Polishing pad and method for manufacturing the same

Abstract

To provide an abrasive pad that is less prone to adhesion of abrasive particles, particularly silicon (Si) components, in the slurry, and a method for manufacturing the same. [Solution] A polishing pad comprising a polishing layer having a polyurethane sheet containing multiple teardrop-shaped bubbles, The polyurethane sheet contains polyurethane resin, The polyurethane resin includes a cationic polyurethane resin. The aforementioned polishing pad.

Description

Technical Field

[0004]

[0001] The present invention relates to a polishing pad used for polishing semiconductor devices and the like.

Background Art

[0002] Since flatness is required for the surfaces of materials such as silicon, substrates for hard disks, mother glass for thin liquid crystal displays, semiconductor wafers, and semiconductor devices, free abrasive grain polishing using a polishing pad is performed. The free abrasive grain method is a method of polishing the processed surface of an object to be polished while supplying a slurry (polishing liquid, polishing slurry) containing abrasive grains between the polishing pad and the object to be polished.

[0003] As a method for planarizing the surface of a semiconductor device or the like, a chemical mechanical polishing (CMP) method is generally used. For a polishing pad for a semiconductor device, pores for holding a polishing slurry, hardness for maintaining the flatness of the semiconductor device surface, and elasticity for preventing scratches on the semiconductor device surface are required on the polishing pad surface. As a polishing pad that meets these requirements, a polishing pad having a polishing layer made of a polyurethane resin foam is used.

[0004] A polyurethane resin foam is usually cured and formed by the reaction of a prepolymer containing a urethane bond-containing polyisocyanate compound and a curing agent (dry molding method). Then, the foam is sliced into a sheet shape to form a polishing pad. A polishing pad having a hard polishing layer manufactured by such a dry molding method (hereinafter sometimes abbreviated as a hard polishing pad) has relatively small substantially spherical bubbles formed inside the foam by means such as addition of hollow fine particles, mechanical foaming by mixing an inert gas, and a chemical foaming agent represented by water. Therefore, pores (openings) capable of holding a slurry during polishing are formed on the polishing surface of the polishing pad formed by slicing. Using hard polishing pads can improve the flatness and polishing rate of the substrate. However, due to their hardness, they can cause defects such as scratches. Furthermore, with the recent miniaturization of wiring widths, there is a growing demand for higher precision polishing, and hard polishing pads are increasingly insufficient to meet these requirements. Therefore, especially in the finishing process, polishing pads with a soft polishing layer manufactured by a wet film deposition method (hereinafter sometimes abbreviated as soft polishing pads) are being used.

[0005] As mentioned above, chemical mechanical polishing technology is used to polish semiconductor devices and the like, and polishing is performed by flowing a polishing slurry between the object to be polished and the polishing pad. The polishing slurry contains polishing particles, and these polishing particles have a zeta potential that varies with pH. For example, unmodified colloidal silica shows a zeta potential close to zero in the pH range below 4, cationic silica shows a strong positive zeta potential in the pH range below 6, and anionic silica shows a strong negative zeta potential regardless of the pH range. On the other hand, dielectric films (silicon nitride (SiN), silicon oxide (SiO2 or TEOS), and polysilicon (Poly-Si)) each have an electric charge. Patent Document 1 describes adjusting the charge of polishing particles according to the dielectric film to be polished, thereby achieving selective polishing that polishes only specific types of films using electrostatic attraction and repulsion.

[0006] Furthermore, Patent Document 2 describes that by using a polishing pad in which the zeta potential of the polished surface at pH 10.0 is +0.1 mV or higher, a high polishing rate can be obtained even when performing CMP using an alkaline slurry at pH 12. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 7074635 [Patent Document 2] International Publication No. 2018 / 021428 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the polishing pad used in Patent Document 2 is obtained by pelletizing thermoplastic polyurethane obtained by continuous melt polymerization, and then forming it into a sheet-like molded body by a molding method such as extrusion molding. It is a non-foaming type hard polishing pad with (almost) no air bubbles inside. Such hard polishing pads are used for polishing in relatively early stages, such as polishing silicon wafers before metal wiring is formed. In contrast, polishing pads (wet-deposited type polishing pads) that are manufactured by a so-called wet film deposition method and consist of a polyurethane sheet containing multiple teardrop-shaped bubbles have multiple large teardrop-shaped bubbles and are soft, so they are used for wafers after metal wiring has been formed or for the final finishing polishing stage. Thus, non-foaming polishing pads and wet-film-forming polishing pads are used in different stages and have different characteristics. Furthermore, Patent Document 2 aims to obtain a high polishing speed when polishing with an alkaline slurry of pH 12, and does not recognize the adhesion of abrasive particles and the problems caused by it (such as scratches) when using an acidic slurry. When using a wet-film-forming polishing pad used for finish polishing, if a large amount of abrasive particles adhere to and accumulate on the polished surface during polishing, they can aggregate and cause scratches and particles. Since finish polishing is the final polishing process, the occurrence of scratches and particles on the workpiece, such as a wafer, at this stage is a major problem. Therefore, there is a great demand for a so-called wet-film-forming polishing pad used for finish polishing that does not easily allow abrasive particles from the slurry to adhere.

[0009] The present invention has been made in view of the above points, and aims to provide a wet-film-forming type polishing pad, that is, a polishing pad containing a plurality of teardrop-shaped bubbles, in which abrasive particles in the slurry, particularly silicon (Si) components, are less likely to adhere to the workpiece during polishing, and a method for manufacturing the same. [Means for solving the problem]

[0010] As a result of diligent research, the inventors have discovered that by including a cationic polyurethane resin in the polyurethane sheet constituting the polishing pad containing multiple teardrop-shaped bubbles, a polishing pad can be obtained in which abrasive particles in the slurry, particularly silicon (Si) components, are less likely to adhere, leading to the present invention. The present invention includes the following embodiments.

[0011] [1] A polishing pad comprising a polishing layer having a polyurethane sheet containing a plurality of teardrop-shaped bubbles, The polyurethane sheet contains polyurethane resin, The polyurethane resin includes a cationic polyurethane resin. The aforementioned polishing pad. [2] The polishing pad according to [1], wherein the proportion of cationic polyurethane resin in the polyurethane resin is 1 to 50% by mass. [3] The polishing pad according to [1] or [2] for polishing an object to be polished using an acidic slurry containing silicon atom-containing abrasive particles. [4] The polishing pad according to any one of [1] to [3], wherein the cationic polyurethane resin is a polyurethane resin containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines. [5] The polishing pad according to [4], wherein the cationic polyurethane resin contains nitrogen atoms derived from a tertiary amine. [6] The polishing pad according to any one of [1] to [5], wherein the cationic polyurethane resin contains a nitrogen atom derived from at least one amine selected from primary to tertiary amines in the polyol compound constituting the polyurethane resin. [7] The polyurethane resin comprises the cationic polyurethane resin and a polyurethane resin other than the cationic polyurethane resin, The polishing pad according to any one of items [1] to [6], wherein the mass ratio of the cationic polyurethane resin to the polyurethane resin other than the cationic polyurethane resin in the polyurethane resin is 1:99 to 50:50. [8] The polishing pad according to [7], wherein the polyurethane resin other than the cationic polyurethane resin is a polyurethane resin that does not contain a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines, nor an anionic ionic group selected from the group consisting of a carboxyl group, a sulfo group, and a phosphate group. [9] The polishing pad according to any one of items [1] to [8], wherein the porosity of the polished surface of the polyurethane sheet is 16 to 50%.

[10] The polishing pad according to any one of [1] to [9], wherein the polyurethane sheet further comprises a hydrophobic additive.

[11] The polishing pad according to

[10] , wherein the hydrophobic additive comprises a paraffinic hydrocarbon.

[12] A step of applying a resin solution composition containing polyurethane resin and an organic solvent to a film-forming substrate, and A step of obtaining a polyurethane sheet by immersing a film-forming substrate coated with the resin solution composition in a solidification solution to solidify the resin solution composition, A method for manufacturing an abrasive pad according to any one of items [1] to

[11] , including, The manufacturing method wherein the polyurethane resin includes a cationic polyurethane resin.

[13] The manufacturing method according to

[12] , wherein the proportion of cationic polyurethane resin in the polyurethane resin is 1 to 50% by mass.

[14] A method for polishing an object to be polished, comprising the step of polishing the object to be polished using a polishing pad described in any one of [1] to

[11] in the presence of an acidic slurry containing silicon atom-containing abrasive grains. [Effects of the Invention]

[0012] According to the present invention, it is possible to suppress the adhesion of abrasive grains in the slurry, particularly silicon (Si) components, to the surface of the polishing pad. Therefore, by using the polishing pad of the present invention, it can be expected to reduce problems (such as scratches) caused by the adhesion of abrasive grains to the polishing pad.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a surface SEM image of the polished pad of Comparative Example 1 after buffing. [Figure 2] FIG. 2 is a surface SEM image of the polished pad of Comparative Example 2 after buffing. [Figure 3] FIG. 3 is a surface SEM image of the polished pad of Example 1 after buffing. [Figure 4] FIG. 4 is a surface SEM image of the polished pad of Example 2 after buffing. [Figure 5] FIG. 5 is a surface SEM image of the polished pad of Example 3 after buffing.

Modes for Carrying Out the Invention

[0014] Hereinafter, modes for carrying out the present invention will be described. <<Polishing Pad>> The polishing pad of the present invention is a polishing pad including a polishing layer having a polyurethane sheet containing a plurality of tear-shaped bubbles, wherein the polyurethane sheet contains a polyurethane resin, and the polyurethane resin contains a cationic polyurethane resin.

[0015] The polyurethane sheet has multiple teardrop-shaped bubbles. The term "teardrop-shaped bubbles" refers to bubbles formed inside the polyurethane sheet by the wet film formation method (anisotropic bubbles with a structure in which the diameter increases from the top (the side in contact with the workpiece) to the bottom of the resin sheet), and is used to distinguish them from the approximately spherical bubbles included in the dry molding method. Therefore, the polyurethane sheet having multiple teardrop-shaped bubbles of the present invention can be rephrased as a polyurethane sheet formed by the wet film formation method. The wet film formation method means a method in which the resin to be formed is dissolved in an organic solvent, the resin-containing solution is applied to a sheet-like substrate, the organic solvent is replaced by passing the substrate through a coagulation solution in which it is dissolved but the resin is not, the substrate is coagulated, and then dried to form a foamed layer. Normally, when a polyurethane sheet is manufactured by the wet film formation method, multiple approximately teardrop-shaped macro bubbles (teardrop-shaped bubbles) are generated inside the polyurethane sheet. Furthermore, when polyurethane sheets are manufactured using a wet film deposition method, in addition to macrobubbles, a large number of much smaller bubbles (microbubbles, microbubbles) are usually formed. In this specification and in the claims, a polyurethane sheet means a sheet whose main component is polyurethane resin (50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more of the total resin constituting the polyurethane sheet is polyurethane resin, and the polyurethane resin may be 100% by mass), and is clearly distinguished from sheets whose main component is other resins (such as silicone resin). In this specification and in the claims, the polishing layer is a layer having a surface (polishing surface) that comes into contact with the workpiece to be polished, such as a semiconductor device, when polishing the workpiece. The polishing pad of the present invention may have other layers, such as a cushion layer, on the side opposite to the polishing layer. In this specification and in the claims, the polyurethane sheet shall not contain nonwoven fabric.

[0016] <Polyurethane resin> Polyurethane sheets contain polyurethane resin. There are no particular restrictions on the type of polyurethane resin; it can be selected from various polyurethane resins according to the intended use. For example, polyester-based, polyether-based, or polycarbonate-based polyurethane resins can be used. Examples of polyester resins include polymers of polyester polyols, such as ethylene glycol or butanediol, and adipic acid, and diisocyanates such as diphenylmethane-4,4'-diisocyanate. Examples of polyether-based resins include polymers of polyether polyols such as polytetramethylene ether glycol and polypropylene glycol with isocyanates such as diphenylmethane-4,4'-diisocyanate. Examples of polycarbonate-based resins include polymers of polycarbonate polyols and isocyanates such as diphenylmethane-4,4'-diisocyanate. These resins may be commercially available resins such as "Crisbon" manufactured by DIC Corporation, "Samplen" manufactured by Sanyo Chemical Industries, Ltd., or "Rezamin" manufactured by Dainichi Seika Kogyo Co., Ltd., or a resin with the desired properties may be manufactured in-house.

[0017] In this specification and in the claims, a cationic polyurethane resin is a polyurethane resin having cationic properties. Preferably, a cationic polyurethane resin is a polyurethane resin that contains in its structure at least one amine-derived nitrogen atom selected from the group consisting of primary to tertiary amines (or contains a group containing such nitrogen atom as a cationic ionic group). In this specification and in the claims, an anionic polyurethane resin is a polyurethane resin having anionic properties. Preferably, an anionic polyurethane resin is a polyurethane resin that contains an anionic ionic group in its structure. Examples of anionic ionic groups include carboxyl groups, sulfol groups, phosphate groups, phenolic hydroxyl groups, and the like, with carboxyl groups being preferred. In this specification and in the claims, a nonionic polyurethane resin is a polyurethane resin having nonionic properties, and preferably, in its structure, it does not have a nitrogen atom or an anionic ionic group derived from at least one amine selected from the group consisting of primary amines to tertiary amines. There are no particular restrictions on the method for producing a polyurethane resin containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines within its structure; known methods may be used as appropriate. For example, a compound containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines can be prepared as a component in the prepolymer that will be used as a raw material for the polyurethane resin and / or as a chain extender, or a compound containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines can be prepared by reacting the components in the prepolymer and / or the chain extender with a compound containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines, and then these raw materials can be reacted to produce the polyurethane resin.

[0018] <Cationic polyurethane resin> The polyurethane resin includes a cationic polyurethane resin. The proportion of cationic polyurethane resin in the polyurethane resin is preferably 1 to 50% by mass, more preferably 2 to 45% by mass, even more preferably 3 to 40% by mass, even more preferably 3 to 35% by mass, even more preferably 3 to 30% by mass, even more preferably 3 to 20% by mass, even more preferably 3 to 10% by mass, even more preferably 3 to 8% by mass, and even more preferably 4 to 6% by mass. When the proportion of cationic polyurethane resin in the polyurethane resin is within the above range, abrasive particles, especially silicon (Si) components in slurries, particularly acidic slurries, are less likely to adhere, and a polishing pad with excellent polishing surface properties can be obtained. Such a polishing pad can be preferably used to polish an object to be polished using an acidic slurry containing silicon atom-containing abrasive particles. The cationic polyurethane resin is preferably a polyurethane resin containing nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines, and more preferably a polyurethane resin containing nitrogen atoms derived from a tertiary amine. These nitrogen atoms function as cations. The statement that the cationic polyurethane resin contains nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines can also be rephrased as the cationic polyurethane resin containing at least one amine selected from the group consisting of primary to tertiary amines (hereinafter, groups having primary to tertiary amines may be referred to as primary to tertiary amino groups, respectively). A polyurethane resin containing nitrogen atoms derived from a primary amine means a polyurethane resin that contains nitrogen atoms in a primary amine, in which two of its three bonds are bonded to hydrogen atoms, and the remaining bond is bonded to a group other than a hydrogen atom. A polyurethane resin containing nitrogen atoms derived from a secondary amine means a polyurethane resin that contains nitrogen atoms from a secondary amine in its structure, where one of its three bonds is bonded to a hydrogen atom, and the remaining two bonds are bonded to groups other than hydrogen atoms. A polyurethane resin containing nitrogen atoms derived from a tertiary amine means a polyurethane resin that contains nitrogen atoms in a tertiary amine, where zero of its three bonds are bonded to hydrogen atoms, and the remaining three bonds are bonded to groups other than hydrogen atoms. The nitrogen atoms may be contained in the main chain structure of the polyurethane resin, or in the side chain structure, but it is preferable that they be contained in the main chain structure. The cationic polyurethane resin preferably contains a nitrogen atom derived from at least one amine selected from primary to tertiary amines in the polyol compound constituting the polyurethane resin. The polyol compound may be a polyol compound (A) constituting the prepolymer, or a polyol compound (A') used as a chain extender (C). A nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines may be included in the structure of the polyurethane resin by one or more groups other than the hydrogen atom bonded to the nitrogen atom being bonded to structural units such as polyols that constitute the polyurethane resin, or by one or more groups other than the hydrogen atom having two or more hydroxyl groups, thus being included in the structure of the polyurethane resin as a polyol unit (in the prepolymer or chain extender) that constitutes the polyurethane resin.

[0019] A nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines may be included in any structural unit constituting the polyurethane resin. Generally, polyurethane resins are obtained by reacting a prepolymer consisting of a polyol compound (A) (hereinafter sometimes referred to as component (A)) and a polyisocyanate compound (B) (hereinafter sometimes referred to as component (B)) with a chain extender (C) (hereinafter sometimes referred to as component (C)). The cationic ionic group may be included in the polyol compound (A) or in the chain extender (C) (for example, the polyol compound (A') in the chain extender (C)). Preferably, the cationic ionic group is included in the chain extender (C). When manufacturing polyurethane resin, the polyol compound (A), polyisocyanate compound (B), and chain extender (C) may be mixed and reacted at the same time, or the polyol compound (A) and polyisocyanate compound (B) may be reacted to produce a urethane bond-containing isocyanate compound (prepolymer), and then the prepolymer and chain extender (C) may be mixed and reacted. The following explains each of the ingredients.

[0020] (Polyol compound (A)) In this specification and in the claims, polyol compound (A) means a compound having two or more alcoholic hydroxyl groups in its molecule. Examples of polyol compounds (A) that can be used include polyester polyols, polyether polyols, polycarbonate polyols, polyacrylic polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, and dimer ols. As the polyol compound (A), diol compounds are preferred, with polyester diols, polyether diols, and polycarbonate diols being more preferred, and polyester diols being particularly preferred. These polyol compounds may be used individually or in combination of multiple polyol compounds.

[0021] (Polyisocyanate compound (B)) In this specification and in the claims, polyisocyanate compound (B) means a compound having two or more isocyanate groups in its molecule. The polyisocyanate compound (B) is not particularly limited as long as it has two or more isocyanate groups in its molecule. For example, diisocyanate compounds having two isocyanate groups in their molecule include m-phenylenediisocyanate, p-phenylenediisocyanate, 2,6-tolylenediisocyanate (2,6-TDI), 2,4-tolylenediisocyanate (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'-biphenyldiisocyanate, and 3,3'-dimeth Examples 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, and ethyridine diisothiocyanate. Diisocyanate compounds are preferred as polyisocyanate compounds, with MDI, 2,4-TDI, and 2,6-TDI being more preferred, and MDI being particularly preferred. These polyisocyanate compounds may be used individually or in combination of multiple polyisocyanate compounds.

[0022] (Chain extension agent (C)) As the chain extension agent (C), for example, a polyol compound (A') and / or a polyamine compound (D) with a lower molecular weight than the polyol compound (A) can be used. Specific examples of low molecular weight polyol compounds (A') include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. In this specification and in the claims, polyamine compound (D) means a compound having two or more amino groups in its molecule. Specific examples of low molecular weight polyamine compounds (D) include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, and hydrazine.

[0023] <Nitrogen atom derived from amine> A nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines may be included, for example, in a polyol compound (component (A) and / or component (A')). That is, a structural unit derived from the polyol compound of a cationic polyurethane resin may have a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines. By using a polyol compound having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines, the nitrogen atom can be included (introduced) into the polyurethane resin, and a cationic polyurethane resin can be obtained. Examples of polyols having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines include N-alkyldialkanolamines such as triethylenetetramine, diethylenetriamine, N-methyldiethanolamine, and N-ethyldiethanolamine, and N-alkyldiaminoalkylamines such as N-methyldiaminoethylamine and N-ethyldiaminoethylamine. A compound containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines may be used as a chain extender (C) (component (A')) or as a polyol compound (component (A)), but it is preferable to use it as a chain extender (C).

[0024] There are no particular restrictions on the proportion of structural units derived from a compound having a nitrogen atom from at least one amine selected from the group consisting of primary to tertiary amines to the total structural units constituting the cationic polyurethane resin. However, among the total structural units constituting the cationic polyurethane resin (structural units derived from polyol compounds, structural units derived from polyisocyanate compounds, structural units derived from chain extenders, and compounds derived from a compound having a nitrogen atom from at least one amine selected from the group consisting of primary to tertiary amines), the proportion of structural units derived from a compound having a nitrogen atom from at least one amine selected from the group consisting of primary to tertiary amines (preferably a polyol compound) is preferably in the range of 0.1 to 30 mol%, more preferably in the range of 0.5 to 20 mol%, even more preferably in the range of 1 to 15 mol%, and still more preferably in the range of 5 to 15 mol%. Furthermore, when a compound having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines is used as a chain extender, the proportion of structural units derived from the compound having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines among the total structural units derived from the chain extender of the cationic polyurethane resin is preferably 1 to 50 mol%, more preferably 3 to 40 mol%, and even more preferably 5 to 30 mol%. Furthermore, when a compound having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines is used as a chain extender, the proportion of structural units derived from the compound having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines among the total structural units derived from the chain extender of the cationic polyurethane resin is preferably 5 to 65% by mass, more preferably 10 to 60% by mass, even more preferably 15 to 55% by mass, even more preferably 15 to 45% by mass, even more preferably 15 to 35% by mass, and particularly preferably 15 to 25% by mass. Furthermore, when using a compound having nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines as a chain extender, the mass ratio of structural units derived from a compound having nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines to structural units derived from a compound that does not have nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines (preferably also does not have cationic ionic groups) is preferably 100:10 to 70, more preferably 100:15 to 65, even more preferably 100:15 to 60, even more preferably 100:15 to 50, even more preferably 100:15 to 40, and particularly preferably 100:20 to 30. The structural units derived from the chain extender of the cationic polyurethane resin are preferably composed of structural units derived from a compound having a nitrogen atom from at least one amine selected from the group consisting of primary to tertiary amines, and structural units derived from a compound that does not have a nitrogen atom from at least one amine selected from the group consisting of primary to tertiary amines (preferably also does not have an anionic ionic group). Furthermore, a compound in the chain extension agent having a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines may have the same structure as a chain extension agent that does not have a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines, except that it contains a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines, or it may have a different structure.

[0025] <Polyurethane resins other than cationic polyurethane resins> The polyurethane resin preferably contains a cationic polyurethane resin and a polyurethane resin other than the cationic polyurethane resin. The mass ratio of the cationic polyurethane resin to the polyurethane resin other than the cationic polyurethane resin in the polyurethane resin is preferably 1:99 to 50:50, more preferably 2:98 to 45:55, even more preferably 3:97 to 40:60, even more preferably 3:97 to 35:65, even more preferably 3:97 to 30:70, even more preferably 3:97 to 20:80, even more preferably 3:97 to 10:90, even more preferably 3:97 to 8:92, and even more preferably 4:96 to 6:94. If the mass ratio of cationic polyurethane resin to non-cationic polyurethane resin in the polyurethane resin is within the above range, it is possible to reduce the adhesion of abrasive particles in the slurry to the polishing surface of the polishing pad.

[0026] There are no particular restrictions on polyurethane resins other than cationic polyurethane resins; any known polyurethane resin may be used. Examples of polyurethane resins other than cationic polyurethane resins include polyurethane resins that do not contain nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines, and polyurethane resins that do not contain (have not introduced) nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines, nor anionic ionic groups selected from the group consisting of carboxyl groups, sulfo groups, phosphate groups, and phenolic hydroxyl groups. Examples of polyurethane resins other than cationic polyurethane resins include anionic polyurethane resins and nonionic polyurethane resins. Among these, polyurethane resins other than cationic polyurethane resins are preferably polyurethane resins that do not contain nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines, more preferably polyurethane resins that do not contain nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines, and anionic ionic groups selected from the group consisting of carboxyl groups, sulfo groups, phosphate groups, and phenolic hydroxyl groups, even more preferably polyurethane resins that do not contain nitrogen atoms derived from at least one amine selected from the group consisting of primary to tertiary amines, and anionic ionic groups, and still more preferably polyurethane resins that do not contain anionic ionic groups or cationic ionic groups.Furthermore, among polyurethane resins other than cationic polyurethane resins, it is preferable to have the same structural units as cationic polyurethane resins, except that structural units derived from compounds containing nitrogen atoms from at least one amine selected from the group consisting of primary to tertiary amines are replaced with structural units derived from compounds that do not contain nitrogen atoms from at least one amine selected from the group consisting of primary to tertiary amines. More preferable are polyurethane resins that have the same structural units as cationic polyurethane resins in the same proportions, except that structural units derived from compounds containing nitrogen atoms from at least one amine selected from the group consisting of primary to tertiary amines are replaced with structural units derived from compounds that do not contain nitrogen atoms from at least one amine selected from the group consisting of primary to tertiary amines.

[0027] <Zeta potential> Zeta potential can be measured using the flow potential method, which measures the potential difference caused by a pressure difference, or the electrophoresis method, which measures the potential difference from the mobility of tracer particles. Measurement using the flow potential method is preferred. In addition, to measure the zeta potential of polyurethane resin, a dry film with a thickness of about 200 μm is prepared by spreading the polyurethane resin (solution) thinly and drying it, and the zeta potential of this dry film is measured. The zeta potential of the polyurethane resin is preferably in the range of 5 to 50 mV at pH 2.9 to 3.1 (preferably pH 2.9), more preferably 10 to 35 mV, and even more preferably 13 to 32 mV.

[0028] (Modulus) Modulus is an index that represents the hardness of a resin. It is the value obtained by dividing the load applied when a non-foamed resin sheet is stretched to 100% (twice its original length) by its cross-sectional area (hereinafter sometimes referred to as 100% modulus). The higher this value, the harder the resin. The polyurethane resin preferably has a 100% modulus of 1 to 10 MPa, more preferably 3 to 8 MPa, and even more preferably 3 to 5 MPa. When the 100% modulus is within the above range, it tends to be easier to balance the polishing rate and the amount of polishing scratches.

[0029] <Hydrophobic additive> The polyurethane sheet preferably contains a hydrophobic additive. The hydrophobic additive acts as a film-forming aid and can improve the film-forming properties of the polyurethane sheet. Various conventional hydrophobic additives can be used as hydrophobic additives. Examples of hydrophobic additives include paraffinic hydrocarbons and nonionic hydrocarbons. Among these, it is preferable to include paraffinic hydrocarbons. Examples of paraffinic hydrocarbons include straight-chain hydrocarbons with 5 to 30 carbon atoms, normal paraffinic hydrocarbons such as liquid paraffin, kerosene, and light oil, branched hydrocarbons with 5 to 40 carbon atoms, and isoparaffinic hydrocarbons such as liquid isoparaffin. The amount of hydrophobic additives included in the polyurethane sheet is not particularly limited as long as a film can be formed on the polyurethane sheet, and any amount can be used as appropriate according to the properties of the polyurethane resin. Generally, as the proportion of cationic polyurethane resin in the polyurethane resin increases, the film-forming ability deteriorates, so the amount of hydrophobic additives may be adjusted to facilitate film formation. Among these, the amount of hydrophobic additive is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 18 parts by mass or less, and even more preferably 16 parts by mass or less per 100 parts by mass of polyurethane resin. On the other hand, there is no particular lower limit on the amount of hydrophobic additive. For example, it may be 0.01 parts by mass or more, 0.1 parts by mass or more, 0.5 parts by mass or more, 1 part by mass or more, 2 parts by mass or more, 4 parts by mass or more, 6 parts by mass or more, 8 parts by mass or more, 10 parts by mass or more, or 12 parts by mass or more per 100 parts by mass of polyurethane resin.

[0030] <Cellulose derivatives> The resin sheet preferably contains a cellulose derivative. By including a cellulose derivative, a microcell structure can be sufficiently formed when a polyurethane resin-containing solution applied to a film-forming substrate is wet-coated. In addition, the brittleness of the polishing pad is less likely to increase, and physical properties such as elongation are less likely to decrease. Examples of cellulose derivatives include ester-based cellulose derivatives, ether-based cellulose derivatives, ether-ester-based cellulose derivatives, and aromatic-containing cellulose conductors. Among these, ester-based cellulose derivatives are more preferred. Examples of ester-based cellulose derivatives include acetylcellulose, triacetylcellulose, acetylbutylcellulose, diacetylcellulose, acetylpropylcellulose, ethylcellulose, cellulose propionate, cellulose butyrate, nitrocellulose, cellulose sulfate, cellulose phosphate, cellulose acetate butyrate, cellulose nitrate acetate, and cellulose acetate propionate. Among these, acetylcellulose, triacetylcellulose, acetylbutylcellulose, diacetylcellulose, and acetylpropylcellulose are preferred, and those in which some or all of the OH groups of cellulose, such as acetylcellulose and triacetylcellulose, are esterified with acetate (particularly acetylcellulose with a substitution degree of 2.41) are more preferred. There are no particular restrictions on the amount of cellulose derivative contained in the polyurethane sheet, but 0.1 to 10 parts by mass is preferred, 0.2 to 8 parts by mass is more preferred, and 0.5 to 5 parts by mass is even more preferred, per 100 parts by mass of polyurethane resin.

[0031] <Other ingredients> The polishing pad of the present invention may contain components other than those mentioned above in the polyurethane sheet, as long as it does not impair the effects of the present invention. Examples of components other than those mentioned above include fillers such as carbon black.

[0032] (Thickness) There are no particular restrictions on the thickness of the polyurethane sheet in the polishing pad of the present invention, but it can be used in the range of, for example, 0.3 to 3.0 mm, preferably 0.5 to 2.0 mm, and more preferably 0.7 to 1.5 mm.

[0033] (Other layers) The polishing pad of the present invention is based on the premise that the surface (polishing surface) of the polyurethane sheet is in contact with the object to be polished, and therefore no other resin layer exists on the polishing surface of the polyurethane sheet. On the other hand, the polishing pad of the present invention may have another resin layer (underlayer, support layer) bonded to the side of the polyurethane sheet opposite to the surface that polishes the workpiece (polishing surface), or it may not have another resin layer bonded to it. The properties of the other resin layer are not particularly limited, but it is preferable that a layer harder than the polyurethane sheet (a layer with high hardness such as Shore A hardness or Shore D hardness) is bonded to it. By providing a layer harder than the polyurethane sheet, it is possible to avoid the fine irregularities of the polishing platen affecting the shape of the polishing surface, and the polishing flatness is further improved. In addition, the overall rigidity of the polishing pad is increased, which suppresses the occurrence of wrinkles when attaching the polishing pad to the polishing platen, and improves workability.

[0034] (Average pore diameter) In this specification and the claims, the average aperture diameter refers to the average of the equivalent diameters of circles calculated based on the area of ​​minute apertures present on the polished surface. The aperture diameter can be calculated by binarizing an image of the polished surface taken with a scanning electron microscope (SEM) using image processing software to confirm the number of apertures, determining the equivalent diameter of a circle from the area of ​​each aperture, and taking the average value of these values ​​as the average aperture diameter. The polished surface is preferably a polished surface after buffing a polyurethane sheet. The polishing pad of the present invention preferably has an average diameter of 20 to 60 μm in the open portions present on the polishing surface, more preferably 30 to 55 μm, even more preferably 38 to 50 μm, and still more preferably 40 to 45 μm.

[0035] (open area ratio) In this specification and in the claims, the porosity ratio means the ratio (%) of the open area to the polished surface. The polished surface is preferably the polished surface after buffing a polyurethane sheet. The porosity ratio can be determined by binarizing an image of the polished surface taken with a scanning electron microscope (SEM) using image processing software, determining the area of ​​each open, and then determining the ratio of the open area per unit area of ​​the polished surface as the porosity ratio (%). The porosity of the polyurethane sheet in the polishing pad of the present invention is preferably in the range of 10 to 50%, more preferably 16 to 50%, even more preferably 16 to 45%, and even more preferably 17 to 42%.

[0036] (Application) The polishing pad of the present invention can be suitably used as a polishing pad when polishing (chemical mechanical polishing (CMP)) workpieces such as semiconductor devices, semiconductor wafers, silicon, and glass. Among these, the polishing pad of the present invention can be suitably used as a polishing pad for semiconductor devices. Furthermore, the polishing pad of the present invention can be suitably used as a polishing pad for polishing metal pattern wafers such as copper, and as a polishing pad for polishing barrier metals. Furthermore, the polishing pad of the present invention can be suitably used for polishing workpieces using a polishing slurry (chemical mechanical polishing). Among these, the polishing pad of the present invention can be suitably used for polishing workpieces using a slurry containing silicon atom-containing abrasive particles, and can be particularly suitably used for polishing workpieces using an acidic slurry containing silicon atom-containing abrasive particles (chemical mechanical polishing).

[0037] <effect> The polishing pad of the present invention contains a cationic polyurethane resin in the polyurethane sheet. By including the cationic polyurethane resin, it is possible to obtain a polishing pad that is less likely to have abrasive particles, especially silicon (Si) components, adhere to it in the slurry. In particular, by including 1 to 50% by mass of the cationic polyurethane resin, the adhesion of abrasive particles, especially silicon (Si) components, in the slurry can be significantly suppressed. The reason why the adhesion of silicon components is suppressed by including 1 to 50% by mass of the cationic polyurethane resin compared to when the cationic polyurethane resin is included in more than 50% by mass is not entirely clear, but it is speculated that if the proportion of cationic polyurethane resin in the polyurethane resin becomes too high, the film-forming ability during wet film formation will decrease, the properties of the polishing surface will change, and the performance in preventing the adhesion of abrasive particles, especially silicon (Si) components, to the polishing surface will decrease (comparison of Example 1 and Example 3 of this embodiment). On the other hand, if the amount of cationic polyurethane resin in the polyurethane resin is 1 to 50% by mass, the above problems will not occur, and it is speculated that the adhesion of abrasive particles to the polishing pad, especially in acidic slurries, can be significantly reduced. Furthermore, the polishing pad described in Patent Document 2 aims to achieve a high polishing speed when polishing with an alkaline slurry of pH 12, and since it is a hard polishing pad without internal bubbles, problems such as film formation issues and changes in the properties of the polished surface are less likely to occur. On the other hand, the wet-formation type polishing pad of the present invention is a soft polishing pad with multiple large teardrop-shaped bubbles, so the effect of the foaming state is extremely large. Thus, the properties of the wet-formation type polishing pad differ greatly from those of the non-foaming type polishing pad, and it is impossible to recognize the above problems and solutions in the wet-formation type polishing pad from the disclosure of Patent Document 2, which deals with a different issue from the present invention and relates to a non-foaming type polishing pad. The effect of including a cationic polyurethane resin (preferably 1 to 50% by mass) in the polyurethane resin constituting the polyurethane sheet of the wet-formation type polishing pad, which makes it difficult for abrasive particles in the slurry, especially abrasive particles in acidic slurries, preferably silicon (Si) components, to adhere to the polishing pad, is remarkable.

[0038] Furthermore, because the polishing pad of the present invention has multiple teardrop-shaped bubbles, it is soft and can be used for finish polishing. Unlike the initial polishing stage where nonwoven fabric type polishing is used, finish polishing is the final stage, so it is necessary to reduce the risk of scratches and particles. As described above, the polishing pad of the present invention can suppress the adhesion, accumulation, and aggregation of abrasive grains in the slurry, especially silicon (Si) components, on the surface of the polishing pad. Therefore, it is expected that problems such as fine scratches caused by polishing the workpiece with aggregates of abrasive grains adhering to the surface of the polishing pad will be reduced. In addition, in finish polishing, if aggregates of abrasive grains containing Si adhere to the workpiece after polishing, it becomes a major problem as it results in defects (particles), but since aggregates containing Si do not easily adhere to the polishing surface of the polishing pad of the present invention, it is expected that the risk of defects caused by the transfer of aggregates from the polishing surface to the workpiece will also be reduced.

[0039] The polishing pad of the present invention can be manufactured, for example, by the following method.

[0040] <<Manufacturing method for polishing pads>> The present invention relates to a manufacturing method comprising the steps of applying a resin solution composition containing a polyurethane resin and an organic solvent to a film-forming substrate, and immersing the film-forming substrate coated with the resin solution composition in a solidifying solution to solidify the resin solution composition and obtain a polyurethane sheet, wherein the polyurethane resin includes a cationic polyurethane resin. The following describes each step.

[0041] <Step of applying the resin solution composition to the film-forming substrate> In the step of applying the resin solution composition to the film-forming substrate, a resin solution composition containing polyurethane resin and an organic solvent is prepared and applied to the film-forming substrate.

[0042] (Polyurethane resin) The resin solution composition contains polyurethane resin, which is the material for the polyurethane sheet. The polyurethane resin includes cationic polyurethane resin. The polyurethane resin, cationic polyurethane resin, and their respective content ratios can be those specified in the description of the polishing pad.

[0043] (organic solvent) As an organic solvent, any solvent that can dissolve polyurethane resin and is miscible with water can be used without particular limitations. Examples include N,N-dimethylformamide (DMF), methyl ethyl ketone, N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and acetone. Among these, DMF or DMAc are preferred. The organic solvent is preferably included in the polyurethane resin-containing solution in an amount such that the solid content concentration in the polyurethane resin-containing solution is preferably 10 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass. Within the above concentration range, the polyurethane resin-containing solution has appropriate fluidity and can be uniformly applied to the film-forming substrate in the subsequent coating process.

[0044] (Hydrophobic additive) The resin solution composition preferably contains a hydrophobic additive. The hydrophobic additives listed in the description of the polishing pad can be used. The amount of hydrophobic additive contained in the resin solution composition is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 18 parts by mass or less, per 100 parts by mass of polyurethane resin. Furthermore, the amount of hydrophobic additive is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, even more preferably 4 parts by mass or more, even more preferably 6 parts by mass or more, even more preferably 8 parts by mass or more, even more preferably 10 parts by mass or more, and even more preferably 12 parts by mass or more, per 100 parts by mass of polyurethane resin.

[0045] (Cellulose derivatives) The resin solution composition may also contain cellulose derivatives in addition to the above components. The cellulose derivatives listed in the description of the polishing pads can be used. The amount of cellulose derivative contained in the resin solution composition is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass, even more preferably 0.5 to 5 parts by mass, even more preferably 0.5 to 3 parts by mass, and even more preferably 0.5 to 2 parts by mass per 100 parts by mass of polyurethane resin.

[0046] (Other ingredients) The resin solution composition may further contain other components besides those mentioned above, as long as they do not impair the effects of the present invention. Other components that can be used include those listed in the description of the polishing pad. The resin solution composition obtained above is continuously applied to the film-forming substrate in a substantially uniform manner, for example, using a knife coater, reverse coater, etc. The film-forming substrate can be any substrate commonly used in this art without particular limitations. Examples of film-forming substrates include flexible polymer films such as polyester films and polyolefin films, and nonwoven fabrics impregnated and fixed with elastic resin, among which polyester films are preferred.

[0047] <Coagulation process> A film-forming substrate coated with a resin solution composition is immersed in a coagulation solution mainly composed of water, which is a poor solvent for polyurethane resin. As the coagulation solution, water, or a mixed solution of water and a polar solvent such as DMF can be used. Examples of polar solvents include water-miscible organic solvents used to dissolve polyurethane resin, such as DMF, DMAc, THF, DMSO, NMP, and acetone. Furthermore, the concentration of the polar solvent in the mixed solvent is preferably 0.5 to 30% by mass. There are no particular restrictions on the temperature of the coagulation solution or the immersion time; for example, immersion at 5-80°C for 5-60 minutes is sufficient.

[0048] <Wash and dry> If necessary, the sheet-like polyurethane resin obtained by solidifying in a solidification bath is either peeled off the film-forming substrate or washed and dried without peeling. The cleaning process removes any organic solvents remaining in the polyurethane resin. Water is a common cleaning solution used for this process. After washing, the polyurethane resin is dried. The drying process can be carried out using conventional methods; for example, it can be dried in a dryer at 80-150°C for about 5-60 minutes. A polyurethane sheet can be obtained through the above process.

[0049] In the method for manufacturing the polishing pad of the present invention, the polishing surface of the polyurethane sheet and / or the surface opposite to the polishing surface may be polished (buffed) as needed. Furthermore, grooves, embossing, and / or holes (punching) may be applied to the polishing surface of the polyurethane sheet, and a base material may be bonded to the polyurethane sheet. In addition, a light-transmitting portion may be provided on the polyurethane sheet and / or the polishing pad. There are no particular restrictions on the grinding method, and grinding can be done using known methods. Specifically, grinding with sandpaper is one example. There are no particular restrictions on the shape of the grooves and embossing; for example, grid-type, concentric circle, and radial shapes can be used. When bonding multiple substrates together to form a multilayer structure, the layers can be bonded and fixed together using double-sided tape or adhesive, applying pressure as needed. There are no particular restrictions on the double-sided tape or adhesive used in this process; any known double-sided tape or adhesive in this field can be arbitrarily selected and used.

[0050] Subsequently, double-sided tape is applied to the side of the polyurethane sheet opposite to the polishing surface, or to the side opposite to the surface bonded to the polyurethane sheet of the base material, and the sheet is cut into a predetermined shape, preferably a disc shape, to complete the polishing pad of the present invention. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be arbitrarily selected and used.

[0051] <Polishing method> The present invention relates to a polishing method for an object to be polished, comprising the step of polishing the object to be polished using the above-described polishing pad in the presence of a slurry containing silicon atom-containing abrasive particles. In the polishing method of the present invention, when polishing, the workpiece may be held using a holding pad while polishing it with a polishing pad. When using the polishing pad of the present invention, the polishing pad is mounted on the polishing platen of the polishing machine so that the polishing surface of the polyurethane sheet faces the workpiece. Then, while supplying polishing slurry onto the polishing pad or the workpiece, the polishing platen is rotated to polish the processed surface of the workpiece. Examples of objects to be polished (held objects) include semiconductor devices, semiconductor wafers, silicon, and glass. Among these, semiconductor devices are preferred as the objects to be polished. Examples of semiconductor device materials include silicon, polysilicon, silicon oxide films, silicon nitrides, and metals such as Cu, W, Al, Ta, and TiN. Furthermore, the polishing pad of the present invention can be suitably used as a polishing pad for polishing metal pattern wafers such as copper, or as a polishing pad for polishing barrier metals. Examples of polishing slurries include those for barrier metals, oxide films, and copper. Preferably, the slurry contains silicon atom-containing abrasive particles. The slurry may also contain other abrasive particles, oxidizing agents, protective components for the workpiece, etching agents, chelating agents, and the like. The abrasive material (abrasive grains) in the polishing slurry is preferably silicon atom-containing abrasive grains, and among these, silica (SiO2) is preferred, and colloidal silica is more preferred. Examples of components that protect the workpiece being polished include triazole compounds, pyrazole compounds, pyramidine compounds, imidazole compounds, guanidine compounds, thiazole compounds, and tetrazole compounds, which act as metal corrosion inhibitors. Furthermore, the properties of the polishing slurry may be acidic or alkaline, but an acidic slurry is preferred. The properties of the polishing slurry can be adjusted by adding acidic components such as sulfuric acid or phosphoric acid, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, organic alkali compounds such as tetramethylammonium hydroxide and choline, and alkaline components such as ammonia to the slurry as needed. [Examples]

[0052] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In Examples 1-3 and Comparative Examples 1-2, unless otherwise specified, "parts" refers to "parts by mass."

[0053] <Comparative Example 1> A polyurethane resin-containing solution was obtained by mixing 100 parts of a 100% modulus 4.0 MPa polyester-based polyurethane resin solution A (solid content concentration 30% by mass) with 40 parts of DMF, 2 parts of water, 5 parts of polyether-modified silicone, and 2 parts of cellulose acetate. Next, a PET film was prepared as a film-forming substrate, and the polyurethane resin-containing solution was applied to it using a knife coater. The film was then immersed in a solidification bath (solidification liquid was water) to solidify the polyurethane resin-containing solution. After solidification, the film-forming substrate was peeled off, washed, and dried to obtain a polyurethane sheet. Subsequently, the skin layer was buffed to open the surface, and a polyethylene terephthalate (PET) sheet was bonded to the side of the polyurethane sheet opposite to the buffed surface. Finally, the buffed surface was embossed with a grid-shaped mold to obtain the polishing pad of Comparative Example 1.

[0054] <Comparative Example 2> A polyurethane resin-containing solution was obtained by mixing 100 parts of a 100% modulus 4.0 MPa polyester-based polyurethane resin solution A (solid content concentration 30% by mass) with 40 parts of DMF, 2 parts of water, 5 parts of isoparaffinic hydrocarbon (DIC Corporation's Crisbon Assister SD-8i), and 2 parts of cellulose acetate. Next, a PET film was prepared as a film-forming substrate, and the polyurethane resin-containing solution was applied to it using a knife coater. The film was then immersed in a solidification bath (solidification liquid was water) to solidify the polyurethane resin-containing solution. After solidification, the film-forming substrate was peeled off, washed, and dried to obtain a polyurethane sheet. Subsequently, the skin layer was buffed to open the surface, and a polyethylene terephthalate (PET) sheet was bonded to the side of the polyurethane sheet opposite to the buffed surface. Finally, the buffed surface was embossed with a grid-shaped mold to obtain the polishing pad of Comparative Example 2.

[0055] <Example 1> A polyurethane resin-containing solution was obtained by mixing 95 parts of a 100% modulus 4.0 MPa polyester-based polyurethane resin solution A (solid content concentration 30% by mass), 5 parts of a 100% modulus 4.1 MPa charge-adjusted polyester-based polyurethane resin solution C (solid content 30% by mass), 40 parts of DMF, 5 parts of isoparaffinic hydrocarbon (DIC Corporation's Crisbon Assister SD-8i), and 0.5 parts of cellulose acetate. The polishing pad of Example 1 was obtained in the same manner as in Comparative Example 2. The polyester polyurethane resin A and the charge-modified polyester polyurethane resin C used consisted of the same polyol component and isocyanate component (MDI), but differed in the composition of their chain extenders (in polyester polyurethane resin A, the chain extender without nitrogen atoms derived from tertiary amines: chain extender with nitrogen atoms derived from tertiary amines in the main chain = 100:0 (weight ratio), while in polyester polyurethane resin C, the chain extender without nitrogen atoms derived from tertiary amines: chain extender with nitrogen atoms derived from tertiary amines = 100:50 (weight ratio)). The proportion of structural units (polyols) derived from the chain extender with nitrogen atoms derived from tertiary amines in the total structural units constituting the charge-modified polyester polyurethane resin solution C was 10 mol%.

[0056] <Example 2> A polyurethane resin-containing solution was obtained by mixing 70 parts of a 100% modulus 4.0 MPa polyester-based polyurethane resin solution A (solid content concentration 30% by mass), 30 parts of a 100% modulus 4.1 MPa charge-adjusted polyester-based polyurethane resin solution C (solid content 30% by mass), 40 parts of DMF, 5.5 parts of isoparaffinic hydrocarbon (DIC Corporation's Crisbon Assister SD-8i), and 0.5 parts of cellulose acetate. The polishing pad of Example 2 was obtained in the same manner as in Comparative Example 2.

[0057] <Example 3> A polyurethane resin-containing solution was obtained by mixing 100 parts of a 100% modulus 4.1 MPa charge-adjusted polyester polyurethane resin solution C (solid content concentration 30% by mass) with 40 parts of DMF, 7 parts of isoparaffinic hydrocarbon (DIC Corporation's Crisbon Assister SD-8i), and 0.5 parts of cellulose acetate. The polishing pad of Example 3 was obtained in the same manner as in Comparative Example 2.

[0058] <Test 1: Zeta potential measurement> For zeta potential measurement, polyurethane resin solution A and / or polyurethane resin solution C were mixed in the ratios used in Comparative Examples 1-2 and Examples 1-3, respectively. Each polyurethane resin was thinly rolled and hot-air dried to produce a dry film with a thickness of approximately 200 μm. The zeta potential of the obtained film surface was measured by the flow potential method in a 1 mM KCl aqueous solution while changing the pH from alkaline to neutral. HCl aqueous solution and KOH aqueous solution were used to adjust the pH. The results for pH 2.9-3.1 are shown in Table 1.

[0059] [Table 1]

[0060] <Test 2: Measurement of Si adhesion after polishing test> For each of the polishing pads in Comparative Examples 1-2 and Examples 1-3, a pad break (pre-use polishing surface preparation using a dresser) was performed, and 10 workpieces were polished continuously under the following polishing conditions. Then, the amount of Si component, which is an abrasive particle, attached to the central part of the land (area surrounded by embossed grooves) on the polishing surface of the polishing pad was evaluated by energy-dispersive X-ray analysis of the SEM image area (0.4 mm × 0.3 mm) of the polishing pad surface using a scanning electron microscope (SEM-EDX) equipped with an energy-dispersive X-ray spectrometer. The amount of Si deposited was evaluated according to the following criteria, and a score of B or higher was considered acceptable. A: Si adhesion amount is 5.0% by mass or less. B: Si adhesion amount is greater than 5.0% by mass and less than or equal to 5.5% by mass. C:Si adhesion amount is greater than 5.5% by mass and less than or equal to 6.0% by mass. D: Si adhesion amount exceeds 6.0% by mass The results are shown in Table 2.

[0061] <Test Conditions> Dresser: 3M Diamond Dresser A188 Bad Break: 30N x 30 minutes Polishing slurry: Strongly acidic (pH 2-3) colloidal silica slurry Workpiece to be polished: Silicon wafer with TEOS film Polishing pressure: 2 psi Polishing time: 1 minute Slurry flow rate: 200 mL / min Conditioning: Ex-situ 30N, 4 scans, 16 seconds

[0062] [Table 2]

[0063] <Result 1> Compared to the polishing pads of Comparative Examples 1 and 2, the polishing pads of Examples 1 to 3, which contain cationic polyurethane resin, showed less silicon component adhesion and were found to suppress abrasive particle adhesion. Furthermore, considering the zeta potential, Example 3 (with 100% by mass of charge-adjusting resin) was expected to show the greatest reduction in adhesion. However, as can be seen from the results of Test 2, the polishing pads of Examples 1 and 2 showed an unexpected result: the amount of adhesion was smaller than that of the polishing pad of Example 3, which had the highest zeta potential (Table 2).

[0064] (Test 3: Measurement of average hole diameter and porosity) The average pore diameter and pore ratio of the polishing pads for Comparative Examples 1-2 and Examples 1-3 were calculated by observing nine locations on the polishing surface of a polyurethane sheet using a scanning electron microscope (JEOL Ltd., JMS-5500LV) at 100x magnification, and then binarizing these images using image processing software (Nikon Corporation, ImageAnalyzerV20LABVer.1.3). The average pore diameter was calculated by checking the number of apertures after binarization, determining the equivalent diameter of a circle from the area of ​​each pore, and taking the average value. The pore ratio was calculated by determining the area of ​​each pore after binarization and taking the ratio of the pore area per unit area of ​​the polishing surface as the pore ratio (%). The results are shown in Table 3 and Figures 1-5.

[0065] [Table 3]

[0066] <Test 4: Measurement of Si adhesion amount after immersion test> For the polyester-based polyurethane resin solution A and charge-adjusted polyurethane resin solution C used in Comparative Examples 1-2 and Examples 1-3, the polyurethane resin solution was thinly rolled out and hot-air dried in the same manner as in Test 1 to produce a dry film with a thickness of approximately 200 μm. The obtained film (3 cm × 5 cm) was immersed and shaken in 60 mL of acidic colloidal slurry at 100 rpm for 2 hours, and then washed by immersion in 60 mL of 1 mM HNO3 aqueous solution for 5 minutes. The washed film was ultrasonically immersed in 30 mL of 1 M HNO3 aqueous solution for 1 hour, and the resulting solution was filtered. After filtering, 20 mL of the filtrate was subjected to ICP emission spectrometer (PerkinElmer Avio 500) to measure the Si content. The results are shown in Table 4.

[0067] [Table 4]

[0068] <Result 2> The polishing pads of Examples 1 and 2, in which the proportion of cationic polyurethane resin to the polyurethane resin was 5% by mass and 30% by mass, respectively, did not show significant deterioration of the polishing surface compared to the polishing pad of Example 3, in which the proportion of cationic polyurethane resin was 100% by mass (Figures 3 to 5). As mentioned above, considering the zeta potential, Example 3 (100% charge-adjusting resin) was expected to have the lowest amount of adhesion. However, when comparing Examples 1-2 and Example 3, the polishing pads of Examples 1-2 actually had less adhesion than the polishing pad of Example 3 (Table 2). Therefore, in Test 3, the polished surfaces of the polishing pads of Examples 1-3 and Comparative Examples 1-2 were examined after buffing. The polishing pad of Example 3 had a worse surface condition compared to the polishing pads of Examples 1-2 and Comparative Example 2 (insufficient pores were not formed by buffing, resulting in an uneven polished surface (Table 3, Figure 5)). Furthermore, in Test 4, when film formation was performed without wet deposition using only polyurethane resin solution A or polyurethane resin solution C, and the surface condition was not deteriorated without teardrop-shaped bubbles or surface pores, the amount of Si adhesion was examined. The resin solution C containing cationic polyurethane resin had a slightly smaller amount of Si adhesion than resin solution A which does not contain cationic polyurethane resin (Table 4). Based on these results, it is speculated that in polishing pads obtained by wet deposition, if the proportion of cationic polyurethane resin is too high, the surface condition after wet deposition deteriorates, increasing the specific surface area of ​​the polishing surface and thus increasing the amount of adhesion. From the above, it is considered that the polishing pads of Examples 1 to 3, which contain cationic polyurethane resin, can reduce the adhesion of abrasive particles during polishing of the workpiece, and that the polishing pads of Examples 1 to 2, in which the proportion of cationic polyurethane resin is 1 to 50% by mass, can further significantly reduce the amount of abrasive particles adhering without causing significant deterioration of the polishing surface. [Industrial applicability]

[0069] According to the present invention, it is possible to suppress the adhesion of abrasive particles, particularly silicon (Si) components, from the slurry to the surface of the polishing pad. Therefore, the polishing pad and its manufacturing method according to the present invention have industrial applicability.

Claims

1. A polishing pad comprising a polishing layer having a polyurethane sheet containing multiple teardrop-shaped bubbles, The polyurethane sheet contains polyurethane resin, The polyurethane resin includes a cationic polyurethane resin. The aforementioned polishing pad.

2. The polishing pad according to claim 1, wherein the proportion of cationic polyurethane resin in the polyurethane resin is 1 to 50% by mass.

3. A polishing pad according to claim 1 or 2 for polishing an object to be polished using an acidic slurry containing silicon atom-containing abrasive particles.

4. The polishing pad according to claim 1 or 2, wherein the cationic polyurethane resin is a polyurethane resin containing a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines.

5. The polishing pad according to claim 4, wherein the cationic polyurethane resin contains nitrogen atoms derived from a tertiary amine.

6. The cationic polyurethane resin contains a nitrogen atom derived from at least one amine selected from primary to tertiary amines in the polyol compound constituting the polyurethane resin. The polishing pad according to claim 1 or 2.

7. The polyurethane resin comprises the cationic polyurethane resin and a polyurethane resin other than the cationic polyurethane resin. The polishing pad according to claim 1 or 2, wherein the mass ratio of the cationic polyurethane resin to the polyurethane resin other than the cationic polyurethane resin in the polyurethane resin is 1:99 to 50:

50.

8. The polishing pad according to claim 7, wherein the polyurethane resin other than the cationic polyurethane resin is a polyurethane resin that does not contain a nitrogen atom derived from at least one amine selected from the group consisting of primary to tertiary amines, nor an anionic ionic group selected from the group consisting of a carboxyl group, a sulfo group, and a phosphate group.

9. The polishing pad according to claim 1 or 2, wherein the porosity of the polishing surface of the polyurethane sheet is 16 to 50%.

10. The polishing pad according to claim 1 or 2, wherein the polyurethane sheet further comprises a hydrophobic additive.

11. The polishing pad according to claim 10, wherein the hydrophobic additive comprises a paraffinic hydrocarbon.

12. A step of applying a resin solution composition containing polyurethane resin and an organic solvent to a film-forming substrate, and A step of obtaining a polyurethane sheet by immersing a film-forming substrate coated with the resin solution composition in a solidification solution to solidify the resin solution composition, A method for manufacturing an abrasive pad according to claim 1, comprising: The manufacturing method wherein the polyurethane resin includes a cationic polyurethane resin.

13. The manufacturing method according to claim 12, wherein the proportion of cationic polyurethane resin in the polyurethane resin is 1 to 50% by mass.

14. A method for polishing an object to be polished, comprising the step of polishing the object to be polished using a polishing pad according to claim 1 or 2 in the presence of an acidic slurry containing silicon atom-containing abrasive particles.

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