Single-sided wafer polishing method, wafer manufacturing method, and single-sided wafer polishing apparatus

Abstract

To provide a wafer one-side polishing method that can obtain a wafer in a desired shape.SOLUTION: A wafer one-side polishing method, which polishes a wafer held by a polishing head by rotating a polishing head and a suede-type polishing pad which is larger than the wafer while pressing the wafer against the polishing pad, comprises: an oscillation-condition calculating step of determines an oscillation condition for the polishing head, on the basis of machining allowance in polishing that is performed using the polishing pad having a compressibility distribution in a radial direction while oscillating the polishing head; and a polishing step of polishing the wafer using the polishing pad, while oscillating the polishing head in a direction which is parallel to a polishing surface of the polishing pad, on the basis of the oscillation condition.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] 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. [Background technology]

[0002] 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 removal. One known technique for addressing this effect is to use a pad with a porosity that varies circumferentially to improve polishing performance (see, for example, Patent Document 1). Another known technique is to modify the surface shape of the polishing pad so as 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 pad (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-35773 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-187059 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as the demand for wafer shape accuracy, particularly ESFQR (Edge Site Flatness Front Reference Least Square Deviation) in the peripheral area of ​​the wafer, increases, it is becoming difficult to obtain a wafer with the desired shape simply by adjusting the porosity of the polishing pad or making the overall surface shape uniform, as in the techniques described in Patent Documents 1 and 2.

[0005] An object of the present invention is to provide 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, which are capable of obtaining a wafer of a desired shape. [Means for solving the problem]

[0006] The single-sided polishing method for wafers of the present invention is a method for polishing a wafer by pressing a wafer held by a polishing head against a suede-type polishing pad larger than the wafer and rotating the polishing head and the polishing pad, and comprises: an oscillation condition calculation step for determining oscillation conditions for the polishing head based on the removal rate in polishing performed using the polishing pad having a radial compressibility distribution while oscillating the polishing head; and a polishing step for polishing the wafer using the polishing pad while oscillating the polishing head based on the oscillation conditions.

[0007] In the method for polishing one side of a wafer of the present invention, it is preferable to include a polishing pad adjustment step in which a circular region having a compression rate different from other regions is formed on the polishing pad by rotating the polishing pad and pressing a brush against the polishing pad.

[0008] In the method for polishing a single side of a wafer according to 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.

[0009] In the single-sided polishing method for wafers of the present invention, the polishing process polishes the wafer while the wafer is positioned outside the center of rotation of the polishing pad, and the polishing pad adjustment process forms a single annular area using the brush, and the annular area is an area whose inner edge is 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 farthest from the center of rotation on the wafer when the polishing pad is not oscillating is defined as the 100% position, and the area has a higher compression rate than the inner area.

[0010] The method for producing a wafer of the present invention includes a finishing step for finishing the wafer, in which the wafer is polished by the above-described single-side polishing method for a wafer.

[0011] The single-sided wafer polishing apparatus of the present invention is a single-sided wafer polishing apparatus that 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, and is equipped with a rotation drive unit that rotates the polishing head and the polishing pad, an oscillation drive unit that oscillates the polishing head in a direction parallel to the polishing surface of the polishing pad, and a control device, wherein the control device is equipped with an oscillation condition calculation unit that determines the oscillation conditions of the polishing head based on the removal rate in polishing performed using the polishing pad having a radial compressibility distribution while oscillating the polishing head, and a polishing control unit that controls the rotation drive unit and the oscillation drive unit to oscillate the polishing head based on the oscillation conditions and polish the wafer using the polishing pad. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a single-sided polishing apparatus according to an embodiment. [Figure 2] 1A to 1C are plan views illustrating a method for adjusting a polishing pad according to an embodiment. [Figure 3] 1 is a block diagram showing a schematic configuration of a control device according to an embodiment; [Figure 4] 1 is a flowchart showing a method for manufacturing a wafer according to an embodiment. [Figure 5] 10 is a flowchart showing a single-side finishing process according to an embodiment. [Figure 6] FIG. 2 is a schematic diagram showing an example of the compressibility distribution of a polishing pad according to an embodiment. [Figure 7] 10 is a graph showing the relationship between the amount of pressing of the brush against the polishing pad, the swing width of the polishing head, and the ESFQR of the wafer after polishing in Example 1. [Figure 8] 10 is a graph showing the pre-polishing shape of a wafer according to Example 2. [Figure 9] 10 is a graph showing the relationship between the oscillation width of the polishing head and the shape of the wafer after polishing in polishing using a polishing pad having the compressibility distribution according to Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Embodiment] Hereinafter, an embodiment of the present invention will be described.

[0014] <Configuration of single-sided polishing machine> First, a single-side polishing apparatus 1 according to an 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.

[0015] 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, a polishing liquid supply unit 29, and a swing driving unit 30. Although the polishing unit 2 may be provided with 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.

[0016] Each polishing head 21 is formed in a disk shape. Each polishing head 21 holds the surface (back surface) of the wafer W opposite to the surface W1 (front surface) to be polished by the surface tension of water or the like.

[0017] A back pad 211 is disposed on the lower surface of the polishing head 21 so as to cover the entire lower surface. The back pad 211 is made of, for example, a porous resin material, and can contain liquid such as water.

[0018] A ring-shaped retainer ring 212 is disposed on the outer periphery of the lower surface of the back pad 211. The retainer ring 212 comes into contact with the outer periphery of the wafer W positioned inside the retainer ring 212, and holds the wafer W so that it does not come out of the gap between the back pad 211 and the polishing pad 26.

[0019] A cylindrical head rotation shaft member 213 is disposed at the center of the top surface of each polishing head 21.

[0020] The head holding unit 22 holds the upper end portion 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 the multiple polishing heads 21 are lined up at equal intervals on the circumference of a predetermined circle.

[0021] The head lifting unit 23 lifts and lowers the head holding unit 22 .

[0022] The head driving unit 24 is disposed inside the head holding unit 22. The head driving unit 24 is configured by, for example, a motor, and rotates a head rotation shaft member 213 connected to the rotation shaft of the motor.

[0023] The surface plate 25 is formed in a disk shape and is disposed below the plurality of polishing heads 21. A cylindrical surface plate rotating shaft member 251 is disposed in the center of the lower surface of the surface plate 25.

[0024] 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 be able 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.

[0025] The platen driving unit 27 is configured by, for example, a motor, and rotates a platen rotating shaft member 251 connected to the rotating shaft of the motor in the same direction as the polishing head 21 or in the opposite direction.

[0026] The wafer pressure adjusting unit 28 is a fixed pressure type device that adjusts the pressure that presses the wafer W against the polishing pad 26. In the fixed pressure type, the entire polishing head 21 is pressed down by cylinder pressure, and the polishing head 21 is pressed against the upper 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.

[0027] The polishing liquid supply unit 29 supplies a slurry-like polishing liquid to the polishing pad 26 through a nozzle 291. The surface W1 to be polished of the wafer W is polished using this polishing liquid.

[0028] The swing drive unit 30 swings each polishing head 21 in a direction parallel to the polishing surface of the polishing pad 26. For example, the swing drive unit 30 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 about the rotation axis D of the polishing head 21.

[0029] The polishing pad conditioning unit 4 conditions 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, and the surface plate 25 and surface plate drive unit 27 described above.

[0030] The brush holder 41 includes a rod-shaped brush rotating shaft member 411 that extends vertically. A holding arm 412 that extends horizontally is disposed on the upper end of the brush rotating shaft member 411.

[0031] 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.

[0032] 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.

[0033] Here, a method for adjusting polishing pad 26 using polishing pad adjusting unit 4 so that it has a compressibility distribution will be described. 2, under the control of the control device 5, 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. Next, under the control of the control device 5, the surface plate driving unit 27 rotates the surface plate 25. 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 polishing pad 26 against which brush 42 is pressed to a predetermined position, second adjustment area 262, third adjustment area 263, and fourth adjustment area 264, each indicated by two-dot chain lines, are adjusted.

[0034] 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.

[0035] 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.

[0036] 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, multiple brushes 42 of 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.

[0037] The control device 5 controls the polishing unit 2 and the polishing pad adjustment unit 4. As shown in FIG.

[0038] 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. Examples of the settings to be input include the target shape of the polished surface W1 of the wafer W (hereinafter, sometimes referred to as the "target shape of the wafer W") and adjustment conditions for the polishing pad 26. 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.

[0039] Here, examples of indices that represent the target shape of the wafer W include ESFQR, ZDD (Z-height Double Differentiation), and GBIR (Global flatness Back reference Ideal Range).

[0040] ESFQR is an index indicating the site flatness at the outer periphery (edge) of the wafer W. GBIR is an index indicating the global flatness of the wafer W. ESFQR and GBIR are measured by a flatness measuring device (for example, Wafer sight 2 manufactured by KLA-Tencor).

[0041] The outer periphery of the wafer W is divided into many (e.g., 72) fan-shaped regions (sites), and the ESFQR is calculated using the least squares method to determine the plane within the site. The ESFQR is the amount of displacement from this plane within the site, and each site has one piece of data.

[0042] The ZDD is an index that represents the change in inclination (curvature) near the outer periphery of the wafer W. The 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, while a negative 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.

[0043] The memory unit 52 stores various 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 adjustment conditions of the polishing pad 26 and second correlation information used to calculate the oscillation conditions of the polishing head 21. The first correlation information and the second correlation information may be stored in, for example, a server device installed in 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 multiple single-sided polishing apparatuses 1.

[0044] The first 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 first 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.

[0045] The second correlation information represents the correlation between the radial compressibility distribution of the polishing pad 26, the target removal amount of the wafer W (radial target removal amount distribution), and the oscillation conditions of the polishing head 21 under preset polishing conditions (for example, the pressure for pressing the wafer W against the polishing pad 26 or the polishing time). Examples of the oscillation conditions of the polishing head 21 include the oscillation width (reciprocating movement width) L and the oscillation speed shown in FIG. If the polishing conditions are always the same, the second correlation information may have the above-described structure. However, if the polishing conditions vary, the second correlation information may be information representing the correlation between the polishing conditions, the compressibility distribution of the polishing pad 26, the target removal amount of the wafer W, and the oscillation conditions of the polishing head 21.

[0046] The first correlation information and the second correlation information may be information having a table structure, or may be information expressed as a function.

[0047] The control unit 53 includes a CPU, and realizes various functions by the CPU executing programs stored in the storage unit 52. The control unit 53 includes an information acquisition unit 531, a polishing pad adjustment condition calculation unit 532, a polishing pad adjustment control unit 533, a target removal amount calculation unit 534, a swing condition calculation unit 535, and a polishing control unit 536.

[0048] 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, for example, compression rate distribution information representing the compression rate distribution of the polishing pad 26 set using the input unit 51. Examples of the content represented by the compression rate distribution information include the position, width, compression rate, and number of adjustment regions corresponding to the type of index (ESFQR, ZDD, or GBIR) of the target shape of the wafer W. Note that, for example, when an operator sets the type of index of the target shape of the wafer W using the input unit 51, the information acquisition unit 531 may acquire compression rate distribution information corresponding to the type of index. In this case, it is preferable that information representing the relationship between the type of index of the target shape and the compression rate distribution of the polishing pad 26 be stored in the storage unit 52. The information acquiring unit 531 acquires pre-polishing shape information that represents the shape of the wafer W before single-side polishing (hereinafter, may be referred to as the "pre-polishing shape of the wafer W"). The information acquiring unit 531 may acquire the pre-polishing shape information from the input unit 51 or may acquire it from a shape measuring device. The information acquisition unit 531 acquires target shape information that indicates the target shape of the wafer W set using the input unit 51, for example.

[0049] The polishing pad adjustment condition calculation unit 532 determines, based on the first correlation information acquired by the information acquisition unit 531, adjustment conditions for changing the compression rate distribution of the polishing pad 26 to the compression rate distribution represented by the compression rate distribution information acquired by the information acquisition unit 531.

[0050] The polishing pad adjustment control unit 533 controls the polishing pad adjustment unit 4 so as to adjust the polishing pad 26 based on the adjustment conditions determined by the polishing pad adjustment condition calculation unit 532 .

[0051] The target removal amount calculation unit 534 calculates a target removal amount for forming the wafer W into the target shape based on the pre-polishing shape information and target shape information acquired by the information acquisition unit 531.

[0052] Based on the compression rate distribution information and the second correlation information acquired by the information acquisition unit 531, the oscillation condition calculation unit 535 determines the oscillation conditions of the polishing head 21 that allow the removal amount in polishing performed using the polishing pad 26 having a compression rate distribution in the radial direction to be the target removal amount while oscillating the polishing head 21.

[0053] The polishing control unit 536 controls the polishing unit 2 to rotate the polishing head 21 and the polishing pad 26, and to oscillate the polishing head 21 under the oscillation conditions calculated by the oscillation condition calculation unit 535, thereby polishing the polished surface W1 of the wafer W.

[0054] <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 manufacturing method of the wafer W includes a lifting process (step S1), a block processing process (step S2), a slicing process (step S3), a pre-processing process (step S4), a double-sided simultaneous polishing process (step S5), a single-sided finishing process (step S6) as a finishing process, a cleaning process (step S7), and a final wafer inspection process (step S8).

[0055] In the pulling process of step S1, a cylindrical silicon single crystal is pulled from a silicon melt using the Czochralski method.

[0056] In the block processing step S2, the outer periphery of the single crystal ingot is ground, notched according to the crystal orientation, and then cut into a plurality of blocks using, for example, a band saw.

[0057] In the slicing step of step S3, the block is sliced ​​into a plurality of wafers W each having a thickness of, for example, about 1 mm using an inner diameter cutting machine or a wire saw.

[0058] In the pre-processing step S4, chamfering is performed and rough polishing (lapping) is performed with, for example, an alumina abrasive so that both surfaces of the wafer W are parallel. Then, after etching or the like is performed as necessary, a planarization process is performed to remove unevenness from the surface of the wafer W.

[0059] In the double-side simultaneous polishing process of step S5, the pre-processed wafer W is subjected to a mirror finish to increase the flatness. For example, double-side polishing is performed using colloidal silica liquid or the like to further increase the flatness and obtain a wafer W with a predetermined flatness.

[0060] 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, a 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 performing 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.

[0061] In the cleaning step of step S7, the wafer W obtained in the single-side finishing step is cleaned with, for example, an alkaline solution.

[0062] In the final wafer inspection process of step S8, a wafer surface inspection device or the like is used to inspect the surface particles or scratches present on the wafer W. After the necessary quality inspections are carried out, the products that pass are packaged and shipped.

[0063] 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 compression ratio distribution information acquisition process (step S62), a polishing pad adjustment condition calculation process (step S63), a polishing pad adjustment process (step S64), a pre-polishing shape information acquisition process (step S65), a target shape information acquisition process (step S66), a target removal amount calculation process (step S67), an oscillation condition calculation process (step S68), a wafer setting process (step S69), a polishing process (step S70), and a wafer removal process (step S71).

[0064] In the correlation information acquisition step 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 storage unit 52.

[0065] In the compression ratio distribution information acquisition step of step S62, the information acquisition unit 531 acquires the compression ratio distribution information based on the input operation of the input unit 51 by the operator. Note that the information acquisition unit 531 may acquire the compression ratio distribution information from an external network via the input unit 51.

[0066] Here, when the index representing the target shape corresponding to the content of the compression ratio distribution information is ESFQR or ZDD, the multiple regions having different compression ratios represented by the compression ratio distribution information are preferably composed of two regions, and include one unadjusted circular region 26A and one adjusted annular region 26B surrounding the unadjusted region 26A, as shown in FIG. 6. On the other hand, when the index corresponding to the content of the compression rate distribution information is ESFQR, the adjustment region 26B is preferably a circular region whose inner edge is located outside the 99% position and inside the 100% position, where the rotation center C of the polishing pad 26 is the 0% position and the position on the outer edge farthest from the rotation center C of the polishing pad 26 on the wafer W when the polishing head 21 is not oscillating is the 100% position, and is a region with a higher compression rate than the inner unadjusted region 26A. When the index corresponding to the content of the compression ratio distribution information is ZDD, the adjustment region 26B may be formed in the same position as in the case of ESFQR, or may be formed inside or outside compared to the case of ESFQR.

[0067] Here, to explain the above-mentioned 100% position in more detail, when the polishing unit 2 has 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 L. Furthermore, when the polishing unit 2 includes multiple polishing heads 21, the 100% position is 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 L. In other words, when the centers of the multiple polishing heads 21 are equidistant from the center of the polishing pad 26, the 100% position is the position on the outer edge of the wafer W that is farthest from the center of rotation C of the polishing pad 26.

[0068] 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 of the wafer W, such as ESFQR or ZDD, without affecting the overall shape of the 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 a position of 120%.

[0069] Furthermore, when the index corresponding to the content of the compression ratio distribution information is GBIR, the multiple regions having different compression ratios represented by the compression ratio distribution information preferably include three or more regions, and the third region from the inside is preferably a circular region whose inner edge is located at a position inside the 100% position, where the rotation center C of the polishing pad 26 is defined as the 0% position and the position on the outer edge of the wafer W farthest from the rotation center C of the polishing pad 26 when the polishing head 21 is not oscillating is defined as the 100% position. For example, it is preferable that the compression ratios of the circular unadjusted region whose center is defined as the 0% position and the outer edge is defined as the 25% position, the first circular adjusted region whose inner edge is defined as the 25% position and the outer edge is defined as the 55% position, and the second circular adjusted region whose inner edge is defined as the 55% position and the outer edge is defined as the 120% position are different from each other.

[0070] By polishing using a polishing pad 26 with such a compressibility distribution, the amount of material to be polished on the wafer W in each radial region can be gradually reduced toward the outer region, allowing for precise control of the shape of the wafer W.

[0071] Alternatively, a circular area with the center at 0% and the outer edge at 25% may be set as the adjustment area. Alternatively, an annular region with the inner edge at 25% and the outer edge at 55% may be left as an unadjusted region. In this case, the removal allowance at the center of the wafer W can be reduced. As described above, by changing the compressibility distribution of the polishing pad 26, it is possible to change the distribution of the removal amount of the wafer W within the plane 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.

[0072] In the polishing pad adjustment condition calculation process of step S63, the polishing pad adjustment condition calculation unit 532 determines adjustment conditions based on the first correlation information acquired in the correlation information acquisition process to change the compression rate distribution of the polishing pad 26 to a compression rate distribution based on the compression rate distribution information acquired in the compression rate distribution information acquisition process.

[0073] In the polishing pad adjustment process of step S64, the polishing pad adjustment control unit 533 controls the position adjustment unit 43 and the platen driving unit 27 of the polishing pad adjustment unit 4 to adjust the polishing pad 26 based on the adjustment conditions obtained in the polishing pad adjustment condition calculation process. By this polishing pad conditioning step, a polishing pad 26 capable of adjusting the shape of the wafer W to the target shape is obtained.

[0074] In the pre-polishing shape information acquisition step of step S65, the information acquisition unit 531 acquires pre-polishing shape information from the input unit 51 or the measuring device.

[0075] In the target shape information acquisition process of step S66, the information acquisition unit 531 acquires target shape information based on the input operation by the operator on the input unit 51. For example, the information acquisition unit 531 acquires information representing ESFQR, ZDD, or GBIR as the target shape information.

[0076] In the target machining allowance calculation process of step S67, the target machining allowance calculation unit 534 calculates the target machining allowance for forming the wafer W into the target shape based on the pre-polishing shape information acquired in the pre-polishing shape information acquisition process and the target shape information acquired in the target shape acquisition process.

[0077] In the oscillation condition calculation process of step S68, the oscillation condition calculation unit 535 calculates the oscillation conditions of the polishing head 21 based on the second correlation information acquired in the correlation information acquisition process and the compression ratio distribution information acquired in the compression ratio distribution information acquisition process.

[0078] In the wafer setting step of step S69, the wafer W obtained in the double-side simultaneous polishing step is set in the single-side polishing apparatus 1.

[0079] In the polishing process of step S70, the polishing control unit 536 controls the head lifting unit 23, head driving unit 24, platen driving unit 27, wafer pressure adjustment unit 28, polishing liquid supply unit 29, and swing driving unit 30 of the polishing unit 2 based on the preset polishing conditions and the swing conditions calculated in the swing condition calculation process, to swing the polishing head 21 while polishing 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.

[0080] In a wafer removal process of step S71, the wafer W is removed from the single-side polishing apparatus 1. The removed wafer W is cleaned in a cleaning process of step S7.

[0081] <Effects of the embodiment> According to the above embodiment, the single-sided polishing apparatus 1 includes an oscillation condition calculation process for determining oscillation conditions for the polishing head 21 that will allow the removal amount in polishing performed using a polishing pad 26 having a radial compression rate distribution to be equal to the target removal amount while oscillating the polishing head 21, and a polishing process for polishing the wafer W using the polishing pad 26 while oscillating the polishing head 21 in a direction parallel to the polishing surface of the polishing pad 26 based on the oscillation conditions. In this way, by performing polishing using the polishing pad 26 having a compressibility distribution in the radial direction, that is, the polishing pad 26 having a different removal amount in the radial direction, it is possible to control the removal amount shape of the wafer W. Furthermore, by swinging the polishing head 21 during polishing, it is possible to adjust the width of the outer periphery of the wafer W to be polished in a predetermined adjustment range, and a wafer W having a desired shape can be obtained.

[0082] The polishing pad 26 is a suede type polishing pad. Therefore, a compressibility distribution can be easily formed in the polishing pad 26.

[0083] 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 efficiently 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 may worsen LPD (Light Point Defect), but by using the brush 42, it is possible to suppress the deterioration of LPD.

[0084] 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 control unit 533. 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.

[0085] 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 533, 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.

[0086] [Variations] 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.

[0087] For example, a configuration has been exemplified in which the target removal amount is determined based on pre-polishing shape information and target shape information, but if multiple wafers W with the same pre-polishing shape are to be polished and these multiple target shapes are the same, the target removal amount may be set to a constant value and the pre-polishing shape acquisition process, target shape acquisition process, and target removal amount calculation process may not be performed.

[0088] As a method for forming an annular region on the polishing pad 26 with a different compression rate from other regions, a method in which the brush 42 is fixed and the polishing pad 26 is rotated has been exemplified, but the brush 42 may also be moved in a circular motion without rotating the polishing pad 26 or while rotating the polishing pad 26.

[0089] 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, but the height position of the polishing pad 26 may also be changed while the height position of the brush 42 is fixed or changed. [Example]

[0090] Next, examples of the present invention will be described. Note that the present invention is not limited to the examples. There is no.

[0091] Example 1: Relationship between the amount of brush pressure against the polishing pad (compressibility distribution of the polishing pad), the swing width of the polishing head, and the shape of the wafer after polishing First, the single-side polishing apparatus 1 of the above embodiment was prepared. Also, a plurality of suede-type polishing pads 26 were prepared. Also, a plurality of wafers W having the same pre-polishing shape and a diameter of 300 mm were prepared.

[0092] 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 the 99.7% position when the polishing head 21 was not oscillating, and the position of the outer edge was 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.

[0093] Then, adjustment was performed for 30 seconds by rotating surface plate 25. As a result, polishing pad 26 of Example 1-1 was obtained, which had a compression ratio distribution in which the unadjusted region 26A and the adjusted region 26B had different compression ratio distributions.

[0094] In addition, another polishing pad 26 was adjusted under the same conditions as the polishing pad 26 of Example 1-1, except that the pressing amount of the brush 42 was set to 0.8 mm, to obtain the polishing pad 26 of Example 1-2 having a compressibility distribution. In addition, another polishing pad 26 was adjusted under the same conditions as the polishing pad 26 of Example 1-1, except that the pressing amount of the brush 42 was set to 1.1 mm, to obtain the polishing pad 26 of Example 1-3 having a compressibility distribution. In addition, another polishing pad 26 that had not been conditioned with the brush 42 was prepared as the polishing pad 26 of Comparative Example 1 that did not have a compressibility distribution.

[0095] As described above, the greater the pressing amount of brush 42 against polishing pad 26, the greater the compression ratio of polishing pad 26. Therefore, the compression ratio of adjustment region 26B in polishing pads 26 of Examples 1-1 to 1-3 is the greatest in polishing pad 26 of Example 1-3 and the smallest in polishing pad 26 of Example 1-1. Furthermore, the compression ratio of the unadjusted region 26A in the polishing pads 26 of Examples 1-1 to 1-3 is the same as the compression ratio of the entire polishing pad 26 of Comparative Example 1. Moreover, the overall thickness of the polishing pad 26 in each of Examples 1-1 to 1-3 and Comparative Example 1 is approximately the same.

[0096] Then, the oscillation width L of the polishing head 21 was set to 0 mm, 20 mm, 40 mm or 60 mm, respectively, and different wafers W were polished using the polishing pad 26 of Example 1-1, thereby obtaining multiple wafers W of Example 1-1 polished with different oscillation widths L. In addition, another wafer W was polished under the same conditions as the wafer W of Example 1-1, except that the polishing pad 26 of Example 1-2 was used, and a wafer W of Example 1-2 was obtained that was polished with a different oscillation width L. In addition, another wafer W was polished under the same conditions as the wafer W of Example 1-1, except that the polishing pad 26 of Example 1-3 was used, and a wafer W of Example 1-3 was obtained, which was polished with a different oscillation width L. In addition, another wafer W was polished under the same conditions as the wafer W of Example 1-1, except that the polishing pad 26 of Comparative Example 1 was used, and a wafer W of Comparative Example 1 was obtained that was polished with a different oscillation width L.

[0097] The ESFQR was measured for the wafers W of Examples 1-1 to 1-3 and Comparative Example 1. The measurement results are shown in FIG.

[0098] From the measurement results for the wafer W of Comparative Example 1, it was confirmed that when the wafer W is polished using a polishing pad 26 that does not have a compressibility distribution, the value of ESFQR is almost the same regardless of the oscillation width L of the polishing head 21, that is, the flatness of the outer periphery of the wafer W remains almost unchanged. On the other hand, from the measurement results for the wafers W in Examples 1-1 to 1-3, it was confirmed that when the wafer W is polished using a polishing pad 26 having a compressibility distribution, the larger the oscillation width L of the polishing head 21, the smaller the ESFQR value, i.e., the higher the flatness of the outer periphery of the wafer W. Furthermore, from the measurement results for the wafers W in Examples 1-1 to 1-3, it was confirmed that when polishing the wafer W using a polishing pad 26 having a compression rate distribution, if the oscillation width L of the polishing head 21 is the same, the higher the compression rate of the adjustment region 26B, the smaller the ESFQR value, i.e., the higher the flatness of the outer periphery of the wafer W.

[0099] From the above, it was confirmed that when polishing the wafer W, not only is a polishing pad 26 having a compressibility distribution used, but also the polishing head 21 is oscillated, thereby increasing the flatness of the outer periphery of the wafer W. It was also confirmed that by controlling the compressibility distribution of the polishing pad 26 and the oscillation width L of the polishing head 21, a wafer W having a desired shape can be obtained.

[0100] Example 2: Relationship between the swing width of the polishing head and the shape of the wafer after polishing when polishing using a polishing pad with a compressibility distribution First, the single-side polishing apparatus 1 of the above embodiment was prepared. Two suede-type polishing pads 26 having the following characteristics were also prepared. Compression rate of polishing pad 26: 26.6%

[0101] The single-side polishing device 1 was equipped with the polishing pad 26 and a nylon brush 42 with bristles of 5 mm length. 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 the 99.7% position when the polishing head 21 was not oscillating, and the position of the outer edge was 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.

[0102] Then, adjustment was performed for 30 seconds by rotating the surface plate 25. As a result, polishing pad 26 of Example 2 was obtained, which had a compression rate distribution in which the compression rate in the region from the center to the 99% position was 26.6%, and the compression rate in the region from the 99% position to the 120% position was 27.8%.

[0103] Additionally, multiple wafers W with a diameter of 300 mm were prepared, each having the pre-polishing shape shown in Fig. 8. The horizontal axis of the graph shown in Fig. 8 represents the distance from the center of the wafer W, and the vertical axis represents the amount of displacement from a reference plane (shown as "first reference plane" in Fig. 8) calculated by the least squares method from the thickness distribution within the site.

[0104] Then, without swinging the polishing head 21, the wafer W was polished using the polishing pad 26 of Example 2, to obtain the wafer W of Comparative Example 2. Also, another wafer W was polished under the same conditions as those for the wafer W of Comparative Example 2, except that the swing width L of the polishing head 21 was set to 20 mm, to obtain a wafer W of Example 2-1. In addition, another wafer W was polished under the same conditions as those for the wafer W of Comparative Example 2, except that the swing width L of the polishing head 21 was set to 40 mm, to obtain a wafer W of Example 2-2. Also, another wafer W was polished under the same conditions as those for the wafer W of Comparative Example 2, except that the swing width L of the polishing head 21 was set to 60 mm, to obtain a wafer W of Example 2-3.

[0105] Then, the polishing allowance shapes of the wafers W of Comparative Example 2 and Examples 2-1 to 2-3 were measured. The measurement results are shown in Fig. 9. The horizontal axis of the graph shown in Fig. 9 represents the distance from the center of the wafer W, and the vertical axis represents the amount of displacement from a reference plane (shown as a "second reference plane" in Fig. 9) found within the site by the least squares method in a calculated differential profile of the thickness of the wafer W before and after polishing. Furthermore, the ESFQR_max_1mm and GBIR of the wafers W of Comparative Example 2 and Examples 2-1 to 2-3 were measured. The measurement results are shown in Table 1. 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.

[0106] [Table 1]

[0107] When comparing the shape of the wafer W shown in Figure 9 and the measurement results of ESFQR_max_1mm for the wafers W of Comparative Example 2 and Examples 2-1 to 2-3 polished using a polishing pad 26 having a compressibility distribution, it was confirmed that the flatness of the outer periphery of the wafers W of Examples 2-1 to 2-3 was higher than that of the outer periphery of the wafer W of Comparative Example 2. Furthermore, when ESFQR_max_1mm was compared for the wafers W of Examples 2-1 to 2-3, it was confirmed that the value for the wafer W of Example 2-3 was the smallest and the value for the wafer W of Example 2-1 was the largest. In other words, it was confirmed that the flatness of the outer periphery of the wafer W of Example 2-3 was the highest and the flatness of the outer periphery of the wafer W of Example 2-1 was the lowest.

[0108] From the above, it was confirmed that when polishing a wafer W using a polishing pad 26 having a compressibility distribution, the larger the oscillation width L of the polishing head 21, the higher the flatness of the outer periphery of the wafer W. In particular, it was confirmed that for a wafer W having a pre-polishing shape as shown in Fig. 8, a wafer W having a high flatness of the outer periphery can be obtained by selecting the compressibility distribution and oscillation width as shown in Example 2-3 in Fig. 9.

[0109] Furthermore, when comparing the GBIR measurement results for the wafers W of Examples 2-1 to 2-3, it was confirmed that the value for the wafer W of Example 2-3 was the smallest and the value for the wafer W of Example 2-1 was the largest. In particular, it was confirmed that the GBIR values ​​for the wafers W of Examples 2-2 and 2-3 were smaller than the GBIR value for the wafer W of Comparative Example 2.

[0110] From the above, it has been confirmed that when polishing a wafer W using a polishing pad 26 having a compressibility distribution, a wafer W with high flatness can be obtained by selecting a compressibility distribution and oscillation width that allows for a removal amount that matches the pre-polishing shape of the wafer W.

[0111] Example 3: Relationship between the presence or absence of compressibility distribution in the polishing pad during polishing with an oscillating polishing head and the shape of the wafer after polishing Of the polishing pads 26 prepared in Example 2, the polishing pad 26 that had not been conditioned with the brush 42 was prepared as the polishing pad 26 of Comparative Example 3, which did not have a compressibility distribution. Then, the wafer W was polished under the same conditions as those for the wafer W in Example 2-3, except that the polishing pad 26 in Comparative Example 3 was used, thereby obtaining the wafer W in Comparative Example 3.

[0112] The ESFQR_max_1mm and GBIR of the wafers W of Comparative Example 3 and Example 2-3 were measured. The measurement results are shown in Table 2.

[0113] [Table 2]

[0114] When the measurement results of ESFQR_max_1mm and GBIR for the wafers W of Comparative Example 3 and Example 2-3 were compared, it was confirmed that the values ​​of the wafer W of Example 2-3 were smaller than the values ​​of the wafer W of Comparative Example 3.

[0115] From the above, it was confirmed that for a wafer W having a pre-polishing shape as shown in Figure 8, the flatness of the outer periphery and the entire wafer W can be improved by providing a compression rate distribution to the polishing pad 26 and oscillating the polishing head 21. [Explanation of symbols]

[0116] 1...single-sided polishing apparatus, 5...controller, 21...polishing head, 24...head drive unit (rotation drive unit), 26...polishing pad, 27...plate drive unit (rotation drive unit), 30...oscillation drive unit, 42...brush, 535...oscillation condition calculation unit, 536...polishing control unit, W...wafer

Claims

1. A method for polishing a single side of a wafer, comprising: pressing a 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 to polish the wafer, a polishing pad adjusting step in which a process of adjusting the polishing pad to have a compressibility distribution in the radial direction is performed by rotating the polishing pad and pressing a brush against the polishing pad to form an annular region on the polishing pad having a compressibility different from that of other regions; a swing condition calculation step of determining swing conditions for the polishing head based on a removal rate during polishing performed using the polishing pad having the compressibility distribution while swinging the polishing head; a polishing step of polishing the wafer using the polishing pad while oscillating the polishing head based on the oscillation conditions.

2. 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 when the polishing pad is not oscillating is the 100% position, and the compression rate is higher than that of the inner region.

3. 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.

4. 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 swing drive unit that swings the polishing head in a direction parallel to the polishing surface of the polishing pad; a control device; The control device a polishing pad adjustment control unit that controls the polishing pad adjustment unit to adjust the polishing pad so that it has a compressibility distribution in the radial direction, by pressing the brush against the polishing pad while rotating the polishing pad, thereby forming an annular region having a compressibility different from that of other regions; a swing condition calculation unit that calculates swing conditions for the polishing head based on a removal rate during polishing performed using the polishing pad having the compressibility distribution while swinging the polishing head; a polishing control unit that controls the rotation drive unit and the swing drive unit to swing the polishing head based on the swing conditions and polish the wafer using the polishing pad.

Images