JPS6012191B2 - Polishing element for mirror finishing of silicon semiconductor and mirror finishing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polishing element used for mirror finishing a silicon semiconductor and a method for mirror finishing a silicon semiconductor using the polishing element.

The currently widely used polishing process for silicon semiconductors (wafers) involves cutting silicon single crystals or polycrystals and then lapping (sanding) them with an abrasive slurry of dew-molten alumina, silicon carbide, etc. with a grain size of approximately 10 μm. This is then carried out by mirror polishing with a slurry containing fine powder such as silica.

This mirror polishing process is performed in two or three stages. In the sanding process, a lap plate such as a cast iron plate is used, and in the mirror polishing process, a so-called polishing cloth made of polyurethane fiber or the like is attached to the lap plate.

The silicon semiconductor wafer obtained by these polishing processes is required to have high planar accuracy, fine surface roughness, and little processing distortion.

Therefore, especially in the mirror polishing process, it is extremely difficult for coarse particles of the abrasive material or foreign matter, such as dust from the outside or chipping of the workpiece, to get mixed into the abrasive slurry, and the abrasive slurry is circulated. I can't use it, so I have no choice but to use it continuously. Therefore, the processing cost is higher than in the mirror polishing process for glasses and metals, which normally uses an abrasive slurry in circulation, and a large amount of abrasive liquid is generated.

Furthermore, the polishing performance of the polishing cloth used in the mirror polishing process changes depending on the degree of fluff, so it is required to be replaced quite frequently.

Generally, in the polishing process using an abrasive slurry, there are problems such as repositioning of the surface plate and disposal of slurry waste, so polishing using an abrasive molded body instead of the slurry has also been proposed. For example, for mirror finishing of glass, Z2
, Ce02, and Fe203 are used as a polishing tool made of a molded porous unsaturated polyester resin. (
(Japanese Unexamined Patent Publication No. 52-79398) However, for materials such as silicon semiconductors, which require a higher degree of surface processing precision than glass, it has been considered difficult to achieve a mirror finish using an abrasive molded body, and this has not been achieved. In fact, for example CeQ,
It has been found that when Zr02 and Fe203 characteristic particles are fixed with a resin, processing distortion of the silicon semiconductor wafer is extremely large no matter what resin is used.

Further, even if amorphous silica fine powder used in the case of slurry was used and dispersed in a resin by a conventional method, a highly accurate mirror-polished surface could not be obtained.

The present invention was arrived at as a result of intensive research under these circumstances, and involves dispersing amorphous silica fine powder in a porous unsaturated polyester resin, and determining the amount of dispersion and pore size to porosity. This made it possible for the first time to achieve a mirror finish on a silicon semiconductor using a polished molded body.

The present invention will be explained in detail below. First, there is the amorphous silica fine powder, which is called "white carbon," but its primary particles are very fine, with a size of 0.05 mm or less.

This is dispersed and contained in the molded article of the present invention. There are other types such as pulverized fused silica. The amount of dispersion needs to be 30 to 7% by weight for mirror finishing of silicon semiconductors. If it is less than 30%, the polishing speed is too low to be practical, and if it exceeds 70%, the surface of the workpiece is likely to be damaged due to the abrasive particles falling off, which is both undesirable.
The resins used are limited to unsaturated polyesters, such as t-polyvinyl alcohol resins and phenol resins, but even if they are made porous, the same effects as the present invention cannot be obtained. Unsaturated polyester resin contains maleic acid,
An unsaturated polyester obtained by reacting an unsaturated dibasic acid such as fumaric acid with a dihydric alcohol such as ethylene glycol and diethylene glycol is dissolved in a vinyl monomer such as styrene, vinyl acetate, or methyl methacrylate. Before hardening, it is a sticky oily liquid and is insoluble in water. In the present invention, this resin is cured into a porous molded body under the conditions described below. In general, the role of pores in an abrasive compact is extremely important, and the preferred pore distribution varies depending on the type of binder (resin) used, abrasive particles, material to be polished, etc., and these factors are related to each other.
It is difficult to predict it.

In the mirror finishing of silicon semiconductors using unsaturated polyester resin as a binder and amorphous silica fine powder as an abrasive, the molded body has a porosity of 35 to 65% and a pore diameter of 0.

It is necessary to ensure that the majority (approximately 80% or more) is in the range of 1 to 10 French in order to improve the precision of mirror finishing of silicon semiconductors and to improve the polishing efficiency.

If the porosity is less than 35%, the polishing speed will be low and it is not practical.

Moreover, if it exceeds 65%, not only the polishing speed becomes low but also the finishing accuracy deteriorates. Furthermore, if the pores are too large, the polishing speed will be low; if the pores are too low, the wear of the polishing element will increase, which is undesirable.

The polishing element having the above configuration can be made into various shapes such as a cylindrical shape, and when polishing silicon semiconductors, one or more polishing elements can be fixed at one end to a surface plate and polished at the other end. do.

In particular, when a plurality of pieces are fixed to a surface plate at intervals, "When polishing is performed, the waste generated during polishing is discharged from between the intervals and does not intervene on the surface to be polished, so that extremely good polishing can be achieved. In the polishing element of the present invention, a water-in-oil emulsion in which water is dispersed as fine droplets in the resin is made from the above-mentioned liquid unsaturated polyester resin and water, and fine silica powder is introduced into the emulsion. It can be made by uniformly dispersing it, dehydrating it, and curing it.

The porosity can be controlled by the amount of water, and the diameter of the pores can be controlled by, for example, the composition of the unsaturated polyester resin, curing conditions, etc. Next, we will describe a mirror polishing method for silicon semiconductors using this polishing element.

Using the polishing element of the present invention, it is possible to mirror-polish a silicon semiconductor after sand-sand polishing while pouring water or the like.

Preferably in this case an aqueous solution of the basic substance is used. Examples of base substances include hydroxides of Na, K, Ca, etc., carbonates of Na and K, ammonia, primary and secondary aliphatic and aromatic amines, etc. The mirror polishing mechanism of silicon is generally mechanochemical. It is believed that gel-like substances such as oxides or hydroxides generated on the silicon surface are mechanically removed using amorphous silica.

The rate of formation of a gel-like substance is accelerated by the presence of a basic substance. Example: To 10M of an unsaturated polyester resin (condensation product of maleic anhydride and diethylene glycol) containing 30% styrene, 1 part of cobalt octoate as a hardening accelerator and 3 parts of triethylamine as a hair thinning agent were added, and the mixture was heated with a candle. While worshiping,
When 200 ml of water is gradually added dropwise, a white water-in-oil emulsion with high viscosity is obtained.

To this, amorphous silica fine powder (manufactured by Philadelphia Quartz Co., Ltd., trade name Q-G-3, ultimate particle size 0.02 m),
Agglomerated particle size: 0.5 A) 150 ml of agglomerated particles were added, and the mixture was slowly heated to wet the surface of the fine powder. Next, 2 ml of methyl ethyl ketone peroxide, which is a hardening agent, was added and stirred.

The resulting mixture is placed in a mold and left to harden at room temperature for 8 hours. It was removed from the mold and dried at 110 oo for 8 hours to complete curing and at the same time remove the moisture contained. The obtained molded body was a disc with a diameter of 13 skins and a length of 3 skins, and the porosity was 54%.
, the pore distribution was mostly in the range of 0.1 to 10 μm. One end of this molded body was attached to the surface of a surface plate with a diameter of 3 mm and a diameter of 10 mm. The ratio of the gluing area of the molded body to the area of the surface plate was about 50%. Using this polishing tool, a silicon semiconductor wafer that had been sand-polished was polished for 60 minutes. Polishing was performed while pouring an aqueous solution of ethylamine from PHil. When the surface of the wafer after polishing was observed under a microscope, the scratch rate was lower than when polishing slurry was used.

Claims (1)

[Scope of Claims] 1. A porous unsaturated polyester resin molded body containing 30 to 70% of amorphous silica fine powder dispersed therein, the molded body having a porosity of 35% to 65% and a majority of pore diameters of 0.5%. 5μ～10μ
A polishing element for mirror finishing a silicon semiconductor, characterized by comprising: 2 A porous unsaturated polyester resin molded body containing 30 to 70% of amorphous silica fine powder dispersed therein, the molded body having a porosity of 35% to 65% and a majority of pore diameters of 0.1 μ to 10 μ.
A mirror finishing method characterized by mirror polishing a silicon semiconductor while pouring an aqueous solution of a basic substance using a polishing element consisting of.