JP7757902B2 - Single-sided wafer polishing method, wafer manufacturing method, and single-sided wafer polishing apparatus - Google Patents

Description

The present invention relates to a method for polishing a single side of a wafer, a method for manufacturing a wafer, and an apparatus for polishing a single side of a wafer.

It is known that when polishing one side of a wafer with a polishing pad, the physical properties of the polishing pad's surface affect the amount of material removed. One known technique for addressing this effect is to improve polishing performance by using a polishing pad with a specific range of surface roughness-to-compressibility ratio (see, for example, Patent Document 1). Another known technique uniformly conditions the polishing pad surface by controlling the rotation speed of a platen on which the polishing pad is placed and the movement speed of a conditioning head in the radial direction of the platen depending on the distance of the conditioning head from the center of the platen (see, for example, Patent Document 2). Yet another known technique modifies the surface shape of the polishing cloth to correct uneven pressure acting on the wafer by changing the amount of surface shape modification depending on the position on the surface of the polishing cloth (see, for example, Patent Document 3).

Japanese Patent Application Laid-Open No. 2003-142437 JP 2017-064874 A Japanese Patent Application Laid-Open No. 2002-187059

However, as demands for wafer shape accuracy increase, particularly in terms of ESFQR (Edge Site Flatness Front Reference Least Square Deviation) around the wafer periphery, it is becoming increasingly difficult to obtain wafers with the desired shape simply by making the overall compressibility or surface shape of the polishing pad uniform, as in the techniques described in Patent Documents 1 to 3.

The present invention aims to provide a single-sided wafer polishing method, a wafer manufacturing method, and a single-sided wafer polishing apparatus that can produce wafers of the desired shape.

The single-sided polishing method for wafers of the present invention uses a single-sided polishing apparatus that polishes a wafer by pressing the wafer held by a polishing head against a suede-type polishing pad that is larger than the wafer and rotating the polishing head and the polishing pad. The method comprises: a compressibility distribution calculation step for calculating the radial compressibility distribution of the polishing pad according to the target shape of the wafer after polishing; a polishing pad adjustment step for adjusting the polishing pad so that it has the compressibility distribution; and a polishing step for polishing the wafer using the polishing pad that has the compressibility distribution.

In the single-side polishing method for wafers of the present invention, the polishing pad conditioning step preferably involves rotating the polishing pad while pressing a brush against the polishing pad to form an annular region on the polishing pad with a compression rate different from that of other regions.

In the single-side polishing method for wafers of the present invention, the polishing pad conditioning step preferably forms the annular region so that the thickness of the region having the compressibility distribution is substantially uniform.

In the single-side polishing method for wafers of the present invention, the polishing step preferably involves polishing the wafer while the wafer is positioned outside the center of rotation of the polishing pad, and the polishing pad conditioning step preferably involves using the brush to form a single annular region, the annular region having an inner edge located outside the 99% position and inside the 100% position, where the center of rotation of the polishing pad is defined as the 0% position and the position on the outer edge of the wafer farthest from the center of rotation is defined as the 100% position, and the region has a higher compression rate than the inner region.

In the single-sided wafer polishing method of the present invention, it is preferable that the indicator of the target shape of the wafer is ESFQR.

In the single-side polishing method for wafers of the present invention, the polishing step preferably involves polishing the wafer while the wafer is positioned outside the center of rotation of the polishing pad, and the polishing pad conditioning step preferably involves using the brush to form annular regions such that three or more regions with different compression rates are aligned radially, and the third innermost region of the three or more regions with different compression rates is an annular region whose inner edge is located inside the 100% position, where the center of rotation of the polishing pad is the 0% position and the position on the outer edge of the wafer farthest from the center of rotation is the 100% position.

In the single-sided wafer polishing method of the present invention, it is preferable that the indicator of the target shape of the wafer is GBIR.

The single-sided polishing method of the present invention preferably comprises a polishing apparatus preparation step in which the compressibility distribution calculation step and the polishing pad adjustment step based on the different target shapes are performed on the multiple single-sided polishing apparatuses so that the compressibility distributions of the polishing pads equipped on the multiple single-sided polishing apparatuses are different from one another; and a polishing apparatus selection step in which the single-sided polishing apparatus capable of polishing the wafer to be polished into the set target shape is selected from the multiple single-sided polishing apparatuses, and the polishing step preferably comprises polishing the wafer using the single-sided polishing apparatus selected in the polishing apparatus selection step.

The wafer manufacturing method of the present invention includes a finishing step for finishing the wafer, in which the wafer is polished using the single-sided wafer polishing method described above.

The single-sided wafer polishing apparatus of the present invention polishes a wafer by pressing a wafer held by a polishing head against a suede-type polishing pad that is larger than the wafer and rotating the polishing head and the polishing pad. It includes a polishing pad adjustment unit that adjusts the polishing pad, a rotation drive unit that rotates the polishing head and the polishing pad, and a control device. The control device includes a compression distribution calculation unit that calculates the radial compressibility distribution of the polishing pad according to the target shape of the wafer after polishing, a polishing pad adjustment control unit that controls the polishing pad adjustment unit to adjust the polishing pad to have the compression distribution, and a polishing control unit that controls the rotation drive unit to polish the wafer using the polishing pad having the compression distribution.

In the single-side wafer polishing apparatus of the present invention, it is preferable that the polishing pad adjustment unit includes a brush, and the polishing pad adjustment control unit controls the polishing pad adjustment unit to rotate the polishing pad while pressing the brush against the polishing pad, thereby forming an annular region with a compression rate different from other regions.

In the single-side wafer polishing apparatus of the present invention, it is preferable that the polishing pad adjustment unit includes a position adjustment unit that adjusts the position of the brush, and the polishing pad adjustment control unit controls the position adjustment unit to position the brush at a height position corresponding to the compression ratio.

1 is a schematic diagram showing a schematic configuration of a single-sided polishing apparatus according to a first embodiment and a second embodiment. 3A to 3C are plan views showing a method for adjusting a polishing pad according to the first and second embodiments. FIG. 2 is a block diagram showing a schematic configuration of a control device according to the first and second embodiments. 3 is a flowchart showing a wafer manufacturing method according to the first and second embodiments. 10 is a flowchart showing a single-side finishing process according to the first embodiment. 3A and 3B are schematic diagrams showing an example of the compressibility distribution of the polishing pad according to the first and second embodiments. 10 is a flowchart showing a single-side finishing process according to the second embodiment. 10 is a graph showing the relationship between the compressibility distribution of the polishing pad according to Example 2 and the shape of the wafer after polishing.

[First embodiment]
A first embodiment of the present invention will be described below.

<Configuration of single-sided polishing device>
First, a single-side polishing apparatus 1 according to a first embodiment of the present invention will be described with reference to the accompanying drawings.
1 polishes one side (surface to be polished W1) of a wafer W (hereinafter, polishing in the single-sided polishing apparatus 1 may be referred to as "single-sided polishing"). The single-sided polishing apparatus 1 includes a polishing unit 2, a polishing pad adjustment unit 4, and a control device 5.

The polishing unit 2 includes a polishing head 21, a head holding unit 22, a head lifting unit 23, a head driving unit 24 as a rotation driving unit, a surface plate 25, a polishing pad 26, a surface plate driving unit 27 as a rotation driving unit, a wafer pressure adjusting unit 28, and a polishing liquid supply unit 29.
Although the polishing unit 2 may be provided with only one polishing head 21, the present embodiment illustrates a configuration in which the polishing unit 2 is provided with a plurality of polishing heads 21.

Each polishing head 21 is formed in a disk shape. Each polishing head 21 holds the surface (back surface) of the wafer W opposite the polished surface W1 (front surface) by using the surface tension of water, etc.

A back pad 211 is arranged on the underside of the polishing head 21 so as to cover the entire underside. The back pad 211 is made of, for example, a porous resin material and can contain liquid such as water.

A ring-shaped retainer ring 212 is disposed on the outer periphery of the underside of the back pad 211. The retainer ring 212 contacts the outer periphery of the wafer W located inside the retainer ring 212, and holds the wafer W so that it does not slip out of the gap between the back pad 211 and the polishing pad 26.

A cylindrical head rotation shaft member 213 is located in the center of the top surface of each polishing head 21.

The head holding unit 22 holds the upper end of the head rotation shaft member 213 of each polishing head 21 so that the head rotation shaft member 213 can rotate around its axis. The head holding unit 22 holds the head rotation shaft member 213 so that multiple polishing heads 21 are lined up at equal intervals on the circumference of a predetermined circle.

The head lifting unit 23 raises and lowers the head holding unit 22.

The head drive unit 24 is disposed inside the head holder 22. The head drive unit 24 is composed of, for example, a motor, and rotates the head rotation shaft member 213 connected to the rotation shaft of the motor.

The surface plate 25 is formed in a disk shape and is positioned below the multiple polishing heads 21. A cylindrical surface plate rotation shaft member 251 is located in the center of the underside of the surface plate 25.

The polishing pad 26 is attached to the upper surface of the surface plate 25. The polishing pad 26 is formed in a circular shape larger than the wafer W and is configured to simultaneously polish wafers W held by multiple polishing heads 21. The polishing pad 26 is a soft suede-type polishing pad. The compressibility of the polishing pad 26 is, for example, 23% or more and 36% or less. The polishing pad 26 has a nap layer. The polished surface W1 of the wafer W is pressed against the nap layer of the polishing pad 26 with a predetermined force, thereby polishing the wafer W.
Here, the nap layer refers to a layer having a large number of pores formed by foaming.

The platen driving unit 27 is composed of, for example, a motor, and rotates the platen rotation shaft member 251 connected to the motor's rotation shaft in the same direction as or opposite to the rotation direction of the polishing head 21.

The wafer pressure adjustment unit 28 is a fixed pressure type device that adjusts the pressure that presses the wafer W against the polishing pad 26. With the fixed pressure type, the entire polishing head 21 is pressed down by cylinder pressure, and the polishing head 21 is pressed against the top surface of the wafer W via the back pad 211, thereby pressing the polished surface W1 of the wafer W against the polishing pad 26.

The polishing liquid supply unit 29 supplies a slurry-like polishing liquid to the polishing pad 26 via a nozzle 291. This polishing liquid is used to polish the polished surface W1 of the wafer W.

The polishing unit 3 may be provided with a swing drive unit that swings each polishing head 21 in a direction parallel to the polishing surface of the polishing pad 26. For example, the swing drive unit holds the head lift unit 23 and moves the head lift unit 23 back and forth in one direction (for example, back and forth in the left and right direction in FIG. 1 ) during polishing of the wafer W, thereby swinging each polishing head 21 around the rotation axis D of the polishing head 21.
By using such an oscillation drive unit to oscillate the polishing head 21 during polishing, the width of the outer periphery of the wafer W to be polished can be adjusted using a predetermined adjustment area described below, and a wafer W of the desired shape can be obtained.

The polishing pad adjusting unit 4 adjusts the polishing pad 26 so that the polishing pad 26 has a compressibility distribution in the radial direction. The adjusted region of the polishing pad 26 has a high compressibility and becomes soft.
The polishing pad adjustment unit 4 includes a brush holder 41, a brush 42, a position adjustment unit 43, the surface plate 25 and the surface plate driver 27 described above.

The brush holder 41 includes a rod-shaped brush pivot shaft member 411 that extends vertically. A horizontally extending holding arm 412 is located at the upper end of the brush pivot shaft member 411.

The brush 42 is disposed at the tip end of the holding arm 412. The brush 42 is made up of a plurality of nylon bristles bound together in a circular shape, and is formed in a shape that is smaller than the surface of the polishing pad 26 in a plan view.
As will be described in more detail later, by rotating the polishing pad 26 against which the brush 42 is pressed, the compression ratio of the contact area of the polishing pad 26 with the brush 42 increases, and a compression ratio distribution is formed in the polishing pad 26.
From the viewpoint of improving the resolution of the compressibility distribution, the diameter of the cylindrical shape formed by the bundled bristles of the brush 42 is preferably 5 mm or less. Furthermore, from the viewpoint of suppressing variations in the compressibility due to deformation of the bristles when the brush 42 is pressed against the polishing pad 26, the length of the bristles of the brush 42 is preferably 0.5 mm or more and 15 mm or less.

The position adjustment unit 43 adjusts the position of the brush 42. The position adjustment unit 43 adjusts the height position of the brush 42 by raising and lowering the brush rotation shaft member 411. The position adjustment unit 43 adjusts the horizontal position of the brush 42 on the polishing pad 26 by rotating the brush rotation shaft member 411 around its axis.

Here, a method for adjusting the polishing pad 26 so as to have a compressibility distribution using the polishing pad adjusting unit 4 will be described.
2, the position adjustment unit 43 presses the brush 42 against the polishing pad 26 with the holding arm 412 positioned as shown by the solid line under the control of the control device 5. Next, the surface plate driving unit 27 rotates the surface plate 25 under the control of the control device 5. As the surface plate 25 rotates, a first adjustment region 261, which is annular and indicated by a two-dot chain line, on the polishing pad 26 is adjusted.
Furthermore, when the brush 42 is pressed against the polishing pad 26 with the holding arm 412 positioned at the position shown by the dotted line and the base plate 25 is rotated, the fifth adjustment area 265, which is annular and shown by the dotted line on the polishing pad 26, is adjusted.
Furthermore, by setting the position on the polishing pad 26 against which the brush 42 is pressed to a predetermined position, a second adjustment area 262, a third adjustment area 263, and a fourth adjustment area 264, each indicated by a two-dot chain line, are adjusted.

The compression ratio of the adjusted region (adjusted region) is greater than the compression ratio of the unadjusted region (unadjusted region), for example, the compression ratio of the unadjusted region 260 located inside the first adjusted region 261 .
Furthermore, the compression rate of the adjustment area increases as the amount of pressing of the brush 42 against the polishing pad 26 increases (as the height position of the brush 42 decreases).
Furthermore, when the amount of pressing of the brush 42 against the polishing pad 26 is the same, the compression rate of the adjustment area increases as the adjustment time increases.
Furthermore, the thickness of the unadjusted area and each adjusted area is substantially equal regardless of the amount of pressure of the brush 42 against the polishing pad 26 .
In this way, the polishing pad adjustment section 4 can form annular adjustment regions in the polishing pad 26 so that regions with different compressibility are aligned in the radial direction of the polishing pad 26 and the thicknesses of the regions with the compressibility distribution are substantially equal. In other words, the compressibility distribution is a distribution formed by annular adjustment regions with different compressibility.

Furthermore, the higher the compressibility of the polishing pad 26 is in an area, the smaller the removal amount during polishing becomes.
Therefore, for example, by forming a compression rate distribution in the polishing pad 26 so that the compression rate of the outer region is higher than that of the inner region, the removal rate of the outer region on the wafer W can be made smaller than the removal rate of the inner region.

Although FIG. 2 illustrates an example in which there are five annular adjustment regions with different compression rates, the number may be one to four, or six or more.
Furthermore, the widths of the multiple adjustment regions may be the same or different.
The compression ratio distribution may be formed so that the compression ratio of the outer region is greater than that of the inner region, or may be formed so that the compression ratio of the outer region is smaller than that of the inner region.
Alternatively, the entire polishing pad 26 may be adjusted by moving the brush 42 in the horizontal direction. When adjusting the entire polishing pad 26, a brush that is the same size as the polishing pad 26 in a plan view or larger than the polishing pad 26 may be used. Alternatively, a plurality of brushes 42 that are different sizes in a plan view may be attached to the holding arm 412, and the brush 42 may be selected depending on the size of the adjustment area of the polishing pad 26.

The control device 5 controls the polishing unit 2 and the polishing pad adjustment unit 4. As shown in FIG. 3, the control device 5 includes an input unit 51, a memory unit 52, and a control unit 53.

The input unit 51 is configured with, for example, a touch panel or physical buttons. The input unit 51 is used, for example, by an operator to input various settings related to polishing of the wafer W, and outputs a signal corresponding to the input operation to the control unit 53.
An example of the settings to be input is the target shape of the polished surface W1 of the wafer W (hereinafter, sometimes referred to as the "target shape of the wafer W").
The input unit 51 may acquire various setting information related to polishing of the wafer W from an external network connected to the control device 5 .

Here, examples of indices representing the target shape of the wafer W include ESFQR, ZDD (Z-height Double Differentiation), and GBIR (Global flatness Back reference Ideal Range).

ESFQR is an index that indicates the site flatness at the outer periphery (edge) of the wafer W. GBIR is an index that indicates the global flatness of the wafer W. ESFQR and GBIR are measured using a flatness measurement device (for example, KLA-Tencor's Wafer Sight 2).

ESFQR is calculated by dividing the outer periphery of the wafer W into a large number (e.g., 72) of fan-shaped regions (sites), and using the intra-site plane calculated using the least squares method to fit the data within the site. ESFQR is the amount of displacement from this intra-site plane, with each site having one piece of data.

ZDD is an index representing the change in inclination (curvature) near the outer periphery of the wafer W. ZDD is obtained by second-order differentiation of the displacement profile of the surface of the wafer W from the center of the wafer W to the outermost periphery.
A positive ZDD value indicates that the surface is displaced in the direction of rebound, whereas a negative ZDD value indicates that the surface is displaced in the direction of sagging. The closer the ZDD value is to 0, the less tilt there is (the flatter the wafer W is) near its outer periphery.

The memory unit 52 stores various pieces of information related to, for example, polishing of the wafer W so that the information can be read by the control unit 53. Examples of the information related to polishing of the wafer W include first correlation information used to calculate the compressibility distribution of the polishing pad 26 and second correlation information used to calculate the adjustment conditions of the polishing pad 26.
The first correlation information and the second correlation information may be stored in, for example, a server device installed at a location remote from the single-sided polishing apparatus 1. In this case, the information stored in the server device may be made available to a plurality of single-sided polishing apparatuses 1.

The first correlation information represents the correlation between the radial compression rate distribution of the polishing pad 26 under preset polishing conditions (e.g., the pressure pressing the wafer W against the polishing pad 26 or the polishing time) and the shape of the wafer W after single-sided polishing.
Here, if the shape of the wafer W before single-sided polishing is always the same, the first correlation information may have the above-described configuration. However, if the shape of the wafer W before single-sided polishing may vary, information representing the correlation between the radial compressibility distribution of the polishing pad 26 and the shape of the wafer W before and after single-sided polishing may be applied as the first correlation information.
Furthermore, if the polishing conditions are always the same, the first correlation information may have the above-described configuration. However, if the polishing conditions vary, the first correlation information may be information representing the correlation between the polishing conditions, the radial compressibility distribution of the polishing pad 26, and the shape of the wafer W before and after single-sided polishing.

The second correlation information represents the correlation between the radial compressibility distribution of the polishing pad 26 and the adjustment conditions of the polishing pad 26. Examples of the adjustment conditions included in the second correlation information include the pressing position of the brush 42 against the polishing pad 26, the pressing amount, and the adjustment time.
The adjustment conditions may further include the size of the brush 42 or the hardness of the bristles.

Note that the first correlation information and second correlation information described above may be information having a table structure, or may be information expressed as a function.

The control unit 53 includes a CPU, which executes programs stored in the memory unit 52 to realize various functions. The control unit 53 includes an information acquisition unit 531, a compression distribution calculation unit 532, a polishing pad adjustment condition calculation unit 533, a polishing pad adjustment control unit 534, and a polishing control unit 535.

The information acquisition unit 531 acquires the first correlation information and the second correlation information from the storage unit 52 .
The information acquisition unit 531 acquires target shape information that indicates the target shape of the wafer W set using, for example, the input unit 51 .

The compression rate distribution calculation unit 532 calculates the radial compression rate distribution of the polishing pad 26 according to the target shape of the wafer W after single-sided polishing, based on the target shape information and first correlation information acquired by the information acquisition unit 531.

If the shape of the wafer W before single-sided polishing may be different, the compressibility distribution calculation unit 532 may determine the radial compressibility distribution of the polishing pad 26 based on the first correlation information including the shape of the wafer W before single-sided polishing. In this case, the information acquisition unit 531 may acquire information representing the shape before single-sided polishing from the input unit 51 or from a shape measurement device.
Furthermore, when the polishing conditions may vary, the compressibility distribution calculation unit 532 may calculate the radial compressibility distribution of the polishing pad 26 based on the first correlation information including the polishing conditions. In this case, the information acquisition unit 531 may acquire information representing the polishing conditions from the input unit 51.

The polishing pad adjustment condition calculation unit 533 calculates the adjustment conditions for adjusting the compression rate distribution of the polishing pad 26 to the compression rate distribution calculated by the compression rate distribution calculation unit 532 based on the second correlation information acquired by the information acquisition unit 531.

The polishing pad adjustment control unit 534 controls the polishing pad adjustment unit 4 to adjust the polishing pad 26 based on the adjustment conditions determined by the polishing pad adjustment condition calculation unit 533.

The polishing control unit 535 controls the polishing unit 2 to rotate the polishing head 21 and polishing pad 26, thereby polishing the polished surface W1 of the wafer W.

<Wafer manufacturing method>
Next, a method for manufacturing a wafer W, including a method for polishing a single side of a wafer W using the single side polishing apparatus 1, will be described.
As shown in FIG. 4, the method for manufacturing the wafer W includes a lifting step (step S1), a block processing step (step S2), a slicing step (step S3), a pre-processing step (step S4), a double-sided simultaneous polishing step (step S5), a single-sided finishing step (step S6) as a finishing step, a cleaning step (step S7), and a final wafer inspection step (step S8).

In the pulling process of step S1, a cylindrical silicon single crystal is pulled from the silicon melt using the Czochralski method.

In the block processing step S2, the outer periphery of the single crystal ingot is ground and notched according to the crystal orientation. The single crystal ingot is then cut into multiple blocks, for example using a band saw.

In the slicing process of step S3, the block is sliced into multiple wafers W, each about 1 mm thick, using an inner diameter cutting machine or wire saw.

In the pre-processing step S4, the wafer W is chamfered and roughly polished (lapped) with, for example, an alumina abrasive to make both surfaces parallel. Then, after etching or other processes are performed as needed, the wafer W is flattened to remove any irregularities on its surface.

In step S5, the double-sided simultaneous polishing process, the pre-processed wafer W is subjected to a mirror finish to enhance its flatness. For example, double-sided polishing (polishing) is performed using colloidal silica liquid or the like to further enhance the flatness and obtain a wafer W with the desired flatness.

The single-side finishing process of step S6 includes the single-side polishing method of the present invention for polishing a wafer W. In the single-side finishing process, the single-side polishing apparatus 1 is used to polish the polished surface W1 of the wafer W obtained in the double-side simultaneous polishing process.
By carrying out polishing in the single-side finishing step, scratches and damage on the polished surface W1 of the wafer W can be removed, and at the same time, the surface roughness of the polished surface W1 can be adjusted.
The single-sided finishing process will be described in detail later.

In the cleaning process of step S7, the wafer W obtained in the single-sided finishing process is cleaned, for example, using an alkaline solution.

In the final wafer inspection process of step S8, a wafer surface inspection device is used to inspect the wafer W for surface particles or scratches. After the necessary quality inspections are carried out, products that pass are packaged and shipped.

Next, the single-side finishing step of step S6 will be described in detail.
As shown in FIG. 5, the single-sided finishing process includes a correlation information acquisition process (step S61), a target shape information acquisition process (step S62), a compression ratio distribution calculation process (step S63), a polishing pad adjustment condition calculation process (step S64), a polishing pad adjustment process (step S65), a wafer setting process (step S66), a polishing process (step S67), and a wafer removal process (step S68).

In the correlation information acquisition process of step S61, the information acquisition unit 531 of the control unit 53 acquires the first correlation information and the second correlation information from the memory unit 52.

In the target shape information acquisition process of step S62, the information acquisition unit 531 acquires target shape information based on the input operation of the input unit 51 by the operator. For example, the information acquisition unit 531 acquires information representing ESFQR, ZDD, or GBIR as target shape information. Note that the information acquisition unit 531 may also acquire target shape information from an external network via the input unit 51.

In the compression rate distribution calculation process of step S63, the compression rate distribution calculation unit 532 calculates the compression rate distribution of the polishing pad 26 to make the shape of the wafer W after single-sided polishing the target shape based on the first correlation information acquired in the correlation information acquisition process and the target shape information acquired in the target shape acquisition process.

Here, when the index represented by the target shape information is ESFQR or ZDD, the multiple regions having different compression rates formed by the process of step S65 are preferably composed of two regions, and include one unadjusted circular region 26A that has not been adjusted, and one adjusted annular region 26B that surrounds the unadjusted region 26A, as shown in Figure 6.
On the other hand, when the index represented by the target shape information is ESFQR, the adjustment region 26B is preferably a circular region with its inner edge located outside the 99% position and inside the 100% position, where the center of rotation C of the polishing pad 26 is the 0% position and the position on the outer edge farthest from the center of rotation C of the polishing pad 26 on the wafer W is the 100% position, and the adjustment region 26B has a greater compression rate than the inner unadjusted region 26A.
When the index represented by the target shape information is ZDD, the adjustment region 26B may be formed in the same position as in the case of ESFQR, or may be formed more inward or outward than in the case of ESFQR.
The compression ratio and width of the adjustment region 26B vary depending on the value of ESFQR or ZDD represented by the target shape information.

Here, to specifically explain the above-mentioned 100% position when the polishing unit 2 is equipped with an oscillation drive unit, when the polishing unit 2 is equipped with one polishing head 21, the 100% position is the position on the outer edge of the wafer W that is farthest from the rotation center C of the polishing pad 26 when the polishing head 21 is positioned at the center of the oscillation width.
Furthermore, when the polishing unit 2 includes a plurality of polishing heads 21, the position on the outer edge of the wafer W that is farthest from the center of rotation C of the polishing pad 26 when each polishing head 21 is disposed at the center of the oscillation width is the 100% position. In other words, when the centers of the plurality of polishing heads 21 are equidistant from the center of the polishing pad 26, the position on the outer edge of the wafer W that is farthest from the center of rotation C of the polishing pad 26 is the 100% position.

By polishing using the polishing pad 26 having such a compressibility distribution, the removal amount of the region excluding the outer periphery of the wafer W polished in the unadjusted region 26A can be made approximately the same, while the removal amount of the outer periphery of the wafer W polished in the adjusted region 26B can be made smaller than that of the inner region. In particular, by making the adjusted region 26B an annular region with its inner edge located outside the 99% position and inside the 100% position, and adjusting only the region of the polishing pad 26 that contacts the outer periphery of the wafer W, it is possible to control the outer periphery shape, such as ESFQR or ZDD, without affecting the shape of the entire wafer W.
The position of the outer edge of the adjustment region 26B is not particularly limited, but FIG. 6 shows the case where it is at the 120% position.

Furthermore, when the index represented by the target shape information is GBIR, the multiple regions having different compression rates formed by the process of step S65 preferably include three or more regions, and the third region from the inside is an annular region whose inner edge is located at a position inside the 100% position, where the rotation center C of polishing pad 26 is the 0% position and the position on the outer edge farthest from the rotation center C of polishing pad 26 on wafer W is the 100% position. For example, it is preferable that the compression rates of the circular unadjusted region whose center is the 0% position and the outer edge is the 25% position, the first annular adjusted region whose inner edge is the 25% position and the outer edge is the 55% position, and the second annular adjusted region whose inner edge is the 55% position and the outer edge is the 120% position are different from each other.
The compression ratio and width of each adjustment region 26B differ depending on the value of GBIR represented by the target shape information.

By polishing using a polishing pad 26 with such a compressibility distribution, the amount of material removed from the wafer W polished in each radial region can be gradually reduced toward the outer regions, allowing for precise control of the shape of the wafer W.

Alternatively, a circular area with the center at 0% and the outer edge at 25% may be used as the adjustment area.
Alternatively, an annular region with an inner edge at 25% position and an outer edge at 55% position may be left as an unadjusted region. In this case, the removal allowance at the center of the wafer W can be made small.
As described above, by changing the compressibility distribution of the polishing pad 26, it is possible to change the distribution of the removal stock of the wafer W within the surface of the wafer W. Furthermore, by selecting the compressibility distribution in accordance with the pre-polishing shape of the wafer W, it is possible to manufacture a flatter wafer W.

In the polishing pad adjustment condition calculation process of step S64, the polishing pad adjustment condition calculation unit 533 calculates adjustment conditions for adjusting the compression rate distribution of the polishing pad 26 to the compression rate distribution calculated in the compression rate distribution calculation process, based on the second correlation information acquired in the correlation information acquisition process.

In the polishing pad adjustment process of step S65, the polishing pad adjustment control unit 534 controls the position adjustment unit 43 and the platen driving unit 27 of the polishing pad adjustment unit 4 based on the adjustment conditions obtained in the polishing pad adjustment condition calculation process to adjust the polishing pad 26.
This polishing pad conditioning step provides a polishing pad 26 that can adjust the shape of the wafer W to a target shape.

In the wafer setting process of step S66, the wafer W obtained in the double-sided simultaneous polishing process is set in the single-sided polishing machine 1.

In the polishing process of step S67, the polishing control unit 535 controls the head lifting unit 23, head driving unit 24, platen driving unit 27, wafer pressure adjustment unit 28 and polishing liquid supply unit 29 of the polishing unit 2 based on the preset polishing conditions, and polishes the wafer W using the polishing pad 26 adjusted in the polishing pad adjustment process.
By this polishing process, a wafer W having a target shape is obtained.

In the wafer removal process of step S68, the wafer W is removed from the single-sided polishing apparatus 1. The removed wafer W is then cleaned in the cleaning process of step S7.

<Effects of First Embodiment>
According to the first embodiment, the single-sided polishing apparatus 1 includes a compression rate distribution calculation process for calculating the radial compression rate distribution of the polishing pad 26 that can shape the wafer W after polishing into the target shape, a polishing pad adjustment process for adjusting the polishing pad 26 so that it has the calculated compression rate distribution, and a polishing process for polishing the wafer W using the adjusted polishing pad 26.
In this way, by adjusting the radial compressibility distribution of the polishing pad 26 to match the target shape of the wafer W, a wafer W having a desired shape can be obtained by polishing using the polishing pad 26.

The polishing pad 26 is a suede type polishing pad.
Therefore, a compressibility distribution can be easily formed in the polishing pad 26 .

As a method for forming a compression rate distribution in the polishing pad 26, a method is used in which the suede-type polishing pad 26 is rotated while the brush 42 is pressed against the polishing pad 26, thereby forming an annular area with a compression rate different from other areas.
Therefore, a compressibility distribution can be formed in the polishing pad 26 by the simple method of simply rotating the polishing pad 26 using the brush 42 .
In particular, by adjusting the suede-type polishing pad 26 using the brush 42, whose bristles deform, rather than using a grinding stone to scrape the polishing pad 26, it is possible to fine-tune the compression ratio without substantially changing the thickness of the polishing pad 26. Furthermore, when adjusting the polishing pad 26 using a grinding stone, there is a risk that components of the grinding stone will adhere to the polishing pad 26, which can worsen light point defects (LPDs), but by using the brush 42, it is possible to suppress the deterioration of LPDs.

When ESFQR is set as an index representing the target shape of the wafer W, the polishing pad adjustment unit 4 preferably forms an annular region in the polishing pad 26 so as to include a circular unadjusted region 26A and an annular adjusted region 26B having different compression rates, based on the control of the polishing pad adjustment controller 534. In this case, the adjusted region 26B is formed in an annular shape with its inner edge located outside the 99% position and inside the 100% position, and has a larger compression rate than the unadjusted region 26A.
With this configuration, the shape of the outer periphery of the wafer W can be controlled with higher precision.

When GBIR is set as an index representing the target shape of the wafer W, it is preferable that the polishing pad adjustment unit 4, based on the control of the polishing pad adjustment control unit 534, form a circular region in the polishing pad 26 so that three or more regions with different compression rates are arranged radially.
With this configuration, the overall shape of the wafer W can be controlled with higher precision.

The polishing pad adjustment unit 4 positions the brush 42 at a height position according to the compression rate under the control of the polishing pad adjustment control unit 534 .
Therefore, the compressibility of the polishing pad 26 can be controlled with high precision by simply adjusting the height position of the brush 42. As a result, the shape of the wafer W can be controlled with higher precision.

Second Embodiment
Next, a second embodiment of the present invention will be described.
In the second embodiment, a configuration will be described in which a plurality of single-side polishing apparatuses 1 are used to polish the polished surfaces W1 of the wafers W into different shapes.
Since the configuration of the single-sided polishing apparatus 1 used in the second embodiment is the same as that of the single-sided polishing apparatus 1 of the first embodiment, the following description will focus on a method for manufacturing a wafer W, including a method for polishing a single side of a wafer W. In addition, in the description of the method for manufacturing a wafer W, the same steps as those in the first embodiment are given the same names and symbols, and the description will be simplified.

As shown in Figure 4, the manufacturing method of the wafer W in the second embodiment differs from the manufacturing method in the first embodiment only in the single-sided finishing process (step S9) as a finishing process.

As shown in FIG. 7, the single-sided finishing process of the second embodiment includes a polishing device preparation process (step S91), a polishing device selection process (step S92), a wafer setting process (step S93), a polishing process (step S67), and a wafer removal process (step S68).

In the polishing apparatus preparation process of step S91, a correlation information acquisition process (step S61), a target shape information acquisition process (step S62), a compression rate distribution calculation process (step S63), a polishing pad adjustment condition calculation process (step S64), and a polishing pad adjustment process (step S65) based on different target shapes are performed on multiple single-sided polishing apparatuses 1 so that the compression rate distributions of the polishing pads 26 respectively equipped on the multiple single-sided polishing apparatuses 1 are different from each other.
With this polishing apparatus preparation process, for example, when three single-sided polishing apparatuses 1 are used, by performing each process based on three different target shapes, it is possible to prepare three single-sided polishing apparatuses 1 having polishing pads 26 with different compression rate distributions.

In addition, the first correlation information and the second correlation information may be stored in a server device instead of being stored in the memory unit 52 of each single-sided polishing apparatus 1, and the information acquisition unit 531 of each single-sided polishing apparatus 1 may acquire the first correlation information and the second correlation information from the server device.
Furthermore, the information acquisition unit 531 of each single-sided polishing apparatus 1 may acquire the target shape information from the input unit 51 of each single-sided polishing apparatus 1 .
Alternatively, an operator may input a target shape into a management device that collectively manages a plurality of single-side polishing machines 1, and the information acquisition unit 531 may acquire target shape information corresponding to the input setting.

In the polishing apparatus selection step of step S92, a single-side polishing apparatus 1 for polishing the wafer W to a set target shape is selected from a plurality of single-side polishing apparatuses 1.
The selection of the single-side polishing apparatus 1 may be performed by the management apparatus based on information corresponding to the setting input, in which case the operator sets and inputs the set target shape to the management apparatus.
Furthermore, the selection of the single-sided polishing apparatus 1 may be performed at the discretion of the operator.

In the wafer setting process of step S93, the wafer W obtained in the double-sided simultaneous polishing process is set in the single-sided polishing machine 1 selected in the polishing machine selection process.

The polishing process in step S67 and the wafer removal process in step S68 are performed on the single-sided polishing machine 1 selected in the polishing machine selection process.

<Effects of the Second Embodiment>
According to the second embodiment, the radial compression rate distributions of the polishing pads 26 of the multiple single-sided polishing apparatuses 1 are adjusted to be different from each other, and the wafer W is polished using the single-sided polishing apparatus 1 selected according to the set target shape.
Therefore, wafers W having different desired shapes can be obtained at the same time.

[Modification]
Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and various improvements and design changes that do not deviate from the gist of the present invention are also included in the present invention.

For example, a method of fixing the brush 42 and rotating the polishing pad 26 has been exemplified as a method of forming an annular region on the polishing pad 26 with a different compression rate from other regions. However, the brush 42 may also be moved in a circular motion without rotating the polishing pad 26 or while rotating the polishing pad 26.

As a method for adjusting the amount of pressure of the brush 42 against the polishing pad 26, a method in which the height position of the polishing pad 26 is fixed and the height position of the brush 42 is adjusted has been exemplified. However, the height position of the polishing pad 26 may also be changed while the height position of the brush 42 is fixed or changed.

Next, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1: Relationship between polishing pad conditioning time and polishing pad properties after conditioning
First, the single-side polishing apparatus 1 of the first embodiment was prepared. Also, a plurality of suede-type polishing pads 26 having the following characteristics were prepared.
Thickness of the polishing pad 26: 0.94 mm
Compression rate of polishing pad 26: 26.6%

The polishing pad 26 and a nylon brush 42 with bristles of 5 mm in length were attached to the single-side polishing device 1 .
The horizontal position of the brush 42 was adjusted to adjust the adjustment area 26B shown in Fig. 6. At this time, the position of the inner edge of the adjustment area 26B was at the 99.7% position, and the position of the outer edge was at the 120% position.
The height position of the brush 42 was adjusted so that the amount of pressure of the brush 42 against the polishing pad 26 was 0.5 mm. The amount of pressure of the brush 42 was 0 mm when the tips of the bristles were in contact with the polishing pad 26 without bending the bristles.

Then, the surface plate 25 was rotated and adjustment was performed for 30 seconds, to obtain the polishing pad 26 of Example 1-1.
In addition, after replacing the polishing pad 26 of the single-sided polishing apparatus 1 with a polishing pad 26 that had not been adjusted as a whole, the polishing pad 26 was adjusted under the same conditions as the polishing pad 26 of Example 1-1, except that the adjustment time was set to 60 seconds, thereby obtaining the polishing pad 26 of Example 1-2.

The thickness and compression ratio of the outer periphery (adjustment region) of the polishing pads 26 of Examples 1-1 and 1-2 were measured. The results are shown in Table 1.
The polishing pad 26 of Comparative Example 1 is a polishing pad 26 that has not been adjusted as a whole.

As shown in Table 1, it was confirmed that the thickness of the outer periphery of the polishing pad 26 was almost the same regardless of whether the outer periphery of the polishing pad 26 was adjusted or the length of the adjustment time, while the compression rate of the polishing pad 26 increased as the adjustment time increased.
From this, it was confirmed that the compression ratio can be adjusted without changing the overall thickness of the polishing pad 26 by adjusting the length of the adjustment time.

Example 2: Relationship between compressibility distribution of polishing pad and shape of wafer after polishing
First, a plurality of wafers W each having a diameter of 300 mm and having the same shape of polished surface W1 were prepared. Also, the polishing pad 26 of Comparative Example 1 (the polishing pad 26 having a uniform overall compression rate of 26.6%) was attached to the single-side polishing apparatus 1. Then, the wafers W were polished under preset polishing conditions to obtain wafers W of Comparative Example 2.
In addition, another wafer W was polished under the same conditions as the wafer W of Comparative Example 2, except that the polishing pad 26 of Example 1-1 (polishing pad 26 having a compression rate of 26.6% in the region from the center to the 99.7% position and a compression rate of 27.3% in the region from the 99.7% position to the 120% position) was used, thereby obtaining the wafer W of Example 2-1.
Similarly, another wafer W was polished under the same conditions as the wafer W of Comparative Example 2, except that the polishing pad 26 of Example 1-2 (polishing pad 26 having a compression rate of 26.6% in the region from the center to the 99.7% position and a compression rate of 27.8% from the 99.7% position to the 120% position) was used, to obtain the wafer W of Example 2-2.

The polishing allowance shapes of the wafers W of Comparative Example 2 and Examples 2-1 and 2-2 were measured. The measurement results are shown in FIG.
In the graph shown in Figure 8, the horizontal axis represents the distance from the center of the wafer W, and the vertical axis represents the amount of displacement from a reference plane obtained by calculating a differential profile of the thickness of the wafer W before and after polishing and using the least squares method within the site in that differential profile.

As shown in Figure 8, it was confirmed that the removal allowance at the outer periphery of the wafer W in Example 2-2 was the smallest, while the removal allowance at the outer periphery of the wafer W in Comparative Example 2 was the largest. In other words, it was confirmed that the flatness at the outer periphery of the wafer W in Example 2-2 was the highest, while the flatness at the outer periphery of the wafer W in Comparative Example 2 was the lowest.

In addition, ESFQR_max_1mm and ZDD of the polished surface W1 were measured. The measurement results are shown in Table 2.
ESFQR_max_1mm represents the largest displacement amount among the displacement amounts of each site when the measurement target is an area excluding a range of 1 mm from the outer edge of each site.

As shown in Table 2, it was confirmed that Example 2-2 had the smallest absolute values of ESFQR_max_1mm and ZDD, while Comparative Example 2 had the largest absolute values of ESFQR_max_1mm and ZDD.

From the results shown in Figure 8 and Table 2, it was confirmed that the greater the compression ratio of the outer periphery of the polishing pad 26 compared to the inner region, the smaller the removal amount of the outer periphery and the higher the flatness of the polished surface W1.

Example 3: Relationship between the amount of brush pressure against the polishing pad and the properties of the polishing pad after adjustment
First, a plurality of suede-type polishing pads 26 having the following characteristics were prepared.
Thickness of the polishing pad 26: 0.93 mm
Compressibility of polishing pad 26: 24.7%

The above-mentioned polishing pad 26 and a brush 42 made of nylon with 5 mm bristles were attached to the single-sided polishing device 1. The horizontal position of the brush 42 was adjusted to adjust the adjustment area 26B to the same position and shape as in Example 1. The height position of the brush 42 was also adjusted so that the amount of pressure of the brush 42 against the polishing pad 26 was 0.5 mm.

Then, the surface plate 25 was rotated and adjustment was performed for 30 seconds, to obtain the polishing pad 26 of Example 3-1.
In addition, the polishing pad 26 of the single-sided polishing apparatus 1 was replaced with a polishing pad 26 that had not been adjusted as a whole, and then adjustment was performed under the same conditions as the polishing pad 26 of Example 3-1, except that the pressing amount was set to 0.8 mm, thereby obtaining the polishing pad 26 of Example 3-2.
Furthermore, the polishing pad 26 of the single-sided polishing apparatus 1 was replaced with a polishing pad 26 that had not been adjusted as a whole, and then adjustment was performed under the same conditions as the polishing pad 26 of Example 3-1, except that the pressing amount was set to 1.1 mm, thereby obtaining the polishing pad 26 of Example 3-3.

The thickness and compression ratio of the outer periphery (adjustment region) of the polishing pads 26 of Examples 3-1, 3-2, and 3-3 were measured. The results are shown in Table 3.
The polishing pad 26 of Comparative Example 3 is a polishing pad 26 that has not been adjusted as a whole.

As shown in Table 3, regardless of whether the outer periphery of the polishing pad 26 is adjusted or the amount of pressure applied by the brush 42, the thickness of the outer periphery of the polishing pad 26 is almost the same, while it was confirmed that the greater the amount of pressure applied, the greater the compression rate of the polishing pad 26.
From this, it was confirmed that the compressibility can be adjusted without changing the overall thickness of the polishing pad 26 by adjusting the amount of pressure of the brush 42 against the polishing pad 26 .
Furthermore, taking into consideration the results of Example 1, it was confirmed that by adjusting the length of the adjustment time in addition to the amount of pressure of the brush 42 against the polishing pad 26, the compression ratio can be adjusted more precisely without changing the overall thickness of the polishing pad 26.

Example 4: Relationship between the amount of brush pressure against the polishing pad and the shape of the wafer after polishing
First, a plurality of wafers W each having a diameter of 300 mm and having the same shape of polished surface W1 were prepared. Also, the polishing pad 26 of Comparative Example 3 (the polishing pad 26 having a uniform overall compressibility of 24.7%) was attached to the single-side polishing apparatus 1.
The wafer W was then polished under the same polishing conditions as in Example 2 to obtain a wafer W of Comparative Example 4.
In addition, another wafer W was polished under the same conditions as the wafer W of Comparative Example 4, except that the polishing pad 26 of Example 3-1 (polishing pad 26 having a compression rate of 24.7% in the region from the center to the 99.7% position and a compression rate of 26.5% from the 99.7% position to the 120% position) was used, to obtain the wafer W of Example 4-1.
Similarly, another wafer W was polished under the same conditions as the wafer W of Comparative Example 4, except that the polishing pad 26 of Example 3-2 (polishing pad 26 having a compression rate of 24.7% in the region from the center to the 99.7% position and a compression rate of 26.8% in the region from the 99.7% position to the 120% position) was used, thereby obtaining the wafer W of Example 4-2.
In addition, another wafer W was polished under the same conditions as the wafer W of Comparative Example 4, except that the polishing pad 26 of Example 3-3 (polishing pad 26 having a compression rate of 24.7% in the region from the center to the 99.7% position and a compression rate of 27.2% in the region from the 99.7% position to the 120% position) was used, thereby obtaining the wafer W of Example 4-3.

The ESFQR_max_1mm and ZDD of the polished surface W1 were measured for wafers W of Comparative Example 4 and Examples 3-1, 3-2, and 3-3. The measurement results are shown in Table 4.

As shown in Table 4, it was confirmed that the absolute values of ESFQR_max_1mm and ZDD decreased in the order of Comparative Example 4, Example 4-1, Example 4-2, and Example 4-3.
From this, it was confirmed that, as in Example 2, the greater the compression rate of the outer periphery of the polishing pad 26 compared to its inner region, the smaller the machining allowance of the outer periphery and the higher the flatness of the polished surface W1.

1...single-sided polishing apparatus, 4...polishing pad adjustment unit, 5...controller, 21...polishing head, 24...head drive unit (rotation drive unit), 26...polishing pad, 27...plate drive unit (rotation drive unit), 42...brush, 43...position adjustment unit, 532...compressibility distribution calculation unit, 533...polishing pad adjustment condition calculation unit, 534...polishing pad adjustment control unit, 535...polishing control unit, W...wafer.

Claims (9)

A single-sided polishing method for a wafer using a single-sided polishing apparatus, which polishes a wafer by pressing the wafer held by a polishing head against a suede-type polishing pad having a nap layer and larger than the wafer, and rotating the polishing head and the polishing pad, comprising:
a compressibility distribution calculation step of calculating a compressibility distribution in the radial direction of the polishing pad according to a target shape of the wafer after polishing;
a polishing pad adjustment step in which, as a process for adjusting the polishing pad to have the compressibility distribution, a process is performed in which a brush is pressed against the polishing pad while rotating the polishing pad, thereby forming an annular region on the polishing pad having a compressibility different from that of other regions ;
a polishing step of polishing the wafer using the polishing pad having the compressibility distribution. 2. The method for polishing a single side of a wafer according to claim 1 ,
The polishing step includes polishing the wafer in a state where the wafer is positioned outside the center of rotation of the polishing pad,
The polishing pad conditioning step includes forming one annular area using the brush,
A method for polishing a single side of a wafer, wherein the annular region has an inner edge located outside the 99% position and inside the 100% position, where the center of rotation of the polishing pad is the 0% position and the position on the outer edge of the wafer farthest from the center of rotation is the 100% position, and the region has a higher compression rate than the inner region. 3. The method for polishing a single side of a wafer according to claim 2 ,
A single-sided polishing method for a wafer, wherein the indicator of the target shape of the wafer is ESFQR. 2. The method for polishing a single side of a wafer according to claim 1 ,
The polishing step includes polishing the wafer in a state where the wafer is positioned outside the center of rotation of the polishing pad,
The polishing pad conditioning step includes forming an annular region using the brush so that three or more regions having different compression rates are arranged in a radial direction,
A method for polishing one side of a wafer, wherein the third innermost region among the three or more regions with different compression rates is a circular region whose inner edge is located inside the 100% position when the rotation center of the polishing pad is the 0% position and the position on the outer edge of the wafer farthest from the rotation center is the 100% position. 5. The method for polishing a single side of a wafer according to claim 4 ,
A single-side polishing method for a wafer, wherein the indicator of the target shape of the wafer is GBIR. 2. The method for polishing a single side of a wafer according to claim 1,
a polishing apparatus preparation step of performing the compressibility distribution calculation step and the polishing pad adjustment step based on the different target shapes for the plurality of single-sided polishing apparatuses so as to make the compressibility distributions of the polishing pads provided for the plurality of single-sided polishing apparatuses different from one another;
a polishing apparatus selection step of selecting the single-sided polishing apparatus capable of polishing the wafer to be polished to a set target shape from among the plurality of single-sided polishing apparatuses,
The method for polishing a single side of a wafer, wherein the polishing step polishes the wafer using the single side polishing machine selected in the polishing machine selection step. A method for manufacturing a wafer, comprising:
a finishing step of finishing the wafer,
A method for manufacturing a wafer, wherein in the finishing step, the wafer is polished by the method for polishing a single side of a wafer according to claim 1. A single-side polishing apparatus that polishes a wafer by pressing a wafer held by a polishing head against a suede-type polishing pad that has a nap layer and is larger than the wafer, and rotating the polishing head and the polishing pad,
a polishing pad adjustment unit having a brush and adjusting the polishing pad;
a rotation drive unit that rotates the polishing head and the polishing pad;
a control device;
The control device
a compressibility distribution calculation unit that calculates a compressibility distribution in the radial direction of the polishing pad according to a target shape of the wafer after polishing;
a polishing pad adjustment control unit that controls the polishing pad adjustment unit to adjust the polishing pad to have the compressibility distribution, by rotating the polishing pad and pressing the brush against the polishing pad to form an annular region having a compressibility different from that of other regions ;
a polishing control unit that controls the rotation drive unit to polish the wafer using the polishing pad having the compressibility distribution. 9. The single-side polishing apparatus for wafers according to claim 8 ,
the polishing pad adjustment unit includes a position adjustment unit that adjusts the position of the brush,
The polishing pad adjustment control unit controls the position adjustment unit to position the brush at a height position according to the compression ratio.