Polishing pad and wafer polishing method

Abstract

To provide a polishing pad and a wafer polishing method which can suppress occurrence of scratch of a wafer after polishing, and can achieve both high accuracy and high workability.SOLUTION: A polishing pad can be taken as a first polishing pad 7 and a second polishing pad 9, in a double-sided polishing type wafer polishing device 10. A wafer W is composed of SiC so that one of a first surface W1 and a second surface W2 is Si face, and the other of the first surface W1 and the second surface W2 is C face. The polishing pad contains a binder resin, and includes a base material 19 formed with a plurality of pores 21 and 23, and polishing particles 25a and 25b held in the base material 19 or the pores 21 and 23. The binder resin is a sulfonic resin, and the polishing particles 25a and 25b are composed of silica, and have durometer hardness (D) of 30 to 52, and density of 0.60 to 0.90 g / cm3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing pad and a method for polishing a wafer. [Background technology]

[0002] Patent Document 1 discloses a method for simultaneously polishing both sides of a SiC wafer. This wafer polishing method is used in a double-side polishing wafer polishing apparatus. This wafer polishing apparatus moves a first side of the wafer and a first polishing pad relative to each other under a predetermined surface pressure to polish the first side with the first polishing pad, and moves a second side of the wafer (the backside of the first side) relative to the second polishing pad to polish the second side with the first polishing pad. During this process, a polishing liquid containing no abrasive particles is interposed between the first side of the wafer and the first polishing pad and between the second side of the wafer and the second polishing pad.

[0003] More specifically, the wafer polishing apparatus comprises a first platen, a second platen, and a carrier. The first platen has a first polishing pad extending in a direction perpendicular to its axis and is rotated about its axis. The second platen extends in a direction perpendicular to the axis and has a second polishing pad facing the first polishing pad and is rotated about its axis. The carrier extends in a direction perpendicular to the axis and has a fixing portion facing the first polishing pad and the second polishing pad, and is rotated relative to the first platen and the second platen.

[0004] The first polishing pad and the second polishing pad are abrasive grain-containing polishing pads also known as LHA (Loosely Held Abrasive) pads, which contain a binder resin, a base material with multiple pores formed therein, and abrasive particles held within the base material or the pores.

[0005] In this wafer polishing method, when the first surface of a wafer is a Si surface and the second surface is a C surface, the polishing rate of the first polishing pad is set lower than that of the second polishing pad because the polishing rate of the second surface is greater than that of the first surface, which makes it possible to suppress scratches on the wafer after polishing and achieves high workability and precision. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7433170 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the conventional wafer polishing method described above, it is necessary to use a first polishing pad and a second polishing pad with different polishing rates, which results in insufficient workability.

[0008] The present invention has been made in consideration of the above-mentioned conventional situation, and aims to solve the problem of providing a polishing pad and a wafer polishing method that can suppress the occurrence of scratches on the wafer after polishing, and that can achieve high precision and greater workability. [Means for solving the problem]

[0009] The polishing pad of the present invention is used in a double-side polishing type wafer polishing apparatus that polishes a first surface of a wafer with the first polishing pad by relatively moving the first surface of the wafer and the first polishing pad under a predetermined surface pressure, and polishes a second surface of the wafer, which is the back side of the first surface, with the first polishing pad by relatively moving the second polishing pad and the second polishing pad, and can be the first polishing pad and the second polishing pad, The wafer polishing apparatus includes a first polishing pad extending in a direction perpendicular to an axis of the wafer polishing apparatus, the first polishing pad being rotated around the axis of the wafer polishing apparatus; a second platen extending in a direction perpendicular to the axis, having the second polishing pad facing the first polishing pad, and rotated around the axis; a carrier extending in a direction perpendicular to the axis, facing the first polishing pad and having a fixing portion facing the second polishing pad, the carrier being rotated relatively to the first platen and the second platen; the wafer is fixed to the fixing portion such that the first surface faces the first polishing pad and the second surface faces the second polishing pad; the wafer is made of SiC, one of the first surface and the second surface being a Si surface, and the other of the first surface and the second surface being a C surface; a base material containing a binder resin and having a plurality of pores formed therein; and abrasive particles held in the base material or the pores; the binder resin is a sulfone-based resin, the abrasive particles are made of silica; Durometer hardness (D) is 30 to 52, Density: 0.60~0.90g / cm 3 It is characterized in that:

[0010] The wafer polishing method of the present invention also includes a first polishing pad extending in a direction perpendicular to an axis and rotated around the axis; a second polishing pad extending in a direction perpendicular to the axis and facing the first polishing pad, the second polishing pad being rotated around the axis; a wafer polishing apparatus including a carrier that extends in a direction perpendicular to the axis, has a fixing portion facing the first polishing pad and facing the second polishing pad, and is rotated relatively to the first platen and the second platen; The wafer is fixed to the fixing portion so that a first surface faces the first polishing pad and a second surface, which is the back side of the first surface, faces the second polishing pad; A wafer polishing method comprising: polishing the first surface by relatively moving the first surface and the first polishing pad under a predetermined surface pressure; and polishing the second surface by relatively moving the second surface and the second polishing pad, the wafer is made of SiC, one of the first surface and the second surface being a Si surface, and the other of the first surface and the second surface being a C surface; the first polishing pad and the second polishing pad are the same type of polishing pads, each of which includes a base material containing a binder resin and having a plurality of pores formed therein, and abrasive particles held in the base material or the pores; the binder resin is a sulfone-based resin, the abrasive particles are made of silica; Durometer hardness (D) is 30 to 52, Density: 0.60~0.90g / cm 3 It is characterized in that:

[0011] According to the results of the inventors' tests, if the above-mentioned polishing pads are used for the first and second polishing pads, it is possible to suppress the occurrence of scratches on the wafer after polishing and achieve high precision. Therefore, the wafer polishing method of the present invention using the polishing pad of the present invention eliminates the need to use first and second polishing pads with different polishing rates, and achieves higher workability. [Effects of the Invention]

[0012] The polishing pad and wafer polishing method of the present invention can suppress the occurrence of scratches on the wafer after polishing, and can also achieve high precision and improved workability. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of a wafer polishing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is an SEM photograph of the polishing pad of Example 1 at 500x magnification. [Figure 3] FIG. 3 is an SEM photograph of the first region of the polishing pad of Example 1, magnified 2000 times. [Figure 4] FIG. 4 is an SEM photograph of the second region of the polishing pad of Example 1 at 400 magnifications. [Figure 5] FIG. 5 is an SEM photograph of the second region of the polishing pad of Example 1 at 2000 magnifications. [Figure 6] FIG. 6 is a schematic enlarged cross-sectional view of the polishing pads of Examples 1 to 7. DETAILED DESCRIPTION OF THE INVENTION

[0014] A sulfone-based resin is used as the binder resin. The LHA pad can use, as its binder resin, polyether, rigid polyurethane foam, epoxy resin, polyethersulfone resin, as well as fluorine-based synthetic resins such as polyvinyl fluoride, vinyl fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyethylene resin, polymethyl methacrylate, etc. However, according to the results of tests conducted by the inventors, sulfone-based resins are preferred for the first polishing pad and the second polishing pad because of their excellent chemical resistance and abrasion resistance.

[0015] The sulfone resin may be polyethersulfone (PES), polysulfone (PSU), polyphenylsulfone (PPSU), etc. The inventors confirmed the effect of the present invention using PES.

[0016] Silica is used as the abrasive particles. The LHA pad can use silica, diamond, cubic boron nitride, boron carbide, silicon carbide, alumina, zirconia, titania, ceria, manganese oxide, barium carbonate, chromium oxide, iron oxide, etc., but according to the inventors' test results, silica is preferred for the first and second polishing pads because it has a low Knoop hardness, making it less susceptible to scratches, and has excellent polishing properties.

[0017] According to the test results of the inventors, the polishing pads used for the first polishing pad and the second polishing pad should have a durometer hardness (D) of 30 to 52 and a density of 0.60 to 0.90 g / cm 3 It is preferable to set the following.

[0018] According to the results of the inventors' tests, it is preferable that the binder resin is 17.6 to 26.2% by volume, the abrasive particles are 16.3 to 24.6% by volume, and the pores are 49.2 to 66.1% by volume.

[0019] It is particularly preferable that the pores consist of micropores forming a three-dimensional network structure and large pores that are larger in volume than the micropores and communicate with numerous other micropores. In this case, the polishing surface of the polishing pad has a first region without large pores and a second region with large pores. In the first region, the binder resin forms a network structure, and abrasive particles are contained within the pores. Furthermore, in the first region, the binder resin and abrasive particles are densely packed. Therefore, high-efficiency polishing can be expected in the first region. On the other hand, in the second region, numerous pores exist on the surface of the large pores, and abrasive particles are discharged from each pore. Furthermore, the polishing liquid accumulates in the large pores. The abrasive particles discharged from the micropores into the large pores have a degree of freedom in the large pores during polishing. Furthermore, the large pores reduce processing resistance during double-sided polishing of wafers, resulting in high-quality polished wafers and reducing wafer crushing during double-sided polishing.

[0020] According to the test results of the inventors, it is preferable that the fine pores are 44.1 to 51.6% by volume and the large pores are 2.7 to 15.7% by volume.

[0021] In wafer polishing methods, a polishing liquid is placed between the wafer and the first polishing pad and between the wafer and the second polishing pad, but the wafer polishing method of the present invention can use a polishing liquid that does not contain abrasive particles, which improves the cleanability of the wafer after polishing and is expected to reduce waste liquid costs.

[0022] Examples and Comparative Examples First, a double-side polishing type wafer polishing apparatus (9B double-side polisher) 10 shown in Figure 1 was prepared. This wafer polishing apparatus 10 includes a first platen 1, a second platen 3, and a carrier 5. The wafer polishing apparatus 10 is capable of polishing the first side W1 and the second side W2 of the wafer W simultaneously.

[0023] The first base plate 1 is annular, and has a first annular polishing pad 7 on its underside. The second base plate 3 is also annular and matches the first base plate 1, and has a second annular polishing pad 9 on its upper surface. The first base plate 1 is provided with a first rotation shaft (not shown), and the second base plate 3 is provided with a second rotation shaft (not shown). These extend in the direction of axis X1 and are rotated around axis X1 at a predetermined speed by a drive unit 11. The first base plate 1 and the second base plate 3 can move toward and away from each other. The first polishing pad 7 and the second polishing pad 9 extend horizontally in a direction perpendicular to X1 and face each other.

[0024] The carrier 5 is disposed between the first polishing pad 7 and the second polishing pad 9. A driving force transmission mechanism (not shown) is provided in the carrier 5, and the driving force transmission mechanism causes the carrier 5 to rotate relatively to the first platen 1 and the second platen 3 at a predetermined speed around an axis X2 parallel to the axis X1.

[0025] The fixing portion 5a of the carrier 5 extends horizontally in a direction perpendicular to the axis X2, and faces the first polishing pad 7 and the second polishing pad 9. A wafer W is fixed to the fixing portion 5a. The carrier 5 has multiple fixing portions 5a, and multiple wafers W can be mounted on the fixing portion 5a.

[0026] Each wafer W is made of SiC. The Si surface of the SiC is the first surface W1, and the C surface of the SiC is the second surface W2. The first surface W1 of the wafer W faces the first polishing pad 7, and the second surface W2 faces the second polishing pad 9.

[0027] An annular tray 13 is placed on the first base plate 1. The tray 13 can rotate around the axis X1 together with the first base plate 1. A plurality of nozzles 15 are provided on the tray 13, and each nozzle 15 is connected to a tank (not shown). Therefore, the polishing liquid 17 in the tank is supplied from each noble 15 into the tray 13. A plurality of supply holes 13a are formed in the tray 13, and each supply hole 13a is connected to a tube 19 extending above the first base plate 1. A communication hole 1a and an opening 7a are formed through the first base plate 1 and the first polishing pad 7, and the polishing liquid 17 in the tray 13 can be supplied between the first polishing pad 7 and the second polishing pad 9 through each supply hole 13a, each tube 19, each communication hole 1a, and each opening 7a.

[0028] When the wafer W is fixed to the fixing portion 5a and the wafer polishing apparatus 10 is operated, the first platen 1 and the second platen 3 approach each other, and each wafer W fixed to the fixing portion 5a of the carrier 5 and the first and second polishing pads 7 and 9 are pressed to a predetermined surface pressure, and the drive unit 11 is driven to rotate the first platen 1, the second platen 3, and the carrier 5. As a result, the first surface W1 of the wafer W and the first polishing pad 7 move relative to each other at a predetermined speed to polish the first surface W1, and the second surface W2 of the wafer W and the second polishing pad 9 move relative to each other at a predetermined speed to polish the second surface W2. Then, after a predetermined time has elapsed, polishing of the first surface W1 and polishing of the second surface W2 can be completed simultaneously.

[0029] Meanwhile, the following binder resin, abrasive particles, solvent, pore-forming agent, and additives were prepared. (binder resin) Polyethersulfone (PES) (abrasive particles) Silica (SiO2) (average particle size: 200 nm) (solvent) N-methyl-2-pyrrolidone (NMP) (pore-forming agent) Granulated sugar (average particle size 200 μm) (additives) glycerin

[0030] The binder resin, abrasive particles, solvent, pore-forming agent, and additive components were mixed in the blending ratios (volume %) shown in Table 1 to obtain pastes. Each of the obtained pastes was used to obtain sheet-shaped compacts using a T-die. The solvent was removed from each compact, and the binder resin was solidified.

[0031] [Table 1]

[0032] The polishing surface of the obtained intermediate was dressed to produce polishing pads of Examples 1 to 7 and Comparative Example 1. A 500x SEM photograph of the polishing pad of Example 1 is shown in Figure 2. From Figure 2, it can be seen that the polishing pads of Examples 1 to 7 contain a base material containing a binder resin and having multiple pores formed therein, and abrasive particles held within the base material or the pores. It can also be seen that the pores consist of fine pores forming a three-dimensional network structure and large pores that are larger in volume than the fine pores and communicate with the fine pores. The fine pores are formed by a solvent, and the large pores are formed by granulated sugar. Glycerin is used to adjust the solubility of the binder resin in the solvent.

[0033] The physical properties of the polishing pads of Examples 1 to 7 and Comparative Example 1 were measured using durometer hardness (D), density (g / cm 3 The results are shown in Table 2.

[0034] [Table 2]

[0035] The breakdown of the pore content, i.e., the volume percent of fine pores and the volume percent of large pores, was also measured. The results are shown in Table 3.

[0036] [Table 3]

[0037] 3 shows a 2000x SEM photograph of the first region, where no large pores exist, in the polishing pad of Example 1. Table 4 shows the density additions (volume %) of the binder resin and the density additions (volume %) of the abrasive particles in the first region of the polishing pads of Examples 1 to 7.

[0038] [Table 4]

[0039] Figure 3 shows that in the first region, the binder resin forms a network structure, with abrasive particles contained within the pores. Table 4 also shows that the binder resin and abrasive particles are densely packed together to fill the volume of large pores with a diameter of approximately 200 μm.

[0040] Meanwhile, an SEM photograph of the second region at 400x magnification is shown in Figure 4, and an SEM photograph of the second region at 2000x magnification is shown in Figure 5. Figures 4 and 5 show that large pores have formed in the second region, and that there are many small pores with a diameter of about 4 μm on the surface of the large pores, and that abrasive particles are discharged from the pores.

[0041] (test) The polishing pads of Examples 1 to 7 or Comparative Example 1 were used as the first polishing pad 7 and second polishing pad 9 of the wafer polishing apparatus 10, and a polishing test was carried out under the following conditions. Polishing pad dimensions: Donut shape with a diameter of 660 mm (punched out at a diameter of 200 mm from the center) Wafer W: SiC (diameter 4 inches) Polishing solution: Permanganic acid aqueous solution (does not contain abrasive particles)

[0042] The polishing rate (μm / h), surface roughness Ra (nm) of the Si surface, surface roughness Ra (nm) of the C surface, machining resistance (A) converted to current value, and TTV (μm) were measured. Note that TTV is an index of thickness variation of the wafer W. A high TTV indicates large thickness variation, and a low TTV indicates small thickness variation. A low TTV is excellent.

[0043] The cleaning properties were evaluated by observation under an electron microscope, with 0 particles in a 5 μm x 5 μm area being rated as ◎, 5 or fewer particles being ◯, 5 to 10 particles being △, and 10 or more particles being ×.

[0044] The overall evaluation was performed according to the following criteria. ◎ was evaluated as follows: a polishing rate of 1.5 μm / h or more, a surface roughness Ra of the Si surface of 0.15 nm or less, a surface roughness Ra of the C surface of 0.25 nm or less, a machining resistance of 0.40 A or less, a TTV of 1.0 μm or less, and cleanability of ◎. 〇 was evaluated as follows: a polishing rate of 1.0 μm / h or more, a surface roughness Ra of the Si surface of 0.20 nm or less, a surface roughness Ra of the C surface of 0.30 nm or less, a machining resistance of 0.40 A or less, a TTV of 1.5 μm or less, and cleanability of ◎ or ○. △ was evaluated as follows: a polishing rate of 1.0 μm / h or less, a surface roughness Ra of the Si surface of 0.20 nm or more, a surface roughness Ra of the C surface of 0.30 nm or more, a machining resistance of 0.40 A or more, a TTV of 1.5 μm or more, and cleanability of ○ or △. The results were evaluated as × when the polishing rate was 1.0 μm / h or less, the surface roughness Ra of the Si surface was 0.20 nm or more, the surface roughness Ra of the C surface was 0.30 nm or more, the processing resistance was 0.40 A or more, the TTV was 2.0 μm or more, and the cleanability was △ or ×. The results are shown in Table 5.

[0045] [Table 5]

[0046] From Table 5, it can be seen that if the polishing pads of Examples 1 to 7 are used for the first polishing pad 7 and the second polishing pad 9, it is possible to suppress the occurrence of scratches on the wafer W after polishing and achieve high accuracy, even if the wafer W is made of SiC, with the first surface W1 being an Si surface and the second surface W2 being a C surface. Therefore, it can also be seen that the wafer polishing methods of Examples 1 to 7 using the polishing pads of Examples 1 to 7 eliminate the need to use first and second polishing pads with different polishing rates, and achieve higher workability.

[0047] 6, in the polishing test, the first surface W1 or the second surface W2 of the wafer W moves relative to the first polishing pad 7 or the second polishing pad 9 while being pressed by a predetermined force F in the presence of a polishing liquid 17. During this time, the inventors speculate that the following action occurs in the polishing pads of Examples 1 to 6, since the pores are composed of fine pores 21 and large pores 23.

[0048] That is, the base material 19 has a three-dimensional network structure formed by the pores 21, and the pores 21 contain abrasive particles 25a that do not contribute to polishing. The large pores 23 have a larger volume than the pores 21 and are connected to the countless pores 21. The polishing liquid 17 accumulates in the large pores 23. The abrasive particles 25a that do not contribute to polishing within the countless pores 21 are discharged from each pore 21 into the large pores 23. The abrasive particles 25b discharged into the large pores 23 contribute to polishing the wafer W on the polishing surface 20 while retaining their freedom. Furthermore, the binder resin and abrasive particles are densely present in the first region of the polishing surface 20. In this way, polishing is performed with high precision and efficiency.

[0049] Although the present invention has been described above with reference to the examples, it goes without saying that the present invention is not limited to the above examples and can be modified and applied as appropriate within the scope of the invention.

[0050] For example, in the above-mentioned wafer polishing apparatus 10, the first axis X1 of the first and second platens 1 and 3 is parallel to the second axis X2 of the carrier 5, but in the wafer polishing apparatus used in the polishing pad and wafer polishing method of the present invention, the axis of the first and second platens 1 and 3 may coincide with the axis of the carrier 5. [Industrial Applicability]

[0051] The present invention can be used in semiconductor device manufacturing equipment and the like. [Explanation of symbols]

[0052] W...wafer W1…First page 7...First polishing pad W2...Second side 9...Second polishing pad 10...Wafer polishing device X1, X2...Axis center (X1...1st axis center, X2...2nd axis center) 1...First base plate 3...Second base plate 5a…Fixed part 5...Carrier 19...Base material 21, 23... Pores (21... pores, 23... large pores) 25a, 25b...abrasive particles

Claims

1. A polishing pad that can be the first polishing pad and the second polishing pad is used in a double-side polishing type wafer polishing apparatus that polishes a first surface of a wafer with the first polishing pad by relatively moving the first surface of the wafer and a first polishing pad under a predetermined surface pressure, and polishes a second surface of the wafer, which is the back side of the first surface, with the first polishing pad by relatively moving the second polishing pad, The wafer polishing apparatus includes a first polishing pad extending in a direction perpendicular to an axis of the wafer polishing apparatus, the first polishing pad being rotated around the axis of the wafer polishing apparatus; a second platen extending in a direction perpendicular to the axis, having the second polishing pad facing the first polishing pad, and being rotated around the axis; a carrier extending in a direction perpendicular to the axis, facing the first polishing pad and having a fixing portion facing the second polishing pad, the carrier being rotated relatively to the first platen and the second platen; the wafer is fixed to the fixing portion such that the first surface faces the first polishing pad and the second surface faces the second polishing pad; the wafer is made of SiC, one of the first surface and the second surface being a Si-face and the other of the first surface and the second surface being a C-face; a base material containing a binder resin and having a plurality of pores formed therein; and abrasive particles held in the base material or the pores; the binder resin is a sulfone-based resin, the abrasive particles are made of silica; Durometer hardness (D) is 30 to 52, Density is 0.60 to 0.90 g / cm 3 A polishing pad characterized by:

2. 2. The polishing pad according to claim 1, wherein the binder resin is polyethersulfone.

3. The binder resin is 17.6 to 26.2% by volume, The abrasive particles are 16.3 to 24.6 volume percent, 3. The polishing pad according to claim 2, wherein the pores are 49.2 to 66.1% by volume.

4. 4. The polishing pad according to claim 1, wherein the pores are composed of pores forming a three-dimensional network structure and large pores having a larger volume than the pores and communicating with an innumerable number of the pores.

5. The pores are 44.1 to 51.6% by volume, 5. The polishing pad according to claim 4, wherein the large pores are 2.7 to 15.7% by volume.

6. a first polishing pad extending in a direction perpendicular to the axis and a first surface plate rotated around the axis; a second polishing pad extending in a direction perpendicular to the axis and facing the first polishing pad, the second polishing pad being rotated around the axis; a wafer polishing apparatus including a carrier that extends in a direction perpendicular to the axis, has a fixing portion facing the first polishing pad and facing the second polishing pad, and is rotated relatively to the first platen and the second platen; The wafer is fixed to the fixing portion so that a first surface faces the first polishing pad and a second surface, which is the back side of the first surface, faces the second polishing pad; A wafer polishing method comprising: polishing the first surface by relatively moving the first surface and the first polishing pad under a predetermined surface pressure; and polishing the second surface by relatively moving the second surface and the second polishing pad, the wafer is made of SiC, one of the first surface and the second surface being a Si-face and the other of the first surface and the second surface being a C-face; the first polishing pad and the second polishing pad are the same type of polishing pads, each of which includes a base material containing a binder resin and having a plurality of pores formed therein, and abrasive particles held in the base material or the pores; the binder resin is a sulfone-based resin, the abrasive particles are made of silica; Durometer hardness (D) is 30 to 52, Density is 0.60 to 0.90 g / cm 3 A wafer polishing method comprising:

7. a polishing liquid is interposed between the wafer and the first polishing pad and between the wafer and the second polishing pad; 7. The wafer polishing method according to claim 6, wherein the polishing liquid does not contain abrasive particles.

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