JPH10128674A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad, in the case of polishing a semiconductor wafer, memory disk, etc., which can improve flatness of this polishing surface extend a usable time and reduce a cost required for polishing. SOLUTION: A polishing pad 1 is formed by a felt-shaped fiber sheet 3 carrying a fine porous elastomer 4 composed mainly of polyurethane. A constitutional fiber of this felt-shaped fiber sheet 3 is 6.0 to 20.0 denier and 30 to 100mm fiber length, and METSUKE weight of the sheet is 150 to 600g/cm<2> . A difference between maximum/minimum heights of a polishing surface of the felt-shaped fiber sheet 3 is within 20μm, and for providing flatness within 20μm in Ra (ten point average height), flatness may be applied by a plane of the same width or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor wafer,
The present invention relates to a polishing pad used for polishing or polishing a memory disk, an optical component lens, and the like.

[0002]

2. Description of the Related Art Conventionally, as a polishing pad for mirror polishing a semiconductor wafer used as a base material for forming an integrated circuit, a velor-like or suede-like fiber / resin composite material generally known as artificial leather is used. And felted fibrous sheets impregnated with a thermoplastic polyurethane resin by wet coagulation.

In recent years, in particular, in semiconductor wafers and memory disks, demands for price reductions have been increasing in addition to quality improvement such as high flatness and the like. It is required to provide a function that enables the use of the device and to have a long usable time.

In response to such a demand, in a conventional mirror polishing process of a semiconductor wafer, a polishing pad used in a primary polishing process (stock removal process) for determining most of the flatness of the wafer is used. It has become clear that the flatness of the finished wafer is greatly affected by the hardness. As an index for quantifying the hardness, a compression ratio is cited, and this compression ratio largely depends on the amount of the microporous elastomer mainly composed of polyurethane used for the polishing pad. That is, the polishing pad which is relatively hard and has a low compressibility has a large amount of the microporous elastomer mainly composed of polyurethane adhered to the fiber, and particles of the microporous elastomer are remarkably present on the obtained polishing pad surface. As a result, the slurry and polishing debris are clogged in the fine holes of the polishing pad at an early stage, and as a result, the roughness of the wafer surface is large, and scratches tend to occur easily. In addition, polishing debris during polishing of a semiconductor wafer is liable to be clogged, and it is difficult to correct and remove it by brushing or the like, so that the usable time of a polishing pad is short.

On the other hand, in order to solve the above-mentioned problem, in a polishing pad in which the amount of microporous elastomer mainly composed of polyurethane attached to fibers is reduced, the compression ratio shows a high value. This is because the adhesion of microporous elastomer particles to the polishing pad surface is reduced, so that the voids on the polishing pad surface are increased, and as a result, clogging of polishing debris during polishing of a semiconductor wafer is suppressed. Although the usable time of the polishing pad can be lengthened, it is difficult to perform mirror finishing of a desired flatness of the semiconductor wafer in the primary polishing step (stock removal process) due to insufficient hardness.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to improve the flatness of the surface of an object to be polished, such as a semiconductor wafer, a memory disk, etc., and to be usable. An object of the present invention is to provide a polishing pad that can extend the time and reduce the cost required for polishing.

[0007]

The polishing pad of the present invention comprises a felt-like fibrous sheet carrying a microporous elastomer mainly composed of polyurethane, and the fibers constituting the felt-like fibrous sheet are: It is characterized by having a denier of 6.0 to 20.0 and a fiber length of 30 to 100 mm and a basis weight of the felt-like fibrous sheet of 150 to 600 g / cm ² , thereby achieving the above object.

That is, if the constituent fibers of the felt-like fibrous sheet, which is the starting raw material of the polishing pad, have a certain hardness in advance, the amount of the microporous elastomer mainly composed of polyurethane to be carried on the sheet is considered. Even when the amount is small, the polishing pad can be given a predetermined hardness, so that the adhesion of the microporous elastomer particles to the surface of the polishing pad can be suppressed, and the above problem can be solved.

Preferably, the polishing pad has a plurality of grooves formed on the polishing surface.

It is desirable that the difference between the maximum height and the minimum height of the polishing surface of the polishing pad be within 20 μm and the 10-point average height Ra be within 12 μm.

Further, the difference between the maximum height and the minimum height of the polishing surface of the polishing pad is within 20 μm, the average height Ra at 10 points is within 12 μm, and a plurality of grooves are formed in the polishing surface. It is desirable.

Another polishing pad of the present invention is obtained by impregnating a felt-like fibrous sheet with a resin solution mainly composed of polyurethane, and then wet-coagulating and drying the fibrous sheet to form the felt-like fibrous sheet. Is 6.0-2
It is characterized by 0.0 denier, a fiber length of 30 to 100 mm and a basis weight of the felt-like fibrous sheet of 150 to 600 g / cm ² , thereby achieving the above object.

The operation of the present invention is as follows.

The fibers constituting the felt-like fibrous sheet used for the conventional polishing pad have a denier number of 2 to 4.
Was formed in the degree. Therefore, there is a disadvantage that the fibers are present in a dense state on the polishing surface of the polishing pad and the voids are relatively reduced, so that the polishing debris during the polishing of the semiconductor wafer is easily clogged.

On the other hand, according to the polishing pad of the present invention, the constituent fibers of the felt-like fibrous sheet carrying the microporous elastomer mainly composed of polyurethane are 6.0 to 6.0.
20.0 denier, fiber length of 30 to 150 mm, and weight per unit area of 150 to 600 g / cm ² , it is possible to secure surface pores in mirror polishing of semiconductor wafers and the like. It is possible to prevent abrasive particles in the liquid from dropping and clogging. Thereby, stable polishing performance can be maintained for a long time, and the flatness of the polished surface of the object to be polished can be improved.

That is, the relatively large voids formed on the surface of the felt-like fibrous sheet provide excellent flowability of the polishing liquid, and the abrasive dust easily falls into the voids. The usable time of the pad can be maintained for a long time.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The felt-like fibrous sheet used in the present invention is resistant to polyurethane-soluble solvents such as DMF, MEK and tetrahydrofuran, and has a pH of about 10 to 11 used during polishing. Preferably, those having alkali resistance are used, and examples thereof include fibrous sheets made of nylon, polyester, aramid fiber and the like.

In the sheet, the fibers constituting the sheet are 6.
A non-woven fabric having a denier of 0 to 10.0, a fiber length of 30 to 100 mm, and a weight per unit area of 150 to 400 g / cm ² is preferable, and a needle-punched non-woven fabric containing no binder is more preferable. Of these, the basis weight can usually be changed depending on the frequency of needle punching and the fiber length.

More preferably, the fibers constituting the sheet have a denier of 6 to 8 and a fiber length of 40 to 70 mm, and a basis weight of 180 to 300 g / cm ² .

The constituent fibers of the felt-like fibrous sheet are 6.
If it is less than 0, as seen in the conventional example described above,
Since the fibers are present in a dense state on the polishing surface of the obtained polishing pad, the polishing debris during polishing of the semiconductor wafer are easily clogged, and when it exceeds 20.0 denier, the hardness of the polishing pad is too high. Therefore, the surface flatness of the object to be polished tends to deteriorate. If the fiber length is shorter than 30mm,
The microporous elastomer mainly composed of polyurethane is supported on the felt-like fiber in a predetermined amount or more, and the hardness of the polishing pad is too high. When the fiber length is longer than 150 mm, the microporous elastomer mainly composed of polyurethane cannot be sufficiently supported on the felt-like fiber, and the hardness of the polishing pad is too low. Further, when the basis weight of the sheet is less than 150 g / cm ² , the microporous elastomer mainly composed of polyurethane is supported on the felt-like fiber in a predetermined amount or more, and the hardness of the polishing pad is too high. The basis weight of the sheet is 600g
If it exceeds / cm ² , the microporous elastomer mainly composed of polyurethane cannot be sufficiently supported on the felt-like fiber, and the hardness of the polishing pad will be too low. The microporous elastomer mainly composed of polyurethane used in the present invention is an elastic body mainly composed of polyurethane having many micropores, and preferably has a modulus at 100% elongation of 100 kg / cm ² or more.

As the polyurethane used in the present invention, any commercially available polyurethane for artificial leather can be used. For example, polyester or polyether-based MDI (4,4'-diphenylmethane diisocyanate)
Alternatively, a urethane prepolymer having a TDI (tolylene diisocyanate) terminal alone or a blend of a melamine resin, a polycarbonate resin, or the like for adjusting the hardness and compressibility of a polishing pad (polishing cloth) may be used.

The polyurethane contains a bifunctional organic amine curing agent such as 3,3'-dichloro-4,4'-diaminodiphenylmethane and, if necessary, an accelerator mainly composed of a dicarboxylic acid such as adipic acid. obtain. These are DMF, M
It can be used by dissolving it in an organic solvent such as EK and tetrahydrofuran. When considering the thermal efficiency of drying, it is desirable to use a low boiling point solvent such as MEK as the organic solvent.

Further, the thickness of the polishing pad of the present invention is set at 0.3.
5 to 2.0 mm is preferred. The compression ratio of the polishing pad is 2.
The compression ratio of the polishing pad is preferably in the range of 0 to 14.0%, and particularly preferably 2.5 to 9.0%. If the thickness of the polishing pad is less than 0.5 mm or more than 2.0 mm, the workability when the polishing machine is mounted on the carrier plate is reduced. On the other hand, when the compression ratio is less than 2%, the wafer flatness is reduced, and
%, The polishing efficiency tends to deteriorate.

In the polishing pad of the present invention, the difference between the maximum height and the minimum height of the polishing surface of the polishing pad is within 20 μm, and the 10-point average height Ra is within 12 μm. More preferably, the difference between the maximum height and the minimum height of the polishing surface of the polishing pad is within 10 μm, and the 10-point average height Ra is 5 μm.
It is within μm.

As a method for producing the polishing pad of the present invention, for example, there is the following method.

(1) A felt-like fibrous sheet (sheet-like fibrous base material) is impregnated with the above-mentioned polyurethane DMF solution, and an intermediate composite base material is prepared through wet coagulation, washing and drying steps.

Here, the weight ratio of the resin phase to the fiber phase in the composite base material is preferably such that the resin relative fiber phase is 1: 1 to 1: 5. The polishing pad of the present invention is characterized in that the constituent fibers of the felt-like fibrous sheet have a denier of 6.0 to 20.0, a fiber length of 30 to 150 mm, and a basis weight of 150 to 600 g / cm ² , The compression elasticity of the working surface (sheet surface) is likely to be low, and in order to complement the compression elasticity, a resin is supported to increase hardness and prevent compression deformation during polishing.

For example, in the prior art, the porous structure by wet coagulation existing in the resin phase of the composite base material in which the weight ratio of the resin to the fiber phase exceeds 1: 1 becomes too dense.
Since a considerable amount of voids existing on the surface of the sheet-like fiber base material were filled with the resin phase, when used for polishing, the flow of the polishing liquid and polishing waste was hindered, and clogging occurred in a short time. . Conversely, the weight ratio of resin to fiber phase is 1
In a state below the ratio of 5, the resin phase only surrounds the entanglement point of the fiber and the outer peripheral portion, and the impregnated polyurethane tends to be localized on the side that was on the lower side of the sheet during drying, The reinforcing effect on the fiber was not obtained, and the target hardness was not reached.

Therefore, in the above step (1), the solid content of the impregnated polyurethane in the DMF solution is adjusted according to the bulk density of the sheet-like fiber substrate to be used, and the resin relative fiber phase in the obtained composite substrate is adjusted. The ratio is 1: 1 to 1: 5
Is preferable.

(2) Next, since the composite base material obtained in the above step (1) has a dense foam layer called a skin layer near the front and back surfaces, the foam layers on both front and back surfaces are removed, and the composite base material is flattened. It is used as a polishing pad by improving the degree.

If necessary, a plurality of grooves can be formed on the surface (working surface) of the polishing pad obtained in the above step (2). For example, a V-shaped cross section (depth 0.1 to 1.5
mm) can be formed in a mesh shape. By forming such grooves on the surface of the polishing pad, the polishing slurry is filled over the entire surface of the wafer, and the flattening of the wafer can be promoted.

If necessary, the surface (working surface) of the polishing pad obtained in the above step (2) is cut with a plane having a width equal to or larger than the outer diameter of the surface (working surface). By obtaining a flat surface (working surface), high flatness of the wafer can be promoted.

The polishing pad obtained in the above step (2) may be further impregnated with an unreacted thermosetting resin solution such as a thermosetting polyurethane solution and then dried.

The polishing pad of the present invention and the polishing performance thereof will be described in more detail with reference to the following Examples, but these Examples do not limit the present invention.

[0035]

【Example】

(A) The method for measuring the compressibility of the polishing pad (or sheet) obtained in the following examples is as follows.

Compression ratio = {(D1-D2) / D1} × 10
Calculated as 0 (%).

Here, D1 is the thickness of the polishing pad when a load of 300 gf / cm ² × 60 seconds is applied to the working surface.
Is the thickness of the polishing pad when a load of 1800 gf / cm ² × 60 seconds is applied to the working surface.

(B) A polishing test of a wafer using the polishing pad obtained in the following example is as follows.

The wafer was polished using a speed fam 59 SPAW2 type, and the wafer was polished with a silicon single crystal P (10
0) 8 inch diameter wafer was used. The polishing conditions are summarized in Table 1.

[0040]

[Table 1]

The dimensional accuracy of the polished wafer was evaluated using a capacitance type wafer flatness inspection machine; ADE9500 wafer flatness inspection meter.

(C) The compositions of Formulations 1 and 2 used in the following examples were as follows:

Formulation 1 Crisbon 8867 (Dainippon Ink and Chemicals, Inc.) 100.0 phr Dimethylformamide (Nitto Chemical Co., Ltd.) 200.0 phr The above crisbon 8867 has an average molecular weight of 200,000 and a cured product having a 100% modulus of 120 kg / cm. ^The main component is a polyester-based polyurethane.

Formulation 2 Hyprene L-315 (Mitsui Toatsu Chemical Co., Ltd.) 100.0 phr Iharacuamine (Ihara Chemical Co., Ltd.) 26.9 phr MEK 576.0 phr (Example 1) 6.0 denier, fiber length 60 mm A needle-punched nonwoven fabric made of polyester fiber and having a thickness of 2.0 mm, a bulk density of 0.11 g / cm ³ , and a basis weight of 350 g / cm ² was used as a substrate.

After the substrate was sufficiently immersed and impregnated with the above Formulation 1, it was immersed in a coagulating solution at 30 ° C. for 20 minutes in pure water, and then washed in pure water for 60 minutes to wet coagulate the thermoplastic polyurethane resin. After forming the felt base material in a porous shape, D
The MF was completely replaced with pure water, and further dried at 120 ° C. with hot air. The thickness was 1.7 mm, the bulk density was 0.23 g / cm ³ , the basis weight was 520 g / cm ² ,
A composite substrate having a urethane to fiber weight ratio of 0.5 to 1 was obtained. Grind the front and back of the composite base material with a 60 mesh baffle,
The dense skin layer was removed. The compression ratio of this sheet was 10%.

Further, after impregnating the sheet material with the impregnating solution of the above-mentioned formulation 2, the sheet material was dried with 120 ° C. hot air for 20 minutes to remove the solvent.
A polishing pad was obtained by curing the curable polyurethane of Formulation 2 while covering the cell walls of the polyurethane porous phase in the sheet material.

The front and back surfaces of the polishing pad were further buffed to obtain a polishing pad 1 having a flat working surface as shown in FIG. In the figure, reference numeral 2 denotes the working surface of the polishing pad 1;
Is a felt-like fibrous sheet, and 4 is an elastomer. This polishing pad had a thickness of 1.30 mm, a bulk density of 0.38 g / cm ³ , and a compressibility of 3.0%.

The processing accuracy of the wafer polished using the polishing pad was TTV: 0.5 μm, LTV: 0.3 μm, and the life of the polishing pad was 1951 hours.

(Example 2) 15.0 denier, polyester fiber having a fiber length of 60 mm, thickness 2.0 mm, bulk density 0.11 g
/ cm ^3, with a weight per unit area 360 g / cm ² of needle punched nonwoven as a substrate.

After sufficiently immersing and impregnating the base material with the above-mentioned composition 1, after immersing in a coagulating liquid at 30 ° C. for 20 minutes with pure water, 6
Rinse in pure water for 0 minutes, wet-solidify the thermoplastic polyurethane resin, form a felt base material in a porous form, completely replace DMF with pure water, and further dry with hot air at 120 ° C to a thickness of 1.7 mm, a bulk density of 0.23 g / cm ^3, a weight per unit area 520 g / c
A composite substrate with m ² and a urethane to fiber weight ratio of 0.5 to 1 was obtained.

The front and back surfaces of the composite substrate were ground with a 60-mesh baffle to remove a high-density skin layer. The compression ratio of this sheet was 10%.

Further, after impregnating the sheet material with the impregnating solution of the above-mentioned formulation 2, the sheet material was dried with hot air at 120 ° C for 20 minutes to remove the solvent.
The polishing pad was obtained by curing the thermosetting polyurethane of Formulation 2 while covering the cell walls of the polyurethane porous phase in the sheet material.

The front and back surfaces of the polishing pad were further buffed to obtain a polishing pad 1 having a flat working surface as shown in FIGS. On the surface of this polishing pad 1
A V-shaped groove 5 having a width of 2 mm and a depth of 3 mm was formed in a mesh at a pitch of 50 mm.

This polishing pad has a thickness of 1.30 mm and a bulk density of 1.30 mm.
The compression ratio was 0.38 g / cm ³ and the compression ratio was 3.0%.

The processing accuracy of the wafer polished using the polishing pad was TTV: 0.4 μm, LTV: 0.2 μm, and the life of the polishing pad was 2125 hours.

(Example 3) 10.0 denier, fiber length 60
2.2mm thick, bulk density made of mm polyester fiber
A needle-punched nonwoven fabric having a weight of 0.11 g / cm ³ and a basis weight of 300 g / cm ² was used as a substrate.

After sufficiently immersing and impregnating the base material with the above Formulation 1, immersing in a coagulating liquid at 30 ° C. for 20 minutes with pure water, washing with pure water for 60 minutes to wet coagulate the thermoplastic polyurethane resin. After forming the felt base material in a porous shape, D
The MF was completely replaced with pure water, further dried with hot air at 120 ° C., thickness 1.6 mm, bulk density 0.23 g / cm ³ , basis weight 520 g / cm ² ,
A composite substrate having a urethane to fiber weight ratio of 0.5 to 1 was obtained.

The surface (working surface) of the composite substrate is defined by a shear angle.
26 ° stainless steel blade, 6 ° rake angle, 1.
Grinding was performed at a cutting depth of 30 microns at 5 m / min. On the other hand, the back surface was ground with a 60-mesh baffle. These removed the dense skin layer. The compression ratio of this sheet was 10%.

Further, after impregnating the sheet material with the impregnating solution of the above-mentioned composition 2, drying with hot air at 120 ° C. for 20 minutes, and removing the solvent by drying, the thermosetting polyurethane of the above-mentioned composition 2 was mixed with the polyurethane in the composite base material. By curing while covering the cell walls of the porous phase, a polishing pad was obtained.

The back surface of the polishing pad was further buffed to obtain a polishing pad 1 having a flat working surface as shown in FIG. In the figure, reference numeral 2 denotes a working surface of the polishing pad 1, 3 denotes a felt-like fibrous sheet, and 4 denotes an elastomer. This polishing pad had a thickness of 1.27 mm, a bulk density of 0.39 g / cm ³ , and a compressibility of 2.8%.

The processing accuracy of the wafer polished using the polishing pad was TTV: 0.5 μm, LTV: 0.3 μm, and the life of the polishing pad was 2016 hours.

(Comparative Example) 3.0 denier, polyester fiber having a fiber length of 50 mm, a thickness of 2.5 mm, and a bulk density of 0.175 g /
A needle-punched nonwoven fabric having a cm ³ and a basis weight of 360 g / cm ² was used as a substrate.

After sufficiently immersing and impregnating the base material with the above-mentioned formulation 1, immersion in a coagulating solution of pure water at a temperature of 30 ° C. for 20 minutes, washing with pure water for 60 minutes, wet coagulation of the polyurethane resin, After the felt base material is formed, the DMF is completely replaced with pure water, and further dried with hot air at 120 ° C., thickness 1.8 mm, bulk density 0.3 g / cm ³ , basis weight 620 g / cm ² , urethane A composite substrate having a weight ratio of fiber to fiber of 0.9 to 1 was obtained.

The front and back surfaces of the composite substrate were ground with a 60-mesh baffle to remove a high-density skin layer. The compression ratio of this sheet was 12%.

Further, after impregnating the above-mentioned sheet material into the above-mentioned composition 2, it was dried with hot air at 120 ° C. for 20 minutes, and the solvent was removed by drying. By curing while covering the cell wall, a high hardness composite substrate was obtained.

A flat polishing pad obtained by further buffing the front and back surfaces of the composite base material has a thickness of 1.27 mm and a bulk density of
The compression ratio was 0.45 g / cm ³ and the compression ratio was 4.2%.

The processing accuracy of the wafer polished using the polishing pad was 1.0 μm for TTV and 0.8 μm for LTV, and the life of the polishing pad was 1300 hours. The target machining accuracy could not be achieved.

From the above results, it is clear that the polishing pad of this embodiment is a 4MDRAM, or a 64M or 256MD in the future.
Possesses physical properties suitable for manufacturing wafers for RAM, enables supply of highly flat wafers with LTV value of 0.3μ or less and PUA value of 95% or more, and short-term polishing ability due to clogging by polishing debris etc. Thus, there was provided a polishing pad that could have a longer life because it had no drawbacks.

[0069]

According to the polishing pad of the present invention, the felt-like fibrous sheet carrying a microporous elastomer mainly composed of polyurethane has 6.0 to 20.0 denier constituent fibers.
A basis weight of 150~600g / cm ² in fiber length 30 to 100 mm, since the rigidity is high, the ability to reduce the microporous elastomer supported amount to achieve the felt-like fibrous sheet in a predetermined compression rate, by the polishing debris Clogging is less likely to occur, the usable time of the polishing cloth is extended, and high flatness of the wafer surface can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a polishing pad of the present invention.

FIG. 2 is a plan view of another embodiment of the polishing pad of the present invention.

FIG. 3 is an enlarged sectional view of a main part of the polishing pad shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing pad 2 Working surface of polishing pad 3 Felt-like fibrous sheet 4 Elastomer 5 Groove

Claims (4)

[Claims] 1. A polishing pad comprising a felt-like fibrous sheet carrying a microporous elastomer mainly composed of polyurethane, wherein the fibers constituting the felt-like fibrous sheet are 6.0 to 6.0.
A polishing pad characterized by having a denier of 20.0, a fiber length of 30 to 100 mm, and a basis weight of the felt-like fibrous sheet of 150 to 600 g / cm ² . 2. A polishing pad obtained by impregnating a resin solution mainly composed of polyurethane into a felt-like fibrous sheet, and then wet-solidifying and drying the fiber-like sheet, wherein the fibers constituting the felt-like fibrous sheet are: 6.0-
A polishing pad characterized by having a denier of 20.0, a fiber length of 30 to 100 mm, and a basis weight of the felt-like fibrous sheet of 150 to 600 g / cm ² . 3. The difference between the maximum height and the minimum height of the polishing surface of the polishing pad is within 20 μm, and a 10-point average height R
3. The polishing pad according to claim 1, wherein a is within 12 μm. 4. The polishing pad according to claim 1, wherein a plurality of grooves are formed on a polishing surface of the polishing pad.