Polishing pad and method for manufacturing the same

Abstract

To provide a polishing pad which has high stability of a temporal polishing rate, and excellent rise performance of the polishing rate, and a manufacturing method of the same.SOLUTION: A polishing pad includes a polyurethane resin sheet which is formed by a wet type film-forming method and includes a plurality of communication bubbles therein, as a polishing layer, wherein when abundance ratios of three components of a crystal phase, an intermediate phase and an amorphous phase, which are determined by a pulse NMR, are represented by A1, A2 and A3 (%), the polishing layer satisfies the following conditions: (i) a difference (A2wet-A2dry) of an intermediate phase component abundance ratio A2wet (%) when wetted to an intermediate phase component abundance ratio A2dry (%) when dried of -20% or more, and (ii) a difference (A3wet-A3dry) of an amorphous phase component abundance ratio A3wet (%) when wetted to an amorphous phase component abundance ratio A3dry (%) when dried and of 30% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polishing pad and a method for manufacturing the same. In particular, it relates to a polishing pad for polishing silicon, hard disks, mother glass for liquid crystal displays, and semiconductor devices, and a method for manufacturing the same.

Background Art

[0002] Since flatness is required for the surfaces of materials such as optical materials, semiconductor devices, hard disks, and glass substrates, free abrasive polishing using a polishing pad is performed. The free abrasive method is a method of polishing the processed surface of the workpiece while supplying a slurry (polishing liquid) containing abrasive grains between the polishing pad and the workpiece. Polishing pads used for polishing semiconductor devices and the like are highly required to have defect-free and planarization characteristics of the workpiece, and the use of soft polishing pads mainly in the finishing polishing process is increasing. In CMP technology, it is necessary to stabilize the polishing rate from the viewpoints of improving productivity efficiency and yield. In particular, since the polishing rate at the start of polishing is smaller than the polishing rate in the steady state, it is required to further shorten the time (start-up processing time) required for dummy polishing until the polishing rate becomes almost constant. To address the above problems, a soft polishing pad has been proposed (Patent Document 1) that reduces the start-up processing time by defining the average diameter of the openings in the nap layer of the polishing cloth and increasing the area of the non-opening wall portion compared to the area of the opening portion of the holes. In addition, a soft polishing pad has been proposed (Patent Document 2) that defines the ratio of the opening diameter of the bubbles opened on the surface of the nap layer to the distance from the surface to the deepest part of the bubbles opened on the surface, and by smoothly flowing in, holding, and discharging the polishing slurry into the bubbles opened during polishing, improves the polishing rate and obtains stable polishing characteristics, and shortens the start-up processing time to improve productivity.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2006-75914 [Patent Document 2] Japanese Patent Publication No. 2007-160474 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, with conventional soft abrasive pads, the polishing rate fluctuated as the workpiece was being polished, making it difficult to achieve a stable polishing rate. As a result, variations in the amount of material polished were likely to occur, making it difficult to maintain consistent product quality. In addition, conventional soft abrasive pads still required a considerable amount of time for the start-up process, and further reductions in this time were needed. The present invention has been made in view of the above problems, and aims to provide a polishing pad and a method for manufacturing the same that can continuously polish an object to be polished at a stable polishing rate. Furthermore, the present invention aims to provide a polishing pad and a method for manufacturing the same that can eliminate or minimize the start-up time. The present invention also aims to provide a polishing pad and a method for manufacturing the same that have a short start-up time and a relatively high polishing rate. [Means for solving the problem]

[0005] As a result of diligent research, the inventors of the present invention have discovered that among the three components of the crystalline phase, intermediate phase, and amorphous phase determined by pulsed NMR spectroscopy, a polishing pad in which the difference between the dry and wet states of the intermediate phase and amorphous phase is relatively small can polish non-polished materials with a short start-up time and a stable polishing rate, thereby completing the present invention. The present invention includes the following embodiments. [1] A polishing pad comprising a polyurethane resin sheet formed by a wet film deposition method and containing multiple interconnected air bubbles as an polishing layer, The polished layer is separated into three components—crystalline phase, intermediate phase, and amorphous phase—by subtracting the components with the longest spin-spin relaxation time T2 from the free induction decay signal (FID) obtained by pulsed NMR using the least squares method, and then separating the waveforms. The relative abundances of each phase are A1, A2, and A3 (%), respectively, under the following conditions: (i) The difference between the ratio of intermediate phase components in dry conditions A2dry(%) and the ratio of intermediate phase components in wet conditions A2wet(%) (A2wet-A2dry) is -20% or more. (ii) The difference between the ratio of amorphous components in dry state A3dry (%) and the ratio of amorphous components in wet state A3wet (%) (A3wet-A3dry) is 30% or less. (However, "dry" refers to conditions where the sample is kept in an environment of 25°C and 50% relative humidity for 48 hours, while "wet" refers to conditions where the sample is immersed in deionized water at 20±2°C for 10 minutes while the pressure is reduced using an aspirator.) A polishing pad that meets the requirements. [2] The polishing pad according to [1] above, characterized in that the abrasive layer has an amorphous relaxation time T2(3)wet when wet that is 6 to 15 times that of the amorphous relaxation time T2(3)dry when dry. [3] The polishing pad according to [1] above, wherein the polyurethane resin sheet comprises a polyurethane resin which is a cured product of a resin solution composition comprising at least a polyisocyanate compound (A) and a polyol compound (B), and the (B) polyol compound comprises ethylene glycol. [4] The polishing pad described in [1] above, wherein the thickness of the polyurethane resin sheet is in the range of 0.5 to 3.0 mm. [5] A step of applying a resin solution composition containing polyurethane resin, a non-polar oil, and a solvent to a film-forming substrate, and A process to form a wet-formed polyurethane resin sheet by immersing a film-forming substrate coated with the resin solution composition in a solidification solution and solidifying the resin solution composition, A method for manufacturing an abrasive pad according to any one of the above [1] to [4], including the above. [6] The method for manufacturing an abrasive pad according to [5] above, wherein the content of the non-polar oil is 1 to 10% by mass relative to the mass of the polyurethane resin in the resin solution composition. [Effects of the Invention]

[0006] According to the present invention, it is possible to obtain a polishing pad with high stability of the polishing rate. Furthermore, according to the present invention, it is possible to obtain a polishing pad with excellent performance in the rise of the polishing rate and a relatively high polishing rate. [Brief explanation of the drawing]

[0007] [Figure 1] This graph shows the change in the ratio of intermediate phase components A2wet(%) when wet compared to the ratio A2dry(%) when dry for polishing pads (polyurethane resin sheets) in the examples and comparative examples. [Figure 2] This graph shows the change in the amorphous component ratio A3wet(%) when wet compared to the amorphous component ratio A3dry(%) when dry for polishing pads (polyurethane resin sheets) of the examples and comparative examples. [Figure 3] This graph shows the change in amorphous phase relaxation time T2(3)wet when wet and amorphous phase relaxation time T2(3)dry when dry for polishing pads (polyurethane resin sheets) in the examples and comparative examples. [Figure 4] This is a cross-sectional photograph of the polishing pad (polyurethane resin sheet before the buffing process) from Example 1. Teardrop-shaped bubbles and microbubbles can be seen. [Figure 5] This graph shows the water contact angle (an indicator of wettability) measured for polishing pads (polyurethane resin sheets) in the examples and comparative examples. [Figure 6] This figure schematically shows the curve of the time-free induction decay signal measured by pulsed NMR, and the curves obtained when the waveform is separated into amorphous phase (L component), intermediate phase (M component), and crystalline phase (S component) using the least squares method based on the difference in spin-spin relaxation time. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments for carrying out the present invention will be described. [[Polishing Pad]] The polishing pad of the present invention is used for polishing optical materials, semiconductor wafers, semiconductor devices, substrates for hard disks, etc. In particular, it is suitably used for chemical mechanical polishing (CMP) of devices in which an oxide layer, a metal layer such as copper, etc. are formed on a semiconductor wafer. The polishing pad of the first aspect of the present invention is a polishing pad including a polyurethane resin sheet formed by a wet film-forming method. The polyurethane resin sheet formed by the wet film-forming method may contain a plurality of communicating air bubbles. The plurality of communicating air bubbles include teardrop-shaped bubbles and a plurality of substantially spherical microbubbles having a smaller size than the teardrop-shaped bubbles, and these are in communication with each other. (See FIG. 4). The polishing layer of the polishing pad of the first aspect of the present invention subtracts the free induction decay signal (FID) obtained by pulsed NMR from the component with a long spin-spin relaxation time T2 in order by the least squares method and separates the waveform, so that, in order from the longer spin-spin relaxation time T2, it is divided into three components of crystalline phase, mesophase, and amorphous phase, and when the abundance ratios of each phase are A1, A2, A3 (%) respectively, the following conditions: (i) The difference (A2wet - A2dry) between the mesophase component abundance ratio A2wet (%) during wetting and the mesophase component abundance ratio A2dry (%) during drying is -20% or more, (ii) The difference (A3wet - A3dry) between the amorphous phase component abundance ratio A3wet (%) during wetting and the amorphous phase component abundance ratio A3dry (%) during drying is 30% or less, (However, "during drying" is the condition of holding for 48 hours in an environment of temperature 25°C and relative humidity 50%, and "during wetting" is the condition of immersing in deionized water at 20 ± 2°C for 10 minutes while reducing the pressure with an aspirator.)

[0009] (Pulsed NMR) The measurement of pulsed NMR is carried out using a pulsed NMR measuring device, by the solid echo method, at 90° pulse 0.5 s, repetition time: 4 s, number of integrations: 128 times, and temperature: 40°C. Regarding the solid echo method, since it is already well-known, details are omitted here. It is mainly used for measuring samples with short relaxation times such as glassy and crystalline polymers. By a method that seemingly eliminates the dead time, in the 90°x-τ-90°y pulse method where two 90° pulses are applied with a 90° phase change, when a 90° pulse is applied in the X-axis direction, a free induction decay (FID) signal is observed after the dead time. When a second 90° pulse is applied in the y-axis direction at a time τ when the FID signal does not decay, an echo appears at t = 2τ when the magnetization directions align. The obtained echo can approximate the FID signal after the 90° pulse. Methods for analyzing the relationship between physical properties, phase separation structure, and composition from the analysis results of pulsed NMR are already well-known. By subtracting the free induction decay (FID) signal obtained by pulsed NMR from the long component of the spin-spin relaxation time T2 in order using the least squares method and performing waveform separation, it can be divided into three components. The component with a long relaxation time is defined as the component with high mobility and is the amorphous phase, the short component is the component with low mobility and is the crystalline phase, and the intermediate component is the intermediate phase (when it is difficult to separate the components of the intermediate phase and the amorphous phase, it is analyzed as the intermediate phase). Using calculation formulas based on Gaussian functions and Lorentzian functions, the component amounts (abundance ratios) of each component can be obtained (for example, refer to "Analysis of Phase Separation Structure of Polyurethane Resin by Solid NMR (High-Resolution NMR and Pulsed NMR)" (DIC Technical Review N.12, pp. 7 - 12, 2006)).

[0010] A detailed explanation of pulsed NMR measurements is as follows: First, a sample, consisting of pieces approximately 1-2 mm square packed to a height of 1-2 cm in a 1 cm diameter glass tube, is placed in a magnetic field. After applying a high-frequency pulsed magnetic field, the relaxation behavior of the macroscopic magnetization is measured, yielding a free induction decay (FID) signal as shown in Figure 6 (horizontal axis: time (μs), vertical axis: free induction decay signal). The initial value of the obtained FID signal is proportional to the number of protons in the sample. If the sample has three components, the FID signal appears as the sum of the response signals of the three components. On the other hand, since each component in the sample has different mobility, the rate of decay of the response signal differs among the components, resulting in different spin-spin relaxation times T2. Therefore, it can be separated into three components by the least squares method, and these become the amorphous phase, intermediate phase, and crystalline phase, respectively, in order from the longest spin-spin relaxation time T2 (see Figure 6). The amorphous phase is the component with high molecular mobility, the crystalline phase is the component with low molecular mobility, and the intermediate phase is the component in between. The following describes a more detailed fitting method (a method for separating into three components with different motility). Using the analysis software "TD-NMR Analyzer" manufactured by BRUKER, the obtained relaxation curve was fitted using the following calculation formula (1) according to the product manual, and the ratio of each component and the relaxation time were determined from the curves derived from the three components obtained by measurement. In this embodiment, the fitting was performed with the Weibull coefficients set to W(1)=2.0, W(2)=1.0, and W(3)=1.0, starting from the shortest relaxation time T2. Formula (1) JPEG0007850641000001.jpg31170

[0011] "Area of ​​each phase" refers to the proportion (%) of each phase present. In this document, the abundance ratios of the crystalline phase, intermediate phase, and amorphous phase are referred to as A1, A2, and A3 (%), respectively. Furthermore, in this specification, the abundance ratios under certain conditions in wet or dry states are distinguished by adding terms such as wet and dry, for example, A2wet (wet) and A2dry (dry). Generally, the lower the proportion of amorphous phase, the harder the urethane becomes. Also, the less intermediate phase there is, the clearer the phase separation between the crystalline and amorphous phases becomes, resulting in a structure that tends to have elastic properties that are less prone to distortion. Conversely, the more intermediate phase there is, the less clear the phase separation between the crystalline and amorphous phases becomes, resulting in a structure that tends to have delayed elastic properties. In this specification, "dry" refers to the condition of being held for 48 hours in an environment with a temperature of 25°C and a relative humidity of 50%, and "wet" refers to the condition of being immersed in deionized water at 20±2°C for 10 minutes while reducing the pressure with an aspirator in a bell jar (a condition in which water penetrates to the inside of the foam of the polishing layer). As mentioned above, 1 The spin-spin relaxation time T2 observed by H-pulse NMR decreases in the order of crystalline phase, intermediate phase, and amorphous phase. The intermediate phase has a faster relaxation time than the amorphous phase and is considered to be an amorphous phase with constrained mobility. When the slurry adheres to the polishing surface of the polishing pad, it is thought that water molecules bind to some of the molecular chains that were constrained as the intermediate phase, forming a highly mobile amorphous phase component. In this invention, by suppressing the decrease of intermediate phase component A2 when transitioning from a dry state to a wet state, it is possible to suppress the excessive increase of amorphous phase component A3 when transitioning from a dry state to a wet state, thereby obtaining polishing stability. If the difference in the relative abundance of intermediate phase component A2 between dry and wet states is -20% or more ((A2wet-A2dry)≧-20%) (i.e., the relative abundance of the intermediate phase tends to decrease in wet states compared to dry states, and is at most 20%), and the difference in the relative abundance of amorphous phase component A3 between dry and wet states is 30% or less ((A3wet-A3dry)≦30%) (i.e., the relative abundance of the crystalline phase tends to increase in wet states compared to dry states, and is at most 30%), then the amount of components that behave as soft segments in the pad will not increase excessively, preventing the polishing rate from becoming unstable or insufficient.

[0012] The difference between the ratio of intermediate phase components A2wet(%) in the wet state and the ratio of intermediate phase components A2dry(%) in the dry state (A2wet-A2dry) is preferably 0 to -20%, and more preferably less than 0 and 10% or more. The difference between the amorphous phase component abundance ratio A3wet(%) in the wet state and the amorphous phase component abundance ratio A3dry(%) in the dry state (A3wet-A3dry) is preferably 0-30%, more preferably 5-20% by mass, and even more preferably 10-15%.

[0013] (Spin-spin relaxation time T2) The "spin-spin relaxation time (T2)" is used as an indicator of molecular kineticity, with a higher value indicating greater kineticity. Generally, crystalline phases have low kineticity, resulting in a small T2 value, while amorphous phases have a high T2 value. The higher the molecular weight of the diol, the greater the kineticity and the larger the T2 value. The reason why the spin-spin relaxation time T2 is a measure of molecular kineticity can be understood from the relationship between the correlation time τc and T2. τc represents the average time it takes for molecules in a certain state of motion to undergo a molecular collision, and it is known that the value of T2 decreases inversely proportional to the increase in τc. This indicates that T2 shortens as molecular kineticity decreases. In this specification, the relaxation time T2 of the amorphous phase is also referred to as T2(3). Furthermore, in this specification, the relaxation time T2 of the amorphous phase under certain conditions in the wet or dry state is also referred to as T2(3)wet and T2(3)dry, respectively. The wet and dry conditions in this case are as follows: "Dry state" is the condition of being held for 48 hours in an environment of 25°C and 50% relative humidity, and "Wet state" is the condition of being immersed in deionized water at 20±2°C for 10 minutes while reducing the pressure with an aspirator in a bell jar (a sample in which water is immersed to the inside of the foam of the polished layer).

[0014] In the polished layer of the present invention, the amorphous phase relaxation time T2(3)wet in the wet state is preferably 6 to 15 times greater than the amorphous phase relaxation time T2(3)dry in the dry state. More preferably 7 to 13 times greater. When the slurry is in contact with the surface of the polishing pad, the polar molecules of the polishing pad material form hydrogen bonds with water molecules. The urethane resin component, which is strongly bound from the surrounding molecules by hydrogen bonding, can be identified by pulsed NMR measurement of target nuclei. 1 When measuring the free induction decay signal of H, the free induction decay signal changes rapidly, meaning the relaxation time is short. On the other hand, when there are many bonds between water molecules, the binding state is loose, resulting in high molecular mobility, and the free induction decay signal changes slowly, meaning the relaxation time is long. The polishing pad of the present invention can sufficiently increase the relaxation time of the amorphous phase component when it changes from a dry state to a wet state, and it is thought that the amount of bonding between the resin component, i.e., the soft segment and water, which is constrained by hydrogen bonding, can be suppressed, thereby suppressing the softening of the resin and leading to a stable polishing rate.

[0015] (Polyurethane resin sheet) (A) Polyisocyanate compounds In this specification, polyisocyanate compound (A) means a compound having two or more isocyanate groups in its molecule. The polyisocyanate compound (A) 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 aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, phenylene diisocyanate, and xylylene diisocyanate; and aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylylene diisocyanate. Further examples of aromatic diisocyanates, aliphatic or alicyclic diisocyanates 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'-biphenyl diisocyanate, and 3,3'-dimethyldi Examples include phenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, 1,6-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 ethylidine diisothiocyanate. Among these, the polyisocyanate compound (A) is preferably composed of diphenylmethane-4,4'-diisocyanate (MDI), 1,6-hexamethylene diisocyanate, and isophorone diisocyanate, and more preferably contains diphenylmethane-4,4'-diisocyanate (MDI), due to the favorable balance of the physical properties of the resulting polyurethane and its availability in large quantities at low cost for industrial purposes.

[0016] These polyisocyanate compounds (A) may be used individually or in combination of multiple polyisocyanate compounds.

[0017] (B) Polyol compounds In this specification, a polyurethane resin sheet can be obtained by reacting at least a polyisocyanate compound (A) with a polyol (B). Polyol compounds (B) refer to compounds that have two or more alcoholic hydroxyl groups (OH) in their molecule.

[0018] Examples of polymeric diols, such as polyol compounds (B), include polyether diols and polyester diols. These polymeric diols may be used individually or in combination of two or more.

[0019] In the present invention, it is preferable to use a hydrophilized diol compound. For example, a hydrophilized diol compound can be obtained by increasing the ratio of oxygen atoms to methylene groups in the diol compound, or by introducing a hydrophilic functional group. Specifically, for example, compared to a compound obtained by the reaction of adipic acid, a conventional polyester diol compound, with a polyol containing 1,4-butanediol or ethylene glycol, the hydrophilicity can be improved by increasing the molar ratio of ethylene glycol in the polyol. That is, since the number of methylene groups per repeating unit in the polyurethane resin is 4 in 1,4-butanediol and 2 in ethylene glycol, the ratio of oxygen atoms to methylene groups increases, thereby improving hydrophilicity. By reacting a hydrophilized diol compound with a polyvalent isocyanate compound, the resulting polyurethane resin becomes more hydrophilic. In other words, the higher the degree of hydrophilicity of the diol compound, the higher the hydrophilicity of the polyurethane resin. As a result, the resulting polyurethane resin sheet has increased affinity for slurry, improving its initial reaction time and polishing stability. The wettability of a polyurethane resin sheet resulting from the hydrophilization of a polyol compound may be evaluated by measuring the water contact angle of the polyurethane resin sheet.

[0020] Examples of polyetherdiols include poly(ethylene glycol), poly(propylene glycol), poly(tetramethylene glycol), and poly(methyltetramethylene glycol). These polyetherdiols may be used individually or in combination of two or more.

[0021] Polyester diols can be produced, for example, by directly esterifying or transesterifying a low-molecular-weight diol with an ester-forming derivative such as a dicarboxylic acid or its ester, or an anhydride. Examples of dicarboxylic acids that constitute polyester diols include aliphatic dicarboxylic acids with 4 to 12 carbon atoms, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanediic acid, and 3,7-dimethyldecanediic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and orthophthalic acid. These dicarboxylic acids may be used individually or in combination of two or more. Examples of low molecular weight diols that constitute polyester diols include aliphatic diols such as ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. These low molecular weight diols may be used individually or in combination of two or more. Examples of carbon number in low molecular weight diols include 6 to 12.

[0022] (C) Chain elongator The polyurethane resin used in the production of the polyurethane resin sheet of the present invention may further contain a chain extender (C) in addition to the above-mentioned (A) polyisocyanate compound and (B) polyol compound. The chain extender (C) is preferably added in an amount of 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 2 to 10 parts by mass, per 100 parts by mass of the polyol compound (B). Chain extender (C) may be a low molecular weight compound containing an active hydrogen group, such as aliphatic polyol compounds such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, saccharose, methylene glycol, glycerin, sorbitol, bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, hydro Aromatic polyol compounds such as quinones, ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,2-cyclohexanediamine, 1,4-cyclohexanediamine, aminoethylethanolamine, hydrazine, diamines such as diethylenetriamine and triethylenetetramine, amino alcohols, and water can be used. These chain extenders may be used alone or in combination of two or more.

[0023] (D) Other ingredients The resin solution composition for producing the polyurethane resin sheet of the present invention may further contain additives. The additives are preferably selected from the group consisting of film-forming aids, carbon black, and the like. Examples of film-forming aids include hydrophilic surfactants, hydrophobic surfactants, and cellulose derivatives. Examples of hydrophilic additives include anionic surfactants such as sodium lauryl sulfate, carboxylates, sulfonates, sulfate esters, and phosphate esters, and nonionic surfactants such as hydrophilic esters, ethers, ester-ethers, and amides. Examples of hydrophobic additives include nonionic surfactants, more specifically 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. Examples of cellulose derivatives include ester-based cellulose derivatives such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose valerate, and cellulose acetate butyrate, as well as ether-based cellulose derivatives such as ethylcellulose and hydroxypropylcellulose, and ether-ester-based cellulose derivatives such as acetylethylcellulose and acetoxypropylcellulose. When a film-forming aid is added as an additive, it is preferably in an amount of 0.1 to 10% by mass. Polyurethane resin sheets can be manufactured by polymerizing and curing (solidifying) the resin solution composition described above.

[0024] (E) Non-polar oil The polyurethane resin sheet of the present invention may further contain a non-polar oil, and it is preferable that it does. Non-polar oil refers to an oil composed only of carbon and hydrogen, and specifically includes C8-C16 isoalkane non-polar oils such as isodecane, isododecane, isohexadecane, and hydrogenated polyisobutene. In the present invention, the non-polar oil preferably has a mass-average molecular weight of 300-5000, and more preferably 500-3000. By using a non-polar oil, the size of multiple spherical microbubbles present in the resin wall portion between adjacent teardrop-shaped bubbles can be reduced and the number of microbubbles can be increased, improving the affinity to the polishing liquid even in the initial stages of polishing and increasing the strength of the resin wall. This improves the affinity to water while maintaining the rigidity of the pad, thereby improving the polishing rate. The non-polar oil content is preferably 1 to 10% by mass, and more preferably 2 to 7% by mass, relative to the mass (100% by mass) of the polyurethane resin sheet. If the blending amount is 1% by mass or more, the size of the relatively large number of spherical microbubbles present in the resin wall portion between adjacent teardrop-shaped bubbles can be reduced, increasing the number of microbubbles and improving the affinity to the polishing slurry even in the initial stages of polishing. If the blending amount is less than 10% by mass, no phase separation of the polyurethane resin is observed, and a flat sheet can be obtained without excessive shrinkage of the polyurethane resin sheet. Therefore, this range is preferable. By adding an appropriate amount of non-polar oil, the decrease in intermediate phase components and the increase in amorphous phase components when transitioning from a dry state to a wet state can be reduced.

[0025] (Polyurethane resin sheet thickness and buffing amount) There are no particular restrictions on the thickness of the polyurethane resin sheet in the polishing pad of the present invention, but it can be used in the range of 0.5 to 3.0 mm, preferably 0.5 to 2.0 mm, and more preferably 1.0 to 1.5 mm. Furthermore, the polyurethane resin sheet may be buffed. In the buffing process, it is preferable to buff the skin layer side of the film-forming resin so that the thickness is uniform. The amount of grinding on the skin layer side by buffing is preferably 30 to 300 μm, more preferably 50 to 150 μm. Within this range, the thickness of the polyurethane resin sheet is made uniform, and sufficient openings for holding slurry can be secured on the polished surface.

[0026] <<Manufacturing method for polishing pads>> The present invention can be manufactured by a conventionally known wet film formation method. Preferably, the method includes the steps of applying a resin solution composition containing a polyurethane resin, a non-polar oil, and a solvent to a film-forming substrate, and immersing the film-forming substrate coated with the resin solution composition in a solidification solution to solidify the resin solution composition and form a wet-formed polyurethane resin sheet. More specifically, the method for manufacturing the polishing pad of the present invention may include a step of preparing a resin solution composition (preparation step), a step of applying the resin solution composition to a film-forming substrate (application step), and a solidification regeneration step of immersing the film-forming substrate to which the resin solution composition has been applied in a solidification solution to solidify the resin solution composition. The process may include a step of washing and drying after wet film formation (washing and drying step), and may also include a grinding and removal step for flattening the surface of the sheet as needed. In the wet film formation process, a resin solution composition obtained by dissolving the polyurethane resin produced from the (A) polyisocyanate compound and (B) polyol compound described above, along with a non-polar oil, in a water-miscible organic solvent is continuously applied to a film-forming substrate. This substrate is then immersed in an aqueous solidification solution to solidify and regenerate the polyurethane resin into a sheet. The sheet thus obtained contains numerous bubbles generated during the solidification and regeneration of the polyurethane resin. These bubbles consist of multiple interconnected bubbles. These interconnected bubbles include teardrop-shaped bubbles and multiple nearly spherical microbubbles smaller than the teardrop-shaped bubbles, which are interconnected. After washing and drying, a long polyurethane resin sheet can be obtained. The following describes each step in the process of manufacturing a polyurethane resin sheet from polyurethane resin.

[0027] <Preparation process> In the preparation step (the step of preparing the resin solution composition), the polyurethane resin and non-polar oil described above are dissolved in a water-miscible organic solvent that can dissolve the polyurethane resin, and additives are added as desired. The mixture is then mixed until homogeneous to prepare the polyurethane resin solution composition. Preferably, the resin solution composition is filtered to remove aggregates and other impurities as needed, and then degassed under vacuum. Examples of water-miscible organic solvents that can dissolve the polyurethane resin include polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and methyl ethyl ketone (MEK). There are no limitations on the concentration of polyurethane resin in the resin solution composition, but for example, it can be 10 to 50% by mass. Furthermore, the resin solution composition may contain, for example, film-forming stabilizers such as hydrophilic surfactants that promote foaming and hydrophobic surfactants that stabilize the solidification and regeneration of polyurethane resin, as well as additives such as carbon black to stabilize foam formation.

[0028] <Coating process> In the coating process, the resin solution composition prepared in the preparation process is applied to a strip-shaped film-forming substrate at room temperature using a knife coater or the like, thereby forming a coating film. At this time, the coating thickness (amount of coating) of the resin solution composition can be adjusted by adjusting the gap (clearance) between the knife coater and the film-forming substrate. Flexible films, nonwoven fabrics, woven fabrics, etc., can be used as film-forming substrates. When using nonwoven or woven fabrics as film-forming substrates, it is preferable to pre-treat the substrate by immersing it in water or an aqueous organic solvent solution (such as a mixture of DMF and water) to suppress the penetration of the resin solution composition into the film-forming substrate during application.

[0029] <Coagulation regeneration process> In the solidification and regeneration process, the coating film obtained in the coating process (a film-forming substrate to which the resin solution composition has been applied) is immersed in a solidification solution that is a poor solvent for the polyurethane resin (for example, water or a solvent mainly composed of water), and the coating film of the resin solution composition is solidified and regenerated into a sheet-like form with numerous foams inside. In the solidification solution, generally, a skin layer with micropores and a thickness of several μm is first formed on the surface of the applied resin solution composition. Subsequently, as the organic solvent in the resin solution composition is replaced by the solidification solution, the polyurethane resin solidifies and regenerates in a sheet-like form on one side of the film-forming substrate. Typically, at this time, the organic solvent is removed from the resin solution composition, and the organic solvent is replaced by the solidification solution, resulting in the formation of a foamed layer on the underside of the skin layer (on the film-forming substrate side) in which foams with a larger pore diameter than the micropores formed in the skin layer and a roughly triangular cross-section with a rounded shape in the thickness direction of the sheet are dispersed almost uniformly. However, the foamed structure is not limited to this.

[0030] <Washing and drying process> In the washing and drying process, the polyurethane resin sheet that has been solidified and regenerated in the solidification and regeneration process is peeled off from the film-forming substrate and washed in a washing solution such as water to remove any organic solvents remaining in the polyurethane resin. After washing, the obtained polyurethane resin sheet is dried in a cylinder dryer or the like as needed. A cylinder dryer is a dryer equipped with a cylinder containing a heat source, and the polyurethane resin sheet is dried by passing along the circumferential surface of the cylinder. After drying, the polyurethane resin sheet is wound into a roll.

[0031] <Grinding and Removal Process> In the grinding and removal process, at least one of the two surfaces of the polyurethane resin sheet is ground and / or partially removed by buffing or slicing. There are no particular restrictions on the method of buffing or slicing, and grinding can be done by known methods. Specifically, grinding with sandpaper is one example. Buffing or slicing can make the thickness of the polyurethane resin sheet more uniform and the surface of the polyurethane resin sheet flatter, thereby further equalizing the pressing force on the workpiece and improving the flatness of the workpiece.

[0032] If the polishing pad has a multilayer structure consisting of a polishing layer (polyurethane resin sheet) and other layers such as a base material or intermediate layer, these layers are bonded to the polishing layer. Pressure-sensitive adhesives such as acrylic adhesives can be used for bonding. Next, after cutting the pad into the desired shape, such as a circle, an inspection is performed to confirm that there is no dirt or foreign matter attached, and the polishing pad is completed.

[0033] Furthermore, the polishing pad of the present invention may have grooves, embossing, or holes (punching) on ​​its surface as needed, a base material and / or an adhesive layer may be bonded to the polishing layer, and it may also have a light-transmitting portion. 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.

[0034] 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 polishing layer faces the workpiece to be polished. Both single-sided and double-sided polishing machines can be used as the polishing machine, but the polishing process when using a single-sided polishing machine will be described below as a specific example. First, the workpiece to be polished is held in the holding platen of the single-sided polishing machine. Next, a polishing pad is attached to the polishing platen, which is positioned opposite the holding platen. Then, a slurry containing abrasive grains (polishing particles) is supplied between the workpiece and the polishing pad, and the polishing platen or holding platen is rotated while pressing the workpiece toward the polishing pad with a predetermined polishing pressure, thereby polishing the workpiece by chemical mechanical polishing. [Examples]

[0035] 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 each example and comparative example, unless otherwise specified, "%" means "mass%" and "parts" means "parts by mass".

[0036] [Example 1] A polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used, containing 100 parts by mass of a polyester polyol with a number average molecular weight of 2000, composed of adipic acid and ethylene glycol as constituent units, and 16 parts by mass of ethylene glycol as a chain extender. To 100 parts of a 30% dimethylformamide (DMF) solution of the resin, 2 parts of Chrisbon Assister SD-8i (manufactured by DIC Corporation), a non-polar oil, and 25 parts of DMF for viscosity adjustment were mixed to prepare a resin solution composition. The resin modulus of the polyurethane resin used was 6 MPa. Using the obtained resin solution composition, a 1.15 mm thick polyurethane resin sheet was prepared by a wet film deposition method. The skin layer side of the obtained polyurethane resin sheet was buffed to a buffing depth of 0.1 mm using sandpaper with a buffing grit of #180, and a polishing pad was manufactured by bonding a 0.188 mm thick PET resin substrate to the side opposite the buffed surface with adhesive.

[0037] [Comparative Example 1] A polyester MDI polyurethane resin was used, containing 100 parts by mass of a polyester polyol with a number average molecular weight of 2000, composed of adipic acid and 1,4-butanediol as constituent units, and 12 parts by mass of ethylene glycol as a chain extender. To 100 parts of this 30% polyurethane resin solution, 5 parts of sodium lauryl sulfate (SLS) as a hydrophilic additive were added, and 25 parts of DMF for viscosity adjustment were mixed to prepare the resin solution composition. The resin modulus of the polyurethane resin used was 6 MPa. Using the obtained resin solution composition, a polyurethane resin sheet with a thickness of 0.90 mm was prepared by a wet film formation method, and the sheet was buffed with sandpaper of buff grit #180 with a buffing depth of 0.1 mm, as in Example 1. A polishing pad was manufactured by bonding a PET resin substrate with a thickness of 0.188 mm to the side opposite the buffed surface with adhesive.

[0038] [Comparative Example 2] A polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used, containing 100 parts by mass of a polyester polyol with a number average molecular weight of 2000, composed of adipic acid and ethylene glycol as constituent units, and 16 parts by mass of ethylene glycol as a chain extender. A resin solution composition was prepared by mixing 25 parts of DMF for viscosity adjustment with 100 parts of a 30% DMF solution of the resin. The resin modulus of the polyurethane resin used was 6 MPa. Using the obtained resin solution composition, a 1.15 mm thick polyurethane resin sheet was prepared by wet film formation in the same manner as in Example 1. The skin layer side of the obtained polyurethane resin sheet was buffed to a buffing depth of 0.1 mm using sandpaper with a buffing grit of #180, and a polishing pad was manufactured by bonding a 0.188 mm thick PET resin substrate to the side opposite the buffed side with adhesive.

[0039] <Preparation of sample for pulsed NMR measurement> Dried samples: Polishing pads from Example 1 and Comparative Examples 1-2 were punched out with a circular punch to a diameter of 8 mm to prepare circular samples. The prepared circular samples were stacked to a height of 1-1.2 cm in a 10 mmφ pulsed NMR sample tube and kept in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 48 hours to prepare pulsed NMR samples. Wet Samples: For each of the polishing pads used in Example 1 and Comparative Examples 1-2, circular samples were prepared by punching out 8mm in diameter using a circular punch. The cut samples were placed in a beaker containing deionized water at 20±2℃, covered with a bell jar, and degassed and immersed in water under negative pressure using an aspirator for 10 minutes. The samples were then wrapped in Kimwipes, surface moisture was wiped off, and the samples were stacked to a height of 1-1.2cm in a 10mmφ pulsed NMR sample tube to prepare the pulsed NMR measurement samples. In Comparative Example 1, however, the sample was not immersed in water after 10 minutes of degassing and immersion, so the degassing and immersion time was extended, and the sample was removed and used for measurement 60 minutes after degassing and immersion. <Measurement of pulsed NMR> Using the sample prepared above, structural analysis was performed by pulsed NMR under the following conditions. Pulsed NMR measurement conditions Pulsed NMR spectrometer Bruker Minispec mq20 Measurement method Solid echo method Total number of times: 128 Cumulative measurement interval: 0.5s Repeat time: 4.0s Measurement temperature 40℃ Under the above apparatus and conditions, pulsed NMR measurements were performed on circular samples prepared in test tubes. Using the analysis software "TD-NMR Analyzer" manufactured by BRUKER, the obtained relaxation curves were fitted according to the product manual using the following calculation formula (1). The least squares method was used to analyze the results so that the obtained decay curve and the fitted curve matched, and the proportions (abundance (%)) of crystalline, intermediate, and amorphous phases in the polished layer, as well as the relaxation time (T2), were determined. In this embodiment, the fitting was performed with the Weibull coefficients set to W(1)=2.0, W(2)=1.0, and W(3)=1.0, starting from the shortest relaxation time T2.

[0040] Table 1 TIFF0007850641000002.tif47157 *Mass percentage of the resin solution composition relative to the mass of the polyurethane resin

[0041] <<Index of wettability>> The water contact angles of the polishing pads of Example 1 and Comparative Examples 1 to 2 were measured using an automatic contact angle meter DropMaster DM500 (manufactured by Kyowa Interface Science Co., Ltd.). Those with a contact angle less than 90 degrees within 300 seconds were evaluated as ○, and those not less than 90 degrees were evaluated as ×. Specifically, for the measurement of the contact angle, under the conditions of a temperature of 20°C and a humidity of 60%, one drop of water was dropped onto the surface of the polishing pad from an injection needle, and the change over time of the dynamic contact angle from the time of dropping to 300 seconds was measured with an n number of 3. The results are shown in the graph of Table 1 and FIG. 3. Generally, when the contact angle is greater than 90 degrees, it is said to be water-repellent (repelling water and being difficult to wet with water). In the polishing pads of Example 1 and Comparative Example 2, the contact angle dropped below 90 degrees within 50 to 100 seconds, indicating that they were easy to wet and had good water affinity. On the other hand, in Comparative Example 1, the contact angle did not drop below 90 degrees even after 300 seconds had elapsed, indicating that it was difficult to wet and had poor water affinity.

[0042] <> The A hardness of the polishing layer was measured using an A hardness meter after cutting out a sample piece (10 cm × 10 cm) from the polishing pad in accordance with JIS K7311 and stacking a plurality of such sample pieces so that the thickness was 4.5 mm or more. For each of the polishing pads of the examples and comparative examples, polishing was performed under the following polishing conditions, and the polishing rate and polishing stability were measured. In addition, the surface of the polishing pad was pre-dressed using a diamond dresser under dressing conditions of a pressure of 9 N, a rotation speed of 54 rpm for the polishing head and the polishing surface plate, an ultrapure water supply rate of 200 ml / min, and a dressing time of 30 minutes, and then used for polishing evaluation.

[0043] <<Polishing test>> For the polishing pads of each of the examples and comparative examples, polishing was performed under the following polishing conditions, and the polishing rate was measured. <Polishing conditions> Polishing machine used: manufactured by Ebara Corporation, trade name "F-REX300" Polishing speed (rotation speed of the surface plate): 70 rpm Processing pressure: 176 g / cm² 2 Slurry: Colloidal silica slurry (pH: 11.5) Slurry flow rate: 200 mL / min Polishing time: 60 seconds Workpiece to be polished: Silicon wafer with TEOS (Tetra Ethyl Ortho Silicate) coating

[0044] <Average polishing rate> The polishing rate is expressed by dividing the amount of polishing (the difference in film thickness before and after polishing) by the polishing time. For the TEOS film on the wafer before and after polishing, the polishing rate (Å / min) was determined by dividing the thickness polished at each point by the polishing time, based on the average of the thickness measurements taken at 121 locations. Thickness measurements were performed using an optical film thickness analyzer (KLA Tencor, product name "ASET-F5x", measurement: DBS mode), with measurements taken at the 25th, 50th, and every 100 wafers thereafter. The average of the measured polishing rates was taken to determine the average polishing rate.

[0045] <Number of pages to process at startup> The rapid stabilization of the polishing rate in the initial stages of polishing was evaluated as follows: The polishing rate was tracked relative to the number of wafers polished, and the number of wafers polished at which the trend of increasing polishing rate ceased to be observed was defined as the "startup number of wafers." A smaller "startup number of wafers" indicates that the polishing rate stabilized more rapidly in the initial stages of polishing.

[0046] <Analysis of polishing rate stability> Polishing uniformity represents the variation in thickness measured at 121 locations during the evaluation of the polishing rate. From each measured polishing rate, the maximum, minimum, average, and standard deviation of the polishing rate were determined, and the polishing rate stability and polishing uniformity were evaluated using the following formula. Furthermore, a lower polishing rate stability value and smaller variation depending on the number of sheets processed indicates higher polishing stability. Polishing rate stability (%) = (Standard deviation of polishing rate / Mean polishing rate) × 100

[0047] Table 2 TIFF0007850641000003.tif28126

[0048] The polishing test results showed that the polishing rate of the comparative example 1 pad continued to increase from the start of polishing until the completion of polishing 600 wafers, but the polishing rate was unstable and the number of wafers processed for startup could not be measured, indicating poor polishing rate stability. The polishing rate stability of the comparative example 2 pad was improved compared to the comparative examples, but the polishing rate was low. The polishing rate stability of the example 1 pad was the best, as it required the fewest number of wafers to process for startup and showed high polishing rate stability.

Claims

1. A polishing pad comprising a polyurethane resin sheet formed by a wet film deposition method as an polishing layer, The polished layer is separated into three components—crystalline phase, intermediate phase, and amorphous phase—by subtracting the components with the longest spin-spin relaxation time T2 from the free induction decay signal (FID) obtained by pulsed NMR using the least squares method, and then separating the waveforms. The relative abundances of each phase are A1, A2, and A3 (%), respectively, under the following conditions: (i) The difference between the ratio of intermediate phase components in dry conditions A2dry (%) and the ratio of intermediate phase components in wet conditions A2wet (%) (A2wet - A2dry) is -20% or more. (ii) The difference between the ratio of amorphous components in dry state A3dry (%) and the ratio of amorphous components in wet state A3wet (%) (A3wet - A3dry) is 30% or less. (However, the "drying" condition involves holding the sample in a constant temperature and humidity chamber at 25°C and 50% relative humidity for 48 hours, while the "wet" condition involves immersing the sample in deionized water at 20±2°C for 10 minutes while reducing the pressure using an aspirator.) A polishing pad that meets the requirements.

2. The polishing pad according to claim 1, characterized in that the abrasive layer has an amorphous phase relaxation time T2(3)wet when wet that is 6 to 15 times that of the amorphous phase relaxation time T2(3)dry when dry.

3. The polishing pad according to claim 1, wherein the polyurethane resin sheet comprises a polyurethane resin which is a cured product of a resin solution containing at least a polyisocyanate compound (A) and a polyol compound (B), and the (B) polyol compound comprises ethylene glycol.

4. The polishing pad according to claim 1, wherein the thickness of the polyurethane resin sheet is in the range of 0.5 to 3.0 mm.

5. A step of applying a resin solution composition containing polyurethane resin, a non-polar oil, and a solvent to a film-forming substrate, and A process to form a wet-formed polyurethane resin sheet by immersing a film-forming substrate coated with the resin solution composition in a solidification solution and solidifying the resin solution composition, A method for manufacturing an abrasive pad according to any one of claims 1 to 4, including the method described in any one of claims 1 to 4.

6. The method for manufacturing an abrasive pad according to claim 5, wherein the content of the non-polar oil is 1 to 10% by mass relative to the mass of the polyurethane resin in the resin solution composition.

Images