[0020] The grinding wheel for polishing of the present invention (hereinafter referred to as the present polishing wheel) is characterized by that diamond-containing resin fibers (hereinafter referred to simply as fibers) are implanted in a polishing substrate in a form of a brush. For the present grinding wheel, as a material of the grinding substrate, various ones may be used, and a metal is preferred since it is excellent in mechanical strength, and stainless, aluminum or steel stock may, for example, be mentioned.

[0021] For implantation, the fibers may directly be implanted in one side, both sides or side face of the disk in a form of a brush, or the fibers may be indirectly implanted in such a manner that brushes (in such a shape that fibers are fixed to an entangled wire such as a brush part of a test tube brush for example) are constituted by the fibers, which are further fixed to the grinding substrate by means of e.g. bonding. Fixation of the fibers to the grinding substrate is not particularly limited, and adhesion, welding, soldering or fastening by a wire may, for example, be mentioned. Here, in the present specification, implantation in a form of a brush means that the fibers are densely implanted.

[0022] In a case of directly implanting the fibers, each fiber may be implanted with a short interval. Otherwise, it is possible to obtain the present grinding wheel 10 by forming a large number of small holes 16 on a discal grinding substrate 11 , and putting and implanting a plurality of fibers 12 in the small pores 16 in a bundle, as illustrated in FIGS. 1 ( a ) and 1 ( b ). The number of the fibers 12 in a bundle is preferably at a level of from 2 to 100, more preferably at a level of from 5 to 50, particularly preferably from 10 to 30. If the number of the fibers 12 in a bundle is too large, rigidity tends to be high, and there is fear that scars may form due to polishing.

[0023] The interval between bundles (hereinafter referred to as pitch) is optionally selected depending upon the number of the fibers in a bundle. In a case of FIG. 1 ( a ), the pitch is the minimum distance between two adjacent small holes 16 . When the number of the fibers in a bundle is large, the pitch is increased, and when the number of the fibers in a bundle is small, the pitch is reduced. If the pitch is small, the load during polishing tends to be heavy, and accordingly the pitch is preferably at least 5 mm, more preferably from 5 to 20 mm. The pitch may be constant in the present grinding wheel, or the pitch in a radius direction may be different from that in a circle direction.

[0024] Here, as a fixation method of the fibers 12 in a bundle, the fibers 12 may directly be bonded to the grinding substrate 11 by an adhesive for implantation, or the fibers 12 may be bent at least double, hitched on a wire, and fastened and fixed with the wire for implantation. FIGS. 1 ( a ) and 1 ( b ) illustrate an example wherein fibers 12 are fixed by a wire which is not shown. It is also possible that the fibers 12 in a bundle are fastened by a metal ring, which are pressed into small holes 16 on a grinding substrate 11 , or the metal ring is fixed by e.g. welding.

[0025] FIGS. 2 ( a ) and 2 ( b ) illustrate an example wherein fibers 22 are implanted in a wire 27 to obtain a brush 28 , and a plurality thereof is bonded to the side face of a grinding substrate 21 to obtain a grinding wheel 20 of the present invention. FIG. 3 illustrates an example wherein brushes 38 similar to those in FIG. 2 ( b ), comprising fibers 32 , are fixed to grooves 33 formed on a grinding substrate 31 in addition to the side face of the grinding substrate 31 to obtain a grinding wheel 30 of the present invention.

[0026] FIGS. 4 ( a ) and 4 ( b ) illustrate an example wherein small holes 46 are formed on the flat surface of a grinding substrate 41 having grooves 43 formed thereon, and fibers 42 are fixed in the same construction as illustrated in FIGS. 1 ( a ) and 1 ( b ), and brushes 48 similar to those in FIG. 2 ( b ), obtained by implanting fibers 42 in a wire 47 , are fixed to the side face in the same construction as illustrated in FIG. 3 , and both constructions are combined to obtain a grinding wheel 40 of the present invention.

[0027] In the present invention, the type of the resin of the fibers is not particularly limited, and a nylon resin may, for example, be mentioned in view of the balance between the hardness and elasticity. The diameter of the fibers is not particularly limited also, but fibers having a diameter of from 0.1 to 1.5 mm are preferred since they are readily available. The diameter of the fibers is more preferably from 0.1 to 1.0 mm, particularly preferably from 0.1 to 0.4 mm.

[0028] The length of the fibers is not particularly limited also, but fibers having a length of from 0.5 to 10 mm are preferred since they are readily available. The length of the fibers is more preferably from 1 to 6 mm in view of e.g. processability. It is more preferred that the diameter of the fibers is from 0.1 to 0.4 mm, and the length of the fibers is from 1 to 6 mm. The ratio of (the length of the fibers)/(the diameter of the fibers) is particularly preferably from 10 to 30, whereby the degree of polishing and the surface state can readily be controlled. As an example of a preferred fiber shape, fibers having a length of 3 mm and a diameter of 0.15 mm may be mentioned.

[0029] In the present invention, the particle size of the diamond is optionally selected depending upon the required surface roughness, and it is preferably from #400 to #3,000 as stipulated in JIS R6001 (electric resistance test). If the particle size of the diamond is rougher than #400, scars are likely to form on the polished surface, and further, if the particle size of the diamond is finer than #3,000, the surface roughness to be obtained is less likely to be lessened any more, and it tends to be difficult to prepare the grinding wheel.

[0030] In the present invention, the particle size of the diamond is preferably such that the particle diameter is from 4 to 30 μm at a 50% point of the cumulative height (electric resistance test). If the above particle diameter is larger than 30 μm, scars are likely to form on the polished surface, and if the particle diameter is smaller than 4 μm, the surface roughness to be obtained is less likely to be lessened any more, and it tends to be difficult to prepare the grinding wheel.

[0031] Further, the particle size of the diamond is more preferably such that the particle diameter is from 4 to 14 μm at a 50% point of the cumulative height, whereby an edge part of teeth forming grooves of an object to be polished such as a wafer boat, can be polished without impairing accuracy of form, while chamfering the edge part into a curved shape with a curvature radius of from 0.2 to 3 mm (hereinafter referred to as R-chamfering).

[0032] In the present invention, the content of the diamond contained in the fibers is preferably from 5 to 40 mass % in the fibers. Here, the type of the diamond is not particularly limited, and synthetic diamond or natural diamond may optionally be used.

[0033] As an object to be polished by using the present grinding wheel, a surface for which mirror polishing is required may be mentioned. It is suitable to polish the surface of a complicated shape part of an object to be polished having a complicated shape by using the present grinding wheel. For example, in a case where the surface to be polished is the surface of a groove part of a wafer boat, said groove part is weak in mechanical strength and has a complicated shape, and accordingly it is preferably polished by the present grinding wheel.

[0034] Further, it is particularly preferred to polish the surface of a complicated shape part of an object to be polished having a complicated shape, on which a vapor deposition film by CVD or a vapor deposition film by PVD is formed, by the present grinding wheel, whereby effects of use of the present grinding wheel can be obtained. The surface of a groove part of a SiC wafer boat, the surface of which is covered with a SiC film formed by CVD, may, for example, be mentioned.

[0035] The surface roughness on the surface polished by the present grinding wheel can be controlled by selecting the particle size of the diamond. The surface roughness Ry on the surface to be in contact with e.g. a wafer is particularly preferably at most 5 μm, whereby excellent smoothness tends to be obtained, and the surface roughness Ry is more preferably at most 2 μm. It is particularly preferred as a slip countermeasure of a wafer that the surface roughness Ry is at most 1 μm and the surface roughness Ra is at most 0.1 μm.

[0036] In a case where the vapor deposition film surface is polished by using the present grinding wheel, the thickness of the vapor deposition layer after polishing is preferably at least 20 μm, whereby functions of the CVD vapor deposition film such as prevention of diffusion of impurities in the substrate are not impaired.

[0037] As conditions of polishing by using the present grinding wheel, the peripheral speed of the grinding wheel is preferably from 100 to 1,500 m/min, more preferably from 300 to 800 m/min, the feed rate of the grinding wheel is preferably from 0.5 to 20 mm/min, more preferably from 3 to 10 mm/min, and the depth of cut by the grinding wheel is preferably from 0.1 to 5 mm, whereby the surface roughness Ry on the polished surface of at most 1 μm is likely to be obtained.

[0038] Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples.

[0039] As samples 4 for evaluation (hereinafter referred to simply as samples), a plurality of blocks (30×12×100 mm) made of silicon-impregnated SiC having four grooves (20×12×10 mm) formed thereon with an interval of 10 mm, were prepared. Some of the blocks were put in a CVD apparatus to form a CVD film of SiC on their surface. The thickness of the CVD film was 60 μm as calculated from the change in dimension. Further, as the surface state on the CVD film surface, the surface roughness Ra was 1.5 μm and the surface roughness Ry was 15 μm.