Polishing pad, method for producing polishing pad, and method for polishing surface of optical material or semiconductor material

Abstract

The purpose of the present invention is to provide a polishing pad capable of reducing start-up processing time and suppressing occurrence of scratches at an initial stage of polishing.　This polishing pad has a polishing layer. The polishing layer contains a polyurethane resin and a low-molecular-weight polyol, and includes substantially teardrop-shaped air bubbles. The proportion of the mass (mg) of the low-molecular-weight polyol to the mass (g) of the polishing layer is 0.1-8.0 mg / g.

Description

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

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

[0002] The polishing of semiconductor devices is performed using the chemical mechanical polishing (CMP) method. In the CMP method, the chemical components contained in the polishing agent (polishing slurry) increase the mechanical polishing (surface removal) effect due to the relative motion between the polishing agent and the workpiece, enabling high-speed polishing and the acquisition of a smooth polished surface. In such CMP methods, stabilizing the polishing rate is desirable from the viewpoint of improving productivity and yield. Generally, the polishing rate at the start of polishing is lower than the polishing rate in a steady state. Therefore, in the CMP method, it is particularly desirable to shorten the time it takes for the polishing rate to become nearly constant (called the start-up time), that is, to improve the start-up speed.

[0003] Various studies have been conducted to shorten such start-up processing time. For example, Patent Document 1 relates to an abrasive cloth comprising a base layer and a porous surface layer, wherein the surface layer has pores with an average diameter of 1 μm to 30 μm. Patent Document 1 aims to improve productivity by reducing the time required for start-up processing as much as possible. Patent Document 2 relates to an abrasive cloth comprising a base layer and a nap layer formed on the base layer, wherein the nap layer has bubbles opening on the surface of the nap layer, and the ratio of "the opening diameter of the bubbles on the surface" to "the distance from the surface to the deepest part of the bubbles" is 1 / 10 to 1 / 3. Patent Document 2 claims that the start-up time (break-in time) can be shortened.

[0004] Japanese Patent Publication No. 2006-075914 Japanese Patent Publication No. 2007-160474

[0005] Furthermore, in recent years, with the miniaturization of wiring widths, there is a demand for more precise polishing with fewer polishing scratches (especially fewer scratches in the initial stages of polishing). Patent documents 1 and 2 mentioned above do not describe suppressing scratches in the initial stages of polishing. Thus, in addition to shortening the start-up processing time, which has been a challenge in the past, there is a need to suppress the occurrence of scratches in the initial stages of polishing.

[0006] The present invention aims to provide a polishing pad that can shorten the start-up processing time and suppress the occurrence of scratches in the initial stages of polishing.

[0007] As a result of diligent research by the present inventors to solve the above problems, they discovered that the above problems can be solved by incorporating a specific amount of low molecular weight polyol into the polishing layer, and thus completed the present invention. Specific aspects of the present invention are as follows.

[0008] [1] A polishing pad having a polishing layer, wherein the polishing layer comprises a polyurethane resin and a low molecular weight polyol, has substantially teardrop-shaped bubbles, and the ratio of the mass (mg) of the low molecular weight polyol to the mass (g) of the polishing layer is 0.1 mg / g or more and 8.0 mg / g or less. [2] The polishing pad according to [1], wherein no covalent bond is formed between the polyurethane resin and the low molecular weight polyol. [3] The polishing pad according to [1] or [2], wherein the low molecular weight polyol comprises diethylene glycol. [4] The polishing pad according to any one of [1] to [3], wherein the polishing layer further comprises a nucleating agent. [5] The polishing pad according to [4], wherein the nucleating agent comprises a cellulose derivative. [6] A method for manufacturing the polishing pad according to any one of [1] to [5], comprising the step of using a wet film formation method. [7] A method for polishing the surface of an optical material or a semiconductor material, comprising the step of using the polishing pad according to any one of [1] to [5]. [8] A polishing pad manufactured by the method according to [6].

[0009] The polishing pad of the present invention can shorten the start-up processing time and suppress the occurrence of scratches in the initial stages of polishing.

[0010] This graph shows the FID signal obtained by pulsed NMR for polyurethane resin. This graph shows the FID signal of each component after waveform separation. This is a cross-sectional photograph of the polishing pad of Example 1. This is a cross-sectional photograph of the polishing pad of Comparative Example 1. This is a cross-sectional photograph of the polishing pad of Comparative Example 2. This is the ion chromatogram of the measurement sample of Example 1. This is the ion chromatogram of the measurement sample of Comparative Example 1. This shows the intensity factor (a) obtained by pulsed NMR in the initial state. ｉ This is a graph of the measurement results of the intensity factor (a) measured by pulse NMR in the initial state. This is a schematic diagram of the wear test. The intensity factor (a) measured by pulse NMR in Example 1. ｉ This is a graph of the measurement results (over time) of ). For Comparative Example 1, the intensity factor (a) obtained by pulse NMR ｉ This is a graph of the measurement results (over time) of ). For Comparative Example 2, the intensity factor (a) obtained by pulse NMR ｉ This is a graph of the measurement results (over time) of ) for Example 1, specifically the relaxation time (t) measured by pulsed NMR. ｉ This is a graph of the measurement results (over time) of ). For Comparative Example 1, the relaxation time (t) measured by pulsed NMR. ｉ This is a graph of the measurement results (over time) of ). For Comparative Example 2, the relaxation time (t) measured by pulsed NMR. ｉ This is a graph of the measurement results (over time) for the following: Graphs of the measurement results of the polishing rate (Å / min) for Examples 1 to 5. Graphs of the measurement results of the polishing rate (Å / min) for Comparative Examples 1 to 3. Graphs of the measurement results of the number of scratches for Examples 1 to 5. Graphs of the measurement results of the number of scratches for Comparative Examples 1 and 3.

[0011] (Effect) The inventors have unexpectedly discovered that by incorporating a specific amount of low-molecular-weight polyol into the polishing layer, it is possible to obtain a polishing pad that can shorten the start-up processing time and suppress the occurrence of scratches in the initial stages of polishing. The details of why these properties are obtained are not clear, but the following can be inferred.

[0012] Polyurethane resin is a synthetic resin with plasticity and elasticity, produced by reacting components such as polyols and isocyanates. Components of polyurethane resin include polyisocyanates, low-molecular-weight polyols, polyamines, and high-molecular-weight polyols. In polyurethane resin, the portion formed by polyisocyanates, low-molecular-weight polyols, and polyamines is called the hard segment. The hard segment forms a crystalline structure, thereby exhibiting physical properties such as hardness and strength. On the other hand, the portion of the high-molecular-weight polyol in polyurethane resin is called the soft segment. The soft segment forms amorphous regions or a rubbery state, thereby improving the flexibility and elasticity of the material.

[0013] In polyurethane resin, suppressing the aggregation of hard segments reduces the boundary between hard and soft regions. Conversely, as the aggregation of hard segments in polyurethane resin progresses, it separates into hard and soft regions. In polishing pads using polyurethane resin as the polishing layer, as the aggregation of hard segments of the polyurethane resin progresses, regions with different resin properties become widespread in the polishing layer. In this case, it is presumed that clumps of highly crystalline hard segments (aggregated regions) come into contact with the workpiece during polishing, causing polishing scratches.

[0014] Here, as in the present invention, it is presumed that adding a low molecular weight polyol to the polyurethane resin alleviates the aggregation of hard segments. When a polyurethane resin sheet is formed by the wet film formation method described later, the solvent in the resin solution evaporates upon contact with the water bath, causing the polyurethane resin to precipitate. Normally, because the hard segments in the polyurethane resin have a high affinity for each other, it is thought that the hard segments crystallize in an aggregated state. On the other hand, when a resin solution with added low molecular weight polyol is used, it is presumed that when the polyurethane resin precipitates, the low molecular weight polyol, which has high compatibility with the hard segments, enters between multiple hard segments. Therefore, it is presumed that a space is created between multiple hard segments, alleviating the aggregation of hard segments. This is thought to be due to the low molecular weight polyol portion contained as a component in the polyurethane resin attracting the low molecular weight polyol added to the resin solution.

[0015] In polishing with a polishing pad, polishing performance is achieved when the abrasive (polishing slurry) sufficiently adheres to (penetrates) the surface of the polishing layer. Generally, since the polishing pad is dry before polishing, it often takes some time from the start of polishing for the polishing slurry to penetrate the polishing pad. This is thought to be one of the reasons why sufficient polishing performance cannot be achieved in the initial stages of polishing. As mentioned above, if the hard segments in the polishing layer are highly aggregated, the polishing slurry can easily penetrate the soft segments, but it is presumed that it is difficult for the polishing slurry to penetrate between multiple aggregated hard segments. On the other hand, as mentioned above, if low molecular weight polyols are interposed between multiple hard segments, it is presumed that the presence of the low molecular weight polyols makes it easier for the polishing slurry to penetrate between the hard segments. This is presumed to be because the low molecular weight polyols, which are hydrophilic due to the presence of hydroxyl groups, easily attract the polishing slurry, which is in an aqueous solution state.

[0016] The following describes the polishing pad, the method for manufacturing the polishing pad, and the method for polishing the surface of an optical material or semiconductor material according to the present invention. In this specification and in the claims, when numerical ranges are expressed using "A to B", the range includes the two end numbers, A and B. In this specification, "startup processing time" means the time from the start of supplying the polishing slurry until the polishing rate stabilizes at a certain level. In this specification, "initial polishing" means the period from the start of polishing until the startup processing is completed (until the startup processing time).

[0017] 1. Polishing Pad The polishing pad of the present invention is a polishing pad having a polishing layer, wherein the polishing layer contains a polyurethane resin and a low molecular weight polyol, has substantially teardrop-shaped bubbles, and the ratio of the mass (mg) of the low molecular weight polyol to the mass (g) of the polishing layer is 0.1 mg / g or more and 8.0 mg / g or less. The polishing pad of the present invention can shorten the start-up processing time and suppress the occurrence of scratches in the initial stages of polishing by having the polishing layer contain a specific amount of low molecular weight polyol.

[0018] (Low Molecular Weight Polyols) Low molecular weight polyols refer to polyols with a molecular weight of 50 to 500 g / mol. Low molecular weight polyols are not particularly limited, but low molecular weight diols are preferred. Low molecular weight polyols are not particularly limited, but may include or consist of aliphatic polyol compounds, aromatic polyol compounds, or combinations thereof. Examples of aliphatic polyol compounds include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, methylene glycol, or combinations of two or more of these. Examples of aromatic polyol compounds include bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, hydroquinone, or combinations of two or more of these. Examples of low molecular weight polyols include ethylene glycol, 1,4-butanediol, diethylene glycol, or a combination of two or more of these, with diethylene glycol being preferred. Ethylene glycol and 1,4-butanediol have structures similar to those of diethylene glycol and therefore produce similar effects. The low molecular weight polyol may contain diethylene glycol or may be composed of diethylene glycol.

[0019] It is preferable that no covalent bond is formed between the polyurethane resin and the low molecular weight polyol. The low molecular weight polyol may not originate from the polyurethane resin itself, but may be added to the polyurethane resin. The low molecular weight polyol may also be added to the solution containing the polyurethane resin, which is the raw material solution, in the wet film formation method described later.

[0020] The ratio of the mass (mg) of low molecular weight polyol to the mass (g) of the polishing layer (mass of low molecular weight polyol (mg) / mass (g) of the polishing layer) is 0.1 mg / g or more and 8.0 mg / g or less. By having the above ratio of 0.1 mg / g or more and 8.0 mg / g or less, the start-up processing time can be shortened and the occurrence of scratches in the initial stages of polishing can be suppressed. In some cases, by having the above ratio of 8.0 mg / g or less, it is also possible to prevent the low molecular weight polyol from dissolving and adsorbing onto the workpiece during polishing. The lower limit of the above ratio may be 0.12 mg / g or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.45 or more. The above ratio may be 0.1 mg / g or more and 7.5 mg / g or less, 0.1 mg / g or more and 5 mg / g or less, 0.1 mg / g or more and 4 mg / g or less, 0.1 mg / g or more and 3.5 mg / g or less, 0.1 mg / g or more and 3.1 mg / g or less, or 0.1 mg / g or more and 3 mg / g or less. The ratio of the mass (mg) of low molecular weight polyol to the mass (g) of the polishing layer can be measured based on the procedure and method described in the [Examples] below. The above ratio value measured in this way will include values ​​for both low molecular weight polyol derived from the polyurethane resin components and low molecular weight polyol added to the polyurethane resin, but the value for low molecular weight polyol derived from the polyurethane resin components is extremely small. Therefore, the measured above ratio value can be considered to be approximately the value for low molecular weight polyol added to the polyurethane resin.

[0021] (Polyurethane Resin) There are no particular restrictions on the type of polyurethane resin; it is acceptable to select from various polyurethane resins according to the intended use. For example, polyester, polyether, or polycarbonate resins can be used. Polyurethane resins can be produced by reacting polyisocyanates, high-molecular-weight polyols, and optional components such as chain extenders. Examples of polyester resins include polymers of polyester polyols, which are reaction products of ethylene glycol or butylene glycol with adipic acid, and diisocyanates such as diphenylmethane-4,4'-diisocyanate. Examples of polyester resins include polymers of polyester polyols, which are reaction products of 1,4-butanediol and adipic acid, and a chain extender containing 1,4-butanediol and trimethylolpropane, and 4,4'-diphenylmethane diisocyanate (MDI). 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 with isocyanates such as diphenylmethane-4,4'-diisocyanate. These resins may be those available on the market, such as "Crisbon®" from DIC Corporation, "Samplen®" from Sanyo Chemical Industries, Ltd., and "Rezamin®" from Dainichi Seika Kogyo Co., Ltd., or resins with desired properties may be manufactured in-house.

[0022] The polyurethane resin used preferably has a specific 100% resin modulus. The 100% resin modulus is an index representing the hardness of the resin, and is the value obtained by dividing the load applied when a non-foamed resin sheet is stretched to 100% (stretched to twice its original length) by the cross-sectional area (hereinafter sometimes referred to as the 100% modulus). The higher this value, the harder the resin. The polyurethane resin used preferably has a 100% resin modulus of 1 to 20 MPa, and more preferably has a 100% resin modulus of 3 to 18 MPa. When the 100% resin modulus is within the above range, defects can be reduced when polishing wafers with wiring metal. The 100% resin modulus of the polyurethane resin can be measured based on the procedure and method described in the [Examples] below.

[0023] Polyurethane resin sheets are primarily composed of polyurethane resin, but may also contain other known wet film-forming resins.

[0024] In this specification, a high-molecular-weight polyol is a polyol with a number-average molecular weight exceeding 1000 g / mol. The number-average molecular weight of the above high-molecular-weight polyol refers to the molecular weight in polystyrene equivalent, measured by gel permeation chromatography (GPC) under the following conditions: <Measurement conditions> Column: Ohpak SB-802.5HQ (exclusion limit 10000) Mobile phase: 5 mM LiBr / DMF Flow rate: 0.5 mL / min (26 kg / cm) ２ Oven: 60°C Detector: RI 40°C Sample volume: 20 μL

[0025] (Nurturing agent) The polished layer may further contain a nucleating agent. The nucleating agent is not particularly limited, but may include or consist of a cellulose derivative, an inorganic salt, or a combination of two or more of these. The cellulose derivative is not particularly limited, but may include or consist of cellulose acetate, cellulose propionate, cellulose butyrate, or a combination of two or more of these. Of these, cellulose acetate is preferred.

[0026] When manufacturing polyurethane resin by the wet film deposition method described later, the above-mentioned nucleating agent has the effect of suppressing the elution of hydrophilic additives such as low molecular weight polyols into the water bath and retaining the hydrophilic additives in the polyurethane resin (in the polished layer). If the resin solution used as the raw material for the wet film deposition method does not contain the nucleating agent, the rate at which the hydrophilic additives elute into the water bath is faster than the rate at which the polyurethane resin precipitates, making it difficult to retain the hydrophilic additives in the polyurethane resin. On the other hand, if the resin solution contains the nucleating agent, the rate at which the polyurethane resin precipitates increases, making it easier for the hydrophilic additives to be incorporated into the polyurethane resin before they elute into the water bath.

[0027] The ratio of the mass (mg) of the nucleating agent to the mass (g) of the polishing layer (mass (mg) of the nucleating agent / mass (g) of the polishing layer) is not particularly limited, but may be between 1 mg / g and 35 mg / g. When a cellulose derivative is used as the nucleating agent, since the cellulose derivative is insoluble in water (water bath), it is assumed that, in principle, the cellulose derivative blended into the resin solution that serves as the raw material for the wet film formation method is contained directly in the urethane resin (in the polishing layer). Therefore, the ratio of the mass (mg) of the nucleating agent to the mass (g) of the polishing layer can be calculated based on the concentration of the nucleating agent in the polyurethane resin solution described later.

[0028] (Film-forming aid) The polishing layer may further contain a film-forming aid. Examples of film-forming aids include hydrophobic surfactants. Examples of hydrophobic surfactants include paraffinic surfactants such as isoalkanes; nonionic surfactants such as copolymers of ethylene oxide and propylene oxide, polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, perfluoroalkyl ethylene oxide adducts, glycerin fatty acid esters, propylene glycol fatty acid esters, and polyether-modified silicones; and anionic surfactants such as alkyl carboxylic acids. The above compounds can be used as film-forming aids individually or in combination of two or more. Paraffinic surfactants, nonionic surfactants, or combinations thereof are preferred as film-forming aids, and a combination of a paraffinic surfactant and a copolymer of ethylene oxide and propylene oxide is more preferred.

[0029] The ratio of the mass of the film-forming aid (mg) to the mass of the polishing layer (g) (mass of film-forming aid (mg) / mass of polishing layer (g)) is not particularly limited, but is preferably 10 mg / g or less.

[0030] (Other components) The abrasive layer may further contain foam-suppressing agents. Examples of foam-suppressing agents include hydrophilic surfactants. Examples of hydrophilic surfactants include anionic surfactants such as carboxylates, sulfonates, sulfates, and phosphates, and cellulose esters.

[0031] (Abrasive layer) The roughly teardrop-shaped bubbles in the abrasive layer are anisotropic and have a vertically elongated bubble structure from the abrasive surface to the opposite surface.

[0032] Around the above-mentioned slightly tear-shaped bubbles, there are small-diameter communication holes that communicate in a three-dimensional network pattern. The average opening diameter of the bubbles in the polishing layer is not particularly limited, but is preferably 10 to 70 μm, and can also be 15 to 60 μm, 20 to 50 μm, or 25 to 40 μm. The average opening diameter of the bubbles in the polishing layer can be measured by magnifying the surface of the polishing layer 50 times with a scanning electron microscope (manufactured by JEOL Ltd., JSM-5000LV) and processing the obtained image with image processing software (Image Analyzer V20LAB Ver. 1.3) as described in the [Examples] below.

[0033] The polishing rate indicated by the polishing pad is not particularly limited, but is preferably 150 Å / min or more, more preferably 180 Å / min or more, and most preferably 200 Å / min or more. Also, the polishing rate is not particularly limited, but can also be 1000 Å / min or less, 800 Å / min or less, or 700 Å / min or less. The above numerical ranges regarding the polishing rate can be arbitrarily combined. The polishing rate indicated by the polishing pad can be measured based on the procedures and methods described in the [Examples] below.

[0034] The polishing pad may further include a base material layer and / or an adhesive tape layer. The polishing pad can be composed of a polishing layer, a base material layer, and an adhesive tape layer. The polishing pad can have a support member selected from a flexible film such as a polyethylene terephthalate (hereinafter abbreviated as PET) film, a non-woven fabric, and a woven fabric on the opposite surface side (lower surface side) to the polishing surface of the above-mentioned polishing layer. On the lower surface side of the support member, a double-sided tape for attaching the polishing pad to the polishing platen with release paper on the other surface side (lowermost surface side) is bonded.

[0035] (Structural Analysis by Pulse NMR) In pulse NMR, an FID signal with excellent quantitative properties can be obtained by detecting a response signal to a pulse radio wave. Therefore, the phase separation structure of the polyurethane resin can be analyzed. The initial value of the FID signal is proportional to the number of protons in the measurement sample. If there are multiple components in the measurement sample, the FID signal is the sum of the response signals of each component. If there is a difference in the mobility of each component, the decay rate of the response signal is different and the spin-spin relaxation time T2 is different. Therefore, these can be separated to obtain the relaxation time T2 and the component ratio R of each component. The smaller the mobility of the component, the shorter the relaxation time T2, and the larger the mobility, the longer the relaxation time T2. In other words, the shorter the relaxation time T2, the larger the crystallinity, and the longer the relaxation time T2, the larger the amorphousness.

[0036] As shown in Fig. 1, the FID signal obtained by pulse NMR of the polyurethane resin is shown by a curve. From this curve, by subtracting in order from the component with a long relaxation time T2 by the least squares method and performing waveform separation, as shown in Fig. 2, it can be divided into three components shown by three curves respectively. The component with a long relaxation time T2 shown by the solid line curve corresponds to the amorphous phase, and the component with a short relaxation time T2 shown by the broken line curve corresponds to the crystalline phase. The component shown by the dotted line curve corresponds to the interface phase. As described above, in the polyurethane resin, the component ratio of the amorphous phase formed by the soft segment with large mobility correlates with the physical properties of flexibility and stretchability, and the component ratio of the crystalline phase formed by the hard segment with small mobility correlates with hardness and strength. Therefore, increasing the component ratio of the amorphous phase can increase flexibility and stretchability, and increasing the component ratio of the crystalline phase can increase hardness and strength.

[0037] In pulse NMR, for each component, an intensity factor (a ｉ ) and a relaxation time (t ｉ (tau ｉ )) can be measured. From the intensity factor (a ｉ ) of each component, the ratio (%) of the intensity factor can be calculated. The larger the intensity factor (a ｉ ), the larger the amount of that component. The relaxation time (t ｉThe larger the value of the component, the higher its mobility. The strength factor (a) of each component is compared between different samples. ｉ By comparing the size of the particles, the degree of crystallinity can be determined. The pulsed NMR of the polished layer (or polyurethane resin) can be measured based on the procedure and method described in [Examples] below.

[0038] The polishing pad of this embodiment may be a polishing pad manufactured by the method described in "2. Method for Manufacturing a Polishing Pad" below. Alternatively, the polishing pad of this embodiment may be a soft polyurethane polishing pad as described later in "2. Method for Manufacturing a Polishing Pad".

[0039] 2. Method for Manufacturing an Abrasive Pad The method for manufacturing an abrasive pad of the present invention is the method for manufacturing an abrasive pad described in "1. Abrasive Pad" above, and includes a step of using a wet film formation method. Each component of the abrasive pad in the method for manufacturing an abrasive pad may be the same as each component described in "1. Abrasive Pad" above.

[0040] Polishing pads with a polyurethane resin polishing layer include polishing pads with a hard polyurethane resin polishing layer (hard polyurethane polishing pads) and polishing pads with a soft polyurethane resin polishing layer (soft polyurethane polishing pads). Hard polyurethane polishing pads are used for rough polishing, while soft polyurethane polishing pads are used for finish polishing. Soft polyurethane polishing pads have a texture similar to suede (napped leather). A wet film formation method is generally used to manufacture soft polyurethane polishing pads, in which a resin solution obtained by dissolving polyurethane resin in a polar solvent such as DMF (N,N-dimethylformamide) is applied to a substrate, and then the substrate is immersed in an aqueous coagulation solution. The manufacturing method of the polishing pad in this embodiment relates to the wet film formation method described above.

[0041] Polishing pads can be manufactured by a wet film formation method, for example, a method that includes at least one or all of the following steps: (1) preparing a polyurethane resin solution by mixing and dispersing a polyurethane resin, a polar solvent, and a low molecular weight polyol; (2) applying the polyurethane resin solution to a substrate; and (3) immersing the substrate coated with the polyurethane resin solution in a solidification solution for the solidification and regeneration of the polyurethane resin.

[0042] (1) Step of preparing a polyurethane resin solution The polyurethane resin can be the polyurethane resin described in "1 Polishing pad" above. The concentration (solid content concentration) of the polyurethane resin in the polyurethane resin solution is not particularly limited, but for example it is 10 to 50% by mass, preferably 15 to 50% by mass, more preferably 20 to 40% by mass, and most preferably 25 to 35% by mass. Within this concentration range, the sheet density can be adjusted to an appropriate range and a desired foam structure can be formed.

[0043] The polar solvent is not particularly limited, but may include or consist of DMF, DMAc, THF, DMSO, NMP, acetone, or a mixture of two or more of these. Of these, DMF is preferred from the viewpoint of excellent solubility of polyurethane resin. When DMF is used, since DMF, which is a good solvent for polyurethane resin, can be mixed with water in any ratio, the substitution rate with the coagulation solution (water) is fast, and the DMF on the lower layer (substrate side) of the polyurethane resin solution quickly moves to the upper layer (surface layer), making it easy to form relatively large bubbles (elongated vertically in the sheet thickness direction) on the lower layer side. This makes it possible to form roughly teardrop-shaped bubbles in the polished layer. The concentration of the polar solvent is not particularly limited, but is preferably 50 to 85% by mass, more preferably 60 to 80% by mass, and most preferably 65 to 75% by mass.

[0044] The low molecular weight polyol to be mixed and dispersed in the polyurethane resin can be the low molecular weight polyol described in "1. Polishing Pad" above. The concentration of the low molecular weight polyol in the polyurethane resin solution is not particularly limited, but is preferably 0.1 to 10% by mass, more preferably 1 to 5% by mass, and most preferably 2 to 4% by mass.

[0045] The polyurethane resin solution may further contain the nucleating agent and / or film-forming aid described in "1. Polishing Pad" above. As described above, the nucleating agent has the effect of suppressing the elution of hydrophilic additives such as low molecular weight polyols into the water bath and retaining the hydrophilic additives in the polyurethane resin (in the polishing layer). The film-forming aid also has the effect of improving the film-forming properties of the polyurethane resin solution.

[0046] The concentration of the nucleating agent in the polyurethane resin solution is not particularly limited, but is preferably 0.05 to 5% by mass, more preferably 0.5 to 3% by mass, and most preferably 0.1 to 2% by mass. The concentration of the film-forming aid in the polyurethane resin solution is not particularly limited, but is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, and most preferably 1 to 10% by mass.

[0047] The polyurethane resin solution may contain water as needed. The polyurethane resin solution may also contain additives as needed. While not particularly limited, examples of additives include pigments such as carbon black.

[0048] (2) Polyurethane resin solution coating process The substrate used in the polyurethane resin solution coating process can be any flexible material, such as plastic film (e.g., polyester film, polyolefin film, etc.) or nonwoven fabric. There are no particular limitations on the method of coating the polyurethane resin-containing solution onto the substrate, and for example, a conventional coater (knife coater, reverse coater, roll coater, etc.) can be used for coating. The coating thickness is, for example, 0.5 to 2.5 mm, preferably 1.0 to 2.0 mm, and more preferably 1.2 to 1.8 mm, from the standpoint of forming a predetermined foam structure.

[0049] (3) Coagulation and regeneration process of polyurethane resin In the coagulation and regeneration process of polyurethane resin, the coagulation solution into which the substrate coated with the polyurethane resin solution is immersed mainly consists of a poor solvent for polyurethane resin (water, etc.). Examples of coagulation solutions include water, a mixed solution of water and a polar solvent (e.g., DMF, DMAc, THF, DMSO, NMP, acetone, etc.). The concentration of the polar solvent in the mixed solution is preferably 0.5 to 30% by mass.

[0050] A polyurethane foam sheet solidified on a substrate is obtained through a polyurethane resin solidification and regeneration process.

[0051] (4) Washing and drying process of polyurethane resin The method for manufacturing the polishing pad of this embodiment may further include a step of washing and drying the polyurethane foam sheet obtained by solidification on the substrate, after peeling it off the substrate as necessary. Washing and drying remove any polar solvent and solidification liquid (water) remaining in the polyurethane resin. Water is usually used as the washing solution. Drying is usually carried out at 80 to 150°C for about 5 to 60 minutes.

[0052] The method for manufacturing the polishing pad of this embodiment may further include a step of grinding the surface or both the surface and the back surface; and / or a step of surface treatment of grooving by cutting and / or embossing.

[0053] The grinding (buffing) method is not particularly limited, and for example, a method using sandpaper can be used. The surface to be ground (buffed) may be either the polished surface (surface layer side) or the non-polished surface (surface attached to the surface plate), or both. The amount of grinding (buffing) is, for example, 0.05 to 0.3 mm, preferably 0.1 to 0.2 mm, depending on the desired surface shape. This creates pores in the polyurethane foam and pores in the porous microparticles on the surface layer of the polishing pad, and also makes the thickness of the sheet uniform.

[0054] In grooving and embossing, the processing temperature and processing pressure are not particularly limited, but the processing temperature is, for example, 100 to 200°C, preferably 120 to 180°C, and the processing pressure is, for example, 3 to 6 MPa, preferably 4 to 5 MPa. The processing time is also not particularly limited, but for example, 30 to 300 seconds, preferably 60 to 180 seconds.

[0055] The recesses formed by grooving or embossing may be formed randomly, or they may be formed regularly (for example, in a grid, concentric, radial, or honeycomb pattern). The width of the recesses is, for example, 0.3 to 3.0 mm, preferably 0.5 to 1.5 mm, and more preferably 0.8 to 1.2 mm. The average distance between the centers of adjacent recesses is, for example, 1 to 100 mm, preferably 2 to 20 mm. This promotes the supply and discharge of slurry to the surface layer side of the polishing pad.

[0056] A polishing pad can be manufactured by attaching the aforementioned support member to the polishing layer obtained in the manner described above, on the side opposite to the polishing surface (the bottom side).

[0057] 3. Method for polishing the surface of an optical material or semiconductor material The method for polishing the surface of an optical material or semiconductor material of the present invention includes the step of using the polishing pad described in "1. Polishing Pad" above. Each component of the polishing pad in the above polishing method may be the same as each component described in "1. Polishing Pad" above.

[0058] The optical material or semiconductor material to be polished is not particularly limited, but devices in which an oxide layer, a metal layer, or the like is formed on a semiconductor wafer are particularly preferred. The process of using the polishing pad described above may further include a step of finishing polishing the optical material or semiconductor material.

[0059] The process of using the polishing pad described above may further include a process of using an abrasive (polishing slurry). As mentioned above, it is presumed that the low molecular weight polyols that have entered between the hard segments of the polishing layer readily attract the polishing slurry, thereby enabling the polishing pad to exhibit sufficient polishing performance in the initial stages of polishing.

[0060] It is preferable that the polishing slurry contains abrasive particles. The liquid component in the polishing slurry is not particularly limited, but examples include water, acid, alkali, polar solvent, etc., and is selected depending on the material of the object to be polished and the desired polishing conditions. The abrasive component in the polishing slurry is not particularly limited, but examples include silica, zirconium silicate, cerium oxide, aluminum oxide, manganese oxide, etc. The polishing slurry may also contain other components such as organic substances soluble in the liquid component or pH adjusters.

[0061] The present invention will be experimentally explained by the following examples, but the following explanation is not intended to be interpreted as limiting the scope of the present invention to these examples.

[0062] 1. Preparation of polishing pads (Materials) The materials used in Examples 1 to 5 and Comparative Examples 1 to 3 described below are listed below.

[0063] • Polyurethane resin: Polyurethane resin (1)... Solution of polyester polyurethane resin (solid content concentration 30% by mass, 100% resin modulus of polyester polyurethane resin: 5.9 MPa) *The above polyester polyurethane resin is obtained by condensing a polyester polyol obtained by dehydrating and condensing 1,4-butanediol and adipic acid (used without distillation treatment, containing 12.9 mol% of low molecular weight diol component), a chain extender in a 1,4-butanediol / trimethylolpropane = 60 / 40 molar ratio, and 4,4'-diphenylmethane diisocyanate (MDI).

[0064] • Solvent: DMF...N,N-dimethylformamide

[0065] • Film-forming aids: Film-forming aid (1)...Paraffin-based surfactant Film-forming aid (2)...Copolymer of ethylene oxide and propylene oxide

[0066] • Nucleating agent: Nucleating agent (1) ... Cellulose acetate (viscosity-average degree of polymerization 120, degree of substitution 2.41)

[0067] • Low molecular weight polyols: Low molecular weight polyol (1) ... DEG (diethylene glycol)

[0068] In this embodiment, the 100% resin modulus refers to the value obtained by dividing the load applied when a non-foamed resin sheet is stretched to 100% (stretched to twice its original length) by its cross-sectional area. The 100% resin modulus was determined by thinly spreading a resin solution, drying it with hot air to produce a dry film with a thickness of approximately 200 μm, curing it for a while, punching out a dumbbell-shaped sample with a total length of 90 mm, a width of 20 mm at both ends, a distance of 50 mm between the grips, a parallel section width of 10 mm, and a thickness of 200 μm. The sample was then clamped in the upper and lower air chucks of a Tensilon universal material tester (Tensilon universal tester "RTC-1210" manufactured by A&D Co., Ltd.), and pulled at a pulling speed of 100 mm / min in an atmosphere of 20°C (±2°C) and 65% humidity (±5%), and the tension at 100% elongation (twice the original length) was determined by dividing the tension by the initial cross-sectional area of ​​the sample.

[0069] (Example 1) 100 parts by mass of the polyurethane resin (1) (30 parts by mass as solids), 2 parts by mass of the crystal nucleating agent (1), and 5 parts by mass of the low molecular weight polyol (1) were mixed to obtain a resin-containing solution. Other solvents (DMF), water, film-forming aid (1), and film-forming aid (2) were added as appropriate according to the film-forming properties of the resin. Table 1 shows the composition of each component.

[0070] Next, a PET film was prepared as a substrate for film formation. The resin-containing solution was applied to it to a thickness of 1.0 mm using a knife coater, and the solution was immersed in a solidification bath (solidification liquid: water) to solidify. After solidification, the resin-containing solution was washed and dried, and then peeled off the PET film to obtain a resin film (thickness 1.0 mm). The skin layer formed on the surface of the obtained resin film was ground (grinding amount: 200 μm). Subsequently, a PET substrate was bonded to the back surface of the ground surface of the resin film (polished layer) via double-sided tape to obtain a laminate of the resin film (polished layer) and the PET substrate. The surface of the resin film (polished layer) in the obtained laminate (ground surface) was embossed using a grid-shaped mold, and double-sided tape with release paper for fixing to a polishing platen was bonded to the surface of the PET substrate in the laminate (the surface that has not been ground or embossed) to obtain a polishing pad.

[0071] (Example 2) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the water described above was not added and no water was used. Then, using the resin-containing solution, a resin film was formed, a grinding process was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Example 2.

[0072] (Example 3) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the amount of the low molecular weight polyol (1) added was changed from 5 parts by mass to 6 parts by mass. Then, using the resin-containing solution, a resin film was formed, a grinding process was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Example 3.

[0073] (Example 4) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the water described above was not added, the amount of the crystal nucleating agent (1) was changed from 2 parts by mass to 3 parts by mass, and the amount of the low molecular weight polyol (1) was changed from 5 parts by mass to 6 parts by mass. Then, using the resin-containing solution, a resin film was formed, a grinding process was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Example 4.

[0074] (Example 5) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the water described above was not added and the amount of low molecular weight polyol (1) added was changed from 5 parts by mass to 6 parts by mass. Then, using the resin-containing solution, a resin film was formed, a grinding process was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Example 5.

[0075] (Comparative Example 1) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the above film-forming aid (1), above film-forming aid (2), above 2 parts by mass of crystal nucleating agent (1), and above 5 parts by mass of low molecular weight polyol (1) were not added and these components were not used. Then, using the above resin-containing solution, a resin film was formed, a grinding treatment was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Comparative Example 1.

[0076] (Comparative Example 2) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the amount of water added was changed from 5 parts by mass to 2 parts by mass, and 5 parts by mass of the low molecular weight polyol (1) from Example 1 was not added, and the low molecular weight polyol (1) was not used. Then, using the resin-containing solution, a resin film was formed, a grinding treatment was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Comparative Example 2.

[0077] (Comparative Example 3) As shown in Table 1, a resin-containing solution was obtained in the same manner as in Example 1, except that the water described above was not added and the amount of low molecular weight polyol (1) added was changed from 5 parts by mass to 10 parts by mass. Then, using the resin-containing solution, a resin film was formed, a grinding process was performed, a PET substrate was bonded, and embossing was performed in the same manner as in Example 1 to obtain the polishing pad of Comparative Example 3.

[0078]

[0079] Figures 3 to 5 show cross-sectional images taken with a scanning electron microscope (JEOL Ltd., JSM-5000LV) of each polishing pad obtained in Example 1 and Comparative Examples 1 and 2. Figure 3 is a cross-sectional image of the polishing pad of Example 1, measured at 50x magnification. Figure 4 is a cross-sectional image of the polishing pad of Comparative Example 1, measured at 50x magnification. Figure 5 is a cross-sectional image of the polishing pad of Comparative Example 2, measured at 50x magnification.

[0080] From the cross-sectional photographs in Figures 3 to 5, it was confirmed that the polishing layer of each polishing pad in Example 1 and Comparative Examples 1 and 2 contained roughly teardrop-shaped bubbles. Furthermore, the images of the cross-sectional photographs in Figures 3 to 5 were processed using image processing software (Image Analyzer V20LAB Ver. 1.3) to measure the average pore diameter of the bubbles. As a result, the average pore diameter of the bubbles in the polishing layer of each polishing pad in Example 1 and Comparative Examples 1 and 2 was 30 to 60 μm.

[0081] 2. Measurement of Low Molecular Weight Polyol Content The low molecular weight polyol content was measured for each resin film obtained in Examples 1 to 5 and Comparative Examples 1 to 3 (before polishing) based on the following procedure and method.

[0082] A portion (approximately 270 mg) was taken from the center of each resin film and transferred to a vial, and the weight of the portion of resin film was measured. 3 mL of ethanol was added to the vial containing the portion of resin film. The vial containing the portion of resin film and ethanol was placed on a hot plate (set to 70°C) and left to stand for 6 hours to extract the low molecular weight polyol with ethanol. This series of operations, from taking the resin film to extracting the low molecular weight polyol with ethanol, was repeated three times, yielding a total of approximately 9 mL of extract. The obtained extract was diluted to 10 mL by adding ethanol, and then diluted with acetone (HPLC grade, with a small amount of tetradecane added (an amount that is somewhat close to the peak size of the target compound)) (extract:acetone = 2:1 (volume ratio)) to obtain the measurement sample. The prepared measurement sample was measured by gas chromatography-mass spectrometry to quantify the low molecular weight polyol (mg). Then, based on the weight (g) of the resin film used (corresponding to the polishing layer) and the weight (mg) of the low molecular weight polyol, the ratio of the mass (mg) of the low molecular weight polyol to the mass (g) of the polishing layer (mass of low molecular weight polyol (mg) / mass (g) of the polishing layer) was calculated. The calculation results are shown in Table 3.

[0083] The ion chromatograms of the measurement samples for Example 1 and Comparative Example 1 obtained by the above measurements are shown in Figures 6 and 7, respectively (Figure 6: Example 1, Figure 7: Comparative Example 1). The portion indicated by A in Figures 6 and 7 corresponds to diethylene glycol, which is a low molecular weight polyol (1). An internal standard method (internal standard: tetradecane) was applied during the above measurements. The measurement conditions are shown below.

[0084] [Equipment] Gas chromatograph mass spectrometer: GC / MS-QP2020 NX (Shimadzu Corporation) Sample injection device: AOC-20i Plus (Shimadzu Corporation) [Gas chromatograph conditions] Carrier gas: Helium Column: DB-WAXetr (inner diameter 0.25 mm, length 30 m, film thickness 0.25 μm) Linear velocity: 36.1 cm / sec Sample injection volume: 1 μL Gas chromatograph inlet temperature: 250 °C Split ratio: 1:20 Column oven temperature program: The heating conditions are shown in Table 2 below.

[0085]

[0086] [Mass Spectrometry Conditions] Ionization Method: Electron Ionization Mass Spectrometry Interface Temperature: 220°C Scan Range: m / z 29–350 Detection Start Time: 5 minutes after sample introduction

[0087]

[0088] As shown in Table 3, in each polishing pad of Examples 1 to 5 and Comparative Example 3, the ratio of the mass (mg) of diethylene glycol, a low molecular weight polyol, to the mass (g) of the polishing layer was 0.12 to 8.10 mg / g. This result indicates that diethylene glycol remains in the polishing layer even after processes such as wet film formation. On the other hand, in each polishing pad of Comparative Examples 1 and 2, the ratio of diethylene glycol was 4.0 μg / g (0.004 mg / g) and 0.03 mg / g, respectively. This ratio is very small, and it is thought that the diethylene glycol detected originated from the raw materials of the polyurethane resin.

[0089] 3. Measurement of pulsed NMR The following pulsed NMR measurements were performed on each of the polishing pads in Example 1 and Comparative Examples 1 and 2 described above.

[0090] (1) Initial pulsed NMR Structural analysis of each polishing pad was performed by pulsed NMR under the following conditions.

[0091]

[0092] Under the above apparatus and conditions, the land portion of the embossed polishing pad was cut out with a cutter, and four 20 mm x 10 mm rectangular sample pieces were packed into a 10 mmφ sample tube. Pulse NMR measurements were then performed to obtain a decay curve. The obtained decay curve and the fitting curve were analyzed using the least squares method with the Lorentz function (linear portion) and the Gaussian function (curved portion) to determine the intensity factors (a) of the crystalline phase, interface phase, and amorphous phase in the polishing layer. ｉ The ratio (%) of the intensity factor was obtained. Fitting and analysis were performed using the software attached to the above-mentioned measuring device.

[0093] The measurement results are shown in Tables 5 and 6, and their graphs are shown in Figures 8 and 9 (Table 5 and Figure 8: Intensity Factor (a ｉ ), Table 6 and Figure 9: Percentage of intensity factors (%).

[0094] (2) Pulse NMR over time Abrasion tests were performed using each polishing pad at each test time (0 minutes, 5 minutes, 15 minutes, 30 minutes, 60 minutes, 90 minutes, or 120 minutes) based on the following [wear test conditions]. A new polishing pad was used for each test time.

[0095] A schematic diagram of the abrasion test is shown in Figure 10. Figure 10 shows the entire single-sided polishing machine 100, where 10 is the polishing pad, 20 is the dresser, 30 is the rotating platen, and 40 is the slurry. In the abrasion test, the dresser is set to contact and wear down the entire radius of the polishing pad. After each test time, an arbitrary portion of the part of the polishing pad that the center of the dresser contacted (circumference) was cut out with a cutter, and four rectangular sample pieces measuring 20 mm x 10 mm were placed in a 10 mmφ sample tube in the same manner as in (1) above, and pulse NMR measurements were performed.

[0096] Intensity factor (a ｉ The measurement results of the intensity factor (a) are shown in Table 7. ｉ Figures 11-13 show graphs of the measurement results of the relaxation time (t). Figures 11-13 are graphs for Example 1 and Comparative Examples 1 and 2, respectively. ｉ (Tau ｉThe measurement results are shown in Table 8. The relaxation time measurement results are shown in graphs (logarithmic scale on the vertical axis) in Figures 14 to 16. Figures 14 to 16 are graphs for Example 1 and Comparative Examples 1 and 2, respectively. The test time in this wear test is assumed to be the time from the start of polishing when actually polishing an object using a polishing pad. Therefore, the observation by pulse NMR in this wear test observes the change in the state of the polishing pad from the start of polishing.

[0097] [Abrasion Test Conditions] Polishing machine used: Speedfam, product name "FAM-12BS" Plate rotation speed (polishing pad rotation speed): 30 rpm Flow rate: 80 mL / min (polishing slurry) Polishing slurry is dropped from the rotation center of the polishing pad Polishing slurry: Colloidal silica slurry (pH: 11.5, a mixture of colloidal silica stock solution (silica concentration 14-16 wt%) and water = 1:3 (mass ratio) is used) Dresser: 3M diamond dresser, model number "A188" Dresser shape: 100 mmφ disc Dresser rotation speed: 30 rpm Dresser position: The center of rotation of the dresser is 105 mm away from the rotation center of the polishing pad in the outer direction Dressing pressure: 10 N Dresser rotation direction: Rotate in the same direction as the polishing pad. Test duration: 0 minutes, 5 minutes, 15 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes.

[0098]

[0099]

[0100]

[0101]

[0102] From the results in Tables 5 and 6 and Figures 8 and 9, it was found that Example 1 and Comparative Example 2, in which cellulose acetate, a crystal nucleating agent, was added, had a lower proportion of crystalline phase components and a higher proportion of amorphous phase components compared to Comparative Example 1, in which the crystal nucleating agent was not added. This is thought to be because the addition of the crystal nucleating agent increases the rate at which the polyurethane resin precipitates during wet film formation, shortening the time for the crystalline phase components to grow. Thus, since Example 1 and Comparative Example 2 have a lower proportion of crystalline phase components and a higher proportion of amorphous phase components compared to Comparative Example 1, it can be said that the mobility of the polyurethane resin is improved.

[0103] Furthermore, from the results in Tables 7 and 8 and the graphs in Figures 11 to 16, the polishing pads of Example 1 and Comparative Example 2 maintained high values ​​for the intensity factor and relaxation time of the amorphous phase component, which is a highly mobile component, from the beginning to the end of the test. This indicates that the polishing pads of Example 1 and Comparative Example 2 had high mobility of the polyurethane resin from the beginning of the test and maintained high mobility thereafter. It is presumed that such polishing pads will also have high initial polishing performance when actually polishing the workpiece. On the other hand, the polishing pad of Comparative Example 1 had a very low intensity factor of the amorphous phase component, which is a highly mobile component, at the start of the test, and the intensity factor of the amorphous phase component increased after about 5 minutes from the start of the test, after which it tended to stabilize. In addition, the polishing pad of Comparative Example 1 had a very high relaxation time of the amorphous phase component, which is a highly mobile component, at the start of the test, and the relaxation time of the amorphous phase component decreased after about 5 minutes from the start of the test, after which it tended to stabilize. These results indicate that the polyurethane resin in the polishing pad of Comparative Example 1 had low mobility at the beginning of the test, and its mobility increased after the test started. It is presumed that such a polishing pad will also have poor initial polishing performance when actually polishing the workpiece.

[0104] 4. Measurement of Polishing Rate The polishing rates were measured for each polishing pad in Examples 1 to 5 and Comparative Examples 1 to 3 as shown below. In the polishing of the TEOS film in this measurement, the polishing rate is important because the TEOS film is an insulating film and it is necessary to quickly remove excess film thickness. On the other hand, in the polishing of the Cu film in "5. Measurement of Scratches" described later, since the Cu film has fine wiring attached to it, scratch suppression is more important in processes where a soft polyurethane polishing pad is used.

[0105] For each polishing pad, polishing was performed under the conditions described in [Polishing Conditions] below, and the polishing rate was measured and evaluated, yielding the results in Table 9. When using the polishing pads, the pads were mounted on the polishing platen of the polishing machine so that the polishing surface of the polishing layer faced the workpiece. Then, while supplying slurry to the polishing surface of the polishing pad, the polishing platen was rotated to polish the processed surface of the workpiece.

[0106] The substrates used for polishing were 12-inch silicon wafers on which tetraethoxysilane was deposited by CVD to create an insulating film with a thickness of 1 μm (uniformity (CV%) of 13%). 600 substrates were polished sequentially.

[0107] The polishing rate is expressed as the amount of polishing per minute in terms of thickness (Å). For each number of polished substrates, the thickness of the insulating film of the substrate was measured at 121 locations before and after polishing, and the average of these 121 thicknesses was calculated. The polishing rate was calculated from this average value and was defined as the polishing rate (Å / min) for each number of polished substrates. The above thickness measurements were taken using the DBS mode of an optical film thickness and quality analyzer (KLA-Tencor, ASET-F5x).

[0108] The measurement results are shown in Table 9, and the measurement results are shown as graphs in Figures 17 and 18. In the above measurements, if the polishing rate is 210 Å / min or higher after 50 sheets of processing, it can be said that the polishing performance is high. Furthermore, if the polishing rate reaches 210 Å / min or higher by the time 50 sheets of processing are processed, it can be said that the polishing start-up is excellent.

[0109] As will be described later, the polishing pad of Comparative Example 2 showed a tendency to stabilize at a low polishing rate, so the measurement was stopped after polishing 200 substrates, and no further measurements of the polishing rate were performed.

[0110] [Polishing Conditions] Polishing machine: EBARA F-REX300X Disk: A189L (manufactured by 3M) Slurry: Colloidal silica slurry (pH: 11.5, a mixture of colloidal silica stock solution (silica concentration 14-16 wt%) and water = 1:3 (mass ratio), to which 1.0 wt% hydrogen peroxide solution was added) Workpiece: 300 mmφ SiO ２ (TEOS) Pad diameter: 740 mmφ Pad break: 30 N x 30 minutes, platen rotation speed 80 rpm Conditioning: Ex-situ, 30 N, 4 scans Ultrapure water: 800 mL / min Polishing: Platen rotation speed 70 rpm, slurry flow rate 200 mL / min, polishing time 60 seconds, polishing pressure: 2.05 g / cm ２ Number of sheets processed: 600

[0111]

[0112] As shown in Table 3 above, Examples 1 to 5 relate to polishing pads in which the ratio of the mass (mg) of low molecular weight polyol to the mass (g) of the polishing layer is 0.1 to 8.0 mg / g. Comparative Examples 1 and 2 relate to polishing pads in which the above ratio is less than 0.1 mg / g. Comparative Example 3 relates to a polishing pad in which the above ratio is greater than 8.0 mg / g.

[0113] From the results in Table 9 and Figures 17 and 18, it was found that the polishing pads of Examples 1, 2, 4, and 5 showed a high polishing rate of 210 Å / min or more after polishing 10 plates, and maintained a high polishing rate of 215 Å / min or more thereafter. In particular, the polishing pads of Examples 4 and 5 showed an extremely high polishing rate of 240 Å / min or more after polishing 10 plates, and maintained an extremely high polishing rate of 250 Å / min or more thereafter. Furthermore, the polishing pads of Example 3 and Comparative Example 3 showed a high polishing rate of 210 Å / min or more after polishing 20 plates, and maintained a high polishing rate of 210 Å / min or more thereafter. The polishing pads of Examples 1 to 5 and Comparative Example 3 showed good initial polishing performance, and this result is in good agreement with the results of the pulse NMR over time described above.

[0114] On the other hand, the polishing pad of Comparative Example 1 did not show a significant increase in polishing rate even after a considerable amount of time had passed since the start of polishing, finally reaching a polishing rate of 230 Å / min after polishing 300 sheets. The polishing pad of Comparative Example 1 had poor start-up of polishing performance, and this result is in good agreement with the results of the pulsed NMR over time described above.

[0115] Furthermore, for the polishing pad of Comparative Example 2, a tendency was observed for the polishing rate to stabilize at a low level of less than 200 Å / min. Therefore, measurements were stopped after polishing 200 substrates, and no further measurements of the polishing rate were performed. As described above, the polishing pad of Comparative Example 2 showed similar pulse NMR results to the polishing pad of Example 1, but unlike Example 1, no low molecular weight polyol was added. From a comparison of the results of Examples 1 to 5 and Comparative Example 3 with the results of Comparative Example 2, it was found that the addition of low molecular weight polyol is effective in achieving a high polishing rate.

[0116] 5. Measurement of Scratches The following scratch measurements were performed on each of the polishing pads in Examples 1 to 5 and Comparative Examples 1 and 3. Note that for the polishing pad of Comparative Example 2, the polishing rate was low in the test described in "4. Measurement of Polishing Rate" above, so a polishing test on the Cu film substrate was not performed, and therefore the scratch measurement was not performed.

[0117] Scratch evaluation was performed by polishing a Cu film substrate based on the conditions described in the [Polishing Test] below. After polishing, the substrate was measured using a wafer surface inspection device (KLA-Tencor, Surfscan SP5, detection limit 110 nm) in high-sensitivity measurement mode to detect defects (surface defects) with a size of 110 nm or larger across the entire substrate. For each detected defect, SEM images were taken using a review SEM and analyzed to classify them into "particles," "pad debris," and "scratches," and the number of scratches was counted. Here, "particles" refers to fine particles remaining on the surface of the object being polished, "pad debris" refers to debris of the polishing layer adhering to the surface of the object being polished, and "scratches" refers to scratches on the surface of the object being polished.

[0118] The measurement results are shown in Table 10, and the measurement results are shown as graphs in Figures 19 and 20. In the above measurements, if the number of scratches is 30 or less, it can be said that the scratches have been suppressed.

[0119] [Polishing Test] Polishing machine: EBARA F-REX300X Disk: A189L (manufactured by 3M) Slurry: Colloidal silica slurry (pH: 11.5, a mixture of colloidal silica stock solution (silica concentration 14-16 wt%) and water = 1:3 (mass ratio), with 1.0 wt% hydrogen peroxide added) Workpiece: 300 mmφ Cu film substrate Pad diameter: 740 mmφ Pad break: 30 N x 30 minutes, platen rotation speed 70 rpm Conditioning: Ex-situ, 30 N, 4 scans Ultrapure water: 800 mL / min Polishing: Platen rotation speed 80 rpm, slurry flow rate 200 mL / min, polishing time 60 seconds, polishing pressure: 2.05 g / cm ２ Number of sheets processed: 100

[0120]

[0121] From the results in Table 10 and Figures 19 and 20, it can be said that the polishing pads of Examples 1 to 5 produced fewer scratches at all processing counts, indicating that scratch suppression was achieved. In particular, the polishing pads of Examples 1 to 5 produced significantly fewer scratches in the initial stages of polishing (up to 16 processing counts) compared to the polishing pads of Comparative Examples 1 and 3, which will be described later. Furthermore, the polishing pad of Example 5 produced significantly fewer scratches at all processing counts, indicating even greater scratch suppression. The polishing layer in the polishing pads of Examples 1 to 5 contains 0.1 mg / g to 8.0 mg / g of low molecular weight polyol, which is presumed to allow the polishing slurry to adhere easily to the polishing pad. Therefore, it is thought that in the polishing pads of Examples 1 to 5, the polishing grains are quickly dispersed on the surface of the polishing pad, making it less likely for aggregated abrasive grains, which cause scratches, to form.

[0122] On the other hand, the polishing pad of Comparative Example 1 produced a large number of scratches at all processing counts, indicating that scratching was not suppressed. In particular, the number of scratches was very high in the initial stages of polishing (up to 16 processing counts). Similarly, the polishing pad of Comparative Example 3 produced a large number of scratches in the initial stages of polishing (up to 16 processing counts), especially up to 4 processing counts, indicating that scratching in the initial stages of polishing was not suppressed.

[0123] Based on the above results, it was confirmed that the polishing pad of the present invention can shorten the start-up processing time and suppress the occurrence of scratches in the initial stages of polishing.

Claims

1. A polishing pad having an abrasive layer, wherein the abrasive layer comprises a polyurethane resin and a low molecular weight polyol, has substantially teardrop-shaped bubbles, and the ratio of the mass (mg) of the low molecular weight polyol to the mass (g) of the abrasive layer is 0.1 mg / g or more and 8.0 mg / g or less.

2. The polishing pad according to claim 1, wherein no covalent bond is formed between the polyurethane resin and the low molecular weight polyol.

3. The polishing pad according to claim 1 or 2, wherein the low molecular weight polyol comprises diethylene glycol.

4. The polishing pad according to any one of claims 1 to 3, wherein the polishing layer further comprises a crystal nucleating agent.

5. The polishing pad according to claim 4, wherein the nucleating agent comprises a cellulose derivative.

6. A method for manufacturing an abrasive pad according to any one of claims 1 to 5, comprising the step of using a wet film formation method.

7. A method for polishing the surface of an optical material or a semiconductor material, comprising the step of using a polishing pad according to any one of claims 1 to 5.

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