KR20040041835A - A silica grinding wheel - Google Patents

Abstract

PURPOSE: A silica grinding wheel is provided to be capable of manufacturing an abrasive made of colloidal silica alone without using a bond for minimizing the surface contamination and damage of a wafer. CONSTITUTION: An abrasive of a silica grinding wheel is made of silica. Preferably, the grinding wheel is manufactured by sintering the abrasive without bonding material. Preferably, the sintering is performed at the temperature of 850-950 °C. Preferably, the grain diameter of the abrasive is in the range of 300-1000 nm. Preferably, the wafer contamination and damage caused by using the bonding material is considerably reduced.

Description

A silica grinding wheel

With the rapid development of the information and communication field, research and development on silicon wafers, which are essential for the manufacture of various semiconductor equipments, are actively underway. The manufacturing process of semiconductor materials such as silicon wafers can be broadly divided into two stages, which are a crystal growing process and a processing process of silicon single-crystalline silicon and semiconductor materials. The semiconductor material processing process is basically sawing, lapping, etching, heat treatment, polishing; chemical mechanical polishing, commonly referred to as CMP process, Chemical Mechanical Polishing, cleaning Process), and may vary depending on the manufacturer. The sawing process (or slicing process) is a process in which silicon single crystals are cut to a certain thickness to produce a wafer, and the lapping process removes damage of the wafer surface generated during the sawing process. And the wafer thickness and flatness are uniform, and the etching process is the process of removing damage through chemical polishing, and the polishing process is the process of polishing the rough surface of the wafer to have high flatness. It is called CMP process because it uses mechanical method. 1 shows a manufacturing process diagram of a silicon wafer and a semiconductor material.

In general, the silicon wafer is very damaged on the surface during the sawing process, it is necessary to remove the silicon wafer. There are many differences in the method of removing damage, but in some cases, a fine grinding process and a grinding process using a grinding wheel are used. Conventional grinding wheels, which have been widely used in the related art, are composed of abrasive grains (or abrasive particles, abrasives), binders, and pores. The abrasive grains include diamond, alumina, silicon carbide, cubic boron nitride (CBN), and the like. In addition, the characteristics of the grinding wheel appear depending on the type of binder that maintains the shape of the grindstone by combining the abrasive grains. Table 1 shows the types and characteristics of the binders.

designation Main features Remarks Vitrified bonded wheel -Addition of solvent to clay and feldspar / high temperature (pottery nitriding)-Most commonly used binder-Difficult to make thin due to low elasticity V Silicate bond whetstone -Water glass (sodium silicate) / low temperature-easy to manufacture with large size (more than 1m in diameter)-difficult to make thin and unsuitable for heavy cutting S Resin bonded whetstone -Thermosetting resin (Bakelite, etc.) / Low temperature-Excellent elasticity and toughness, suitable for high speed use-Easy to make thin and suitable for heavy cutting-Cutting, offset wheel, etc. / Excellent autogenous action B Rubber bonded whetstone -Adding sulfur light to natural or artificial rubber / Low temperature-Cutting, centerless grinding wheel R Metal bonded wheel -Silver, copper, brass, nickel, iron, etc.-Applied to diamond, CBN whetstone, etc.-Strong bonding but no autogenous action. M

In addition, the bonding method includes a metal bond, a resin bond, a non-bonded bond, an electrodeposition method, and the like, and the characteristics thereof are described in Table 2 below.

Joining method Characteristic Metal bond -Long service life / Clogging concerns-Cutting of brittle materials such as cemented carbide, ceramics, glass and crystal Resin bond -Phenolic resin or polyamide type-Excellent grinding ability but low wear resistance-Polyamide type for grinding / heavy grinding of carbide tools, ceramics etc. Vitrified Bond -Intermediate properties of metal and resinoid-Polishing gem / sintered diamond such as ruby and sapphire Electrodeposition (plating) -Diamond grain electroplating on the surface-Easy to make cheap and complicated shapes, excellent grinding ability, short life-Small inner diameter, small quantity of various products, mold, jig polishing

Diamond grindstone is used for grinding, polishing and cutting a wide range of materials such as cemented carbide, glass, ferrite, semiconductor and ceramic. It is suitable for grinding cemented carbide, cemented carbide, etc. because it has high finishing surface roughness and excellent grinding. However, when polishing a silicon wafer with a resin bonded diamond whetstone, contamination from resins occurs. In addition, the use of other binders, such as metal bonds and bitifier bonds, is unavoidable. Therefore, in order to avoid contamination from the binder, it must be in the form of being bonded by abrasive grains itself. In the case of diamond, diamond particles cannot be bonded by a general method with a very covalent material. In addition, in the case of diamond abrasive grains, the wafer is damaged because the shape is very irregular.

At present, efforts have been made to minimize surface damage by using commercially available materials such as diamond as abrasive grains. However, the material has a stronger bonding force than semiconductor materials such as silicon, so that the surface damage is minimized to form a mirror surface. There is a limit.

Therefore, ceramics is a material that can replace the grinding wheels made of diamond and the above-mentioned bonds, among which abrasive grains and bonds made or made of cations such as silicon can prevent contamination from cations. In addition, since the physical properties of the original material formed on the surface of semiconductor materials such as silicon and oxides are similar, the surface damage can be minimized to form a mirror surface.

Therefore, an object of the present invention is to prepare abrasive grains from colloidal silica alone to provide silica grinding wheels without binder.

It is also an object of the present invention to provide a silicon wafer and a semiconductor material which minimize the surface damage without contamination by a binder by using the above-described grinding wheel.

1 shows a manufacturing process of a silicon wafer and a semiconductor material.

Figure 2 shows the particle size distribution of abrasive grains prepared from colloidal silica.

Figure 3 is a graph of the shrinkage of the silica grinding wheel according to the heat treatment temperature.

Figure 4 is a microstructure photograph of the silica grinding wheel heat treated for 1 hour at 1000 ℃.

5 is a microstructure photograph of a silica grinding wheel subjected to heat treatment at 900 ° C. for 1 hour.

6 is a photograph (b) using a surface photograph (a) and a magic mirror (mirror) of a wafer polished using a silica grinding wheel heat treated at 900 ° C. for 1 hour. The white part of Figs. 6A and 6B is the ground part.

7 is a schematic diagram of a magic mirror system.

The present invention relates to a silica grinding wheel comprising silica as abrasive grains, wherein the abrasive grains have a particle diameter of 300 nm to 1000 nm. If the grain size of the abrasive grain is less than 300 nm, the grinding ability is insignificant, and if it is 1000 nm or more, the abrasive grain is too large to damage the wafer.

In addition, the present invention is characterized in that the abrasive grains are manufactured as a grinding wheel through a heat treatment process, the heat treatment temperature is 850 ℃ ~ 950 ℃. If the heat treatment temperature is lower than 850 ° C, sintering of the silica particles does not occur, so there is no grinding ability, and if the heat treatment temperature is higher than 950 ° C, huge silica particles are formed to damage the wafer.

In addition, the present invention relates to a silica grinding wheel, which is produced only by abrasive grains without using a binder.

Hereinafter, the configuration of the present invention will be described in detail through specific examples. However, the scope of the present invention is not limited to the description of the following examples.

Example 1

A grinding wheel was prepared by filling silica mold with a metal mold having a diameter of 12 mm and molding the same, followed by heat treatment for 1 hour. At this time, the change of bower's axial rate according to heat treatment temperature was calculated by the following equation, and the change of bower's axial rate according to heat treatment temperature is shown in FIG.

Bow Axle (%) = (Shrinked Length / Initial Length) × 100

The silica grinding wheel heat-treated at each temperature was used to polish a 200 mm diameter silicon wafer after lapping. Grinding wheels heat-treated at 850 ℃ or lower had no grinding capacity with 3% or less bow. This is because sintering of the silica particles did not occur. In case of heat treatment above 950 ℃, the contraction rate is suddenly shrunk to 16% or more. This is because huge silica abrasive grains are formed. Damage the surface.

4 is a microstructure photograph when the heat treatment at 1000 ℃, it can be observed that sintering occurs to form a large particle. A microstructure photograph of the grinding wheel subjected to heat treatment at 900 ° C. for 1 hour is shown in FIG. 5. Bonding of abrasive grains occurs without the use of a binder, and formation of large particles such as at 1000 ° C. is not seen.

After grinding using a grinding wheel heat-treated at 900 ℃, the surface observed and photographed using a magic mirror (magic mirror, Hologenix, model YIS 200SP) is shown in FIG. The magic mirror method is useful for observing the surface shape of the mirror surface (i.e., polished surface) that occurs after the polishing process in the silicon wafer processing process. The surface of the sample which forms the mirror surface perpendicularly to the white light of the tungsten lamp It is a system to observe the reflected light incident on. At this time, the case where there is a shallow depth of curvature (curvature or waviness) over a large area on the reflected mirror surface or the case where there is an inclined curve (microflow) on a minute area is projected on the screen Observed as light and dark areas in the image. The bright portion is the concave portion of the wafer surface (ie, the portion where polishing takes place) and the dark portion becomes the relatively convex portion.

The white part of the surface photograph of FIG. 6A is the part which was grind | polished with the silica grinding wheel, and the white part of the photograph observed with the magic mirror of FIG. Therefore, in the case of manufacturing grinding grindstone from colloidal silica, it was most effective to use grindstone heat treated at 900 ℃ for 1 hour, and the contraction rate was about 8%. In the case of heat treatment), sintering does not occur, so that the bonding between the abrasive grains does not occur, and thus there is no polishing ability, and in the case of heat treatment at 950 ° C. or more, excessive bonding is performed to form large abrasive particles, thereby causing damage in the polishing process.

The present invention provides a silicon wafer and a semiconductor material which is free of abrasive grains and surface damage and which is free from contamination by a binder, which can prevent fine damage of the surface by diamond and contamination by a binder in precision grinding of the silicon wafer and semiconductor. Can be.

In addition, the present invention can reduce damage to the wafer by using a silica grinding wheel having a uniform shape.

Claims (4)

Silica grinding wheel using silica as abrasive grains. The silica grinding wheel according to claim 1, wherein the abrasive grains are manufactured into a grinding wheel by heat treatment without using a binder. The grinding wheel of silica according to claim 2, wherein the heat treatment temperature is 850 ° C to 950 ° C. The silica grinding wheel according to any one of claims 1 to 3, wherein the abrasive grains have a particle size of 300 nm to 1000 nm.