JPH01177969A - Fine grinding compound for wafer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to polishing for smoothing irregularities larger than 10!0μ on the surface of wafers that are widely used as supporting crystals for electrical integrated circuits. The present invention relates to a polishing composition suitable for fine polishing.

``Prior Art'' Wafers, which are widely used as supporting crystals for electrical integrated circuits, are usually sliced from ingots of silicon or germanium crystals and their surfaces polished to form as flat a surface as possible. Later, it was used to form a circuit.

This is because when drawing a circuit pattern on the wafer surface, if the surface is uneven, it becomes difficult to draw the line precisely and precisely, and it also causes non-uniformity in the electrical characteristics of the wafer. .

Various abrasives have been proposed to polish the surface of such wafers.

For example, U.S. Patent No. 3.170. ．． Specification No. 273,
discloses silica sol having a silica concentration of 2 to 50% and silica gel having a silica concentration of 2 to 100% as abrasives, and US Pat. No. 3,328°141 discloses that alkaline compounds are added to these abrasives. is added to adjust the pH to 10.5 to 12.5, and it is disclosed that the polishing rate increases when this is used. However, when the surface of a wafer polished with these abrasives is observed using a differential interference microscope or the like, there are irregularities of 5 to 5001 microns, which is not completely satisfactory.

In addition, Japanese Patent Publication No. 53-9910 discloses that it contains quartz, silicate, hexafluorosilicate, and further contains 3 to 3 C atoms.
An abrasive containing a monohydric alcohol and polyvinyl alcohol having 5 atoms has been disclosed, but even when such an abrasive is used, a sufficiently satisfactory polished surface has not yet been obtained. This abrasive has the disadvantage that it is difficult to store it stably for a long period of time.

Further, Japanese Patent Publication No. 14655/1983 discloses a polishing agent containing water-soluble carboxypolymethylene rubber or xanthan gum, but the polishing time required to form a smooth polished surface and the polishing time after polishing are There was a drawback that so-called dry polishing had to be carried out for a long time while running water for cleaning. Another disadvantage is that microorganisms that use xanthan gum as a nutrient source are generated during polishing, making it difficult to store it stably for a long period of time.

E: Problems to be Solved by the Present Invention The present invention uses an abrasive that provides a polished surface with no irregularities even when observed with a differential interference microscope when a wafer is polished, that is, it finely polishes the surface of the wafer. The object of the present invention is to provide a fine polishing composition suitable for polishing and having excellent long-term storage stability.

[Means for Solving the Problems] The gist of the present invention is to contain a polysaccharide polymer compound obtained by graft polymerization of water, granular amorphous silica, and acrylamide, and to adjust the pH to 51 to 8 to 12 with an alkaline compound. The present invention will be described in detail below.

The granular amorphous silica used in the present invention includes colloidal silica or silica powder, which can be used in the form of fleugle silica sol, an aqueous slurry in which silica powder is suspended in water, or , used in such a form that it can form an aqueous slurry when added to water. The silica concentration in the slurry when it is made into an aqueous slurry is usually preferably 1 to 5 times the weight.

Therefore, the granular amorphous silica described in item (h) is usually used having an average particle size larger than 5 mμ and smaller than 10 μm. If the average particle size is less than 5 μm, the proportion of silicic acid monomers and oligomers contained in the particles will increase, and polishing with a material containing a large amount of these will cause silica to adhere to the wafer surface, which is undesirable. If the thickness is less than micron, scratches may easily occur on the wafer surface, which is not preferable. In addition, in the present invention, the average particle size means the average particle size of particles in an isolated state without agglomeration, and when the particles exist in an agglomerated state, it means the average particle diameter of the particles in that state. means the average particle size of the aggregated particles in that state.

Further, the content of the granular 7 mol 7 gamma streak silica in the composition for fine polishing of wafers according to the present invention is usually set at a ratio of 0.1% by weight or more, since the effect is not sufficient if it is too small.

In the present invention, examples of the polysaccharide polymer compound include guar gum and xanthan gum.

Guar gum refers to lactomannan, a mucilaginous substance contained in the endosperm of the seeds of guar, a plant belonging to the leguminous family. do.

The composition for fine polishing of wafers according to the present invention contains a polysaccharide polymer compound obtained by graft polymerization of acrylamide to the above polysaccharide polymer compound.

Therefore, compared to a polysaccharide polymer compound in which acrylamide is graft-polymerized, the drug ligoxitan effect of its aqueous solution is enhanced, and biochemical decomposition by microorganisms is enhanced. It has high resistance to.

The drug rig oxidation effect is an effect that makes it difficult for turbulence to occur even under conditions where the Reynolds number of the fluid is high. This means that even during polishing, the polishing composition maintains a laminar flow and is less likely to become turbulent.

A method for graft polymerizing acrylamide onto a polysaccharide polymer compound is described in Tsunaru Op Applied Polymer Science vol. 130.4013-4018 (198
5> and the same, vo132.6163-6176 (19
The method detailed in 8G) may be used.

For example, when graft polymerizing acryl 7mide to guar gum or xanthan gum, add 1 mmol to 1 mol of acrylamide and a polymerization initiator per 1 g of guar gum or xanthan gum to an aqueous solution containing 0.01 to 2.0% by weight of guar gum or xanthan gum. It may be added in a proportion of 1 micromol to 10 mmol and allowed to react at a temperature of 0 to 100°C in air or in the presence of an inert gas.

As the polymerization initiator, it is preferable to use a cerium ion radical, and it is preferable that the guar gum or xanthan gum has as high a purity as possible.

The content of the polysaccharide polymer compound graft-polymerized with acrylamide in the composition for fine polishing of wafers according to the present invention is usually applied at 1 ppm or more, particularly preferably from 10 ppm to 1000 ppm. When polishing a wafer using a polishing composition with a content within these ranges, a clean laminar flow is formed in the sliding direction between the polishing cloth and the wafer surface, making the wafer surface even smoother. However, if the content is less than IPI), it is difficult to form the laminar flow, and if it exceeds 1000 pp+s, turbulent flow may be formed, which is not preferable.

The fine polishing composition for wafers according to the present invention has a pH of 8 to 12, preferably 9 to 12, depending on the alkaline compound.
10 to keep the silica sol stable.

As the alkaline compound, alkali metals, amines or ammonia can be used, but it is particularly preferred to use highly basic amines such as dimethylamine.

"Effects of the Invention" The present invention has the following particularly remarkable effects, and therefore has extremely great industrial utility value.

(1) When polishing a wafer using the fine polishing composition according to the present invention, the polysaccharide polymer compound in which acrylamide is graft-polymerized in the slurry composition enhances the drug ligoxitan effect, and A laminar flow is formed between the wafer and the wafer, suppressing the occurrence of turbulent flow. Therefore,
The surface of the polished wafer is a smooth polished surface with no unevenness observed even when observed with a differential interference microscope.

(2) The polysaccharide polymer compound graft-polymerized with acrylamide in the fine polishing composition according to the present invention is
Since it has high resistance to biochemical decomposition by microorganisms, it can be stored stably for a long period of time as an effective abrasive.

"Examples" Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 (1) Production of guar gum grafted with acrylamide High molecular weight guar gum (manufactured by Sanshin Co., Ltd., trade name Mayprodol 120) was dissolved in water to prepare a 0.5% aqueous solution.

This was purified by filtration and alcohol elution. This purification method was carried out as follows. First, the pore size was 1.
Coarse impurities in the guar gum aqueous solution were removed by filtration using a ~10μ mesh filter. Since guar gum is not soluble in alcohol, the guar gum aqueous solution was poured into alcohol, the alcohol eluate was eluted, and the precipitate was collected.

This precipitate was dried and then dissolved in water again to obtain a guar gum aqueous solution of a predetermined concentration, in this example 1% by weight.

Add 0.5 mol of acrylamide to the obtained 1% by weight aqueous solution 11, stir while bubbling nitrogen, add 0.3 mmol of cerium 7-quinium nitrate as a polymerization initiator, and further stir, The reaction was carried out at room temperature for 24 hours to obtain guar gum grafted with acrylamide.

The graft reaction can also be carried out by adding an excess of about 10 mmol of the polymerization initiator liquid and reacting in an air atmosphere.
The reaction can also be carried out by stirring for about 1 hour and then leaving it to stand.

(2) Preparation of polishing composition A 1% aqueous solution of guar gum grafted with acrylamide obtained by the method described in (1) above was mixed with 200 ppTa in terms of guar gum, an average particle size of 70 millimicrons, and silica. was added to an aqueous solution of colloidal silica containing 2% by weight. 0.6% by weight of dimethylamine was added to the resulting aqueous solution.
Add DH to between 9 and 10 ii! l! 1. A composition for fine polishing of wafers was obtained.

(3) Storage period storage test of polishing composition” - Store the polishing composition obtained in (2) at room temperature,
Periodically, this composition was flowed through a rod-shaped capillary with a hole diameter of 0,5 m+++S and 50 cm at a pressure of 4 kg/c2, and the pressure was measured at the inlet and outlet of the capillary.
We observed the time when the pressure drop was 414 or more compared to water.

The results are shown in table tItJ1.

(4) Wafer fine polishing test Using Speed 77M Polishing 8!5 PAW36 and a soft suede type polishing cloth, the silicon wafer was polished while supplying the above polishing composition at a rate of 11 per minute. Polished. The polishing pressure at this time is 100kg/c
m”, the relative speed of the wafer and polishing cloth is 1 m/see
The temperature of the polishing cloth during polishing was 40°C.

The time required for the wafer to reach the top surface by polishing with a polishing machine was measured (to check whether the wafer was smooth or not, use a differential interference microscope during polishing). The results are shown in Table 1.

Ken! After polishing with the M machine, rinsing was performed while running water instead of the polishing composition described above to remove silica and polysaccharide polymers on the wafer surface. The time required for rinsing polishing (the time point at which rinsing polishing was completed was determined by observing the wafer surface with a differential interference microscope) was measured. .

The results are shown in Table 1.

Example 2 (1) Xanthan gum grafted with acrylamide! ! Xanthan gum (manufactured by Sanshin Co., Ltd., trade name: Kelzan F), a synthetic polymer, was dissolved in water to form a 0.5% aqueous solution.

This was purified in the same manner as described in Example 1 (1), and acrylamide was grafted in the same manner to produce acrylamide-grafted xanthan gum.

(2) Preparation of polishing composition A 1% aqueous solution of xanthan gum grafted with acrylamide obtained in (1) above was added to
00 ppm and an average particle size of 70 millimicrons was added to an aqueous solution of colloidal silica containing 2% by weight of silica. 0.6% by weight of trimethylamine was added to the resulting aqueous solution to prepare a pt-i between 9 and 10 to obtain a composition for fine polishing of wafers.

(3) Long-term storage test of polishing composition Evaluation was performed using the same procedure as in Example 1 (3).

The results are shown in Table 1.

(4) Wafer fine polishing test The test was carried out in the same manner as in Example 1 (4).

The results are shown in Table 1.

Comparative Example 1 (1) Fixation of polishing composition In the example described in Example 1 (2), guar gum purified by the method described in (1) on the same side (Mishima) was used instead of the guar gum grafted with acrylamide. A polishing composition was prepared in the same manner as on the same side, except that Mayprodol 120 (manufactured by Co., Ltd.) was used.

(2) Long-term storage test of polishing composition Evaluation was performed using the same procedure as in Example 1 (3).

The results are shown in Table 1.

(3) Wafer fine polishing test Evaluation was performed using the same procedure as in Example 1 (4).

The results are shown in Table 1.

Comparative Example 2 (1) Preparation of polishing composition In the example described in Example 2 (2), 1 xanthan gum grafted with acrylamide was replaced with 1 xanthan gum on the same side (1
) xanthan gum (Mishima Co., Ltd.) purified by the method described in
A polishing composition was prepared in the same manner as on the same side, except that KELZAN F) (manufactured by Co., Ltd.) was used.

(2) Long-term storage test of polishing composition Evaluation was performed using the same procedure as in Example 1 (3).

The results are shown in Table 1.

(3) Wafer 71-in polishing test Evaluation was performed using the same procedure as in Example 1 (4).

The results are shown in Table 1.

Table 1 From the fjS1 table, the following becomes clear.

1. The polishing composition according to the present invention does not lose its drug effect even after long-term storage, and has excellent storage stability.

2. When polishing with the polishing composition according to the present invention, the fine polishing time is short and the rinsing polishing time is also short, making it suitable as a polishing agent.

3. On the other hand, the polishing composition of the comparative example does not lose its drag-grip effect even after being stored for a short period of time, and has poor storage stability.

4. When polishing with the polishing composition of the comparative example, both the fine polishing time and the rinse polishing time are longer than those of the example.

Applicant: Mitsubishi Monsanto Chemicals Co., Ltd.

Claims (5)

[Claims] (1) Contains a polysaccharide polymer compound obtained by graft polymerization of water, granular amorphous silica, and acrylamide,
A composition for fine polishing of wafers, the composition being adjusted to pH 8 to 12 with an alkaline substance. (2) The composition for fine polishing of wafers according to claim (1), wherein the average particle size of the granular amorphous silica is in the range of 5 mm to 10 microns. (3) A patent claim characterized in that the content of granular amorphous silica is 0.1% by weight or more, and the content of a polysaccharide polymer compound obtained by graft polymerization of acrylamide is 1 ppm or more. A composition for fine polishing of wafers according to range (1). (4) The composition for fine polishing of wafers according to claim (1), wherein the polysaccharide polymer compound is one or more types selected from water-soluble guar gum and xanthan gum. (5) Claims characterized in that the alkaline compound is an alkali metal, amines, or ammonia (
The composition for fine polishing of wafers according to item 1).