Polishing pad

Abstract

To provide a polishing pad that has excellent defect performance, as well as, excellent topo performance.SOLUTION: A polishing pad comprises a polishing layer made of a polyurethane resin foam made from an isocyanate-terminated prepolymer and a curing agent. Therein: a value obtained by subtracting a ratio of a crystalline phase content to the amorphous phase content (amorphous phase / crystalline phase) in the polishing layer measured at 40°C by a pulsed NMR method in a dry state from the ratio of the crystalline phase content to the amorphous phase content (amorphous phase / crystalline phase) in the polishing layer measured at 40°C by the pulsed NMR method in the wet state is 0.50% or more and 0.85% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing pad. The polishing pad of the present invention is used for polishing optical materials, semiconductor devices, glass substrates for hard disks, etc., and is particularly suitable for polishing devices having an oxide layer, metal layer, etc. formed on a semiconductor wafer. [Background technology]

[0002] Chemical mechanical polishing (CMP) is a commonly used polishing method for planarizing the surfaces of optical materials, semiconductor wafers, semiconductor devices, and hard disk substrates. The CMP method will be described with reference to FIG. 1. As shown in FIG. 1, a polishing apparatus 1 for performing the CMP method is equipped with a polishing pad 3. The polishing pad 3 contacts the workpiece 8 held by a holding platen 16 and a retainer ring (not shown in FIG. 1) that prevents the workpiece 8 from shifting. The polishing pad 3 includes a polishing layer 4, which is the layer that performs the polishing, and a cushion layer 6 that supports the polishing layer 4. The polishing pad 3 is rotated while pressed against the workpiece 8, polishing the workpiece 8. During this process, a slurry 9 is supplied between the polishing pad 3 and the workpiece 8. The slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard, fine abrasive grains. As the chemical components and abrasive grains flow, the relative movement with the workpiece 8 increases the polishing effect. The slurry 9 is supplied to and discharged from the polishing surface via grooves or holes.

[0003] The polishing layer material used in polishing semiconductor devices is a hard polyurethane material obtained by reacting a prepolymer containing an isocyanate component (e.g., toluene diisocyanate (TDI)) and a high molecular weight polyol (e.g., polyoxytetramethylene glycol (PTMG)) with a diamine curing agent (e.g., 4,4'-methylenebis(2-chloroaniline) (MOCA)). This hard polyurethane material is composed of a soft segment formed by the high molecular weight polyol and a hard segment formed by urethane bonds or urea bonds. In recent years, with the miniaturization of wiring in semiconductor devices, conventional polishing layers or polishing pads have sometimes proven insufficient in terms of topography and removal rate, and further investigation is being conducted.

[0004] Patent document 1 discloses a polishing pad that uses a polishing layer that contains a specified proportion of a crystalline phase (S phase) measured by pulse NMR, thereby reducing changes in hardness due to heat, resulting in sufficient polishing and less scratching, allowing for stable polishing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Restatement 2016 / 158348 publication Summary of the Invention [Problem to be solved by the invention]

[0006] However, the polishing pad described in Patent Document 1 has the problem that its topo performance and polishing rate are insufficient. The present invention has been made in view of the above problems, and has an object to provide a polishing pad that is excellent in topo performance and polishing rate. [Means for solving the problem]

[0007] The present inventors have discovered that a polishing layer capable of controlling the change in the ratio of the content of the crystalline phase, mesophase, and amorphous phase in the polishing layer when changing from a dry state to a wet state has excellent topo performance and polishing rate, and have achieved the present invention. [1] A polishing pad having a polishing layer made of a polyurethane resin foam made from an isocyanate-terminated prepolymer and a curing agent, the ratio of the content rate of the crystalline phase to the content rate of the amorphous phase in the polishing layer measured at 40°C by pulse NMR in a wet state (amorphous phase / crystalline phase) minus the ratio of the content rate of the crystalline phase to the content rate of the amorphous phase in the polishing layer measured at 40°C by pulse NMR in a dry state (amorphous phase / crystalline phase) is 0.50 or more and 0.85 or less; Polishing pad. [2] The polishing pad described in [1], wherein the ratio of the mesophase content to the amorphous phase content in the polishing layer (amorphous phase / mesophase) measured at 40°C by pulse NMR in the wet state is 5.0 or more and 13.0 or less, and the ratio of the mesophase content to the amorphous phase content in the polishing layer (amorphous phase / mesophase) measured at 40°C by pulse NMR in the dry state is 5.0 or more and 13.0 or less. [3] The polishing pad described in [1], wherein the ratio of the crystalline phase content to the amorphous phase content in the polishing layer (amorphous phase / crystalline phase) measured at 40°C by pulse NMR in a wet state and a dry state is 1.00 or more and 5.00 or less. [4] The polishing pad described in [1], wherein the content of amorphous phase in the polishing layer measured at 40°C by pulse NMR in a wet state and a dry state is 60.0% or more and 80.0% or less. [5] The polishing pad according to [1], wherein the content of mesophase in the polishing layer measured at 40°C by pulse NMR in a wet and dry state is 15.0% or less. [6] The polishing pad according to [1], wherein the isocyanate-terminated prepolymer contains a structural unit derived from a polyisocyanate compound and a structural unit derived from a high-molecular-weight polyol, and the structural unit derived from a high-molecular-weight polyol contains at least a structural unit derived from a polyether polycarbonate diol (PEPCD) and a structural unit derived from a PPG. [7] The polishing pad according to [6], wherein the polyether polycarbonate diol (PEPCD)-derived constitutional units account for 30% by weight or more and 80% by weight or less of the high-molecular-weight polyol-derived constitutional units. [8] The polishing pad according to [6], wherein the polyurethane resin foam is made from at least two types of isocyanate-terminated prepolymers, at least one of the at least two types of isocyanate-terminated prepolymers contains the polyether polycarbonate diol (PEPCD)-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the polyether polycarbonate diol (PEPCD)-derived structural unit is 580 or more and 700 or less. [9] The polishing pad according to [6], wherein the polyurethane resin foam is made from at least two types of isocyanate-terminated prepolymers, at least one of the at least two types of isocyanate-terminated prepolymers contains the PPG-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the PPG-derived structural unit is 580 or more and 700 or less. [Effects of the Invention]

[0008] When the polishing layer changes from a dry state to a wet state, the change in the ratio of the content of the crystalline phase, intermediate phase, and amorphous phase in the polishing layer can be controlled, and the proportion of the amorphous phase, which has high mobility, becomes higher than that of the crystalline phase and the intermediate phase, and it is thought that the polishing layer moderately softens during polishing. A polishing pad having such a polishing layer is a polishing pad with excellent topo performance and removal rate for polished objects containing wiring. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the state of polishing. [Figure 2] FIG. 2 is a cross-sectional view of a polishing pad. [Figure 3] FIG. 3 is a schematic diagram showing a polished state of an object to be polished in which wiring is present. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments of the invention will be described, but the present invention is not limited to the embodiments of the invention.

[0011] <<Polishing pads>> The structure of the polishing pad 3 will be described with reference to Fig. 2. As shown in Fig. 2, the polishing pad 3 includes a polishing layer 4 and a cushion layer 6. The shape of the polishing pad 3 is preferably disk-shaped, but is not particularly limited thereto, and the size (diameter) can also be determined appropriately depending on the size of the polishing apparatus 1 equipped with the polishing pad 3, and can be, for example, about 10 cm to 2 m in diameter. In the polishing pad 3 of the present invention, the polishing layer 4 is preferably bonded to the cushion layer 6 via an adhesive layer 7, as shown in FIG. The polishing pad 3 is attached to the polishing platen 10 of the polishing apparatus 1 by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing apparatus 1 while pressing against the object 8 to be polished, and polishes the object 8 to be polished.

[0012] <Polishing layer> (composition) The polishing pad 3 includes a polishing layer 4 that is a layer for polishing an object to be polished 8. The material that constitutes the polishing layer 4 is a polyurethane resin foam. The material, manufacturing method, etc. of the polyurethane resin foam will be described later. The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3, and can be about 10 cm to 2 mm in diameter, and the thickness of the polishing layer 4 can be about 0.8 mm to 5 mm. The polishing layer 4 is rotated together with the polishing table 10 of the polishing device 1, and while a slurry 9 is poured onto it, the chemical components and abrasive grains contained in the slurry 9 are moved relative to the object 8 to be polished, thereby polishing the object 8 to be polished. The polishing layer 4 may have hollow microspheres 4A (foamed) dispersed therein. When hollow microspheres 4A are dispersed, as the polishing layer 4 is worn, the hollow microspheres 4A are exposed to the polishing surface, creating minute voids on the polishing surface. This is preferable because these minute voids retain the slurry, allowing polishing of the workpiece 8 to proceed more efficiently. The polishing layer 4 is also dry-molded. Figure 2 shows an example in which hollow microspheres 4A (foamed) are contained.

[0013] (grooving) It is preferable to provide grooves, if necessary, on the surface of the polishing layer 4 of the present invention facing the polished object 8. The grooves are not particularly limited and may be either slurry discharge grooves that communicate with the periphery of the polishing layer 4 or slurry retention grooves that do not communicate with the periphery of the polishing layer 4, or both slurry discharge grooves and slurry retention grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, while examples of the slurry retention grooves include concentric grooves and perforations (through holes), and these can also be combined.

[0014] (Shore D hardness) The Shore D hardness of the polishing layer 4 of the present invention is not particularly limited, but is, for example, 20 to 100, preferably 30 to 80, and more preferably 40 to 70. If the Shore D hardness is low, the topo performance tends to deteriorate during low-pressure polishing. If the Shore D hardness is too high, the polishing layer 4 may be rubbed strongly against the workpiece 8, causing scratches on the polished surface of the workpiece 8.

[0015] (density) The density of the polishing layer 4 of the present invention is not particularly limited, but is, for example, 0.60 g / cm 3 More than 1.25g / cm 3 or less, preferably 0.65 g / cm 3More than 1.15g / cm 3 When the density of the polishing layer 4 is within the above range, the hardness of the polishing layer 4 can be maintained, and good topo performance and polishing rate tend to be obtained.

[0016] In the polishing pad 3 of the present invention, when hollow microspheres 4A are used, air bubbles can be encapsulated within the polyurethane resin molding. Hollow microspheres refer to microspheres having voids. The shapes of the hollow microspheres 4A include spherical, elliptical, and shapes similar thereto. Examples include pre-expanded microspheres and those obtained by thermally expanding unexpanded thermally expandable microspheres.

[0017] (About Topo performance and polishing rate) The polishing pad of the present invention is characterized by having excellent topo performance and polishing rate due to the presence of a specific polishing layer. First, the topo performance will be described. As shown in FIG. 3, the object to be polished 8 is composed of a base 81 and a metal film 82 formed on the base. Before polishing, as shown in Figure 3(a), the formed metal film 82 may have steps (unevenness of the metal film 82 at a position higher than the surface 813 of the base) in locations such as the wide wiring portion 811 and the narrow wiring portion 812. However, when polishing such an object to be polished 8, as shown in Figure 3(b), the surface of the metal film 82 of the object to be polished 8 is polished overall, regardless of the locations of the wide wiring portion 811 and the narrow wiring portion 812. If polishing is then performed with a polishing pad having poor topo performance, dishing 821 is observed in the wide wiring portion 811, and erosion 822 is observed in the narrow wiring portion 812, as shown in Figure 3(c). Dishing 821 is a phenomenon in which the metal film is recessed only in the line width portion, and erosion 822 is a phenomenon in which the metal film is recessed over the entire narrow wiring portion 812. The polishing pad 3 of the present invention is a polishing pad with high topo performance in terms of being able to suppress dishing 821, particularly dishing 821, out of dishing 821 and erosion 822.

[0018] Next, the polishing rate will be explained. The polishing rate refers to the amount of polishing per unit time.

[0019] (crystalline phase, mesophase, amorphous phase) In the polishing layer of the polishing pad of the present invention, the ratio of the crystalline phase content to the amorphous phase content in the polishing layer measured in a wet state by pulsed NMR at 40°C (amorphous phase / crystalline phase) minus the ratio of the crystalline phase content to the amorphous phase content in the polishing layer measured in a dry state by pulsed NMR at 40°C (amorphous phase / crystalline phase) is 0.50 or more and 0.85 or less, preferably 0.52 or more and 0.84 or less, more preferably 0.53 or more and 0.83 or less. A polishing pad having such a polishing layer has excellent topo performance and polishing rate because the content ratio of the crystalline phase to the amorphous phase in the polishing layer changes greatly when the state changes from a dry state to a wet state, and the proportion of the amorphous phase, which has high mobility, increases moderately, and the polishing layer moderately softens during polishing.

[0020] The proportions of the crystalline, mesophase, and amorphous phases in the polishing layer are determined using pulsed NMR. In pulsed NMR measurements, the free induction decay (FID) signal can be separated into three components by subtracting the component with the longest spin-spin relaxation time using the least-squares method. Specifically, the initial value of the FID signal is proportional to the number of protons in the sample. If the sample contains three components, the FID signal appears as the sum of the response signals of the three components. However, because the components in the sample have different mobilities, the decay rates of the response signals differ between the components, resulting in different spin-spin relaxation times. Therefore, the least-squares method can separate the three components. Polyurethane resin foams are classified into short phases (S phases), middle phases (M phases), and long phases (L phases) in order of shortest spin-spin relaxation time, and the proportions of each phase are determined. Regarding the proportions of the S phase, M phase, and L phase, for example, the crystalline phase is mainly observed as the S phase in pulsed NMR measurement, the amorphous phase is mainly observed as the L phase, and the mesophase is mainly observed as the M phase in pulsed NMR measurement. Furthermore, the hard segment portion is mainly observed as the S phase in pulsed NMR measurement, and the soft segment portion is mainly observed as the L phase. The spin-spin relaxation time can be determined, for example, by carrying out measurements using a JEOL "JNM-MU25" by the Solid Echo method. NMR (nuclear magnetic resonance) generally uses a superconducting magnet to measure chemical shifts in a strong magnetic field, and is widely known as a device for structural analysis of organic compounds. It measures the ratio of crystalline phases (hard segments), amorphous phases (soft segments), and intermediate phases (interface phases), and evaluates molecular mobility from relaxation time. When a magnetic field is applied to a sample as a pulse, the nuclear spins of the protons in the sample enter an excited state with aligned directions. The process by which this returns to the original random ground state is called relaxation, and the time required for this process is called relaxation time.

[0021] During polishing, the temperature of the polishing pad reaches 40°C. If the polishing pad becomes too hard due to an increase in the proportion of hard segments during polishing, scratches may occur more easily and defect performance may deteriorate. On the other hand, an increase in the proportion of soft segments makes the polishing pad softer, which is undesirable because it deteriorates the topo performance and removal rate. Here, the crystalline phase is a component with low mobility and corresponds to the hard segment component, while the amorphous phase is a component with high mobility and corresponds to the soft segment component. The proportions of the hard segment component and the soft segment component affect the physical properties of the polishing pad, such as hardness. Pulse NMR measurements have traditionally been performed in a dry state. However, as mentioned above, actual polishing is performed while supplying a slurry, which is a mixture of water, various chemical components, and hard, fine abrasive grains. Actual experimental results will be described in the examples, but the results of pulse NMR measurements performed in a dry state differ from those of pulse NMR measurements performed in a wet state.

[0022] In this specification, measurement by pulse NMR in a wet state means immersing the polishing layer material in pure water for 24 hours, wiping off the pure water on the surface of the polishing layer with Kimtowel (registered trademark), and then performing pulse NMR measurement at a specified temperature (40°C in this invention).

[0023] In the polishing layer of the polishing pad of the present invention, the ratio of the mesophase content to the amorphous phase content in the polishing layer measured at 40 ° C. by pulse NMR in a wet state (amorphous phase / mesophase) is preferably 5.0 or more and 13.0 or less, more preferably 5.2 or more and 12.8 or less. In addition, the ratio of the mesophase content to the amorphous phase content in the polishing layer measured at 40 ° C. by pulse NMR in a dry state (amorphous phase / mesophase) is preferably 5.0 or more and 13.0 or less, more preferably 5.2 or more and 12.8 or less. When changing from a dry state to a wet state, the content ratio of the amorphous phase from the mesophase in the polishing layer changes significantly, the proportion of the amorphous phase with high mobility increases moderately, and the polishing layer moderately softens during polishing, resulting in excellent topo performance and polishing rate.

[0024] In the polishing layer of the polishing pad of the present invention, the ratio of the content of the crystalline phase to the content of the amorphous phase in the polishing layer measured at 40°C by pulse NMR in a wet state and a dry state (amorphous phase / crystalline phase) is preferably 1.0 or more and 5.0 or less, more preferably 1.5 or more and 4.5 or less. By satisfying the above range, when the dry state changes to a wet state, the proportion of the amorphous phase with high mobility is appropriately present, and the polishing layer is appropriately softened during polishing, and rubber elasticity is imparted, which tends to result in excellent topo performance and polishing rate.

[0025] The content of amorphous phase in the polishing layer of the polishing pad of the present invention, measured at 40 ° C. by pulse NMR in wet and dry states, is not particularly limited, but is preferably 60.0% or more and 80.0% or less, more preferably 63.0% or more and 77.0% or less. By satisfying the above range, the proportion of amorphous phase with high mobility is moderately present, and the polishing layer is moderately softened during polishing, and rubber elasticity is imparted, which tends to result in excellent topo performance and polishing rate.

[0026] The content of the mesophase in the polishing layer of the polishing pad of the present invention, measured at 40°C by pulse NMR in a wet state and a dry state, is not particularly limited, but is preferably 15.0% or less, more preferably 12.0% or less. By satisfying this range, a structure in which the crystalline phase and the amorphous phase are clearly phase-separated during polishing in a wet state is obtained, and the pad has elastic properties that are less likely to cause distortion, which tends to result in excellent topo performance and polishing rate.

[0027] The polishing layer of the polishing pad of the present invention has a crystalline phase content of 10.0% or more and 30.0% or less, preferably 12.0% or more and 28.0% or less, measured at 40°C by pulse NMR in both wet and dry states. By satisfying this range, the proportion of crystalline phase with low mobility is adequate, the polishing layer maintains an adequate hardness during polishing, and the topo performance and polishing rate tend to be excellent.

[0028] <Cushion layer> (composition) The polishing pad 3 of the present invention has a cushion layer 6. The cushion layer 6 desirably allows the polishing layer 4 to contact the workpiece 8 more uniformly. Materials for the cushion layer 6 include resins; impregnated materials in which the resins are impregnated into a base material; flexible materials such as synthetic resins and rubbers; and sponge materials using the resins. Examples of the resins include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber.

[0029] The cushion layer 6 may be a foam having a cellular structure. As the cellular structure, in addition to a nonwoven fabric or the like having voids formed therein, a suede-like material having teardrop-shaped bubbles formed by a wet film-forming method, or a sponge-like material having fine bubbles formed therein may be preferably used. Among these, if a cushion layer is made of a nonwoven fabric impregnated with polyurethane or a sponge-like material, it will be compatible with the polishing layer, and will be able to achieve a high polishing rate while maintaining defect performance.

[0030] <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 a double-sided tape or an adhesive. Any double-sided tape or adhesive known in the art (e.g., an adhesive sheet) can be used. The polishing layer 4 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be formed of at least one adhesive selected from, for example, acrylic, epoxy, and urethane adhesives. For example, an acrylic adhesive is used, and the thickness can be set to 0.1 mm.

[0031] The polishing rate refers to the amount of polishing per unit time.

[0032] <<Polishing pad manufacturing method>> A method for producing the polishing pad 3 of the present invention will be described.

[0033] <Abrasive layer material> A polyurethane resin foam is used as the material for the polishing layer 4. Specific examples of the main component include a material obtained by reacting an isocyanate-terminated prepolymer with a curing agent. To foam the material, a foaming agent is added to the material.

[0034] The method for producing the polishing layer 4 will be described below using an example in which an isocyanate-terminated prepolymer and a curing agent are used.

[0035] Examples of methods for producing the polishing layer 4 using an isocyanate-terminated prepolymer and a curing agent include a material preparation step of preparing at least an isocyanate-terminated prepolymer, an additive, and a curing agent; a mixing step of mixing at least the isocyanate-terminated prepolymer, the additive, and the curing agent to obtain a mixture for molding a molded body; a molding step of molding the polishing layer 4 from the mixture for molding a molded body; and a bonding step of bonding the polishing layer and the cushion layer together.

[0036] The material preparation process, the mixing process, the molding process, and the joining process will be explained below.

[0037] <Material preparation process> To manufacture the polishing layer 4 of the present invention, an isocyanate-terminated prepolymer and a curing agent are prepared as raw materials for the polyurethane resin foam. Here, the isocyanate-terminated prepolymer is a urethane prepolymer for forming the polyurethane resin foam.

[0038] Each component will be described below.

[0039] (Isocyanate-terminated prepolymer) The isocyanate-terminated prepolymer can contain structural units derived from a polyisocyanate compound and structural units derived from a high-molecular-weight polyol, and the structural units derived from a high-molecular-weight polyol can contain at least structural units derived from a polyether polycarbonate diol (PEPCD) and structural units derived from a PPG. The isocyanate-terminated prepolymer is a compound obtained by reacting the following polyisocyanate compound with a polyol under commonly used conditions, and contains a urethane bond and an isocyanate group in the molecule. Furthermore, other components may be contained in the isocyanate-terminated prepolymer within the range that does not impair the effects of the present invention.

[0040] The isocyanate-terminated prepolymer may be a commercially available product, or may be one synthesized by reacting a polyisocyanate compound with a polyol. There are no particular limitations on the reaction, and the addition polymerization reaction may be carried out using a method and conditions known in the production of polyurethane resins. For example, the prepolymer may be produced by adding a polyisocyanate compound heated to 50°C to a polyol heated to 40°C while stirring in a nitrogen atmosphere, then heating the mixture to 80°C after 30 minutes and continuing the reaction at 80°C for 60 minutes.

[0041] The polyurethane resin foam of the polishing pad of the present invention is made from at least two types of isocyanate-terminated prepolymers, at least one of which is an isocyanate-terminated prepolymer containing a polyether polycarbonate diol (PEPCD)-derived structural unit, and at least one of which can be an isocyanate-terminated prepolymer containing a PPG-derived structural unit. By using the above isocyanate-terminated prepolymer, it is possible to easily adjust the crystalline phase, mesophase, and amorphous phase to the desired content ratio during polishing in a wet state.

[0042] (NCO equivalent weight of isocyanate-terminated prepolymer) The NCO equivalent of the isocyanate-terminated prepolymer containing a polyether polycarbonate diol (PEPCD) structural unit is preferably 580 or more and 700 or less, more preferably 590 or more and 680 or less, and the NCO equivalent of the isocyanate-terminated prepolymer forming the PPG structural unit is preferably 580 or more and 700 or less, more preferably 590 or more and 680 or less. In addition, when two or more isocyanate-terminated prepolymers are used, the NCO equivalent of the isocyanate-terminated prepolymer after mixing is preferably 580 or more and 700 or less, more preferably 580 or more and 680 or less. By using the above-mentioned NCO equivalent of the isocyanate-terminated prepolymer, it is easy to adjust the content ratio of the crystalline phase, mesophase and amorphous phase to the desired ratio during polishing in a wet state. Therefore, when the isocyanate-terminated prepolymer is commercially available, it is preferable that the NCO equivalent weight falls within the above range. When producing it by synthesis, it is preferable to adjust the NCO equivalent weight within the above range by using the raw materials described below in appropriate proportions.

[0043] (Polyisocyanate compounds) In this specification, the term "polyisocyanate compound" refers to 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'-dimethyl- Examples of the polyisocyanate compound include diphenylmethane-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, ethylidine diisothiocyanate, etc. These polyisocyanate compounds may be used alone, or multiple polyisocyanate compounds may be used in combination.

[0044] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI.

[0045] (Polyol as a raw material for prepolymer) In this specification, a high molecular weight polyol means a compound having two or more hydroxyl groups (OH) in the molecule, and "high molecular weight" means a molecular weight of 500 or more. Examples of polyol compounds used in the synthesis of urethane bond-containing polyisocyanate compounds as prepolymers include diol compounds and triol compounds such as ethylene glycol, diethylene glycol (DEG), and butylene glycol; and polyether polyol compounds such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG), polypropylene glycol (PPG), and polyether polycarbonate diol (PEPCD). PEPCD is a compound represented by the following general formula:

[0046] [ka]

[0047] In the above formula, m and n represent the number of repeating units and each independently represents a real number. PEPCD can be used alone or in combination of two or more. In the above formula, m and n represent the number of repeating units and each independently represents a real number. PEPCD can be used alone or in combination of two or more.

[0048] Among the above components, in order to satisfy the polishing layer having a value obtained by subtracting the ratio of the crystalline phase content to the amorphous phase content (amorphous phase / crystalline phase) in the polishing layer measured in a wet state at 40°C by pulse NMR from the ratio of the crystalline phase content to the amorphous phase content (amorphous phase / crystalline phase) in the polishing layer measured in a dry state at 40°C by pulse NMR, of 0.50 or more and 0.85 or less, it is preferable that the high molecular weight polyol-derived structural unit contains at least a polyether polycarbonate diol (PEPCD)-derived structural unit and a PPG-derived structural unit. In a preferred embodiment, other polyol components may be used in addition to polyether polycarbonate diol (PEPCD) and PPG. Furthermore, the polyether polycarbonate diol (PEPCD)-derived structural units are preferably 30% by weight or more and 80% by weight or less, more preferably 30% by weight or more and 70% by weight or less, relative to the high molecular weight polyol-derived structural units. When the ratio of the polyether polycarbonate diol (PEPCD)-derived structural units to the high molecular weight polyol-derived structural units is within the desired range, and the isocyanate-terminated prepolymer is used, it becomes easy to adjust the crystalline phase, mesophase, and amorphous phase to the desired content ratio during polishing in a wet state. As a result, the polishing layer during polishing in a wet state has the desired physical properties, and there is a tendency to achieve both excellent topo performance and excellent polishing rate. Furthermore, since isocyanate-terminated prepolymers having structural units derived from polyether polycarbonate diol (PEPCD) contain carbonate bonds, the polishing layer (polyurethane resin foam) tends to be harder than isocyanate-terminated prepolymers having structural units derived from high molecular weight polyols other than polyether polycarbonate diol (PEPCD) even if the NCO equivalent weight is about the same, and the topo performance and polishing rate tend to be superior.

[0049] The number average molecular weight (Mn) of the polyols such as PPG and PEPCD is not particularly limited, and is preferably 500 to 3000, more preferably 800 to 2500. The proportions of crystalline phase, mesophase, and amorphous phase can be adjusted by adjusting the number average molecular weight of the polyol. Here, the number average molecular weight can be measured by gel permeation chromatography (GPC). When measuring the number average molecular weight of a polyol compound from a polyurethane resin, each component can be decomposed by a conventional method such as amine decomposition, and then the molecular weight can be estimated by GPC.

[0050] (additives) As described above, additives such as an oxidizing agent can be added to the material of the polishing layer 4 as needed.

[0051] (hardening agent) In the method for producing the polishing layer 4 of the present invention, a curing agent (also called a chain extender) is mixed with the isocyanate-terminated prepolymer in the mixing step. By adding the curing agent, the main chain end of the isocyanate-terminated prepolymer bonds with the curing agent to form a polymer chain in the subsequent molding step, which then hardens. Examples of the curing agent include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, 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-hydroxyphenyl)propane, 2,2-bis[3-(isopropylamino)-4- polyamine compounds such as 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, trimethylethylenebis-4-aminobenzoate, and polytetramethyleneoxide-di-p-aminobenzoate; ethylene glycol, propane, Pyrene 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- Examples of polyhydric alcohol compounds include 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, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol.Furthermore, the polyvalent amine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, etc. As the polyvalent amine compound, a diamine compound is preferred, and it is more preferred to use, for example, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

[0052] When two or more types of high molecular weight polyols are used as raw materials for the isocyanate-terminated prepolymer, the two or more types of high molecular weight polyols may be mixed and then reacted with a polyisocyanate compound, or two or more types of high molecular weight polyols may be reacted with a polyisocyanate compound, and then the mixture may be mixed and cured.

[0053] The polishing layer 4 can be formed from hollow microspheres 4A, which have an outer shell and a hollow interior. The hollow microspheres 4A may be commercially available or synthesized by conventional methods. The material for the outer shell of the hollow microspheres 4A is not particularly limited, but examples include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride and organic silicone resins, and copolymers of two or more of the monomers constituting these resins (e.g., acrylonitrile-vinylidene chloride copolymer). Commercially available hollow microspheres include, but are not limited to, the Expancel series (trade name, manufactured by Nippon Phillite Co., Ltd.) and Matsumoto Microsphere (trade name, manufactured by Matsumoto Yushi Co., Ltd.). The gas contained in the hollow microspheres 4A is not particularly limited, but examples thereof include hydrocarbons, such as isobutane, pentane, and isopentane.

[0054] The shape of the hollow microspheres 4A is not particularly limited and may be, for example, spherical or nearly spherical. The average particle size of the hollow microspheres 4A is not particularly limited but is preferably 5 μm to 200 μm, more preferably 5 μm to 80 μm, even more preferably 5 μm to 50 μm, and particularly preferably 5 μm to 35 μm. The average particle size can be measured using a laser diffraction particle size analyzer (e.g., Mastersizer 2000, manufactured by Spectris Co., Ltd.).

[0055] The material for the hollow microspheres 4A is added in an amount of preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 4 parts by mass, per 100 parts by mass of the isocyanate-terminated prepolymer.

[0056] In addition to the above components, conventional blowing agents may be used in combination with the hollow microspheres 4A within the range that does not impair the effects of the present invention, and a gas that is non-reactive with the above components may be blown into the hollow microspheres 4A during the mixing step described below. Examples of the blowing agent include water and blowing agents whose main component is a hydrocarbon having 5 or 6 carbon atoms. Examples of the hydrocarbon include linear hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

[0057] <Mixing process> In the mixing step, the isocyanate-terminated prepolymer obtained in the preparation step, the additives, and the curing agent are fed into a mixer and stirred and mixed. The mixing step is carried out in a state where the components are heated to a temperature that ensures the fluidity of each component.

[0058] <Forming process> In the molding process, the mixture for molding prepared in the mixing process is poured into a mold preheated to 30 to 100°C for primary curing, and then heated at about 100 to 150°C for about 10 minutes to 5 hours for secondary curing to form a cured polyurethane resin (polyurethane resin foam). At this time, the isocyanate-terminated prepolymer and the curing agent react to form a polyurethane resin, which cures the mixture. If the viscosity of the urethane prepolymer (isocyanate-terminated prepolymer) is too high, its fluidity will be poor, making it difficult to achieve uniform mixing. Increasing the temperature to lower the viscosity shortens the pot life, resulting in uneven mixing and uneven size of the hollow microspheres 4A formed in the resulting foam. Conversely, if the viscosity is too low, air bubbles will move within the mixture, making it difficult to form uniformly dispersed hollow microspheres 4A in the resulting foam. For this reason, it is preferable to set the viscosity of the isocyanate-terminated prepolymer at a temperature of 50 to 80°C in the range of 500 mPa·s to 10,000 mPa·s. This can be achieved, for example, by changing the molecular weight (degree of polymerization) of the isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer is heated to approximately 50 to 80°C to become flowable.

[0059] In the molding process, the mixture is reacted in a mold as needed to form a foam, during which the isocyanate-terminated prepolymer reacts with the curing agent to crosslink and harden.

[0060] After obtaining the polyurethane resin foam, it is sliced ​​into sheets to form multiple polishing layers 4. A common slicing machine can be used for slicing. During slicing, the lower layer of the polishing layer 4 is held, and the polishing layer 4 is sliced ​​to a predetermined thickness starting from the upper layer. The slice thickness is set, for example, in the range of 0.8 mm to 2.5 mm. For example, in the case of a polyurethane resin foam molded in a 50 mm thick mold, approximately 10 mm of the upper and lower layers of the polyurethane resin foam are not used due to scratches, and 10 to 25 polishing layers 4 are formed from approximately 30 mm of the center. In the curing and molding step, a polyurethane resin foam is obtained in which hollow microspheres 4A are uniformly formed inside.

[0061] The polishing surface of the resulting polishing layer 4 is grooved as needed. Grooves with any pitch, width, and depth can be formed by cutting the polishing surface with a required cutter. Examples of the slurry-retaining grooves include circular grooves formed in a concentric pattern, and examples of the slurry-discharging grooves include linear grooves formed in a lattice pattern or linear grooves formed radially from the center of the polishing layer.

[0062] After that, a double-sided tape is attached to the surface of the polishing layer 4 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.

[0063] <Method of manufacturing cushion layer 6> As described above, examples of the material for the cushion layer 6 include an impregnated material in which resin fibers (nonwoven fabric, flexible film, etc.) such as polyethylene or polyester are impregnated with a resin solution such as urethane; a suede material using a resin material such as urethane; and a sponge material using a material such as urethane. In the present invention, a known material can be used for the cushion layer 6, and a known manufacturing method can also be used.

[0064] <Joining process> In the bonding step, the formed polishing layer 4 and cushion layer 6 are bonded together (bonded) with an adhesive layer 7. For example, an acrylic adhesive is used for the adhesive layer 7, and the adhesive layer 7 is formed to a thickness of 0.1 mm. That is, the acrylic adhesive is applied to a substantially uniform thickness on the surface of the polishing layer 4 opposite the polishing surface. The surface of the polishing layer 4 opposite the polishing surface and the surface of the cushion layer 6 (the surface on which the skin layer is formed) are pressed together via the applied adhesive, and the polishing layer 4 and cushion layer 6 are bonded together with the adhesive layer 7. Then, after cutting into a desired shape such as a circle, an inspection is performed to check for the absence of dirt or foreign matter, etc., and the polishing pad 3 is completed. [Example]

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0066] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0067] The NCO equivalent is a numerical value showing the molecular weight of the prepolymer (PP) per NCO group, which is calculated by the formula "(mass (parts) of polyisocyanate compound + mass (parts) of polyol) / [(number of functional groups per molecule of polyisocyanate compound × mass (parts) of polyisocyanate compound / molecular weight of polyisocyanate compound) - (number of functional groups per molecule of polyol × mass (parts) of polyol / molecular weight of polyol)]".

[0068] (About the polishing layer) Urethane prepolymer 1 (PP1) and urethane prepolymer 2 (PP2) were prepared by reacting the specified 2,4-tolylene diisocyanate (2,4-TDI) as an isocyanate compound, PPG (polypropylene glycol) and DEG (diethylene glycol) as polyols, and PEPCD (polyether polycarbonate diol) and DEG, respectively (see Table 1 for the components used in preparing the urethane prepolymers). Unexpanded hollow microspheres with a shell composed of acrylonitrile-vinylidene chloride copolymer and containing isobutane gas were added to the urethane prepolymer mixture, which was mixed in the proportions shown in Table 2, to obtain a mixed solution. The urethane prepolymer mixture was placed in a first-liquid tank and kept at 60°C. Next, MOCA, a curing agent, was placed in a second-liquid tank, separately from the first liquid, and heated to 120°C for melting and keeping the temperature constant. The liquids from the first and second liquid tanks were injected into a mixer equipped with two injection ports so that the R value, which represents the equivalent ratio of amino groups and hydroxyl groups present in the curing agent to the terminal isocyanate groups in the prepolymer, was 0.9. The two injected liquids were mixed and stirred while being poured into a mold preheated to 80°C, then the mold was clamped and heated at 80°C for 30 minutes for primary curing. The primary cured molded product was demolded and then subjected to secondary curing 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, heated again in an oven at 120°C for 5 hours, and then sliced ​​to a thickness of 1.3 mm to obtain abrasive layers A to C shown in Tables 2 to 6. The density and Shore D hardness of each abrasive layer are shown in Table 2. The proportions of crystalline phase, mesophase, and amorphous phase in each abrasive layer measured at 40°C by pulse NMR in wet and dry states are shown in Table 3. From these data, predetermined values ​​are shown in Tables 4 and 5. In Table 5, "wet / dry" refers to the ratio of the crystalline phase, mesophase, and amorphous phase, respectively, and the lower column of Table 5 shows the relaxation times of the crystalline phase, mesophase, and amorphous phase, which are the values ​​in the wet state minus the values ​​in the dry state (differences) for crystalline phase / mesophase, amorphous phase / crystalline phase, and amorphous phase / mesophase, respectively. Table 6 shows the measurement methods and conditions for density, Shore D hardness, and pulse NMR measurements (dry and wet states).

[0069] (density) Density of the polishing layer (g / cm 3 ) was measured in accordance with the Japanese Industrial Standard (JIS K 6505).

[0070] (Shore D hardness) The Shore D hardness of the polishing layer (referred to as "D hardness" in Table 2) was measured using a Shore D hardness tester in accordance with the Japanese Industrial Standard (JIS-K-6253). Here, the measurement sample was obtained by stacking multiple polishing layers as necessary to achieve a total thickness of at least 4.5 mm.

[0071] (Pulse NMR measurement) The conditions for pulse NMR measurements carried out on the polishing layers A to E are as follows: The phases were divided into crystalline phase, mesophase, and amorphous phase according to the relaxation time, and the proportions of each were calculated. Equipment Bruker Minispec mq20 (20MHz) nuclide 1 H Measurement T2 Measurement method Solid echo method Acquisition Scale 0.4msec Scan 128 times Recycle Delay 0.5sec Measurement temperature 40℃ After the temperature of the apparatus reached the measurement temperature and the sample was set, the measurement was started after leaving it for 5 minutes. One measurement was taken immediately after the start of the measurement, and then one measurement every 5 minutes thereafter, for a total of six measurements. Of the six measurements, the second to sixth measurements were averaged to obtain the average value. The samples were prepared by punching out 8 mm diameter samples from the polishing layers A to E and storing them in a thermo-hygrostat chamber at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) for 40 hours. Also prepared were wet samples that were immersed in pure water for 24 hours, after which the surface moisture was wiped off with Kimtowel (registered trademark), and then immediately measured. The punched samples were filled into the sample tube to a height of 1 to 1.5 cm using the above apparatus and conditions.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] [Table 5]

[0077] [Table 6]

[0078] (About the cushion layer) Commercially available sponge-like urethane foam (Shore A hardness 60, density 0.55 g / cm 3 The Shore A hardness of the cushion layer was determined in accordance with the Japanese Industrial Standards (JIS-K-7311) from the depth of penetration of an indenter pressed against the surface of the test piece via a spring. The density of the cushion layer was determined by measuring it in the same way as the polishing layer.

[0079] Examples and Comparative Examples The polishing layer B and the cushion layer were bonded with a 0.1 mm thick double-sided tape (a PET substrate with an adhesive made of an acrylic resin on both sides) to obtain the polishing pad of Example 1. Polishing layers A, C, D, and E were used instead of polishing layer B and bonded in the same manner to obtain the polishing pads of Comparative Example 1, Comparative Example 2, Example 2, and Example 3.

[0080] (Polishing performance evaluation) Using the resulting polishing pads of Examples 1, 2, 3, Comparative Examples 1 and 2, polishing tests were carried out under the following polishing conditions to evaluate the polishing performance (topographical performance and polishing rate).

[0081] (polishing conditions) Polishing machine used: F-REX300X (manufactured by Ebara Corporation) Disk: 34J (Kinik) Polishing agent temperature: 20℃ Polishing platen rotation speed: 90 rpm Polishing head rotation speed: 81 rpm Grinding pressure: 1.7psi Polishing slurry (metal film): CSL-9044C (a mixture of CSL-9044C stock solution and purified water at a weight ratio of 1:9) (manufactured by Fujifilm Planar Solutions Co., Ltd.) Polishing slurry flow rate: 200 ml / min Polishing time: 60 seconds Polished object (metal film): Cu film substrate (disk-shaped, 300 mm diameter) Pad break: 32N 20 minutes Conditioning: Ex-situ 32N 4 scans

[0082] (Topo performance evaluation) The polishing pad was placed in the designated position on the polishing machine using double-sided tape with an acrylic adhesive, and polishing was performed under the above-mentioned polishing conditions. The topo performance was evaluated by measuring the amount of depressions created by polishing pattern wafers (workpieces) with wiring widths of 100 μm / 100 μm, 50 μm / 50 μm, and 10 μm / 10 μm using an atomic force microscope (product name "NX-wafer", manufactured by Park Systems) in NC-AFM (non-contact) measurement mode. In Table 7, the cases where the amount of recession was 100 angstroms or less for all wiring widths were marked with a circle, and the cases where the amount of recession exceeded 100 angstroms for any wiring width were marked with an x.

[0083] (polishing rate) In the examples and comparative examples, the removal rate of the 16th, 26th, and 51st substrates polished was evaluated in terms of the polished thickness. The thickness was measured using a four-probe sheet resistance measurement device (manufactured by KLA-Tencor Corporation, trade name "RS-200", measurement: DBS mode). The lowest removal rate and the evaluation results are shown in Table 7. The evaluation was made as "Good" when the removal rate of all substrates was 3500 angstroms or more, and as "Poor" otherwise.

[0084] [Table 7]

[0085] From the results in Table 7, it was found that the polishing pads of Examples 1 to 3 have good topo performance because the value obtained by subtracting the ratio of the crystalline phase content to the amorphous phase content in the polishing layer (amorphous phase / crystalline phase) measured at 40°C by pulse NMR in a wet state from the ratio of the crystalline phase content to the amorphous phase content in the polishing layer (amorphous phase / crystalline phase) measured at 40°C by pulse NMR in a dry state is within an appropriate range. Furthermore, the results in Table 7 show that the polishing pads of Examples 1 to 3 have superior polishing rates compared to Comparative Example 1. [Industrial Applicability]

[0086] The present invention contributes to the manufacture and sale of polishing pads and has industrial applicability.

[0087] 1 Polishing equipment 3 polishing pads 4 Polishing layer 4A Hollow microsphere 6 Cushion layer 7 Adhesive layer 810 Polishing Plate

Claims

1. A polishing pad having a polishing layer made of a polyurethane resin foam made from an isocyanate-terminated prepolymer and a curing agent, A polishing pad in which the ratio of the crystalline phase content to the amorphous phase content in the polishing layer (amorphous phase / crystalline phase), measured at 40°C by pulse NMR in a wet state, minus the ratio of the crystalline phase content to the amorphous phase content in the polishing layer (amorphous phase / crystalline phase), measured at 40°C by pulse NMR in a dry state, is 0.50 or more and 0.85 or less.

2. The polishing pad of claim 1, wherein the ratio of the mesophase content to the amorphous phase content in the polishing layer (amorphous phase / mesophase) measured at 40°C by pulse NMR in the wet state is 5.0 or more and 13.0 or less, and the ratio of the mesophase content to the amorphous phase content in the polishing layer (amorphous phase / mesophase) measured at 40°C by pulse NMR in the dry state is 5.0 or more and 13.0 or less.

3. 2. The polishing pad of claim 1, wherein the ratio of the crystalline phase content to the amorphous phase content in the polishing layer (amorphous phase / crystalline phase) measured at 40°C by pulse NMR in a wet state and a dry state is 1.0 or more and 5.0 or less.

4. 2. The polishing pad according to claim 1, wherein the content of the amorphous phase in the polishing layer is 60.0% or more and 80.0% or less as measured at 40°C by pulse NMR in a wet state and a dry state.

5. 2. The polishing pad according to claim 1, wherein the content of mesophase in the polishing layer is 15.0% or less as measured at 40°C by pulse NMR in a wet state and a dry state.

6. The isocyanate-terminated prepolymer comprises a structural unit derived from a polyisocyanate compound and a structural unit derived from a high molecular weight polyol, and the structural unit derived from a high molecular weight polyol comprises at least a structural unit derived from a polyether polycarbonate diol (PEPCD) and a structural unit derived from a PPG. The polishing pad of claim 1.

7. 7. The polishing pad according to claim 6, wherein the polyether polycarbonate diol (PEPCD)-derived constitutional units account for 30% or more and 80% or less of the high-molecular-weight polyol-derived constitutional units.

8. The polyurethane resin foam is made from at least two types of isocyanate-terminated prepolymers, at least one of the at least two types of isocyanate-terminated prepolymers contains the polyether polycarbonate diol (PEPCD)-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the polyether polycarbonate diol (PEPCD)-derived structural unit is 580 or more and 700 or less. The polishing pad according to claim 6.

9. The polyurethane resin foam is made from at least two types of isocyanate-terminated prepolymers, at least one of the at least two types of isocyanate-terminated prepolymers contains the PPG-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the PPG-derived structural unit is 580 or more and 700 or less. The polishing pad of claim 6.

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