JPH09132661A - Production of foam for cmp pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a foam used for a CMP pad and having excellent water resistance and consequent durability by forming a mixture comprising a crosslinking agent, a heat-decomposable blowing agent and a polyolefin resin containing an abrasive into a sheet and crosslinking and foaming this sheet. SOLUTION: A crosslinking agent, a crosslinking aid (A), a heatdecomposable blowing agent (B), an abrasive (C) and a polyolefin resin (D) are melt-kneaded at the decomposition temperature of component B or below, and the resultant mixture is formed into a sheet, This sheet is crosslinked and foamed to form a foam for a CMP(chemical-mechanical polishing) pad. Examples of component D include polypropylene and polyethylene, An example of component A is tbutylcumyl peroxide. An example of component B is an organic type such as azodicarbonamide or an inorganic type such as sodium carbonate/citric acid mixture. The composition of a combination of component A with component B is desirably such that cell diameters of several tensμm or below can be realized. Component C used is desirably a finely divided silicon oxide abrasive, This foam has excellent water resistance as compared with a conventional urethane foam, so that it can give a CMP pad having durability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a foam for a CMP pad.

[0002]

2. Description of the Related Art Conventionally, a CMP pad is made of foamed polyurethane having a hollow portion having a diameter of several tens of μm (monthly publication, Semiconductor World May 1995, P3).
7). However, since polyurethane generally has poor water resistance, there is a problem in the durability of the pad.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a CMP pad having improved durability and excellent durability.

[0004]

Thus, according to the present invention, a polyolefin resin composition containing a cross-linking agent and / or a cross-linking aid, a pyrolytic foaming agent, and an abrasive is molded into a sheet, and the sheet is formed. CM obtained by cross-linking and foaming a molded article
A foam for a P-pad is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the polyolefin resin used in the present invention, resins such as polypropylene and polyethylene are used. As polypropylene, homopolypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, reactor-polyolefin thermoplastic elastomer (PER) [polypropylene component 5 to 45% by weight, ethylene / propylene copolymer Polymerization component 95-55% by weight
And polypropylene) are used. As polyethylene, polyethylene such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene is used, and further, a copolymer of ethylene and α-olefin or ethylene and other monomer such as vinyl acetate is used. A copolymer with ethyl acrylate or the like can also be used. In the present invention, these resins are
They can be used alone or as a mixture.

A cross-linking agent and / or a cross-linking auxiliary agent, a foaming agent, an abrasive, and various other additives may be added to these polyolefin resins in the present invention.

The crosslinking agent used in the present invention includes, for example,
t-butylcumyl peroxide, 2,5 dimethyl-
2,5 di (t-butylperoxy) hexane, 2,5 dimethyl-2,5 di (t-butylperoxy) hexyne-
3 and the like can be used, and the addition ratio is 0.2 to 5 parts by weight based on the total amount of the resin components. This percentage is
If the amount is less than 0.2 parts by weight, the crosslinking will be insufficient to obtain a uniform foam, and if it exceeds 5 parts by weight, the crosslinking density will be too high.
A good foam cannot be obtained due to cracks in the foam and coarsening of the cells.

Examples of the crosslinking aid include quinone dioxime, triallyl trimellilate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate and ethylene glycol methacrylate. The addition ratio of these cross-linking aids can be appropriately determined according to the desired degree of cross-linking and the like, but is usually in the range of 0.2 to 5 parts by weight with respect to 100 parts by weight of the total amount of the resin components.

The thermal decomposition type foaming agent used in the present invention is a compound which decomposes to generate a gas when heated, and examples thereof include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylene tetramine and toluene sulfonyl hydrazide. An organic compound or an inorganic compound such as a sodium carbonate / citric acid mixed system is used. Among these foaming agents, a foaming agent which gives a cell diameter of several tens of μm or less is particularly preferable. The addition amount of the thermal decomposition type foaming agent can be appropriately determined according to the desired expansion ratio, but is 2 to 50 parts by weight, preferably 5 to 40 parts by weight with respect to 100 parts by weight of the total amount of the resin components. Used within the range of.

The polishing material used in the present invention is a plasma CVD-SiO ₂ film or a CVD-TEO to be polished.
Thin film layers such as S (tetraethoxysilane) film and SOG (spin on glass) film (monthly Semiconductor World 199
(See the February issue, p. 76) as long as it can be polished according to the intended degree, it is not particularly limited, but is mainly composed of an abrasive composed of fine particles, for example, silicon oxide having a size of several μm to several tens of μm. Abraded material or the like can be used. The amount of the abrasive added to 100 parts by weight of resin is not particularly limited, but is generally 5 to 100 parts by weight, preferably 10 to 80 parts by weight.

In the present invention, if necessary, various additives such as antioxidants, ultraviolet absorbers, polymerization regulators,
A foam stabilizer, an antistatic agent, a pigment, a filler and the like can be added.

As a method for mixing the above materials, a polyolefin resin, a cross-linking agent and / or a cross-linking auxiliary agent, a foaming agent, an abrasive, and various desired additives are added at a decomposition temperature of the cross-linking agent or a decomposition temperature of the foaming agent. In the following, it is melt-kneaded using a Banbury mixer, a roll, an extruder (single axis, multi-axis), etc., and finally formed into a sheet through a press, a die and the like.

The gel fraction of the obtained crosslinked foam is
It is preferable to adjust the amount of additives such as a cross-linking agent and a cross-linking auxiliary agent so as to be 20 to 80%. If the gel fraction is too small, heat resistance cannot be obtained. On the contrary, if the gel fraction is too large, the elongation is lowered and the external appearance such as ear cracks and blister is deteriorated, which is not preferable. Further, in the present invention, it is possible to perform crosslinking of the crosslinked polyolefin resin using radiation such as electron beam,
In this case, the above-mentioned crosslinking aid can be used. The irradiation dose of the electron beam is not particularly limited as long as the gel ratio of the resin crosslinked portion is 20 to 80%, but is generally 1 to 20 Mrad.
Irradiation, preferably 2 to 10 Mrad.

The foam according to the present invention comprises a polyolefin resin foam obtained by crosslinking and foaming a polyolefin resin composition containing a cross-linking agent and / or a cross-linking aid and a thermal decomposition type foaming agent. It is possible to provide a CMP foam which is excellent in durability and, by extension, has durability.

[0015]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 7% by weight of ethylene component, melt flow rate (ME
R: 230 ° C.) is 3 g / 10 minutes, and the ethylene / propylene random copolymer having a melting point of 138 ° C. is 100 parts by weight,
5 parts by weight of azodicarbonamide as a foaming agent, 1 part by weight of trimethylolpropane triacrylate as a crosslinking aid, and Irganox 1010 as an antioxidant of 0.
Aerosil with 5 parts by weight and a particle size of 5-20 μm as an abrasive
(Nippon Aerosil Co., Ltd.) 20 parts by weight were compounded and kneaded at once at 155 ° C. using an LCM kneading machine to prepare pellets having an outer diameter of about 6 mm. Incidentally, the extrusion rate was 65 kg / h. Next, the pellets obtained by the method were put into a hopper of a single-screw extruder having a screw diameter of 65 mm, and a sheet having a thickness of about 1 mm and having good resin and foaming agent dispersibility was formed using a sheet die (molding). The conditions are as follows). Screw: Compression ratio: 3.0 L / D: 26 Screw rotation speed: 45 rpm Cylinder temperature: C1 / C2 / C3 / C4; 150/155/155/155 ° C Adapter temperature: AD; 155 ° C Die temperature: D; 155 C. Next, the sheet 2Mrad obtained by the above method was subjected to electron beam irradiation and then placed in an oven at 230.degree. C. and heated. As a result, a foam having a foaming ratio of about 10 times and a good appearance with no blisters was obtained. .

Example 2 Ethylene component 7% by weight, melt flow rate (ME
R: 230 ° C.) 3 g / 10 min, melting point 138 ° C. ethylene / propylene random copolymer 80 parts by weight, and low-density polyethylene / high-density polyethylene mixed weight ratio 70/30 polyethylene 30 parts by weight 7 parts by weight of azodicarbonamide as a foaming agent, 1 part by weight of trimethylolpropane triacrylate as a crosslinking aid, 0.5 parts by weight of Irganox 1010 as an antioxidant, and a particle size of 5 as an abrasive. ~ 20
After mixing 20 µ parts by weight of Aerosil (manufactured by Nippon Aerosil Co., Ltd.) and kneading them together at 155 ° C using an LCM kneading device, pellets having an outer diameter of about 6 mm were prepared. Incidentally, the extrusion rate was 70 kg / h. Next, the pellets obtained by the method were put into a hopper of a single-screw extruder having a screw diameter of 65 mm, and a sheet having a thickness of about 0.8 mm and good dispersibility of a resin and a foaming agent was formed using a sheet die. (Molding conditions are as follows). Screw: Compression ratio: 3.0 L / D: 26 Screw rotation speed: 45 rpm Cylinder temperature: C1 / C2 / C3 / C4; 145/150/150/150 ° C Adapter temperature: AD; 150 ° C Die temperature: D; 150 C. Next, the sheet 2Mrad obtained by the above method was subjected to electron beam irradiation and then placed in an oven at 230.degree. C. and heated. As a result, a foam having a foaming ratio of about 10 times and a good appearance with no blisters was obtained. .

[0018]

EFFECTS OF THE INVENTION According to the present invention, water resistance is excellent as compared with conventional foams for CMP pads made of urethane foam.
As a result, a CMP pad having excellent durability can be provided.

Claims (3)

[Claims] 1. A CMP obtained by molding a polyolefin resin composition containing a cross-linking agent and / or a cross-linking aid, a thermal decomposition type foaming agent, and an abrasive into a sheet, and cross-linking and foaming the sheet-shaped molded article. Chemical Mechanical Polishing) A method for producing a foam for a pad. 2. The method for producing a foam for a CMP pad according to claim 1, wherein the polyolefin resin is polypropylene or polyethylene. 3. The method for producing a foam for a CMP pad according to claim 1, wherein the polishing material is silica.