JP2002018731A - Abrasive pad and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CMP abrasive pad having a hydrophilic property and improved in the retainability of abrasive slurry. SOLUTION: Abrasive inorganic fine-grains are dispersed at 10-90 wt.% in regenerated cellulose.

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 and the like (hereinafter, referred to as a "semiconductor wafer and the like"). 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 former synthetic polymer molded article is mainly composed of a material having poor hydrophilicity, it is difficult to use a material having good wettability and water retention. Nevertheless, 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 polishing efficiency and 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. Therefore, as described above, the polishing efficiency and the polishing accuracy are adversely affected.

[0008] With respect to the above-mentioned deterioration in polishing efficiency and polishing accuracy,
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 abrasives enter the holes and grooves and accumulate to cause clogging. Due to this clogging, the polishing slurry is no longer held, causing a sharp decrease in polishing efficiency and scratching.

On the other hand, a cleaning material comprising a polyvinyl acetal sponge having an abrasive fixed thereto is disclosed in Japanese Patent Laid-Open No.
It is disclosed in JP-A-130634, and it is conceivable to use this as a CMP polishing pad. in this case,
A polishing slurry is unnecessary, or a small amount of polishing slurry is required. However, although polyvinyl acetal has a hydrophilic group, its wettability is insufficient, and water or polishing slurry is not uniformly held on the pad surface, so that polishing accuracy is poor.

Accordingly, an object of the present invention is to provide a CMP polishing pad having hydrophilicity and improved holding property of a polishing slurry.

[0011]

The present invention has solved the above-mentioned problems by dispersing 10 to 90% by weight of abrasive inorganic fine particles in regenerated cellulose.

Since the regenerated cellulose having excellent wettability is used, the polishing slurry can be uniformly held on the polishing pad surface.

Further, since the abrasive inorganic fine particles are dispersed in the regenerated cellulose, a polishing pad of a fixed abrasive type is obtained. Moreover, because the regenerated cellulose is the base material, it itself wears moderately during polishing and releases abrasive grains.
Polishing slurry is not required, or polishing is possible with only a small supply.

[0014]

Embodiments of the present invention will be described below.

The polishing pad according to the present invention is obtained by dispersing abrasive inorganic fine particles in regenerated cellulose.

The above-mentioned regenerated cellulose is cellulose regenerated from a cellulose solution or a solution of a cellulose derivative. The source of the raw material cellulose is not particularly limited, and examples thereof include wood, cotton, hemp, and the like. Here, as the cellulose solution, formaldehyde-dimethylsulfoxide, lithium chloride-
Dimethylacetamide, N-methylmorpholine-N-
Examples thereof include a solution in which cellulose such as an oxide is directly dissolved in a solvent, and an alkali-type cellulose solution such as viscose, cellulose copper ammonia solution, and cellulose carbamate. Examples of the solution of a cellulose derivative include a solution in which a cellulose ester such as cellulose nitrate and cellulose acetate and a cellulose ether such as carboxymethyl cellulose and methyl cellulose are dissolved in a solvent such as water. Among these, the alkali-type cellulose solution is easy to handle and relatively inexpensive, and among them, viscose, particularly viscose for cellophane, 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 becomes extremely high, making it difficult to handle, and it takes a long processing time for regeneration.

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.

The regenerated cellulose can be made porous for the purpose of further improving the retention of the abrasive inorganic fine particles contained in the obtained polishing pad. The pore size when the regenerated cellulose is made porous is 1 to 100 μm.
m is preferable, and 5 to 50 μm is more preferable. If it is smaller than 1 μm, it may not be very effective for improving the retention of the abrasive inorganic fine particles.
If it is larger than μm, the mechanical strength of the pad may be extremely reduced.

The above-mentioned abrasive inorganic fine particles are inorganic fine particles that impart polishing ability to the obtained polishing pad. The abrasive inorganic fine particles are dispersed and fixed in the regenerated cellulose by being dispersed in the above-mentioned cellulose solution or the solution of the cellulose derivative, and then coagulated and regenerated. For this reason,
The obtained polishing pad is a so-called fixed abrasive, which does not require a polishing slurry or can be polished only by supplying a small amount.

The particle size of the inorganic fine particles is 0.01 to 10
μm is preferred, and 0.1-1 μm is preferred. Particle size 0.0
If it is less than 1 μm, it may take a very long time to uniformly disperse the cellulose solution or cellulose derivative in the solution. If it exceeds 10 μm, the flatness of the object to be polished and the uniformity of polishing may be poor.

As the inorganic fine particles, any inorganic fine particles can be used as long as they have a polishing effect on an object to be polished and there is no extreme dissolution or deterioration in the production process in the present invention. For example, silicon oxide, aluminum oxide, cerium oxide, manganese dioxide, chromium oxide,
Inorganic fine particles such as iron oxide, zirconium oxide, silicon carbide, and diamond can be used alone or in combination of two or more.

The amount of the inorganic fine particles dispersed in the regenerated cellulose is 1 to the total weight of the obtained polishing pad.
The content is preferably 0 to 90% by weight, and more preferably 50 to 80% by weight.
If it is less than 10% by weight, the polishing effect is difficult to appear, and 9
If it exceeds 0% by weight, uniform dispersion may not be achieved or the composition may become extremely brittle.

Further, a hydrophilic polymer other than the above-mentioned regenerated cellulose can be compounded with the above-mentioned regenerated cellulose. By combining this hydrophilic polymer, the hardness and mechanical strength of the obtained polishing pad can be improved. Since the hydrophilic polymer is used, the hydrophilicity of the regenerated cellulose is maintained, and the uniformity of polishing can be maintained.

The above hydrophilic polymer is required to be insoluble in water since it is exposed to an aqueous polishing slurry. Examples of such a hydrophilic polymer include those obtained by insolubilizing a water-soluble polymer by chemical crosslinking. Specific examples include polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyethylene glycol, polyvinyl ethers, insoluble synthetic polymers such as polyethyleneimine by chemical crosslinking, sodium alginate, gum arabic, gelatin, starch, pullulan, dextran. And the like, which are obtained by chemically crosslinking natural polymers such as

The degree of hydrophilicity of these hydrophilic polymers is as follows:
If the material alone can be formed into a film or plate, 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
20 ° or less is preferable, and 100 ° or less is more preferable.
If the angle is larger than 20 °, the hydrophilicity inherent in the regenerated cellulose as a base material may be impaired.

The amount of the hydrophilic polymer to be combined with the regenerated cellulose is preferably 5 to 5 parts with respect to the regenerated cellulose.
It is preferably 80% by weight, more preferably 20 to 50% by weight. When the amount is less than 5% by weight, there is almost no effect on hardness and mechanical strength. On the other hand, when the amount is more than 80% by weight, excellent hydrophilicity of regenerated cellulose may be impaired.

As a method for dispersing the above-mentioned abrasive inorganic fine particles in regenerated cellulose, the above-mentioned abrasive inorganic fine particles are dispersed in a raw material cellulose solution or a solution of a cellulose derivative, and then the cellulose solution or the cellulose derivative solution is regenerated. There is a method. As a method of dispersing the abrasive inorganic fine particles in the raw material cellulose solution or the cellulose derivative solution, the abrasive inorganic fine particles may be directly added to the cellulose solution or the cellulose derivative solution being stirred by a stirrer or a kneader or the like. Or the like, and may be added. Further, for the purpose of improving the dispersion state, a dispersant may be added and dispersed.
The order of addition is not particularly limited.

The polishing pad according to the present invention can be obtained by dispersing the above-mentioned abrasive inorganic fine particles in a cellulose solution or a solution of a cellulose derivative, forming a sheet, and then coagulating and regenerating the sheet.

When an alkali-type cellulose solution is used among the above-mentioned cellulose solutions or cellulose derivative solutions, the cellulose is regenerated at the same time as coagulation by immersion in a coagulation / regeneration solution containing an acid. Therefore, the polishing pad of the present invention can be obtained by forming a solution in which the abrasive inorganic fine particles are dispersed in the alkaline cellulose into a sheet, and immersing the sheet in a coagulation / regeneration solution containing an acid.

As the coagulation / regeneration liquid, sulfuric acid, hydrochloric acid,
Examples include inorganic acids such as phosphoric acid and organic acids such as acetic acid and benzoic acid. Among these, coagulation and regeneration proceed rapidly,
Sulfuric acid is more preferred because it is relatively difficult to volatilize.

When sulfuric acid is used as a coagulation / regeneration liquid,
The 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 a long time to solidify and regenerate. If it exceeds 20% by weight, solidification and regeneration occur rapidly, so that uneven shrinkage and remarkable deformation of the molded body are liable to occur.

Also, a solution in which abrasive inorganic fine particles are dispersed in an alkali type cellulose solution is coagulated in advance by dipping in a concentrated salt solution or applying heat, and then dipped in an acid to regenerate the cellulose. You may. Examples of the concentrated salt solution include an aqueous solution in which one or more inorganic salts such as sodium chloride, calcium chloride, ammonium chloride, sodium sulfate, ammonium sulfate, and magnesium sulfate are mixed.

Further, a mixture of the above inorganic salt and an acid may be used as a coagulation / regeneration liquid.
For the purpose of promoting regeneration, the coagulation / regeneration liquid may be heated.

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 of combining another hydrophilic polymer with the above-mentioned regenerated cellulose, the above water-soluble polymer is dissolved or mixed in a cellulose solution or a solution of a cellulose derivative to coagulate and insolubilize the hydrophilic polymer. Thereafter, a method of regenerating cellulose can be mentioned.

Further, as another method of compounding the regenerated cellulose with another hydrophilic polymer, a pulverized product, a particulate material, a fine powder, a fibrous material, etc. of the above-mentioned hydrophilic polymer are directly added to a cellulose solution or cellulose. After mixing and dispersing in the derivative solution,
By coagulating and regenerating a cellulose solution or a solution of a cellulose derivative, a hydrophilic polymer can be compounded in regenerated cellulose. In this case, the hydrophilic polymer used may be in a dry state or a hydrogel state.

Examples of the method for converting the regenerated cellulose into a porous material include a method of dissolving a polysaccharide in a cellulose solution or a solution of a cellulose derivative to coagulate and regenerate the cellulose, or a method of using a surfactant to prepare a cellulose solution or a cellulose derivative. And a method of coagulating and regenerating by previously bubbling the solution.

The polishing pad obtained according to the present invention is a pad of the fixed abrasive type, and at the same time, the regenerated cellulose is appropriately abraded, so that the abrasive inorganic fine particles that have partially fallen off during polishing act as free abrasive particles. I do. Further, since the regenerated cellulose has extremely excellent wettability, the supplied water or polishing slurry is uniformly dispersed on the pad surface together with the abrasive inorganic fine particles, and efficient polishing proceeds.

Further, since the base material of the polishing pad obtained by the present invention is made of regenerated cellulose, it can be formed into an arbitrary shape. For this reason, a polishing pad of an arbitrary form can be provided according to the place of use or the like.

The object to be polished by precision polishing using the polishing pad obtained by the present invention is not particularly limited, and examples thereof include a semiconductor wafer, a memory disk, a liquid crystal glass, and an optical component lens. .

[0042]

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”.

Example 1 40 parts by weight of cerium oxide (average particle size: 1 μm) was put in 100 parts by weight of viscose (cellulose concentration: 9.5%, ammonium chloride value: 7, alkali concentration: 6%) for cellophane production. Solution mixed with
It was poured into a 0 cm square, 3 mm thick mold, immersed in 8% sulfuric acid, and solidified and regenerated. Then, the mixture was heated to 70 ° C.
The mixture was desulfurized with a 3% aqueous sodium sulfide solution and bleached with a 0.3% aqueous sodium hypochlorite solution. After sufficiently washing the obtained sheet with water, it was punched into a circular shape having a diameter of 60 cm to obtain a polishing pad. The obtained polishing pad had a cerium oxide weight ratio of 80%, a contact angle of 10 °, and a hardness of 79 using an ASKER C type hardness meter.

The obtained polishing pad was mounted on a CMP polishing apparatus, and the silicon wafer with an oxide film was polished.
The polishing rate was 1000 ° / min. No scratch was observed on the obtained wafer.

Example 2 100 parts by weight of the viscose used in Example 1 was mixed with polyvinyl alcohol (saponification degree 98.
A solution prepared by adding 12 parts by weight of an 8% aqueous solution having a polymerization degree of 5% and a polymerization degree of 2000) and 44 parts by weight of the cerium oxide used in Example 1 was poured into a mold having a size of 120 cm square and 3 mm thick. Was coagulated and regenerated with 7% hydrochloric acid mixed with water. Thereafter, the mixture was washed with water, centrifugally dehydrated, and impregnated with a mixed solution of 7.3 parts by weight of ethylene glycol diglycidyl ether and 10.5 parts by weight of a 2% aqueous sodium hydroxide solution.
After drying at 60 ° C, heat-treating at 120 ° C for 2 hours,
The solution was desulfurized with a 0.3% aqueous sodium sulfide solution heated to 70 ° C., and bleached with a 0.3% aqueous sodium hypochlorite solution.
After sufficiently washing the obtained sheet with water, it was punched into a circular shape having a diameter of 60 cm to obtain a polishing pad. The absolute dry weight ratio of regenerated cellulose and polyvinyl acetal in the obtained polishing pad was 10: 1, the weight ratio of cerium oxide in the pad was 80%,
The contact angle was 13 °, and the hardness measured by an ASKER C-type hardness tester was 88.

When the obtained polishing pad was polished by the method described in Example 1, the polishing rate was 1200 ° / min.
Met. No scratch was observed on the obtained wafer.

Example 3 9.5 parts by weight of silicon oxide (average particle size: 0.1 μm) and 1 part by weight of sodium lauryl sulfate were mixed with 100 parts by weight of the viscose used in Example 1, and mixed. Stir with a whisk. The subsequent operations were performed according to the method described in Example 1 to obtain a polishing pad. The obtained polishing pad has a diameter of 50 to 100 μm.
m independent holes were uniformly distributed. The silicon oxide weight of the polishing pad was 50%, the contact angle was 10 °, and the ASKER
The hardness according to a C-type hardness meter was 77.

When the obtained polishing pad was polished by the method described in Example 1, the polishing rate was 800 ° / min. No scratch was observed on the obtained wafer.

Comparative Example 1 The viscose used in Example 1 was molded according to the method described in Example 1 to obtain a pad containing no abrasive inorganic fine particles. The obtained pad had a contact angle of 10 ° and a hardness of 76 using an ASKER C hardness meter.

The obtained polishing pad was polished by the method described in Example 1, but the silicon wafer was not polished.

Comparative Example 2 A 100% by weight aqueous solution of 8% polyvinyl alcohol used in Example 2 was mixed with a polyamide epoxy resin-based crosslinking agent (Sumitomo Chemical Industries, Ltd .: Sumireze Resin 675, 25% aqueous solution). 3.2 parts by weight and 37 parts by weight of cerium oxide described in Example 1 were mixed and poured into the mold described in Example 1. This was dried at 40 ° C., and further heat-treated at 120 ° C. for 1 hour. Furthermore, a pad was obtained by punching out a circle having a diameter of 60 cm. The weight ratio of cerium oxide was 80%, the contact angle of the obtained pad was 15 °, and the hardness measured by an ASKER C type hardness meter was 93.

The obtained polishing pad was polished by the method described in Example 1, but the silicon wafer was not polished. When the operation was performed while supplying the polishing slurry, the polishing rate was 1200 ° / min, but scratches occurred on the wafer surface.

[0053]

According to the present invention, since the regenerated cellulose having excellent wettability is used, the polishing slurry can be uniformly held on the polishing pad surface.

Further, since the abrasive inorganic fine particles are dispersed in the regenerated cellulose, the obtained polishing pad becomes a fixed abrasive which can be polished without the need for a polishing slurry or can be polished only by supplying a small amount thereof, and has a high polishing efficiency.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01L 21/304 622 H01L 21/304 622F (72) Inventor Satoshi Muramoto 1-Jiyugaoka, Kanatsu-cho, Sakai-gun, Fukui Prefecture No. 8-10 Rengo Co., Ltd. Fukui Research Laboratory (72) Inventor Satoshi Higashiyama 1-8-10 Jiyugaoka, Kanazu-cho, Sakai-gun, Fukui Prefecture Fukui Research Laboratory (72) Inventor Hidenao Saito Jiyugaoka, Kanatsu-cho, Fukui Prefecture 1-8-10 Rengo Co., Ltd. Fukui Research Laboratory (72) Inventor Shigeru Tominaga 6-20-12 Minamioi, Shinagawa-ku, Tokyo Loki Techno Co., Ltd. (72) Inventor Tetsuji Hirara 5-36 Kamata, Ota-ku, Tokyo No. 5 F-term in ACE Co., Ltd. (reference) 3C058 AA09 CB01 CB02 CB03 DA17 3C063 AA10 AB07 BA2 2 BB01 BB02 BB03 BB04 BE06 EE01 EE02 EE10 EE26 FF20 FF30

Claims (7)

[Claims] 1. A polishing pad comprising 10 to 90% by weight of abrasive inorganic fine particles dispersed in regenerated cellulose. 2. The polishing pad according to claim 1, wherein a hydrophilic polymer other than the regenerated cellulose is compounded with the regenerated cellulose in an amount of 5 to 80% by weight based on the regenerated cellulose. 3. The inorganic fine particles having a particle size of 0.01 to 10
The polishing pad according to claim 1, wherein the thickness is μm. 4. The inorganic fine particles are one or a mixture of two or more selected from silicon oxide, cerium oxide, aluminum oxide, manganese dioxide, chromium oxide, iron oxide, zirconium oxide, silicon carbide, and diamond. 4. The polishing pad according to any one of claims 1 to 3. 5. The polishing pad according to claim 1, wherein the regenerated cellulose is a porous body. 6. A method for producing a polishing pad in which abrasive inorganic fine particles are dispersed in a cellulose solution or a solution of a cellulose derivative, formed into a sheet, and solidified and regenerated. 7. The method according to claim 6, wherein the cellulose solution is an alkaline cellulose solution.