JP2023146016A - Polishing pad and method for manufacturing polishing pad - Google Patents

Abstract

To provide a polishing pad which is excellent in step elimination performance and defect performance, and is also excellent in abrasion resistance.SOLUTION: A polishing pad has a polishing layer composed of a polyurethane resin foam derived from an isocyanate-terminated prepolymer and a curing agent, wherein a distance between hard segments in the polishing layer measured by an X-ray small angle scattering method is 9.5 nm or less.SELECTED DRAWING: Figure 1

Description

FIELD OF THE INVENTION The present invention relates to polishing pads. Specifically, the present invention relates to a polishing pad that can be suitably used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, and the like.

Chemical mechanical polishing (CMP) is generally used as a polishing method for flattening the surfaces of optical materials, semiconductor wafers, semiconductor devices, and hard disk substrates.

The CMP method will be explained using FIG. As shown in FIG. 1, a polishing apparatus 1 that performs the CMP method is equipped with a polishing pad 3, and the polishing pad 3 contacts a workpiece 8 held on a holding surface plate 16 and performs polishing. The polishing layer 4 includes a polishing layer 4 and a cushion layer 6 that supports the polishing layer 4. The polishing pad 3 is driven to rotate while the object 8 to be polished is pressed, and polishes the object 8 to be polished. At that time, slurry 9 is supplied between polishing pad 3 and object to be polished 8 . Slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard fine abrasive grains, and as the chemical components and abrasive grains in the slurry flow, relative movement with the object to be polished 8 increases the polishing effect. This increases the Slurry 9 is supplied to the polishing surface through the grooves or holes and is discharged.

By the way, for polishing semiconductor devices, a prepolymer containing an isocyanate component (such as toluene diisocyanate (TDI)) and a high molecular weight polyol (such as polyoxytetramethylene glycol (PTMG)) and a diamine-based curing agent (4,4'-methylene bis It is common to use a polishing pad using a hard polyurethane material obtained by reacting (2-chloroaniline) (MOCA), etc.) as the polishing layer 4. The high molecular weight polyol contained in the prepolymer forms a soft segment of urethane, and PTMG, which exhibits ease of handling and appropriate rubber elasticity, has been commonly used as the high molecular weight polyol.

However, in recent years, with the miniaturization of wiring in semiconductor devices, conventional polishing pads may have insufficient performance to eliminate step differences and defect performance, and studies are being conducted to use materials other than PTMG as high molecular weight polyols.

As a document that considers the above-mentioned issues, Patent Document 1 discloses a polishing pad that uses polypropylene glycol (PPG) as a high-molecular-weight polyol in a prepolymer to have high level difference elimination performance and fewer scratches. There is.

Further, Patent Document 2 discloses a polishing pad in which the defect rate is reduced by using a mixture of PPG and PTMG as a high molecular weight polyol of a prepolymer.

Japanese Patent Application Publication No. 2020-157415 Japanese Patent Application Publication No. 2011-040737

However, the polishing pad described in Patent Document 1 has a problem in that the polishing layer has poor wear resistance and the life of the polishing pad is short. Furthermore, the polishing pad described in Patent Document 2 has a problem in that its level difference elimination performance and defect performance are not sufficient.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a polishing pad that is excellent in level difference elimination performance and defect performance, and also has excellent wear resistance.

As a result of intensive research, the present inventor has found that when the material used for the polishing layer of a polishing pad has a structure in which the distance between hard segments is a specific length, it has excellent step elimination performance and defect performance. It was discovered that a polishing pad with further excellent wear resistance can be obtained, and the present invention was achieved. That is, the present invention includes the following.
[1] A polishing pad having a polishing layer made of a polyurethane resin foam derived from an isocyanate-terminated prepolymer and a curing agent,
A polishing pad, wherein the distance between hard segments in the polishing layer measured by small-angle X-ray scattering is 9.5 nm or less.
[2] The isocyanate-terminated prepolymer contains a polyisocyanate compound-derived structural unit and a high molecular weight polyol-derived structural unit,
The polishing pad according to [1], wherein the high molecular weight polyol-derived structural unit includes at least a polypropylene glycol structural unit and a polyester diol structural unit.
[3] The polishing pad according to [2], wherein the polypropylene glycol structural unit is less than 60% by weight based on the high molecular weight polyol-derived structural unit.
[4] The polishing pad according to [2], wherein the polyester diol for forming the polyester diol structural unit has a number average molecular weight of 600 to 2,500.
[5] The polishing pad according to [1], wherein the polyurethane resin foam has an average cell diameter of 5 μm or more and less than 20 μm.
[6] The polishing pad according to [1], wherein the isocyanate-terminated prepolymer has an NCO equivalent of 500 to 600.
[7] The polishing pad according to [1], wherein the distance between hard segments in the polishing layer measured by small-angle X-ray scattering is 3.0 to 9.5 nm.
[8] A method for manufacturing a polishing pad having a polishing layer made of polyurethane resin foam, comprising:
A step of mixing and reacting an isocyanate-terminated prepolymer with a curing agent to obtain the polyurethane resin foam;
molding the polyurethane resin foam into the shape of an abrasive layer,
A method for producing a polishing pad, wherein the distance between hard segments in the polishing layer as measured by small-angle X-ray scattering is 9.5 nm or less.
[9] The method for producing a polishing pad according to [8], wherein an unexpanded balloon is also allowed to coexist when mixing the isocyanate-terminated prepolymer and the curing agent.

The polishing layer of the polishing pad of the present invention has a distance between hard segments of a specific length, thereby providing a polishing pad with excellent step elimination performance and defect performance as well as excellent wear resistance. Can be done.

FIG. 1 is a perspective view of the polishing apparatus 1. FIG. FIG. 2 is a cross-sectional view of the polishing pad. FIG. 3 shows the measurement results of the polishing layers of the polishing pads of Example 1 and Comparative Example 1 by small-angle X-ray scattering. FIG. 4 is an enlarged view of the area surrounded by FIG. 3. FIG. 5 is a diagram in which the graph of FIG. 4 has been corrected to make it easier to find the local maximum. FIG. 6 is a diagram showing a schematic diagram of a step state in a step polishing amount test.

Hereinafter, the embodiments for carrying out the invention will be described, but the present invention is not limited to the embodiments for carrying out the invention.

<<Polishing pad>>
The structure of the polishing pad 3 will be explained using FIG. 2(a). The polishing pad 3 includes a polishing layer 4 and a cushion layer 6, as shown in FIG. 2(a). The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited, and the size (diameter) can be determined as appropriate depending on the size of the polishing device 1 equipped with the polishing pad 3, etc. For example, the diameter can be about 10 cm to 2 m.
Preferably, in the polishing pad 3 of the present invention, the polishing layer 4 is bonded to the cushion layer 6 via an adhesive layer 7, as shown in FIG. 2(a).
The polishing pad 3 is attached to the polishing surface plate 10 of the polishing device 1 with a double-sided tape or the like provided on the cushion layer 6. The polishing pad 3 is rotated by the polishing device 1 while pressing the object 8 to be polished, and polishes the object 8 (see FIG. 1).

<Polishing layer>
(composition)
The polishing pad 3 includes a polishing layer 4 that is a layer for polishing the object 8 to be polished. The material constituting the polishing layer 4 is a specific polyurethane resin.
The size (diameter) of the polishing layer 4 is similar to that of the polishing pad 3, and can be about 10 cm to 2 m in diameter, and the thickness of the polishing layer 4 can usually be about 1 to 5 mm.
The polishing layer 4 is rotated together with the polishing surface plate 10 of the polishing device 1, and while the slurry 9 is poured onto it, the chemical components and abrasive grains contained in the slurry 9 are caused to move relative to the object to be polished 8. By doing so, the object to be polished 8 is polished.
The polishing layer 4 may have hollow microspheres 4A dispersed therein. When the hollow microspheres 4A are dispersed, when the polishing layer 4 is worn away, the hollow microspheres 4A are exposed to the polishing surface and minute voids are created on the polishing surface, and these minute voids retain the slurry. Polishing of the object to be polished 8 can be further progressed.

The polishing layer 4 is formed by slicing a polyurethane resin foam that has been cured by casting a mixture of an isocyanate-terminated prepolymer, a curing agent (chain extender), and, if necessary, hollow microspheres 4A. ing. That is, the polishing layer 4 is dry molded.

(distance between hard segments)
The material constituting the polishing layer 4 has a distance between hard segments of 9.5 nm or less as measured by small-angle X-ray scattering. When the distance between hard segments is 9.5 nm or less, a polishing pad provided with the polishing layer has excellent step elimination performance, excellent defect performance, and excellent wear resistance.
The distance between hard segments is preferably 3.0 to 9.5 nm, more preferably 4.0 to 9.0 nm.

The distance between hard segments is measured by small angle X-ray scattering. Here, the small-angle X-ray scattering method is a method in which X-rays are incident on a sample and the scattered X-rays are obtained using a detector. It is possible to obtain data such as non-destructively.
When the polishing layer 4 made of polyurethane resin foam is measured using the small angle X-ray scattering method, a curve as shown in FIG. 3 can be obtained.

In this specification, the hard segment refers to a portion composed of urethane bonds or urea bonds formed by a reaction between isocyanate and a curing agent in the polyurethane resin constituting the polishing layer 4.
Generally, when measuring by small-angle X-ray scattering, the intensity of the obtained data is not used as is, but the intensity is corrected using the following formula. In the present invention, correction is also performed using this calculation.
Intensity after correction = (Intensity of target sample / Transmittance of target sample) - (Intensity of air / Transmittance of air)

The distance between hard segments is calculated from the maximum value of Q in the area enclosed in FIG. That is, the distance between hard segments can be determined from distance=2π/Q. Therefore, when the value of Q is small, the distance between hard segments becomes large.

This will be explained using FIG. 3. The curve in FIG. 3 has been corrected using transmittance and the like. Focusing on the location of the highest peak in the flat portion of FIG. 3, its X axis corresponds to the distance between hard segments. When the distance between the hard segments thus obtained is 9.5 nm or less, the polishing pad provided with the polishing layer has excellent step elimination performance, excellent defect performance, and excellent wear resistance.

From here, we convert to make it easier to find the maximum. Redraw the graph using the following method.
(Redraw method)
(1) From the obtained curve, a tangent line is derived from the part where the intensity slopes downward to the right. For example, from the measurement results in FIG. 3, a tangent line is derived from the intensity when Q is around 0.1 to 0.2.
(2) Obtain the intensity from the Q value (X) of the tangent derived in (1) above, and calculate the difference between it and the corrected intensity near the inflection point. For example, from the measurement results in FIG. 3, since there is an inflection point between Q and 0.3 to 1.2, the intensity is obtained by substituting Q into the equation of the tangent. Thereafter, the difference is obtained by subtracting the intensity obtained by the tangent equation from the corrected intensity.
(3) Create an intensity difference graph (normal distribution) from the difference obtained in (2) above.
(4) The peak of the normal distribution (the peak of the graph shown in FIG. 5) is estimated to be the distance between hard segments.

Note that when the slope of the strength difference graph is gentle, the sizes of hard segments tend to vary (the sizes of hard segments tend to vary), and when the slope of the strength difference graph is steep, the same There is a tendency for there to be many hard segments of the same size (the hard segments tend to have the same size).

As already explained, good characteristics can be obtained when the distance between the hard segments is 9.5 nm or less, but the distance between the hard segments requires changing the material of the polishing layer 4 or changing the manufacturing method. It can be adjusted by.
For example, when the high molecular weight polyol that is the material of the polishing layer 4 is obtained using both polypropylene glycol and polyester diol, the distance between the hard segments can be changed by changing the ratio of polypropylene glycol and polyester diol. That is, by changing the ratio of polypropylene glycol and polyester diol, the distance between hard segments can be adjusted.

(Hollow microspheres)
The hollow microspheres 4A, which may be contained in the polishing layer 4 in the polishing pad of the present invention, can be confirmed as hollow bodies on the polishing surface of the polishing layer 4 or the cross section of the polishing layer 4, and the hollow bodies usually have a diameter of 2 to 200 μm. (the diameter of the hollow microsphere 4A). The average cell diameter is preferably 5 μm or more and less than 20 μm. The shapes of the hollow microspheres 4A include spherical, elliptical, and shapes close to these.

As the hollow microspheres 4A, commercially available balloons can be used, and examples thereof include already-expanded balloons and unexpanded balloons. The unexpanded microspheres are heat-expandable microspheres, which can be heated and expanded during the manufacturing process to form bubbles of a predetermined size. In the present invention, it can be used as appropriate if necessary.

(Groove machining)
Grooving can be provided on the surface of the polishing layer 4 of the present invention on the object to be polished 8 side. The groove is not particularly limited, and may be either a slurry discharge groove that communicates with the periphery of the polishing layer 4 or a slurry holding groove that does not communicate with the periphery of the polishing layer 4. It may have both slurry holding grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, and examples of the slurry holding grooves include concentric grooves and perforations (through holes), and these can also be combined.

<Cushion layer>
(composition)
The polishing pad 3 of the present invention has a cushion layer 6. It is desirable that the cushion layer 6 allows the polishing layer 4 to contact the object to be polished 8 more uniformly. The material of the cushion layer 6 may be any one of an impregnated nonwoven fabric impregnated with resin, a flexible material such as synthetic resin or rubber, and a foam having a cell structure. Examples include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber. From the viewpoint of adjusting the density and compressive elastic modulus, an impregnated nonwoven fabric is preferable, and it is preferable to use polyurethane as the resin material with which the nonwoven fabric is impregnated.

Further, the cushion layer 6 is preferably made of polyurethane resin having sponge-like microbubbles.

The compressive modulus, density, and bubbles of the cushion layer 6 in the polishing pad 3 of the present invention are not particularly limited, and a cushion layer 6 having known characteristic values can be used.

<Adhesive layer>
The adhesive layer 7 is a layer for adhering the cushion layer 6 and the polishing layer 4, and is usually made of double-sided tape or adhesive. As the double-sided tape or adhesive, those known in the art (for example, adhesive sheets) can be used.
The polishing layer 4 and the cushion layer 6 are bonded together with an adhesive layer 7. The adhesive layer 7 can be formed of at least one type of adhesive selected from acrylic, epoxy, and urethane adhesives, for example. For example, an acrylic adhesive may be used, and the thickness may be set to 0.1 mm.

The polishing pad 3 of the present invention has excellent step elimination performance and defect performance, as well as excellent wear resistance.
Here, the level difference elimination performance refers to the ability to reduce the level difference of a patterned wafer that has a level difference (irregularities) due to polishing. Figure 6 shows a schematic diagram of an experiment to measure the level difference elimination performance. When there is a step difference of 3500 angstroms on the object to be polished, the state in which the step difference is eliminated is shown when a polishing pad with high step resolving performance (dotted line) and a polishing pad with relatively low step resolving performance (solid line) are used. Although there is no difference at the time of (a) in Figure 6, when polishing progresses and the amount of polishing reaches 2000 angstroms, the polishing pad (dotted line) with good level difference elimination performance has a relatively low level difference elimination performance. Compared to the pad (solid line), it is shown that there are fewer level differences ((b)), and the polishing pad with high level difference elimination performance eliminates the level difference relatively quickly ((c)). It can be said that the polishing pad indicated by the dotted line has relatively higher level difference elimination performance than the polishing pad indicated by the solid line.

In addition, "defects" refer to "particles," which refer to the remains of fine particles attached to the surface of the object to be polished, and "pad debris," which refers to the debris of the polishing layer attached to the surface of the object to be polished. Defect performance refers to the ability to reduce these "defects".

And wear resistance refers to resistance to wear.

<<Manufacturing method of polishing pad>>
A method for manufacturing the polishing pad 3 of the present invention will be explained.

<Material of polishing layer>
In the present invention, the main component of the polishing layer material is polyurethane resin. A specific example of the main component material is a polyurethane resin foam material obtained by reacting an isocyanate-terminated prepolymer with a curing agent.

A method of manufacturing the polishing layer 4 using an isocyanate-terminated prepolymer and a curing agent includes, for example, a preparation step of preparing an isocyanate-terminated prepolymer; an isocyanate-terminated prepolymer, a curing agent, an optional additive, and an optional additive. a material preparation step for preparing hollow microspheres; a mixing step for mixing the isocyanate-terminated prepolymer, a curing agent, optional additives, and optional hollow microspheres to obtain a liquid mixture for molding the compact; ; a manufacturing method including a curing step of molding an abrasive layer from the mixture liquid for forming a molded body;

Hereinafter, the preparation process; material preparation process, mixing process, and molding process will be explained separately.

<Preparation process>
The isocyanate-terminated prepolymer used in the present invention can be obtained by reacting a polyisocyanate compound with a high molecular weight polyol such as polypropylene glycol or polyester diol, and contains an isocyanate group at the molecular end. If a commercially available isocyanate-terminated prepolymer is available, it can be used, but usually a prepolymer prepared by partially reacting a polyisocyanate compound and a polyol compound is used. There are no particular limitations on the reaction, and the addition polymerization reaction may be carried out using methods and conditions known in the production of polyurethane resins. For example, a polyisocyanate compound heated to 50°C is added to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, the temperature is raised to 80°C after 30 minutes, and the reaction is further carried out at 80°C for 60 minutes. It can be manufactured by such methods.

The NCO equivalent of the isocyanate-terminated prepolymer is not particularly limited, but is preferably 500 to 600. If it is less than 500, the defect performance may deteriorate, and if it exceeds 600, the desired polishing rate may not be obtained and the step removal performance may deteriorate.

Each component will be explained below.

(Polyisocyanate compound)
The isocyanate-terminated prepolymer uses a polyisocyanate compound as a raw material.

The polyisocyanate compound may be a commercially available one and is not particularly limited.
In this specification, the polyisocyanate compound means a compound having two or more isocyanate groups in the molecule.
The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2 , 4-TDI), 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 , ethyridine diisothiocyanate, and the like. These polyisocyanate compounds may be used alone or in combination of a plurality of polyisocyanate compounds.

The polyisocyanate compound preferably contains 2,4-TDI and/or 2,6-TDI.

(High molecular weight polyol as raw material for isocyanate-terminated prepolymer)
As used herein, "polyol" means a compound having two or more hydroxyl groups (OH) in the molecule. Moreover, "high molecular weight" refers to a molecular weight of 500 or more.
In the present invention, examples of the high molecular weight polyol as a raw material for the isocyanate-terminated prepolymer include diol compounds such as ethylene glycol, diethylene glycol (DEG), butylene glycol, triol compounds, etc.; poly(oxytetramethylene) glycol (or polytetra Examples include polyether polyol compounds such as methylene ether glycol (PTMG); and polyester diols.
Among them, from the viewpoint of being able to adjust the distance between hard segments, it is preferable to use polypropylene glycol and polyester diol in combination. Polypropylene glycol and polyester will be explained below.

The polypropylene glycol that can be used in the present invention is not particularly limited, and includes, for example, polypropylene glycol having a number average molecular weight (Mn) of 500 to 2,000, more preferably 650 to 1,000.
Note that the number average molecular weight can be measured by gel permeation chromatography (GPC). In addition, when measuring the number average molecular weight of a polyol compound from a polyurethane resin, it can also be estimated by GPC after decomposing each component by a conventional method such as amine decomposition.

In the present invention, polyester diol can be used as the high molecular weight polyol as a raw material for the isocyanate-terminated prepolymer. In this specification, polyester diol has two or more ester bonds and two hydroxyl groups (OH).
Polyester diol can be obtained, for example, by reacting a dicarboxylic acid compound and a diol compound.
Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, and dodecanedioic acid; maleic anhydride, maleic acid, and fumaric acid. unsaturated bond-containing dicarboxylic acids such as; alicyclic polycarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; orthophthalic acid, terephthalic acid, isophthalic acid, and 1,4-naphthalene dicarboxylic acid; acids, aromatic dicarboxylic acids such as 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, naphthalic acid, biphenyl dicarboxylic acid, diphenic acid, and anhydrides thereof; etc., and can be used alone or in combination. be able to.

Diol compounds used in the synthesis of polyester diol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl 1,3-propanediol, 1,3 -Butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, etc., and can be used alone or in combination. be able to.

Among the above, polyester diols of adipic acid and 1,4-butanediol and polyester diols of adipic acid and diethylene glycol are preferred.

The number average molecular weight of the polyester diol is preferably 600 to 2,500 from the viewpoint of exhibiting the rubber elasticity necessary for the polishing pad as a soft segment.

The content of polypropylene glycol is preferably less than 60% by weight based on the entire high molecular weight polyol. If it is 60% by weight or more, wear resistance may deteriorate. Preferably, the polypropylene glycol is 30-50% by weight based on the total high molecular weight polyol.
Moreover, the polyester diol is preferably 70% by weight or less based on the entire high molecular weight polyol. If it exceeds 70% by weight, the level difference elimination performance may deteriorate. Preferably, the polyester diol is 50-70% by weight based on the total high molecular weight polyol.
The total amount of polypropylene glycol and polyester diol is preferably 80% by weight or more based on the entire high molecular weight polyol. This is because if the content is 80% by weight or more, the effect will be noticeable.

In the present invention, polyoxytetramethylene glycol or the like may also be used as the high molecular weight polyol, and is preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 3% by weight based on the entire high molecular weight polyol. It is as follows. If the content exceeds 10% by weight, the level difference elimination performance and defect performance may become insufficient.

<Material preparation process>
For the production of the polishing layer 4 of the present invention, an isocyanate-terminated prepolymer, a curing agent, optional additives, and optional hollow microspheres are provided. Since the isocyanate-terminated prepolymer has been previously discussed, the curing agent, additives, and hollow microspheres will now be discussed.

(hardening agent)
In the method for manufacturing the polishing layer 4 of the present invention, a curing agent (also referred to as a chain extender) is mixed with an isocyanate-terminated prepolymer and the like in the mixing step. By adding a curing agent, the main chain end of the urethane bond-containing polyisocyanate compound can be bonded to the curing agent to form a polymer chain and cured in the subsequent molding step.
Examples of the curing agent include ethylene diamine, propylene diamine, hexamethylene diamine, isophorone diamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4-methyl -2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxy phenyl)propane, 2,2-bis[3-(isopropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2 -bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, Polyvalent amine compounds such as trimethylethylene bis-4-aminobenzonate and polytetramethylene oxide-di-p-aminobenzonate; ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, Dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-4,5-pentanediol, 2 , 2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, Examples include polyhydric alcohol compounds such as neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol. Further, the polyvalent amine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, and di-2-hydroxyethylethylenediamine. -hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, and the like. As the polyvalent amine compound, a diamine compound is preferable, and for example, it is further preferable to use 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA). preferable.

(Additive)
As a material for the polishing layer 4, additives such as an oxidizing agent can be added as necessary. In the present invention, there are no particular limitations as long as they do not inhibit the effects of the present invention.

(Hollow microspheres)
The polishing layer 4 includes, if necessary, hollow microspheres 4A having an outer shell and having a hollow interior. As described above, commercially available materials can be used for the hollow microspheres 4A. Alternatively, those obtained by synthesis by conventional methods may be used. The material for the outer shell of the hollow microspheres 4A is not particularly limited, but includes, for example, polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, Examples include polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organic silicone resins, as well as copolymers made by combining two or more types of monomers constituting these resins. Examples of commercially available hollow microspheres include, but are not limited to, the Expancel series (trade name manufactured by Akzo Nobel) and Matsumoto Microspheres (trade name manufactured by Matsumoto Yushi Co., Ltd.). It will be done.

The material of the hollow microspheres 4A is preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, and even more preferably 1 to 3 parts by weight, based on 100 parts by weight of the isocyanate-terminated prepolymer. Add to.

In addition to the above-mentioned components, conventionally used foaming agents may be used in combination with the hollow microspheres 4A to the extent that they do not impair the effects of the present invention. A reactive gas may also be blown. Examples of the blowing agent include water and a blowing agent whose main component is a hydrocarbon having 5 or 6 carbon atoms. Examples of the hydrocarbon include chain hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

The prepolymer can be produced by, for example, mixing a polyisocyanate compound, polypropylene glycol, and polyester diol and reacting them, or by mixing a mixture 1 of a polyisocyanate compound and polypropylene glycol with a polyisocyanate compound and a polyester diol. You may react by mixing mixture 2 with.

<Mixing process>
In the mixing step, the isocyanate-terminated prepolymer, curing agent, optional additives, and optional hollow microspheres obtained in the preparation step are fed into a mixer and stirred and mixed. The mixing process is carried out at a temperature that ensures the fluidity of each of the above components, but if the heating is too high, the hollow microspheres will expand and will no longer have the desired aperture distribution. ,Caution must be taken.

<Molding process>
In the molded body forming step, the mixed liquid for molding the molded body prepared in the mixing step is poured into a mold preheated to 30 to 100°C, and after it is primarily cured, it is heated at about 100 to 150°C for about 10 minutes to 5 hours. The cured polyurethane resin (polyurethane resin molded body) is molded by heating and secondary curing. At this time, the isocyanate-terminated prepolymer and the curing agent react to form a polyurethane resin foam, thereby curing the mixed liquid.
If the viscosity of the isocyanate-terminated prepolymer is too high, the fluidity will deteriorate and it will be difficult to mix substantially uniformly during mixing. If the temperature is raised to lower the viscosity, the pot life will be shortened, and uneven mixing will occur, leading to variations in the size of the hollow microspheres contained in the resulting foam. In particular, if the reaction temperature is too high, if unexpanded hollow microspheres are used, they will expand more than necessary, making it impossible to obtain the desired openings. On the other hand, if the viscosity is too low, air bubbles will move in the mixed liquid, making it difficult to obtain a foam in which the hollow microspheres are substantially uniformly dispersed. Therefore, the isocyanate-terminated prepolymer preferably has a viscosity of 500 to 4000 mPa·s at a temperature of 50 to 80°C. This can be done, for example, by changing the molecular weight (degree of polymerization) of the isocyanate-terminated prepolymer to set the viscosity. The isocyanate-terminated prepolymer is heated to about 50 to 80°C to make it flowable.

In the molding process, if necessary, the cast mixture is reacted within the mold to form a foam. At this time, the isocyanate-terminated prepolymer is crosslinked and cured by the reaction between the isocyanate-terminated prepolymer and the curing agent.

After obtaining the molded product, it is sliced into sheets to form a plurality of polishing layers 4. A general slicing machine can be used for slicing. When slicing, the lower layer portion of the polishing layer 4 is held, and the polishing layer 4 is sliced to a predetermined thickness in order from the upper layer. The thickness of slicing is set, for example, in the range of 1.3 to 2.5 mm. For a foam molded in a mold with a thickness of 50 mm, for example, approximately 10 mm of the upper and lower layers of the foam are not used due to scratches, etc., and 10 to 25 sheets are polished from approximately 30 mm of the center. Layer 4 is formed. In the curing and molding step, a foam in which hollow microspheres 4A are formed substantially uniformly is obtained.

The polished surface of the obtained polishing layer 4 may be grooved if necessary. In the present invention, the groove processing method and its shape are not particularly limited.

After that, a double-sided tape is attached to the polishing layer 4 obtained in this way on the surface opposite to the polishing surface of the polishing layer 4. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be selected and used.

<Method for manufacturing cushion layer 6>
The cushion layer 6 is preferably composed of an impregnated nonwoven fabric impregnated with resin. The resin to be impregnated into the nonwoven fabric is preferably a polyurethane type such as polyurethane and polyurethane polyurea, an acrylic type such as polyacrylate and polyacrylonitrile, a vinyl type such as polyvinyl chloride, polyvinyl acetate, and polyvinylidene fluoride, polysulfone, and polyether. Examples include polysulfone-based materials such as sulfone, acylated cellulose-based materials such as acetylated cellulose and butyrylated cellulose, polyamide-based materials, and polystyrene-based materials. The density of the nonwoven fabric before resin impregnation (web state) is preferably 0.3 g/cm ³ or less, more preferably 0.1 to 0.2 g/cm ³ . Further, the density of the nonwoven fabric after resin impregnation is preferably 0.7 g/cm ³ or less, more preferably 0.25 to 0.5 g/cm ³ . When the density of the nonwoven fabric before resin impregnation and after resin impregnation is below the above upper limit, processing accuracy is improved. Furthermore, by setting the density of the nonwoven fabric before and after resin impregnation to be at least the above lower limit, it is possible to reduce penetration of the polishing slurry into the base material layer. The adhesion rate of the resin to the nonwoven fabric is expressed as the weight of the attached resin relative to the weight of the nonwoven fabric, and is preferably 50% by weight or more, and more preferably 75 to 200% by weight. When the adhesion rate of the resin to the nonwoven fabric is below the above upper limit, desired cushioning properties can be obtained.

<Joining process>
In the bonding step, the formed polishing layer 4 and cushion layer 6 are bonded together (bonded) using an adhesive layer 7. For the adhesive layer 7, an acrylic adhesive is used, for example, and the adhesive layer 7 is formed to have a thickness of 0.1 mm. That is, an acrylic adhesive is applied to the surface of the polishing layer 4 opposite to the polishing surface to a substantially uniform thickness. The surface of the polishing layer 4 opposite to the polishing surface P and the surface of the cushion layer 6 are brought into pressure contact via the applied adhesive, and the polishing layer 4 and the cushion layer 6 are bonded together with the adhesive layer 7. After cutting into a desired shape such as a circle, the polishing pad 3 is inspected to confirm that there is no dirt or foreign matter attached thereto, and the polishing pad 3 is completed.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

In each Example and Comparative Example, "parts" means "parts by mass" unless otherwise specified.

In addition, the NCO equivalent is "(mass (parts) of polyisocyanate compound + mass (parts) of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound x mass (parts) of polyisocyanate compound / polyisocyanate Molecular weight of the compound) - (Number of functional groups per molecule of the polyol compound x Mass (parts) of the polyol compound / Molecular weight of the polyol compound)] A numerical value indicating the molecular weight of the prepolymer (PP) per NCO group. be.

(Manufacture of polishing layer)
2,4-tolylene diisocyanate (TDI) and a high molecular weight polyol are mixed in the proportions shown in Table 1 to prepare PP1 and PP2, and then mixed in the proportions shown in Table 2. To 100 parts of isocyanate group-terminated urethane prepolymer having an NCO equivalent of approximately 520, 3.5 parts of unexpanded hollow microspheres whose shell portion is made of acrylonitrile-vinylidene chloride copolymer and isobutane gas encapsulated in the shell are added. The mixture was added and mixed to obtain a mixed solution. The obtained liquid mixture was charged into a first liquid tank and kept warm. Next, separately from the first liquid, 23.1 parts of MOCA as a curing agent was charged into a second liquid tank and kept warm in the second liquid tank. The liquids in the first liquid tank and the second liquid tank are fed into a mixer equipped with two injection ports, and the equivalent ratio of the amino groups and hydroxyl groups present in the curing agent to the terminal isocyanate groups in the prepolymer is determined. The injection was performed so that the R value representing 0.90. The two injected liquids were mixed and stirred and injected into a mold of a molding machine preheated to 80° C., the mold was clamped, and the mixture was heated for 30 minutes for primary curing. After demolding the primarily cured molded product, it was secondarily cured in an oven at 120° C. for 4 hours to obtain a urethane molded product. The obtained urethane molded product was allowed to cool to 25° C., then heated again in an oven at 120° C. for 5 hours, and then sliced into 1.3 mm thick pieces to obtain polishing layers 1 to 4.

(Manufacture of cushion layer)
A nonwoven fabric made of polyester fibers was immersed in a urethane resin solution (manufactured by DIC Corporation, trade name "C1367"). After dipping, the resin solution was squeezed out using a mangle roller capable of applying pressure between a pair of rollers, so that the nonwoven fabric was substantially uniformly impregnated with the resin solution. Next, the impregnated resin was coagulated and regenerated by immersing it in a coagulation solution consisting of water at room temperature, thereby obtaining a resin-impregnated nonwoven fabric. Thereafter, the resin-impregnated nonwoven fabric was taken out from the coagulation solution, further immersed in a cleaning solution consisting of water to remove N,N-dimethylformamide (DMF) in the resin, and then dried. After drying, the surface skin layer was removed by buffing to produce a cushion layer with a thickness of 1.3 mm.

(Example and comparative example)
The polishing layers 1 to 4 and the cushion layer were bonded using double-sided tape (having an adhesive made of acrylic resin on both sides of a PET base material) having a thickness of 0.1 mm.
In Table 1, TDI is 2,4-toluene diisocyanate, PPG1000 is polypropylene glycol with a number average molecular weight of 1000, and ester is polyester diol with a number average molecular weight of 1000 obtained by reacting adipic acid and butanediol. It is.

(distance of hard segment)
The distances between the hard segments of polishing layers 1 to 4 were measured under the following measurement conditions based on the content explained above.
[Measurement condition]
Equipment: BL8S3 (Aichi Synchrotron Light Center)
Wavelength: 1.5 angstrom Measurement detector: R-AXIS IV++
Measurement time: 120sec
Measurement camera length: 3976.88mm
Measurement data for polishing layer 1 (Example 1) and polishing layer 3 (Comparative Example 1) are shown in FIGS. 3, 4, and 5. Table 3 shows the hard segment distance (HS distance) obtained from the data, the Q value at the peak time, and the transmittance.

(density)
The density (g/cm ³ ) of the polishing layer was measured in accordance with Japanese Industrial Standards (JIS K 6505).

(D hardness)
The D hardness of the polishing layer was measured using a D-type hardness meter in accordance with Japanese Industrial Standards (JIS-K-6253). Here, the measurement sample was obtained by stacking a plurality of polishing layers as necessary so that the total thickness was at least 4.5 mm.

(wear test)
The resulting polishing pad was subjected to an abrasion test using a small friction and abrasion tester under the following conditions. In the obtained abrasion test results, in Table 3, when it is 0.15 mm or less, it is written as ◯, and when it exceeds 0.15 mm, it is written as ×.

(Abrasion test conditions)
Polishing machine used: Small friction and wear tester Indenter side: PAD (17φ)
Surface plate side: #180 sandpaper load: 300g
Liquid: Water flow rate: 45ml/min Surface plate rotation speed: 40rpm
Time: 10 minutes Thickness measurement load: 300g

Examples 1 and 2, in which the hard segment distance is appropriate, show excellent wear performance, but Comparative Examples 1 and 2, in which the high molecular weight polyol in the isocyanate-terminated prepolymer uses only PPG or only ester, show good wear performance. It wasn't the result.

Using the obtained polishing pads of Examples 1 and 2 and Comparative Examples 1 and 2, a polishing test was conducted under the following polishing conditions, and the polishing performance (level difference elimination performance and defect performance) was evaluated.
(polishing conditions)
Polishing machine used: F-REX300X (manufactured by Ebara Corporation)
Disk: A188 (manufactured by 3M)
Abrasive temperature: 20℃
Polishing surface plate rotation speed: 85 rpm
Polishing head rotation speed: 86 rpm
Polishing pressure: 3.5psi
Polishing slurry (metal film): CSL-9044C (CSL-9044C stock solution: pure water = 1:9 weight ratio mixture was used) (manufactured by Fujimi Corporation)
Polishing slurry flow rate: 200ml/min
Polishing time: 60 seconds Polished object (metal film): Cu film substrate Pad break: 35N 10 minutes Conditioning: Ex-situ, 35N, 4 scans

(Level difference elimination performance test)
A polishing pad was installed at a predetermined position of a polishing device via a double-sided tape having an acrylic adhesive, and polishing was performed under the above-mentioned polishing conditions. The level difference elimination performance is measured by measuring dishing at each wiring width of 120 μm/120 μm, 100 μm/100 μm, 50 μm/50 μm, and 10 μm/10 μm using a step/surface roughness/fine shape measuring device (manufactured by KLA Tencor, P-16+). It was evaluated based on the following.
For a patterned wafer with a film thickness of 7000 angstroms and a step difference of 3000 angstroms, polishing was performed by adjusting the polishing rate so that the amount of polishing per time was 1000 angstroms. Measurements were carried out. For all wiring widths, cases where the level difference was eliminated when the amount of polishing was 6000 angstroms or less were marked as ○, and cases where the level difference was resolved after the amount of polishing exceeded 6000 angstroms or cases where the level difference was not eliminated were marked with x.

(Defect performance evaluation)
The 16th, 26th, and 51st polished substrates were inspected for defects (surface defects with a size of 155 nm or more) using the high-sensitivity measurement mode of a surface inspection device (Surfscan SP2XP, manufactured by KLA-Tencor). defect) was detected. For each detected defect, a SEM image taken using a review SEM was analyzed, and the number of scratches was counted. If the number of scratches was 10 or less, which is considered necessary in practice, it was written as ○, and if the number of scratches exceeded 10, it was written as ×.

The present invention has industrial applicability because it contributes to the manufacture and sale of polishing pads.

1 Polishing device 3 Polishing pad 4 Polishing layer 4A Hollow microspheres 6 Cushion layer 7 Adhesive layer 8 Object to be polished 9 Slurry 10 Polishing surface plate

Claims (9)

A polishing pad having a polishing layer made of a polyurethane resin foam derived from an isocyanate-terminated prepolymer and a curing agent,
A polishing pad, wherein the distance between hard segments in the polishing layer measured by small-angle X-ray scattering is 9.5 nm or less. The isocyanate-terminated prepolymer includes a polyisocyanate compound-derived structural unit and a high molecular weight polyol-derived structural unit,
The polishing pad according to claim 1, wherein the high molecular weight polyol-derived structural unit comprises at least a polypropylene glycol structural unit and a polyester diol structural unit. The polishing pad according to claim 2, wherein the polypropylene glycol structural unit is less than 60% by weight based on the structural unit derived from the high molecular weight polyol. The polishing pad according to claim 2, wherein the polyester diol for forming the polyester diol structural unit has a number average molecular weight of 600 to 2,500. The polishing pad according to claim 1, wherein the polyurethane resin foam has an average cell diameter of 5 μm or more and less than 20 μm. The polishing pad of claim 1, wherein the isocyanate-terminated prepolymer has an NCO equivalent weight of 500-600. The polishing pad according to claim 1, wherein the distance between hard segments in the polishing layer as measured by small-angle X-ray scattering is 3.0 to 9.5 nm. A method for manufacturing a polishing pad having a polishing layer made of polyurethane resin foam, the method comprising:
A step of mixing and reacting an isocyanate-terminated prepolymer with a curing agent to obtain the polyurethane resin foam;
molding the polyurethane resin foam into the shape of an abrasive layer,
A method for producing a polishing pad, wherein the distance between hard segments in the polishing layer as measured by small-angle X-ray scattering is 9.5 nm or less. 9. The method for manufacturing a polishing pad according to claim 8, wherein unexpanded balloons are also allowed to coexist when the isocyanate-terminated prepolymer and the curing agent are mixed.