JPH074769B2 - Polishing cloth - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing cloth used for polishing semiconductor wafers, memory disks, lenses for optical components and the like.

[0002]

Conventionally, polishing using the mirror-polishing of the semiconductor wafer used as a substrate for forming an integrated circuit
As a cloth for use, a velor-like and suede-like fiber / resin composite material that is generally well known as artificial leather,
And, a polyurethane resin-impregnated wet coagulation-treated felt-like fibrous sheet has been widely used. However, especially in recent years
AM (Dynamic Random Access)
With respect to the circuit used as a memory, efforts are being made to increase the degree of integration, and accordingly, the flatness of the semiconductor wafer, which will be the substrate on which the circuit is formed, is increasing in order to reduce the line width between the circuits. The situation is getting tougher.

In response to such a demand, in the conventional mirror surface processing step of a semiconductor wafer, a polishing cloth used in a primary polishing step (stock removal process) that determines most of the flatness of the wafer is used. It has become clear that the flatness of the finished wafer is greatly influenced by the physical properties. That is, when a relatively soft polishing cloth is used, the roughness of the wafer surface is small and the number of scratches (scratches) is small, but the adverse effect on the flatness generally expressed by the term surface sag and edge sagging. Is likely to occur, and when a rigid polishing cloth is used, relatively good flatness can be obtained.

[0004]

SUMMARY OF THE INVENTION The most commonly used method for polishing semiconductor wafers at the present time, that is, polishing.
A method of polishing a surface of a workpiece by pressing a workpiece against a rotary polishing machine having a polishing cloth attached thereto and pressing the workpiece and supplying a polishing liquid containing mainly SiO ₂ fine particles as free abrasive grains. The processing pressure is applied to the work as a vertically evenly distributed load. Such a polishing cloth facing the work piece is required to have a function of sufficiently holding the polishing liquid, and the artificial leather-like porous fiber resin composite material is used. The uniform reaction force from the inside of the polishing cloth against the vertical evenly distributed load transmitted to the polishing cloth through the work piece and the polishing liquid film, and the above-mentioned propagating vertical evenly distributed load make the polishing cloth It is an important factor to prevent the surface sagging and the edge sagging of the wafer, and to improve the flatness of the wafer after polishing, that the wafer itself causes only small and uniform deformation.

Therefore, the polishing which was conventionally judged empirically
The softness or rigidity of the cloth for use should be judged by the magnitude of the stress against the compressive load and the magnitude of the deformation. As a material satisfying such an element, first, a single sheet of rubber or plastic is considered from the viewpoint of uniformity of material, but as a polishing cloth used for free abrasive grain polishing which is processed by a polishing liquid, It has a drawback that it has almost no holding power for the polishing liquid and cannot be used in practice. Next, various plastic foams are conceivable. However, all of them are too soft, too hard, or have high closed cell properties, so hard polyurethane foams are only used in some applications. Absent.
On the other hand, the artificial leather-like polishing cloth that has been conventionally used for polishing with such loose abrasive grains has a holding power for the polishing liquid,
In addition, it has been widely used for polishing semiconductor wafers for 64K or 256K DRAM as a suitable material from the viewpoint of stress and deformation with respect to compressive load.
When polishing M or a wafer for 4MDRAM in the future, the amount of deformation with respect to a compressive load is large, so that the processing pressure must be reduced to perform polishing for a long time, or the thickness of the polishing cloth itself must be reduced. As a result of reducing the amount of relative deformation, there are drawbacks such as a short life of the polishing cloth and the need to replace the polishing cloth after a short period of use.

Various attempts have been made to solve these drawbacks. For example, a sheet-like fiber base material is impregnated with a dimethylformamide (hereinafter referred to as DMF) solution of thermoplastic polyurethane, which is generally known as a wet coagulation method, and then water and DMF are replaced in a water bath. At the same time, in the conventionally known method of forming a polyurethane porous body in a fiber substrate, when the polyurethane solid substance in the thermoplastic polyurethane / DMF solution to be impregnated is increased, wet coagulation, washing, and drying steps are performed. Through,
The polishing cloth finally finished by removing the surface skin layer by buffing has a very uniform and dense structure,
Although the amount of deformation with respect to the compressive load is also small, when actually polishing a Si wafer using such a polishing cloth, polishing debris is clogged in the polishing cloth in a very short time, and further polishing can be performed. Disappear. Further, when a thermoplastic polyurethane having a higher hardness is used as the above-mentioned wet coagulation, the coagulation characteristics become non-uniform, and a large amount of variation in compression deformation occurs in one polishing cloth. . Furthermore, for the purpose of producing a uniform polishing cloth having a small amount of compressive deformation, a thermosetting urethane blepolymer and an organic solvent solution of a curing agent are directly impregnated into the sheet-shaped fiber base material and then dried in a drying oven. When solvent drying and urethane curing are performed at the same time, there is a drawback that resin migration occurs in the thickness direction of the fiber substrate in the time until drying and curing, and the amount of resin becomes uneven in the thickness direction of the polishing cloth. ing.

[0007]

The present invention solves the above-mentioned drawbacks and solves the problems of 1MDRAM and future 4MDRAM.
The present invention presents a polishing cloth such as a highly flat wafer mainly for semiconductor wafers.

The polishing cloth of the present invention is a felt-like fiber.
Constituent fibers in the quality sheet are linear thermoplastic polyurethane
The polymer mainly composed of resin is embedded in the
The composite base material is formed and the porous phase of the composite base material is formed.
The cell walls present in the
It is characterized by being covered and reinforced by a thin film of hard resin.
To collect .

The felt-like fibrous sheet used in the present invention
DM is nylon, polyester, aramid fiber, etc.
A nonwoven fabric made of fibers having resistance to polyurethane-soluble solvents such as F, methyl ethyl ketone (hereinafter referred to as MEK), and tetrahydrofuran, and having alkali resistance to a polishing liquid having a pH of about 10 to 11 used at the time of polishing, preferably Is a needle-punched non-woven fabric containing no binder and has a bulk density of 0.10 g / cm ^{3 to} 0.20 g.
Those in the range of / cm ³ are preferable. For polishing of the present invention
The cloth is manufactured by impregnating such a sheet-like fiber base material with a DMF solution of a polyester-based or polyether-based thermoplastic polyurethane, followed by wet coagulation to obtain an intermediate composite material. It comprises a primary treatment step of preparing a substrate and a secondary treatment step of treating the composite substrate with a thermosetting polyurethane or the like. These will be described below step by step.

As the thermoplastic polyurethane used for the primary treatment, any of those generally commercially available for artificial leather can be used, but for this purpose, preferably 100
It is preferable that the modulus at% elongation is 100 kg / cm ² or more. What is more important in this step is what is the weight ratio of the resin phase to the fiber phase in the composite substrate formed through the steps of wet coagulation, washing and drying. For example, when the ratio (resin relative fiber phase) exceeds 1: 1 the porous structure due to wet coagulation existing in the resin phase of the composite base material becomes dense, and the heat of the secondary treatment continuously performed. Since a considerable amount of pores are filled with the curable polyurethane, when used for polishing, the flow of the polishing liquid and polishing debris is obstructed, and clogging occurs in a short time. On the contrary, when the ratio of the resin relative fiber phase is less than 1: 5, the resin phase only surrounds the entanglement points of the fibers and the outer peripheral portion, and the solvent solution of the thermosetting polyurethane used in the next secondary treatment. Migrates in the process of drying and curing, and is localized on the side that was the lower side during drying. Therefore, in this primary treatment step, the solid content of the thermoplastic polyurethane to be impregnated in the DMF solution is adjusted according to the bulk density of the sheet-shaped fiber base material to be used, and the resin relative fiber phase in the intermediate composite base material to be completed is adjusted. It is preferable that the ratio is 1: 1 to 1: 5. The intermediate base material created through such wet coagulation, washing, and drying is
Since there is a dense foam layer called a skin layer near the surface, both the front surface and the back surface are removed so that the impregnating liquid for the secondary treatment that is continuously carried out can be uniformly and quickly penetrated.

The intermediate substrate thus prepared is subsequently subjected to a secondary treatment. The impregnating liquid used in this process is polyester or polyether MDI.
(Methylene diisocyanate), a urethane prepolymer having TDI (tolylene diisocyanate) ends, or a blend of melamine resin, polycarbonate resin, etc. for adjusting the hardness and compressibility of the polishing cloth. A bifunctional organic amine curing agent such as dichloro-4,4'diaminophenylmethane, and, if necessary, an accelerator mainly containing a dicarboxylic acid such as adipic acid, in an organic solvent solution, which has a thermal efficiency of drying. When considering, it is desirable to use a solvent having a relatively low boiling point such as MEK.

In this secondary treatment step, the thermosetting polyurethane compounding liquid permeates the porous phase in the intermediate composite base material, loses the solvent component by drying in the furnace, and becomes a viscous liquid. The walls of the cells that are present at are evenly coated. Subsequent heating causes the urethane curing reaction, and the three-dimensionally crosslinked thermosetting polyurethane thin film covers and reinforces the cell wall of the thermoplastic polyurethane formed by the primary treatment.

Also in this step, the solid content of the thermosetting polyurethane compounding liquid used as the secondary treatment is important, and when the amount is too large, the pores formed in the primary treatment also become the secondary treatment liquid. If it is too low, the reinforcing effect is low and the physical properties of the intermediate composite base material are not so different. Therefore, in this secondary treatment, the weight ratio of the thermosetting polyurethane after drying / curing to the thermoplastic polyurethane contained in the intermediate composite base material is 1: 3 to 1: 1.
Rukoto is controlled in the range of: 1 is preferred.

According to the polishing cloth of the present invention, the felt
The constituent fibers in the fibrous sheet are linear thermoplastic
The polymer mainly composed of retin resin is embedded in the surrounding area.
Walls present in the porous phase of the composite substrate formed by
However, a thin resin film that is harder than thermoplastic polyurethane resin
Because it is more covered and reinforced, the pores of the porous cell are larger.
In the thickness direction of the polishing cloth without reducing the width
The amount of compressive deformation can be reduced.

That is, the porous material present in the polishing cloth
Structure in which the cell wall is covered and reinforced with a hard resin thin film
Has a significantly lower porosity (density) of the polishing cloth.
Its compression modulus can be increased without lowering
It

The polishing cloth and its polishing performance will be described in more detail with reference to the following examples, but these examples do not limit the basic part of the present invention.

[0017]

【Example】

Example 1 A needle bunch nonwoven fabric having a thickness of 2 mm, a bulk density of 0.13 g / cm ³ , and a basis weight of 260 g / m ² , which is made of polyester fiber having a denier of 3.0 mm and a fiber length of 50 mm, is used as a base material,
Molecular weight 200,000, 100% modulus 120kg
After fully impregnating and impregnating the base material with a DMF solution having a solid content of 13% of polyester-based polyurethane (trade name: Crisbon 8867) of 10 / cm ² , the ratio of DMF to pure water is 10: 9.
After immersing in a coagulating liquid at 0 and a temperature of 30 ° C. for 20 minutes, 60
After rinsing in pure water for a minute, the polyurethane resin is wet-coagulated and the felt base material is surrounded in a porous form, then DMF is completely replaced with pure water and further dried with hot air at 120 ° C, thickness 2 mm, bulk density 0.26 g / cm ^3, a weight per unit area 520 g / m
^2. A composite substrate with a urethane to fiber weight ratio of 0.9: 1 was obtained. The front and back surfaces of the base material were ground with a 60 mesh buff roll to remove the skin layer having a high density. The hardness of this sheet was 60 degrees according to JIS A, and the compression rate was 30%. The sheet material was dipped and impregnated in a secondary impregnating solution having the following composition, dried with hot air at 120 ° C. for 20 minutes, and the solvent was completely dried and removed to give the thermosetting polyurethane as a polyurethane porous phase in the composite substrate. A high hardness composite substrate was obtained by curing while covering the cell wall of.

A flat high hardness composite base material obtained by buffing the front and back surfaces of this composite base material has a thickness of 1.27 mm and a bulk density of 0.
36 g / cm ³ , hardness JISA 85 degrees, compression rate 6.0%,
Fiber to primary resin to secondary resin ratio of 1 to 0.9 to 0.9
Met. The flatness of the wafer polished by this high hardness composite substrate was good, and the life of the polishing cloth was 60 hours.

Blending Example of Secondary Impregnation Solution: Hibrene L-315 (trade name of Mitsui Toatsu Chemicals, Inc.) 100.0 parts Iharacuamine MT (trade name of Ihara Chemicals Co., Ltd.) 26.9 parts MEK 576. 0 part Total 702.9 parts [Hybrene L-315] Polyol component: Polytetramethylene ether glycol Isocyanate component: 2,4-toluene diisocyanate [Iharacuamine MT] 3,3′-dichloro-4,4′-diaminophenylmethane (Example 2) 3.0 denier fiber length 60 mm polyester fiber,
A needle-punched nonwoven fabric having a thickness of 2 mm, a bulk density of 0.15 g / cm ³ , and a basis weight of 300 g / m ² , which is composed of 80 to 20 of heat-shrinkable polyester fiber having a denier of 50 mm and a length of 50 mm, is used as a base material. , Molecular weight 200,000, 10
After thoroughly impregnating the base material with a DMF solution having a solid content of 11% of a polyester polyurethane resin having a 0% modulus of 120 kg / cm ² (trade name: Crisbon 8867, manufactured by Dainippon Ink & Co., Inc.) The ratio is 20:80,
Further, after immersing in a coagulating liquid at a temperature of 35 ° C. for 20 minutes, washing in pure water for 60 minutes to wet-coagulate the polyurethane resin and surrounding the felt base material in a porous form, DMF is completely replaced with pure water. Further dried with hot air at 120 ° C, thickness 2m
m, bulk density 0.26 g / cm ³ , basis weight 520 g /
A composite substrate with m ² and a urethane to fiber weight ratio of 0.6 to 1 was obtained. The front and back surfaces of the base material were ground with 80 mesh baffle to remove the skin layer having a high density. The hardness of this sheet was 52 degrees according to JIS A, and the compression rate was 33%. The sheet material was dipped and impregnated in a secondary impregnating solution having the following composition, dried with hot air at 120 ° C. for 20 minutes, and the solvent was completely dried and removed to give the thermosetting polyurethane as a polyurethane porous phase in the composite substrate. A high hardness composite substrate was obtained by curing while covering the cell wall of. A flat high-hardness composite substrate obtained by buffing the front and back surfaces of this composite substrate has a thickness of 1.27 mm, a bulk density of 0.34 g / cm ³ , and a hardness of JIS A8
The compression ratio was 0 degree, the compression ratio was 6.5%, and the ratio of the fiber to the primary resin to the secondary resin was 1: 0.6: 0.5. The flatness of the silicon wafer polished by this high hardness composite substrate is good,
The life of the polishing cloth was 100 hours. The formulation example of the secondary impregnation liquid is the same as in Example 1. Example 3 A needle punched non-woven fabric having a thickness of 2 mm, a bulk density of 0.20 g / cm ³ , and a basis weight of 400 g / m ² , which is composed of a polyester fiber having a 3.0 denier fiber length of 75 mm, is used as a base material and has a molecular weight of 200. 1,000, 100% modulus 120kg / cm
² % polyester type polyurethane resin (Dai Nippon Ink Co., Ltd. product name: Chris Bon 8867) with a solid content of 9%
After sufficiently dipping and impregnating the base material with the MF solution, the polyurethane resin is wet-coagulated into a porous form by immersing it in a coagulating liquid having a DMF to pure water ratio of 25% to 75% and a temperature of 30 ° C. for 20 minutes. After that, it was washed in pure water for 60 minutes to completely replace DMF with pure water, and further dried with hot air at 120 ° C. to have a thickness of 2 mm, a bulk density of 0.30 g / cm ³ , and a basis weight of 600 g /
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 base material were ground with 80 mesh baffle to remove the skin layer having a high density. The hardness of this sheet was 65 degrees according to JIS A, and the compression rate was 22%. The sheet material was dipped and impregnated in a secondary impregnation solution having the following composition, dried with hot air at 120 ° C. for 20 minutes, and the solvent was completely dried and removed to give the thermosetting polyurethane as a polyurethane porous material in the composite substrate. A high hardness composite base material was obtained by curing while coating the cell walls of the matrix. A flat high-hardness composite base material obtained by buffing the front and back surfaces of this composite base material has a thickness of 1.27 mm, a bulk density of 0.35 g / cm ³ , and a hardness of JIS A8.
Twice, the compressibility was 60%, and the ratio of fiber to primary resin to secondary resin was 1: 0.5: 0.3. The flatness of the silicon wafer polished by this high hardness composite substrate was good, and the life of the polishing cloth was 130 hours. The formulation example of the secondary impregnation liquid is the same as in Example 1. (Example 4) 3.0 denier polyester fiber having a fiber length of 60 mm,
Based on a needle punched non-woven fabric with a thickness of 2 mm, a bulk density of 0.15 g / cm ³ and a basis weight of 300 g / m ² , which is composed of heat-shrinkable polyester fibers having a ratio of 2.5 denier and a fiber length of 50 mm of 80 to 20. Material, molecular weight 200,000, 1
After sufficiently dipping and impregnating the base material with a DMF solution having a solid content of 11% of a polyester polyurethane resin having a 00% modulus of 120 g / cm ² , the ratio of DMF to pure water is 20:80.
At a temperature of 35 ° C. for 20 minutes to wet-solidify the polyurethane resin into a porous form, and then 60
After washing in pure water for 1 minute, DMF is completely replaced with pure water, and further dried with hot air at 120 ° C to a thickness of 2 mm and a bulk density of 0.26.
A composite base material having a g / cm ² , a basis weight of 520 g / m ² , and a urethane to fiber weight ratio of 0.6 to 1 was obtained. 80 the substrate
The front and back surfaces were ground with a mesh baffle to remove the dense skin layer. The hardness of this sheet was 58 degrees according to JIS A, and the compression rate was 33%. The sheet material was dipped and impregnated in a secondary impregnation liquid having the following composition, and then dried with hot air at 120 ° C. for 20 minutes to completely dry and remove the solvent, and the thermosetting polyurethane was used as the polyurethane porous material in the composite substrate. A high hardness composite substrate was obtained by curing while covering the cell walls in the layer. A flat high hardness composite base material obtained by further buffing this composite base material on the front and back sides has a thickness of 1.27 mm and a bulk density of 0.
35 g / cm ³ , hardness JISA 85 degrees, compression rate 5.0%,
The ratio of fiber to primary resin to secondary resin is 1 to 0.6 to 0.5.
Met. The flatness of the silicon wafer polished by this high hardness composite substrate was particularly good, and the life of the polishing cloth was 95 hours.

Blending Example of Secondary Impregnation Solution: Vibrasen B-803 (Uniroyal Inc. trade name) 100.0 parts Iharacuamine MT (Ihara Chemical Co., Ltd. trade name) 32.9 parts MEK 605.0 parts Total 737.9 parts (Example 5) 3.0 denier polyester fiber having a fiber length of 60 mm,
Based on a needle punched non-woven fabric with a thickness of 2 mm, a bulk density of 0.15 g / cm ³ and a basis weight of 300 g / m ² , which is composed of heat-shrinkable polyester fibers having a ratio of 2.5 denier and a fiber length of 50 mm of 80 to 20. Material, molecular weight 250,000, 1
Solid content 9% of polyester polyurethane resin (Sambrene LQ3700) with a 00% modulus of 180 g / cm ²
After sufficiently dipping and soaking the substrate in the DMF solution of, the DMF to pure water is immersed in a coagulating liquid having a ratio of DMF to pure water of 20 to 80 and a temperature of 35 ° C. for 20 minutes to wet-coagulate the polyurethane resin in a porous form. After that, it was washed in pure water for 60 minutes to completely replace DMF with pure water, and further dried with hot air at 120 ° C. to have a thickness of 2 mm, a bulk density of 0.26 g / cm ² , and a basis weight of 520 g /
A composite substrate with m ² and a urethane to fiber weight ratio of 0.6 to 1 was obtained. The front and back surfaces of the base material were ground with 80 mesh baffle to remove the skin layer having a high density. The hardness of this sheet was 65 degrees according to JIS A, and the compression rate was 22%. After dipping and impregnating the sheet material with the secondary impregnation liquid of Example 1,
Drying with hot air at 120 ° C. for 20 minutes to completely remove the solvent, and curing the thermosetting polyurethane while coating the cell walls in the polyurethane porous layer in the composite substrate, to obtain a high hardness composite. A base material was obtained. A flat high-hardness composite substrate obtained by buffing the front and back surfaces of this composite substrate has a thickness of 1.27 mm, a bulk density of 0.35 g / cm ³ , and a hardness of JIS A8
Twice, the compressibility was 5.6%, and the ratio of fiber to primary resin to secondary resin was 1: 0.6: 0.5. The flatness of the silicon wafer polished by this high hardness composite substrate is good,
The life of the polishing cloth was 110 hours. (Comparative Example 1) 3.0 denier polyester fiber having a fiber length of 60 mm,
Based on a needle punched non-woven fabric having a thickness of 2 mm, a bulk density of 0.175 g / cm ³ and a basis weight of 350 g / m ² , which is composed of a heat-shrinkable polyester fiber having a ratio of 2.5 denier and a fiber length of 50 mm of 80 to 20. Material, molecular weight 300,000,
After thoroughly impregnating the base material with a DMF solution having a solid content of 15% of a 100% modulus 240 g / cm ² polyester-based polyurethane resin (Dainippon Ink and Co., Ltd., trade name: Crisbon 8966), the substrate was treated with DMF and pure water. 20:80 ratio
At a temperature of 35 ° C. for 20 minutes to wet-solidify the polyurethane resin into a porous form, and then 60
After washing in pure water for a minute, DMF is completely replaced with pure water and further dried with hot air at 120 ° C. to have a thickness of 2 mm and a bulk density of 0.30.
A composite base material having a weight per unit area of g / cm ² , a weight per unit area of 600 g / m ² , and a weight ratio of urethane to fiber of 0.8: 1 was obtained. 80 the substrate
The front and back surfaces were ground with a mesh baffle to remove the dense skin layer. The hardness of this sheet was 72 degrees according to JIS A, and the compression rate was 11%. The flatness of the silicon wafer polished by this composite substrate has a large surface sag,
It was not good.

The polishing cloth of this embodiment is 1MD in recent years.
For manufacturing RAM or wafers for future 4MDRAM
Possessing suitable physical properties, LTV value of 0.8μ or less, PU
It becomes possible to supply highly flat wafers with an A value of 95% or more.
Not only the polishing ability due to clogging by polishing debris etc.
To provide a polishing cloth that does not have the drawback that
I was able to. Furthermore, as a side effect, a polishing cloth is used.
Since it has a long life, it is frequently replaced with a new polishing cloth.
Was much less.

[0022]

The polishing cloth of the present invention is a polishing cloth.
The walls of the porous cells present in the wall are covered with a hard resin thin film
・ Porosity of polishing cloth due to reinforced structure
Its compressive modulus can be reduced without significantly reducing (density)
Since it can be made higher, it holds the machining fluid and machining chips.
The polishing cloth can be maintained without lowering the space
Avoids clogging in a short time and making polishing impossible
Can be done at the same time as polishing rate (production efficiency), polishing
Reduced cloth usable time (work efficiency and production cost)
High surface flatness of the work piece can be achieved without
It

Claims (5)

[Claims] 1. Constituent fibers in a felt-like fibrous sheet
Is a polymer based on linear thermoplastic polyurethane resin
When the body is embedded and surrounded to form a composite substrate
Both are the walls of the cells present in the porous phase of the composite substrate
However, a thin resin film that is harder than thermoplastic polyurethane resin
Polishing black characterized by being more covered and reinforced
Su . 2. A heat which can cure the composite substrate comprising the thermoplastic polyurethane and the felt-like fibrous sheet described above with an organic amine compound such as 3,3′dichloro-4,4′diaminodiphenylmethane as a secondary treatment. A curable polyurethane and an organic amine compound as a curing agent for the polyurethane are impregnated with a solvent solution and heated to a temperature equal to or higher than the reaction temperature of the curing agent to evaporate and remove the solvent. polishing black of that cause the curing reaction thus according to claim 1 to be manufactured
Su . 3. A heat which can cure the composite base material comprising the thermoplastic polyurethane and the felt-like fibrous sheet as described above as a secondary treatment with an organic amine compound such as 3,3′dichloro-4,4′diaminodiphenylmethane. Curable polyurethane and melamine resin, impregnated with a solvent solution in which a resin obtained by blending a resin such as a polycarbonate resin and a curing agent for the polyurethane is dissolved, and heated at a temperature equal to or higher than the reaction temperature of the curing agent, At the same time the solvent is evaporated to remove, Ken according to claim 1, wherein the thus produced to cause the curing reaction of polyurethane
Polishing cloth . 4. The composite base material comprising the thermoplastic polyurethane and the felt-like fibrous sheet as described above, wherein the weight ratio of polyurethane to fiber is in the range of 1 to 5 to 1: 1. Any of claims 1 to 3 manufactured by
A polishing cloth as described therein . 5. A thermoplastic polyurethane used to form the composite substrate, and the composite substrate further impregnated, dried,
The secondary treatment impregnating resin for curing has a weight ratio of 1: 3 to 1
Ken according to any one of claims 2 to 4, such as in-one
Polishing cloth .