JP2002011652A - Polishing pad and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad having hydrophilic nature and durability and used in a CMP improved in maintenance of polishing slurry on a pad surface. SOLUTION: A sheet formed of hydrophilic fibers is caused to carry 20-90 wt.% hydrophilic high molecules.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing pad, and more particularly, to a precision polishing of a semiconductor wafer, a memory disk, a liquid crystal glass, an optical component lens, etc. (hereinafter, referred to as a "semiconductor wafer, etc."). It relates to a polishing pad.

[0002]

2. Description of the Related Art Conventionally, as one of the techniques for precision flattening of a semiconductor wafer or the like, CMP (chemical mechanic) has been used.
al polishing). The CMP polishing method is a method in which a polishing pad and a workpiece are rotationally driven, and polishing is performed while supplying a polishing slurry of pH-adjusted water-dispersed silica, alumina, ceria, or the like.

[0003] Examples of the polishing pad used in the CMP include a pad mainly composed of a synthetic polymer molded article and a pad mainly composed of a nonwoven fabric.

As the former pad mainly composed of a synthetic polymer molded article, a rigid polyurethane foam disclosed in JP-A-64-58475 and JP-A-9-1326 are disclosed.
No. 61, a polyolefin resin foam, and an epoxy resin molded product disclosed in JP-A-11-138241.

[0005] Further, as the latter pad using a nonwoven fabric as a base material, Japanese Patent Application Laid-Open Nos.
And non-woven fabrics impregnated with a synthetic resin disclosed in JP-A-99479 and heat-fused fibers disclosed in JP-A-11-90809.

[0006]

However, since each pad mainly composed of the above-mentioned synthetic polymer molded body is mainly composed of a non-hydrophilic material, a material having good wettability and water retention is not considered. However, it is disadvantageous for holding the polishing slurry on the pad surface. That is, since the surface is hydrophobic, the polishing slurry is not uniformly held on the pad surface, which adversely affects the polishing accuracy.

[0007] In order to obtain a sufficient polishing efficiency, the respective pads made of the latter non-woven fabric as a base material need to have a hard surface, and have the necessary strength and durability as a polishing pad. Sufficient processing such as impregnation with a resin such as urethane or heat fusion with a thermoplastic resin is required to provide the adhesive. When these conditions are satisfied, the pad surface becomes hydrophobic, and the water retention becomes insufficient.

On the other hand, in order to make the pad surface hydrophilic, it is conceivable to use a pad mainly composed of cellulose fibers as disclosed in Japanese Patent Application Laid-Open No. 57-173465. However, when a shear force is applied to the pad in a water-containing state, the fibers are likely to be detached from the surface, so that the pad has insufficient durability for use in CMP polishing.

In order to hold the polishing slurry on the pad surface, it is conceivable to form holes or grooves on the pad surface. However, in the polishing step, polishing debris and agglomerates of the abrasive tend to enter the pores and grooves and accumulate. If so, clogging is likely to occur. When clogging occurs, the polishing slurry becomes difficult to be held, sharply lowers the polishing efficiency, deteriorates the flatness and uniformity of the processed product, and easily causes scratches.

Accordingly, the present invention provides a C powder having hydrophilicity and durability, and improved polishing slurry retention on the pad surface.
An object is to provide a polishing pad used in MP.

[0011]

The present invention has solved the above-mentioned problems by supporting a hydrophilic polymer in a sheet composed of hydrophilic fibers at 20 to 90% by weight.

Since the hydrophilic polymer is supported on the hydrophilic fiber, the detachment of the fiber is suppressed, and the durability is improved. Also,
Since the hydrophilic material is used, the pad surface is easily wetted and the polishing slurry is easily held.

[0013]

Embodiments of the present invention will be described below.

The polishing pad according to the present invention is obtained by supporting a hydrophilic polymer on a sheet composed of hydrophilic fibers.

The above-mentioned hydrophilic fiber has a hydrophilic group in a molecule constituting the fiber, and the fiber itself has hydrophilicity. Examples thereof include vegetable fibers such as cotton and hemp, animal hair fibers such as wool and goat hair, regenerated cellulose fibers such as rayon and cupra, and synthetic fibers such as polyvinyl alcohol. A sheet is formed from one or more of these hydrophilic fibers, and is used as a base material for a polishing pad.

The degree of hydrophilicity in the hydrophilic fiber is as follows:
Although it varies depending on the relative amount of the hydrophilic group, etc., it greatly affects the hygroscopicity and equilibrium moisture of the fiber. Therefore, in order to know the degree of hydrophilicity of the fiber, the moisture content under a predetermined environmental condition is one index. The preferable degree of hydrophilicity of the hydrophilic fiber is preferably 6% or more, more preferably 10% or more, when evaluated by equilibrium moisture at 20 ° C. and 65% RH. If it is less than 6%, the hydrophilicity of the polishing pad may not be sufficiently exhibited.

As a sheet composed of more preferable hydrophilic fibers having the above-mentioned equilibrium moisture, there is a pulp sheet which is an aggregate of cellulose fibers.

The raw material of the pulp, which is the raw material of the pulp sheet, is not particularly limited.
Any of wood pulp such as conifers, pulp fiber pulp such as manila hemp, mulberry, mitsumata, cotton pulp, rayon pulp and the like can be suitably used.

The above hydrophilic polymer is used as a polishing pad,
It is necessary to have a hydrophilic property to hold the aqueous polishing slurry and to be insoluble in water because it is exposed to the aqueous polishing slurry. Examples of such a hydrophilic polymer include those obtained by insolubilizing a water-soluble polymer by chemical crosslinking. Specific examples include those obtained by insolubilizing synthetic polymers such as polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyethylene glycol, polyvinyl ether, and polyethylene imine by chemical crosslinking, and regenerated cellulose.

The degree of hydrophilicity of these hydrophilic polymers is as follows:
If the material alone can be formed into a plate shape, it can be evaluated by the contact angle of water. When evaluating the hydrophilicity of the hydrophilic polymer by the contact angle of water, the contact angle is preferably 20 ° or less, more preferably 15 ° or less. If the angle is larger than 20 °, the hydrophilic property of the sheet composed of the hydrophilic fibers as the base material may be impaired.

A more preferred hydrophilic polymer having the above-mentioned contact angle is regenerated cellulose which is particularly excellent in hydrophilicity. The regenerated cellulose is obtained by dissolving cellulose with a specific solvent to obtain a cellulose solution, which is coagulated and regenerated. The source of the raw material cellulose is not particularly limited, and examples thereof include wood, cotton, hemp, and the like. Here, examples of the cellulose solution include cellulose itself and a solution dissolved as a cellulose derivative. Specifically, first, formaldehyde-dimethylsulfoxide-based, lithium chloride-
Dimethylacetamide, N-methylmorpholine-N-
Examples thereof include a solution in which cellulose such as an oxide is directly dissolved in a solvent. Examples of cellulose derivatives such as cellulose esters such as cellulose nitrate and cellulose acetate and cellulose ethers such as carboxymethylcellulose and methylcellulose include those dissolved in a solvent such as water. Further, alkali-type cellulose solutions such as viscose, cellulose copper ammonia solution, cellulose carbamate solution and the like can be mentioned. Among these, viscose, particularly viscose for cellophane production, is preferred.

When viscose is used as the alkali type cellulose solution, the concentration of the cellulose component contained in the viscose is preferably 3 to 15% by weight, and more preferably 4 to 10% by weight. If the amount is less than 3% by weight, the mechanical strength of the regenerated cellulose is low, and the durability of the polishing pad may be insufficient. If it is higher than 15% by weight,
Despite the entanglement with the degree of polymerization, the viscosity is extremely high and handling tends to be difficult.

The alkali concentration in the viscose is preferably 2 to 15% by weight in terms of sodium hydroxide.
~ 13% by weight is preferred. Further, the ammonium chloride value in the viscose is preferably 3 to 12, and more preferably 4 to 9.

As a method for supporting the hydrophilic polymer on the sheet made of the hydrophilic fiber, any method can be used. For example, first, the hydrophilic polymer is made into a solution, and the solution is impregnated into the sheet, coated, and sprayed. , Coating, etc., and then solidifying the hydrophilic polymer.

For example, when regenerated cellulose is used as the hydrophilic polymer, a method similar to the viscose processing method used for a general packaging material or the like is employed as a method of supporting the regenerated cellulose on a sheet made of hydrophilic fibers. be able to. That is, the sheet is impregnated or coated with an alkali-type cellulose solution such as viscose, and the coagulation liquid coagulates and regenerates the alkali-type cellulose solution, whereby the regenerated cellulose can be fixedly supported on the sheet. As a method of impregnating or applying the alkali-type cellulose solution to the sheet made of the above-mentioned hydrophilic fiber, for example, the sheet may be simply immersed in a viscose bath, a coating method using a roll coater or the like, a spraying method, brushing or the like. Can be used. If a coagulant containing an acid is used as the coagulating liquid, cellulose can be regenerated simultaneously with coagulation.

Examples of the coagulating solution include concentrated salt solutions, inorganic acids, and organic acids. Examples of the coagulating solution for the alkaline cellulose solution include inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, acetic acid, and benzoic acid. And the like are preferred. Among these, sulfuric acid is more preferred because coagulation and regeneration proceed quickly and are relatively difficult to volatilize.

When sulfuric acid is used as the coagulating liquid, its concentration is preferably 1 to 20% by weight, more preferably 5 to 10% by weight. If it is less than 1% by weight, it takes time to coagulate and regenerate,
On the other hand, if it exceeds 20% by weight, solidification and regeneration occur rapidly, causing uneven shrinkage and easy deformation.

For the purpose of accelerating coagulation of the alkali-type cellulose solution, the coagulation solution may be used alone or with an aqueous solution of an inorganic salt such as sodium chloride, calcium chloride, ammonium chloride, sodium sulfate, ammonium sulfate or magnesium sulfate. You may mix two or more types, or heat a coagulation liquid.

When viscose is used as the alkali type cellulose solution, a step of desulfurization treatment with sodium sulfide or the like may be inserted after the coagulation regeneration step. After the desulfurization treatment, washing may be performed, and a bleaching treatment step using sodium hypochlorite or the like may be inserted as necessary.

As a method for supporting a water-soluble polymer other than regenerated cellulose on a sheet composed of hydrophilic fibers, first, a solution of the water-soluble polymer is impregnated or coated on the sheet by the same means as the viscose processing method. After that, it can be fixed and supported by insolubilizing by performing a chemical crosslinking treatment or the like.

Further, a sheet made of a hydrophilic fiber is impregnated or coated with a solution obtained by mixing a cellulose solution and a water-soluble polymer, and then the water-soluble polymer is insolubilized and the cellulose is regenerated. And another hydrophilic polymer can be fixed and supported at the same time.

The amount of the hydrophilic polymer supported on the sheet composed of hydrophilic fibers is from 20 to 9
It is preferable to carry it in the range of 0% by weight, preferably 30 to 70% by weight. If the amount is less than 20% by weight, the fibers are likely to be detached from the sheet, and the strength of the obtained pad may be reduced. If the amount exceeds 90% by weight, the obtained pad may lack flexibility.

The sheet composed of the hydrophilic fibers and the polishing pad composed of a hydrophilic polymer can be polished by improving the polishing efficiency or by using a polishing pad that does not require a polishing slurry, that is, by merely supplying water. For the purpose of so-called fixed abrasive grains, inorganic fine particles for polishing can be carried.

The particle size of the inorganic fine particles is from 0.01 to 10
μm is preferred, and 0.1-1 μm is preferred. Particle size 0.0
When the thickness is less than 1 μm, the polishing efficiency is deteriorated, and it may take a very long time to uniformly disperse the hydrophilic polymer in a solution or a cellulose solution.

As the inorganic fine particles, fine particles of silicon oxide, aluminum oxide, cerium oxide or the like may be used alone or
A mixture of more than one kind can be used.

As a method for supporting the inorganic fine particles, there is a method of mixing the inorganic fine particles with a solution of a hydrophilic polymer or a cellulose solution.

The amount of the inorganic fine particles to be mixed is preferably 2 to 90% by weight, more preferably 50 to 80% by weight, based on the hydrophilic fiber or hydrophilic polymer. If it is less than 2% by weight,
The abrasive effect of the abrasive inorganic particles is hardly exhibited, and if it exceeds 90% by weight, the particles become brittle.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. In the following, “%” indicates “% by weight”. The moisture content is a value obtained by adjusting the humidity at 20 ° C. and a relative humidity of 65%, and then by the absolute drying method.

Example 1 700 mm square hardwood pulp sheet (LBKP, 1000 g / m ² , moisture content) in viscose for cellophane production (cellulose concentration 9.5%, ammonium chloride value 7, alkali concentration 6%) 9%), and the pulp sheet was sufficiently impregnated with viscose.
After removing excess viscose adhering to the surface, it was immersed in 8% sulfuric acid to coagulate the viscose impregnated in the pulp sheet and regenerate cellulose. Then, it is desulfurized with a 0.3% aqueous sodium sulfide solution heated to 70 ° C.
Bleaching was carried out with an aqueous sodium hypochlorite solution. Finally, the sheet was thoroughly washed with water, dried with hot air, and punched into a circular shape having a diameter of 24 inches to obtain a polishing pad. The amount of the regenerated cellulose supported on the obtained polishing pad was 40% (absolute dry weight ratio) with respect to the pulp sheet, and the contact angle of water on the pad surface was 10 °.

When the silicon wafer provided with an oxide film was polished with the obtained polishing pad, the retention of the polishing slurry was good, and the polishing rate was 1000 ° / min.

Example 2 A polishing pad was obtained in the same manner as in Example 1 except that viscose was diluted with water to adjust the cellulose concentration to 7.9%. The regenerated cellulose carrying amount of the obtained polishing pad was 27.5% based on the pulp sheet.
(Absolute dry weight ratio) and the contact angle of water on the pad surface is 10
°.

When the silicon wafer with the oxide film was polished with the obtained polishing pad, the holding property of the polishing slurry was good, and the polishing rate was 800 ° / min.

Example 3 A 8% aqueous solution of polyvinyl alcohol (degree of saponification 98.5%, degree of polymerization 2000) was mixed with a polyamide epoxy resin-based cross-linking agent (Sumitomo Chemical Co., Ltd .: Sumireze Resin 675, 25). % Aqueous solution) at a solid content of 10%, and a 250 mm square dissolving pulp sheet (800 g / m ² , water content 9%) is immersed in the mixed solution.
The pulp sheet was sufficiently impregnated with polyvinyl alcohol. After removing excess polyvinyl alcohol adhering to the surface, the resultant was dried at 40 ° C. and further subjected to heat treatment at 120 ° C. for 1 hour. Then, a circular pad having a diameter of 200 mm was punched to obtain a polishing pad. The amount of polyvinyl alcohol carried on the obtained polishing pad was 24% based on the pulp sheet.
(Absolute dry weight ratio) and the contact angle of water on the pad surface is 15
°.

When the silicon wafer with the oxide film was polished with the obtained polishing pad, the holding property of the polishing slurry was good, and the polishing rate was 500 ° / min.

(Comparative Example 1) A 250 mm square dissolving pulp sheet (mixed with a 1: 4 mixture of a polyester polyurethane resin (manufactured by Dainippon Ink and Chemicals, Inc .: "Chrisbon 8867") and dimethylformamide) was used. 800
g / mm ² , a water content of 9%) and impregnated with the solution, and then squeezed to three times the original weight. afterwards,
Immerse the sheet in pure water to solidify the polyurethane resin,
After sufficiently washing with water, hot air drying was performed. Furthermore, it was punched into a circle having a diameter of 200 mm. In this case, the amount of loaded resin was 28%, and the contact angle of water on the sample surface was 80 °.

When the obtained sample was mounted on the above-mentioned CMP polishing apparatus and the silicon wafer was polished while supplying the above-mentioned polishing slurry, the polishing slurry was not uniformly held, so that the wafer surface was scratched.

(Comparative Example 2) A sample was obtained in the same manner as in Example 2 except that the pulp sheet was impregnated with viscose and then pressed so as to be three times the original weight. The carrying amount of the regenerated cellulose of the obtained sample was 15.5% (absolute dry weight ratio) with respect to the pulp sheet, and the contact angle of water on the surface of the regenerated cellulose was 10 °.

When the obtained polishing pad was mounted on the above-mentioned CMP polishing apparatus and the silicon wafer was polished while supplying the above-mentioned polishing slurry, the fibers began to be detached from the surface of the sample, and the fiber did not have sufficient durability. Polishing could not be performed.

[0049]

According to the present invention, since 20 to 90% by weight of the hydrophilic polymer is carried on the hydrophilic fiber, the disintegration of the fiber is suppressed and the durability is improved. In addition, since a hydrophilic material is used, the pad surface becomes hydrophilic, and the polishing slurry is easily held.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Higashiyama 1-8-10 Jiyugaoka, Kanatsu-machi, Sakai-gun, Fukui Prefecture Inside Rengo Co., Ltd. Fukui Research Institute (72) Inventor Tadashi Muramoto 1-Jiyugaoka, Kanazu-cho, Sakai-gun, Fukui Prefecture No. 8-10 Inside Rengo Co., Ltd. Fukui Research Laboratory (72) Inventor Hidenao Saito 1-8-10 Jiyugaoka, Kanatsu-machi, Sakai-gun, Fukui Prefecture Inside No. 8 Rengo Co., Ltd. Fukui Research Laboratory (72) Inventor Shigeru Tominaga 6 Minamioi, Shinagawa-ku, Tokyo No. 20-12, Loki Techno Co., Ltd. (72) Inventor Tetsuji Hirara 5-36-5, Kamata, Ota-ku, Tokyo F-term in AC Co., Ltd. 3C058 AA07 AA09 CA01 CB01 DA12

Claims (9)

[Claims] 1. A polishing pad in which a hydrophilic polymer is supported on a sheet composed of hydrophilic fibers in an amount of 20 to 90% by weight. 2. The polishing pad according to claim 1, wherein the hydrophilic polymer is regenerated cellulose. 3. The polishing pad according to claim 1, wherein inorganic fine particles for polishing are supported. 4. The loading amount of the inorganic fine particles is 2 to 9
The polishing pad according to claim 3, which is 0% by weight. 5. The particle size of said inorganic fine particles is 0.01 to 10
The polishing pad according to claim 3, wherein the thickness of the polishing pad is μm. 6. The polishing pad according to claim 3, wherein the inorganic fine particles are one or a mixture of two or more selected from silicon oxide, cerium oxide, and aluminum oxide. 7. A method for producing a polishing pad by applying or impregnating a hydrophilic polymer solution to a sheet composed of hydrophilic fibers to solidify and insolubilize the hydrophilic polymer solution. 8. The method for producing a polishing pad according to claim 7, wherein the solution of the hydrophilic polymer is a cellulose solution. 9. The method for producing a polishing pad according to claim 7, wherein inorganic fine particles for polishing are mixed with the solution of the hydrophilic polymer.