Polishing pad

Abstract

To provide a polishing pad that is excellent in step-eliminating performance and planarizing 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 ratio of a crystalline phase content to an amorphous phase content in the polishing layer measured at 40°C by a pulsed NMR method in a wet state is 0.5 or more and 1.0 or less; and a ratio of a mesophase content to an amorphous phase content in the polishing layer measured at 40°C by the pulsed NMR method in the wet state is 0.4 or more and 0.9 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] Polishing pads for semiconductor device polishing typically use a polishing layer made of 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-based curing agent (e.g., 4,4'-methylenebis(2-chloroaniline) (MOCA)). The high-molecular-weight polyol contained in the prepolymer forms a urethane soft segment, and PTMG, which exhibits ease of handling and moderate rubber elasticity, has traditionally been used as the high-molecular-weight polyol. However, with the recent trend toward finer wiring in semiconductor devices, conventional polishing pads have proven insufficient in terms of step resolution and planarization performance when polishing workpieces with a mixture of steps of different heights. Therefore, the use of high-molecular-weight polyols other than PTMG has been explored. Patent Document 1 discloses a polishing pad in which the defect rate is reduced by using a mixture of PPG and PTMG as a high molecular weight polyol of a prepolymer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-040737 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the polishing pad described in Patent Document 1 uses a mixture of PPG and PTMG, and therefore does not have sufficient step-eliminating and planarizing capabilities. The present invention has been made in view of the above problems, and has as its object to provide a polishing pad that is excellent in step-eliminating performance and planarizing performance. [Means for solving the problem]

[0006] The inventors discovered a polishing pad having a polishing layer that has excellent step elimination and planarization performance when polishing a workpiece containing a mixture of steps of different heights by adjusting the ratio of the crystalline phase content to the amorphous phase content, and the ratio of the intermediate phase content to the amorphous phase content, of the polishing layer, as measured by pulse NMR in a wet state, and arrived at the present invention. That is, the present invention includes the following. [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 crystalline phase content (%) to the amorphous phase content (%) in the polishing layer measured at 40°C by pulse NMR in a wet state is 0.5 or more and 1.0 or less; A polishing pad characterized in that the ratio of the mesophase content (%) to the amorphous phase content (%) in the polishing layer measured at 40°C by pulse NMR in the wet state is 0.4 or more and 0.9 or less. [2] The polishing pad according to [1], wherein the content of amorphous phase in the polishing layer measured at 40°C by pulse NMR in the wet state is 30.0% or more and 55.0% or less. [3] The polishing pad according to [1], wherein the content of mesophase in the polishing layer measured at 40°C by pulse NMR in the wet state is 15.0% or more and 35.0% or less. [4] The polishing pad according to [1], wherein the isocyanate-terminated prepolymer contains a polyisocyanate compound-derived structural unit and a high-molecular-weight polyol-derived structural unit, and the high-molecular-weight polyol-derived structural unit contains at least a polyester diol-derived structural unit and a PTMG-derived structural unit. [5] The polishing pad according to [4], wherein the number average molecular weight of the polyester diol used to form the polyester diol structurally derived units is 600 or more and 2500 or less. [6] The polishing pad according to [4], wherein the PTMG-derived structural units account for 30% by weight or more and 80% by weight or less of the high-molecular-weight polyol-derived structural units. [7] The polishing pad according to [4], 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 PTMG-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the PTMG-derived structural unit is 400 or more and 500 or less. [8] The polishing pad described in [4], 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 polyester diol-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the polyester diol structural unit is 550 or more and 700 or less. [Effects of the Invention]

[0007] The ratio of the crystalline phase content to the amorphous phase content in the polishing layer, as measured by pulse NMR in a wet state, is adjusted to a specific range, so that the proportion of the highly mobile amorphous phase is higher than that of the crystalline phase or intermediate phase, and the polishing layer softens moderately during polishing, resulting in a polishing pad with excellent step elimination and planarization performance even on polished objects containing a mixture of steps of different heights. [Brief explanation of the drawings]

[0008] [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 for explaining the step elimination performance and the planarization performance. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the embodiments of the invention will be described, but the present invention is not limited to the embodiments of the invention.

[0010] <<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.

[0011] <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 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, or may have no hollow microspheres, but it is preferable that the hollow microspheres 4A be dispersed therein.

[0012] (Groove machining) 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.

[0013] (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, it becomes difficult to flatten fine irregularities by 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.

[0014] (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 3 More 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 step-eliminating performance tends to be obtained.

[0015] In the polishing pad 3 of the present invention, when hollow microspheres 4A are used, air bubbles are encapsulated within the polyurethane resin molding by the hollow microspheres 4A. 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.

[0016] (Regarding step elimination and flattening performance) The polishing pad of the present invention is characterized by having excellent step-eliminating and planarizing capabilities due to the presence of a specific polishing layer. The polishing pad 3 of the present invention has excellent step-eliminating performance. Here, step elimination performance refers to the ability to reduce steps (unevenness) on patterned wafers that have steps during polishing. Figure 3 shows a schematic diagram of an experiment to measure step elimination performance. At the stage of Figure 3(a), there are steps of different heights on the polished object 8. A polishing pad with high step elimination performance will preferentially polish the steps on the patterned wafer as polishing progresses, polishing it to the same height as the non-wiring area in a short time and eliminating the steps (Figure 3(b)). On the other hand, a polishing pad that takes a long time to eliminate the steps on the patterned wafer has low step elimination performance.

[0017] The present invention aims to improve the step elimination performance and flattening performance when polishing an object having steps of different heights. This will be explained in more detail using FIG. 3. For example, the object to be polished is composed of a substrate and a metal film thereon, and the metal film is polished using the polishing pad of the present invention. For example, as shown in FIG. 3, the object to be polished 8 is composed of a substrate 81 and a metal film 82 formed on the substrate (note that FIG. 3 is a cross-sectional view of the object to be polished 8). Before polishing, as shown in FIG. 3(a), the formed metal film 82 has a small thickness from the surface (highest position) 813 of the substrate 81, where the metal film formed directly above the wiring-free portion 811 of the substrate 81 is thin. On the other hand, the metal film formed directly above the wiring portions 812 and 813 of the substrate 81 is thick from the surface of the substrate 81, resulting in steps (82A, 82B). Furthermore, the thickness of the metal film increases as the width of the wiring decreases. That is, the height of the step 82B directly above the wire 813 with a small wire width is X, whereas the height of the step 82A directly above the wire 812 with a large wire width is Y, and X is greater than Y. When polishing such an object 8 to be polished, if polishing is performed with a polishing pad having excellent step elimination and flattening performance, the surface of the metal film 82 of the object 8 to be polished will be flattened regardless of the location of the non-wiring portion 811 and the wiring portions 812 and 813, as shown in Fig. 3(b) , by preferentially polishing the wiring portion 812. Thereafter, the metal film 82 of the object 8 to be polished is polished in a flat state. On the other hand, if polishing is performed with a polishing pad with poor step-eliminating performance, it will take a long time for the metal film directly above the wiring portions 812 and 813 to become equal in thickness to the metal film in the non-wiring portion 811. If polishing is performed with a polishing pad with poor planarizing performance, not only the metal film directly above the wiring portions will be polished, but also other portions, and the metal film will not be flat. The step elimination performance is a performance that indicates the degree to which steps (convex and concave portions) on a patterned wafer that have steps due to polishing are flattened. Specifically, a patterned wafer with concave and convex portions is polished and the remaining steps on the wafer after polishing (the degree to which the steps are flattened) are evaluated. Furthermore, the flattening performance evaluates whether or not there are steps between the metal film in the non-wiring portion and the metal film in the wiring portion after polishing, resulting in a flat surface.

[0018] (crystalline phase, mesophase, amorphous phase) The proportions of the crystalline, mesophase, and amorphous phases in the polishing layer are determined by pulsed NMR. In pulsed NMR, 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 phase (S phase), middle phase (M phase), and long phase (L phase) in order of shortest spin-spin relaxation time, and the proportions of each phase are determined. Regarding the content ratios 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.

[0019] 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 reduction performance may be impaired. On the other hand, an increase in the proportion of soft segments makes the polishing pad softer, which is undesirable because it reduces step elimination and planarization performance. 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. Furthermore, pulsed 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 it was found that the results of pulsed NMR measurements performed in a dry state differ from those of pulsed NMR measurements performed in a wet state.

[0020] 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).

[0021] In the polishing layer of the polishing pad of the present invention, the ratio of the crystalline phase content to the amorphous phase content measured at 40°C by pulsed NMR in a wet state is 0.5 or more and 1.0 or less. The ratio of the crystalline phase content to the amorphous phase content is preferably 0.55 or more and 0.95 or less, more preferably 0.60 or more and 0.90 or less, and even more preferably 0.55 or more and 0.85 or less. Furthermore, the ratio of the mesophase content to the amorphous phase content measured at 40°C by pulsed NMR in a wet state is 0.4 or more and 0.9 or less. The ratio of the mesophase content to the amorphous phase content is preferably 0.45 or more and 0.85 or less, more preferably 0.50 or more and 0.80 or less.

[0022] By ensuring that the ratio of the crystalline phase content to the amorphous phase content in the polishing layer, and the ratio of the intermediate phase content to the amorphous phase content in the polishing layer measured at 40°C by pulse NMR in a wet state, each fall within the above ranges, the proportion of the amorphous phase, which has high mobility during polishing, becomes higher than that of the crystalline phase and the intermediate phase, and the polishing layer softens appropriately during polishing, resulting in a polishing pad with excellent step-eliminating and planarizing performance.

[0023] In the polishing layer of the polishing pad of the present invention, the content of the amorphous phase in the polishing layer measured in a wet state by pulse NMR at 40°C is preferably 30.0% or more and 55.0% or less, more preferably 32.0% or more and 50.0% or less, and even more preferably 35.0% or more and 50.0% or less. By satisfying the above range, the proportion of the amorphous phase with high mobility is appropriately present, and the polishing layer is appropriately softened during polishing, which tends to result in excellent step elimination performance and flattening performance.

[0024] In the polishing layer of the polishing pad of the present invention, the mesophase content in the polishing layer measured at 40°C by pulse NMR in a wet state is preferably 15.0% or more and 35.0% or less, more preferably 17.0% or more and 33.0% or less, and even more preferably 20.0% or more and 30.0% or more.

[0025] In the polishing layer of the polishing pad of the present invention, the content of the crystalline phase in the polishing layer measured by pulse NMR in a wet state at 40°C is 25.0% or more and 45.0% or less, preferably 28.0% or more and 42.0% or less, more preferably 28.0% or more and 35.0% or less. By satisfying the above range, the proportion of the crystalline phase with low mobility is appropriately present, and the polishing layer has appropriate hardness during polishing, which tends to result in excellent step elimination performance and planarization performance.

[0026] <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 a base material is impregnated with resin; flexible materials such as synthetic resins and rubber; and sponge materials using 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.

[0027] 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, when a cushion layer is made of a nonwoven fabric impregnated with polyurethane or a sponge-like material, it is compatible with the polishing layer and can therefore maintain excellent step-eliminating performance.

[0028] <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 cushioning 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.

[0029] <<Polishing pad manufacturing method>> A method for producing the polishing pad 3 of the present invention will be described.

[0030] <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.

[0031] 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.

[0032] 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 the isocyanate-terminated prepolymer and the curing agent; a mixing step of mixing at least the isocyanate-terminated prepolymer and the curing agent to obtain a mixture for molding a molded body; and a molding step of molding the polishing layer 4 from the mixture for molding a molded body.

[0033] The material preparation process, the mixing process, and the molding process will be explained below.

[0034] <Material preparation process> To manufacture the polishing layer 4 of the present invention, an isocyanate-terminated prepolymer, a curing agent, and hollow microspheres are prepared as raw materials for the polyurethane resin foam. Here, the isocyanate-terminated prepolymer is a urethane prepolymer (sometimes simply referred to as a prepolymer) for forming the polyurethane resin foam.

[0035] Each component will be described below.

[0036] (Isocyanate-terminated prepolymer) The isocyanate-terminated prepolymer can contain a polyisocyanate compound-derived structural unit and a polyol-derived structural unit, and 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 a range that does not impair the effects of the present invention. From the viewpoints of adjusting physical properties and handling, two or more different types of isocyanate-terminated prepolymers can be used.

[0037] The isocyanate-terminated prepolymer may be a commercially available product, or may be synthesized by reacting a polyisocyanate compound with a polyol. There are no particular limitations on the reaction, and an addition polymerization reaction may be carried out using a method and conditions known in the art for producing 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.

[0038] (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.

[0039] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI, and more preferably 2,4-TDI.

[0040] (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. The polyol compound used as a raw material for the prepolymer is not particularly limited as long as the object of the present invention can be achieved, but examples thereof include diol compounds, triol compounds, etc., such as ethylene glycol, diethylene glycol (DEG), and butylene glycol; polyether polyol compounds, such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG), polypropylene glycol (PPG), and polyether polycarbonate diol (PEPCD); and polyester polyols.

[0041] Among the above components, in order to achieve a polishing layer in which 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 is 0.5 or more and 1.0 or less, and the ratio of the mesophase content to the amorphous phase content in the polishing layer measured in a wet state by pulsed NMR at 40°C is 0.4 or more and 0.9 or less, it is preferable that the high-molecular-weight polyol-derived structural unit contains a polyoxytetramethylene glycol (PTMG)-derived structural unit and a polyester diol-derived structural unit. In a preferred embodiment, other polyol components may be used in addition to PTMG and polyester diol.

[0042] When a combination of polyoxytetramethylene glycol (PTMG) and polyester diol is used, the weight proportion of PTMG is preferably 30% by weight or more and 80% by weight or less based on the total weight of the high molecular weight polyol compound used as a raw material for the prepolymer.

[0043] The polyester diol is not particularly limited as long as it is a compound of an acid and a diol component, but examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid. Examples of diols used in polyester diols include ethylene glycol, diethylene glycol (DEG), butylene glycol (1,4-butanediol), neopentyl glycol, 1,3-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Among these, polyester diols synthesized from adipic acid and 1,4-butanediol are preferred, as they allow for easy adjustment of the ratio of crystalline and amorphous phases.

[0044] The number average molecular weight (Mn) of the polyester diol for forming the polyester diol-derived structural unit is preferably 600 or more and 2500 or less, more preferably 800 or more and 2000 or less. Here, the number average molecular weight can be measured by gel permeation chromatography (GPC). When measuring the number average molecular weight of the polyol compound from the polyurethane resin, it can also be estimated by GPC after decomposing each component by a conventional method such as amine decomposition. By having a number average molecular weight of 600 to 2500, the polishing pad can be given the necessary rubber elasticity, and the effects of the present invention tend to be obtained.

[0045] (NCO equivalent weight of isocyanate-terminated prepolymer) When two or more types of isocyanate-terminated prepolymers are used, the NCO equivalent of the isocyanate-terminated prepolymer is preferably 400 to 500, more preferably 420 to 490, for an isocyanate-terminated prepolymer containing a PTMG-derived structural unit, and is preferably 550 to 700, more preferably 570 to 660, for an isocyanate-terminated prepolymer forming a polyester diol-derived structural unit. Furthermore, when two or more types of isocyanate-terminated prepolymers are used, the NCO equivalent of the isocyanate-terminated prepolymer after mixing is preferably 400 to 650, more preferably 410 to 570. By satisfying the above ranges, excellent step-eliminating performance and planarizing performance tend to be obtained. 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.

[0046] (additives) As described above, additives such as an oxidizing agent can be added to the material of the polishing layer 4 as needed.

[0047] (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).

[0048] 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.

[0049] (Hollow microspheres) 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 Oil & Fat 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.

[0050] 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 to 200 μm, more preferably 5 to 80 μm, even more preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. The average particle size can be measured using a laser diffraction particle size analyzer (for example, Mastersizer 2000, manufactured by Spectris Co., Ltd.).

[0051] 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.

[0052] 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 each component 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.

[0053] <Mixing process> In the mixing step, the isocyanate-terminated prepolymer obtained in the preparation step, additives, and 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.

[0054] <Forming process> In the molding process, the mixture prepared in the mixing process is poured into a mold preheated to 60-120°C and subjected to primary curing at 100-150°C for 30 minutes to 1 hour. The cured molded product is then removed from the mold and heated at approximately 100-150°C for 2-6 hours for secondary curing to form a cured polyurethane resin (polyurethane resin foam). At this time, the urethane prepolymer and curing agent react to form a polyurethane resin, which hardens 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 urethane prepolymer in the range of 500 to 10,000 mPa·s at a temperature of 50 to 80°C. This can be achieved, for example, by changing the molecular weight (degree of polymerization) of the urethane prepolymer. The urethane prepolymer is heated to approximately 50 to 80°C to become flowable.

[0055] In the molding process, the mixture is reacted in a mold as needed to form a polyurethane resin foam, during which the urethane prepolymer reacts with the curing agent to crosslink and harden.

[0056] 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 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. This results in a polyurethane resin foam with hollow microspheres 4A formed approximately uniformly inside.

[0057] 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.

[0058] 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.

[0059] <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.

[0060] <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 P 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]

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0063] 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)]".

[0064] (About the polishing layer) Two types of urethane prepolymers (PP1 and PP2) were prepared by reacting 2,4-tolylene diisocyanate (TDI) as an isocyanate compound, PTMG and diethylene glycol (DEG) as polyol compounds, and polyester polyol (adipic acid and 1,4-butanediol composite (adipic acid butylene glycol ester)) with diethylene glycol (DEG) as polyol compounds (see Table 1 for the components used in preparing the urethane prepolymers). 1.8 parts of hollow microspheres (balloons: Expancel 920DU20 (Nippon Phillite Co., Ltd.)) with an average particle size of 6.0 μm were added to 100 parts of the urethane prepolymer mixture mixed in the proportions shown in Table 2 to obtain a mixed solution. The resulting mixed solution was placed in a first liquid tank and maintained at 60°C. Next, 26.2 parts of MOCA as a curing agent, separately from the first liquid, were placed in a second liquid tank, heated to 120°C, melted, and maintained at that temperature. 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 to perform 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 the polishing layer B used in Example 1 shown in Table 2. Polishing layers A, C, D, and E were prepared using the same process according to Tables 1 and 2. The density and Shore D hardness of each polishing layer are also shown in Table 2, and the content ratios of the crystalline phase, mesophase, and amorphous phase are shown in Table 3 (measured at 40 ° C in wet and dry states, respectively). In Table 3, T (1), T (2), and T (3) are the relaxation times of the crystalline phase, mesophase, and amorphous phase, respectively, and are expressed in msec (milliseconds). From these data, the predetermined values ​​are shown in Table 4. The measurement methods and conditions for density, Shore D hardness, and pulse NMR measurements (dry and wet conditions) are as follows.

[0065] (density) Density of the polishing layer (g / cm 3 ) was measured in accordance with the Japanese Industrial Standard (JIS K 6505).

[0066] (Shore D hardness) The Shore D hardness of the polishing layer 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.

[0067] (Pulse NMR measurement) Equipment Bruker Minispec mq20 (20MHz) Various 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, it was left to stand for 5 minutes before measurement began. One measurement was taken immediately after the start of measurement, followed by one every 5 minutes thereafter, for a total of six measurements. Of the six measurements, the second through sixth were averaged to obtain the average value. The samples were prepared by punching out 8 mm diameter samples from polishing layers A through 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. Wet samples were also prepared by immersing them in pure water for 24 hours, wiping off the surface moisture, and immediately measuring. The punched samples were filled into the sample tube to a height of 1 to 1.5 cm using the above apparatus and conditions.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] [Table 4]

[0072] (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.

[0073] Examples and Comparative Examples The polishing layers A to E and the cushion layer were each bonded with 0.1 mm thick double-sided tape (a PET substrate with adhesive layers made of acrylic resin on both sides), and double-sided tape was attached to the side of the cushion layer opposite the adhesive layer to produce the polishing pads of Examples 1 to 3 and Comparative Examples 1 and 2.

[0074] (Polishing performance evaluation) Polishing tests were carried out under the following polishing conditions using the polishing pads obtained in Examples 1 to 3 and Comparative Examples 1 and 2. The results are shown in Table 5.

[0075] (polishing conditions) Polishing machine: F-REX300X (manufactured by Ebara Corporation) Disk: 34R (Kinik) Retainer ring: Retainer ring GXKD (manufactured by Ebara Corporation) Rotation speed: (Surface plate) 90 rpm, (Polishing head) 81 rpm Grinding pressure: 1.7psi Polishing agent temperature: 20℃ Abrasive discharge rate: 200 ml / min Abrasive: CSL-9044C (a mixture of CSL-9044C concentrate and purified water at a weight ratio of 1:9) (manufactured by Fujifilm Planar Solutions Co., Ltd.) Polished object: Cu film substrate (disk-shaped, 300 mm diameter) Polishing time: 60 seconds Pad break: 32N 20 minutes Conditioning: Ex-situ 32N 4 scans

[0076] (Step-eliminating performance evaluation test) The polishing pad was placed in a predetermined position on the polishing machine using double-sided tape with an acrylic adhesive, and polishing was performed under the above-mentioned polishing conditions. The step-elimination performance was evaluated by polishing a non-wiring area, a patterned wafer (workpiece) with wiring widths of 0.18 μm / 0.18 μm, and 0.50 μm / 0.50 μm, measuring the remaining step heights with an atomic force microscope (product name "NX-wafer" manufactured by Park Systems) in NC-AFM (non-contact) mode, and measuring the thickness of the Cu film after polishing with a four-probe sheet resistance measurement device (manufactured by KLA-Tencor, product name "RS-200", measurement: DBS mode). More specifically, the height of the step on the patterned wafer (workpiece) before polishing was measured using an atomic force microscope and a four-probe sheet resistance measurement device. The patterned wafer (workpiece) had a 10,000 angstrom-high Cu film remaining on the non-wiring areas, a 21,000 angstrom-high Cu film remaining on the 0.18 μm / 0.18 μm wiring width, and a 14,000 angstrom-high Cu film remaining on the 0.50 μm / 0.50 μm wiring width before polishing. The height of the remaining Cu film on each location was measured using an atomic force microscope and a four-probe sheet resistance measurement device. In Table 5, cases where the difference between the height of the step remaining in all wiring widths after polishing and the height remaining in the area without wiring after polishing was 1000 angstroms or less were marked with an O, and cases where the difference between the height of the step remaining in all wiring widths after polishing and the height remaining in the area without wiring after polishing exceeded 1000 angstroms were marked with an X.

[0077] (Flattening performance evaluation test) The planarization reduction performance was evaluated by measuring the remaining heights of the patterned wafer (object to be polished) after polishing under the above polishing conditions at locations where there were no wiring, 0.18 μm / 0.18 μm, and 0.50 μm / 0.50 μm, using an atomic force microscope (AFM) and a four-probe sheet resistance measurement device under the above measurement conditions. More specifically, the remaining height of each portion of the patterned wafer (object to be polished) was measured using an atomic force microscope under the above measurement conditions. In Table 5, among the remaining heights of all portions, those for which the difference between the maximum and minimum values ​​was 1000 angstroms or less were marked with an O, and those exceeding 1000 angstroms were marked with an X.

[0078] [Table 5]

[0079] The results in Table 5 show that the polishing pads of Examples 1 to 3 have good step-eliminating and planarizing performance because the ratios of the crystalline phase content to the amorphous phase content and the ratios of the mesophase content to the amorphous phase content in the polishing layer measured at 40°C by pulse NMR in a wet state are within appropriate ranges. When comparing different compounding ratios, a tendency toward improved step-eliminating and planarizing performance was observed when the compounding ratio of PTMG-derived structural units was between 30% and 80%. The addition of the strong cohesive force of the ester system improves the balance between the hard segment and the soft segment, resulting in an optimal structure for the polishing layer during polishing. It is believed that if the polishing layer is too soft, step-eliminating and planarizing performance will deteriorate. [Industrial Applicability]

[0080] The present invention contributes to the manufacture and sale of polishing pads and has industrial applicability.

[0081] 1 Polishing equipment 3 polishing pads 4 Polishing layer 4A Hollow microspheres 6 Cushion layer 7 Adhesive layer 8 Object to be polished 81 Base 82 Metal Film 9. Slurry 10 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, the ratio of the crystalline phase content (%) to the amorphous phase content (%) in the polishing layer measured at 40°C by pulse NMR in a wet state is 0.5 or more and 1.0 or less; A polishing pad characterized in that the ratio of the mesophase content (%) to the amorphous phase content (%) in the polishing layer measured at 40°C by pulse NMR in the wet state is 0.4 or more and 0.9 or less.

2. 2. The polishing pad according to claim 1, wherein the content of an amorphous phase in the polishing layer measured at 40°C by pulse NMR in the wet state is 30.0% or more and 55.0% or less.

3. 2. The polishing pad according to claim 1, wherein the content of mesophase in the polishing layer measured at 40°C by pulse NMR in the wet state is 15.0% or more and 35.0% or less.

4. 2. The polishing pad according to claim 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 polyester diol and a structural unit derived from a PTMG.

5. 5. The polishing pad according to claim 4, wherein the polyester diol used to form the polyester diol-derived constitutional units has a number average molecular weight of 600 or more and 2,500 or less.

6. 5. The polishing pad according to claim 4, wherein the PTMG-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.

7. 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 PTMG-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the PTMG structural unit is 400 or more and 500 or less. The polishing pad of claim 4.

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 polyester diol-derived structural unit, and the NCO equivalent of the isocyanate-terminated prepolymer containing the polyester diol structural unit is 550 or more and 700 or less. The polishing pad described in claim 4.

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