W), and the polishing process of substrate W ends when a predetermined film thickness value is reached.

[0036] The dressing unit 41 includes: a dresser 51 that contacts the grinding surface 43a of the grinding pad 43; a dresser shaft 53 connected to the dresser 51 via a universal joint 52; a cylinder 54 disposed at the upper end of the dresser shaft 53; and a dresser arm 55 that supports the dresser shaft 53 for free rotation. Abrasive grains such as diamond particles are fixed on the lower surface of the dresser 51. The lower surface of the dresser 51 forms a dressing surface for dressing the grinding surface 43a of the grinding pad 43.

[0037] As a dressing surface, a circular dressing surface (a dressing surface on which abrasive grains are fixed integrally on the lower surface of the dresser 51), an annular dressing surface (a dressing surface on which abrasive grains are fixed at the periphery of the lower surface of the dresser 51), or multiple circular dressing surfaces (a dressing surface on which abrasive grains are fixed on the surface of multiple small-diameter plates arranged at approximately equal intervals around the center of the dresser 51). Furthermore, in this embodiment, the dresser 51 is provided with a circular dressing surface.

[0038] The dresser shaft 53 and the dresser 51 are configured to move up and down relative to the dresser arm 55. The cylinder 54 is a device that applies pressure (dresser load) to the grinding pad 43 on the dresser 51. The dresser load can be adjusted by adjusting the air pressure supplied to the cylinder 54 by the dresser control unit 60 described later.

[0039] The dresser arm 55 is driven by a motor 57 and configured to swing around a pivot 56. The dresser shaft 53 rotates via a motor (not shown) located within the dresser arm 55, thereby causing the dresser 51 to rotate about its axis. A cylinder 54 presses the dresser 51 against the grinding surface 43a with a specified dresser load via the dresser shaft 53. A universal joint 52 is configured to allow tilting movement of the dresser 51 and transmit the rotation of the dresser shaft 53 to the dresser 51. Thus, even if the dresser shaft 53 is slightly tilted relative to the surface of the grinding pad 43, the lower surface (dressing surface) of the dresser 51 can properly abut against the grinding pad 43.

[0040] The dressing of the grinding surface 43a is performed as follows: The grinding table 44 and the grinding pad 43 are rotated, and dressing fluid (e.g., pure water) is supplied to the grinding surface 43a of the grinding pad 43 via a dressing fluid supply nozzle (not shown). Further, the dresser 51 is rotated about its axis. The dresser 51 is pressed against the grinding surface 43a by a cylinder 54 with a predetermined dresser load, thereby bringing the dressing surface of the dresser 51 into contact with the grinding surface 43a. In this state, the dresser arm 55 is rotated, causing the dresser 51 in contact with the grinding pad 43 to swing in the approximate radial direction of the grinding pad 43. As a result, the grinding surface 43a of the grinding pad 43 is shaved away by the rotating dresser 51, thereby re-forming the fine irregularities of the grinding surface 43a.

[0041] A pad height sensor (surface height measuring machine) 58 for measuring the height of the grinding surface 43a is fixed to the dressing arm 55. Additionally, a sensor target 59 is fixed to the dressing shaft 53 opposite to the pad height sensor 58. Although the sensor target 59 is configured to move vertically and vertically integrally with the dressing shaft 53 and the dressing 51, the vertical position of the pad height sensor 58 is fixed.

[0042] The pad height sensor 58 is, for example, a displacement sensor, which detects the height of the dressing device 51 connected to the sensor target 59 by measuring the displacement of the sensor target 59. Since the dressing device 51 is in contact with the abrasive pad 43, the height (thickness of the abrasive pad 43) of the abrasive surface 43a of the abrasive pad 43 during the dressing process can be indirectly measured by measuring the dressing device 51. As the pad height sensor 58, various types of sensors such as linear scaling sensors, laser sensors, ultrasonic sensors, or eddy current sensors can be used.

[0043] The height of the abrasive surface 43a, measured by the pad height sensor 58, is determined in multiple defined areas along the radial direction of the abrasive pad 43. Figure 5 The height of the grinding surface 43a in the area (defined monitoring area) contacted by the lower surface (dressing surface) of the dresser 51 is measured using a pad height sensor 58. By measuring the height of the grinding pad 43 in multiple monitoring areas, the height profile of the grinding pad 43 (the cross-sectional shape of the height of the grinding surface 43a) can be obtained.

[0044] The pad height sensor 58 is connected to the dresser control unit 60, and the output signal of the pad height sensor 58 (i.e., the measured value of the height of the grinding surface 43a) is sent to the dresser control unit 60. The dresser control unit 60 has the following function: it obtains the outline of the grinding pad 43 based on the measured value of the height of the grinding surface 43a, and then determines whether the dressing of the grinding pad 43 is performed correctly.

[0045] The dressing unit 41 also includes: a table rotary encoder 61 for measuring the rotation angle of the grinding table 44 and the grinding pad 43; and a dressing rotary encoder 62 for measuring the rotation angle of the dressing device 51. These table rotary encoders 61 and dressing rotary encoders 62 are absolute encoders that measure the absolute value of the angles and are connected to the dressing device control unit 60. The dressing device control unit 60 can acquire information about the rotation angle of the grinding table 44 and the grinding pad 43, and even the rotation angle of the dressing device 51, when the height of the grinding surface 43a is measured by the pad height sensor 58.

[0046] A surface roughness measuring device 63 for measuring the surface roughness of the polishing pad 43 is disposed above the polishing pad 43. This surface roughness measuring device 63 can be a known non-contact type surface roughness measuring device, such as an optical type. The surface roughness measuring device 63 is connected to the dressing control unit 60, and the measured value of the surface roughness of the polishing pad 43 is sent to the dressing control unit 60.

[0047] The trimmer control unit 60 is connected to the device control unit 15. Besides receiving control signals from the device control unit 15 to perform trimmer processing on the polishing pad, it also performs polishing pad contour control processing, which will be described later. The device control unit 15 is connected to an input unit 65 such as a keyboard, microphone, or tablet computer; and an output unit 66 such as a display or speaker. The control program for controlling the operation of the substrate processing apparatus 10 can be pre-installed on the computer constituting the device control unit 15, or stored on a storage medium such as a CD-ROM or DVD-ROM. Alternatively, it can be installed on the device control unit 15 via the Internet. Furthermore, the device control unit 15 can be mounted on the substrate processing apparatus 10, or it can be configured to be connected to the substrate processing apparatus 10 via a network.

[0048] Next, refer to Figure 3 The swing of the dressing device 51 is explained below. The dressing device arm 55 (represented by a straight line for simplicity in the drawing) rotates clockwise and counterclockwise by a predetermined angle around point J. The position of point J corresponds to the pivot 56 (see reference). Figure 2 The center of rotation of the dresser 51 is located at the center of the abrasive pad 43 within the radius indicated by the arc L, due to the rotation of the dresser arm 55.

[0049] Figure 4 This is a partial enlarged view of the grinding surface 43a of the grinding pad 43. The swing range (swing amplitude L) of the dresser 51 is divided into multiple (in) Figure 4 In this example, there are seven scanning areas (oscillation intervals) S1 to S7. These scanning areas S1 to S7 are imaginary intervals pre-defined on the polishing surface 43a, arranged along the oscillation direction of the dresser 51 (i.e., the radial direction of the polishing pad 43). The dresser 51 moves across these scanning areas S1 to S7 with its center in the middle while dressing the polishing pad 43. The lengths of these scanning areas S1 to S7 may be the same or different.

[0050] Figure 5 This is an explanatory diagram showing the positional relationship between the scanning areas S1 to S7 and the monitoring areas M1 to M10 of the polishing pad 43. The horizontal axis of the diagram represents the distance from the center of the polishing pad 43. In this embodiment, seven scanning areas and ten monitoring areas are set as an example, but these numbers can be appropriately changed. In addition, in the area with a width equivalent to the radius of the trimmer 51 from both ends of the scanning area, it is more difficult to control the pad profile. Therefore, a monitoring exclusion width is set on the inner side (the area R1 to R3 from the center of the pad) and the outer side (the area R4 to R2 from the center of the pad), but it is not necessary to set an exclusion width.

[0051] The movement speed of the trimmer 51 when it oscillates on the polishing pad 43 is preset based on each scanning area S1 to S7, or can be adjusted appropriately. The movement speed distribution of the trimmer 51 represents the movement speed of the trimmer 51 in each scanning area S1 to S7.

[0052] The moving speed of the dresser 51 is one of the determining factors of the pad height profile of the polishing pad 43. The shearing rate of the polishing pad 43 represents the amount (thickness) of the polishing pad 43 removed by the dresser 51 per unit time. When the dresser moves at a constant speed, the thickness of the polishing pad 43 removed in each scanning area is usually different; therefore, the value of the shearing rate also varies based on each scanning area. However, the pad profile is generally preferably maintained at its initial shape; therefore, the moving speed is adjusted to reduce the difference in the amount of removal between scanning areas.

[0053] Here, increasing the moving speed of the dresser 51 means shortening the dwell time of the dresser 51 on the polishing pad 43, i.e., reducing the amount of material removed by the polishing pad 43. On the other hand, decreasing the moving speed of the dresser 51 means increasing the dwell time of the dresser 51 on the polishing pad 43, i.e., increasing the amount of material removed by the polishing pad 43. Therefore, by increasing the moving speed of the dresser 51 in a certain scanning area, the amount of material removed in that scanning area can be reduced; by decreasing the moving speed of the dresser 51 in a certain scanning area, the amount of material removed in that scanning area can be increased. As a result, the overall pad height profile of the polishing pad can be adjusted.

[0054] The trimmer control unit 60 is a general-purpose or dedicated computer device equipped with a control program that performs trimming processing on the polishing pad 43 and control processing of the polishing pad profile (described later). This control program can be pre-installed on the computer constituting the trimmer control unit 60, or stored on a storage medium such as a CD-ROM or DVD-ROM. Alternatively, it can be installed on the device control unit 15 via the Internet. Furthermore, the trimmer control unit 60 can be mounted on the substrate processing apparatus 10, or it can be configured to be connected to the substrate processing apparatus 10 via a network.

[0055] like Figure 6 As shown, the dresser control unit 60 includes: a dresser model setting unit 71, a basic contour calculation unit 72, a cutting rate calculation unit 73, an evaluation index setting unit 74, a moving speed calculation unit 75, a pad height detection unit 76, a dresser load setting unit 77, a pad height correction unit 78, a correction data storage unit 79, and a setting input unit 80. The dresser control unit 60 acquires the contour of the grinding pad 43 and sets the moving speed of the dresser 51 in the scanning area to the optimal value at a predetermined time.

[0056] The trimming model setting unit 71 sets a trimming model matrix S for calculating the wear amount of the abrasive pad 43 in the scanning area. The trimming model matrix S is an m-row n-column real number matrix when the number of segments of the monitoring area is set to m (10 in this embodiment) and the number of segments of the scanning area is set to n (7 in this embodiment), and is determined by various parameters described later.

[0057] The scanning speed of the trimmer in each scanning area set on the polishing pad 43 is set to V = [v1, v2, ..., v n And set the width of each scanned region to W = [w1, w2, ..., w] n When ], the dwell time of the trimmer (center) in each scanning area is expressed by the following formula.

[0058] T=W / V=[w1 / v1,w2 / v2,…,w n / v n ]

[0059] At this point, the pad wear in each monitoring area is set as U = [u1, u2, ..., u...]. m When calculating the pad wear amount U, the aforementioned trimming model matrix S and the dwell time T in each scanning area are used to perform the following matrix operation.

[0060] U=ST

[0061] In deriving the trimming model matrix S, various elements such as 1) the cutting rate model, 2) the trimmer diameter, and 3) the scanning speed control can be considered and appropriately combined. The cutting rate model is set based on the premise that each element of the trimming model matrix S is proportional to the dwell time in the monitoring area or proportional to the scraping distance (movement distance).

[0062] Furthermore, regarding the dresser diameter, the elements of the dressing model matrix S are set with the assumption that the diameter of dresser 51 is taken into account (the abrasive pad wears at the same cutting rate throughout the effective area of ​​the dresser) or not (only the cutting rate at the center of dresser 51 is considered). By taking the dresser diameter into account, an appropriate dressing model matrix can also be defined for dressers, for example, those with diamond particles coated in a ring. Regarding scanning speed control, the elements of the dressing model matrix S are set corresponding to whether the change in the dresser's moving speed is stepped or ramped. By appropriately combining these parameters, a cutting amount that better fits the actual state can be calculated based on the dressing model matrix S, thereby obtaining an accurate profile prediction value.

[0063] The pad height detection unit 76 correlates the height data of the polishing pad 43 continuously measured by the pad height sensor 58 with the measured coordinate data on the polishing pad, thereby detecting the pad height in each monitoring area. The correction of the pad height profile (pad height profile) corresponding to the dressing load will be described later.

[0064] The basic profile calculation unit 72 calculates the target profile (basic profile Htg(j)) of the pad height at the time of convergence at a specified time or when a specified condition is met (T1) (refer to...). Figure 7 The basic profile is used to calculate the target cutting amount by the moving speed calculation unit 75, which will be described later. The basic profile can be calculated based on the height distribution (Diff(j)) of the grinding pad in its initial state and the measured pad height, or it can be assigned as a set value. Alternatively, without setting a basic profile, the target cutting amount can be calculated to make the shape of the grinding pad 43 flat.

[0065] The target shearing amount is based on the pad height profile H, which represents the pad height of each monitored area at the current time (T2). p (j) [j = 1, 2…m] and the additionally defined convergence target for reducing wear A tg And calculated by the following formula:

[0066] min{H p (j)}-A tg

[0067] In addition, the target cutting amount for each monitored area can be calculated using the following formula, taking into account the aforementioned basic contour:

[0068] min{H p (j)}-A tg +Diff(j)

[0069] The shearing rate calculation unit 73 calculates the shearing rate of the trimmer in each monitoring area. For example, the shearing rate can be calculated based on the slope of the change in pad height in each monitoring area.

[0070] The evaluation index setting unit 74 calculates and corrects the optimal dwell time (oscillation time) in the scanning area using the evaluation index described later, thereby optimizing the movement speed of the dresser in each scanning area. This evaluation index is based on 1) the deviation from the target cutting amount, 2) the deviation from the dwell time under the baseline processing method, and 3) the speed difference between adjacent scanning areas. It is the dwell time T = [w1 / v1, w2 / v2, ..., w...] in each scanning area. n / v n The function is defined as follows: Furthermore, by determining the dwell time T in each scanning region to minimize this evaluation metric, the movement speed of the trimmer is optimized.

[0071] 1) Deviation from the target cutting amount

[0072] When the target cutting amount of the dressing is set to U0 = [U 01 U 02 、…、U 0m When [the wear is] measured, the square of the difference between this value and the pad wear amount U (=ST) in each of the aforementioned monitoring areas is calculated (|U-U0|). 2 This allows for the calculation of the deviation from the target cutting amount. Furthermore, the target profile used to determine the target cutting amount can be determined at any time after the start of use of the grinding pad, or it can be determined based on a manually set value.

[0073] 2) Deviation from the dwell time under the benchmark processing method

[0074] like Figure 8 As shown, the square of the difference (ΔT) between the moving speed (reference speed (reference dwell time T0) of the trimmer based on the reference processing method set in each scanning region and the moving speed (trimmer dwell time T) of the trimmer in each scanning region is calculated. 2 =|T-T0| 2 This allows for the calculation of the deviation from the dwell time under a reference processing method. Here, the reference speed refers to the moving speed at which a flat cutting rate is expected to be obtained in each scanning area, and is a value obtained in advance through experiments and simulations. When the reference speed is obtained through simulation, it can be calculated as, for example, proportional to the scraping distance (dwell time) of the dresser and the cutting amount of the abrasive pad. Furthermore, the reference speed can be appropriately updated according to the actual cutting rate when using the same abrasive pad.

[0075] 3) Velocity difference between adjacent scanning regions

[0076] In the polishing apparatus of this embodiment, the effects of rapid changes in moving speed on the polishing apparatus are also suppressed by suppressing the speed difference between adjacent scanning regions. That is, the square value of the speed difference between adjacent scanning regions (|ΔV) is calculated. inv | 2 This allows for the calculation of an index representing the velocity difference between adjacent scan regions. Here, for example... Figure 8 As shown, the difference in velocity between scanning areas can be represented by the difference in reference velocity (Δ). inv ) and the moving speed of the trimmer (Δ v Any one of the following. Furthermore, since the width of the scanning area is a fixed value, the speed difference index depends on the dwell time of the trimmer in each scanning area.

[0077] The evaluation index formulation department 74 defines the evaluation index J based on these three indicators, as shown in the following formula:

[0078] J=γ|U-U0| 2 +λ|T-T0| 2 +η|ΔV inv | 2

[0079] Here, the first, second, and third terms on the right side of the evaluation index J are respectively caused by the deviation from the target cutting amount, the deviation from the dwell time under the benchmark processing method, and the speed difference between adjacent scanning areas, and all depend on the dwell time T of the dresser in each scanning area.

[0080] Furthermore, in the moving speed calculation unit 75, an optimization calculation is performed to minimize the value of the evaluation index J, the dwell time T of the trimmer in each scanning area is calculated, and the moving speed of the trimmer is corrected. As the optimization calculation method, quadratic programming can be used, or simulation-based convergence calculation and PID control can be used.

[0081] In the aforementioned evaluation index J, γ, λ, and η are specified weighted values ​​that can be appropriately changed during the use of the same polishing pad. By changing these weighted values, the indicators that should be emphasized can be appropriately adjusted according to the characteristics of the polishing pad, the dresser, and the operating conditions of the device.

[0082] Furthermore, when calculating the moving speed of the trimmer, it is preferable to set the total trimming time to be within a specified value. Here, the total trimming time refers to the moving time based on the entire swing range of the trimmer (scanning areas S1 to S7 in this embodiment). When the total trimming time (the time required for trimming) becomes longer, it may affect other strokes such as the substrate grinding stroke and the transport stroke. Therefore, it is preferable to appropriately correct the moving speed in each scanning area so that this value does not exceed the specified value. In addition, due to the constraints of the device mechanism, it is also preferable to set the moving speed of the trimmer so that the maximum (and minimum) moving speed of the trimmer and the ratio of the maximum speed (minimum speed) to the initial speed are within a set value.

[0083] Furthermore, in cases where the appropriate dressing conditions are unclear due to the combination of a new dresser and a grinding pad, or in cases where the dresser's reference speed (reference dwell time T0) has not yet been determined after the dresser and grinding pad have just been replaced, the moving speed calculation unit 75 can also determine the evaluation index J (hereinafter) by applying only the condition of deviation from the target cutting amount, thereby optimizing the moving speed of the dresser in each scanning area (initial setting).

[0084] J = |U-U0| 2

[0085] The dresser load setting unit 77 sets the load (dresser load) applied from the dresser 51 to the grinding surface 43a of the grinding pad 43, and adjusts the dresser load on the grinding pad 43 by changing the position of the cylinder 54. When the dresser load changes from a reference value (reference dresser load), the amount of pressure applied to the grinding pad 43 by the dresser 51 changes. For example, when the dresser load increases, the grinding pad 43 is pressed further, and therefore the pad height decreases. Conversely, when the dresser load decreases, the pad height of the grinding pad 43 increases. As a result, because the position of the grinding surface 43a changes, the height of the grinding pad 43 cannot be calculated (to reduce wear).

[0086] To compensate for the change in pad height caused by the change in dresser load, the pad height correction unit 78 calculates a correction value for the pad height corresponding to the amount of change in dresser load. The amount of change in pad height may vary depending on the radial position of the abrasive pad 43; therefore, it is configured to calculate multiple correction values ​​for the pad height based on the radial position of the abrasive pad 43.

[0087] Figure 9 This is a graph illustrating an example of the distribution of the polishing pad height under varying loads on the dresser. The horizontal axis represents the radial position of the polishing pad, and the point where it intersects the vertical axis indicates a zero radial position (the center of the polishing pad). Furthermore, the pad height represents the relative height with respect to a preset reference value; a larger value indicates a higher polishing surface 43 of the polishing pad 43. Figure 9 The graph shows that as the dresser load increases, the pad height decreases. Additionally, it indicates that the larger the radius (closer to the outer periphery of the grinding pad 43), the lower the pad height. These pad height data are for each dresser load at multiple radius locations (in... Figure 9 In the example, seven points (50mm from the center of the grinding pad, spaced at intervals of 50mm up to 350mm) are measured in advance by testing and stored in the calibration data storage unit 79 as a reference data for distinguishing the pad height based on the load / radius.

[0088] The load / radius differentiation pad height reference data can be measured statically (with the grinding table 44 and dresser 51 stopped) or dynamically (with the grinding table 44 and dresser 51 rotated, and the dresser 51 oscillating, in a state close to the actual dressing of the grinding pad 43). In the case of dynamic measurement, it is preferable to be able to continuously acquire data at multiple radius positions. Furthermore, the load and radius positions are not limited to the examples described above; they can be appropriately changed as long as they are close to the actual usage range, but it is preferable that there are three or more load and radius positions respectively.

[0089] The calculation of the pad height correction amount in the pad height correction unit 78 can be performed as follows, for example: The adjuster load set in the adjuster load setting unit 77 is set to DF. x At that time, the load / radius differentiation pad height reference data stored in the calibration data storage unit 79 is read from the DF. x Two close dresser loads (DF1, DF2) and corresponding pad height reference data (PadH1, PadH2) are used, and the value relative to the set dresser load DF is calculated by interpolation using the following formula. x Pad height PadH x .

[0090] PadH x =(PadH1-PadH2) / (DF1-DF2)×(DF x -DF2)+PadH2

[0091] Where DF1 < DF x <DF2

[0092] In addition to linear interpolation as shown in the above formula, interpolation can also be performed, for example, by splines.

[0093] For example, Figure 9 Thus, for every 10N trimmer load, the load / radius differentiation pad height reference data is stored in the calibration data storage unit 79, and the DF... x With the load set to 15N, DF1 is 10N and DF2 is 20N. Therefore, the pad height reference data corresponding to the dresser loads of 10N and 20N is read from the calibration data storage unit 79, and the pad height H is calculated for each radius position of the grinding pad. x The pad height correction unit 78 calculates the pad height PadH, calculated by the above formula, at each radial position of the grinding pad for both the specified reference load and the dresser load (measurement load) used for actual dressing. x The calculated pad height PadH x The value is stored in the correction data storage unit 79.

[0094] Figure 10 The graph is a plot of the pad height values ​​calculated by interpolation along the radius of the grinding pad, showing the pad height PadH under a reference load (e.g., 25 N). bDF PadH under the measured load (e.g., 15 N) mDF Here, the reference load is often constant and independent of the measured load; therefore, it can be stored in the calibration data storage unit 79 based on pre-calculation. This shortens the pad height calibration process.

[0095] The pad height correction unit 78 calculates the correction amount PadH for each radius position of the grinding pad using the following formula. delta (r), the correction amount PadH delta (r) is used to determine the pad height PadH based on the measured load. mDF (r) converted to baseline load PadH bDF (r).

[0096] PadH delta (r)=PadH mDF (r)-PadH bDF (r)

[0097] Next, the pad height correction unit 78 performs interpolation processing based on the correction amount values ​​obtained for each radius position, thereby generating a function F(DF, r) of the correction amount relative to the radius position of the grinding pad.

[0098] Figure 11 This is a graph of an example of the function F(DF, r) representing the correction amount, where each point represents the correction amount PadH calculated using the above formula. delta The discrete values ​​of (r) (e.g., seven points spaced 50 mm from the center of the abrasive pad up to 350 mm) are represented by a curve, which shows an example of a function F obtained by spline interpolation based on these discrete values, and a straight line, which shows an example of a function F obtained by linear interpolation using adjacent discrete values. While an appropriate interpolation formula can be used to obtain function F, linear interpolation is preferred when the difference between adjacent discrete values ​​is large.

[0099] Here, the formula for calculating the pad height measurement data and correction value is preferably determined based on the type (hardness) of the abrasive pad used for dressing, or it can be determined according to each combination of abrasive pad and dressing tool. Alternatively, the formula for calculating the pad height measurement data and correction value can be determined inherently on the grinding table.

[0100] The pad height correction unit 78 uses the function F(DF, r) obtained as described above, based on the height of the abrasive pad (measurement height) PadH measured at a certain radius position. measure PadH(r) is the pad height (pad height readjusted to reference load) used for pad control, calculated by the following formula.

[0101] PadH(r)=PadH measure (r)+PadH delta (r)

[0102] The input unit 80 is set to an input device such as a keyboard or mouse, and inputs various parameters such as the values ​​of each component of the trimming model matrix S, the setting of constraints, the shear rate update cycle, and the movement speed update cycle. Furthermore, a memory (not shown) provided in the trimmer control unit 60 stores various data such as program data for operating the structural elements constituting the trimmer control unit 60, the values ​​of each component of the trimming model matrix S, the target profile, the weighted value of the evaluation index J, and the set value of the trimmer's movement speed.

[0103] Figure 12 This is a flowchart illustrating the sequence of grinding and cleaning multiple substrates W while controlling the movement speed of the trimmer after replacing the grinding pad. When the device control unit 15 detects that the grinding pad 43 has been replaced through processes such as resetting the pad usage time (step S10), the trimming model setting unit 71 derives the trimming model matrix S by considering parameters such as the cutting rate model, trimmer diameter, and scanning speed control (step S11). Furthermore, if the grinding pads 43 before and after replacement are of the same type, the same trimming model matrix can continue to be used.

[0104] Next, it is determined whether to calculate the reference speed of the dresser (for example, whether an instruction indicating that a reference speed calculation has been input via the setting input unit 80) (step S12). If the reference speed is calculated, in the moving speed calculation unit 45, the moving speed (dwell time T) of the dresser in each scanning area is set by the target cutting amount U0 of the dresser and the pad wear amount U in each monitoring area, so that the following evaluation index J is minimized (step S13). The calculated reference speed can also be set as the initial value of the moving speed.

[0105] J = |U-U0| 2

[0106] Subsequently, when substrate W is set, grinding and cleaning processes are performed on substrate W (step S14), and the basic contour is calculated if specified conditions are met. Additionally, if other conditions are met, the cutting rate is calculated or the dressing speed is updated (see [reference]). Figure 13 The pad replacement indicator can be determined based on the number of substrates W being processed, or it can be automatically determined based on the height of the polishing pad.

[0107] Figure 13 This is a flowchart illustrating the processing sequence of substrate W. When a substrate processing start command is issued in the device control unit 15 (step S30), the trimmer control unit 60 determines whether the specified conditions are met. Figure 13In the example, this refers to whether the cutting rate calculation cycle has been reached (e.g., grinding of a specified number of substrates W) (step S31). If it has been reached, the reference load pad height (described later) is calculated (step S32), and then the cutting rate of the trimmer in each scanning area is calculated and updated in the cutting rate calculation unit 73 (step S33). On the other hand, if the condition is not met, the cutting rate update process is skipped.

[0108] Furthermore, the trimmer control unit 60 determines whether the specified conditions are met (in... Figure 13 In the example, this refers to whether the moving speed update cycle has been reached (e.g., grinding a specified number of substrates W) (step S34). If it has been reached, the reference load pad height is calculated (step S35). In the moving speed setting unit 75, the moving speed of the trimmer in each scanning area is optimized by calculating the dwell time of the trimmer that minimizes the evaluation index J (step S36). Then, the value of the optimized moving speed is set, and the moving speed of the trimmer is updated (trimming process) (step S37).

[0109] Figure 14 This is a flowchart illustrating the calculation process of the reference load pad height in steps S35 (and S32). The pad height correction unit 78 reads the measured values ​​of the pad height stored in the correction data storage unit 79 (step S50). Next, the pad height correction unit 78 calculates the average pad height for each monitoring area by averaging the measured values ​​at the corresponding radius positions for each monitoring area of ​​the grinding pad (step S51), and uses this as the measured value PadH. measure (r)(Step S51). Alternatively, instead of calculating the average value for each monitored area, the measured values ​​at each radius location can be used as PadH. measure (r).

[0110] Next, the pad height correction unit 78 reads the trimmer load (measured load) DF set by the trimmer load setting unit 77. x Two close dresser loads (DF1, DF2) and corresponding pad height reference data (PadH1, PadH2) are read (step S52). Similarly, two dresser loads close to the reference load and their corresponding pad height reference data are read.

[0111] The pad height correction unit 78 calculates the pad height corresponding to the reference load and the measured load for each radius position of the grinding pad by interpolation based on the read dresser load and pad height reference data (step S53). Then, based on the pad height information obtained by interpolation, it generates a calculation formula F(DF, r) for the correction amount of the pad height relative to the measured load (step S54).

[0112] Next, the pad height correction unit 78 calculates the measured value PadH of the pad height based on the obtained calculation formula F(DF, r). measure The correction value PadH corresponding to the radius position of (r) delta (r)(step S55), and calculate the reference load pad height PadH(r) using this correction amount (step S56).

[0113] exist Figure 13 In the process, when the reference load pad height PadH(r) is calculated and the calculation ends according to the calculation conditions, the substrate W provided on the substrate polishing unit is polished (step S38). The polishing of the substrate W can be carried out until the film thickness is preset or until the substrate layer is exposed. When the substrate W after polishing is removed from the substrate polishing unit, the trimmer control unit 60 drives the trimmer 51 to perform trimming of the polishing pad 43 according to the set trimming process program (step S39). When trimming of the polishing pad 43 is performed, the height of the polishing surface 43a (pad height) is measured by the pad height sensor 58 (step S40), and the measured data is stored in the memory in the trimmer control unit 60 (step S41). The polished substrate W is sent to the cleaning unit 14 (first substrate cleaning device 30, second substrate cleaning device 31, substrate drying device 32) to perform cleaning / drying on the substrate (step S42), and is taken out to the outside by the substrate processing device 10.

[0114] exist Figure 12 In the process, when substrate processing 14 ends, it is determined whether the conditions for obtaining the basic contour are met (e.g., grinding a specified number of substrates W) (step S15). If the conditions are met, the target contour (basic contour) of the pad height at convergence is calculated in the basic contour calculation unit 72 (step S16). If the conditions for obtaining the basic contour are not met (if a specified number of substrates W are not ground), the process returns to step S14, and the next substrate W is ground and cleaned.

[0115] Once the basic contour has been set, the next substrate W is subjected to a grinding / cleaning process (step S17). This grinding / cleaning process is related to... Figure 13 The flowchart is the same as that described above, so detailed explanation is omitted. Then, substrate processing continues in step S17 until the amount of material removed from the polishing pad becomes larger than the replacement reference value (step S18). Then, if the height of the polishing pad is less than the replacement reference value (in step S18, "Yes"), the device control unit 15 instructs the operator to replace the polishing pad via the output unit 66 (step S19).

[0116] Figure 15This is a graph illustrating an example of the relationship between the pad height and the radius of the grinding pad when the dresser load is varied from 12N to 24N. Without pad height correction ( Figure 15 (a) When the dresser load increases to 24N, the measured value of the pad height profile (compared to the case of 12N) decreases, therefore the dresser's moving speed cannot be properly calculated. In contrast, with pad height correction ( Figure 15 (b) Even if the trimmer load increases, the measured value of the pad height profile remains almost unchanged (compared to the case of 12N), thus enabling the trimmer's moving speed to be calculated appropriately.

[0117] The thickness of the polishing pad 43 may vary depending on the pad's thickness, elastic modulus (pad stiffness), and cross-sectional area. Therefore, it is preferable to set correction data for the reference load for each type of polishing pad. In addition, the polishing pad 43 wears slightly each time it is dressed, so when the number of dressings increases, there may be a situation where the amount of wear changes significantly compared to the thickness of the polishing pad immediately after replacement.

[0118] Therefore, the pad height can be calculated by adding an adjustment factor f(t) corresponding to the pad's usage time (or the amount of pad wear) each time the reference load pad height PadH(r) is calculated (step S56). In this case, the reference load pad height PadH(r) can be calculated using the following formula:

[0119] PadH(r)=PadH measure (r)+f(t)×PadH delta (r)

[0120] Here, the adjustment coefficient f(t) can be determined in advance through testing. It is a function corresponding to the usage time t of the polishing pad, but it can also be determined by taking the number of times the polishing pad is treated by the dresser as the independent variable.

[0121] The above-described embodiments are intended to enable those skilled in the art to carry out the invention. Various modifications of the above-described embodiments can obviously be implemented by those skilled in the art, and the technical concept of the invention can also be applied to other embodiments. The invention is not limited to the described embodiments, but is interpreted as encompassing the maximum scope of the technical concept as defined by the scope of protection claimed by the invention.

Claims

1. A substrate processing apparatus for grinding a substrate by causing the substrate to slide into contact with a grinding member, the substrate processing apparatus being characterized by comprising: A dresser that dresses the grinding member by oscillating on it, and the dresser is able to adjust the oscillation speed in multiple scanning areas set radially on the grinding member; A height sensor that measures the height of the trimmer; A pad height detection unit generates a pad profile by measuring the surface height of the grinding member in contact with the dresser along the radial direction of the grinding member based on the height of the dresser measured by the height sensor. The dresser load setting unit sets the dresser load applied by the dresser to the grinding member; A pad height correction unit, which extends to multiple points along the radial direction, calculates a correction amount for the surface height of the grinding member corresponding to the variation in the dresser load relative to a reference load, and corrects the measured value of the surface height at multiple points along the radial direction of the grinding member using the correction amount, thereby correcting the pad profile; and The movement speed calculation unit adjusts the oscillation speed of the trimmer in each scanning area based on the corrected pad profile. The correction amount has different values ​​in the radial direction of the grinding component.

2. The substrate processing apparatus according to claim 1, characterized in that, It includes a calibration data storage unit that stores multiple pad height reference data along the radial direction of the grinding member, corresponding to multiple reference dresser loads. The pad height correction unit interpolates and calculates the correction amount of the surface height based on the pad height reference data corresponding to the reference dresser load that is close to the set dresser load and the pad height reference data corresponding to the reference dresser load that is close to the reference load.

3. The substrate processing apparatus according to claim 2, characterized in that, The pad height reference data is set according to each type of the grinding component and / or each type of the dressing tool.

4. The substrate processing apparatus according to claim 1, characterized in that, The pad height correction unit corrects the surface height by means of a correction coefficient corresponding to the usage time of the grinding component or the number of times the dresser is dressed.

5. The substrate processing apparatus according to claim 1, characterized in that, The pad height detection unit measures the surface height of the grinding component in multiple pre-defined monitoring areas along the radial direction of the grinding component.

6. The substrate processing apparatus according to claim 1, characterized in that, have: The trimming model matrix definition department defines the trimming model matrix, which is defined by multiple monitoring areas, scanning areas, and trimming models. as well as The evaluation index setting unit uses the trimming model matrix and the oscillation speed or dwell time in each scanning area to calculate the height profile prediction value, and sets the evaluation index based on the difference between the predicted value and the target value of the height profile of the grinding component. The moving speed calculation unit calculates the swing speed of the trimmer in each scanning area based on this evaluation index.

7. A method for dressing a grinding component, wherein a dresser is oscillated on a grinding component used in a substrate grinding apparatus to dress the grinding component, the method being characterized in that the dresser can adjust its oscillation speed in a plurality of scanning areas set on the grinding component along the oscillation direction, the method comprising: The trimmer height measurement step involves measuring the height of the trimmer using a height sensor. The pad height measurement step generates a pad profile by measuring the surface height of the grinding member in contact with the dressing member radially along the grinding member based on the height of the dressing member measured by the height sensor. The dressing load setting step sets the dressing load applied by the dressing to the grinding component; The pad height correction step involves calculating a correction amount for the surface height of the grinding component corresponding to the variation in the dresser load relative to a reference load at multiple points along the radial direction, and correcting the measured value of the surface height at multiple points along the radial direction of the grinding component using the correction amount, thereby correcting the pad profile; and The movement speed calculation step involves adjusting the oscillation speed of the trimmer in each scanning area based on the corrected pad profile. The correction amount has different values ​​in the radial direction of the grinding component.

8. A storage medium, non-transitory and readable by a computer, characterized in that, The storage medium contains computer-executable code for a polishing apparatus that causes a dresser to oscillate on a polishing component for polishing a substrate to dress the component, and the dresser is capable of adjusting the oscillation speed in multiple scanning areas set on the polishing component along the oscillation direction. The code is used to instruct the computer to perform the following steps: The trimmer height measurement step involves measuring the height of the trimmer using a height sensor. The pad height measurement step generates a pad profile by measuring the surface height of the grinding member in contact with the dressing member radially along the grinding member based on the height of the dressing member measured by the height sensor. The dressing load setting step sets the dressing load applied by the dressing to the grinding component; The pad height correction step involves calculating a correction amount for the surface height of the grinding component corresponding to the variation of the dresser load relative to the reference load at multiple points along the radial direction, and correcting the measured value of the surface height at multiple points along the radial direction of the grinding component with the correction amount, thereby correcting the pad profile. as well as The movement speed calculation step involves adjusting the oscillation speed of the trimmer in each scanning area based on the corrected pad profile. The correction amount has different values ​​in the radial direction of the grinding component.

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