JP2021160025A - Polishing device and polishing method - Google Patents

Abstract

To provide a polishing device that can identify a reference position of a wafer angle accurately during polishing a wafer.SOLUTION: A polishing device includes a polishing table 3, a polishing head 1, a rotation mechanism and a reference position detection device 200. A control device 9 calculates a relative angle of a reference position to the polishing head 1 on the basis of a first signal relating to a rotation angle of the polishing head 1 which is acquired from a rotation angle detector 41 and a second signal relating to a rotation angle of the reference position which is acquired from the reference position detection device 200.SELECTED DRAWING: Figure 6

Description

The present invention relates to a polishing apparatus and a polishing method.

Chemical mechanical polishing (CMP) is known as a technique in the manufacturing process of semiconductor devices. The polishing apparatus for performing CMP includes a polishing table for supporting the polishing pad and a polishing head for holding the wafer.

When polishing a wafer using such a polishing device, the wafer is pressed against the polishing surface of the polishing pad with a predetermined pressure while holding the wafer by the polishing head. At this time, by moving the polishing table and the polishing head relative to each other, the wafer is in sliding contact with the polishing surface, and the surface of the wafer is polished.

Japanese Unexamined Patent Publication No. 2016-5991 Japanese Unexamined Patent Publication No. 2005-288572 Japanese Unexamined Patent Publication No. 2001-38614 JP-A-2019-87603

Generally, a wafer is required to have a uniform film thickness distribution over its entire surface. When the initial film thickness differs in the radial direction of the wafer, the polishing rate (removal) along the radial direction of the wafer is adjusted by adjusting the pressure in a plurality of concentric pressure chambers formed by the elastic films that abut the wafer. It is possible to adjust the rate).

Depending on the characteristics of the film forming apparatus and the like, the initial film thickness of the wafer to be polished may vary along the circumferential direction of the wafer. In particular, the initial film thickness tends to vary along the circumferential direction at the peripheral edge of the wafer. In order to reduce such variations in film thickness, a method may be adopted in which a portion of the wafer having a thick film is positively polished to improve the uniformity of the film thickness distribution in the circumferential direction of the wafer.

In this case, it is necessary to determine the relative angle between the wafer and the polishing head in order to polish a specific part of the wafer. The reference position of the circumferential angle (that is, the wafer angle) of the wafer is, for example, the position of a notch formed on the peripheral edge of the wafer. However, during wafer polishing, the wafer (ie, the reference position of the wafer angle) may shift in the direction of rotation of the polishing head with respect to the polishing head due to the frictional force acting between the wafer and the polishing pad. .. In this case, since the relative angle between the predetermined wafer and the polishing head also deviates, it is not possible to accurately polish a specific portion of the wafer.

Therefore, an object of the present invention is to provide a polishing apparatus and a polishing method capable of accurately specifying a reference position of a wafer angle during polishing of a wafer.

In one aspect, a polishing table that supports the polishing pad, a polishing head that presses the substrate against the polishing surface of the polishing pad, a rotation mechanism that rotates the polishing head about its axis, and during polishing of the substrate. A reference position detection device that detects a reference position of an angle in the circumferential direction of the substrate, a rotation angle detector that detects the rotation angle of the polishing head, and the reference position during polishing of the substrate are obtained from the reference position detection device. A polishing device comprising a control device to acquire is provided. The control device is based on the first signal regarding the rotation angle of the polishing head acquired from the rotation angle detector and the second signal regarding the rotation angle of the reference position acquired from the reference position detection device. The relative angle of the reference position with respect to the polishing head is calculated.

In one aspect, the control device determines the relative angle between the reference position and the polishing head before the start of polishing of the substrate, based on the rotation angle of the polishing head obtained from the rotation angle detector. The amount of change in the relative angle is calculated based on the reference position during polishing of the substrate obtained from the reference position detection device, and the relative angle is corrected based on the calculated amount of change.
In one aspect, the control device inputs the data measured by the reference position detecting device into the model constructed by the machine learning algorithm, and outputs a determination result indicating the position of the reference position from the model.
In one aspect, the polishing head comprises an elastic film that presses the substrate against the polishing surface and retainers that are arranged so as to surround the elastic film and come into contact with the polishing surface. The reference position detecting device is arranged adjacent to the elastic film.

In one aspect, the reference position detection device includes an image acquisition device arranged in a pressure chamber of the elastic membrane.
In one aspect, the reference position detector comprises a non-contact distance sensor or an acoustic sensor located outside the retainer ring.
In one aspect, the reference position detector comprises a non-contact distance sensor, an acoustic sensor, or a vibration sensor located in the pressure chamber of the elastic membrane.

In one aspect, the reference position detector comprises a non-contact distance sensor, an acoustic sensor, or a vibration sensor embedded inside the ring member of the retainer ring.
In one aspect, the reference position detector comprises a non-contact distance sensor, an acoustic sensor, or a vibration sensor attached to the drive ring of the retainer ring.
In one aspect, the reference position detector comprises a non-contact distance sensor embedded in the polishing table.

In one aspect, the film thickness distribution information of the substrate is acquired, the rotation angle of a specific portion on the substrate to be adjusted is determined with reference to the reference position of the angle in the circumferential direction of the substrate, and the rotation angle of the specific portion of the substrate is determined. During polishing, the reference position of the circumferential angle of the substrate was detected, and the specific portion was located at a specific position on the polishing table based on the detected reference position information and the rotation angle of the specific portion. Polishing methods are provided that sometimes adjust the polishing pressure.

In one aspect, there is provided a polishing method that detects a reference position of an angle in the circumferential direction of the substrate during polishing of the substrate and determines the timing at which the polishing head rises based on the information of the detected reference position. Will be done.

The control device is based on the data acquired from the reference position detection device that detects the reference position of the angle in the circumferential direction of the substrate and the rotation angle detector that detects the rotation angle of the polishing head during polishing of the substrate. The relative angle of the reference position with respect to the polishing head is calculated. Therefore, the polishing apparatus can accurately identify the reference position of the wafer angle during the polishing of the wafer.

It is a schematic diagram which shows one Embodiment of a polishing apparatus. It is a schematic cross-sectional view of a polishing head. 3 (a), 3 (b), and 3 (c) are diagrams showing an example of the film thickness distribution along the circumferential direction of the wafer at a position 3 mm inside from the outermost end of the wafer. .. It is a figure which showed the positional relationship seen from the upper side of the polished surface. It is a figure which shows one Embodiment of the polishing method using a polishing apparatus. It is a figure which shows one Embodiment of the notch detection device. It is a figure which shows the notch detection device arranged at equal intervals along the circumferential direction of the edge pressure chamber of an elastic film. It is a figure which shows the flow which corrects the relative angle between a wafer and a polishing head by a control device. It is a figure for demonstrating the method of constructing a trained model. It is a figure which shows the notch detection device arranged outside the retainer ring. It is a figure which shows the notch detection device arranged outside the retainer ring. It is a figure which shows the other embodiment of the notch detection apparatus. It is a figure which shows the holding ring which holds a plurality of notch detection devices. It is a figure which shows still another embodiment of the notch detection apparatus. It is a figure which shows still another embodiment of the notch detection apparatus. It is a figure which shows still another embodiment of the notch detection apparatus. It is a figure which shows the scribe line of the pattern formed on the wafer. 18 (a) to 18 (c) are views showing how the wafer is cracked.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding components are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a schematic view showing an embodiment of a polishing apparatus. As shown in FIG. 1, the polishing device is a polishing head (board holding device) 1 that holds and rotates a wafer W, which is an example of a substrate, a polishing table 3 that supports the polishing pad 2, and a polishing pad 2. It includes a polishing liquid supply nozzle 5 for supplying a liquid (slurry).

The polishing head 1 is configured so that the wafer W can be held on the lower surface thereof by vacuum suction. The polishing head 1 and the polishing table 3 rotate in the same direction, and in this state, the polishing head 1 presses the wafer W against the polishing surface 2a of the polishing pad 2. The polishing liquid is supplied onto the polishing pad 2 from the polishing liquid supply nozzle 5, and the wafer W is polished by sliding contact with the polishing pad 2 in the presence of the polishing liquid.

The polishing table 3 is connected to a table motor 13 arranged below the table shaft 3a via a table shaft 3a, and is rotatable around the table shaft 3a. A polishing pad 2 is attached to the upper surface of the polishing table 3, and the upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the wafer W. By rotating the polishing table 3 by the table motor 13, the polishing surface 2a moves relative to the polishing head 1. Therefore, the table motor 13 constitutes a polishing surface moving mechanism that moves the polishing surface 2a in the horizontal direction.

The polishing head 1 is connected to a polishing head shaft 11, and the polishing head shaft 11 moves up and down with respect to the head arm 16 by a vertical movement mechanism 27. The vertical movement of the polishing head shaft 11 raises and lowers the entire polishing head 1 with respect to the head arm 16 for positioning. A rotary joint 25 is attached to the upper end of the polishing head shaft 11.

The vertical movement mechanism 27 that moves the polishing head shaft 11 and the polishing head 1 up and down includes a bridge 28 that rotatably supports the polishing head shaft 11 via a bearing 26, a ball screw 32 attached to the bridge 28, and a support column 30. A support base 29 supported by the support base 29 and a servomotor 38 provided on the support base 29 are provided. The support base 29 that supports the servomotor 38 is fixed to the head arm 16 via the support column 30.

The ball screw 32 includes a screw shaft 32a connected to the servomotor 38 and a nut 32b into which the screw shaft 32a is screwed. The polishing head shaft 11 moves up and down integrally with the bridge 28. Therefore, when the servomotor 38 is driven, the bridge 28 moves up and down via the ball screw 32, which causes the polishing head shaft 11 and the polishing head 1 to move up and down. The head arm 16 is provided with a polishing head height sensor 39 facing the bridge 28. The polishing head height sensor 39 measures the height of the polishing head 1 from the position of the bridge 28 that moves up and down integrally with the polishing head 1.

Further, the polishing head shaft 11 is connected to the rotary cylinder 12 via a key (not shown). The rotary cylinder 12 is provided with a timing pulley 14 on the outer peripheral portion thereof. A polishing head motor 18 is fixed to the head arm 16, and the timing pulley 14 is connected to a timing pulley 20 provided on the polishing head motor 18 via a timing belt 19. Therefore, by rotationally driving the polishing head motor 18, the rotary cylinder 12 and the polishing head shaft 11 are integrally rotated via the timing pulley 20, the timing belt 19, and the timing pulley 14, and the polishing head 1 is centered on the axis thereof. Rotate as. The polishing head motor 18, the timing pulley 20, the timing belt 19, and the timing pulley 14 constitute a rotation mechanism for rotating the polishing head 1 about its axis. The head arm 16 is supported by an arm shaft 21 rotatably supported by a frame (not shown).

The polishing head 1 can hold the wafer W on the lower surface thereof. The head arm 16 is configured to be rotatable around the arm shaft 21, and the polishing head 1 holding the wafer W on the lower surface moves from the delivery position of the wafer W to the upper position of the polishing table 3 by the rotation of the head arm 16. Will be done. The polishing head 1 and the polishing table 3 are rotated, respectively, and the polishing liquid is supplied onto the polishing pad 2 from the polishing liquid supply nozzle 5 provided above the polishing table 3. Then, the wafer W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1, and the wafer W is brought into sliding contact with the polishing surface 2a of the polishing pad 2 in the presence of the polishing liquid. The surface of the wafer W is polished by the chemical action of the chemical components of the polishing solution and the mechanical action of the abrasive grains contained in the polishing solution.

Next, the details of the polishing head 1 will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view of the polishing head 1. As shown in FIG. 2, the polishing head 1 includes a head main body 102 that presses the wafer W against the polishing surface 2a, and a retainer ring 103 that is arranged so as to surround the wafer W. The head body 102 and the retainer ring 103 are configured to rotate integrally with the rotation of the head shaft 11. The retainer ring 103 is configured to be vertically movable independently of the head main body 102.

The head body 102 includes a circular flange 141, a spacer 142 attached to the lower surface of the flange 141, and a carrier (base plate) 143 attached to the lower surface of the spacer 142. The flange 141 is connected to the polishing head shaft 11. The carrier 143 is connected to the flange 141 via the spacer 142, and the flange 141, the spacer 142, and the carrier 143 rotate integrally and move up and down.

An elastic film 110 that comes into contact with the back surface of the wafer W is connected to the lower surface of the head body 102. The elastic membrane 110 has a plurality of (six in FIG. 2) annular peripheral walls 114a, 114b, 114c, 114d, 114e, 114f, and these peripheral walls 114a to 114f are arranged concentrically.

Due to these peripheral walls 114a to 114f, six pressure chambers, that is, a circular central pressure chamber 116a located at the center and an annular edge pressure chamber 116f located at the outermost periphery, are formed between the elastic film 110 and the head body 102. And intermediate pressure chambers 116b, 116c, 116d, 116e located between the central pressure chamber 116a and the edge pressure chamber 116f are formed.

These pressure chambers 116a to 116f are connected to the pressure adjusting device 165 via a rotary joint 182, and a fluid (for example, air) passes through a fluid line 173 extending from the pressure adjusting device 165 to each of the pressure chambers 116a to 116f. ) Is being supplied. The pressure adjusting device 165 is connected to the control device 9 so that the pressures in these six pressure chambers 116a to 116f can be adjusted independently.

Further, the pressure adjusting device 165 can also form a negative pressure in the pressure chambers 116a to 116f. In this way, in the polishing head 1, the pressing force applied to the wafer W is adjusted by adjusting the pressure of the fluid supplied to the pressure chambers 116a to 116f formed between the head body 102 and the elastic film 110. It can be adjusted for each area of the wafer W.

The elastic film 110 is formed of a flexible rubber material having excellent strength and durability, such as ethylene propylene rubber (EPDM), polyurethane rubber, and silicon rubber. The pressure chambers 116a to 116f are also connected to an air opening mechanism (not shown), and the pressure chambers 116a to 116f can be opened to the atmosphere.

The retainer ring 103 is arranged so as to surround the carrier 143 of the head body 102 and the elastic film 110. The retainer ring 103 includes a ring member 103a that comes into contact with the polishing surface 2a of the polishing pad 2, and a drive ring 103b that is fixed to the upper portion of the ring member 103a. The ring member 103a is connected to the drive ring 103b by a plurality of bolts (not shown). The ring member 103a is arranged so as to surround the outer peripheral edge of the wafer W, and holds the wafer W so that the wafer W does not protrude from the polishing head 1 during polishing of the wafer W.

The upper portion of the retainer ring 103 is connected to an annular retainer ring pressing mechanism 160, and the retainer ring pressing mechanism 160 is uniform over the entire upper surface of the retainer ring 103 (more specifically, the upper surface of the drive ring 103b). A downward load is applied, thereby pressing the lower surface of the retainer ring 103 (that is, the lower surface of the ring member 103a) against the polishing surface 2a of the polishing pad 2.

The retainer ring pressing mechanism 160 includes an annular piston 161 fixed to the upper portion of the drive ring 103b and an annular rolling diaphragm 162 connected to the upper surface of the piston 161. A retainer ring pressure chamber 163 is formed inside the rolling diaphragm 162. The retainer ring pressure chamber 163 is connected to the pressure regulator 165 via a rotary joint 182, and a fluid (for example, air) is supplied through a fluid line 173 extending from the pressure regulator 165 to the retainer ring pressure chamber 163. It is supposed to be done.

When a fluid (for example, air) is supplied from the pressure adjusting device 165 to the retainer ring pressure chamber 163, the rolling diaphragm 162 pushes the piston 161 downward, and the piston 161 pushes the entire retainer ring 103 downward. In this way, the retainer ring pressing mechanism 160 presses the lower surface of the retainer ring 103 against the polishing surface 2a of the polishing pad 2. Further, by forming a negative pressure in the retainer ring pressure chamber 163 by the pressure adjusting device 165, the entire retainer ring 103 can be raised. The retainer ring pressure chamber 163 is also connected to an air release mechanism (not shown), and the retainer ring pressure chamber 163 can be opened to the atmosphere.

The retainer ring 103 is detachably connected to the retainer ring pressing mechanism 160. More specifically, the piston 161 is formed of a magnetic material such as metal, and a plurality of magnets 199 are arranged on the drive ring 103b. By attracting the piston 161 by these magnets 199, the retainer ring 103 is magnetically fixed to the piston 161. As the magnetic material of the piston 161, for example, corrosion-resistant magnetic stainless steel is used. The drive ring 103b may be made of a magnetic material and a magnet may be arranged on the piston 161.

The retainer ring 103 is connected to the spherical bearing 185 via a connecting member 175. The spherical bearing 185 is arranged inside the retainer ring 103 in the radial direction. The connecting member 175 includes a shaft portion 176 arranged at the center of the head main body 102, a hub 177 fixed to the shaft portion 176, and a plurality of spokes 178 extending radially from the hub 177. .. The shaft portion 176 extends in the vertical direction in the spherical bearing 185.

One end of the spoke 178 is fixed to the hub 177, and the other end of the spoke 178 is fixed to the drive ring 103b of the retainer ring 103. The hub 177, the spokes 178, and the drive ring 103b are integrally formed. A plurality of pairs of drive pins (not shown) are fixed to the carrier 143. Each pair of drive pins is arranged on both sides of each spoke 178, and the rotation of the carrier 143 is transmitted to the retainer ring 103 via the drive pins, whereby the head body 102 and the retainer ring 103 rotate integrally. ..

The shaft portion 176 of the connecting member 175 is supported by a spherical bearing 185 arranged at the center of the head body 102 so as to be movable in the vertical direction. With such a configuration, the connecting member 175 and the retainer ring 103 fixed to the connecting member 175 can be moved in the vertical direction with respect to the head main body 102. Further, the retainer ring 103 is tiltably supported by a spherical bearing 185.

3 (a), 3 (b), and 3 (c) show an example of the film thickness distribution along the circumferential direction of the wafer W at a position 3 mm inside from the outermost end of the wafer W. It is a figure. More specifically, FIG. 3 (a) shows the initial film thickness distribution before polishing the wafer, and FIG. 3 (b) shows the film thickness distribution of the wafer when it is polished by a conventional polishing device. c) illustrates the thickness distribution of the wafer when it is polished by the polishing apparatus of this embodiment.

Variations in film thickness in the circumferential direction of the wafer tend to be a problem in the subsequent device manufacturing process. In general, variation in film thickness in a region located 3 mm to 5 mm inward from the outermost end of the wafer W is often a problem. The position of the wafer angle of 0 degrees in FIGS. 3 (a) to 3 (c) is set at a characteristic position where the angle (or orientation) in the circumferential direction of the wafer can be specified. In the examples shown in FIGS. 3A to 3C, the position of the wafer angle of 0 degrees is the position of the notch formed on the peripheral edge of the wafer.

In the example shown in FIG. 3A, the initial film thickness distribution before polishing has a peak position at a wafer angle of 180 degrees, and shows a variation in film thickness having a certain peak width and peak height. The cause of such an initial film thickness distribution is considered to be the characteristics of the film forming apparatus and the influence of various processes for forming the multilayer wiring.

When a wafer having the initial film thickness distribution shown in FIG. 3A is polished by a conventional polishing device, the polishing proceeds almost uniformly in the circumferential direction, so that as shown in FIG. 3B, The thickness distribution of the polished wafer remains almost the same as that before polishing. Such variations in the film thickness distribution may cause the focus to be out of focus in the next exposure process, resulting in a decrease in the yield of semiconductor manufacturing.

As shown in FIG. 3C, when the wafer having the initial film thickness distribution of FIG. 3A is polished by the polishing apparatus of the present embodiment described below, the polishing rate at the peak position is selected. By increasing the speed, it is possible to reduce the variation in film thickness in the circumferential direction as compared with the initial film thickness distribution.

An embodiment for improving the variation in the film thickness distribution in the circumferential direction of the wafer by controlling the polishing rate distribution in the circumferential direction of the wafer will be described. FIG. 4 is a diagram showing the positional relationship of the polished surface 2a as viewed from above. If the line connecting the center of the wafer W and the center of the polished surface 2a is defined as the imaginary line VL, the polished surface 2a can be divided into an upstream side of the imaginary line VL and a downstream side of the imaginary line VL in the rotation direction thereof. can. The upstream side of the imaginary line VL and the downstream side of the imaginary line VL are, in other words, the upstream side and the downstream side of the wafer W with respect to the moving direction of the polishing surface 2a.

The circle S shown in FIG. 4 represents the rotation locus of the polished surface 2a passing through the center of the wafer W. Of the two intersections of the tangent T at the center of the wafer of the circle S and the wafer circle, the intersection on the upstream side is the polishing head angle of 0 degrees, and the intersection on the downstream side is the polishing head angle of 180 degrees. Of the two intersections of the imaginary line VL and the wafer circle, the intersection on the center side of the polishing surface is the polishing head angle of 270 degrees, and the intersection on the outer periphery side of the polishing surface is the polishing head angle of 90 degrees. The wafer circle is a circle representing the outermost end of the wafer W. The polishing head angle is the initial position of the polishing head 1 before polishing the wafer, more specifically, the position of the polishing head 1 when the polishing head 1 holding the wafer is arranged above the polishing pad 2. The rotation angle of.

FIG. 5 is a diagram showing an embodiment of a polishing method using a polishing device. The horizontal axis represents the polishing time, and the vertical axis represents the polishing head angle, the wafer angle, and the pressure in the edge pressure chamber 116f that presses the peripheral edge of the wafer W. In this embodiment, the pressure in the edge pressure chamber 116f is given as an example of the polishing conditions, but the pressure in another pressure chamber or the retainer pressure chamber 163 may be used.

As the polishing time elapses, the polishing head angle changes to 0 degrees, 180 degrees, 360 degrees (= 0 degrees), and the rotation of the polishing head 1 is repeated in the cycle T. In the conventional polishing apparatus, the pressure in the edge pressure chamber 116f is maintained constant (not shown), but in the polishing apparatus of the present embodiment, the wafer film is thick (in FIG. 3A). The pressure in the edge pressure chamber 116f is increased while the wafer portion of the wafer angle of 180 degrees) is located at the polishing head angle of 180 degrees. This boosting time is expressed as Δt.

In the example shown in FIG. 5, the polishing rate is high at the position where the polishing head angle is 180 degrees. Therefore, when the portion where the wafer film is thick comes to the position where the polishing head angle is 180 degrees, the pressure in the entire edge pressure chamber 116f is temporarily increased, and the polishing rate of the portion where the wafer film is thick is selectively selected. To increase. By performing this operation a plurality of times or continuously over the total polishing time, it is possible to improve the uniformity of the film thickness distribution in the circumferential direction of the polished wafer. When the pressure in the entire edge pressure chamber 116f is temporarily increased, the polishing rate increases in other places such as an angle of 0 degrees, but the polishing rate is high at the position where the polishing head angle is 180 degrees. The amount of polishing at an angle of 180 degrees increases relatively much as compared with other angles. Therefore, it is possible to improve the uniformity of the film thickness distribution in the circumferential direction of the wafer.

Contrary to the above example, when the place where the wafer film is thin (the place where the wafer angle is 0 degrees) comes to the position where the polishing head angle is 180 degrees, the pressure in the entire edge pressure chamber 116f is temporarily reduced. Therefore, it is also possible to selectively reduce the polishing rate of this portion. It is also possible to more efficiently improve the uniformity of the circumferential film thickness distribution by combining the two pressure operations described above.

In order to temporarily increase the pressure in the pressure chamber when the thick wafer film comes to the position of a certain polishing head angle, the thick wafer film is specified as the wafer angle, and this wafer angle is specified. It is necessary to determine the polishing head angle corresponding to. Therefore, it is necessary to specify the angle (or orientation) of the wafer to determine the relative angle between the wafer and the polishing head. Hereinafter, a method for determining the relative angle between the wafer and the polishing head will be described.

The angle of the notch, which is a characteristic point for specifying the angle of the wafer, is acquired. The angle of this notch is an initial angle indicating the orientation of the wafer before being held by the polishing head 1. More specifically, the notch position of the wafer is detected by a notch position detector (not shown) provided in the polishing apparatus.

Information about the film thickness of the wafer to be polished is input to the control device 9. Information about the wafer film thickness includes the initial film thickness distribution in the circumferential direction of the wafer such as peak position, peak width, and peak height. For example, the film thickness of the wafer is measured by a film thickness measuring device (not shown) provided in the polishing device, and information on the film thickness of the wafer is input from the film thickness measuring device to the control device 9.

The control device 9 acquires the current rotation angle of the polishing head 1, that is, the initial rotation angle. The rotation angle of the polishing head 1 is detected by a rotary encoder 41 (see FIG. 1) attached to the polishing head motor 18. The rotary encoder 41 is a rotation angle detector that detects the rotation angle of the polishing head 1. However, the rotation angle detector is not limited to the rotary encoder as long as it can detect the rotation angle of the polishing head 1.

Next, the control device 9 rotates the polishing head 1 until the initial rotation angle of the polishing head 1 matches the notch position (initial angle) of the wafer at the delivery position. In this case, the relative angle between the wafer and the polishing head 1 is 0 degrees. In this way, the control device 9 determines the relative angle between the wafer and the polishing head 1.

The wafer held by the polishing head 1 is moved to a position above the polishing surface 2a of the polishing pad 2 by the polishing head 1, and is pressed against the polishing surface 2a by the polishing head 1. The wafer is slidably contacted with the polishing surface 2a in the presence of the polishing liquid supplied from the polishing liquid supply nozzle 5, whereby the surface of the wafer is polished. Based on the determined relative angle, the control device 9 temporarily adjusts the pressure in the pressure chamber of the elastic film 110 when the thick portion of the wafer comes to the position of the predetermined polishing head angle. Selectively increase the polishing rate where the wafer film is thick. As a result, the polishing apparatus can improve the uniformity of the film thickness distribution in the circumferential direction of the polished wafer.

As described above, during polishing of the wafer, the wafer may shift in the rotation direction of the polishing head with respect to the polishing head due to the frictional force acting between the wafer and the polishing pad. In this case, since the relative angle between the predetermined wafer and the polishing head also deviates, it is not possible to accurately polish a specific portion (for example, a thick portion) of the wafer.

Therefore, the polishing device includes a reference position detecting device that detects a reference position of an angle in the circumferential direction of the wafer during polishing of the wafer. In the present embodiment, the reference position of the circumferential angle of the wafer is the position of the notch. Therefore, the reference position detection device may be referred to as a notch detection device. The notch detector is configured to measure the position of the notch on the wafer. Hereinafter, the notch detection device will be described with reference to the drawings.

FIG. 6 is a diagram showing an embodiment of the notch detection device 200. In the embodiment shown in FIG. 6, the notch detection device 200 is an image acquisition device arranged adjacent to the elastic film 110. In the embodiment shown in FIG. 6, the notch detection device 200 is a combination of the fiberscope 200a and the light 200b, and the tip of the fiberscope 200a and the irradiation portion of the light 200b are located in the edge pressure chamber 116f of the elastic film 110. Have been placed. In one embodiment, the notch detection device 201 may be a fiberscope with a built-in light.

The notch detection device 200 (more specifically, the fiberscope 200a) is electrically connected to the control device 9. During polishing of the wafer, the fiberscope 200a constantly images the peripheral edge of the wafer through the elastic film 110 with the light 200b irradiating the edge pressure chamber 116f. In this embodiment, the elastic membrane 110 is transparent or translucent in order to obtain a clearer image. The notch detection device 200 is composed of a repeater provided on the upper part of the head and an amplifier provided in the polishing device, to which the fiberscope 200a and the light 200b are connected, and wireless communication is performed between the repeater and the amplifier. Signals are sent and received by.

FIG. 7 is a diagram showing notch detection devices 200 arranged at equal intervals along the circumferential direction of the edge pressure chamber 116f of the elastic film 110. As shown in FIG. 7, the polishing device may include a plurality of notch detection devices 200 arranged at equal intervals along the circumferential direction of the edge pressure chamber 116f. Each notch detection device 200 is arranged at a predetermined rotation angle of the polishing head 1.

For example, one of the plurality of notch detection devices 200 is arranged at a position where the rotation angle of the polishing head 1 is 0 degrees. The other notch detection device 200 is along the circumferential direction of the polishing head 1 (more specifically, the elastic film 110) with reference to the notch detection device 200 arranged at a position where the rotation angle of the polishing head 1 is 0 degrees. They are arranged at equal intervals (for example, the rotation angles of the polishing head 1 are 30 degrees, 60 degrees, 90 degrees, and so on).

The control device 9 stores as a database the correlation between the output of the notch detection device 200 arranged at a predetermined position in the rotation angle of the polishing head 1 and the rotation angle of the polishing head 1. For example, the fiberscope 200a is arranged so that the notch Nt is located at the center of the image captured by the fiberscope 200a arranged at a position where the rotation angle of the polishing head is 0 degrees. In this case, the control device 9 determines that the notch Nt is at a position where the rotation angle of the polishing head 1 is 0 degrees.

When the angle of the wafer deviates from the rotation angle of the polishing head 1 after the start of polishing the wafer, the position of the notch Nt deviates from the center of the image captured by the fiberscope 200a. For example, when the position of the notch Nt is shifted to the right by 5 mm from the center of the image, the control device 9 determines that the notch Nt is at a position where the rotation angle of the polishing head 1 is 355 degrees. When the position of the notch Nt is shifted to the left by 5 mm from the center of the image, the control device 9 determines that the notch Nt is at a position where the rotation angle of the polishing head 1 is 5 degrees. In this way, the control device 9 may store the correlation between the position of the notch Nt projected on the image captured by the fiberscope 200a and the rotation angle of the polishing head 1.

FIG. 8 is a diagram showing a flow for correcting the relative angle between the wafer and the polishing head by the control device 9. The control device 9 is configured to acquire the position of the notch during polishing of the wafer from the notch detection device 200. The control device 9 has a first signal (first data) regarding the rotation angle of the polishing head 1 acquired from the rotary encoder 41 and a second signal (second data) regarding the rotation angle of the notch position acquired from the notch detection device 200. Based on the data of 2), the relative angle of the reference position with respect to the polishing head 1 is calculated.

First, as shown in step S101, the control device 9 determines the position of the notch (that is, the wafer) before the start of polishing the wafer based on the rotation angle of the polishing head 1 acquired from the rotary encoder 41 (see FIG. 1). The relative angle with the polishing head 1 is determined. Next, the control device 9 starts polishing the wafer (see step S102), and identifies the position of the notch based on the data acquired from the notch detection device 200 during the polishing of the wafer (see step S103).

After that, the control device 9 determines the position of the notch during polishing of the wafer and the relative angle between the polishing head 1 and calculates the amount of change in the current relative angle with respect to the relative angle before polishing the wafer (see step S104). ). After that, the control device 9 corrects the relative angle before polishing based on the calculated change amount of the relative angle (see step S105). The control device 9 periodically changes the pressure in the pressure chamber in synchronization with the rotation angle of the polishing head 1 based on the corrected relative angle and the information on the thickness of the wafer (see step S106). By periodically changing the pressure in the pressure chamber based on this information, the film thickness distribution in the circumferential direction of the polished wafer can be made uniform.

The control device 9 periodically repeats the steps from step S103 to step S106 to continue polishing the wafer. After step S106, the control device 9 finishes polishing the wafer by reaching a predetermined polishing time or receiving a signal from an end point detection system (not shown) (see “Yes” in step S107) (see “Yes” in step S107). See step S108). When the predetermined polishing time has not been reached or a signal from the end point detection system (not shown) has not been received (see “No” in step S107), the step shown in step S103 is repeated.

According to the present embodiment, since the polishing device includes a notch detection device 200 that acquires the position of the notch during polishing of the wafer, the reference position of the wafer angle (that is, the position of the notch) during polishing of the wafer. Can be identified accurately.

The control device 9 may input the image data captured by the fiberscope 200a into the model constructed by the machine learning algorithm, and output the determination result indicating the position of the notch from the model. As a machine learning algorithm, a deep learning method (deep learning method) is suitable.

By using the model constructed by the machine learning algorithm, it is possible to automatically and accurately generate the determination result indicating the position of the notch. By using such a determination result, the control device 9 can more accurately calculate the amount of change in the relative angle between the notch position and the polishing head 1.

FIG. 9 is a diagram for explaining a method of constructing a trained model. The control device 9 is configured to learn the determination result including various elements by a machine learning algorithm such as deep learning and generate an optimum determination result. When building a trained model, first collect the data and create a collection of raw data (see Figure 9).

Data collection is extensive. The data collected is not limited to the image data measured by the notch detector 200. For example, the data includes various factors such as the shape, transparency, and thickness of the elastic membrane 110.

Next, the training data set required to build (and update) the trained model is created from the collection of raw data. The numerical value indicating the actual notch position is correct data and is used for machine learning such as deep learning.

As shown in FIG. 9, machine learning using a neural network or quantum computing is performed to build a trained model. As machine learning using a neural network or quantum computing, a deep learning method (deep learning method) is suitable. The deep learning method is a learning method based on a neural network in which hidden layers (also referred to as intermediate layers) are multi-layered.

The storage device 9a (see FIG. 1) of the control device 9 stores the model constructed by the machine learning algorithm, and the processing device 9b (see FIG. 1) stores at least the data detected by the notch detection device 200. Input to the model and execute the calculation to output the judgment result indicating the notch position from the model. The determination result output from the model may be reflected in the training data set for updating the trained model.

As described above, when image data indicating the current notch position is input to the constructed model, the computer executes an operation according to the algorithm of the multi-layer perceptron that constitutes the neural network, and the output layer determines the notch position. The indicated determination result (for example, numerical value) is output.

Hereinafter, other embodiments of the notch detection device will be described with reference to the drawings. The notch detection device described below measures the position of the notch based on the distance to the wafer, instead of acquiring image data indicating the position of the notch. Also in the following embodiments (FIGS. 10 to 16), a determination result indicating the position of the notch may be automatically generated by using the model constructed by the machine learning algorithm. As a result, the control device 9 can more accurately calculate the amount of change in the relative angle between the notch position and the polishing head 1.

10 and 11 are views showing a notch detection device 201 arranged outside the retainer ring 103. In the embodiment shown in FIGS. 10 and 11, the notch detection device 201 is a non-contact distance sensor. More specifically, the notch detection device 201 is an ultrasonic sensor and is electrically connected to the control device 9. The notch detection device 201 as an ultrasonic sensor can measure the frequency band of ultrasonic waves in the range of several hundred kHz to several hundred MHz.

As shown in FIGS. 10 and 11, the ring member 103a of the retainer ring 103 is formed with grooves 104 that allow the passage of the polishing liquid at equal intervals along the circumferential direction of the ring member 103a. The notch detection device 201 is arranged adjacent to the groove 104 and is not attached to the polishing head 1. Therefore, even if the polishing head 1 rotates, the notch detection device 201 does not rotate together with the polishing head 1.

The notch detection device 201 transmits ultrasonic waves toward the wafer through the groove 104 and receives the reflected wave from the wafer to measure the distance to the wafer in a non-contact manner. The distance between the notch Nt of the wafer and the notch detection device 201 is different from the distance between the portion where the notch Nt is not formed and the notch detection device 201. Therefore, the control device 9 accurately determines the position of the notch Nt by acquiring the data measured by the notch detection device 201 during the polishing of the wafer and calculating the time required from the transmission to the reception of ultrasonic waves. Can be identified. Also in this embodiment, the notch detection device 201 can accurately identify the reference position of the wafer angle (that is, the position of the notch) during the polishing of the wafer.

In one embodiment, the notch detection device 201 may be a capacitance sensor instead of an ultrasonic sensor as a non-contact distance sensor. The notch detection device 201 as a capacitance sensor measures the capacitance between the notch detection device 201 and the wafer. The control device 9 measures the distance between the wafer and the notch detection device 201 based on the capacitance sent from the notch detection device 201.

In one embodiment, the notch detection device 201 may be arranged on the downstream side of the notch position at the start of polishing in the rotation direction of the polishing table 3. With such an arrangement, the notch detection device 201 can more reliably measure the position of the notch even if the wafer is displaced in the rotation direction of the polishing head 1 during polishing of the wafer.

In one embodiment, the notch detection device 201 may be an acoustic sensor as the non-contact distance sensor. In this case, the notch detection device 201 as an acoustic sensor is preferably arranged on the downstream side in the rotation direction of the polishing table 3.

After the start of polishing the wafer, the peripheral edge of the wafer W collides with the inner peripheral surface of the retainer ring 103 on the rotation downstream side of the polishing table 3. The collision sound with the retainer ring 103 at the portion where the notch Nt is formed is different from the collision sound with the retainer ring 103 at the portion where the notch Nt is not formed. Therefore, the control device 9 acquires the data measured by the notch detection device 201 as an acoustic sensor during polishing of the wafer, and measures the change in the collision sound, whereby the control device 9 determines the position of the notch Nt. It can be identified accurately.

FIG. 12 is a diagram showing another embodiment of the notch detection device 201. As shown in FIG. 12, the notch detection device 201 may be a non-contact distance sensor arranged in the pressure chamber 116f of the elastic membrane 110. The notch detection device 201 is attached to the inner peripheral surface of the peripheral wall 114f.

FIG. 13 is a diagram showing a retaining ring 202 that holds a plurality of notch detection devices 201. As shown in FIG. 13, the plurality of notch detection devices 201 may be held by holding rings 202 arranged concentrically with the elastic film 110. The plurality of notch detection devices 201 are arranged at equal intervals along the circumferential direction of the holding ring 202, and the holding rings 202 are arranged in the pressure chamber 116f. With such a configuration, the plurality of notch detection devices 201 can be easily arranged over the entire circumference of the peripheral edge of the wafer by simply arranging the retaining ring 202 in the pressure chamber 116f. By arranging the plurality of notch detection devices 201 along the circumferential direction of the elastic film 110 in this way, at least one of the plurality of notch detection devices 201 can reliably identify the position of the notch Nt. ..

In one embodiment, the notch detection device 201 may be a vibration sensor. The vibration of the elastic film 110 caused by the collision with the retainer ring 103 of the wafer portion where the notch Nt is formed is the vibration of the elastic film 110 caused by the collision with the retainer ring 103 of the wafer portion where the notch Nt is not formed. Different from vibration. The control device 9 accurately identifies the position of the notch Nt by acquiring the data measured by the notch detection device 201 as a vibration sensor and measuring the change in vibration during the polishing of the wafer. can do.

In one embodiment, the notch detection device 201 may be an acoustic sensor. Even in this case, the control device 9 acquires the data measured by the notch detection device 201 as an acoustic sensor during the polishing of the wafer, and measures the change in the collision sound, whereby the control device 9 can be used. The position of the notch Nt can be accurately specified.

14 and 15 are views showing still another embodiment of the notch detection device 201. As shown in FIG. 14, the notch detection device 201 may have a non-contact distance embedded inside the ring member 103a of the retainer ring 103. When a plurality of notch detection devices 201 are provided, the plurality of notch detection devices 201 are arranged at equal intervals along the circumferential direction of the ring member 103a.

As shown in FIG. 15, the notch detection device 201 may be a non-contact distance sensor attached to the drive ring 103b of the retainer ring 103. When a plurality of notch detection devices 201 are provided, the plurality of notch detection devices 201 are arranged at equal intervals along the circumferential direction of the drive ring 103b. The ring member 103a is a consumable part that needs to be replaced, whereas the drive ring 103b is a part that does not need to be replaced, so that it does not need to be removed when the part is replaced. Similar to the above-described embodiment, in one embodiment, the notch detection device 201 may be an acoustic sensor or a vibration sensor.

FIG. 16 is a diagram showing still another embodiment of the notch detection device 201. As shown in FIG. 16, the notch detection device 201 may be a non-contact distance sensor embedded in the polishing table 3. In the embodiment shown in FIG. 16, the notch detection device 201 is embedded in the communication hole 3b formed in the polishing table 3 and is arranged on the back surface side of the polishing pad 2. Since the wafer is pressed against the polishing pad 2 during polishing of the wafer, the notch detection device 201 can measure the position of the notch Nt formed on the wafer via the polishing pad 2.

In the embodiment shown in FIG. 16, the notch detection device 201 is arranged below the peripheral edge of the wafer, but when a plurality of notch detection devices 201 are provided, the plurality of notch detection devices 201 are centered on the wafer. It may be arranged along the rotation locus (see FIG. 4) of the polishing surface 2a passing through. Further, the plurality of notch detection devices 201 may be arranged on the outer side in the radial direction and the inner side in the radial direction of the rotation locus of the polished surface 2a.

In the above-described embodiment, the angle between the wafer and the polishing head 1 is adjusted at the initial stage of polishing, and the position of the notch is based on the position information of the notch Nt (or information on the rotation angle of the wafer) by the notch detection device 200. While correcting the relative angle between the wafer and the polishing head 1, the pressure in the pressure chamber (that is, the polishing pressure) is changed when a specific position of the wafer reaches a specific head rotation angle. In that case, the timing at which the specific position of the wafer comes to the position of the specific head rotation angle is calculated from the rotation angle of the polishing head 1 acquired from the rotary encoder 41 (see FIG. 1) and the corrected relative angle. May be good. Further, the timing at which the specific position of the wafer comes to the specific head rotation angle is the rotation angle of the notch Nt obtained by the notch detection device 200 and the thickness of the wafer without obtaining the relative angle between the wafer and the polishing head 1. It may be obtained directly from the angle of the portion having a large value with respect to the notch Nt.

According to the above-described embodiment, the control device 9 identifies the position of the notch Nt based on the data measured by at least one of the notch detection device 200 and the notch detection device 201 during the polishing of the wafer. be able to. Therefore, the control device 9 may determine the timing at which the polishing head 1 is separated from the polishing pad 2 after the polishing of the wafer is completed, based on the position of the notch Nt.

FIG. 17 is a diagram showing a scribe line of a pattern formed on a wafer. As shown in FIG. 17, a grid-like scribe line SL is formed on the wafer W. In the embodiment shown in FIG. 17, the notch Nt is a notch extending in a direction parallel to and perpendicular to the scribe line SL.

18 (a) to 18 (c) are views showing how the wafer is cracked. As shown in FIG. 18A, during polishing of the wafer W, the wafer W receives a frictional force from the polishing surface 2a, and the peripheral edge portion of the wafer W is inside the retainer ring 103 (more specifically, the ring member 103a). It may be pressed against the peripheral surface. When the polishing of the wafer is completed and the polishing head 1 is raised, the retainer ring 103 slightly moves downward due to its own weight (see FIG. 18B). When the polishing head 1 rises while the peripheral edge of the wafer W is in contact with the inner peripheral surface of the retainer ring 103, a downward force is applied to the wafer W due to the weight of the retainer ring 103.

Due to the characteristics of crystal orientation, the wafer is liable to crack along the direction orthogonal to the direction in which the notch Nt extends. Therefore, if the polishing head 1 rises when the notch Nt is in contact with the inner peripheral surface of the retainer ring 103 at a position downstream of the rotation direction of the polishing table 3, the wafer may be cracked. In particular, when the portion of the wafer W in contact with the retainer ring 103 is parallel to the scribe line SL (more specifically, in the direction perpendicular to the direction in which the notch Nt extends), the wafer W can be cracked along the scribe line SL. Highly sexual.

Therefore, the control device 9 determines the polishing head when the portion of the wafer W in contact with the retainer ring 103 is tilted (for example, 45 degrees) with respect to the scribe line SL based on the position of the specified notch Nt. It is desirable to increase 1. More specifically, the strength of the wafer is high when the notch Nt is in the direction of 45 degrees with respect to the downstream side in the rotation direction of the polishing table 3. Therefore, if the polishing head 1 is raised at this time, the control device 9 can prevent the wafer from being damaged.

In the embodiment shown in FIG. 17, the control device 9 determines that the current notch Nt position is the notch Nt before polishing the wafer W based on the information acquired from the notch detection device 200 (and / or the notch detection device 201). When it is determined that the polishing head 1 is tilted (for example, 45 degrees off) with respect to the position, the polishing head 1 is pulled up. With such a configuration, the control device 9 can prevent the wafer W from cracking when the polishing head 1 is raised.

The embodiments shown in FIGS. 6, 10, 12, 13, 14, 14, 15, and 16 may be combined as much as possible. In this case, the notch detection device (reference notation omitted) includes an image acquisition device (see, for example, FIG. 6) and a non-contact sensor (see, for example, FIGS. 10, 12, 14, 15, 15, and 16). You may prepare.

The above-described embodiment is described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to carry out the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is construed in the broadest range according to the technical idea defined by the claims.

1 Polishing head 2 Polishing pad 2a Polishing surface 3 Polishing table 3a Table shaft 3b Communication hole 5 Polishing liquid supply nozzle 9 Control device 9a Storage device 9b Processing device 11 Polishing head shaft 12 Rotating cylinder 13 Table motor 14 Timing pulley 16 Head arm 18 Polishing Head Motor 19 Timing Belt 20 Timing Pulley 21 Arm Shaft 25 Rotary Joint 26 Bearing 27 Vertical Movement Mechanism 28 Bridge 29 Support Base 30 Support 32 Ball Screw 38 Servo Motor 39 Polishing Head Height Sensor 41 Rotary Encoder (Rotation Angle Detector)
102 Head body 103 Retainer ring 103a Ring member 103b Drive ring 104 Groove 110 Elastic film 114a, 114b, 114c, 114d, 114e, 114f Peripheral wall 116a Central pressure chamber 116b, 116c, 116d, 116e Intermediate pressure chamber 116f Edge pressure chamber 141 Flange 142 Spacer 143 Carrier 160 Retainer ring pressing mechanism 161 Piston 162 Rolling diaphragm 163 Retainer ring Pressure chamber 165 Pressure regulator 173 Fluid line 175 Connecting member 176 Shaft 177 Hub 178 Spoke 182 Rotary joint 185 Spherical bearing 199 Magnet 200, 201 Notch detector ( Reference position detector)
200a Fiberscope 200b Light 202 Retaining Ring

Claims (12)

A polishing table that supports the polishing pad and
A polishing head that presses the substrate against the polishing surface of the polishing pad,
A rotation mechanism that rotates the polishing head around its axis,
A reference position detecting device for detecting a reference position of an angle in the circumferential direction of the substrate during polishing of the substrate, and a reference position detecting device.
A rotation angle detector that detects the rotation angle of the polishing head,
A control device for acquiring the reference position during polishing of the substrate from the reference position detecting device is provided.
The control device is based on the first signal regarding the rotation angle of the polishing head acquired from the rotation angle detector and the second signal regarding the rotation angle of the reference position acquired from the reference position detection device. A polishing device that calculates a relative angle of a reference position with respect to the polishing head. The control device is
Based on the rotation angle of the polishing head obtained from the rotation angle detector, the relative angle between the reference position and the polishing head before the start of polishing of the substrate is determined.
The amount of change in the relative angle is calculated based on the reference position during polishing of the substrate obtained from the reference position detection device.
The polishing apparatus according to claim 1, wherein the relative angle is corrected based on the calculated amount of change. The control device inputs the data measured by the reference position detecting device into a model constructed by a machine learning algorithm, and outputs a determination result indicating the position of the reference position from the model according to claim 1 or 2. The polishing apparatus described in. The polishing head
An elastic film that presses the substrate against the polished surface,
It is provided with a retainer ring that is arranged so as to surround the elastic film and is in contact with the polished surface.
The polishing apparatus according to any one of claims 1 to 3, wherein the reference position detecting apparatus is arranged adjacent to the elastic film. The polishing apparatus according to claim 4, wherein the reference position detecting apparatus includes an image acquisition apparatus arranged in a pressure chamber of the elastic film. The polishing apparatus according to claim 4 or 5, wherein the reference position detecting device includes a non-contact distance sensor or an acoustic sensor arranged outside the retainer ring. The polishing apparatus according to any one of claims 4 to 6, wherein the reference position detecting apparatus includes a non-contact distance sensor, an acoustic sensor, or a vibration sensor arranged in a pressure chamber of the elastic film. .. The reference position detecting device according to any one of claims 4 to 7, further comprising a non-contact distance sensor, an acoustic sensor, or a vibration sensor embedded inside the ring member of the retainer ring. Polishing equipment. The polishing apparatus according to any one of claims 4 to 8, wherein the reference position detecting device includes a non-contact distance sensor, an acoustic sensor, or a vibration sensor attached to the drive ring of the retainer ring. .. The polishing device according to any one of claims 4 to 9, wherein the reference position detecting device includes a non-contact distance sensor embedded in the polishing table. Obtain the film thickness distribution information of the substrate and
With reference to the reference position of the angle in the circumferential direction of the substrate, the rotation angle of the specific portion for which the film thickness on the substrate should be adjusted is determined.
During polishing of the substrate, a reference position of an angle in the circumferential direction of the substrate is detected.
A polishing method for adjusting the polishing pressure when the specific part is located at a specific position on the polishing table based on the detected reference position information and the rotation angle of the specific part. During polishing of the substrate, the reference position of the circumferential angle of the substrate is detected.
A polishing method for determining the timing at which the polishing head rises based on the detected reference position information.

Images