Resin porous body, compound semiconductor polishing pad, and method for manufacturing the resin porous body

Abstract

To provide a method for manufacturing a resin porous body having fine pores.SOLUTION: The method for manufacturing the resin porous body comprises: a molten body generation unit P1 of obtaining a molten body by melting disaccharides of a base material resin, lactose and the like high in oxidant resistance and abrasion resistance in an organic solvent; a molding step P2 of obtaining a thin plate-like molding by molding the molten body into a thin plate-like shape; a deposition step P3 of leaving the thin plate-like molding in cold water to finely deposit a solid body of the disaccharides in the thin plate-like molding; a replacement step P4 of leaving the thin plate-like molding passed through the deposition step P3 in hot water to replace the solid body of the disaccharides with water; and a drying step P5 of drying the thin plate-like molding until there is no more moisture. The resin porous body is made of a base material resin highly resistant to a strong oxidant, and fine pores are generated in the base material resin. Thus, in polishing of a hard polishing wafer using a polishing pad 18, scratch damaging is limited, and a polishing rate PR and surface roughness Sa can be maintained for a long time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a porous resin body having high chemical resistance and fine pores, and to a compound semiconductor polishing pad using the porous resin body. [Background technology]

[0002] There is a demand for porous resin bodies with high chemical resistance and fine pores for use in compound semiconductor polishing pads for polishing compound semiconductor wafers, water-adhesive pads for fixing compound semiconductor wafers on polishing discs, synthetic leather, vibration-proof sheets, sound-absorbing materials, water-absorbing and water-retaining bodies, separators and separation membranes for fuel cells, etc.

[0003] For example, semiconductor wafers such as SiC wafers, GaN wafers, Si wafers, and Si oxide wafers are known to be difficult to polish. A polishing method based on the CMP method has been proposed for polishing such semiconductor wafers, in which a resin polishing pad that mechanically promotes polishing and a polishing solution that chemically promotes polishing are used. For example, Patent Document 1 describes such a polishing method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-057368 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the hard-to-polish wafer is polished on a polishing pad using a polishing solution containing a strong permanganate-based oxidizing agent such as potassium permanganate, if the resin constituting the polishing pad is a resin with low resistance to the oxidizing agent, such as a foamed polyurethane resin, the resin deteriorates, and the surface roughness and shape of the polishing material tend to deteriorate, resulting in a short service life of the polishing pad.In contrast, if a polishing pad with a high proportion of polyurethane resin in the polishing pad and fewer pores is used, the service life is extended, but there is a problem that scratches are easily formed due to the small number of pores.

[0006] The present invention has been made against the background of the above circumstances, and its object is to provide a method for producing a porous resin body that, when used in a compound semiconductor polishing pad, produces a porous resin body that is free from scratches when polishing difficult-to-polish wafers and can maintain the polishing rate and surface roughness for a long period of time, and a compound semiconductor polishing pad using the porous resin body.

[0007] The inventors conducted extensive research in light of the above circumstances and found that PES (polyethersulfone) resin or PVDF-HFP resin (solid), which is highly resistant to strong permanganate-based oxidizing agents, and lactose (solid), a disaccharide, were dissolved in a warmed, water-soluble solvent such as N-methyl-2-pyrrolidone, and the resulting melt was molded into a desired shape. When the molded body was placed in cold water, lactose precipitated as a fine solid within the melt. Replacing the precipitated solid and the solvent with water yielded a porous resin body with micropores having an average diameter of approximately 0.2 to 3 μm. Furthermore, they found that polishing with a polishing pad containing this porous resin body resulted in no scratches and maintained the removal rate and surface roughness for a long period of time. The present invention was made based on this finding. [Means for solving the problem]

[0008] That is, the gist of the first invention is a resin porous body having a base resin which is a PES (polyethersulfone) resin or a PVDF-HFP (copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin and micropores formed within the base resin, the size of the micropores being 0.2 to 3 μm.

[0009] The gist of the second invention is a compound semiconductor polishing pad made from the resin porous body of the first invention, which is used to polish difficult-to-polish compound semiconductor wafers using a polishing solution containing a permanganate-based strong oxidizing agent.

[0010] The gist of the third invention is (1) a method for producing a resin porous body having high oxidant resistance and abrasion resistance and fine pores, comprising: (2) a melt preparation step in which a base resin and a disaccharide having high oxidant resistance and abrasion resistance are melted in an organic solvent to obtain a melt; (3) a molding step in which the melt is molded into a thin plate to obtain a thin plate-shaped body; (4) a precipitation step in which the thin plate-shaped body is placed in cold water whose temperature is lower than the melting point of the disaccharide to finely precipitate a solid of the disaccharide in the thin plate-shaped body; (5) a substitution step in which the thin plate-shaped body that has undergone the precipitation step is placed in warm water whose temperature is higher than the cold water to replace the finely precipitated solid of the disaccharide in the thin plate-shaped body and the organic solvent in the thin plate-shaped body with water; and (6) a drying step in which the thin plate-shaped body is dried until all moisture is removed from the thin plate-shaped body.

[0011] The gist of the fourth invention is that in the third invention, the base resin is PES (polyethersulfone) resin or PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin.

[0012] The gist of the fifth invention is that in the third invention, the organic solvent is N-methyl-2-pyrrolidone or 2-pyrrolidone. If room temperature is defined as 10°C to 30°C, N-methyl-2-pyrrolidone has a melting point below freezing (-24°C), and 2-pyrrolidone has a melting point at room temperature (24.6°C).

[0013] The gist of the sixth invention is that in the third invention, the organic solvent is a solvent that disperses in water and dissolves the PES (polyethersulfone) resin and the PVDF-HFP (copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin.

[0014] The gist of the seventh invention is that, in the third invention, the precipitation step involves leaving the thin plate-shaped molded body in the cold water at 5 to 10°C, and the replacement step involves leaving the thin plate-shaped molded body that has undergone the precipitation step in the warm water at 40 to 60°C.

[0015] The gist of an eighth aspect of the present invention is that, in the third aspect of the present invention, the resin porous body has fine pores with an average diameter of 0.2 to 3 μm.

[0016] The gist of the 9th invention is that, in the 2nd invention, the compound semiconductor polishing pad has 48.4 to 85.2 volume % pores, 14.8 to 51.6 volume % of the base resin, and a durometer hardness (Type-D) of 12.5 to 58.1. [Effects of the Invention]

[0017] The resin porous body of the first invention is a PES (polyethersulfone) resin or a PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin that has high resistance to oxidizing agents and abrasion, and is a resin porous body in which the size of the micropores formed in the base resin is 0.2 to 3 μm.Therefore, when used as the base resin of a compound semiconductor polishing pad used in polishing a difficult-to-polish wafer by the CMP method, which uses a polishing liquid that mechanically promotes polishing while also chemically promoting polishing, a compound semiconductor polishing pad that is free from scratches and can maintain its polishing rate and surface roughness for a long period of time can be obtained.

[0018] According to the compound semiconductor polishing pad of the second invention, the base resin is composed of the resin porous body of the first invention, so when it is used to polish hard-to-polish compound semiconductor wafers by the CMP method using a polishing solution containing a permanganate-based strong oxidizing agent, there are no scratches and the polishing rate and surface roughness can be maintained for a long time.

[0019] The third invention relates to a method for producing a porous resin body having high resistance to oxidizing agents and abrasion and micropores, and includes a melt preparation step in which a base resin having high resistance to oxidizing agents and abrasion and a disaccharide (e.g., lactose) are melted in an organic solvent to obtain a melt; a molding step in which the melt is molded into a thin plate to obtain a thin plate-like molded body; a precipitation step in which the thin plate-like molded body is placed in cold water whose temperature is lower than the melting point of the disaccharide to precipitate fine solids of the disaccharide in the thin plate-like molded body; a substitution step in which the thin plate-like molded body that has undergone the precipitation step is placed in warm water whose temperature is higher than the cold water to replace the finely precipitated disaccharide solids in the thin plate-like molded body and the organic solvent in the thin plate-like molded body with water; and a drying step in which the thin plate-like molded body is dried until all moisture is removed from the thin plate-like molded body. As a result, the resin porous body that makes up the compound semiconductor polishing pad is made from a base resin that is highly resistant to strong oxidizing agents, and fine pores are formed within this base resin, so when polishing difficult-to-polish wafers, there are no scratches and the polishing rate and surface roughness S can be maintained for a long period of time.

[0020] In the fourth invention, the resin porous body is PES (polyethersulfone) resin or PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin, so that a resin porous body having high resistance to oxidizing agents and abrasion is obtained.

[0021] In the fifth invention, the organic solvent is N-methyl-2-pyrrolidone or 2-pyrrolidone. If room temperature is defined as 10°C to 30°C, N-methyl-2-pyrrolidone has a melting point below freezing, and 2-pyrrolidone has a melting point at room temperature. These organic solvents dissolve the base resins, PES (polyethersulfone) resin and PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene), and lactose. In the precipitation step, the thin plate-shaped molded body is placed in cold water at a temperature lower than the melting point of lactose, thereby allowing the lactose solid to be precipitated in a fine state in the thin plate-shaped molded body. When the organic solvent is 2-pyrrolidone, which has a melting point at room temperature, in the precipitation step, in addition to the fine precipitation of lactose solid, 2-pyrrolidone solid can also be precipitated.

[0022] In the sixth invention, the organic solvent is a solvent that dissolves in water and dissolves PES (polyethersulfone) resin and PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin. This allows the thin plate-shaped article that has undergone the precipitation step to be left in warm water that is higher than the temperature of the cold water and the melting point of the organic solvent, thereby replacing the lactose solid finely precipitated in the thin plate-shaped article and the organic solvent in the thin plate-shaped article with water.

[0023] In the seventh invention, the precipitation step involves leaving the thin plate-shaped body in cold water at 5 to 10° C., and the substitution step involves leaving the thin plate-shaped body that has been subjected to the precipitation step in warm water at 40 to 60° C. As a result, after finely precipitating solid lactose in the thin plate-shaped body in the precipitation step, the solid lactose precipitated in the thin plate-shaped body and the organic solvent in the thin plate-shaped body are substituted with water in the warm water.

[0024] In the eighth aspect of the present invention, the porous resin body has micropores with an average diameter of 0.2 to 3 μm, which has the advantage that when a compound semiconductor wafer that is difficult to polish is polished using a compound semiconductor polishing pad made of the porous resin body, the edges of the numerous micropores contribute to the polishing mechanism, making it difficult for scratches to occur, and thus favorable polishing rate and surface roughness can be obtained.

[0025] In the ninth invention, the compound semiconductor polishing pad has 48.4 to 85.2 volume % pores, 14.8 to 51.6 volume % base resin, and a durometer hardness (Type-D) of 12.5 to 58.1, so that it is free from scratches and can maintain the polishing rate and surface roughness for a long time. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a perspective view schematically showing a surface polishing apparatus used in polishing by the CMP method, in which a polishing pad according to an embodiment of the present invention is used. [Figure 2] 2 is a plan view for schematically explaining a rotating mechanism of an adhering disk of the surface polishing apparatus of FIG. 1. FIG. [Figure 3] 2 is a process diagram illustrating a manufacturing process for manufacturing a porous resin body that constitutes the polishing pad of FIG. 1. FIG. [Figure 4] FIG. 2 is a diagram showing the chemical structure of a PES resin (polyethersulfone resin), which is an example of a resin constituting the polishing pad of FIG. [Figure 5] FIG. 2 is a diagram showing the chemical structure of PVDF-HFP resin (80% polyvinylidene fluoride + 20% hexafluoropropylene copolymer resin), which is another example of the resin constituting the polishing pad of FIG. [Figure 6] 1 is a table showing the samples used in polishing test 1 and the results of the polishing test. [Figure 7] 1 is a table showing the PES resin proportion, pore proportion, and durometer hardness of Example Products 5 to 6 and 9 in the samples used in Polishing Test 1. [Figure 8]1 is a table showing the PVDF-HFP resin proportion, pore ratio, and durometer hardness of Examples 7 and 8 in the samples used in Polishing Test 1. [Figure 9] FIG. 1 is a 500x SEM photograph of a cross section of Example Product 6 in the sample used in Polishing Test 1, showing pores in Example Product 6. [Figure 10] FIG. 1 is a 10,000x SEM photograph of a cross section of Example Product 6 in the sample used in Polishing Test 1, showing pores in Example Product 6. [Figure 11] FIG. 1 is a 500x SEM photograph of a cross section of Example Product 9 in the sample used in Polishing Test 1, showing pores in Example Product 9. [Figure 12] FIG. 1 is a 10,000x SEM photograph of a cross section of Example Product 9 in the sample used in Polishing Test 1, showing pores in Example Product 9. [Figure 13] FIG. 1 is a 500x SEM photograph of a cross section of Comparative Example 1 in a sample used in Polishing Test 1, showing pores in the Comparative Example 1. [Figure 14] FIG. 1 is a 500x SEM photograph of a cross section of Comparative Example 2 in the sample used in Polishing Test 1, showing pores in the comparative example 2. DETAILED DESCRIPTION OF THE INVENTION

[0027] An embodiment of the present invention will be described below with reference to the drawings. Note that in the following embodiment, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0028] Figure 1 shows a schematic diagram of a surface polishing apparatus 10, with the guide roller support removed, for polishing hard-to-polish compound semiconductor wafers such as SiC wafers, GaN wafers, and InP wafers, according to an embodiment of the present invention. In Figure 1, the surface polishing apparatus 10 includes a circular polishing table (rotary table) 12 rotatably supported about a vertical axis of rotation C1. The polishing table 12 is driven by a table drive motor 14 to rotate at a constant speed in one direction indicated by the arrow in the figure. A compound semiconductor polishing pad 18 (hereinafter referred to as the polishing pad) made of a sheet-like porous resin 17 is attached to the upper surface of the polishing table 12, i.e., the surface against which a workpiece (hard-to-polish compound semiconductor wafer) 16 is pressed.

[0029] The workpiece 16 is held on the lower surface of the application disc 20, i.e., the surface facing the polishing pad 18, and the application disc 20 presses the workpiece 16 against the polishing pad 18 with a predetermined load. A drip nozzle 22 is provided near the application disc 20 of the surface polishing device 10, and a strongly acidic polishing solution PF containing an added strong oxidizing agent of permanganate such as potassium permanganate (KMnO4) is delivered from a tank (not shown) and supplied onto the polishing surface plate 12.

[0030] The surface polishing apparatus 10 is optionally provided with an adjustment tool holding member (not shown) that is rotatable about the rotation axis C1 of the polishing table 12 and movable in the direction of the rotation axis C1 and in the radial direction of the polishing table 12, and an abrasive body adjusting tool (dresser or conditioner) such as a diamond wheel (not shown) that is attached to the lower surface of the adjustment tool holding member, i.e., the surface facing the polishing pad 18. This adjustment tool holding member and the abrasive body adjusting tool attached thereto are pressed against the polishing pad 18 while being rotated and driven by an adjustment tool drive motor (not shown), and are moved back and forth in the radial direction of the polishing table 12, thereby adjusting the polishing surface of the polishing pad 18 and constantly maintaining the surface condition of the polishing pad 18 in a state suitable for polishing.

[0031] 2, at a position eccentric from the rotation axis C1 on the polishing table 12, a short cylindrical application disk 20 holds the workpiece 16, or the object to be polished, on its underside by suction, adhesion, or a holding frame, etc. The outer surface of the application disk 20 is supported by a pair of free-rotating guide rollers 30 and a drive guide roller 32 mounted on a fixed guide roller support base 28 fixed to a frame (not shown), allowing the application disk 20 to rotate about the rotation axis C2. The application disk 20 is rotated about the rotation axis C2 by a rotational force based on the difference in peripheral speed between the polishing table 12 and the polishing pad 18, and the application disk 20 is pressed against the polishing pad 18 on the polishing table 12 by the load of, for example, a weight 34, thereby polishing the workpiece 16.

[0032] The following polishing method is applied during polishing using the surface polishing apparatus 10. Specifically, while the polishing pad 18 attached to the polishing surface plate 12, the attachment disk 20, and the workpiece 16 held on its undersurface are rotated about their respective rotation axes C1 and C2 by the surface plate drive motor 14 and drive guide roller 32, a polishing liquid PF containing no abrasive grains is supplied from the drip nozzle 22 onto the surface of the polishing pad 18, and the workpiece 16 held on the attachment disk 20 is pressed against the polishing pad 18. As a result, the surface to be polished of the workpiece 16, i.e., the surface facing the polishing pad 18, is polished flat by the chemical polishing action of the polishing liquid PF.

[0033] The polishing pad 18 is composed of a porous resin body 17 containing fine pores with an average diameter of 0.2 to 3 μm. The porous resin body 17 functions as the base resin of the polishing pad 18. The porous resin body 17 is made of PES (polyethersulfone) resin, which does not contain abrasive grains, or PVDF-HFP resin (a copolymer resin of 80% polyvinylidene fluoride and 20% hexafluoropropylene), and is molded into a sheet shape with a thickness of approximately 2 to 3 mm. PES resin and PVDF-HFP resin have high resistance to the strong oxidizing agent of permanganate in the polishing solution PF and abrasion resistance that allows a high removal rate PR to be obtained. The PES resin has the chemical structure shown in FIG. 4, and the PVDF-HFP resin has the chemical structure shown in FIG. 5.

[0034] The polishing pad 18 preferably has 48.4 to 85.2 volume % pores, 14.8 to 51.6 volume % base resin, and a durometer hardness (Type-D) of 12.5 to 58.1.

[0035] The porous resin body 17 constituting the polishing pad 18 is manufactured by the manufacturing steps P1 to P5 shown in Fig. 3. In Fig. 3, in the melt preparation step P1, PES resin or PVDF-HFP resin (solid at room temperature) and disaccharide such as lactose (C 12 H 22 O 11 A melt is produced by heating and stirring a lactose (which is solid at room temperature) with a common organic solvent having a freezing point below freezing, such as N-methyl-2-pyrrolidone, at a temperature of 50°C or higher. In the molding step P2, the melt is molded into a thin plate of, for example, about 3 mm by slip casting or blade casting to obtain a thin plate-like molded product. In the precipitation step P3, the thin plate-like molded product is left for about 5 hours in cold water at a temperature sufficiently lower than the melting point of lactose (202.8°C), for example, 5 to 10°C, to precipitate fine solid lactose in the thin plate-like molded product. These fine lactose precipitates (crystals) form micropores in the PES resin after the drying step P5 described below. The size of the micropores is adjusted by the temperature of the cold water and the leaving time, but an average diameter of 0.2 to 3 μm is recommended.

[0036] In the subsequent substitution step P4, the thin plate-shaped body that has been subjected to the precipitation step P3 is left for about 5 hours in warm water at a temperature higher than the cold water and the melting point of 2-pyrrolidone, for example, 40 to 60°C, thereby replacing the finely precipitated lactose solids in the thin plate-shaped body and the organic solvent in the thin plate-shaped body with water and hardening the thin plate-shaped body. Then, in the drying step P5, the thin plate-shaped body is dried until all moisture is removed. This results in a thin plate-shaped PES or PVDF-HFP resin porous resin body (base resin of polishing pad 18) 17 having micropores of about 0.2 to 3 μm.

[0037] N-methyl-2-pyrrolidone has the chemical formula CHNO, a freezing point of −24° C., a boiling point of 202° C., is soluble in water, and is capable of dissolving the base resin (PES resin or PVDF-HFP resin). As described in the melt preparation step P1, the precipitation step P3, and the substitution step P4 above, an organic solvent other than N-methyl-2-pyrrolidone may be used as long as it can melt the PES resin, has a freezing point below the freezing point, and can be substituted for water at the temperature of hot water.

[0038] [Polishing test 1] The following describes polishing test 1 for semiconductor wafers conducted by the present inventors. In polishing test 1, comparative examples 1 and 2 shown in FIG. 6 and examples 5 to 9 were applied to an apparatus configured similarly to the surface polishing apparatus 10 shown in FIG. 1, and 4-inch diameter SiC wafers were polished under the test conditions for polishing test 1 described below. Examples 5 and 6 were produced using the manufacturing process shown in FIG. 3, with the proportions of N-methyl-2-pyrrolidone, lactose, and PES resin changed so that the resulting porosity (volume %) differed between the examples. Examples 7 and 8 were produced using the manufacturing process shown in FIG. 3, with the proportions of N-methyl-2-pyrrolidone, lactose, and PVDF-HFP resin changed so that the resulting porosity (volume %) differed between the examples. Example 9 was produced using the manufacturing process shown in FIG. 3, with the proportions of 2-pyrrolidone, lactose, and PES resin changed so that the resulting porosity (volume %) differed between the examples.

[0039] Figure 7 shows the volume fraction of the PES resin, the volume fraction of the pores, and the durometer hardness (Type-D) of Examples 5 to 6 and 9. Figure 8 shows the volume fraction of the PVDF-HFP resin, the volume fraction of the pores, and the durometer hardness (Type-D) of Examples 7 and 8.

[0040] Figures 9 and 10 show SEM photographs at 500x and 10,000x magnification of Example Product 6, which is representative of Examples 5 to 8. Micropores of approximately 0.2 to 2 or 3 μm are observed in the SEM photograph of Figure 10. Figures 11 and 12 show SEM photographs at 500x and 10,000x magnification of Example Product 9. The SEM photograph of Figure 12 shows homogeneous micropores of approximately 0.2 to 3 μm. Example Product 9 uses 2-pyrrolidone, which has a melting point at room temperature (24.6°C), as an organic solvent to dissolve the base resin. Therefore, in the precipitation step P3, solid 2-pyrrolidone is precipitated in addition to lactose, contributing to the formation of pores. Note that DMSO (dimethyl sulfoxide), which has a melting point at room temperature (18.4°C), may be used instead of the 2-pyrrolidone.

[0041] Comparative Example 1 is made of a hard polyurethane resin in which pores of 20 to 40 μm have been created using a pore-forming agent. FIG. 13 shows an SEM photograph of Comparative Example 1 at 500x magnification. Pores of approximately 20 to 40 μm can be observed in the SEM photograph of FIG. 13. Comparative Example 2 is a nonwoven fabric in which intertwined polyester fibers are bonded with polyurethane resin, with gaps of approximately 100 μm formed between the fibers. FIG. 14 shows an SEM photograph of Comparative Example 2 at 500x magnification. Large pores of approximately 100 μm can be observed in the SEM photograph of FIG. 14.

[0042] The polishing rate PR, surface roughness Sa, and number of scratches on the SiC wafer after the polishing test in Polishing Test 1 were measured using the following methods.

[0043] [Test conditions for polishing test 1] Workpiece: 4-inch diameter SiC wafer (0001) Si surface, tilt angle 4° Work rotation speed: 60 rpm Polishing pad diameter: 300mmφ Polishing pad rotation speed: 60 rpm Polishing pressure: 42kPa Polishing liquid: KMnO4 (0.25mol / l) pH=3.2 (abrasive grains not included) Polishing liquid flow rate: 10ml / min Polishing time: [Comparative example 1] 200 hours [Comparative example 2] 70 hours [Example Product 5] 2 hours [Example Product 6] 2 hours [Example Product 7] 2 hours [Example Product 8] 2 hours [Example Product 9] 2 hours

[0044] [Method for measuring polishing rate PR] The difference in mass of the SiC wafer before and after the polishing test was determined using an analytical balance, and the amount of polishing (wear thickness) was calculated from the known density of the SiC wafer and the surface area of ​​the polished surface. The polishing rate PR (nm / h) was calculated by dividing the amount of polishing by the polishing time.

[0045] [Surface roughness Sa measurement method] The surface roughness Sa of the surface profile of the polished surface of the SiC wafer after the polishing test was measured using a white light interference microscope (Hitachi High-Tech VS-1330), and the arithmetic mean surface roughness Sa specified in ISO25178 was calculated.

[0046] [Method for measuring the number of scratches] The entire polished surface of the SiC wafer was observed with a confocal differential interference microscope (Lasertec Optelics Hybrid), and scratches detected using the included scratch assessment software were counted as one scratch.

[0047] FIG. 6 shows the polishing test results (polishing rate PR (nm / h) and surface roughness Sa (nm) of the polished surface) and the number of scratches (count) when Examples 5 to 9 and Comparative Examples 1 and 2 were used. The polishing results show that Examples 5 to 9 achieved a higher polishing rate PR (nm / h) than Comparative Examples 1 to 2. Furthermore, Examples 5 to 9 achieved a better surface roughness Sa than Comparative Examples 1 and 2. SiC wafers are polished while supported by the edges of the bubbles, but Examples 5 to 9 have fine pores of about 0.2 to 3 μm, so it is believed that the above polishing results were achieved because they were supported by many edges.

[0048] As described above, according to the resin porous body 17 of this embodiment, the base resin is PES (polyethersulfone) resin or PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin, which has high resistance to oxidizing agents and abrasion, and the size of the micropores formed in the base resin is 0.2 to 3 μm.Therefore, since the resin porous body 17 is used as the base resin of a compound semiconductor polishing pad used in polishing by the CMP method, which uses a resin polishing pad that mechanically promotes polishing and a polishing liquid that chemically promotes polishing when polishing a difficult-to-polish wafer by the CMP method, a compound semiconductor polishing pad that is free of scratches and can maintain its polishing rate and surface roughness for a long time can be obtained.

[0049] The resin porous body 17 of this embodiment has fine pores with a size of 0.2 to 3 μm, and therefore, when the polishing pad 18 to which the resin porous body 17 is applied is used for polishing a hard-to-polish compound semiconductor wafer by the CMP method using a polishing liquid containing a permanganate-based strong oxidizing agent, there are no scratches and the polishing rate and surface roughness can be maintained for a long time.

[0050] The manufacturing method of the resin porous body 17 constituting the polishing pad 18 of this embodiment includes a melt preparation process P1 in which a base resin and lactose having high resistance to oxidizing agents and abrasion are melted in an organic solvent to obtain a melt; a molding process P2 in which the melt is molded into a thin plate to obtain a thin plate-shaped body; a precipitation process P3 in which the thin plate-shaped body is placed in cold water whose temperature is lower than the melting point of lactose to finely precipitate solid lactose in the thin plate-shaped body; a substitution process P4 in which the thin plate-shaped body that has undergone the precipitation process P3 is placed in warm water whose temperature is higher than the cold water to replace the finely precipitated solid lactose in the thin plate-shaped body and the organic solvent in the thin plate-shaped body with water; and a drying process P5 in which the thin plate-shaped body is dried until all moisture is removed from the thin plate-shaped body. As a result, the resin porous body that constitutes the polishing pad 18 is made of PES resin or PVDF-HFP resin, which is highly resistant to strong oxidizing agents, and fine pores are formed within the PES resin or PVDF-HFP resin, so that when polishing difficult-to-polish wafers, there are no scratches and the polishing rate PR and surface roughness Sa can be maintained for a long period of time.

[0051] The base resin in this embodiment is PES (polyethersulfone) resin or PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin, so a porous resin body with high resistance to oxidizing agents and wear is obtained.

[0052] The organic solvent in this example is N-methyl-2-pyrrolidone or 2-pyrrolidone. These solvents dissolve the base resins, PES (polyethersulfone) resin and PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin, and lactose, and in the precipitation step P3, the thin plate-shaped body is left in cold water at a temperature lower than the melting point of lactose, thereby allowing the lactose solid to be precipitated finely in the thin plate-shaped body.

[0053] The organic solvent in this example is a solvent that dissolves in water and dissolves PES (polyethersulfone) resin and PVDF-HFP resin. By leaving the thin plate-shaped molded body that has been subjected to the precipitation step P3 in warm water that is higher than the temperature of the cold water and the melting point of the organic solvent, the lactose solids that have precipitated finely in the thin plate-shaped molded body and the organic solvent in the thin plate-shaped molded body can be replaced with water.

[0054] In this example, the precipitation step P3 involves leaving the thin plate-shaped body in cold water at 5 to 10°C, and the substitution step P4 involves leaving the thin plate-shaped body that has been subjected to the precipitation step P3 in warm water at 40 to 60°C, which is sufficiently higher than the melting point of lactose. As a result, after fine solid lactose can be precipitated in the thin plate-shaped body in the precipitation step P3, the solid lactose precipitated in the thin plate-shaped body and the organic solvent in the thin plate-shaped body are substituted with water in the warm water.

[0055] The resin porous body of this embodiment constitutes a polishing pad 18 having fine pores, and this polishing pad 18 allows the workpiece 16 to be polished without scratches using a polishing solution PF containing a permanganate-based strong oxidizing agent, thereby obtaining a polishing pad 18 that can maintain the polishing rate PR and surface roughness Sa for a long period of time.

[0056] The porous resin body of this embodiment has micropores with an average diameter of 0.2 to 3 μm, which has the advantage that when the workpiece 16 is polished with the polishing pad 18 made of the porous resin body, the edges of the numerous micropores contribute to the polishing mechanism, making it difficult for scratches to occur, and thus favorable polishing rate PR and surface roughness Sa can be obtained.

[0057] The polishing pad 18 of this embodiment has pores of 48.4 to 85.2 volume %, a base resin of 14.8 to 51.6 volume %, and a durometer hardness of 12.5 to 58.1, so it is free from scratches and can maintain the polishing rate PR and surface roughness Sa for a long period of time.

[0058] Although the preferred embodiment of the present invention has been described in detail above with reference to the drawings, the present invention is not limited to this and may be implemented in other modes.

[0059] For example, in the above-described examples, lactose was used as a disaccharide (an oligosaccharide consisting of two monosaccharide molecules), but maltose, sucrose, cellobiose, etc. may be used instead of lactose. Any disaccharide may be used as long as it is a solid that dissolves in a water-soluble solvent and water.

[0060] Furthermore, although the polishing solution PF in the above-described examples does not contain abrasive grains, it may also contain abrasive grains.

[0061] Furthermore, the polishing solution PF in the above-described examples contains a permanganate-based strong oxidizing agent such as potassium permanganate (KMnO4), but other strong oxidizing agents may also be added.

[0062] Furthermore, although the polishing pad 18 in the above-described embodiment does not contain abrasive grains, it may contain abrasive grains.

[0063] Furthermore, although the resin porous body in the above-described embodiment was used as the polishing pad 18, it may also be used for other purposes, such as a water-adhesive pad for fixing a compound semiconductor wafer on a polishing table, synthetic leather, vibration-proof sheets, sound-absorbing materials, water-absorbing and water-retaining bodies, separators and separation membranes for fuel cells, etc.

[0064] The above is merely one embodiment, and although other examples will not be given, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art within the scope of the invention. [Explanation of symbols]

[0065] 16: Workpiece (hard-to-polish compound semiconductor wafer) 17: Porous resin 18: Polishing pad (compound semiconductor polishing pad made of porous resin) PF: Polishing fluid

Claims

1. The base resin is PES (polyethersulfone) resin or PVDF-HFP (a copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin, and micropores are formed in the base resin, and the size of the micropores is 0.2 to 3 μm. A porous resin body characterized by:

2. A compound semiconductor polishing pad made of the resin porous body of claim 1, Polishing difficult-to-polish compound semiconductor wafers using a polishing solution containing a strong oxidizing agent based on permanganate 1. A compound semiconductor polishing pad comprising:

3. A method for producing a resin porous body having high oxidant resistance and abrasion resistance and fine pores, comprising: a melt preparation step of melting a base resin and a disaccharide, which are highly resistant to oxidizing agents and abrasion, in an organic solvent to obtain a melt; a molding step of molding the melt into a thin plate to obtain a thin plate-shaped molded body; a precipitation step of leaving the thin plate-like molded body in cold water at a temperature lower than the melting point of the disaccharide to precipitate a fine solid of the disaccharide in the thin plate-like molded body; a substitution step in which the thin plate-shaped body that has been subjected to the precipitation step is left in hot water having a temperature higher than that of the cold water, and the disaccharide solid finely precipitated in the thin plate-shaped body and the organic solvent in the thin plate-shaped body are substituted with water; a drying step of drying the thin plate-shaped body until all moisture is removed from the thin plate-shaped body. A method for producing a resin porous body, comprising:

4. The base resin is PES (polyethersulfone) resin or PVDF-HFP (copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin. The method for producing a resin porous body according to claim 3.

5. The organic solvent is N-methyl-2-pyrrolidone or 2-pyrrolidone. The method for producing a resin porous body according to claim 3.

6. The organic solvent is a solvent that disperses in water and dissolves the PES (polyethersulfone) resin and the PVDF-HFP (copolymer of 80% polyvinylidene fluoride and 20% hexafluoropropylene) resin. The method for producing a resin porous body according to claim 3.

7. The precipitation step involves leaving the thin plate-shaped body in the cold water at 5 to 10°C, and the replacement step involves leaving the thin plate-shaped body that has undergone the precipitation step in the warm water at 40 to 60°C.

2. The method for producing a resin porous body according to claim 1.

8. The resin porous body has fine pores with an average diameter of 0.2 to 3 μm. The method for producing a resin porous body according to claim 3.

9. The compound semiconductor polishing pad has 48.4 to 85.2 volume % of pores, 14.8 to 51.6 volume % of the base resin, and a durometer hardness (Type-D) of 12.5 to 58.

1.

3. The compound semiconductor polishing pad according to claim 2.

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