Polishing pad, method for manufacturing a polishing pad, and method for polishing the surface of an optical or semiconductor material

Abstract

To provide a polishing pad which can suppress a rebound phenomenon of an object to be polished, a method for manufacturing the polishing pad, and a method for polishing a surface of an optical material or a semiconductor material using the polishing pad.SOLUTION: A polishing pad has a polishing layer containing a polyurethane resin, wherein the polyurethane resin is a cured product of a curable resin composition containing an isocyanate terminal urethane prepolymer and a curing agent; the isocyanate terminal urethane prepolymer contains an isocyanate terminal urethane prepolymer (A) and an isocyanate terminal urethane prepolymer (B); the isocyanate terminal urethane prepolymer (A) is a reaction product of a polyol component containing polyester polyol and a polyisocyanate component; the polyester polyol includes a structural unit derived from a low molecular weight polyol having a branched chain; the isocyanate terminal urethane prepolymer (B) is a reaction product of a polyol component containing polyether polyol and a polyisocyanate component; and a weight ratio ((A):(B)) of the isocyanate terminal urethane prepolymer (A) to the isocyanate terminal urethane prepolymer (B) in the isocyanate terminal urethane prepolymer is 30:70 to 70:30.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing pad, a method for manufacturing a polishing pad, and a method for polishing the surface of an optical material or a semiconductor material. The polishing pad of the present invention is used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, etc., and is particularly suitable for polishing devices in which an oxide layer, a metal layer, etc. is formed on a semiconductor wafer. [Background technology]

[0002] Optical materials, semiconductor wafers, hard disk substrates, glass substrates for liquid crystal displays, and semiconductor devices require extremely precise flatness. Hard polishing pads are commonly used to polish the surfaces of these various materials, especially the surfaces of semiconductor devices, to a flat surface. Currently, the polishing layer of many hard polishing pads typically uses a hard polyurethane material obtained by curing an isocyanate-terminated urethane prepolymer, which is the reaction product of an isocyanate component such as tolylene diisocyanate (TDI) with a polyol component containing a high molecular weight polyol such as polytetramethylene ether glycol (PTMG), with a curing agent such as 3,3'-dichloro-4,4'-diaminodiphenylmethane. The high molecular weight polyol that forms the isocyanate-terminated urethane prepolymer forms the soft segment of the polyurethane, and PTMG has traditionally been the most commonly used high molecular weight polyol due to its ease of handling and moderate rubber elasticity.

[0003] In the polishing of semiconductor devices, with the recent trend toward miniaturization and higher density of integrated circuits, a stricter level of flatness is being required for the surface of the object to be polished, especially the flatness at the edge of the object to be polished.

[0004] Fig. 1 is a cross-sectional view showing a state in which an object 20 to be polished is being polished by a polishing pad 10. Fig. 1(a) shows the state during polishing, and Fig. 1(b) shows the state after polishing has been completed. As shown in FIG. 1(a), a polished object 20 such as a semiconductor wafer is surrounded by a retainer ring 30. An air chamber 60 is provided above the retainer ring 30. The polished object 20 is placed on a polishing head 40, and an elastic film 50 is present between the polished object 20 and the polishing head 40. During polishing, the polished object 20, together with the retainer ring 30, is pressed against the surface of a polishing pad 10 at a predetermined pressure, and the polished object 20 is polished by rotating both the polished object 20 placed on the polishing head 40 and the polishing pad 10.

[0005] 1(a), the retainer ring 30 serves to prevent the workpiece 20 from jumping out to the outer periphery of the polishing head 40. However, because the retainer ring 30 is pressed against the surface of the polishing pad 10 together with the workpiece 20, this pressure can cause the polishing pad 10 to swell around the area where the retainer ring 30 comes into contact. In FIG. 1(a), an outer bulge 11 and an inner bulge 12 have been formed.

[0006] When polishing is performed using a polishing pad with a raised portion as shown in Fig. 1(a), an over-polished portion 21 may occur inside the edge of the workpiece due to the inner raised portion 12 (this is called the occurrence of a rebound phenomenon) as shown in Fig. 1(b). Furthermore, when polishing is generally performed using a retainer ring 30, an over-polished portion 22 may occur at the edge of the workpiece 20 due to contact between the retainer ring 30 and the workpiece 20 as shown in Fig. 1(b).

[0007] As will be described later, the polishing layer is formed by curing a curable resin composition containing an isocyanate-terminated urethane prepolymer and a curing agent, and reaction heat is generated during this molding. By utilizing this reaction heat, the unexpanded hollow microspheres contained in the curable resin composition can be expanded to form hollow portions with a predetermined diameter in the polishing layer. When expanding the unexpanded hollow microspheres, depending on the composition of the curable resin composition, the reaction heat generated during curing may be too large, resulting in excessive expansion of the hollow microspheres and excessively large diameters of the hollow portions in the polishing layer. If the diameter of the hollow portions in the polishing layer becomes too large, a fine foam structure will not be formed, and polishing with such a polishing layer may result in scratches on the polished object.

[0008] Regarding the flatness of the polished object, conventional polishing pads using PTMG as a high molecular weight polyol are sometimes insufficient in terms of the flatness of the polished surface, and the use of various types of high molecular weight polyols is being investigated.

[0009] Patent Document 1 discloses a polishing pad formed from a reaction-cured product of a composition containing an isocyanate-terminated prepolymer containing a polyether polyol and an isocyanate-terminated prepolymer containing a polyester polyol, the reaction-cured product having a phase-separated structure. Patent Document 1 sets forth the problem to be solved by the invention as providing a polishing pad that has a high removal rate, excellent planarization properties, and can suppress the occurrence of scratches. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-194563 Summary of the Invention [Problem to be solved by the invention]

[0011] However, Patent Document 1 only evaluates the planarization characteristics when viewing the entire surface of the workpiece to be polished, and does not focus on improving the planarization of the edge and surrounding area of ​​the workpiece to be polished. As described above, there is a demand for a polishing pad that can suppress the rebound phenomenon of the polished object (that can suppress over-polishing of the part inside the edge of the polished object).In addition to suppressing the rebound phenomenon of the polished object, there is also a demand for a polishing pad that has a small diameter of the hollow part of the polishing layer and a fine foam structure.

[0012] The present invention has been made in consideration of the above problems, and aims to provide a polishing pad that can suppress the rebound phenomenon of the polished object, a method for manufacturing such a polishing pad, and a method for polishing the surface of an optical material or a semiconductor material using such a polishing pad. Another aim is to provide a polishing pad that not only suppresses the rebound phenomenon of the polished object but also has a small diameter of the hollow part of the polishing layer and a fine foam structure, a method for manufacturing such a polishing pad, and a method for polishing the surface of an optical material or a semiconductor material using such a polishing pad. [Means for solving the problem]

[0013] As a result of intensive research aimed at solving the above problems, the present inventors have found that the above problems can be solved by using an isocyanate-terminated urethane prepolymer (A) containing a polyester polyol and an isocyanate-terminated urethane prepolymer (B) containing a polyether polyol in a weight ratio of 30:70 to 70:30, and the polyester polyol containing a structural unit derived from a low-molecular-weight polyol having a branched chain, thereby completing the present invention.Specific aspects of the present invention are as follows.

[0014] [1] A polishing pad having a polishing layer containing a polyurethane resin, 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 urethane prepolymer comprises an isocyanate-terminated urethane prepolymer (A) and an isocyanate-terminated urethane prepolymer (B); the isocyanate-terminated urethane prepolymer (A) is a reaction product of a polyol component containing a polyester polyol and a polyisocyanate component, the polyester polyol containing structural units derived from a low-molecular-weight polyol having a branched chain; the isocyanate-terminated urethane prepolymer (B) is a reaction product of a polyol component including a polyether polyol and a polyisocyanate component, The polishing pad, wherein the weight ratio ((A):(B)) of the isocyanate-terminated urethane prepolymer (A) to the isocyanate-terminated urethane prepolymer (B) in the isocyanate-terminated urethane prepolymer is 30:70 to 70:30. [2] The polishing pad according to [1], wherein the low molecular weight branched polyol contains neopentyl glycol. [3] The polishing pad according to [1] or [2], wherein the number average molecular weight of the polyester polyol in the isocyanate-terminated urethane prepolymer (A) is less than 1,000. [4] The polishing pad according to any one of [1] to [3], wherein the curable resin composition further contains hollow microspheres. [5] The polishing pad according to any one of [1] to [4], wherein the average bubble diameter of the polishing layer is 5 μm or more and less than 20 μm. [6] The polishing pad according to any one of [1] to [5], wherein the polishing layer does not have a phase-separated structure. [7] The polishing pad according to any one of [1] to [6], wherein the curing agent contains 3,3'-dichloro-4,4'-diaminodiphenylmethane. [8] The polishing pad according to any one of [1] to [7], wherein the polyisocyanate component in the isocyanate-terminated urethane prepolymer (A) contains tolylene diisocyanate. [9] The polishing pad according to any one of [1] to [8], wherein the polyisocyanate component in the isocyanate-terminated urethane prepolymer (B) contains tolylene diisocyanate.

[10] A method for producing a polishing pad according to any one of [1] to [9], comprising the step of forming the polishing layer.

[11] A method for polishing the surface of an optical material or a semiconductor material, comprising a step of polishing the surface of the optical material or the semiconductor material using the polishing pad described in any one of [1] to [9].

[0015] (definition) In this application, when a numerical range is expressed using "X to Y", the range includes the numerical values ​​X and Y at both ends. In this application, "the part inside the edge of the object to be polished" means the area extending from the outer edge of the object to be polished toward the center, which is 2 to 10% of the length between the center of the object to be polished and the outermost edge of the object to be polished (the area enclosed by the 2% line and the 10% line). In this application, the "edge of the object to be polished" means the area extending from the outer edge of the object to the center of the object to be polished by a length that is 2% of the length between the center of the object to be polished and the outermost edge of the object to be polished (the area (portion) on a line with a length of 2%). [Effects of the Invention]

[0016] The polishing pad of the present invention can suppress the rebound phenomenon of the polished object. In addition to suppressing the rebound phenomenon of the polished object, the polishing pad of the present invention can also have a fine foam structure with a small diameter of the hollow part of the polishing layer. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a state in which an object to be polished is being polished by a polishing pad. [Figure 2] FIG. 2 is a photograph showing the foam structure of the polishing layer of Example 1. [Figure 3]FIG. 3 is a photograph showing the foam structure of the polishing layer of Comparative Example 1. [Figure 4] FIG. 4 is a photograph showing the foam structure of the polishing layer of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0018] (action) The present inventors have conducted extensive research into the relationship between the isocyanate-terminated urethane prepolymer used to form the polishing layer and the flatness of the edge of the object to be polished (rebound suppression), and have unexpectedly found that by using an isocyanate-terminated urethane prepolymer containing a polyester polyol-containing isocyanate-terminated urethane prepolymer (A) and a polyether polyol-containing isocyanate-terminated urethane prepolymer (B) in a specific weight ratio, and by using the polyester polyol containing a structural unit derived from a low molecular weight polyol having a branched chain, rebound suppression can be achieved, and the edge of the object to be polished can be made excellent in flatness.The details of why such characteristics are obtained are not clear, but it is speculated as follows.

[0019] In the isocyanate-terminated urethane prepolymer (A) containing polyester polyol, the soft segments contain structural units derived from the polyester polyol, and therefore the presence of ester groups is thought to result in a relatively high cohesive strength of the soft segments. Furthermore, because the polyester polyol contains structural units derived from a low-molecular-weight polyol having a branched chain, the presence of the branched chains is thought to result in a tendency for the cohesive strength of the soft segments to be lower than that of a polyol that does not contain a branched chain. On the other hand, in the isocyanate-terminated urethane prepolymer (B) containing polyether polyol, the soft segments contain structural units derived from polyether polyol, and therefore the cohesive strength of the soft segments is thought to be relatively low due to the presence of ether groups. The fact that the cohesive strength of the soft segments in the isocyanate-terminated urethane prepolymer (A) containing polyester polyol is relatively high, the fact that structural units derived from low-molecular-weight polyols with branched chains tend to reduce the cohesive strength of the soft segments, and the fact that the cohesive strength of the soft segments in the isocyanate-terminated urethane prepolymer (B) containing polyether polyol interact with each other, and as a result, by setting the weight ratio of the isocyanate-terminated urethane prepolymer (A) to the isocyanate-terminated urethane prepolymer (B) to a specific ratio, the cohesive strength of the soft segments in the entire isocyanate-terminated prepolymer becomes appropriate. As a result, when used as a polishing pad, it is thought that the rebound phenomenon can be suppressed and the edge of the object to be polished will have excellent flatness.

[0020] The polishing layer of the polishing pad can also be one that does not have a phase-separated structure. The absence of a phase-separated structure in the polishing layer of the polishing pad can further suppress the rebound phenomenon, resulting in even better flatness of the edge of the polished object. The details of why such characteristics are obtained are not clear, but it is presumed that the absence of a phase-separated structure in the polishing layer of the polishing pad allows the soft segments with the above-mentioned moderate cohesive force to be uniformly distributed throughout the polishing layer, enabling the surface of the polished object, including the edge, to be uniformly polished.

[0021] The polishing pad of the present invention, the method for manufacturing the polishing pad, and the method for polishing the surface of an optical material or a semiconductor material will be described below.

[0022] 1. Polishing pads and manufacturing methods for polishing pads In some embodiments of the present application, the polishing pad has a polishing layer comprising a polyurethane resin, 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 urethane prepolymer comprises an isocyanate-terminated urethane prepolymer (A) and an isocyanate-terminated urethane prepolymer (B); the isocyanate-terminated urethane prepolymer (A) is a reaction product of a polyol component containing a polyester polyol and a polyisocyanate component, the polyester polyol containing structural units derived from a low-molecular-weight polyol having a branched chain; the isocyanate-terminated urethane prepolymer (B) is a reaction product of a polyol component including a polyether polyol and a polyisocyanate component, In the isocyanate-terminated urethane prepolymer, the weight ratio ((A):(B)) of the isocyanate-terminated urethane prepolymer (A) to the isocyanate-terminated urethane prepolymer (B) is 30:70 to 70:30. The polishing pad has a weight ratio of 30:70 to 70:30 between the isocyanate-terminated urethane prepolymer (A) containing polyester polyol and the isocyanate-terminated urethane prepolymer (B) containing polyether polyol, and the polyester polyol contains structural units derived from a low-molecular-weight polyol having a branched chain, thereby suppressing the rebound phenomenon of the polished object. Furthermore, by having the above-mentioned configuration, the polishing pad can not only suppress over-polishing of the portion inside the edge of the polished object, but also has a small diameter of the hollow portion of the polishing layer and a fine foam structure.

[0023] The polishing pad of the present application has a polishing layer containing a polyurethane resin. The polishing layer is positioned in direct contact with the material to be polished, and the remaining parts of the polishing pad may be made of a material for supporting the polishing pad, for example, a highly elastic material such as rubber. Depending on the rigidity of the polishing pad, the polishing layer can be used as a polishing pad.

[0024] The polishing pad of the present application is not significantly different in shape from a general polishing pad, except that it can prevent over-polishing of the part inside the edge of the workpiece, and can be used in the same way as a general polishing pad. For example, the polishing pad can be rotated while the polishing layer is pressed against the workpiece to be polished, or the workpiece can be rotated while the polishing layer is pressed against the polishing layer to polish it.

[0025] The polishing pad of the present application can be produced by commonly known manufacturing methods such as molding, slab molding, etc. First, a polyurethane block is formed by such a manufacturing method, and the block is sliced ​​into a sheet, and an abrasive layer made of polyurethane resin is formed and attached to a support or the like. Alternatively, the abrasive layer can be formed directly on the support.

[0026] More specifically, a double-sided tape is attached to the polishing layer on the side opposite the polishing surface of the polishing layer, and the polishing pad is cut into a predetermined shape. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be selected and used. The polishing pad may have a single-layer structure consisting of only the polishing layer, or may have a multi-layer structure in which another layer (underlayer, support layer) is attached to the side opposite the polishing surface of the polishing layer.

[0027] The polishing layer is formed by preparing a curable resin composition containing an isocyanate-terminated urethane prepolymer and a curing agent, and curing the curable resin composition. The polishing layer can be made of a foamed polyurethane resin, and foaming can be performed by dispersing a foaming agent containing hollow microspheres in the polyurethane resin. In this case, a curable resin composition containing an isocyanate-terminated urethane prepolymer, a curing agent, and a foaming agent is prepared, and the curable resin composition is foamed and cured to form the polishing layer. The curable resin composition can also be a two-component composition prepared by mixing, for example, a liquid A containing an isocyanate-terminated urethane prepolymer and a liquid B containing a curing agent component. The other components can be added to either liquid A or liquid B, but if problems arise, the composition can be further divided into multiple liquids and mixed to form a composition consisting of three or more liquids.

[0028] (1) Isocyanate-terminated urethane prepolymer The isocyanate-terminated urethane prepolymer in some embodiments of the present application is a product obtained by reacting a polyol component with a polyisocyanate component.

[0029] (1-1) Isocyanate-terminated urethane prepolymer (A) The isocyanate-terminated urethane prepolymer (A) contained in the isocyanate-terminated urethane prepolymer is a reaction product of a polyol component containing a polyester polyol and a polyisocyanate component, and the polyester polyol contains structural units derived from a low-molecular-weight polyol having a branched chain.

[0030] (Polyol component contained in isocyanate-terminated urethane prepolymer (A)) The polyol component in the isocyanate-terminated urethane prepolymer (A) includes a polyester polyol. The isocyanate-terminated urethane prepolymer (A) may contain no polyol component other than polyester polyol (the polyol component may be composed of polyester polyol), or may contain a polyol component other than polyester polyol. When the isocyanate-terminated urethane prepolymer (A) contains a polyol component other than polyester polyol, the polyol component other than polyester polyol is not particularly limited, but may be a low-molecular-weight polyol, a high-molecular-weight polyol other than polyester polyol, or a combination thereof.

[0031] (polyester polyol) The polyester polyol contained in the isocyanate-terminated urethane prepolymer (A) is a reaction product of a polycarboxylic acid component and a polyol component, and is a type of high-molecular-weight polyol. In this application, a high-molecular-weight polyol is a polyol having a number-average molecular weight of more than 300.

[0032] The polycarboxylic acid component contained in the polyester polyol is not particularly limited, and examples thereof 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; unsaturated bond-containing dicarboxylic acids such as maleic anhydride, maleic acid, and fumaric acid; alicyclic polycarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as orthophthalic acid, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, diphenic acid, and anhydrides thereof; and combinations of two or more of these. Of these polycarboxylic acid components, adipic acid is preferred. The polycarboxylic acid component contained in the polyester polyol may also be made of adipic acid.

[0033] The polyester polyol contains structural units derived from a low-molecular-weight polyol having a branched chain. In the present application, the low-molecular-weight polyol is a polyol having a number-average molecular weight of 30 to 300.

[0034] The polyol component contained in the polyester polyol includes a low-molecular-weight polyol having a branched chain. Examples of the low-molecular-weight polyol having a branched chain include, but are not limited to, branched alkanediols having 2 to 9 carbon atoms, such as 1,2-propanediol, 1,3-butanediol, neopentyl glycol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, 1,2-hexanediol, and combinations of two or more thereof. Among these, neopentyl glycol is preferred from the viewpoint of suppressing cohesion. The polyol component contained in the polyester polyol may also be made of a low-molecular-weight polyol having a branched chain.

[0035] The content of structural units derived from a low-molecular-weight polyol having a branched chain (a low-molecular-weight polyol having a branched chain) relative to the total polyester polyol is not particularly limited, but is preferably 20 to 60% by weight, more preferably 25 to 55% by weight, and most preferably 30 to 50% by weight.

[0036] The polyol component contained in the polyester polyol may or may not contain a low-molecular-weight polyol other than the low-molecular-weight polyol having a branched chain. Examples of the low-molecular-weight polyol other than the low-molecular-weight polyol having a branched chain include, but are not limited to, ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and combinations of two or more thereof.

[0037] The content of low-molecular-weight polyols other than branched low-molecular-weight polyols relative to the total polyester polyol is not particularly limited, but is preferably 0 to 10% by weight, more preferably 0 to 7% by weight, and most preferably 0 to 5% by weight. Alternatively, the content of low-molecular-weight polyols other than the branched low-molecular-weight polyols can be 0% by weight (no low-molecular-weight polyols other than the branched low-molecular-weight polyols). In this application, "not containing" means that a certain component is not intentionally added, and does not exclude its inclusion as an impurity.

[0038] The number average molecular weight of the polyester polyol is not particularly limited, but is preferably less than 1,000, more preferably 500 to 950, and most preferably 600 to 900, from the viewpoint of the mechanical strength of the polishing layer.

[0039] The content of the polyester polyol relative to the total isocyanate-terminated urethane prepolymer (A) is not particularly limited, but is preferably 30 to 70% by weight, more preferably 35 to 65% by weight, and most preferably 40 to 60% by weight.

[0040] (Polyol components other than polyester polyol) The low-molecular-weight polyol contained in the isocyanate-terminated urethane prepolymer (A) (other than the polyol component constituting the polyester polyol) is not particularly limited, but examples include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,2-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, and combinations of two or more thereof. Examples of high molecular weight polyols other than the polyester polyols contained in the isocyanate-terminated urethane prepolymer (A) include: Polycarbonate polyols; polycaprolactone polyols; or combinations thereof.

[0041] The content of the low molecular weight polyol (other than the polyol component constituting the polyester polyol) relative to the entire isocyanate-terminated urethane prepolymer (A) is not particularly limited, but is preferably 1 to 10% by weight, more preferably 2 to 9% by weight, and most preferably 3 to 8% by weight.

[0042] The content of the high molecular weight polyol other than polyester polyol relative to the total isocyanate-terminated urethane prepolymer (A) is not particularly limited, but is preferably 0 to 10% by weight, more preferably 0 to 7% by weight, and most preferably 0 to 5% by weight. Alternatively, the content of the high molecular weight polyol other than polyester polyol can be 0% by weight (no high molecular weight polyol other than polyester polyol is included).

[0043] (Polyisocyanate component contained in isocyanate-terminated urethane prepolymer (A)) The polyisocyanate component contained in the isocyanate-terminated urethane prepolymer (A) is: For example, 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-phenylenediisothiocyanate, xylylene-1,4-diisothiocyanate, ethylidine diisothiocyanate, or a combination of two or more thereof. Among these, from the viewpoint of polishing properties, it is preferable to use tolylene diisocyanates such as 2,6-tolylene diisocyanate (2,6-TDI) and 2,4-tolylene diisocyanate (2,4-TDI).

[0044] The content of the polyisocyanate component relative to the entire isocyanate-terminated urethane prepolymer (A) is not particularly limited, but is preferably 30 to 60% by weight, more preferably 33 to 57% by weight, and most preferably 35 to 55% by weight.

[0045] The NCO equivalent (g / eq) of the isocyanate-terminated urethane prepolymer (A) is preferably less than 600, more preferably 350 to 550, and most preferably 400 to 500. When the NCO equivalent (g / eq) is within the above range, the polishing layer can have an appropriate hardness, and the rebound phenomenon can be suppressed.

[0046] The number average molecular weights of the polyester polyol, the high molecular weight polyol, and the low molecular weight polyol in the isocyanate-terminated urethane prepolymer (A) can be measured as polyethylene glycol / polyethylene oxide (PEG / PEO) equivalent molecular weights by gel permeation chromatography (GPC) under the following conditions: The number average molecular weight of each polyol described below can also be measured as a PEG / PEO equivalent molecular weight under the same conditions. <Measurement conditions> Column: Ohpak SB-802.5HQ (exclusion limit 10,000) + SB-803HQ (exclusion limit 100,000) Mobile phase: 5mM LiBr / DMF Flow rate: 0.3ml / min (26kg / cm 2 ) Oven: 60℃ Detector: RI 40℃ Sample volume: 20 μl

[0047] (1-2) Isocyanate-terminated urethane prepolymer (B) The isocyanate-terminated urethane prepolymer (B) contained in the isocyanate-terminated urethane prepolymer is a reaction product of a polyol component containing a polyether polyol and a polyisocyanate component. The isocyanate-terminated urethane prepolymer (B) may or may not contain a polyol component other than the polyether polyol. When the isocyanate-terminated urethane prepolymer (B) contains a polyol component other than the polyether polyol, the polyol component other than the polyether polyol is not particularly limited, but may be a low-molecular-weight polyol, a high-molecular-weight polyol other than the polyether polyol, or a combination thereof. The polyol component contained in the isocyanate-terminated urethane prepolymer (B) may also be composed of a polyether polyol and a low-molecular-weight polyol.

[0048] (Polyether polyol) The polyether polyol contained in the isocyanate-terminated urethane prepolymer (B) is a type of high molecular weight polyol. The polyether polyol contained in the isocyanate-terminated urethane prepolymer (B) is not particularly limited, but examples thereof include polytetramethylene ether glycol (PTMG), polyethylene glycol, polypropylene glycol, or a combination of two or more thereof. Among these, from the viewpoint of the mechanical strength of the polishing layer, PTMG is preferred, and a combination of two PTMGs with different number average molecular weights is particularly preferred.

[0049] The number-average molecular weight of the polyether polyol is not particularly limited, but from the viewpoint of the mechanical strength of the polishing layer, it is preferably 500 to 2500, more preferably 550 to 2000, and most preferably 600 to 1500. The polyether polyol contained in the isocyanate-terminated urethane prepolymer (B) may be two types of polyether polyols having different number-average molecular weights, and the number-average molecular weights of these two types of polyether polyols may be within the respective numerical ranges described above.

[0050] The content of the polyether polyol relative to the total isocyanate-terminated urethane prepolymer (B) is not particularly limited, but is preferably 30 to 60% by weight, more preferably 35 to 55% by weight, and most preferably 40 to 50% by weight.

[0051] (Polyol components other than polyether polyols) The low-molecular-weight polyol contained in the isocyanate-terminated urethane prepolymer (B) is not particularly limited, and examples thereof include the compounds described above in the section on the isocyanate-terminated urethane prepolymer (A) (polyol components other than polyester polyols), or combinations of two or more of these. Among these, diethylene glycol is preferred from the viewpoint of adjusting the NCO equivalent of the prepolymer. Examples of high molecular weight polyols other than the polyether polyols contained in the isocyanate-terminated urethane prepolymer (B) include: Polycarbonate polyols; polycaprolactone polyols; or a combination of two or more thereof.

[0052] The content of the low molecular weight polyol relative to the total isocyanate-terminated urethane prepolymer (B) is not particularly limited, but is preferably 1 to 10% by weight, more preferably 2 to 9% by weight, and most preferably 3 to 8% by weight.

[0053] The content of the high molecular weight polyol other than polyether polyol relative to the total isocyanate-terminated urethane prepolymer (B) is not particularly limited, but is preferably 0 to 10% by weight, more preferably 0 to 7% by weight, and most preferably 0 to 5% by weight. Alternatively, the content of the high molecular weight polyol other than polyether polyol can be 0% by weight (not including low molecular weight polyol other than the above-mentioned low molecular weight polyol having a branched chain).

[0054] (Polyisocyanate component contained in isocyanate-terminated urethane prepolymer (B)) Examples of the polyisocyanate component contained in the isocyanate-terminated urethane prepolymer (B) include the compounds described above in the section (Polyisocyanate component contained in the isocyanate-terminated urethane prepolymer (A)), or a combination of two or more of these compounds. Among these, from the viewpoint of polishing properties, it is preferable to use tolylene diisocyanates such as 2,6-tolylene diisocyanate (2,6-TDI) and 2,4-tolylene diisocyanate (2,4-TDI).

[0055] The content of the polyisocyanate component relative to the entire isocyanate-terminated urethane prepolymer (B) is not particularly limited, but is preferably 35 to 65% by weight, more preferably 40 to 60% by weight, and most preferably 45 to 55% by weight.

[0056] The NCO equivalent (g / eq) of the isocyanate-terminated urethane prepolymer (B) is preferably less than 600, more preferably 350 to 550, and most preferably 400 to 500. When the NCO equivalent (g / eq) is within the above range, the polishing layer can have an appropriate hardness, and the rebound phenomenon can be suppressed.

[0057] In the isocyanate-terminated urethane prepolymer, the weight ratio ((A):(B)) of the isocyanate-terminated urethane prepolymer (A) to the isocyanate-terminated urethane prepolymer (B) is 30:70 to 70:30, preferably 40:60 to 65:35, and most preferably 50:50 to 60:40. When the weight ratio of the isocyanate-terminated urethane prepolymer (A) to the isocyanate-terminated urethane prepolymer (B) is within the above range, the average cell diameter of the polishing layer can be controlled to obtain a fine foam structure while maintaining an appropriate curing reaction rate of the curable resin composition.

[0058] (2) Hardener Examples of the curing agent contained in the curable resin composition include the amine-based curing agents described below. Examples of polyamines that constitute amine-based curing agents include diamines, such as alkylenediamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; diamines having an aliphatic ring such as isophoronediamine and dicyclohexylmethane-4,4'-diamine; diamines having an aromatic ring such as 3,3'-dichloro-4,4'-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA); diamines having hydroxyl groups, particularly hydroxyalkyl alkylenediamines, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine; or combinations of two or more of these. Trifunctional triamine compounds and polyamine compounds with four or more functional groups can also be used.

[0059] A particularly preferred amine-based curing agent is the above-mentioned MOCA, the chemical structure of which is as follows:

[0060] [ka]

[0061] The total amount of curing agent used is such that the ratio of the number of moles of active hydrogen groups (such as NH2) in the curing agent to the number of moles of NCO in the isocyanate-terminated urethane prepolymer (number of moles of NH2 / number of moles of NCO) is preferably 0.7 to 1.1, more preferably 0.75 to 1.0, and most preferably 0.8 to 0.95.

[0062] (3) Micro-hollow spheres In some embodiments, the curable resin composition can further comprise hollow microspheres. Foams can be formed by mixing hollow microspheres with polyurethane resin. Examples of hollow microspheres include unfoamed heat-expandable microspheres consisting of a thermoplastic resin outer shell (polymer shell) and a low-boiling hydrocarbon encapsulated within the shell, spheres obtained by thermally expanding the unfoamed heat-expandable microspheres, and combinations thereof. The polymer forming the polymer shell can be a thermoplastic resin, such as an acrylonitrile-vinylidene chloride copolymer, an acrylonitrile-methyl methacrylate copolymer, a vinyl chloride-ethylene copolymer, or a combination of two or more of these. The low-boiling hydrocarbon encapsulated within the polymer shell can be, for example, isobutane, pentane, isopentane, petroleum ether, or a combination of two or more of these.

[0063] (4) Other ingredients In addition, catalysts and the like generally used in the industry may be added to the curable resin composition. Furthermore, the above-mentioned polyisocyanate component can also be added later to the curable resin composition, and the weight ratio of the additional polyisocyanate component to the total weight of the isocyanate-terminated urethane prepolymer and the additional polyisocyanate component is preferably 0.1 to 10 wt %, more preferably 0.5 to 8 wt %, and particularly preferably 1 to 5 wt %. As the polyisocyanate component additionally added to the polyurethane resin curable composition, the above-mentioned polyisocyanate components can be used without any particular limitation, but 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI) is preferred.

[0064] (5) Polishing layer (average bubble diameter) In some embodiments of the present application, the average cell diameter of the polishing layer is not particularly limited, but is preferably 5 μm or more and less than 20 μm, more preferably 6 to 19 μm, and most preferably 7 to 18 μm. By setting the average cell diameter of the polishing layer within the above numerical range, the polishing layer will have a fine foam structure, which can prevent scratches during polishing. The average cell diameter of the polishing layer can be measured by the measurement method and conditions described in (2) Foamed Structure in (Evaluation Method) of [Examples] below.

[0065] The method for controlling the average bubble diameter of the polishing layer is not particularly limited. For example, the predetermined average bubble diameter can be achieved by using the unfoamed heat-expandable microspheres described above in a curable resin composition and controlling the heating temperature and reaction heat. When a curable resin composition containing an isocyanate-terminated prepolymer and a curing agent is cured to form a polishing layer, the use of an isocyanate-terminated prepolymer containing a polyester polyol component as the isocyanate-terminated prepolymer generates a larger reaction heat during curing due to the ester groups, compared to the use of an isocyanate-terminated prepolymer containing a polyether polyol component, which is believed to result in a larger heat generation during molding. High heat generation during molding leads to a larger expansion of the unfoamed heat-expandable microspheres, which results in a larger average cell diameter in the polishing layer and an inability to obtain a finely foamed structure. In some embodiments of the present application, the weight ratio of the isocyanate-terminated urethane prepolymer (A) (an isocyanate-terminated prepolymer containing a polyester polyol component) to the isocyanate-terminated urethane prepolymer (B) (an isocyanate-terminated prepolymer containing a polyether polyol component) is set to 30:70 to 70:30, thereby controlling the average cell diameter of the polishing layer and obtaining a finely foamed structure while maintaining a moderate curing reaction rate.

[0066] (structure) In some embodiments of the present application, the polishing layer preferably does not have a phase-separated structure, which allows the polishing layer as a whole to have uniform physical properties and is effective in suppressing the rebound phenomenon of the polished object. In this application, a state in which the polishing layer has a phase-separated structure means that when a square area with one side of 0.6 mm is observed on the surface of the polishing layer using a laser microscope (VK-X1000, manufactured by KEYENCE) at a magnification of 500x, the multiple components are not completely compatible and some or all of them are separated, for example, like a sea-island structure. In some embodiments of the present invention, the weight ratio of the isocyanate component of the isocyanate-terminated prepolymer is adjusted to use an isocyanate-terminated urethane prepolymer containing a polyester polyol component in combination with an isocyanate-terminated urethane prepolymer containing a polyether polyol component, the polyester polyol contains structural units derived from a low-molecular-weight polyol having a branched chain, and the number-average molecular weight of the polyol component of the isocyanate-terminated prepolymer is adjusted, thereby reducing the difference in reactivity between the isocyanate-terminated prepolymer and the curing agent and making the polishing layer have no phase-separated structure. Furthermore, by adjusting the difference in solubility of the isocyanate-terminated prepolymers used in combination, the polishing layer can be made to have no phase-separated structure.

[0067] 2. Method for polishing the surface of optical or semiconductor materials In some embodiments of the present application, a method of polishing a surface of an optical or semiconductor material includes polishing the surface of the optical or semiconductor material using the polishing pad described above. In some embodiments of the present application, the method of polishing a surface of an optical or semiconductor material can further include applying a slurry to the surface of the polishing pad, the surface of the optical or semiconductor material, or both.

[0068] (slurry) The liquid component contained in the slurry is not particularly limited, but may include water (pure water), acid, alkali, organic solvent, or a combination thereof, and is selected depending on the material of the workpiece to be polished, the desired polishing conditions, etc. The slurry preferably contains water (pure water) as its main component, and preferably contains 80% by weight or more of water based on the total weight of the slurry. The abrasive component contained in the slurry is not particularly limited, but may include silica, zirconium silicate, cerium oxide, aluminum oxide, manganese oxide, or a combination thereof. The slurry may contain other components such as organic substances soluble in the liquid component and pH adjusters. [Example]

[0069] The present invention will be experimentally explained by the following examples, but the following explanation is not intended to limit the scope of the present invention to the following examples.

[0070] (material) The materials used in Examples 1 to 3 and Comparative Examples 1 and 2 described below are listed below.

[0071] Isocyanate-terminated urethane prepolymer: Prepolymer (1) - A urethane prepolymer having an NCO equivalent of 420, containing 2,4-tolylene diisocyanate as a polyisocyanate component, a polyester polyol (a reaction product of adipic acid and neopentyl glycol) having a number average molecular weight of 800 as a high molecular weight polyol component, and diethylene glycol as a low molecular weight polyol component (the contents of 2,4-tolylene diisocyanate, polyester polyol having a number average molecular weight of 800, and low molecular weight polyol (diethylene glycol) other than the polyol constituting the polyester polyol were 44% by weight, 50% by weight, and 6% by weight, respectively, relative to the total amount of prepolymer (1). Prepolymer (2)—A urethane prepolymer having an NCO equivalent of 460, containing 2,4-tolylene diisocyanate as a polyisocyanate component, polytetramethylene ether glycol having a number average molecular weight of 650 and polytetramethylene ether glycol having a number average molecular weight of 850 as high-molecular-weight polyol components, and diethylene glycol as a low-molecular-weight polyol component (the contents of 2,4-tolylene diisocyanate, the total of polytetramethylene ether glycol having a number average molecular weight of 650 and polytetramethylene ether glycol having a number average molecular weight of 850, and diethylene glycol were 38% by weight, 58% by weight, and 4% by weight, respectively, relative to the total content of prepolymer (2). Prepolymer (3)—A urethane prepolymer having an NCO equivalent of 420, containing 2,4-tolylene diisocyanate as a polyisocyanate component, polytetramethylene ether glycol having a number average molecular weight of 650 and polytetramethylene ether glycol having a number average molecular weight of 850 as high-molecular-weight polyol components, and diethylene glycol as a low-molecular-weight polyol component (the contents of 2,4-tolylene diisocyanate, the total of polytetramethylene ether glycol having a number average molecular weight of 650 and polytetramethylene ether glycol having a number average molecular weight of 850, and diethylene glycol were 42% by weight, 52% by weight, and 6% by weight, respectively, relative to the total content of prepolymer (3). Prepolymer (4) - A urethane prepolymer having an NCO equivalent of 420, containing 2,4-tolylene diisocyanate as a polyisocyanate component, a polyester polyol (a reaction product of adipic acid and 1,4-butanediol) having a number average molecular weight of 800 as a high molecular weight polyol component, and diethylene glycol as a low molecular weight polyol component (the contents of 2,4-tolylene diisocyanate, polyester polyol having a number average molecular weight of 800, and low molecular weight polyol (diethylene glycol) other than the polyol constituting the polyester polyol were 44% by weight, 50% by weight, and 6% by weight, respectively, relative to the total content of prepolymer (4).

[0072] Hardener: MOCA···3,3'-dichloro-4,4'-diaminodiphenylmethane (also known as methylenebis-o-chloroaniline) (MOCA) (NH2 equivalents = 133.5)

[0073] Micro-hollow spheres: Expancel 461DU20 (Nippon Phillite Co., Ltd.) (unexpanded type, average diameter in unexpanded state: 6-9 μm)

[0074] Example 1 70.0 g of prepolymer (1) and 30.0 g of prepolymer (2) were prepared as component A, 26.8 g of the curing agent MOCA as component B, and 3.5 g of hollow microspheres (Expancel 461DU20) as component C. Note that the amounts are listed in grams to indicate the ratio of each component, but it is sufficient to prepare the required weight (parts) depending on the size of the block. Below, the amounts will also be listed in grams (parts). The A component and the C component were mixed, and the resulting mixture of the A component and the C component was degassed under reduced pressure. The B component, MOCA, was degassed under reduced pressure. The degassed mixture of the A component and the C component and the degassed B component were fed into a mixer to obtain a mixture of the A component, the B component, and the C component. In the resulting mixture of the A component, the B component, and the C component, the ratio of the number of moles of NH2 of the MOCA of the B component to the sum of the number of moles of NCO of the A component prepolymer (1) and the number of moles of NCO of the prepolymer (2) (number of moles of NH2 / number of moles of NCO) was 0.9. In the resulting mixture of the A component, the B component, and the C component, the weight ratio of the prepolymer (1) to the prepolymer (2) was 70:30. The resulting mixture of components A, B, and C was poured into a mold (850 mm x 850 mm square) heated to 80°C and subjected to primary curing at 80°C for 30 minutes. The formed resin foam was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours. The resulting resin foam was allowed to cool to 25°C and then heated again in an oven at 120°C for 5 hours. The resulting resin foam was sliced ​​in the thickness direction to a thickness of 1.3 mm to prepare a urethane sheet, and double-sided tape was attached to the back of this urethane sheet to prepare a polishing pad.

[0075] (Comparative Example 1) A urethane sheet was prepared in the same manner as in Example 1, except that 70.0 g of prepolymer (1) as component A, 26.8 g of MOCA as component B, and 3.5 g of hollow microspheres (Expancel461DU20) as component C in Example 1 were replaced with 70.0 g of prepolymer (4), 27.5 g of MOCA, and 3.6 g of hollow microspheres (Expancel461DU20), respectively, to obtain a polishing pad of Comparative Example 1. In the obtained mixture of components A, B, and C, the ratio of the number of moles of NH2 of MOCA in component B to the sum of the number of moles of NCO of prepolymer (4) in component A and the number of moles of NCO of prepolymer (2) (number of moles of NH2 / number of moles of NCO) was 0.9. In the obtained mixture of components A, B, and C, the weight ratio of prepolymer (4) to prepolymer (2) was 70:30.

[0076] (Comparative Example 2) In place of the A component prepolymer (1) 70.0 g and prepolymer (2) 30.0 g, B component MOCA 26.8 g, and C component micro hollow spheres (Expancel461DU20) 3.5 g in Example 1, only 100.0 g of prepolymer (3) as A component, 28.1 g of MOCA, and 2.8 g of micro hollow spheres (Expancel461DU20) were used, respectively. A urethane sheet was prepared in the same manner as in Example 1, and a polishing pad of Comparative Example 2 was obtained. In the obtained mixed solution of components A, B, and C, the ratio of the number of moles of NH2 in MOCA, component B, to the number of moles of NCO in prepolymer (3), component A (number of moles of NH2 / number of moles of NCO) was 0.9.

[0077] (Evaluation method) The polishing pads of Example 1 and Comparative Examples 1 and 2 were evaluated for (1) flatness of the edge of the object to be polished, and (2) foam structure. The evaluation results are shown in Tables 3 to 5 below.

[0078] (1) Flatness of the edge of the workpiece Each polishing pad was placed in a predetermined position on a polishing device using double-sided tape with an acrylic adhesive, and the TEOS-coated silicon wafer was polished using the device and conditions described in the <Polishing Conditions> below. The polished TEOS-coated silicon wafers were observed using an optical film thickness and quality analyzer (KLA-Tencor, ASET-F5x) in DBS mode to measure the removal rate (unit: Å). The removal rate was measured at the center of the TEOS-coated silicon wafer, the area (portion) inside the edge of the TEOS-coated silicon wafer (the area extending from the outer edge of the polished object toward the center, a distance of 2-10% of the distance between the center and the outermost edge of the polished object (the area enclosed by the 2% and 10% lines)), and the area (portion) at the edge of the TEOS-coated silicon wafer (the area extending from the outer edge of the polished object toward the center, a distance of 2% of the distance between the center and the outermost edge of the polished object (the area (portion) on the 2% line)). The polishing conditions in the areas inside the edge and at the edge were evaluated according to the following evaluation criteria. The results are shown in Tables 3 and 5.

[0079] <Polishing conditions> Polishing machine: F-REX300X (manufactured by Ebara Corporation) Disk: A188 (3M) Retainer ring: Retainer ring GXKD (manufactured by Ebara Corporation) Rotation speed: (Surface plate) 90 rpm, (Polishing head) 81 rpm Grinding pressure: 3.5psi Polishing agent temperature: 20℃ Abrasive discharge rate: 200 ml / min Abrasive: PL6115 (Fujimi Incorporated) Polishing object: TEOS (Tetra Ethyl Ortho Silicate) coated silicon wafer (300mm diameter disk) Polishing time: 60 seconds Pad break: 32N 20 minutes Conditioning: In-situ 18N 16 scans, Ex-situ 32N 4 scans

[0080] [Table 1]

[0081] (2) Foam structure Nine square areas, each 0.6 mm on a side, were selected uniformly from the entire surface of the polishing layer (urethane sheet) of each polishing pad. Images of each area were taken at 400x magnification using a laser microscope (VK-X1000, Keyence). The nine images were then binarized using image processing software (WinROOF2018 Ver. 4.0.2, Mitani Shoji). The pores in the nine binarized images were then examined to determine the presence or absence of excessively expanded hollow areas of 100 μm or more and the average diameter of the hollow areas resulting from the expansion of the micro-hollow spheres. The cutoff value (lower limit) for the pore diameter was set to 5 μm to eliminate noise. The average diameter of the bubbles represents the average diameter of the pores visible in the laser microscope images. The results are shown in Tables 4 and 5. The hollow areas were then evaluated based on the following evaluation criteria. 2 to 4 (corresponding to Example 1, Comparative Example 1, and Comparative Example 2, respectively) show images before the binarization process.

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] [Table 5]

[0086] Example 1 relates to a polishing pad in which the weight ratio of an isocyanate-terminated urethane prepolymer (1) containing a polyester polyol to an isocyanate-terminated urethane prepolymer (2) containing a polyether polyol is 30:70 to 70:30, and the polyester polyol contains structural units derived from a low-molecular-weight polyol having a branched chain. Comparative Example 1 relates to a polishing pad in which the weight ratio of an isocyanate-terminated urethane prepolymer (4) containing a polyester polyol to the isocyanate-terminated prepolymer (2) is 70:30, and the polyester polyol contains unbranched 1,4-butanediol. Comparative Example 2 relates to a polishing pad in which the isocyanate-terminated urethane prepolymer contains only the isocyanate-terminated urethane prepolymer (3) containing the polyether polyol.

[0087] From the results of Tables 3 and 5, it was found that the polishing pad of Example 1 can suppress over-polishing of the inner region of the edge of the workpiece (can suppress the rebound phenomenon) and has excellent flatness of the edge of the workpiece after polishing. It was also found that these polishing pads can suppress over-polishing of the edge region of the workpiece. On the other hand, the polishing pads of Comparative Examples 1 and 2 were found to have over-polished the inner area of ​​the edge of the workpiece, resulting in poor flatness of the edge of the workpiece after polishing. These polishing pads also had over-polished the edge area of ​​the workpiece.

[0088] Furthermore, the results in Tables 4 and 5 show that the polishing pads of Example 1 and Comparative Example 2 have a small average diameter of the hollow portions and a fine foam structure. By reducing the average diameter of the hollow portions in the polishing layer to form a fine foam structure, the occurrence of scratches during polishing can be suppressed. On the other hand, it was found that the polishing pad of Comparative Example 1 contained excessively expanded micro hollow spheres, and a finely foamed structure was not obtained.

[0089] Furthermore, when evaluation was carried out in accordance with the criteria for the presence or absence of a phase separation structure described in the above item (structure), it was found that the polishing pads of Example 1 and Comparative Example 2 did not have a phase separation structure, while the polishing pad of Comparative Example 1 did have a phase separation structure.

[0090] From the above, it was found that a polishing pad in which the weight ratio of the isocyanate-terminated urethane prepolymer (A) containing polyester polyol to the isocyanate-terminated urethane prepolymer (B) containing polyether polyol in the isocyanate-terminated urethane prepolymer is 30:70 to 70:30, and the polyester polyol contains a structural unit derived from a low-molecular-weight polyol having a branched chain, can suppress the rebound phenomenon of the polished object and has excellent flatness of the edge of the polished object after polishing.Furthermore, it was found that such a polishing pad has a small average diameter of the hollow part, obtains a fine foam structure, and can suppress the occurrence of scratches during polishing.

Claims

1. A polishing pad having a polishing layer containing a polyurethane resin, 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 urethane prepolymer comprises an isocyanate-terminated urethane prepolymer (A) and an isocyanate-terminated urethane prepolymer (B); the isocyanate-terminated urethane prepolymer (A) is a reaction product of a polyol component containing a polyester polyol and a polyisocyanate component, the polyester polyol containing a structural unit derived from a low-molecular-weight polyol having a branched chain; the isocyanate-terminated urethane prepolymer (B) is a reaction product of a polyol component including a polyether polyol and a polyisocyanate component, The polishing pad, wherein the weight ratio ((A):(B)) of the isocyanate-terminated urethane prepolymer (A) to the isocyanate-terminated urethane prepolymer (B) is 30:70 to 70:

30.

2. 10. The polishing pad of claim 1, wherein the branched low molecular weight polyol comprises neopentyl glycol.

3. 3. The polishing pad according to claim 1, wherein the polyester polyol in the isocyanate-terminated urethane prepolymer (A) has a number average molecular weight of less than 1,000.

4. 4. The polishing pad according to claim 1, wherein the curable resin composition further comprises hollow microspheres.

5. 5. The polishing pad according to claim 1, wherein the average bubble diameter of the polishing layer is 5 μm or more and less than 20 μm.

6. 6. The polishing pad according to claim 1, wherein the polishing layer does not have a phase-separated structure.

7. The polishing pad of any one of claims 1 to 6, wherein the curing agent comprises 3,3'-dichloro-4,4'-diaminodiphenylmethane.

8. 8. The polishing pad according to claim 1, wherein the polyisocyanate component in the isocyanate-terminated urethane prepolymer (A) comprises tolylene diisocyanate.

9. 9. The polishing pad according to claim 1, wherein the polyisocyanate component in the isocyanate-terminated urethane prepolymer (B) comprises tolylene diisocyanate.

10. 10. A method for producing a polishing pad according to claim 1, comprising the step of shaping the polishing layer.

11. A method for polishing a surface of an optical or semiconductor material, the method comprising the step of polishing the surface of the optical or semiconductor material using the polishing pad according to any one of claims 1 to 9.

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