KR20090005453A - Polishing pad - Google Patents

Abstract

A grinding pad is provided to prevent air gap from being blocked by an abrasive in a polishing process by dissolving gradually simple fiber comprising non-woven using the abrasive in the polishing process and forming new air gaps, to extend a cycle of conditioning and reduce scratch. A grinding pad contains non-woven consisting of simple fibers(1) interlaced each other and a high molecule elastomer(2) impregnated into the non-woven. At least a part of the simple fiber is a solubility fiber dissolved by an abrasive. A content of solubility fiber in the non-woven is 20~100 weight% based on total weight of the non-woven. The solubility fiber is made of a polyvinyl alcohol type resin.

Description

Polishing Pad {Polishing pad}

1 is a schematic cross-sectional view of a polishing pad according to the present invention.

2 is a schematic cross-sectional view of a polishing pad showing a state in which the soluble fibers in the polishing pad according to the present invention are partially dissolved by the polishing liquid to form new voids 3.

* Code description for main parts of the drawings

1: short fiber 2: polyurethane resin

3: void

The present invention is useful for chemical mechanical polishing (CMP), particularly for CMP methods of planarizing flat glass or other substrates for silicon wafers or displays used in the manufacture of integrated circuit chips or the like. It relates to a polishing pad.

The silicon wafer and the like are smoothly processed by the CMP polishing apparatus, and the CMP polishing apparatus includes a lower board having a circular rotating plate on which the polishing pad is mounted, an upper board which adheres the silicon wafer to the polishing pad, and a device for supplying slurry to the polishing pad. do.

Chemical-mechanical polishing, a CMP operation, pushes the surface of the semiconductor wafer on which the integrated circuit will be fabricated in the opposite direction to remove oxides, including deposited Si-based oxides, and creates a very smooth and flat surface on the wafer. As an operation, deionized water and / or chemically active reagents are applied along with the polishing liquid to the interface between the wafer and the polishing pad during the CMP operation.

As a polishing pad used in a conventional CMP method, Japanese Laid-Open Patent Publication No. 2005-330621 includes a nonwoven fabric composed of nylon short fibers of about 1 to 5 deniers and a polyurethane resin impregnated in the nonwoven fabric. A polishing pad containing a plurality of voids formed at the time is disclosed.

The polishing pad is manufactured by heat-treating a nonwoven fabric impregnated with a polyurethane resin at a high temperature.

However, in the conventional polishing pad, voids generated during wet coagulation of the polyurethane resin are dispersed, but in the polishing process, the voids are easily blocked by the polishing liquid, and thus, the polishing pad should be conditioned in a relatively short period.

Therefore, the conventional polishing pad has a problem in that the process efficiency is lowered, and when the conditioning operation is delayed, the polishing performance is lowered and the scratch generation rate due to polishing is increased.

The present invention consists of short fibers (hereinafter also referred to as "soluble fibers") in which all or a part of the short fibers constituting the nonwoven fabric are gradually dissolved by the polishing liquid so as to solve the conventional problems as described above. To continue to form, thereby providing a polishing pad with a significantly extended conditioning period.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, the polishing pad according to the present invention is a polishing pad composed of a nonwoven fabric in which the short fibers 1 are entangled with each other and a polymer elastic body 2 impregnated in the nonwoven fabric, as shown in FIG. At least a part of 1) is characterized in that the soluble fibers are dissolved little by little by the polishing liquid.

1 is a schematic cross-sectional view of a polishing pad according to the present invention.

As an example of the soluble fiber dissolved little by little by the polishing liquid, a fiber made of polyvinyl alcohol-based resin or the like may be used. The soluble fiber content in the nonwoven fabric in which the short fibers are entangled, that is, the nonwoven fabric in which the polymer elastic body is not impregnated, is preferably 20 to 100% by weight based on the total weight of the nonwoven fabric.

If the content is less than 20% by weight, the effect of extending the conditioning period is low, and the process efficiency is not greatly improved.

The single yarn fineness of the soluble fiber is preferably 0.1 to 6 denier levels.

When the single yarn fineness exceeds 6 deniers, the voids are formed too large, and the polishing quality is lowered. When the single yarn fineness is less than 0.1 denier, the polishing quality is improved, but the yarn manufacturing process is cumbersome.

Polyurethane resin, polyurea resin and the like may be used as the polymer elastomer, but a polyurethane resin is most preferable in view of processability.

Next, a method of manufacturing a polishing pad according to the present invention is described in detail.

In the present invention, after preparing a nonwoven fabric containing soluble short fibers (1) made of polyvinyl alcohol-based resin, and impregnated with a polymeric elastomer (2) in the nonwoven fabric to form a micro void to produce a polishing pad. In manufacturing the nonwoven fabric, only the soluble short fibers described above may be used alone, or soluble short fibers and polyester short fibers or polyamide fibers may be mixed. The content of the soluble short fibers in the nonwoven fabric is 20 to 100% by weight based on the total weight of the nonwoven fabric.

Polyurethane resins, polyurea resins, polyacrylic acid resins, and the like may be used as the polymer elastomer, but a polyurethane resin is preferable in view of processability, wear resistance, hydrolysis resistance, and the like.

The weight ratio of the fibrous base composed of the polymer elastomer / microfiber is preferably 30/70 to 90/10.

If the weight ratio of the polymer elastomer is less than 30% by weight, the hardness of the polishing pad is too low, and if it exceeds 90% by weight, the hardness of the polishing pad may be too high.

The method of filling the polymer elastomer may impregnate and / or apply an organic solvent solution or an aqueous dispersion of the polymer elastomer to the nonwoven fabric and then attach it by wet coagulation or dry coagulation. It is necessary to attach it uniformly in a substantially filling form, and solidifying the polymer elastomer in a porous shape is preferable for polishing without causing defects such as scratching due to slurry agglomeration or polishing residues. After filling the polymer elastomer by the wet coagulation method, the method of increasing the density of the polymer elastomer by the second dry coagulation method is most suitable.

As an organic solvent of a high molecular elastic body, toluene, acetone, methyl ethyl ketone, etc. other than polar solvents, such as dimethylformamide, dimethylacetamide, and dimethyl sulfoxide, can be used.

In the present invention, as described above, the nonwoven fabric impregnated with the elastic polymer 2 may be further buffed with sandpaper or the like.

In the present invention, instead of manufacturing the nonwoven fabric constituting the polishing pad from ordinary polyamide short fibers or polyester short fibers, single fibers (soluble fibers) gradually dissolved by a polishing liquid are used alone, or polyamide short fibers are used. It mixes and manufactures.

Therefore, the present invention gradually dissolves the soluble fibers contained in the polishing pad by the polishing liquid during the polishing process, thereby forming new voids 3 as shown in FIG.

FIG. 2 is a schematic cross-sectional view of the polishing pad showing a state in which new voids 3 are formed while the soluble fibers in the polishing pad are partially dissolved during the polishing process.

As a result, the phenomenon in which the voids of the polishing pad are clogged by the polishing liquid during the polishing process can be significantly reduced, and the period of conditioning can be significantly extended.

In addition, the present invention can effectively prevent problems such as a decrease in the polishing performance and an increase in the scratch occurrence rate generated when the proper conditioning operation is not performed.

In the present invention, the surface roughness and scratch occurrence rate of the polished silicon wafer were evaluated as follows.

Surface Average Roughness of Silicon Wafers

Carl Zeiss, a type of confocal laser scanning microscope (LSS) facility, LSM 5 PASCAL, a topography software package for LSM, or similar Measure by using LSM equipment.

Specifically, the center line average roughness (Ra) value of 10 irregularities formed on the surface based on JIS B 0601 by scanning the surface area range (width 1000 μm x length 1000 μm) of the polished silicon wafer with a laser Is measured and the ten point average roughness Rz of the surface of the polished silicon wafer is obtained from the arithmetic mean value.

Hereinafter, the ten point average roughness Rz is called surface average roughness.

Scratch Rate (%)

The number of scratches generated when scratching a silicon wafer with 100 square inch area by polishing pad is identified and substituted into the following equation.

Scratch Rate (%) = (Scratch Count / 100 Sq Inch) x 100

However, if the number of scratches exceeds 100, leave it at 100.

The scratch reading is judged by visual judgment by a skilled expert, and in the case of a faint defect that is difficult to read whether it is scratched with the naked eye, it may rely on the additional measurement of an optical microscope equipped with dark field illumination and image analysis software.

In addition, the scratch judges the scratch that the ratio of the length in the longitudinal direction and the width direction to be 10 to 1 or more.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

However, the present invention is not particularly limited by the following examples.

Example  One

Polyvinyl alcohol filament having a single yarn fineness of 1 denier was cut to a length of 50 mm, short fibers, and a laminated web of the filament short fibers were manufactured through carding and cross wrapper processes, and then needle punched to prepare a nonwoven fabric.

Next, the nonwoven fabric is impregnated with 30% by weight of the polyurethane resin to the nonwoven fabric weight, and then wet coagulated, and then dry solidified 30% by weight of polyurethane resin, and then buffing it with sandpaper to prepare a polishing pad It was.

100 square inches of the silicon wafer was polished under the following conditions using the prepared polishing pad.

Polishing condition

-Polishing machine: GNP Technology's Poli-500 Polisher

-Polishing time: 10 minutes

Down force: 250g / cm2 (3.5psi) on the wafer surface

-Polishing Table Speed: 120rpm

Wafer Carrier Speed: 120rpm

Slurry flow rate: 700 ml / min

-Slurry type: Nalco 2731, silica slurry diluted with DIW and slurry at 15: 1

Table 1 shows the results of measuring surface average roughness and scratch rate of the polished (polished) silicon wafer.

Example 2

Except for mixing 50% by weight of the polyvinyl alcohol filament short fibers used in Example 1 and 50% by weight of polyamide filament short fibers having 1 denier as the nonwoven fabric in the same process and method as in Example 1 A polishing pad was prepared, and 100 square inches of silicon wafer was polished using the same polishing process as in Example 1.

Table 1 shows the results of measuring the surface average roughness and scratch rate of the polished silicon wafer.

Comparative Example  One

A polishing pad was prepared in the same manner and in the same manner as in Example 1, except that polyamide filament short fibers having single densities of 3 deniers were used instead of the polyvinyl alcohol filament short fibers used in Example 1 when manufacturing the nonwoven fabric. Using this, 100 square inches of silicon wafers were polished by the same polishing process as in Example 1.

Table 1 shows the results of measuring the surface average roughness and scratch rate of the polished silicon wafer as described above.

Measurement results of polished wafer properties division Example 1 Example 2 Comparative Example 1 Surface Average Roughness of Polished Wafers 14.60 14.41 15.30 Scratch Rate (%) 0.10 0.11 0.17

Examples 1 and 2 were better than Example 1 in terms of scratch incidence and polishing performance (surface average roughness of the polished wafer) when the soluble fibers were included in the polishing pad and the polishing process was performed without conditioning.

According to the present invention, since the short fibers constituting the nonwoven fabric are gradually dissolved by the polishing liquid during the polishing process to form new voids, the phenomenon in which the voids are clogged by the polishing liquid during the polishing process can be largely eliminated. Therefore, the present invention has an advantage of extending the period of conditioning, low scratch rate during polishing, and excellent polishing performance.

Claims (4)

A polishing pad composed of a nonwoven fabric in which short fibers (1) are entangled with each other and a polymer elastic body (2) impregnated in the nonwoven fabric, wherein at least some of the short fibers (1) are soluble fibers dissolved little by little by a polishing liquid. Polishing pads, characterized in that. The polishing pad according to claim 1, wherein the soluble fiber content in the nonwoven fabric in which the short fibers (1) are entangled with each other is 20 to 100% by weight based on the total weight of the nonwoven fabric. The polishing pad according to claim 1, wherein the soluble fiber is made of polyvinyl alcohol-based resin. The polishing pad according to claim 1, wherein the single yarn fineness of the soluble fiber is 0.1 to 6 denier.

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