JPH0661702B2 - Suede-like polishing cloth - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a suede-like polishing cloth, and more particularly to a semiconductor substrate having excellent chemical resistance and good durability, particularly for integrated circuit devices, such as high-purity silicon. The present invention relates to a suede-like polishing cloth suitable for mirror-finishing a wafer made of, for example, a compound semiconductor, or for finishing polishing of glass, metal, ceramics, or the like.

(Prior Art) A woven or non-woven fabric made of natural fibers, recycled fibers or synthetic fibers, or a substrate obtained by filling a resin such as a polyurethane elastomer or a rubber-like substance such as styrene butadiene rubber or nitrile butadiene rubber into these. A suede-like polishing cloth obtained by coating a solution of a polyurethane elastomer, treating it with a coagulating liquid and wet coagulating it to form a porous silver surface layer, washing with water and drying, and then grinding the surface of the silver surface layer Well-known, fine free abrasive grains such as cerium oxide, aluminum oxide, and silicon oxide are dispersed in the mirror finishing process of wafers made of high-purity silicon and compound semiconductors, or the finishing process of glass products, metal products, etc. It is widely used for so-called precision polishing, in which polishing is performed while supplying a weak polishing liquid.

Conventionally, in the case of polishing using a suede-like polishing cloth, the processing conditions such as the type, particle size, concentration, etc. of the abrasive grains in the supplied polishing liquid, or the temperature, pressure, rotation speed, etc. during polishing are set appropriately Thus, the desired finishing accuracy is obtained. Further, in order to improve the finish condition, the polishing liquid is adjusted to pH 9 to 1
A general method is to adjust the alkalinity to 2 or mix a polishing liquid with a chemical such as sodium hypochlorite to polish while polishing the surface of the object to be polished.

However, conventionally used suede-like polishing cloths do not have sufficient alkali resistance and chemical resistance and cannot maintain good polishing performance for a long time. Several suede-like sheet materials with improved hydrolysis resistance (alkali resistance) have been proposed, but in this case as well, there is a problem with chemical resistance, such as poor resistance to sodium hypochlorite. . That is, the present situation is that a suede-like polishing cloth excellent in hydrolysis resistance (alkali resistance), chemical resistance and polishing durability has not been proposed yet.

(Problems to be Solved by the Invention) The present inventors have completed as a result of earnest research in view of the above problems, and an object of the present invention is to provide hydrolysis resistance,
It is to provide a suede-like polishing cloth with excellent chemical resistance, durability, and a long working life.

(Means for Solving the Problem) The above-mentioned object is to coat a substrate with a water-miscible organic solvent solution of a polyurethane elastomer and treat it with an aqueous coagulating liquid to form a porous silver surface layer on the substrate. A suede-like polishing cloth formed by grinding the surface of a face layer, which is achieved by including 30 mol% or more of polyhexamethylene carbonate as a polyol component of the polyurethane elastomer.

The substrate used in the present invention includes a textile fabric such as cotton, rayon, polyamide, polyester, polyacrylonitrile or the like, or a woven or non-woven fabric made of a mixture thereof, or a rubber-like substance such as styrene-butadiene rubber or nitrile-butadiene rubber. Examples thereof include those obtained by filling a resin such as polyurethane elastomer, but are not particularly limited thereto.

Generally, a polyurethane elastomer is produced from polyisocyanate, a polyol and a chain extender, but the polyurethane elastomer used for forming the silver surface of the present invention contains polyhexamethylene carbonate as a polyol component in an amount of 30 mol% or more, preferably It contains 50 mol% or more. When the proportion of polyhexamethylene carbonate is less than 30 mol%, hydrolysis resistance (alkali resistance) and chemical resistance are insufficient.

In the present invention, when only polyhexamethylene carbonate is used as the above-mentioned polyol component, hydrolysis resistance and chemical resistance are good, which is preferable, but other polyols may be used together and copolymerized. Examples of the polyol used in combination include polyester polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polyethylene propylene adipate glycol, polybutylene adipate glycol, polyethylene butylene adipate glycol, polypentamethylene adipate glycol, or polyethylene ether glycol, polypropylene ether. Polyols such as glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and other polyether polyols having hydroxyl groups at both ends and having a molecular weight of 500 to 8,000 can be used. As polyols to be copolymerized, polyethers are preferable to polyesters because they have better hydrolysis resistance and chemical resistance.

Examples of the polyisocyanate used for the silver surface polyurethane elastomer of the present invention include diphenylmethane-4,
Organic diisocyanates such as 4'-diisocyanate, tolylene-2,4-diisocyanate, xylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate and hexamethylene diisocyanate, or a mixture thereof can be used. As a chain extender,
Low molecular weight compounds containing active hydrogen groups such as ethylene glycol, propylene glycol, butylene glycol,
Examples thereof include glycols such as diethylene glycol, diamines such as ethylenediamine, trimethylenediamine, propylenediamine, butylenediamine, and amino alcohols.

Examples of the solvent that dissolves the silver surface polyurethane elastomer having the above composition include water-miscible organic solvents such as dimethylformamide, dimethylsulfoxide, tetrahydrofuran, dimethylacetamide, ethylacetate, and dioxane. It is not limited. The concentration of elastomer solids in the polyurethane elastomer solution is preferably 10-40.
%, More preferably 15 to 30% by weight. When the elastomer solid content concentration is too low, the solution viscosity is too low, and the solution excessively penetrates into the substrate, making it difficult to form a good porous silver surface layer.

To produce the suede-like polishing cloth of the present invention, for example, the following may be carried out. That is, the polyurethane elastomer solution for silver surface formation having the composition as described above is applied onto the substrate by a suitable coating means such as a roll coater or a knife coater, preferably 150 to 1500 g / cm ² , and more preferably 300. To obtain a coating amount of 1,200 g / m ² (as a solution), and then wet-coagulate by immersing in water or a mixed solution of water and a solvent of polyurethane elastomer for solvent removal. By washing with water and drying, a sheet-like substance having a silver layer having vertical and uniform spindle-shaped pores on the substrate surface can be obtained. Furthermore, by grinding the silver surface of the sheet-like substance with a surface grinder using sandpaper, a suede-like shape with a uniform surface pore shape and a uniform cross-sectional pore shape perpendicular to the substrate surface. A polishing cloth is obtained.

(Effect of the invention) Since the suede-like polishing cloth of the present invention is excellent in hydrolysis resistance (alkali resistance) and chemical resistance, polishing by using it causes processing scratches (so-called scratches) on the object to be polished. It is less likely to occur, and a good polishing state is maintained for a long time, and it has excellent durability and stable polishing as compared with conventional products.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. Before that, the polishing test method and its evaluation method in the present example and comparative example will be described. Further, "parts" and "%" in Examples and Comparative Examples mean "parts by weight" and "% by weight" unless otherwise specified.

<Polishing Test I> 3% of colloidal silica having an average particle diameter of 0.01 μ is dispersed,
Further, a polishing liquid adjusted to pH 11 with sodium hydroxide was used, and the obtained polishing cloth was used to polish a 5-inch silicon wafer once at a polishing time of 30 minutes with a 36 SPAW polishing machine manufactured by Speedfam. . Polishing was repeated 60 times in total. The other polishing conditions were as follows.

Processing pressure 200 g / cm ² Surface plate rotation speed 77 rpm Processing temperature 40 ° C. Polishing liquid supply amount 100 cc / min <Polishing test II> 5% silicon oxide having an average particle size of 0.1 μ is dispersed and sodium hypochlorite is 1%. A 3-inch Ga.As wafer was polished with a 36 SPAW polishing machine manufactured by Speed Fam Co., using the resulting polishing cloth using the dissolved polishing liquid. 1
The polishing time was 30 minutes, and the polishing was repeated 60 times. Other polishing conditions were the same as those in the polishing test I.

<Polishing efficiency> The grinding depth (μ) in 30 minutes of polishing was measured.

<Defective occurrence> The ratio of wafers in which processing scratches (scratches) were visually confirmed under irradiation light of 50,000 lux was obtained and evaluated according to the following criteria.

◎ Less than 5% ○ 5-10% △ 10-50% × 50% or more (Examples 1 to 4, Comparative Examples 1 to 2) Needle punched with polyester short fibers (fineness 1.5d, length 51mm) Non-woven fabric (Basis weight 300g / m
² , thickness 2.0 m / m) was impregnated with an emulsion solution of a styrene-butadiene copolymer, and after heat-crosslinking reaction,
It was sliced to a thickness of 9 mm to obtain a substrate having a fiber ratio of 46% and a styrene-butadiene copolymer ratio of 54%.

Also, polyhexamethylene carbonate (PHMC) and polytetramethylene ether glycol (PTMG) each having a molecular weight of 2000 were used as a polyol component in a total molar ratio of 1 mol as shown in Table 1, and diphenylmethane-4,4 '. 3 mol of diisocyanate and 2 mol of ethylene glycol were solution polymerized in dimethylformamide to obtain a polyurethane elastomer solution having a concentration of 30%. To 100 parts of this polyurethane elastomer solution, 5 parts of carbon black powder, 3 parts of stearyl alcohol,
100 parts of dimethylformamide was added to obtain a silver surface polyurethane elastomer coating solution having a viscosity of 100 poise / 30 ° C. The obtained coating liquid is applied onto the above substrate with a roll coater.
After applying 00 g / m ² , it is immersed in a coagulation bath (water: dimethylformamide = 90: 10 weight ratio) at 30 ° C. for coagulation, sufficiently desolvated with warm water, and dried with hot air at 120 ° C. went.

Then, each surface was ground by 0.15 mm with # 120 sandpaper to obtain a suede-like polishing cloth. The results are shown in Table 1.

(Example 5) Instead of the polyol used in Examples 1 to 4, polyhexamethylene carbonate (PHMC) and polyhexamethylene adipate glycol (AD) were used in a molar ratio of 50: 5.
A suede-like polishing cloth was obtained in the same manner as in Examples 1 to 4 except that the suede-like polishing cloth was used. The results are shown in Table 1.

(Comparative Example 3) A was used as the polyol without using the PHMC used in Example 5.
A suede-like polishing cloth was obtained in the same manner as in Example 5, except that only D was used. The results are shown in Table 1.

Claims (1)

[Claims] 1. A method comprising applying a water-miscible organic solvent solution of a polyurethane elastomer to a substrate, treating it with an aqueous coagulating liquid to form a porous silver surface layer on the substrate, and grinding the surface of the silver surface layer. A suede-like polishing cloth comprising 30 mol% or more of polyhexamethylene carbonate as a polyol component of the polyurethane elastomer.