JPS639406Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a thermoplastic polyurethane polisher used for finishing the processed surface of a workpiece, such as Si, into a mirror finish by etching or wrapping grinding. Polishing, which is generally performed during the manufacture of Si wafers, removes the striations and process-altered layers on the surface of the Si wafer polished by lapping, finishes the perfect crystal layer into a smooth mirror surface, and polishes the crystal axis of the Si single crystal. The purpose is to maintain a constant angle of the polished surface with respect to the surface and at the same time obtain a crystallographically defect-free surface.
Extremely high precision processing is required. Therefore, this polishing device has a structure similar to a lapping plate, in which the Si wafer is held between two sides, and the polisher is fixed on top and bottom opposing surface plates. A polishing liquid in which silicon dioxide fine powder of ~200 Å is suspended is poured between these polishers and the Si wafer to rub them together. To distinguish this polisher from conventional polishers, a mechanical polisher is used. It is called chemical polishing. In recent years, with the development of large-scale integrated circuits, diameters of 10
It is becoming more and more common to use fairly large Si wafers of cm or more as is without dicing, so the flatness of the wafers is becoming more important. Plans are being made to increase processing pressure. From this point of view, there is a growing demand for very large-sized polyshears with uniform thickness, a uniform surface structure that is effective for processing, and excellent durability. Flocked products such as, metal plates made of tin or lead, artificial leather with a foam layer formed on the surface, natural leather, wood, wax, or fiber materials impregnated with pitch, pine resin, etc. are known. However, these do not satisfy all of the above-mentioned conditions, and in particular, it has been impossible to provide a large-sized polisher having a uniform surface structure that is effective for processing over the entire surface at a low cost. As has been known in the past, the requirements for a polisher are to have fine grooves, openings, etc. on the surface of the polisher in order to have an abrasive retention function, and to have an appropriate hardness. The key is to choose a material that makes it easy to form holding grooves. This invention eliminates the drawbacks of conventional polishers and creates a uniform uneven surface on the surface of thermoplastic polyurethane, which is effective for polishing solid substrates such as Si wafers, and has a function of retaining the abrasive and improves the precision of the machined surface without foaming. The present invention provides an inexpensive, large-sized policy that takes mass production into account. In order to realize the polisher of the present invention that achieves this purpose, a mold whose surface has a certain pattern of unevenness formed by chemical etching is pressed onto the surface of a thermoplastic polyurethane that does not contain pores, and this thermoplastic It is obtained by heating polyurethane and coining and transferring, on the surface of the thermoplastic polyurethane, uneven portions corresponding to the uneven portions formed on the mold. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 shows an example of the method for realizing the polysier of the present invention, which shows a single thermoplastic polyurethane 1 that does not contain pores (non-foamed) that has been processed into a parallel flat plate in advance, and a thermoplastic polyurethane 1 that has not been foamed. A pattern mask 3 in which the uneven portions 2 to be formed on the surface are formed by chemical etching is prepared, and these are sandwiched between a pair of pressurizing plates 4 processed into a highly accurate plane. Thermoplastic polyurethane 1
The thermoplastic polyurethane 1 is heated to an appropriate temperature at which it becomes soft, but in order to improve work efficiency, if the thermoplastic polyurethane 1, pattern mask 3, and pressure plate 4 are all placed in a heating furnace, In order to avoid thermal deformation of the pattern mask 3 and the pressure plate 4, it is preferable that these are made of metal. Alternatively, it is also possible to integrate the pattern mask 3 and the pressure plate 4, and carve the uneven portions 2 of the pattern mask 3 on the surface of one of the pressure plates 4, and use this as a mold. When the pressure plate 4 and the pattern mask 3 are separable as in this embodiment, it is desirable that the flatness and parallelism of the pattern mask 3 be as accurate as possible. The specific shape of the concavo-convex portion 2 of the pattern mask 3 may be any known pattern as long as it can sufficiently function as a policy. An array of rectangular blind holes as shown in Figure 2,
Some typical shapes include an array of circular through holes as shown in FIG. 3, which shows another specific example. The pressure plate 4 approaches each other so that the planes that press the pattern mask 3 and the pressure plate 4 are always parallel, and the uneven portions corresponding to the uneven portions 2 of the pattern mask 3 are made of thermoplastic polyurethane 1. By applying an appropriate pressure to the thermoplastic polyurethane 1 and the pattern mask 3 for a certain period of time so as to cause coining transfer to the surface of the mask, and cooling them with air or liquid, the surface is made to correspond to the uneven portions 2 of the pattern mask 3. It is possible to obtain a thermoplastic polyurethane 1 in which the uneven portions having the shape of the above are coined and transferred. In addition, in FIG. 4 showing another embodiment aimed at improving production efficiency, on the outer peripheral surface of one of the pair of work rolls 6 that press the thermoplastic polyurethane 5,
If the surface of the thermoplastic polyurethane 5 is carved with uneven portions 8 having a shape corresponding to the uneven portions 7 to be coined and transferred, and the polisher is manufactured by a method such as a rolling operation, extremely long polishers can be produced quickly and easily. can be obtained easily. Next, as a specific example of this embodiment, the shore hardness
2mm thick thermoplastic polyurethane with Hs 65-95
The length of one side is 300mm, and the thickness is 0.2mm.
A pattern mask is prepared in which uneven parts consisting of composite through-holes with a grain size of 60 mesh and 20 mesh are engraved by a chemical etching method on highly corrosion-resistant stainless steel with a side length of 300 mm. As shown in the figure, thermoplastic polyurethane is used as the polisher.
Heat to 150℃ and weigh 200Kg (approximately 220g ^per 1cm2)
When the polyurethane and the pattern mask were subjected to a load of 30 seconds for 30 seconds and then cooled with water, irregularities corresponding to the irregularities of the pattern mask were uniformly formed on the surface of the polyurethane to a depth of about 0.1 mm. By changing the pressing force of the pressure plate, the pressing time, the pressing temperature for the thermoplastic synthetic resin, the thickness of the pattern mask, etc., the depth of the uneven portion to be coined and transferred to the surface of the thermoplastic synthetic resin can be adjusted. It is possible to change the degree arbitrarily. A Si wafer with a diameter of approximately 75 mm was polished with colloidal silica using the polisher manufactured in the above-mentioned example, and the results were as follows: The average density of stacking faults (average OSF density) is shown in the table.
The same table also shows the processing accuracy when using conventional artificial leather polisher for comparison. In addition,
The shape of the concavo-convex portion of the pattern mask was a mesh-like one with a grain size of 60 mesh, or a combination of grain sizes of 60 mesh and 20 mesh. In addition, in the case of a smooth polyurethane polisher with a shore hardness Hs of 90 and no uneven parts, the machining speed will be lower.
It was found that it was less than 0.3 μm/hour and was unsuitable for use as a polisher.

[Table] As described above, the polyshear of the present invention is obtained by heat-forming thermoplastic polyurethane, which is easy to process, through a mold that has unevenness carved into the surface, so it is inexpensive and highly suitable for mass production. Since it is a large area polisher with a uniform surface structure, it will become more useful as Si wafers become larger in the future. Furthermore, the polisher according to the present invention has high processing accuracy and is made of polyurethane, so it is excellent in durability, and furthermore, cleaning work before and after processing can be performed extremely easily.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of obtaining a policy according to the present invention, FIG. 2 is an enlarged view of the part shown by the arrow in FIG.
FIG. 3 is an enlarged view similar to FIG. 2 showing the shape of another embodiment of the pattern mask, and FIG. 4 is a perspective view showing the configuration of another embodiment. In the drawing, 1 and 5 are thermoplastic polyurethane, 2 is the uneven part of the pattern mask, 3 is the pattern mask,
4 is a pressure plate, 6 is a work roll, 7 is an uneven part coined into the thermoplastic polyurethane, and 8 is an uneven part of the work roll.

Claims (1)

[Scope of utility model registration request] A fixed pattern with a particle size in the range of 60 mesh to 20 mesh or a pattern with particle size in the range of 60 mesh to 20 mesh is formed on the surface of a plate-shaped thermoplastic polyurethane that does not contain pores and has a shore hardness Hs in the range of 65 < Hs < 95. Depth 0.1 created by overlapping and transferring multiple fixed patterns
A thermoplastic polyurethane polisher characterized by having irregularities of about mm size.