JP2020157431A - Polishing pad, method for producing polishing pad, method for polishing surface of optical material or semiconductor material, and method for evaluating polishing pad - Google Patents

Abstract

To provide a polishing pad which suppresses polishing scratches, is less in fluctuation of a polishing rate during polishing, and is excellent in polishing stability.SOLUTION: A polishing pad has a polishing layer containing a polyurethane resin, in which when a free induction decay signal (FID) obtained by pulse NMR is deducted in order from a long component of a spin-spin relaxation time T2 by a least square method, is subjected to waveform separation and thereby is divided into three components of an amorphous phase, an interface phase and a crystal phase in order from the long spin-spin relaxation time T2, the polishing layer has a content ratio ((Ac20) of the component of the crystal phase at 20°C of 10-20%, and a content ratio (Ai20) of the component of the interface phase at 20°C of 40-50%.SELECTED DRAWING: Figure 5

Description

The present invention relates to a polishing pad, a method for manufacturing a polishing pad, a method for polishing the surface of an optical material or a semiconductor material, and a method for evaluating a polishing pad. The polishing pad of the present invention is used for polishing optical materials, semiconductor wafers, semiconductor devices, substrates for hard disks, etc., and is particularly suitable for polishing devices in which an oxide layer, a metal layer, etc. are formed on a semiconductor wafer. Used for.

In recent years, with the use of multi-layer wiring on the surface of a semiconductor substrate, a so-called chemical mechanical polishing (CMP) technique, in which a semiconductor substrate is polished and flattened when manufacturing a device, has been used. CMP is a method of flattening the surface of an object to be polished (object to be polished) such as a semiconductor substrate by using a polishing composition (slurry) containing abrasive grains such as silica, an anticorrosive agent, and a surfactant. The object to be polished (object to be polished) is silicon, polysilicon, silicon oxide film, silicon nitride, wiring made of metal or the like, a plug, or the like.

In the CMP process, a large amount of impurities are generated on the surface of the semiconductor substrate. Impurities are generated by polishing abrasive grains, metals, anticorrosive agents, organic substances such as surfactants, silicon-containing materials to be polished, metal wiring, plugs, etc., which are derived from the polishing composition used in CMP. It also contains silicon-containing materials and metals, as well as organic substances such as pad scraps generated from various pads and the like, and remains as inorganic particles and organic residues. If the surface of the semiconductor substrate is contaminated with these impurities, the electrical characteristics of the semiconductor may be adversely affected and the reliability of the device may be reduced. In particular, the low dielectric constant interlayer insulating film to be polished is highly hydrophobic, and impurities are easily adsorbed by the hydrophobic interaction. Therefore, the polishing pad used in CMP is required to reduce the inorganic particles and organic residues remaining on the surface of the semiconductor substrate by polishing.

Further, the CMP step includes rough polishing for the purpose of adjusting the flatness and finish polishing for the purpose of improving the surface roughness.

Patent Document 1 discloses that as a polishing pad for finishing the surface of a device, a soft suede pad that is less likely to cause polishing scratches such as scratches is preferably used.

JP-A-2010-149259

In finish polishing with a finishing polishing pad as disclosed in Patent Document 1, there is a demand for a pad that does not damage the object to be polished and has a small fluctuation in the polishing rate during polishing. In particular, there is a great need for a pad that has a small fluctuation in the polishing rate from the initial stage of polishing, and there is a demand for a polishing pad for finishing that enables stable polishing immediately after the start of polishing.

An object of the present invention is to provide a polishing pad that suppresses polishing scratches, has little fluctuation in the polishing rate during polishing, and has excellent polishing stability.

As a result of diligent research to solve the above problems, the present inventors have performed polishing in which the content ratio of the component of the crystal phase (Ac ₂₀ ) and the content ratio of the component of the interface phase (Ai ₂₀ ) at 20 ° C. are within a specific range. It has been found that the above problems can be solved by using layers, and the present invention has been completed. Specific embodiments of the present invention are as follows.

[1] A polishing pad having a polishing layer containing a polyurethane resin.
In the polishing layer, the free induction decay signal (FID) obtained by pulse NMR is subtracted in order from the component having the longest spin-spin relaxation time T2 by the minimum square method, and the waveform is separated to obtain the longer spin-spin relaxation time T2. When divided into three components, an amorphous phase, an interfacial phase, and a crystalline phase, the content ratio (Ac ₂₀ ) of the crystalline phase component at 20 ° C. is 10 to 20%, and the interfacial phase component at 20 ° C. The polishing pad having a content ratio (Ai ₂₀ ) of 40 to 50%.
[2] The absolute value (| Ai _20- Ai ₄₀ |) of the difference between the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai ₄₀ ) is 35 to 5. The polishing pad according to [1], which is 50.
[3] The polishing pad according to [1] or [2], wherein the polishing layer has an A hardness of 5 to 15.
[4] The polishing pad according to any one of [1] to [3], wherein the polishing layer has a compressibility of 35 to 65%.
[5] The method for manufacturing a polishing pad according to any one of [1] to [4], which comprises a step of using a wet film forming method.
[6] The method for polishing the surface of an optical material or a semiconductor material, which comprises a step of using the polishing pad according to any one of [1] to [4].
[7] A method for evaluating a polishing pad having a polishing layer containing a polyurethane resin.
For the polishing layer, the free induction decay signal (FID) obtained by pulse NMR is subtracted in order from the component having the longest spin-spin relaxation time T2 by the minimum square method, and the waveform is separated to obtain the longer spin-spin relaxation time T2. When divided into three components, an amorphous phase, an interface phase, and a crystalline phase, the content ratio (Ac ₂₀ ) of the component of the crystal phase at 20 ° C. is 10 to 20%, and the component of the interface phase at 20 ° C. The evaluation method including a step of confirming whether or not the content ratio (Ai ₂₀ ) is 40 to 50%.
[8] The absolute value (| Ai _20- Ai ₄₀ |) of the difference between the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai ₄₀ ) is 35 to 5. The evaluation method according to [7], further comprising a step of confirming whether or not the value is 50.

The polishing pad of the present invention can suppress polishing scratches, has little fluctuation in the polishing rate during polishing, and is excellent in polishing stability.

It is a figure explaining the structure analysis method of the polishing pad by pulse NMR. It is a schematic diagram which shows an example of the apparatus which performs the steps of coating, solidification regeneration, cleaning / drying in the manufacturing process of the polishing pad of this invention. It is a figure which shows the cross-sectional view of an example of the polishing pad of this invention. It is a figure explaining the polishing method of the object to be polished using the polishing pad of this invention. It is a graph which shows the result (relaxation time of each component) of the structural analysis by the pulse NMR of the polishing pad obtained in Example 1 and Comparative Examples 1-3. It is a graph which shows the result (content ratio of each component) of the structural analysis by the pulse NMR of the polishing pad obtained in Example 1 and Comparative Example 1. It is a graph which shows the result (content ratio of each component) of the structural analysis by the pulse NMR of the polishing pad obtained in Comparative Examples 2 and 3. It is a photograph which shows the cross section of the polishing pad obtained in Example 1 and Comparative Example 1. It is a photograph which shows the cross section of the polishing pad obtained in Comparative Examples 2 and 3.

(Action)
In the present invention, as the polishing layer, the content ratio of the crystal phase component (Ac ₂₀ ) at 20 ° C. is 10 to 20%, and the content ratio of the interface phase component (Ai ₂₀ ) at 20 ° C. is 40 to 50%. Use something.

Unexpectedly, the present inventors have a crystal phase component content ratio (Ac ₂₀ ) at 20 ° C. of 10 to 20%, and an interface phase component content ratio (Ai ₂₀ ) at 20 ° C. of 40 to 50. It has been found that by using the polishing layer of%, polishing scratches are suppressed, the fluctuation of the polishing rate during polishing is small, and a polishing pad having excellent polishing stability can be obtained. The details of the reason why these characteristics are obtained are not clear, but it is inferred as follows.

The content ratio of the crystal phase component at 20 ° C. (Ac ₂₀ ) corresponds to the content ratio of the crystal phase component at the initial stage of polishing at room temperature (about 20 ° C.), and the content ratio of the crystal phase component is the polyurethane resin. It is considered to mean the ratio of the hard segment component in. Further, the content ratio of the interface phase component (Ai ₂₀ ) at 20 ° C. corresponds to the content ratio of the interface phase component at the initial stage of polishing at room temperature (about 20 ° C.), and the interface phase content ratio is the polyurethane resin. It is considered to mean a molecular chain whose movement is restricted to some extent within. The polyurethane resin in the polishing pad of the present invention has a relatively low content of hard segment components and a relatively high proportion of molecular chains whose movement is restricted to some extent, so that it has appropriate elasticity and self-dressing property (self-dressing property). (Self-disintegrating property) is excellent, and as a result, the polishing rate does not fluctuate during polishing, the polishing stability is excellent, and polishing scratches can be suppressed.

(Structural analysis by pulse NMR)
In pulse NMR, a FID signal having excellent quantification can be obtained by detecting a response signal to a pulse. Therefore, the phase-separated structure of the polyurethane resin can be analyzed. The initial value of the FID signal is proportional to the number of protons in the measurement sample, and if the measurement sample has a plurality of components, the FID signal is the sum of the response signals of each component. If there is a difference in the motility of each component, the speed of attenuation of the response signal is different and the spin-spin relaxation time T2 is different. Therefore, it is necessary to separate these and obtain the relaxation time T2 and the component ratio R of each component. it can. The smaller the motility of the component, the shorter the relaxation time T2, and the larger the motility, the longer the relaxation time T2. In other words, the shorter the relaxation time T2, the greater the crystallinity, and the longer the relaxation time T2, the greater the amorphousness.

As shown in FIG. 1, the FID signal obtained by pulse NMR of the polyurethane resin is shown by the curve D. By subtracting from the curve D in order from the component having the longest relaxation time T2 by the least squares method and separating the waveforms, it can be divided into the three components shown by the curve H, the curve S, and the curve I. The component having a long relaxation time T2 shown by the curve S corresponds to the amorphous phase, and the component having a short relaxation time T2 shown by the curve H corresponds to the crystalline phase. The component represented by the curve I between the curve S and the curve H corresponds to the interface phase. In the polyurethane resin, the component ratio of the amorphous phase formed by the soft segment having high motility correlates with the compressive elastic modulus, and the component ratio of the crystalline phase formed by the hard segment having low motility correlates with the A hardness. Therefore, the compressive elastic modulus can be increased by increasing the component ratio of the amorphous phase, and the A hardness can be increased by increasing the component ratio of the crystalline phase.

Hereinafter, the polishing pad of the present invention, a method for manufacturing the polishing pad, a method for polishing the surface of an optical material or a semiconductor material, and a method for evaluating the polishing pad will be described.
In the present specification and the claims, when the numerical range is expressed by using "A to B", the range shall include A and B which are the numerical values at both ends.

(Polishing pad)
The polishing pad of the present invention is a polishing pad having a polishing layer containing a polyurethane resin, and the polishing layer obtains a free induction decay signal (FID) obtained by pulse NMR by a minimum square method and has a spin-spin relaxation time T2. By subtracting the components in order from the longest component and separating the waveforms, the components of the crystalline phase at 20 ° C. are contained when the spin-spin relaxation time T2 is divided into three components in order from the longest component: amorphous phase, interface phase, and crystalline phase. The ratio (Ac ₂₀ ) is 10 to 20%, and the content ratio (Ai ₂₀ ) of the interface phase component at 20 ° C. is 40 to 50%.
Ac ₂₀ is 10 to 20%, preferably 10 to 18%, more preferably 10 to 17%. Ai ₂₀ is 40 to 50%, preferably 41 to 49%, more preferably 42 to 48%. When Ac ₂₀ and Ai ₂₀ are within the above numerical range, polishing scratches can be suppressed, the fluctuation of the polishing rate during polishing is small, and a polishing pad having excellent polishing stability can be obtained.

The polyurethane resin (polishing layer) in which Ac ₂₀ is 10 to 20% can be obtained by reducing the 100% resin modulus (MPa) of the polyurethane resin used for the polishing layer. The 100% resin modulus of the polyurethane resin contained in the polishing layer is preferably 1.0 to 5.0 MPa, more preferably 1.5 to 4.0 MPa, and most preferably 1.8 to 3.5 MPa. The 100% resin modulus of polyurethane resin is an index showing the hardness of the resin, and the load applied when the non-foamed resin sheet is stretched 100% (when stretched to twice the original length) is the cross-sectional area. It is the divided value. For 100% resin modulus, a resin solution is thinly stretched and dried with hot air to prepare a dry film having a thickness of about 200 μm, and after curing for a while, the total length is 90 mm, the width at both ends is 20 mm, the distance between grippers is 50 mm, and the width of parallel parts is 10 mm. The sample is punched into a dumbbell shape with a thickness of 200 μm, and the measurement sample is sandwiched between the upper and lower air chucks of the universal material tester Tencilon (Tencilon universal tester "RTC-1210" manufactured by A & D Co., Ltd.) and 20 ° C (± 2). ℃), humidity 65% (± 5%), pulling at a pulling speed of 100 mm / min, and dividing the tension at 100% elongation (double stretching) by the initial cross-sectional area of the sample. To measure the resin modulus, a polyurethane foam sheet is dissolved in N, N-dimethylformamide (DMF) to obtain a low-concentration polyurethane resin DMF solution, and then the DMF is vaporized by a casting method to obtain a non-foamed resin sheet. It can also be measured by forming.
The weight average molecular weight of the polyurethane resin contained in the polishing layer is preferably 100,000 to 200,000, more preferably 11,000 to 160,000, and most preferably 12,000 to 14,000. The weight average molecular weight of the polyurethane resin can be measured by gel permeation chromatography (GPC) described later.

The content ratio of the components of the interface phase can be adjusted by adjusting the composition of the thermoplastic polyurethane resin, that is, the type and molecular weight of the polymer diol, the type of diisocyanate, the amount of the chain extender and the terminal encapsulant, or these polymers. By adjusting the compounding molar ratio of the diol, the polyisocyanate, and the chain extender, it can be produced in an appropriate range. For example, by bringing the polarities of the hard segment and the soft segment closer to each other, phase separation is less likely to proceed and the number of interface phases can be increased.

The polishing pad of the present invention has an absolute value (| Ai _20- Ai ₄₀ |) of the difference between the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai ₄₀ ). ) Is preferably 35 to 50, more preferably 36 to 48, and most preferably 37 to 46.
When | Ai ₂₀ −Ai ₄₀ | is within the above numerical range, it is considered that a polishing pad having the following effects can be obtained.
Regarding polishing with a polishing pad, the temperature of the polishing surface of the polishing pad at the beginning of polishing is around room temperature (about 20 ° C), but the temperature of the polishing surface from the middle to the latter stage of polishing is around 40 ° C due to frictional heat and the like. Ascend to. When the temperature of the polished surface of the polishing pad rises as the polishing progresses, it is considered that a part of the molecular chain constrained as the interface phase is released and becomes an amorphous phase component that freely moves. In the present invention, | Ai ₂₀ −Ai ₄₀ | is relatively large, and it is considered that most of the interface phase becomes an amorphous phase component as the temperature rises from 20 ° C. to 40 ° C. Therefore, in a state where polishing heat is generated by the polishing process (about 40 ° C.), the softness of the polishing pad is increased, and the force of pressing the polishing agglomerates composed of polishing scraps, pad scraps, slurry components, etc. against the object to be polished is exerted. Since it can be weakened, it is considered that the polishing scratch suppressing effect is large on the easily scratched surface. Further, in the present invention, since the content ratio of the interface phase at 20 ° C. is relatively high, the dressing property of the polishing layer is improved and the polishing rate changes with time when dressing is usually performed at room temperature (about 20 ° C.). It is thought to be suppressed.

Ai ₄₀ is preferably 1 to 10%, more preferably 2 to 8%, and most preferably 3 to 7%.

The content ratio of the amorphous phase component at 20 ° C. is preferably 25 to 60%, more preferably 30 to 50%, and most preferably 35 to 45%.
The relaxation time of the amorphous phase component at 20 ° C. is preferably 800 to 1300 μs, more preferably 900 to 1250 μs, and most preferably 1000 to 1200 μs. The relaxation time of the components of the interface phase at 20 ° C. is preferably 100 to 300 μs, more preferably 150 to 280 μs, and most preferably 180 to 250 μs. The relaxation time of the crystal phase components at 20 ° C. is preferably 10 to 30 μs, more preferably 15 to 28 μs, and most preferably 18 to 25 μs.
The content ratio of the amorphous phase component at 40 ° C. is preferably 70 to 95%, more preferably 75 to 95%, and most preferably 80 to 95%. The content ratio of the components of the crystal phase at 40 ° C. is preferably 1 to 10%, more preferably 2 to 8%, and most preferably 3 to 7%.
The relaxation time of the amorphous phase component at 40 ° C. is preferably 500 to 800 μs, more preferably 620 to 780 μs, and most preferably 650 to 750 μs. The relaxation time of the components of the interface phase at 40 ° C. is preferably 10 to 50 μs, more preferably 15 to 40 μs, and most preferably 20 to 35 μs. The relaxation time of the crystal phase components at 40 ° C. is preferably 5 to 30 μs, more preferably 10 to 25 μs, and most preferably 15 to 20 μs.

The A hardness of the polishing layer is preferably 5 to 15, more preferably 6 to 14, and most preferably 7 to 13. When the A hardness is within the above numerical range, a polishing pad having a good balance between the suppression of polishing scratches and the polishing rate can be obtained.

The compressibility of the polishing layer is preferably 35 to 65%, more preferably 35 to 60%, and most preferably 35 to 55%. When the compressibility is within the above numerical range, the contact of the polishing pad with the object to be polished is stable, and good polishing characteristics can be obtained.

(Polyurethane resin composition)
The polyurethane resin of the polishing pad of the present invention is obtained by reacting a polyisocyanate compound with a curing agent such as polyol or polyamine, and a chain extender can also be used. The crystalline phase (hard segment) is composed of structural units derived from an isocyanate compound and a chain extender, and the amorphous phase (soft segment) is a structural unit derived from a polyol or diamine having an aliphatic organic group having a relatively high degree of freedom. Consists of.

The polyisocyanate compound can be used in the form of a prepolymer obtained by reacting the polyisocyanate compound with a polyol in advance to increase the molecular weight.

Examples of the polyisocyanate compound include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, phenylenedi isocyanate, and xylylene diisocyanate: hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hydrogenated. Examples thereof include aliphatic or alicyclic diisocyanates such as tolylene diisocyanate and hydrogenated xylylene diisocyanate.

Examples of the polyol (polymer diol) include polyether diols, polyester diols, polycarbonate diols and the like. These polymer diols may be used alone or in combination of two or more. Among these, it is preferable to use a polyether diol from the viewpoint of reducing polishing scratches.
Examples of the polyether diol include poly (ethylene glycol), poly (propylene glycol), poly (tetramethylene glycol), poly (methyltetramethylene glycol) and the like. These polyether diols may be used alone or in combination of two or more.
The polyester diol can be produced, for example, by directly subjecting an ester-forming derivative such as a dicarboxylic acid or an ester thereof or an anhydride to a low molecular weight diol by a transesterification reaction or a transesterification reaction.
Examples of the dicarboxylic acid constituting the polyesterdiol include succinic acid, glutaric acid, adipic acid, pimeric acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3-. An aliphatic dicarboxylic acid having 4 to 12 carbon atoms such as methyl adipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, and 3,7-dimethyldecanedioic acid; terephthalic acid. , Aromatic dicarboxylic acids such as isophthalic acid and orthophthalic acid; and the like. These dicarboxylic acids may be used alone or in combination of two or more.
Examples of the low molecular weight diol constituting the polyester diol include ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,5-pentane. Diol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decane An aliphatic diol such as a diol; an alicyclic diol such as cyclohexanedimethanol and a cyclohexanediol; and the like can be mentioned. These low molecular weight diols may be used alone or in combination of two or more. Examples of the carbon number of the low molecular weight diol include 6 or more and 12 or less.

Examples of the chain extender include ethylene glycol, diethylene recall, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, saccharose, and methylene glycol. , Glycerin, sorbitol and other aliphatic polyol compounds; bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylsulfone, hydrogenated bisphenol A, hydroquinone and other aromatic polyols. Compounds, water and the like can be used. These chain extenders may be used alone or in combination of two or more.

(Other ingredients)
The polyurethane resin composition of the present invention can contain additives. The additive is preferably selected from the group consisting of a film forming aid and a foaming inhibitor.
Examples of the film forming aid include hydrophobic activators and the like. Examples of the hydrophobic activator include polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, perfluoroalkylethylene oxide adduct, glycerin fatty acid ester, propylene glycol fatty acid ester, and polyether modification. Examples thereof include nonionic surfactants such as silicone and anionic surfactants such as alkylcarboxylic acids.
Examples of the foaming inhibitor include hydrophilic activators and the like. Examples of the hydrophilic activator include anionic surfactants such as carboxylates, sulfonates, sulfates and phosphates, and cellulose esters.
When the film forming aid is added as an additive, it is preferably 0.2 to 10% by mass. When the foaming inhibitor is added as an additive, it is preferably 0.2 to 10% by mass.

(Polymerization reaction of polyurethane resin composition)
The polyurethane resin can be produced by polymerizing the above-mentioned polyurethane resin composition. That is, if necessary, a method of carrying out a polymerization reaction in an organic solvent in the presence of a catalyst can be mentioned.

(Manufacturing method of polishing pad)
The method for manufacturing a polishing pad of the present invention is the above-mentioned method for manufacturing a polishing pad, and includes a step of using a wet film forming method.

Hereinafter, the method for manufacturing the polishing pad of the present invention will be described with reference to the drawings.
FIG. 3 shows a cross-sectional view of an example of the polishing pad of the present invention. The polishing pad 1 of the present invention has a polyurethane sheet 2 as a soft plastic foam manufactured by a wet film forming method. The polyurethane sheet 2 is buffed on the polished surface P side so that the thickness of the polyurethane sheet 2 (length in the vertical direction in FIG. 3) becomes substantially uniform (details will be described later).

In the polyurethane sheet 2, the skin layer formed on the surface side by the wet film forming method is removed by buffing. The buffing process constitutes a polished surface P for polishing the object to be polished. Inside the polyurethane sheet 2, foams 3 having a substantially triangular cross section and rounded along the thickness direction of the polyurethane sheet 2 are formed. The space volume of the foam 3 is formed so that the size of the polished surface P side is smaller than that of the back surface side of the polished surface P. In the polyurethane resin between the foams 3, microfoams having a space volume smaller than that of the foams 3 are formed. Foam 3 and microfoam are connected in a three-dimensional network through communication holes.

Further, in the polishing pad 1, the base material 8 (polyethylene terephthalate resin sheet having a thickness of 188 μm) and the surface of the buffed polyurethane sheet 2 opposite to the buffed surface are bonded to each other using an acrylic adhesive. ing. A double-sided tape for mounting the polishing pad 1 on the polishing machine is attached to the surface of the base material 8 opposite to the surface attached to the polyurethane resin sheet. In the double-sided tape, the adhesive layer on the other side (opposite side to the base material 8) is covered with a release paper.

A polyurethane sheet 2 is produced by a wet film forming method, and a base material 8 is attached to the polyurethane sheet 2. That is, in the wet film-forming method, a polyurethane resin solution in which a polyurethane resin is dissolved in an organic solvent is continuously applied to a film-forming substrate and immersed in an aqueous coagulation liquid to coagulate and regenerate the polyurethane resin into a film. After washing, it is dried to prepare a strip-shaped (long-shaped) polyurethane sheet 2. Hereinafter, the steps will be described in order.

In the preparatory step, the polyurethane resin, N, N-dimethylformamide (hereinafter abbreviated as DMF), which is a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive are mixed to dissolve the polyurethane resin. For example, the polyurethane resin is dissolved in DMF so as to have a concentration of 30% by mass. As the additive, a hydrophilic activator that promotes foaming, a hydrophobic activator that stabilizes the solidification and regeneration of the polyurethane resin, and the like can be used in order to control the size and amount (number) of the foaming 3. After removing agglomerates and the like by filtering the obtained solution, defoaming is performed under vacuum to obtain a polyurethane resin solution.

In the coating step, coagulation / regeneration step, and cleaning / drying step, the polyurethane resin solution obtained in the preparation step is continuously applied to the film-forming substrate and immersed in an aqueous coagulation liquid to coagulate and regenerate the polyurethane resin for cleaning. After that, it is dried to obtain a polyurethane sheet 2. The coating step, the solidification regeneration step, and the cleaning / drying step are continuously executed by, for example, the film forming apparatus shown in FIG.

As shown in FIG. 2, the film forming apparatus 60 is filled with a pretreatment liquid 15 such as water or a DMF aqueous solution (mixed solution of DMF and water) for pretreating the non-woven fabric or woven fabric of the film forming base material. Pretreatment tank 10, coagulation tank 20 filled with coagulation liquid 25 containing water, which is a poor solvent for polyurethane resin, for coagulation and regeneration of polyurethane resin, water for cleaning polyurethane resin after coagulation and regeneration A cleaning tank 30 filled with a cleaning liquid 35 such as the above and a cylinder dryer 50 for drying the polyurethane resin are continuously provided.

A base material supply roller 41 for supplying the film-forming base material 43 is arranged on the upstream side of the pretreatment tank 10. The pretreatment tank 10 has a pair of guide rollers 13 at the lower inside of a substantially central portion in the same longitudinal direction as the transport direction of the film-forming base material 43. Guide rollers 11 and 12 are arranged on the base material supply roller 41 side above the pretreatment tank 10, and an excess pretreatment liquid contained in the pretreated film-forming base material 43 is arranged on the solidification tank 20 side. A mangle roller 18 for removing 15 is arranged. On the downstream side of the mangle roller 18, a knife coater 46 for substantially uniformly applying the polyurethane resin solution 45 to the film-forming base material 43 is arranged. A guide roller 21 is arranged above the coagulation tank 20 on the downstream side of the knife coater 46.

In the coagulation tank 20, a guide roller 23 is arranged at the lower inside on the cleaning tank 30 side. A mangle roller 28 for dehydrating the polyurethane resin after solidification and regeneration is arranged above the solidification tank 20 and on the cleaning tank 30 side. A guide roller 31 is arranged above the washing tank 30 on the downstream side of the mangle roller 28. In the cleaning tank 30, four guide rollers 33 at the top and five guide rollers 33 at the bottom are arranged alternately in the vertical direction, which is the same as the transport direction of the film-forming base material 43. A mangle roller 38 for dehydrating the polyurethane resin after cleaning is arranged above the cleaning tank 30 and on the cylinder dryer 50 side. In the cylinder dryer 50, four cylinders having a heat source inside are arranged in four upper and lower stages. On the downstream side of the cylinder dryer 50, a take-up roller 42 for winding the dried polyurethane resin (along with the film-forming base material 43) is arranged. The mangle rollers 18, 28, 38, the cylinder dryer 50, and the take-up roller 42 are connected to a rotary drive motor (not shown), and the film-forming base material 43 is a base material supply roller by these rotational drive forces. It is conveyed from 41 to the take-up roller 42. The transport speed of the film-forming substrate 43 is set to, for example, 2.5 m / min, and is preferably set in the range of 1.0 to 5.0 m / min.

When a non-woven fabric or a woven fabric is used as the film-forming base material 43, the film-forming base material 43 is pulled out from the base material supply roller 41 and continuously introduced into the pretreatment liquid 15 via the guide rollers 11 and 12. .. By passing the film-forming base material 43 between the pair of guide rollers 13 in the pretreatment liquid 15 to perform pretreatment (sealing), when the polyurethane resin solution 45 is applied, the film-forming base material 43 is inside. The penetration of the polyurethane resin solution 45 of the above is suppressed. After the film-forming base material 43 is pulled up from the pretreatment liquid 15, the film-forming base material 43 is pressed by the mangle roller 18 to draw down the excess pretreatment liquid 15. The film-forming base material 43 after the pretreatment is conveyed in the direction of the solidification tank 20. When a flexible film made of PET or the like is used as the film-forming base material 43, pretreatment is not required, so that the film is fed directly from the guide roller 12 to the mangle roller 18 or into the pretreatment tank 10. The pretreatment liquid 15 may not be added. Hereinafter, in this example, the film-forming base material 43 will be described as a PET film.

In the coating step, the polyurethane resin solution 45 prepared in the preparatory step is substantially uniformly coated on the film-forming substrate 43 by the knife coater 46 at room temperature. At this time, the coating thickness (coating amount) of the polyurethane resin solution 45 is adjusted by adjusting the gap (clearance) between the knife coater 46 and the upper surface of the film-forming base material 43.

In the solidification / regeneration step, the film-forming base material 43 coated with the polyurethane resin solution 45 by the knife coater 46 is introduced into the coagulation liquid 25 from the guide roller 21 toward the guide roller 23. In the coagulation liquid 25, first, a skin layer 4 having a thickness of several μm is formed on the surface of the applied polyurethane resin solution 45. After that, as the replacement of DMF in the polyurethane resin solution 45 with the coagulating liquid 25 progresses, the polyurethane resin is solidified and regenerated on one side of the film-forming base material 43. The solidification / regeneration of the polyurethane resin is completed between the time when the film-forming base material 43 coated with the polyurethane resin solution 45 enters the coagulation liquid 25 and the time it reaches the guide roller 23. When the DMF is desolvated from the polyurethane resin solution 45, foam 3 is formed in the polyurethane resin. At this time, since the film-forming base material 43 of the PET film does not allow water to permeate, desolvation occurs on the surface side of the polyurethane resin solution 45, and foam 3 having a film-forming base material 43 side larger than the surface side is formed. The coagulated and regenerated polyurethane resin is pulled up from the coagulating liquid 25, the excess coagulating liquid 25 is squeezed out by the mangle roller 28, and then transported to the cleaning tank 30 via the guide roller 31 and introduced into the cleaning liquid 35.

In the washing / drying step, the polyurethane resin is washed by passing the polyurethane resin introduced into the cleaning liquid 35 through the guide rollers 33 alternately up and down. After cleaning, the polyurethane resin is pulled up from the cleaning liquid 35, and the excess cleaning liquid 35 is squeezed out by the mangle roller 38. Then, the polyurethane resin is dried by passing it alternately between the four cylinders of the cylinder dryer 50 (in the direction of the arrow in FIG. 2) along the peripheral surface of the cylinders. The dried polyurethane resin (polyurethane sheet 2) is wound around the winding roller 42 together with the film-forming base material 43.

In the buffing step, the skin layer side of the film-forming resin is buffed so that the thickness becomes uniform. The polyurethane sheet 2 wound around the winding roller 42 is formed on a PET film of the film-forming base material 43. Since the thickness of the polyurethane sheet 2 varies during film formation, irregularities are formed on the polished surface P. After the film-forming base material 43 is peeled off, the surface of the pressure-welding jig having a substantially flat surface is pressed against the surface of the film-forming resin on the side opposite to the skin layer, so that irregularities appear on the skin layer side. The unevenness that appears on the skin layer side is removed by buffing. In this example, since the continuously produced polyurethane sheet 2 is strip-shaped, the skin layer side is continuously buffed while the pressure welding jig is pressed against the polished surface P. As a result, the thickness of the polyurethane sheet 2 from which the skin layer has been removed and the flat polished surface has been formed is eliminated, and openings are formed.

In the bonding step, the base material 8 (polyethylene terephthalate resin sheet having a thickness of 188 μm) and the surface of the buffed polyurethane sheet 2 opposite to the buffed surface are bonded using an acrylic adhesive.

In the laminating process, the double-sided tape is attached to the surface of the base material 8 opposite to the surface to which the polyurethane resin sheet is attached. After embossing the polished surface P, it is cut into a desired shape such as a circle in a cutting / inspection process. The embossing pattern is not particularly limited, and it is sufficient that the slurry moves smoothly during the polishing process. Then, an inspection such as confirming that there is no dirt or foreign matter adhered is performed to complete the polishing pad 1.

(Method of polishing the surface of optical material or semiconductor material)
The method of polishing the surface of an optical material or a semiconductor material of the present invention includes the step of using the above-mentioned polishing pad.

Hereinafter, the polishing method using the polishing pad of the present invention will be described with reference to the drawings.
When polishing the object to be polished, for example, as shown in FIG. 4, a single-sided polishing machine 70 is used. The single-sided polishing machine 70 has a pressure surface plate 72 for pressing an object to be polished on the upper side and a rotatable rotary surface plate 71 on the lower side. Both the lower surface of the pressure surface plate 72 and the upper surface of the rotary surface plate 71 are formed flat. A back pad 75 is attached to the lower surface of the pressure surface plate 72, and a polishing pad 1 for polishing an object to be polished is attached to the upper surface of the rotary surface plate 71. By impregnating the back pad 75 with an appropriate amount of water and pressing the object to be polished 78, the object to be polished 78 is held by the back pad 75 by the surface tension of water and the adhesiveness of the polyurethane resin. By rotating the rotary surface plate 71 while pressurizing the object to be polished 78 with the pressure surface plate 72, the lower surface (processed surface) of the object to be polished 78 is polished by the polishing pad 1.

(Evaluation method of polishing pad)
The method for evaluating a polishing pad of the present invention is a method for evaluating a polishing pad having a polishing layer containing a polyurethane resin, and spins a free induction decay signal (FID) obtained by pulse NMR on the polishing layer by a minimum square method. By subtracting the components with the longest spin-spin relaxation time T2 in order and separating the waveforms, the three components of the amorphous phase, the interface phase, and the crystalline phase are divided in order from the longest spin-spin relaxation time T2, and at 20 ° C. It includes a step of confirming whether or not the content ratio of the component of the crystal phase (Ac ₂₀ ) is 10 to 20% and the content ratio of the component of the interface phase (Ai ₂₀ ) at 20 ° C. is 40 to 50%.

In the method for evaluating a polishing pad of the present invention, the absolute value of the difference between the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai ₄₀ ) (| Ai ₂₀ −) A step of confirming whether or not Ai ₄₀ |) is 35 to 50 can be further included.

In the method for evaluating a polishing pad of the present invention, the numerical ranges of Ac ₂₀ , Ai ₂₀ , | Ai _20- Ai ₄₀ |, and Ai ₄₀ can be those described in the above polishing pad.

The present invention will be described experimentally with the following examples, but the following description is not intended to be construed as limiting the scope of the invention to the following examples.

(Example 1)
100 parts by mass of polyurethane DMF solution having a 100% resin modulus of 4.0 MPa and a concentration of polyester polyurethane resin having a weight average molecular weight of 132800 of 30% by mass, 50 parts by mass of DMF, 5 parts by mass of polyether-modified silicone as an additive, and acetyl. A resin-containing solution was obtained by adding 1 part by mass of butyl cellulose, 1 part by mass of a nonionic surfactant, and 1 part by mass of a cellulose ester and mixing them. The polyester-based polyurethane resin is a chain of 1,4-butanediol / ethylene glycol = 9/1 molar ratio of polyester diol obtained by reacting adipic acid with a polyol having 1,4-butanediol as a constituent unit. The extender obtained by condensing 4,4'-diphenylmethane diisocyanate (MDI) was used.
In this embodiment, the 100% resin modulus means a value obtained by dividing the load applied when the non-foamed resin sheet is stretched 100% (when stretched to twice the original length) by the cross section. .. For 100% resin modulus, a resin solution is thinly stretched and dried with hot air to prepare a dry film having a thickness of about 200 μm, and after curing for a while, the total length is 90 mm, the width at both ends is 20 mm, the distance between grippers is 50 mm, and the width of parallel parts is 10 mm. The sample is punched into a dumbbell shape with a thickness of 200 μm, and the measurement sample is sandwiched between the upper and lower air chucks of the universal material tester Tencilon (Tencilon universal tester "RTC-1210" manufactured by A & D Co., Ltd.) and 20 ° C. (± 2). It was determined by pulling at a tensile speed of 100 mm / min in an atmosphere of 65% (± 5%) humidity (° C.) and dividing the tension at 100% elongation (double stretching) by the initial cross-sectional area of the sample.
Further, in this embodiment, the weight average molecular weight means that measured by GPC under the measurement conditions described later.

Next, a PET film is prepared as a base material for film formation, and the above resin-containing solution is applied thereto with a knife coater to a thickness of 1.0 mm and immersed in a coagulation bath (coagulation liquid: water). The resin-containing solution was coagulated, washed and dried, and then peeled off from the PET film to obtain a resin film (thickness 1.0 mm). The skin layer side formed on the surface of the obtained resin film was ground (grinding amount: 200 μm). Then, a part of the resin film was embossed with a grid-like mold to obtain a polishing pad.

(Comparative Example 1)
Instead of the polyurethane DMF solution of Example 1, a polyurethane DMF solution having a 100% resin modulus of 7.0 MPa and a polyester-based polyurethane resin having a weight average molecular weight of 104300 of 30% by mass was prepared. A resin-containing solution was obtained by mixing 32 parts of DMF and 5 parts of water with 100 parts by mass of this polyurethane DMF solution. As the polyester-based polyurethane resin, a polyester diol obtained by reacting adipic acid with a polyol having 1,4-butanediol as a constituent unit and 1,4-butanediol / 1,6-hexanediol = 9/1. The one obtained by condensing a chain extender having a molar ratio and 4,4'-diphenylmethane diisocyanate (MDI) was used.
After that, a resin film was prepared in the same manner as in Example 1 to obtain a polishing pad.

(Comparative Example 2)
Instead of the polyurethane DMF solution of Example 1, a polyurethane DMF solution having a 100% resin modulus of 8.5 MPa and a weight average molecular weight of 137700 polyester-based polyurethane resin having a concentration of 30% by mass was prepared. A resin-containing solution was obtained by mixing 56 parts of DMF, 2 parts of polyether-modified silicone, and 3 parts of cellulose ester with 100 parts by mass of this polyurethane DMF solution. As the polyester-based polyurethane resin, a polyester diol obtained by reacting adipic acid with a polyol having 1,4-butanediol as a constituent unit and 1,4-butanediol / 1,6-hexanediol = 9/1. The one obtained by condensing a chain extender having a molar ratio and 4,4'-diphenylmethane diisocyanate (MDI) was used.
After that, a resin film was prepared in the same manner as in Example 1 to obtain a polishing pad.

(Comparative Example 3)
Instead of the polyurethane DMF solution of Example 1, a polyurethane DMF solution having a 100% resin modulus of 7.5 MPa and a polyester-based polyurethane resin having a weight average molecular weight of 120,000 and a concentration of 30% by mass was prepared. A resin-containing solution was obtained by mixing 31.8 parts of DMF, 1 part of polyether-modified silicone, and 1 part of cellulose ester with 100 parts by mass of this polyurethane DMF solution. As the polyester-based polyurethane resin, polyester diol obtained by reacting adipic acid with a polyol having 1,4-butanediol as a constituent unit and 1,4-butanediol / 3-methyl-1,5-pentanediol The one obtained by condensing a chain extender having a ratio of 9/1 mol and 4,4'-diphenylmethane diisocyanate (MDI) was used.
After that, a resin film was prepared in the same manner as in Example 1 to obtain a polishing pad.

(Evaluation method)
The following GPC measurement, pulse NMR, A hardness, and D hardness were measured for each of the polishing pads of Example 1 and Comparative Examples 1 to 3. Further, each polishing pad of Example 1 and Comparative Examples 1 to 3 was subjected to a polishing test, and evaluation was performed based on polishing rate variability, polishing stability, and polishing scratches.

(GPC measurement)
From the polishing pads obtained in Example 1 and Comparative Examples 1 to 3, 0.05 g of the polyurethane resin of the polishing layer was cut out, dissolved in 4.95 g of DMF to prepare a 1% polyurethane DMF solution, and after standing in a test tube. It was shaken with a mixer at 50 ° C. for 14 hours. After shaking, 0.5 g of the supernatant was measured and mixed with 2 g of DMF to prepare a 0.2% polyurethane DMF solution, which was then filtered through a 0.45 μm filter to prepare a measurement sample. The obtained measurement sample was measured by gel permeation chromatography (GPC) under the following conditions, and the weight average molecular weight was determined. A calibration curve was prepared using polyethylene glycol oxide (EasiVial PEG / PEO manufactured by Agilent Technologies, Inc.) as a standard sample.
(Measurement condition)
Column: Ohpak KB-805HQ (exclusion limit 2000000)
Mobile phase: 5 mM LiBr / DMF
Flow velocity: 0.75 ml / min (21 kg / cm ² )
Oven: 60 ° C
Detector: RI
Sample volume: 30 μl

(Pulse NMR)
The polishing pads of Example 1 and Comparative Examples 1 to 3 were structurally analyzed by pulse NMR under the following conditions.

Under the above equipment and conditions, the land portion of the obtained embossed polishing pad is cut out with a cutter, and a sample piece of about 1 to 3 mm square is filled in a 10 mmφ sample tube to a height of 1 to 2 cm, and pulse NMR is performed. The attenuation curve was obtained by performing the measurement of. Analysis was performed by the least squares method using the Lorenz function (straight line part) and Gaussian function (curve part) so that the obtained decay curve and fitting curve match, and the crystalline phase, interfacial phase, and non-crystalline phase in the polishing layer were analyzed. The ratio (absence ratio (%)) and relaxation time (T2) were obtained. For fitting and analysis, software attached to the above measuring device was used.

(A hardness)
The A hardness of the polishing layer is based on JIS K7311. A urethane foam sheet sample piece (10 cm x 10 cm) is cut out from the polishing pad, and a plurality of the sample pieces are stacked so as to have a thickness of 4.5 mm or more. It was measured using a hardness tester.

(Compression rate)
The compressibility of the polishing layer was determined using a shopper type thickness measuring instrument (pressurized surface: circular with a diameter of 1 cm) in accordance with JIS L 1021. Specifically, at room temperature (about 20 ° C.), the thickness t ₀ after the initial load is applied for 30 seconds from the unloaded state is measured, and then the final pressure is measured from the state of the thickness t _0. The thickness t ₁ was measured after being left for 1 minute under the same load. From these, the compression ratio was calculated by the following formula. The initial load was 300 g / cm ² and the final pressure was 1800 g / cm ² .

(Polishing rate variability, polishing stability)
Using the polishing pads of Examples 1 and Comparative Examples 1 to 3, 50 silicon wafers with TEOS (Tetro Ethyl Orthosilicate) film and 50 silicon wafers with Cu film were repeatedly polished under the following conditions. It was.
<Polishing conditions>
Polishing machine used: Ebara Corporation, product name "F-REX300"
Polishing speed (surface plate rotation speed): 70 rpm
Dresser: 3M diamond dresser, model number "A188"
Pad break: 30N 30min
Conditioning: Ex-situ, 30N, 4 scans Processing pressure: 176 g / cm ²
Slurry: Colloidal silica slurry (pH: 11.5)
Slurry flow rate: 200 mL / min
Polishing time: 60 seconds Object to be polished: Silicon wafer with TEOS or silicon wafer with Cu film

Then, for each of the silicon wafer with TEOS film and the silicon wafer with Cu film, each polishing rate in the number of polishing treatments of 1 to 50 was determined as follows.
First, with respect to the TEOS film or Cu film on the wafer before and after the polishing test, 121 places were randomly selected over the entire wafer, and the thickness before and after the polishing test was measured at those places. Based on the measured thickness, the average value of the thickness before the polishing test and the average value of the thickness after the polishing test are calculated, and the average value of the polished thickness is calculated by taking the difference between these average values. did. Then, the polishing rate (Å / min) was obtained by dividing the average value of the obtained polished thickness by the polishing time. The thickness was measured in the DBS mode of an optical film thickness film quality measuring device (manufactured by KLA Tencor, model number "ASET-F5x"). The maximum value, minimum value, average value, and standard deviation of the polishing rate at 50 polishing rates were obtained, and the polishing rate variability and polishing stability were calculated by the following formulas.
In the evaluation of the polishing rate variability and the polishing stability, since the evaluation includes the polishing treatment for 1 to 4 sheets corresponding to the initial stage of polishing in which the polishing rate is likely to fluctuate, the polishing for 5 to 50 sheets is performed. This means that the polishing rate variability and polishing stability are evaluated more strictly than the evaluation for the treatment.

The lower the value of polishing rate variability (%), the smaller the polishing rate fluctuation at the initial stage of polishing. It can be said that the fluctuation of the polishing rate is sufficiently small when the polishing rate variability (%) is 25% or less for the silicon wafer with the TEOS film and 5% or less for the silicon wafer with the Cu film.
Further, the lower the value of polishing stability (%), the smaller the variation in the polishing rate value, which indicates that the polishing rate is stable. It can be said that the polishing rate is sufficiently stable when the polishing stability (%) is 10% or less for the silicon wafer with the TEOS film and 2.0% or less for the silicon wafer with the Cu film.

(Abrasive scratch)
Regarding polishing scratches, the 10th, 25th, and 50th TEOS film-coated silicon wafers and Cu film-coated silicon obtained by polishing in the above (polishing rate variability, polishing stability) The wafer was measured in a high-sensitivity measurement mode of a surface inspection device (Surfscan SP2XP manufactured by KLA Tencor), and the number (pieces) of polishing scratches on the surface of the substrate was observed to obtain the total.
When the number of polishing scratches is 5 or less for the silicon wafer with TEOS film and 30 or less for the silicon wafer with Cu film, it can be said that there are few polishing scratches and it is good.

The results are shown in Table 2 below and FIGS. 5-6B. Further, cross-sectional photographs of the polishing pads obtained in Example 1 and Comparative Examples 1 to 3 are shown in FIGS. 7A and 7B.

From the results in Table 2, the content ratio of the component of the crystal phase (Ac ₂₀ ) at 20 ° C. is 10 to 20%, and the content ratio of the component of the interface phase (Ai ₂₀ ) at 20 ° C. is 40 to 50%. The polishing pad of Example 1 has little fluctuation in the polishing rate during polishing for both the silicon wafer with TEOS film and the silicon wafer with Cu film, has excellent polishing stability, and can suppress the occurrence of polishing scratches. I understood.

On the other hand, the polishing pad of Comparative Example 1 in which Ac ₂₀ is more than 20% and Ai ₂₀ is less than 40% is for either a silicon wafer with a TEOS film or a silicon wafer with a Cu film, as compared with the polishing pad of Example 1. However, the polishing rate fluctuated greatly during polishing, and the polishing stability was inferior. It is considered that this is because the Ai ₂₀ was small in the polishing pad of Comparative Example 1.
Further, the polishing pad of Comparative Example 1 had more polishing scratches on the silicon wafer with a Cu film than the polishing pad of Example 1.

The polishing pad of Comparative Example 2 in which Ac ₂₀ greatly exceeds 20% and Ai ₂₀ is less than 40% is different from the polishing pad of Example 1 in both the silicon wafer with TEOS film and the silicon wafer with Cu film. The polishing rate fluctuated greatly during polishing, and the polishing stability of the silicon wafer with a TEOS film was inferior.
Further, in the polishing pad of Comparative Example 2, polishing scratches were extremely generated in both the silicon wafer with the TEOS film and the silicon wafer with the Cu film as compared with the polishing pad of Example 1. It is considered that the reason why many polishing scratches were generated was that Ac ₂₀ was considerably large in the polishing pad of Comparative Example 2.

Although Ai ₂₀ is 40 to 50%, Ac ₂₀ exceeds 20%, and the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai). the absolute value of the difference between the _{40) (| Ai 20 -Ai 40} |) polishing pad of Comparative example 3 is less than 35, compared with the polishing pad of example 1, TEOS film-coated silicon wafer and a Cu film with a silicon wafer In each of the above, the polishing rate fluctuated greatly during polishing, and the polishing stability was inferior. This is because, in the polishing pad of Comparative Example 3, although the content ratio of the interface phase component at 20 ° C. is high, the value does not decrease significantly even at 40 ° C., so that the self-dressing property (self-disintegrating property) is achieved in the latter stage of polishing. ) Is too high, the amount of pad wear becomes excessive, the opening of the polished surface is enlarged, and the fluctuation of the polished surface area is increased.
Further, in the polishing pad of Comparative Example 3, polishing scratches were extremely generated in both the silicon wafer with the TEOS film and the silicon wafer with the Cu film as compared with the polishing pad of Example 1.

From the above results, the polishing pad has a crystal phase component content ratio (Ac ₂₀ ) at 20 ° C. of 10 to 20% and an interface phase component content ratio (Ai ₂₀ ) of 40 to 50% at 20 ° C. However, it was confirmed that polishing scratches were suppressed, the polishing rate did not fluctuate during polishing, and the polishing stability was excellent.

Further, according to the present invention, the content ratio (Ac ₂₀ ) of the component of the crystal phase at 20 ° C. is 10 to 20%, and the content ratio (Ai ₂₀ ) of the component of the interface phase at 20 ° C. is 40 to 50%. It was found that the performance of the polishing pad such as suppression of polishing scratches, suppression of fluctuations in polishing rate during polishing, and excellent polishing stability can be evaluated by confirming the presence or absence.

Claims (8)

A polishing pad having a polishing layer containing a polyurethane resin.
In the polishing layer, the free induction decay signal (FID) obtained by pulse NMR is subtracted in order from the component having the longest spin-spin relaxation time T2 by the minimum square method, and the waveform is separated to obtain the longer spin-spin relaxation time T2. When divided into three components, an amorphous phase, an interface phase, and a crystalline phase, the content ratio (Ac ₂₀ ) of the component of the crystal phase at 20 ° C. is 10 to 20%, and the component of the interface phase at 20 ° C. The polishing pad having a content ratio (Ai ₂₀ ) of 40 to 50%. The absolute value (| Ai _20- Ai ₄₀ |) of the difference between the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai ₄₀ ) is 35 to 50. , The polishing pad according to claim 1. The polishing pad according to claim 1 or 2, wherein the polishing layer has an A hardness of 5 to 15. The polishing pad according to any one of claims 1 to 3, wherein the polishing layer has a compressibility of 35 to 65%. The method for manufacturing a polishing pad according to any one of claims 1 to 4, wherein the method includes a step of using a wet film forming method. The method for polishing the surface of an optical material or a semiconductor material, which comprises the step of using the polishing pad according to any one of claims 1 to 4. A method for evaluating a polishing pad having a polishing layer containing a polyurethane resin.
For the polishing layer, the free induction decay signal (FID) obtained by pulse NMR is subtracted in order from the component having the longest spin-spin relaxation time T2 by the minimum square method, and the waveform is separated to obtain the longer spin-spin relaxation time T2. When divided into three components, an amorphous phase, an interface phase, and a crystalline phase, the content ratio (Ac ₂₀ ) of the component of the crystal phase at 20 ° C. is 10 to 20%, and the component of the interface phase at 20 ° C. The evaluation method including a step of confirming whether or not the content ratio (Ai ₂₀ ) is 40 to 50%. The absolute value (| Ai _20- Ai ₄₀ |) of the difference between the content ratio of the interface phase component at 20 ° C. (Ai ₂₀ ) and the content ratio of the interface phase component at 40 ° C. (Ai ₄₀ ) is 35 to 50. The evaluation method according to claim 7, further comprising a step of confirming whether or not.