JP7189057B2 - polishing pad - Google Patents

Description

The present invention relates to polishing pads. The polishing pad of the present invention is used for polishing optical materials, semiconductor devices, glass 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.

Conventionally, for polishing semiconductor devices, prepolymers containing components derived from TDI (toluenediisocyanate) and PTMG (polyoxytetramethylene glycol) and diamines such as MOCA (4,4′-methylenebis(2-chloroaniline)) A polishing pad having a polishing layer made of a polyurethane material obtained by reacting a curing agent is generally used. In recent years, with the miniaturization of wiring in semiconductor devices, there are cases where conventional polishing pads are insufficient in step performance and defect performance. ing.

However, even when a polyol is used as a curing agent, when PTMG is contained in the prepolymer, the tan δ value of the polishing layer changes greatly with temperature, so the polishing performance is greatly affected by the temperature. Sometimes it didn't show performance. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a polishing pad in which the temperature change of the tan δ value of the polishing layer is small and the effect of temperature on the polishing performance is small.

The present invention provides the following.
[1]
A polishing pad having a polishing layer made of polyurethane resin foam,
The polyurethane resin is a cured product of a curable resin composition containing an isocyanate-terminated urethane prepolymer and a curing agent,
the isocyanate-terminated prepolymer comprises components derived from toluene diisocyanate (TDI) and polypropylene glycol (PPG);
The value of tan δ of the polishing layer measured by a dynamic viscoelasticity test at a measurement frequency of 10 radian/second and a tensile mode is 0.12 or more at 40° C. and the following formula:
[(maximum value of tan δ of the polishing layer at 20° C. to 80° C.)−(minimum value of tan δ of the polishing layer at 20° C. to 80° C.)]/tan δ of the polishing layer at 40° C.
A polishing pad, wherein the fluctuation rate of tan δ of the polishing layer at 20° C. to 80° C. represented by is 50% or less.
[2]
The polishing pad of [1], wherein the curable resin composition further contains hollow microspheres as a foaming agent.
[3]
The polishing pad of [1] or [2], wherein the isocyanate-terminated prepolymer further contains a component derived from diethylene glycol (DEG).
[4]
A method for polishing the surface of an optical material or a semiconductor material, characterized by using the polishing pad according to any one of [1] to [3].
[5]
A method for reducing scratches when polishing the surface of an optical material or semiconductor material using the polishing pad according to any one of [1] to [3].

ADVANTAGE OF THE INVENTION According to this invention, the polishing pad which shows favorable step|step difference performance and defect performance can be provided.

4 is a graph showing the results of dynamic viscoelasticity measurement (DMA) of the polishing layers of the polishing pads of Examples and Comparative Examples. 4 is a graph showing the results of dynamic viscoelasticity measurement (DMA) of the polishing layers of the polishing pads of Examples and Comparative Examples.

[Action]
The polishing pad of the present invention is a polishing pad having a polishing layer made of a polyurethane resin foam, wherein the polyurethane resin is a cured product of a curable resin composition containing an isocyanate-terminated urethane prepolymer and a curing agent, The isocyanate-terminated prepolymer contains components derived from toluene diisocyanate (TDI) and polypropylene glycol (PPG), and the tan δ value of the polishing layer is 40 as measured by a dynamic viscoelastic test at a measurement frequency of 10 radians/second and a tensile mode. 0.12 or more at ° C. and the following formula:
[(maximum value of tan δ of the polishing layer at 20° C. to 80° C.)−(minimum value of tan δ of the polishing layer at 20° C. to 80° C.)]/tan δ of the polishing layer at 40° C.
The fluctuation rate of tan δ of the polishing layer at 20° C. to 80° C. represented by is 50% or less. That is, the polishing layer of the polishing pad of the present invention has a larger value of tan δ at a polishing temperature (around 40° C.) than that of a conventional polishing pad, and the temperature change of tan δ is small in a wide temperature range of 20° C. to 80° C. . In this specification, it is expressed as a percentage obtained by multiplying the variability value by 100.

The viscoelasticity of a material can be considered by combining both the storage modulus (E'), which reflects elasticity, and the loss modulus (E''), which reflects viscosity. tan δ = loss modulus (E″)/storage modulus (E′) is a parameter that reflects the balance between the two. A conventional polishing layer made of polyurethane resin tends to increase in tan δ because its viscosity increases as the temperature rises.

However, as a result of intensive studies, the present inventors found that when the component of the polyurethane resin contains a PPG-derived component, the tan δ value of the polishing layer at a polishing temperature (around 40° C.) is lower than that of the conventional polishing pad. It was found that the tan .delta. This means that the polishing pad of the present invention is highly viscous even at a relatively low temperature of 20°C to 40°C and does not damage the object to be polished, and even at a relatively high temperature of 40°C to 80°C. It means that the initial polishing rate can be maintained without becoming too viscous. In the industry, there is a tendency to expect a lower polishing rate when the tan δ value of the polishing layer is high. When evaluated over a long period of time, an unexpected result is obtained that defects such as scratches are few and the desired polishing rate is obtained. This can also be understood from the fact that the polishing pad of the present invention exhibits excellent polishing properties such as high step performance, few scratches, and a high polishing rate in the results of polishing tests described later.

で表されるＰＴＭＧ（ポリオキシテトラメチレングリコール）は、温度変化に対して分子が変形しやすいが、本発明で、上記プレポリマーのポリオール成分に従来のＰＴＭＧの代わりに下記構造式：

で表されるＰＰＧ（ポリプロピレングリコール）を用いたことにより、温度変化に対して分子が変形しにくい材料を製造できたことによると考えられる。すなわち、ＰＴＭＧ単位は炭素数４個分の長さの直鎖構造であるため、低温領域では凝集しやすい分子構造であり、高温領域になると凝集した分子同士がほつれやすい。一方、本発明でプレポリマーに使用するＰＰＧ単位は炭素数２個分の長さの主鎖を構成し、メチル基が主鎖から分岐しているので、低い温度領域でも凝集しにくい分子構造となっている。このような両者の構造の違いは、温度上昇に伴う分子の運動性にも影響していると考えられる。 The effects of the present invention have been found experimentally and are not bound by any particular theory. , has been used with the following structural formula:

PTMG (polyoxytetramethylene glycol) represented by is susceptible to molecular deformation due to temperature changes, but in the present invention, the following structural formula is used instead of conventional PTMG as the polyol component of the prepolymer:

It is believed that the use of PPG (polypropylene glycol) represented by the following makes it possible to produce a material whose molecules are less likely to deform due to temperature changes. That is, since the PTMG unit has a straight chain structure with a length of 4 carbon atoms, it has a molecular structure that easily aggregates in a low temperature range, and the aggregated molecules easily fray in a high temperature range. On the other hand, the PPG unit used in the prepolymer in the present invention forms a main chain with a length of 2 carbon atoms, and since methyl groups are branched from the main chain, it has a molecular structure that is difficult to aggregate even in a low temperature range. It's becoming Such structural differences between the two are thought to affect the molecular mobility associated with temperature rise.

に示す２官能のＰＰＧであることが好ましい。ＰＰＧの数平均分子量は、７００～５０００であることが好ましく、より好ましくは１０００～２０００である。数平均分子量が１０００または分子長がＰＴＭＧ１０００と同等のＰＰＧが特に好ましい。 [Prepolymer]
The isocyanate-terminated prepolymers of the present invention comprise components derived from toluene diisocyanate (TDI) and polypropylene glycol (PPG), and preferably further comprise components derived from diethylene glycol (DEG). TDI is graded according to the ratio of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate: TDI100 (100% 2,4-toluene diisocyanate), TDI80 (80% 2,4-toluene diisocyanate and 2,6-toluene diisocyanate). - a mixture with 20% toluene diisocyanate). PPG may have substituents within a range that does not affect the performance of the polishing pad of the present invention.

It is preferably a bifunctional PPG shown in . The number average molecular weight of PPG is preferably 700-5000, more preferably 1000-2000. PPG with a number average molecular weight of 1000 or a molecular length equivalent to PTMG1000 is particularly preferred.

The molar ratio of the isocyanate component to the PPG component in the prepolymer is preferably 20:1 to 2:1, more preferably 10:1 to 2:1. When a third component such as DEG is added, the third component is adjusted to 30 mol% or less, particularly 5 to 25 mol%, based on 100 mol% of the total components constituting the prepolymer. .

Examples of prepolymers suitable for use in the present invention are shown below.
Prepolymer (1): TDI100 (50-90 mol%) / PPG1000 (25-5 mol%) / DEG (25-5 mol%) (NCO equivalent 400-600)
Urethane prepolymer prepolymer having an NCO equivalent of 400 to 600 containing TDI100 (toluene-2,4-diisocyanate) as a polyisocyanate component, PPG1000 (polypropylene glycol having a number average molecular weight of 1000) and DEG (diethylene glycol) as a polyol component (2): TDI100 (50-90 mol%) / PPG1000 (15-3 mol%) / PPG2000 (polypropylene glycol with a number average molecular weight of 2000) (10-2 mol%) / DEG (25-5 mol%) (NCO equivalent 400-600 )
TDI100 (toluene-2,4-diisocyanate) as a polyisocyanate component, PPG1000 (polypropylene glycol with a number average molecular weight of 1000), PPG2000 (polypropylene glycol with a number average molecular weight of 2000) and DEG (diethylene glycol) as a polyol component NCO equivalent weight 400 ~ 600 urethane prepolymer

[Polishing pad]
The polishing pad of the present invention comprises a polishing layer made of foamed polyurethane resin and a substrate layer laminated via a double-sided tape. Also includes a mode of attaching to. The polishing layer is arranged at a position in direct contact with the material to be polished.

The polishing pad of the present invention can be used in the same manner as a general polishing pad. It is also possible to polish by pressing against the polishing layer while rotating.

[Method for producing polishing pad]
In the polishing pad of the present invention, the polishing layer can be produced by generally known manufacturing methods such as molding and slab molding. First, a block of polyurethane is formed by these manufacturing methods, the block is made into a sheet by slicing or the like, a polishing layer formed from a polyurethane resin is molded, and the polishing layer is laminated to a base material.

More specifically, the polishing layer is attached with a double-sided tape to the surface opposite to the polishing surface of the polishing layer, attached to the base material layer, and cut into a predetermined shape to form the polishing pad of the present invention. Become. The double-sided tape is not particularly limited, and can be used by arbitrarily selecting from double-sided tapes known in the art.

The polishing layer is formed by preparing a polyurethane resin curable composition containing a polyisocyanate compound and a polyol compound and curing the polyurethane resin curable composition. In the present invention, a curable polyurethane resin composition is prepared by preparing in advance a prepolymer that facilitates control of the performance of the polishing layer and mixing it with a predetermined curing agent.

The polishing layer is made of foamed polyurethane resin in which air bubbles are dispersed in the polyurethane resin curable composition. The method of forming cells is not particularly limited, but there are methods such as foaming with a chemical foaming agent, foaming by mixing mechanical foams, and a method of forming cells by mixing micro hollow spheres. . From the viewpoint of easy control of the bubble diameter, a method of forming bubbles by mixing micro hollow spheres is preferable. In this case, a foaming curable composition containing a prepolymer, a curing agent and a foaming agent is prepared, and the foam is formed by curing the polyurethane resin foaming curable composition.

The curable polyurethane resin composition can be, for example, a two-pack composition prepared by mixing a liquid A containing a polyisocyanate compound (prepolymer) and a liquid B containing other components. Liquid B containing other components can be further divided into a plurality of liquids and mixed with three or more liquids to form a composition.

In the present invention, a prepolymer containing the aforementioned PPG-derived constituents is used. The NCO equivalent weight of the prepolymer is preferably 400-600, more preferably 400-550, more preferably 450-510. The NCO equivalent is "(mass part of polyisocyanate compound + mass part of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound × mass part of polyisocyanate compound / molecular weight of polyisocyanate compound) - (polyol The number of functional groups per molecule of the compound×parts by mass of the polyol compound/molecular weight of the polyol compound)]”, and is a numerical value indicating the molecular weight of PP (prepolymer) per NCO group.

[Isocyanate component]
Examples of isocyanate components other than TDI include:
m-phenylene diisocyanate,
p-phenylene diisocyanate,
naphthalene-1,4-diisocyanate,
diphenylmethane-4,4'-diisocyanate (MDI),
4,4′-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI),
3,3′-dimethoxy-4,4′-biphenyl diisocyanate,
3,3′-dimethyldiphenylmethane-4,4′-diisocyanate,
xylylene-1,4-diisocyanate,
4,4'-diphenylpropane diisocyanate,
trimethylene diisocyanate,
hexamethylene diisocyanate,
propylene-1,2-diisocyanate,
butylene-1,2-diisocyanate,
cyclohexylene-1,2-diisocyanate,
cyclohexylene-1,4-diisocyanate,
p-phenylene diisothiocyanate,
xylylene-1,4-diisothiocyanate,
and ethylidine diisothiocyanate.

[Polyol component]
Examples of polyol components other than PPG (that is, 1,2-propanediol) include:
ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1, diols such as 6-hexanediol;
Polyether polyols such as polytetramethylene glycol (PTMG), polyethylene glycol, polypropylene glycol;
Polyester polyols such as reaction products of ethylene glycol and adipic acid and reaction products of butylene glycol and adipic acid;
polycarbonate polyols;
polycaprolactone polyol;
etc.

[Curing agent]
In the present invention, the curing agent consists of polyamines and polyols.
Polyamine curing agent:
Polyamines include, for example, diamines, including alkylenediamines such as ethylenediamine, propylenediamine and hexamethylenediamine; diamines having an aliphatic ring such as isophoronediamine and dicyclohexylmethane-4,4′-diamine; ,3′-dichloro-4,4′-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA) and other diamines having an aromatic ring; 2-hydroxyethylethylenediamine, 2-hydroxy diamines having a hydroxyl group such as ethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, especially hydroxyalkylalkylenediamine; be done. Tri-functional triamine compounds and tetra- or higher-functional polyamine compounds can also be used.
Polyol curing agent:
The polyol components exemplified in the item of the prepolymer components described above, including PPG, can be mentioned.

[Composition and amount of curing agent]
The flexibility of the polishing pad can be adjusted not only by the constituent components of the prepolymer, but also by the mixing ratio of the polyamine curing agent and the polyol curing agent in the curing agent. When using a mixture of a polyamine curing agent and a polyol curing agent, the hydroxyl group ratio of the curing agent, which is the ratio of the number of hydroxyl groups in the curing agent when the number of amino groups in the curing agent is 100, is 10 to 50. More preferably, the hydroxyl group ratio is 15-30. In addition, the R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent to the isocyanate groups present at the ends of the prepolymer, is 0.60 to 1.2. It is preferred to use quantities. The R value is more preferably 0.70 to 1.0, more preferably 0.80 to 0.95. The D hardness (JISK6253-1997/ISO7619) of the polishing pad is preferably 20-70, more preferably 30-50.

[Blowing agent]
A foam can be formed by mixing hollow microspheres into a polyurethane resin. Hollow microspheres are heat-expanded unfoamed heat-expandable microspheres composed of an outer shell (polymer shell) made of a thermoplastic resin and a low-boiling-point hydrocarbon contained in the outer shell. . Thermoplastic resins such as acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, and vinyl chloride-ethylene copolymer can be used as the polymer shell. Similarly, as the low boiling point hydrocarbon encapsulated in the polymer shell, for example, isobutane, pentane, isopentane, petroleum ether and the like can be used.

The present invention will be specifically described by the following examples, but the following description is not intended to be construed as limiting the scope of the present invention to the following examples.
[material]
The materials used in the examples below are listed.

・Isocyanate-terminated prepolymer:
The following four types of prepolymers were prepared according to methods common in the art and provided for the following examples and comparative examples.
Prepolymer (1): TDI100/PPG1000/DEG (NCO equivalent weight 506)
TDI100 (toluene-2,4-diisocyanate) (66.7 mol%) as a polyisocyanate component, PPG1000 (polypropylene glycol having a number average molecular weight of 1000) (20.9 mol%) and DEG (diethylene glycol) (12.7 mol%) as a polyol component. 4 mol%) urethane prepolymer prepolymer (2) having an NCO equivalent of 506: TDI100/PPG1000/PPG2000/DEG (NCO equivalent of 505)
TDI100 (toluene-2,4-diisocyanate) (66.7 mol%) as a polyisocyanate component, PPG1000 (polypropylene glycol having a number average molecular weight of 1000) (6.4 mol%) as a polyol component, PPG2000 (having a number average molecular weight of 2000) Polypropylene glycol) (6.8 mol%) and DEG (diethylene glycol) (20.1 mol%) Urethane prepolymer with an NCO equivalent of 505 Prepolymer (3): TDI100/PTMG650/DEG (NCO equivalent 458)
Urethane prepolymer prepolymer (4) with an NCO equivalent weight of 458 containing TDI100 (toluene-2,4-diisocyanate) as a polyisocyanate component, PTMG650 (polytetramethylene glycol having a number average molecular weight of 650) and DEG (diethylene glycol) as a polyol component: TDI100/PTMG1000/PTMG650/DEG (NCO equivalent 458)
TDI100 (toluene-2,4-diisocyanate) as a polyisocyanate component, PTMG1000 (polytetramethylene glycol with a number average molecular weight of 1000), PTMG650 (polytetramethylene glycol with a number average molecular weight of 650) and DEG (diethylene glycol) as a polyol component Urethane prepolymer with NCO equivalent of 458

・Curing agent:
Curing agent (1): MOCA (3,3'-dichloro-4,4'-diaminodiphenylmethane, also known as methylenebis-o-chloroaniline)
Hardener (2): 1:1 mixture of MOCA and PPG2000 (weight ratio)

・Other components Micro hollow spheres (foaming agent): EXPANCEL 551DE40d42 manufactured by Nippon Philite Co., Ltd.

[Example 1]
100 g of prepolymer (1) was prepared as the A component, 23 g of MOCA as a curing agent as the B component, and 2 g of micro hollow spheres as the C component.
After mixing the A component and the C component and defoaming the mixture of the A component and the C component under reduced pressure, the mixture of the A component and the C component and the B component were supplied to the mixer.
The resulting mixture was poured into a mold heated to 80° C. and cured by heating for 1 hour, then the formed resin foam was extracted from the mold and cured at 120° C. for 5 hours. This foam was sliced to a thickness of 1.3 mm to prepare a urethane sheet, and this urethane sheet was used as a polishing pad to evaluate the polishing performance.

Table 1 shows the composition, R value and D hardness of the obtained urethane sheet. The D hardness was determined as follows.
(D hardness)
The D hardness of the polishing pad was measured using a D-type hardness tester in accordance with Japanese Industrial Standards (JIS-K-6253). Here, the samples were obtained by stacking a plurality of urethane sheets as necessary so as to have a total thickness of at least 4.5 mm.

[Examples 2 to 6 and Comparative Examples 1 to 3]
Based on the formulation in Table 1, five types of polishing pads were prepared using two types of prepolymers using PPG as Examples 2 to 6. Comparative Example 1 is a conventionally known polishing pad IC1000 (manufactured by Nitta Haas). A polishing pad using PTMG prepolymer and MOCA as a curing agent was prepared as Comparative Example 2, and a polishing pad using PTMG prepolymer and MOCA and PPG2000 as curing agents were prepared as Comparative Example 3 based on the formulation shown in Table 1, respectively. Table 1 shows the composition, R value and D hardness of the urethane sheets of Examples 2 to 6 and Comparative Examples 1 to 3.

[Dynamic viscoelasticity measurement (DMA)]
For each of the above examples and comparative examples, the viscoelastic properties of the sample in the dynamic viscoelasticity test were storage elastic modulus (E′), loss elastic modulus (E″), loss tangent: tan δ (=E″/E′ ) was measured at 20 to 80°C. The dynamic viscoelasticity test was measured under the following conditions according to JIS K7244-4.
Measuring device: TA Instruments Japan RSAIII
Test Mode: Tensile Temperature Dispersion Specimen: 4 x 0.5 x 0.125 cm
Frequency: 1.6Hz
Initial load: 148g
Temperature: 20-80°C
Strain range: 0.1%
Heating rate: 5° C./min Table 2, FIGS. 1 and 2 show the DMA measurement results (tan δ) of each example and comparative example.

In Table 2, the volatility is defined by the following formula.
[(maximum value of tan δ at 20° C. to 80° C.)−(minimum value of tan δ at 20° C. to 80° C.)]/tan δ at 40° C.
In Table 2, the fluctuation rate is expressed as a percentage obtained by multiplying the value of the above formula by 100.

As can be seen from Table 2, the conventionally known polishing pad of Comparative Example 1 had a low tan δ value of 0.106 at 40° C. and a slightly large fluctuation rate of tan δ. In addition, in Comparative Example 2 in which a prepolymer containing PTMG (prepolymer (3)) was used and MOCA and PPG were used as curing agents, the tan δ value at 40°C was as high as 0.134, but the tan δ fluctuation rate was low. It has increased to 103.3%. Comparative Example 3, which uses a prepolymer containing PTMG (prepolymer (4)) and uses MOCA as a curing agent, has a low tan δ value of 0.093 at 40° C. and a tan δ fluctuation rate of 50.5%. It was big. On the other hand, in Examples 1 to 6 using prepolymers containing PPG (prepolymers (1) and (2)), the value of tan δ at 40°C was 0.00, even when the component ratio of the curing agent was changed. 12 or more, and the variation rate of tan δ was 30% or less.

A polishing test was conducted on the polishing pads of the above Examples and Comparative Examples. The results are shown below.
<Conditions of polishing test>
・Grinding machine used: F-REX300X manufactured by Ebara Corporation
・Disk: 3MA188 (#100)
・Number of rotations: (surface plate) 70 rpm, (top ring) 71 rpm
・Polishing pressure: 3.5 psi
・Abrasive: Cabot Corporation, product number: SS25 (SS25 undiluted solution: pure water = 1:1 weight ratio mixed solution is used)
・Abrasive temperature: 20°C
・Abrasive discharge rate: 200ml/min
Workpiece (object to be polished): A substrate obtained by forming an insulating film of 1 μm in thickness with tetraethoxysilane on a 12-inch silicon wafer by PE-CVD Pad break: 35 N for 10 minutes Conditioning: Ex-situ, 35N, 4 scans

(Evaluation of defect performance)
The defect performance was measured by polishing 25 substrates, and measuring five of the 21st to 25th substrates after polishing in the high-sensitivity measurement mode of a wafer surface inspection device (Surfscan SP1DLS, manufactured by KLA-Tencor). The number of defects such as scratches on the substrate surface was counted. The defects evaluated here are the sum of defects such as particles, organic matter derived from pad scraps, organic residues, scratches, film-derived voids, and watermarks.
The evaluation criteria for defect performance are as follows.
Less than 50 defects of 0.16 μm or more: ◎ (extremely good)
Less than 100 defects of 0.16 μm or more: ○ (good)
Less than 200 defects of 0.16 μm or more: Δ (slightly good)
200 or more defects of 0.16 μm or more: × (defective)

(Evaluation of step performance)
The step performance was measured using a wafer with a copper wiring pattern (SEMATECH, 754 wafer), polishing with an abrasive (Fujimi Corporation, PLANARLITE7000), and measuring 100 μm/100 μm dishing with a step, surface roughness, and fine shape measuring device. (manufactured by KLA-Tencor, P-16+) for evaluation.
The evaluation criteria for the step performance are as follows, evaluated by the depth of the depression from the insulating film.
Dishing less than 400 Å: ◎ (extremely good)
Dishing less than 500 Å: ○ (good)
Dishing is 750 Å or more: × (defective)

Evaluation results of defect performance and step performance are shown in Table 3 below.

From the results in Table 3, the defect performance was poor in all of Comparative Examples 1 to 3, while the number of defects in all of Examples 1 to 6 was less than 200. The defect performance is considered to be affected by the variation rate of tan δ and the D hardness. Less and less Examples 3-6 gave better results. Regarding the step performance, it is considered that the value of tan δ at 40 ° C. is affected. Large Examples 1-3 and Example 6 gave very good results.

Claims (4)

A polishing pad having a polishing layer made of polyurethane resin foam,
The polyurethane resin is a cured product of a curable resin composition containing an isocyanate-terminated urethane prepolymer and a curing agent,
The isocyanate-terminated prepolymer is derived from 50 to 90 mol% toluene diisocyanate (TDI), 25 to 5 mol% polypropylene glycol (PPG) having a number average molecular weight of 1000 to 2000 , and 25 to 5 mol% diethylene glycol (DEG). consists of
the curing agent is 3,3′-dichloro-4,4′-diaminodiphenylmethane (MOCA) alone or a mixture of MOCA and PPG;
The value of tan δ of the polishing layer measured by a dynamic viscoelasticity test at a measurement frequency of 10 radian/second and a tensile mode is 0.12 or more at 40° C. and the following formula:
[(maximum value of tan δ of the polishing layer at 20° C. to 80° C.)−(minimum value of tan δ of the polishing layer at 20° C. to 80° C.)]/tan δ of the polishing layer at 40° C.
A polishing pad, wherein the fluctuation rate of tan δ of the polishing layer at 20° C. to 80° C. represented by is 50% or less. The polishing pad according to claim 1, wherein the curable resin composition further contains hollow microspheres as a foaming agent. A method for polishing the surface of an optical material or a semiconductor material, characterized in that the polishing pad according to any one of claims 1 and 2 is used. A method for reducing scratches when polishing the surface of an optical material or a semiconductor material using the polishing pad according to any one of claims 1 and 2 .

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