JP5166172B2 - Polishing pad manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a polishing pad, and in particular, a polishing pad having a polishing layer made of a polyurethane resin obtained by reacting a polyisocyanate compound, a polyol compound and a polyamine compound and having a polishing surface for polishing an object to be polished. It relates to the manufacturing method.

  Since the surface (processed surface) of a material (object to be polished) such as a semiconductor device manufacturing or a glass substrate for liquid crystal display is required to have flatness, polishing using a polishing pad is performed. In semiconductor devices, as the degree of integration of semiconductor circuits increases rapidly, miniaturization and multilayer wiring for the purpose of higher density have progressed, and a technique for further flattening the processed surface has become important. On the other hand, with a glass substrate for a liquid crystal display, higher flatness of a processed surface is required with an increase in size of the liquid crystal display. As demand for flatness increases, polishing performance such as polishing accuracy and polishing efficiency in polishing processing, in other words, performance required for a polishing pad is also increasing.

  In general, a polishing pad used for polishing processing is made of a polyurethane resin obtained by reacting a polyisocyanate compound, a polyol compound and a polyamine compound, and has a polishing layer having a polishing surface for polishing the processed surface of an object to be polished. Yes. The polishing layer has a foamed structure, and an opening is formed in the polishing surface by a grinding process or the like, so that a polishing liquid (slurry) containing abrasive grains supplied during polishing is held in the opening, The polishing liquid is released approximately evenly between the polished surface and the processed surface. In addition, the polishing surface may be subjected to grooving or the like in order to enhance the supply capability of the polishing liquid and the discharge of polishing scraps generated by the polishing process.

  However, when clogging with slurry or polishing debris occurs in the openings, grooves, etc., not only the polishing performance is lowered, but also the processed surface of the workpiece is scratched and the flatness is lowered. In order to improve the supply and retention of the slurry, it is conceivable to increase the number of openings and grooves, but on the contrary, the elasticity of the polishing layer is impaired and the flatness of the object to be polished is lowered. Furthermore, the discharge of slurry is promoted by the increase in the number of openings and grooves, leading to a reduction in polishing performance. Although the polishing performance can be stabilized by continuing to supply a large amount of slurry, a large amount of slurry is required and a large amount of slurry waste liquid is required, resulting in high costs.

In order to solve these problems, for example, the average opening diameter of small holes having an opening diameter of less than 400 μm on the polishing surface is 20 to 100 μm, and 10 to 100 large holes with an opening diameter of 400 to 1000 μm are provided on the polishing surface. A technique of a polishing pad formed with 100 cm ² is disclosed (Patent Document 1). In the technique of Patent Document 1, the slurry holding performance is improved by forming a large opening. However, when foaming with water in forming a foam structure, the speed at which the raw material liquid for forming the polishing pad is poured into the mold is slow. As a result, the large apertures are formed, and there is a problem that the dispersion state of the large apertures tends to vary. In addition, in the formation of a foam structure, when two types of hollow polymer microspheres are added to the raw material liquid and poured into a mold, the bulk density of the two types of hollow polymer microspheres is different, so that the large pores are dispersed. There is a problem that variations tend to occur. In such a polishing pad, small openings are likely to be clogged in a portion where there are few large openings, and aggregates due to abrasive particles and polishing debris are likely to be generated in the large openings, and the occurrence of scratches on the processed surface may increase. .

  On the other hand, when clogging occurs, the polishing process can be interrupted and the polishing surface can be dressed, that is, the clogged surface layer can be removed to expose the new surface layer, thereby restoring the polishing performance. is there. However, since the efficiency is inevitably lowered by interrupting the polishing process, a technique for giving the dressing property to the polishing pad itself is disclosed. For example, a polishing pad technique in which the weight loss (degree of wear) by the Taber abrasion test is 150 to 350 mg is disclosed (Patent Document 2). Further, by adding 50% by weight or more of polyether polyol, polyester polycarbonate polyol or polycarbonate polyol as the alkali-resistant polyol compound with respect to the total polyol compound, the polishing layer is made into a potassium hydroxide aqueous solution (40 ° C.) having a pH of 12.5. A polishing pad technique is disclosed in which the difference in wear loss by the Taber abrasion test before and after immersion for 24 hours is 10 mg or less (Patent Document 3).

JP 2006-210657 A JP 2001-277101 A Japanese Patent No. 3570681

  However, in the technique of Patent Document 2, a chain extender is prepared by mixing a prepolymer using a specific polyol component and a general prepolymer as a raw material liquid for forming a polishing pad in order to give the polishing pad dressing properties. And polymerized with a foaming agent. For this reason, mixed spots of two kinds of prepolymers are likely to occur, the foamed structure is non-uniform, and the pore diameter on the polished surface becomes large, so there is a problem that the hardness is low and the polishing layer is easily worn. As a result, the flatness of the object to be polished and the uniformity within the processed surface are not sufficient, and the change in the polishing performance such as the polishing speed becomes large. It is enough. Further, the technique of Patent Document 3 has a problem that although the change in the polishing rate or the like is reduced by improving the alkali resistance, the wear loss itself is insufficient, so that clogging of the holes is likely to occur. On the other hand, considering the variety of materials and required performance of the object to be polished, it is difficult to uniformly determine the weight loss. Therefore, it is desirable to expose a new surface by moderate abrasion of the polishing surface during polishing processing, but if the wear loss becomes too large, inconveniences such as scratches will occur due to wear debris of the polishing pad, so It is important to optimize wear loss according to the object.

  An object of the present invention is to provide a method for manufacturing a polishing pad that can optimize the degree of wear and stabilize the polishing performance in view of the above-mentioned cases.

In order to solve the above-mentioned problems, the present invention comprises a preparation step of preparing each component of a polyisocyanate compound, a polyol compound, a polyamine compound and water, and a reaction between the polyisocyanate compound prepared in the preparation step and the polyol compound in advance. A foam-forming step of forming a foam from a mixed liquid obtained by mixing an isocyanate group-containing compound, the polyamine compound, the water, and a gas that is non-reactive with the components, and the foam-forming step. A polishing layer forming step of forming a polishing layer having a polishing surface for polishing the object to be polished from the formed foam, and the polyol compound for the isocyanate group of the polyisocyanate compound prepared in the preparation step Equivalent ratio of total hydroxyl group and amino group of polyamine compound And the bulk density of the polishing layer formed in the polishing layer forming step, where HSC (%) is the content of the hard segment formed by the reaction of the isocyanate group-containing compound obtained in the foam forming step and the polyamine compound Is D (g / cm ³ ) and the Shore A hardness is A (degrees), the F value obtained by F = −13.8 · HSC-726 · R + 773 · D-7.95A + 1516 is 100 to 200. The polishing pad manufacturing method is characterized by adjusting the amount of each component prepared in the preparation step and the amount of the gas mixed in the foam formation step so as to be within a range.

  In the present invention, the bulk density D of the polishing layer is interrelated with the foamed structure formed by mixing the non-reactive gas, and the content ratio HSC, equivalent ratio R and hardness A are interrelated with hardness and brittleness. Represents the ease of wear of the polishing layer. By setting the F value in the range of 100 to 200, the degree of wear is optimized even if the bulk density D and hardness A are changed according to the object to be polished. In addition, it is possible to stabilize the polishing performance because the polishing surface is regenerated timely due to wear during polishing.

In this case, in the preparation step, it is preferable to adjust the amount of the polyisocyanate compound, the polyol compound, and the polyamine compound to be prepared so that the equivalent ratio R is in the range of 0.7 to 0.9. At this time, in the foam forming step, it is preferable to adjust the amount of the isocyanate group-containing compound and the polyamine compound to be mixed so that the content rate HSC is in the range of 32% to 42%. In the foam forming step, it is preferable to adjust the amount of water and gas to be mixed so that the bulk density D is in the range of 0.45 g / cm ^{3 to} 0.55 g / cm ³ . Moreover, it is preferable to adjust the amount of each component prepared in the preparation step and the amount of gas mixed in the foam formation step so that the hardness A is 85 degrees or more. At this time, the polyisocyanate compound prepared in the preparation step may contain at least 50% by weight of tolylene diisocyanate, and the polyol compound may contain at least 50% by weight of polytetramethylene ether glycol. In addition, if the viscosity of the isocyanate group-containing compound obtained in the foam formation step is in the range of 2000 mPa · s to 20000 mPa · s at a temperature of 50 ° C. to 80 ° C., the movement of foaming is suppressed in the mixed liquid, Can be made uniform. At this time, if the water prepared in the preparation step is preliminarily dispersed in the polyol compound at a ratio of 1% by weight to 6% by weight, the dispersed state of foaming can be made more uniform. In addition, if the amount of water prepared in the preparation step is set to a ratio of 1 g to 6 g with respect to 1 kg of the weight of the isocyanate group-containing compound obtained in the foam formation step, the amount of water is limited. And bias can be suppressed. If the amount of gas mixed in the foam formation step is 0.5 L to 3.4 L with respect to 1 kg of the total weight of the isocyanate group-containing compound, polyamine compound and water, the amount of gas in the mixed solution is limited. Therefore, the formation of extremely large foam can be suppressed. In the foam formation step, if the mixed solution is prepared under a mixing condition of a shear rate of 9,000 to 41,000 / sec and a shearing frequency of 300 to 10,000, the unevenness of foaming can be further suppressed. Groove processing or embossing may be performed on the polishing surface side of the polishing layer formed in the polishing layer forming step. In addition, a light transmission portion that allows light transmission for optically detecting the polishing state during polishing may be formed in at least a part of the polishing layer formed in the polishing layer forming step. At this time, it is preferable that the light transmission part is formed over the entire thickness direction of the polishing layer.

  According to the present invention, the bulk density D of the polishing layer is interrelated with the foam structure formed by mixing the non-reactive gas, and the content ratio HSC, equivalent ratio R and hardness A are interrelated with hardness and brittleness. Since the F value indicates the ease of wear of the polishing layer, the degree of wear is appropriate even if the bulk density D and hardness A are changed according to the object to be polished by setting the F value in the range of 100 to 200. In addition, the polishing surface can be regenerated timely due to wear during polishing, so that the effect of stabilizing the polishing performance can be obtained.

  Embodiments in which the present invention is applied to a polishing pad for primary polishing of a silicon wafer will be described below with reference to the drawings.

(Polishing pad)
As shown in FIG. 1, the polishing pad 1 of this embodiment is provided with a urethane sheet 2 as a polyurethane resin polishing layer. The urethane sheet 2 has a polishing surface P for polishing an object to be polished. The urethane sheet 2 includes an isocyanate group-containing compound obtained by reacting a polyisocyanate compound and a polyol compound in advance, a dispersion obtained by previously dispersing and diluting water in a polyol compound, a polyamine compound, an isocyanate group-containing compound, and a dispersion. It is formed by slicing a polyurethane foam obtained by casting and curing a mixed liquid obtained by mixing a gas non-reactive with a polyamine compound into a mold. That is, the urethane sheet 2 constituting the polishing pad 1 is formed by dry molding.

  Inside the urethane sheet 2, during the dry molding, the foam 3 and the foam 5 having a circular or elliptical cross section are substantially uniformly dispersed by water and non-reactive gas in the dispersion. Yes. That is, the polyurethane sheet 2 has a foam structure. Foam 3 formed with water in the dispersion has an average pore diameter of 30 to 200 μm, and foam 5 formed of non-reactive gas has a pore diameter of 500 to 2000 μm. Since the urethane sheet 2 is formed by slicing polyurethane foam, a part of the foam 3 and foam 5 is opened on the polishing surface P, and an opening 4 and an opening 6 are formed, respectively. Since the opening 4 and the opening 6 are formed by the openings of foam 3 and foam 5, the average hole diameter is 30 to 200 μm in the opening 4, and the hole diameter is 500 to 2000 μm in the opening 6. That is, the opening 4 is a small opening and the opening 6 is a large opening. The thickness of the urethane sheet 2 is set in a range of 1.3 to 2.5 mm. In this urethane sheet 2, the wet hardness retention rate defined by the ratio of the hardness when immersed in water (hot water) at a temperature of 70 ° C. for the same fixed time with respect to the hardness when immersed in water at a temperature of 20 ° C. for 85 hours is 85. % Or more.

In the urethane sheet 2, the F value obtained by F = −13.8 · HSC-726 · R + 773 · D-7.95A + 1516 (hereinafter referred to as the formula (1)) is in the range of 100 to 200. In the formula (1), HSC indicates the content (%) of the hard segment formed by the reaction of the isocyanate group-containing compound and the polyamine compound, and R is the isocyanate group of the polyisocyanate compound used to produce the isocyanate group-containing compound. The equivalent ratio of the total of the hydroxyl group of the polyol compound and the amino group of the polyamine compound to D, D represents the bulk density (g / cm ³ ) of the urethane sheet 2, and A represents the Shore A hardness (degree) of the urethane sheet 2. ing.

  Here, each factor in the formula (1), that is, the content ratio HSC, the equivalent ratio R, the bulk density D, and the hardness A will be described, and the meaning of the formula (1) will be described. Usually, a polyurethane resin has a hard segment formed by the reaction of an isocyanate group-containing compound and a polyamine compound, and a soft segment formed by a polyol compound. In the hard segment, hydrogen bonds are formed between the urethane bonds and the cohesive force is increased, so that the hard segment exhibits rigidity and high crystallinity. On the other hand, in the soft segment, the hydrogen bond is hardly formed and the cohesive force is weakened, so that the soft segment is easily deformed and has low crystallinity. Therefore, the wearability (degree of wear) and hardness of the polyurethane resin can be adjusted by the content HSC. If the content HSC is too small, stickiness due to low crystallinity (a phenomenon that remains on the polished surface without tearing even if worn) is likely to occur, and the hardness tends to be insufficient, so the apertures 4 and 6 are likely to be clogged. In addition, the flatness of the object to be polished may be lowered. On the other hand, if the content HSC is too large, it becomes highly brittle and hard because of its high crystallinity, which causes excessive wear and impairs the circulation of the slurry. In this example, the content rate HSC is adjusted to be in the range of 32 to 42%.

  The content rate HSC is calculated by the following formula (hereinafter referred to as formula (2)), that is, HSC = 100 · (r−1) · (Mdi + Mda) / (Mg + r · Mdi + (r−1) · Mda). be able to. In the formula (2), Mdi represents an average molecular weight per bifunctional isocyanate group of the polyisocyanate compound, Mg represents an average molecular weight per bifunctional hydroxyl group of the polyol compound, and Mda represents an average per bifunctional amino group of the polyamine compound. The molecular weight is indicated, and r indicates the equivalent ratio of the isocyanate group of the polyisocyanate compound to the hydroxyl group of the polyol compound. The content rate HSC can be calculated using the formula (2) from the blending ratio of the polyisocyanate compound, the polyol compound and the polyamine compound used when the urethane sheet 2 is molded. In other words, the content rate HSC can be adjusted by the compounding ratio of each compound used at the time of molding. Since this blending ratio can also be obtained by structural analysis of the urethane sheet 2 using a nuclear magnetic resonance (NMR) spectrum or the like, the content ratio HSC can be obtained even after the urethane sheet 2 is molded.

  Also, the equivalent ratio R can be calculated from the blending ratio of the polyisocyanate compound, the polyol compound and the polyamine compound at the time of molding the urethane sheet 2 as in the case of the content ratio HSC. It can also be calculated. If the equivalent ratio R is too small, unreacted isocyanate groups are likely to remain. Therefore, in the molded urethane sheet 2, the dimensional stability is impaired due to heat shrinkage, etc., and the flatness of the object to be polished due to thickness spots and foam spots. In addition to lowering, it becomes brittle, so that wear tends to occur and durability becomes insufficient. On the other hand, if the equivalent ratio R is too large, the chain elongation reaction by the polyol compound or the polyamine compound is insufficient, and the elasticity of the urethane sheet 2 is impaired, resulting in stickiness and clogging of the openings 4 and 6. It becomes easy. In this example, the equivalence ratio R is adjusted to be in the range of 0.7 to 0.9.

The bulk density D correlates with the foam structure of the urethane sheet 2. That is, when the pore diameter of foam 3 or foam 5 is too small or the number of foams is too small, the bulk density D increases. When the pore diameters of the foam 3 and foam 5 are reduced, the apertures 4 and 6 are also reduced, so that clogging is likely to occur. When the number of foams is reduced, the number of apertures 4 and apertures 6 is reduced. It is difficult to obtain sufficient polishing performance such as. For this reason, in this example, the bulk density D is adjusted to be in the range of 0.45 to 0.55 g / cm ³ . On the other hand, the hardness A varies depending on the equivalent ratio R, the content ratio HSC, and the bulk density D. In addition, the hardness A depends on the average polymerization degree and molecular weight distribution of the urethane resin constituting the urethane sheet 2 and the shape and distribution of the pores. It is important to consider these as they may change. If the hardness A is too low, since the urethane sheet 2 is too soft, not only the flatness of the object to be polished is impaired, but also stickiness is likely to occur, and the openings 4 and 6 are likely to be clogged. On the other hand, if the hardness A is too high, scratches are likely to occur. In this example, the hardness A is adjusted to be 85 degrees or more. This is equivalent to 75 degrees or less if expressed by Shore D hardness. The bulk density D and hardness A depend on the material of the polyurethane resin, but the size and quantity of the foam 3 and foam 5 are changed, in other words, the amount of water in the dispersion and the amount of gas mixed in the liquid mixture. It can be adjusted by changing the amount.

  As described above, the content rate HSC, the equivalent ratio R, the bulk density D, and the hardness A in the urethane sheet 2 are related to the degree of wear of the urethane sheet 2 and the ease of clogging. When these relationships are comprehensively summarized, the above-described formula (1) can be obtained. Therefore, the F value in the formula (1) represents the ease of wear of the urethane sheet 2. This F value corresponds to the wear loss (mg) per 1000 polishings on the polishing surface P by the Taber abrasion tester of Japanese Industrial Standard (JIS K 6902, abrasion resistance A method). In the urethane sheet 2, the polyisocyanate compound, the polyol compound, the polyamine compound, and the amounts of water and gas mixed in the mixed solution are adjusted so that the F value is in the range of 100 to 200. By setting the F value within this range, the wearability of the urethane sheet 2 is optimized, and the polishing pad 1 can be suitably used for primary polishing of a silicon wafer. Since the bulk density D correlates with the foam structure of the urethane sheet 2 and the content rate HSC affects the hardness, for example, by reducing the equivalent ratio R, the F value can be set without greatly changing the foam structure or hardness. Can be bigger. In other words, the F value can be optimized by adjusting the bulk density D and the hardness A even if the content rate HSC and the equivalent ratio R are changed in accordance with the characteristics of the object to be polished. By adjusting the content ratio HSC, the equivalence ratio R, the bulk density D, and the hardness A so as to satisfy the range of the F value obtained by the above-described formula (1), defects caused by the respective factors can be compensated. As a result, when the workpiece is polished, the polishing surface P is worn and regenerated as appropriate, and clogging of the openings 4 and 6 is suppressed. Thereby, since the slurry is supplied to the entire processing surface while being held, the polishing performance can be stabilized.

  As shown in FIG. 1, the polishing pad 1 has a double-sided tape for attaching the polishing pad 1 to a polishing machine on the surface opposite to the polishing surface P of the urethane sheet 2. The double-sided tape has adhesive layers formed on both sides of a base material 7 such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET). The double-sided tape is bonded to the urethane sheet 2 with an adhesive layer on one side, and the adhesive layer on the other side (the lowermost side in FIG. 1) is covered with the release paper 8.

(Manufacture of polishing pad)
The polishing pad 1 is manufactured through each process shown in FIG. That is, a preparation step (preparation step) for preparing a polyisocyanate compound, a polyol compound, a dispersion obtained by dispersing and diluting water in advance in a polyol compound, and a polyamine compound, respectively, by reacting the polyisocyanate compound and the polyol compound in advance. A mixing step (foam formation step) in which an isocyanate group-containing compound is produced, and the resulting isocyanate group-containing compound, dispersion, polyamine compound, and non-reactive gas for each component are mixed to prepare a mixture. Part), casting process for casting the mixed liquid into the mold (part of the foam forming step), curing molding process for foaming and curing in the mold to form polyurethane foam (foam forming step) A part of the polyurethane foam 2 by slicing the polyurethane foam into a sheet. Step (polishing layer formation step), it is manufactured through a lamination step of forming a polishing pad 1 attaching the urethane sheet 2 and the double-sided tape. Hereinafter, it demonstrates in order of a process.

(Preparation process)
In the preparation step, a polyisocyanate compound, a polyol compound, a dispersion, and a polyamine compound are prepared. The polyisocyanate compound to be prepared is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, as a diisocyanate compound having two isocyanate groups in the molecule, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2 , 4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethoxy-4,4′-biphenyl diisocyanate, 3,3′-dimethyldiphenylmethane-4,4 ′. -Diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, Kurohekishiren 1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p- phenylenediisothiocyanate, xylylene-1,4-diisothiocyanate, mention may be made of ethylidyne diisothiocyanate like. Two or more of these diisocyanate compounds may be used in combination, and a triisocyanate compound having three or more, for example, three isocyanate groups in the molecule may be used.

  On the other hand, the polyol compound may be a compound such as a diol compound or a triol compound, for example, a low molecular weight polyol compound such as ethylene glycol or butylene glycol, and a polyether polyol compound such as polytetramethylene glycol (PTMG). Polyester polyol compounds such as a reaction product of ethylene glycol and adipic acid and a reaction product of butylene glycol and adipic acid, a high molecular weight polyol compound such as a polycarbonate polyol compound and a polycaprolactone polyol compound can be used. Two or more of these polyol compounds may be used in combination.

  Moreover, since the polyol compound used for the preparation of the dispersion reacts with the isocyanate group of the prepolymer to form a soft segment, it is possible to suppress the elution during the polishing process and thus adverse effects on the polishing characteristics. The polyol compound may be a compound such as a diol compound or a triol compound, for example, a low molecular weight polyol compound such as ethylene glycol or butylene glycol, a high molecular weight such as PTMG, polyethylene glycol (PEG), or polypropylene glycol (PPG). Any of the molecular weight polyol compounds can be used. Since it becomes easy to make water dispersion uniform in the mixing step by setting the viscosity to the same level as the prepolymer or polyamine compound solution, it is preferable to use a polyol compound having a number average molecular weight of 500 to 3,000. In this example, PTMG having a number average molecular weight of about 1000 is used, and water is dispersed and diluted at a ratio of 1 to 6% by weight to prepare a dispersion. At the time of preparing the dispersion, stirring and mixing may be performed using a general stirring device, and water may be dispersed and diluted substantially evenly. Although there is no restriction | limiting in particular as water to be used, In order to avoid mixing of an impurity etc., it is preferable to use distilled water. Moreover, it is preferable to prepare the quantity of a dispersion liquid so that the quantity of water may become the ratio of 1-6g with respect to 1 kg of the weight of the prepolymer mixed by the mixing process of the following process. If the amount of water is too small, the size of the foam formed in the resulting polyurethane foam will be too small. Conversely, if the amount is too large, extremely large foam will be formed. For example, when the weight of the prepolymer is 1 kg and the dispersion is 100 g, the amount of water contained in this dispersion is 1 to 6 g.

  The polyamine compound forms a hard segment by reacting with the isocyanate group of the prepolymer. As this polyamine compound, an aliphatic or aromatic polyamine compound can be used. For example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, 3,3 ′. Examples include -dichloro-4,4'-diaminodiphenylmethane (hereinafter abbreviated as MOCA), a polyamine compound having the same structure as MOCA, and the like. Further, the polyamine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, and di-2-hydroxy. Examples include ethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. Two or more of these compounds may be used in combination. As a polyamine compound, in this example, MOCA is used in a state of being heated to about 120 ° C. and melted.

(Mixing process, casting process, curing molding process)
As shown in FIG. 2, in the mixing step, an isocyanate group-containing compound, that is, an isocyanate-terminated urethane prepolymer (hereinafter simply abbreviated as prepolymer) is obtained by reacting the polyisocyanate compound prepared in the preparation step with a polyol compound. .) Is generated. When the obtained prepolymer is mixed with the dispersion and polyamine compound prepared in the preparation step, a gas that is non-reactive with the prepolymer, dispersion, and polyamine compound (hereinafter referred to as non-reactive gas). To prepare a mixed solution. In the casting process, the mixed liquid prepared in the mixing process is cast into a mold, and in the curing molding process, the polyurethane foam is molded by foaming and curing in the mold. In this example, a mixing process, a casting process, and a curing molding process are performed continuously.

  When producing the prepolymer, the prepolymer can be obtained by making the molar amount of the isocyanate group larger than the molar amount of the hydroxyl group. Moreover, when the prepolymer used has a too high viscosity, the fluidity is deteriorated and it becomes difficult to mix substantially uniformly during mixing. When the temperature is raised and the viscosity is lowered, the pot life is shortened, and on the contrary, the size of the foam 3 and foam 5 formed in the polyurethane foam obtained by producing mixed spots is varied. On the other hand, if the viscosity is too low, the bubbles move in the mixed solution, and it becomes difficult to form the foam 3 and the foam 5 that are substantially uniformly dispersed in the polyurethane foam. For this reason, it is preferable that a prepolymer sets the viscosity in the temperature of 50-80 degreeC in the range of 2000-20000 mPa * s. For example, the viscosity can be set by changing the molecular weight (polymerization degree) of the prepolymer. The prepolymer is heated to about 50 to 80 ° C. to be in a flowable state.

  As shown in FIG. 3, in the mixing step, a mixed solution is prepared by the mixer 20, and in the casting step, the prepared mixed solution is continuously cast from the mixer 20 into the mold 25 and cured in the curing molding step. By doing so, the polyurethane foam is molded. The mixer 20 includes a mixing tank 12 in which a stirring blade 14 is incorporated. On the upstream side of the mixing tank 12, a prepolymer as the first component, a polyamine compound as the second component, a supply tank containing the dispersion as the third component, and a supply for supplying the non-reactive gas into the mixing tank 12 A device 16 is arranged. The supply port from each supply tank is connected to the upstream end of the mixing tank 12, and the supply port of the non-reactive gas from the supply device 16 is approximately from the upstream end to the entire length of the mixing tank 12. It is connected to the 1/3 position. The stirring blade 14 is fixed to a rotating shaft arranged from the upstream side to the downstream side at a substantially central portion in the mixing tank 12. As the rotating shaft rotates, the stirring blade 14 rotates to mix the first component, the second component, the third component, and the non-reactive gas so as to shear. The obtained mixed liquid is poured into the mold 25 from a discharge port arranged at the downstream end of the mixing tank 12. In this example, the size of the mold 25 is set to 1050 mm (length) × 1050 mm (width) × 50 mm (thickness).

  Many of the polyamine compounds represented by the prepolymer of the first component and the MOCA of the second component are both solid or difficult to flow at room temperature, so each supply tank is heated so that each component can flow. ing. Further, in order to prevent moisture contained in the non-reactive gas from participating in the reaction in the mixing tank 12, the non-reactive gas from the supply device 16 is removed by a moisture removing device (not shown). Yes. The supplied non-reactive gas becomes fine bubbles by the rotation of the stirring blade 14 in the mixing tank 12, and this bubble exerts a bubbling effect that disperses the dispersion obtained by dispersing and diluting water substantially uniformly in the mixture. . Further, the foam 5 is formed by a part of the supplied non-reactive gas. If the supply amount of the non-reactive gas is too small, the bubbling effect is insufficient, and the dispersion state of water or foam 5 tends to be biased. On the contrary, if the amount is too large, extremely large bubbles are generated. For this reason, it is preferable to adjust the supply amount of a non-reactive gas so that it may become a ratio of 0.5-3.4L with respect to 1 kg of total weight of a prepolymer, a dispersion liquid, and a polyamine compound. Examples of the non-reactive gas include air, nitrogen, oxygen, carbon dioxide, helium, and argon.

  The first component, the second component, and the third component are supplied to the mixing tank 12, and the non-reactive gas is supplied at a stage where they are mixed to some extent by the stirring blade 14. Since the viscosity of each component is adjusted to the same level, when supplying the non-reactive gas, the viscosity of the solution in which each component is mixed is 50 to 20000 mPa · s at a temperature of 50 to 80 ° C. By adjusting the shearing speed and the number of times of shearing of the stirring blade 14, the components and the non-reactive gas are mixed almost uniformly to prepare a mixed solution. When the shear rate of the stirring blade 14 is too low, the size of the foam 3 and the foam 5 formed in the resulting polyurethane foam becomes too large. On the other hand, if the shear rate is too high, the temperature rises due to the heat generated by friction between the stirring blade 14 and the mixed solution, and the viscosity decreases, so that bubbles in the mixed solution move (during molding), and the resulting polyurethane Variations in the dispersed state of foam 3 and foam 5 formed in the foam are likely to occur. On the other hand, if the number of times of shearing is too small, the size of the generated bubbles is likely to be uneven (variation). On the other hand, if the number of shearing is too large, the viscosity decreases due to temperature rise, and the foam 3 and foam 5 are not formed substantially evenly. For this reason, in a mixing process, a shear rate is set to the range of 9,000-41,000 / sec, and the frequency | count of shear is set to the range of 300-10,000 times, and it mixes. The mixing time (residence time) in the mixer 20 is about 1 second although it depends on the flow rate of the mixed liquid (maximum 1 liter / sec). That is, for example, the time required to inject about 100 kg of the mixed solution into the mold 25 in the injecting step is about 1 to 2 minutes. In addition, a shear rate and the frequency | count of shear can be calculated | required by following Formula. That is, shear rate (/ sec) = diameter (mm) of blade tip of stirring blade 14 × circularity × rotational speed (rpm) of stirring blade 14 ÷ 60 ÷ blade tip of stirring blade 14 and inner wall of mixing vessel 12 Clearance (mm), number of times of shearing (times) = rotation speed of stirring blade 14 (rpm) ÷ 60 × retention time of mixed solution in mixing tank 12 (second) × number of blades of stirring blade 14 Can do.

  The F value of the polyurethane foam obtained can be adjusted by the mixed solution prepared in the mixing step. That is, the average molecular weights Mdi, Mg, and Mda per each bifunctionality are determined by the polyisocyanate compound, polyol compound, and polyamine compound used for the production of the prepolymer. The equivalent ratio r is determined by the amount of the mixed polyisocyanate compound and the amount of the polyol compound. From these numerical values, the hard segment content HSC is obtained by the above-described equation (2). The equivalent ratio R is determined from the amounts of the mixed polyisocyanate compound, polyol compound and polyamine compound. By setting the bulk density D and the hardness A in the above-described ranges, the F value is obtained by the above-described formula (1).

  When injecting the mixed liquid into the mold 25 in the liquid injection process, the mixed liquid from the mixer 20 is discharged from the discharge port of the mixing tank 12, for example, between two opposing sides of the mold 25 through a flexible pipe. Liquid is introduced into a liquid injection port (not shown) having a triangular cross section that reciprocates (for example, between the left and right in FIG. 3). While reciprocating the liquid injection port, the end of the discharge port (the end of the flexible pipe) is reciprocated in a direction intersecting the direction of movement of the liquid injection port. The mixed liquid is poured into the mold 25 substantially evenly.

  In the curing molding process, the injected mixed liquid is reacted and cured in the mold 25 to form a block-like polyurethane foam. At this time, the prepolymer is crosslinked and cured by the reaction between the prepolymer, the polyol compound, and the polyamine compound. Simultaneously with the progress of the crosslinking and curing, the isocyanate groups of the prepolymer react with the water dispersed and diluted in the dispersion to generate carbon dioxide. Since the cross-linking and curing proceeds, the generated carbon dioxide does not escape to the outside, and the foam 3 is formed.

(Slicing process)
As shown in FIG. 2, in the slicing step, the polyurethane foam obtained in the curing molding step is sliced into a sheet to form a plurality of urethane sheets 2. A general slicing machine can be used for slicing. At the time of slicing, the lower layer portion of the polyurethane foam is held and sliced to a predetermined thickness in order from the upper layer portion. In this example, the thickness to be sliced is set in a range of 1.3 to 2.5 mm. In addition, in the polyurethane foam molded with the mold 25 having a thickness of 50 mm used in this example, for example, about 10 mm of the upper layer portion and the lower layer portion is not used due to scratches and the like, and from about 30 mm portion of the center portion. 10 to 25 urethane sheets 2 are formed. Since the polyurethane foam in which the foam 3 and the foam 5 are substantially uniformly formed is obtained in the curing molding process, the average number of the holes 4 formed on the surface of the plurality of urethane sheets 2 formed in the slicing process The hole diameter is in the range of 30 to 200 μm, and the hole diameter of the opening 6 is in the range of 500 to 2000 μm. If the average hole diameter of the open holes 4 is less than 30 μm, the abrasive is likely to be clogged during the polishing process, so that the life of the polishing pad is likely to be shortened. On the other hand, if it exceeds 200 μm, it is difficult to control the substantially uniform hole diameter. . On the other hand, if the hole diameter of the opening 6 is less than 500 μm, the effect of improving the slurry retention cannot be obtained sufficiently. Conversely, if the hole diameter exceeds 2000 μm, aggregation of slurry and polishing waste occurs, and scratches are easily induced. .

(Lamination process)
In the laminating process, the urethane sheet 2 formed in the slicing process and the double-sided tape are bonded together. After cutting into a desired shape and size such as a circle, an inspection such as confirming that there is no adhesion of dirt or foreign matter is performed to complete the polishing pad 1.

  When polishing an object to be polished, the polishing pad 1 is mounted on a polishing surface plate of a polishing machine. When the polishing pad 1 is mounted on the polishing surface plate, the release paper 8 is removed, and the surface is adhered and fixed to the polishing surface plate with the exposed adhesive layer. By pressing the object to be polished held on the holding surface plate arranged to face the polishing surface plate to the polishing surface P side and rotating the polishing surface plate or holding surface plate while supplying slurry from the outside. The processed surface of the object to be polished is polished. At this time, the slurry is held in the opening 4 and the opening 6 and supplied to the entire processing surface substantially evenly. Further, the polishing surface P side wears with the polishing process, and a new polishing surface is regenerated at an appropriate time, so that the polishing is performed without clogging the openings 4 and 6. Normally, water is used as a medium for the polishing liquid, but an organic solvent such as alcohol can also be mixed.

(Action etc.)
Next, the operation and the like of the polishing pad 1 of the present embodiment will be described.

  In the conventional polishing process, a polishing pad having a foam structure and having an opening formed in the polishing surface is used. During polishing processing, a polishing liquid containing abrasive particles is supplied between the object to be polished and the polishing pad, and this polishing liquid is supplied to the entire processed surface of the object to be polished while being held in an opening formed in the polishing surface. As a result, the object to be polished is polished. However, the opening may be clogged with abrasive particles or polishing debris generated during polishing. When clogging of the opening occurs, not only does the processing surface suffer from polishing scratches, but the flatness is impaired, and the life of the polishing pad is also reduced. For this reason, when clogging of the opening occurs, the polishing process is interrupted and the polishing surface is dressed. In the dressing process, since the new surface layer is exposed by removing the clogged surface layer, the polishing performance can be recovered. However, by interrupting the polishing process, the efficiency is lowered, and the polishing rate and the like change before and after the dressing process, so that stable polishing process becomes difficult. Although there is a technique to determine the wear loss of the polishing pad (polishing layer) and make the polishing pad itself dressing, it is necessary to use a specific polyol compound, and the relationship with the foam structure and the physical properties of the polishing layer is determined Therefore, the flatness of the object to be polished and the stabilization of the polishing process are not sufficient. Further, when the wear loss is increased, the hardness of the polishing layer is lowered, and on the contrary, the polishing performance is impaired. The present embodiment is a polishing pad that can solve these problems.

The present inventors diligently studied to optimize the wear loss of the polishing layer, including the relationship with the foam structure and physical properties, and found the following relationship. That is, the polishing layer formed of the polyurethane resin is formed by the reaction of the polyisocyanate compound and the polyamine compound, where R is the total equivalent ratio of the hydroxyl group of the polyol compound and the amino group of the polyamine compound to the isocyanate group of the polyisocyanate compound. When the hard segment content is HSC (%), the bulk density is D (g / cm ³ ), and the Shore A hardness is A (degrees), Formula (1), that is, F = −13.8 · The F value obtained by HSC-726 · R + 773 · D-7.95A + 1516 shows excellent correlation with the ease of abrasion of the polishing layer.

  In the urethane sheet 2 of this embodiment, F value obtained by Formula (1) exists in the range of 100-200. Since the bulk density D correlates with the foam structure of the urethane sheet 2 and the hard segment content HSC correlates with the hardness, for example, by reducing the equivalent ratio R, the foam structure and the hardness are not significantly changed. The value can be increased. In other words, even if the content rate HSC and the equivalent ratio R are changed in accordance with the characteristics of the object to be polished, the F value can be optimized by adjusting the bulk density D and the hardness A. That is, by adjusting the content ratio HSC, equivalence ratio R, bulk density D, and hardness A so as to satisfy the appropriate range of the F value obtained by the above-described formula (1), the drawbacks caused by the respective factors are compensated. Can do. For this reason, at the time of polishing of the object to be polished, since the polishing surface P is worn and regenerated as appropriate, clogging of the holes 4 and 6 is suppressed. Thereby, since the slurry is supplied to the entire processing surface while being held, the polishing performance can be stabilized.

  On the other hand, if the content HSC is too small, the openings 4 and 6 are easily clogged and the flatness of the object to be polished is lowered. On the other hand, if the content HSC is too large, it becomes brittle and tends to be hard, so that the circulation of the slurry is impaired. If the equivalent ratio R is too small, not only the flatness of the object to be polished is lowered, but also the brittleness becomes brittle, so that the durability becomes insufficient. On the other hand, if the equivalent ratio R is too large, the elasticity of the urethane sheet 2 is impaired, and the openings 4 and 6 are likely to be clogged. Further, the bulk density D correlates with the foam structure of the urethane sheet 2. That is, when the pore diameter of foam 3 or foam 5 is reduced or the number of foams is reduced, the bulk density D is increased, so that clogging is likely to occur and sufficient polishing performance such as a polishing rate can be obtained. It becomes difficult. Furthermore, if the hardness A is too low, the opening 4 and the opening 6 are likely to be clogged. On the other hand, if the hardness A is too high, scratches are likely to occur. In the present embodiment, the content ratio HSC, the equivalence ratio R, the bulk density D, and the hardness A are adjusted so as to satisfy an appropriate range of the F value obtained by the above-described formula (1). For this reason, the fault which arises by each factor can be compensated.

  Furthermore, in this embodiment, the F value obtained by Formula (1) is adjusted to the range of 100-200. For this reason, the polishing surface P side of the urethane sheet 2 is moderately worn during the polishing process, and a new polishing surface is regenerated. Therefore, clogging of the opening 4 and the opening 6 can be made difficult, and the polishing surface P is excessive. Therefore, it is possible to suppress the occurrence of polishing scratches due to the wear debris of the urethane sheet 2. The polishing pad 1 using such a urethane sheet 2 can be suitably used for primary polishing of a silicon wafer.

  Furthermore, in this embodiment, when a prepolymer, a dispersion liquid, and a polyamine compound are mixed in the mixing step, a non-reactive gas is blown to prepare a mixed liquid. For this reason, fine bubbles are generated by the non-reactive gas, and the water in the dispersion liquid is substantially uniformly dispersed in the mixed liquid by the bubbling effect of the bubbles. Since water is dispersed and diluted in advance in the polyol compound and the dispersion is dispersed in the mixture with bubbles generated by the non-reactive gas, the dispersion state of water in the mixture can be equalized. Thereby, the carbon dioxide generated by the reaction of water and the isocyanate group of the prepolymer is also dispersed substantially uniformly. Moreover, although a part of non-reactive gas produces a large bubble, similarly, it is disperse | distributed substantially uniformly in a liquid mixture by a fine bubble. Therefore, the foam 3 and the foam 5 can be formed in the polyurethane foam to be obtained, the sizes of which are controlled and substantially uniformly dispersed. By slicing in the slicing step, a plurality of urethane sheets 2 having substantially uniform openings 4 and 6 formed on the surface thereof can be obtained, and a plurality of polishing pads using the urethane sheet 2 can be obtained. 1, variation in polishing performance can be suppressed.

  Furthermore, in this embodiment, the amount of water dispersed in the mixed liquid is limited by setting the amount of water in the dispersion to a ratio of 1 to 6 g with respect to 1 kg of the weight of the prepolymer. In addition, the formation and unevenness of large foam can be suppressed. Thereby, in the plurality of sliced urethane sheets 2, the average hole diameter of the openings 4 can be in the range of 30 to 200 μm, and the hole diameter of the openings 6 can be in the range of 500 to 2000 μm. Therefore, since polishing slurry is accommodated in the opening 4 and the opening 6 while the slurry is held in the opening 4 and the opening 6 at the time of polishing, the polishing efficiency can be improved. Moreover, the quantity of non-reactive gas in a liquid mixture is restrict | limited by making the quantity of non-reactive gas into the ratio of 0.5-3.4L with respect to 1 kg of total weight of a prepolymer, a dispersion liquid, and a polyamine compound. Therefore, it is possible to suppress formation of extremely large foam and form foam 3 and foam 5. Further, by setting the viscosity of the prepolymer at a temperature of 50 to 80 ° C. in the range of 2000 to 20000 mPa · s, the bubbling effect due to the non-reactive gas is generated almost uniformly, and the dispersion state of water in the mixed liquid is equalized. be able to. Thereby, the deviation of the foam 3 and the foam 5 can be suppressed, and the dispersed state can be equalized.

  In this embodiment, the polyol compound blended in the dispersion plays a role of facilitating dispersion of water in the mixed solution. However, since the polyol compound exists in the mixed solution, some of the hydroxyl groups of the polyol compound are present. By reacting with the isocyanate group of the prepolymer, it also plays a role of making it difficult to change the hardness of the polyurethane foam in a wet state. For this reason, in the plurality of urethane sheets 2 to be obtained, the wet hardness retention rate is 85% or more. In particular, wet hardness retention can be improved by using PTMG as the polyol compound. Accordingly, since the thermal stability in a wet state is improved, even if heat is generated due to friction or the like during polishing using a slurry, the change in hardness of the polishing pad 1 (urethane sheet 2) is suppressed, and the polishing performance is stabilized. Can be planned.

  In the present embodiment, no specific compound is specifically exemplified, but a triisocyanate compound may be blended with the polyisocyanate compound used for preparing the prepolymer. As described above, when the equivalent ratio R is decreased, the dimensional stability of the obtained polyurethane foam is lowered. However, by adding a triisocyanate compound, the polyurethane foam is hardened and easily worn. Therefore, the F value can be increased without reducing the equivalent ratio R. In this case, the ratio of the triisocyanate compound to be blended is preferably about 0.3 to 0.8 by weight ratio. The polyisocyanate compound preferably contains tolylene diisocyanate, and the blending ratio is preferably at least 50% by weight. Furthermore, although the example which uses PTMG for the polyol compound used for preparation of a prepolymer was shown, you may mix and use polyol compounds other than PTMG. In this case, the blending ratio of PTMG is preferably at least 50% by weight.

  Furthermore, in this embodiment, although the isocyanate terminal urethane prepolymer which made the polyol compound and the diisocyanate compound react was illustrated as a prepolymer, this invention is not limited to this. For example, an active hydrogen compound having a hydroxyl group, an amino group or the like may be used instead of the polyol compound, and a polyisocyanate compound or a derivative thereof may be used instead of the diisocyanate compound, and these may be reacted. In addition, since various kinds of isocyanate-terminated prepolymers are commercially available, commercially available products can be used. Moreover, in this embodiment, although the example which prepares the dispersion liquid which disperse-diluted water in the polyol compound was shown, this invention is not limited to this, For example, a dispersion liquid other than a polyol compound and water, You may make it contain components, such as an additive and a filler required in the case of hardening molding. In this dispersion, since water is dispersed in the polyol compound not involved in foaming, it plays a role of reducing water mixing spots in the mixing step. Although it is possible to use a liquid other than the polyol compound, it is preferable to use a polyol compound in view of the possibility that such a liquid may be eluted during polishing and adversely affect the polishing characteristics.

Furthermore, in this embodiment, the F value obtained by the formula (1) is in the range of 100 to 200, the content HSC is in the range of 32 to 42%, the equivalent ratio R is in the range of 0.7 to 0.9, and the bulk. Although an example in which the density D is in the range of 0.45 to 0.55 g / cm ³ and the hardness A is 85 degrees or more is shown, the present invention is not limited to these. These ranges are preferable because the polishing pad 1 is used for primary polishing of a silicon wafer, but may be appropriately changed depending on characteristics of an object to be polished and required polishing accuracy.

  Furthermore, although not particularly mentioned in the present embodiment, the polishing surface P may be subjected to grooving or embossing in consideration of supply of slurry and discharge of polishing debris. The shape of the groove may be any of a radial shape, a lattice shape, and a spiral shape, and the cross-sectional shape may be any of a rectangular shape, a U shape, a V shape, and a semicircular shape. The pitch, width, and depth of the grooves are not particularly limited as long as the polishing waste can be discharged and the slurry can be moved. Of course, embossing is not particularly limited.

  Although not particularly mentioned in the present embodiment, the urethane sheet 2 has at least a light transmitting portion that allows light transmission for optically detecting the polishing state of the object to be polished. It may be. In this case, it is preferable that the light transmission part is formed so as to penetrate through the entire thickness direction of the urethane sheet 2. In this way, for example, a light-emitting element such as a light-emitting diode provided on the polishing machine side or a light-receiving element such as a phototransistor detects the polishing state of the processing surface of the object to be polished through the light transmitting part during polishing can do. As a result, the end point of the polishing process can be properly detected, and the polishing efficiency can be improved.

  Furthermore, in this embodiment, although the example which uses the mixer 20 in a mixing process and a slicing machine in a slicing process was shown, there is no restriction | limiting in particular in a mixer or a slicing machine, and the mixer and slicing machine which are normally used are used. Can be used. In the present embodiment, the rectangular parallelepiped mold 25 is illustrated, but the present invention is not limited to the shape and size of the mold. For example, a cylindrical form or the like may be used, and the foam may be formed without using the form if the viscosity of the mixed liquid is taken into consideration.

  Hereinafter, examples of the polishing pad 1 manufactured according to the present embodiment will be described. A comparative example prepared for comparison is also shown.

Example 1
In Example 1, 279 parts of 2,4-tolylene diisocyanate (2,4-TDI), 284 parts of PTMG having a number average molecular weight of about 1000, and 64 parts of diethylene glycol were reacted as a first component prepolymer. Using a terminal isocyanate group-containing urethane prepolymer in an amount of 9.6%, this was heated to 55 ° C. and degassed under reduced pressure. The second component MOCA was dissolved at 120 ° C. and degassed under reduced pressure. The third component dispersion is 50 parts of PTMG having a number average molecular weight of about 1000, 2 parts of water, 1 part of a catalyst (Toyocat ET, manufactured by Tosoh Corporation), a silicon-based surfactant (SH-193, 5 parts of Dow Corning) were added and stirred and mixed, and then degassed under reduced pressure. That is, in Example 1, as shown in Table 1 below, the content rate HSC is 39% and the equivalent ratio R is 0.7. The 1st component: 2nd component: 3rd component was supplied to the mixing tank 12 by the ratio of 100 parts: 10 parts: 5 parts by weight ratio. In the mixing step, the stirring conditions were set to a shear rate of 1689 times and a shear rate of 9425 / second. At this time, air was supplied into the mixing tank 12 at a flow rate of 80 L / min. After the obtained mixed liquid was cast into a mold 25 and cured, the formed polyurethane foam was extracted from the mold 25. This foam was sliced to a thickness of 1.3 mm to produce a urethane sheet 2 and a polishing pad 1 was obtained.

(Example 2)
In Example 2, 463 parts of 2,4-TDI as a prepolymer of the first component, 10 parts of triisocyanate to be a trimer of 2,4-TDI, 476 parts of PTMG having a number average molecular weight of about 1000, diethylene glycol A urethane sheet 2 was produced in the same manner as in Example 1 except that a terminal isocyanate group-containing urethane prepolymer having an isocyanate content of 9.5% reacted with 107 parts was obtained, and a polishing pad 1 was obtained. As shown in Table 1, in Example 2, the content HSC is 39% and the equivalent ratio R is 0.7.

(Comparative Example 1)
In Comparative Example 1, 270 parts of 2,4-TDI as a prepolymer of the first component, 292 parts of PTMG having a number average molecular weight of about 1000, and terminal isocyanate having an isocyanate content of 8.7% obtained by reacting 65 parts of diethylene glycol Example 1 was used except that a group-containing urethane prepolymer was used and the first component: second component: third component was supplied to the mixing tank 12 at a ratio of 100 parts: 21 parts: 5.5 parts by weight. Then, a urethane sheet was produced to obtain a polishing pad. As shown in Table 1, in Comparative Example 1, the content rate HSC is 36%, and the equivalent ratio R is 0.9.

(Evaluation 1)
About each Example and the comparative example, the bulk density D of the urethane sheet, the hole diameter of the hole 4, and the hole distribution of the hole 6 were measured. The bulk density D was calculated from the volume obtained by measuring the weight of a sample cut into a predetermined size. The pore diameter was observed with a microscope (manufactured by KEYENCE, VH-6300) by enlarging the range of about 1.3 mm by 175 times, and the obtained image was image processing software (Image Analyzer V20LAB Ver. 1.3). Processed and calculated. In addition, the opening 6 was observed with a microscope (manufactured by KEYENCE, VH-6300) with a 10-fold magnification of the 3.0 cm square area, and the variation in the number of openings over 500 μm CV% = standard Deviation ÷ average value × 100 was determined. For the urethane sheet, the Shore A hardness was measured in accordance with Japanese Industrial Standard (JIS K 7311) to obtain the hardness A. Table 2 below shows the bulk density D, the average pore diameter of the apertures 4, the CV% of the apertures 6, the result of the hardness A, and the F value obtained by the formula (1).

  As shown in Table 2, in Comparative Example 1, the CV% of the opening 6 was higher than that in Example 1 and Example 2, and thus it was found that the distribution of the opening 6 was uneven. The F value at this time was a low value of 74. Compared to this, in Example 1 and Example 2, it was found that there was less variation in the distribution of the apertures 6 than in the comparative example.

(Evaluation 2)
Next, with respect to the polishing pads of the examples and comparative examples, the wear loss was measured according to the abrasion resistance A method in Japanese Industrial Standard (JIS K6902 “Testing Method for Thermosetting Resin High Pressure Decorative Board”). The wear loss was measured when the number of polishing was 1000 times. The measurement results of wear loss are shown in Table 3 below.

  As shown in Table 3, the polishing pad of Comparative Example 1 has a low wear loss, and it was confirmed that most of the openings 4 were clogged after the evaluation. On the other hand, it was confirmed that the polishing pads of Example 1 and Example 2 had moderate wear loss, and the clogging of the aperture 4 after evaluation was less than that of Comparative Example 1. Moreover, it became clear that the abrasion loss which repeated 1000 times grinding | polishing of Example 1, Example 2, and the comparative example 1 exists in the approximate range to F value of Formula (1).

(Evaluation 3)
Moreover, using the polishing pad of each Example and Comparative Example, the aluminum substrate for hard disks was polished under the following polishing conditions, and the polishing rate was measured. The polishing rate is the amount of polishing per minute expressed by thickness, and was calculated from the polishing amount obtained from the weight reduction of the aluminum substrate before and after polishing, the polishing area of the aluminum substrate, and the specific gravity. Moreover, the presence or absence of the scratch was determined visually. The measurement results of the polishing rate and scratch are shown in Table 4 below.
(Polishing conditions)
Polishing machine used: Speedfam, 9B-5P polishing machine Polishing speed (rotation speed): 30 rpm
Processing pressure: 100 g / cm ²
Slurry: Colloidal silica slurry (pH: 11.5)
Slurry supply amount: 100cc / min
Workpiece: Aluminum substrate for hard disk (outer diameter 95mmφ, inner diameter 25mm, thickness 1.27mm)

  As shown in Table 4, in Comparative Example 1, the polishing rate was low, and the occurrence of scratches was also confirmed. On the other hand, in Example 1 and Example 2, it was found that the polishing rate was higher than that of Comparative Example 1 and there was no occurrence of scratches.

  From the above results, in Example 1 and Example 2, the F value obtained by the formula (1) is within the above-described range, the distribution variation of the apertures 6 is small, and appropriate wear loss is shown. It has been clarified that the opening 4 is not easily clogged, exhibits a good polishing rate, and can suppress generation of scratches.

  The present invention contributes to the manufacture and sale of polishing pads in order to provide a polishing pad manufacturing method that can optimize the degree of wear and stabilize the polishing performance, and thus has industrial applicability.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is process drawing which shows the principal part of the manufacturing method of the polishing pad of embodiment. It is a block diagram which shows the outline of the mixer and mold which were used for manufacture of the polishing pad of embodiment.

Explanation of symbols

P Polishing surface 1 Polishing pad 2 Urethane sheet 3, 5 Foam 4, 6 Open hole

Claims (15)

A preparation step of preparing each component of a polyisocyanate compound, a polyol compound, a polyamine compound and water;
From an isocyanate group-containing compound obtained by reacting the polyisocyanate compound and the polyol compound prepared in the preparation step in advance, the polyamine compound, the water, and a mixture of non-reactive gases with respect to the components. A foam forming step for forming the foam;
A polishing layer forming step of forming a polishing layer having a polishing surface for polishing a workpiece from the foam formed in the foam forming step;
Including
Reaction of the isocyanate group-containing compound and the polyamine compound obtained in the foam formation step, where R is the total equivalent ratio of the hydroxyl group of the polyol compound and the amino group of the polyamine compound to the isocyanate group of the polyisocyanate compound prepared in the preparation step HSC (%) is the hard segment content formed in the above, the bulk density of the polishing layer formed in the polishing layer forming step is D (g / cm ³ ), and the Shore A hardness is A (degrees). In addition, each component prepared in the preparation step and the foam formation so that the F value obtained by F = -13.8.HSC-726.R + 773.D-7.95A + 1516 is in the range of 100 to 200. A method for producing a polishing pad, comprising adjusting the amount of the gas mixed in the step.   In the preparation step, the amount of the polyisocyanate compound, the polyol compound, and the polyamine compound to be prepared is adjusted so that the equivalent ratio R is in a range of 0.7 to 0.9. The manufacturing method as described.   The amount of mixing the isocyanate group-containing compound and the polyamine compound is adjusted in the foam formation step so that the content rate HSC is in a range of 32% to 42%. Production method. In the foam formation step, the amount of water and gas mixed is adjusted so that the bulk density D is in the range of 0.45 g / cm ^{3 to} 0.55 g / cm ^3. 2. The production method according to 1.   2. The manufacturing method according to claim 1, wherein the amount of each component prepared in the preparation step and the amount of gas mixed in the foam formation step are adjusted so that the hardness A is 85 degrees or more. .   The production method according to claim 5, wherein the polyisocyanate compound prepared in the preparation step includes at least 50% by weight of tolylene diisocyanate.   6. The production method according to claim 5, wherein the polyol compound prepared in the preparation step contains at least 50% by weight of polytetramethylene ether glycol.   2. The production method according to claim 1, wherein the isocyanate group-containing compound obtained in the foam forming step has a viscosity at a temperature of 50 ° C. to 80 ° C. in a range of 2000 mPa · s to 20000 mPa · s.   9. The method according to claim 8, wherein the water prepared in the preparation step is dispersed in advance in the polyol compound at a ratio of 1% by weight to 6% by weight.   5. The production method according to claim 4, wherein the amount of water prepared in the preparation step is a ratio of 1 g to 6 g with respect to 1 kg of the weight of the isocyanate group-containing compound obtained in the foam formation step.   The amount of gas mixed in the foam forming step is a ratio of 0.5 L to 3.4 L with respect to 1 kg of the total weight of the isocyanate group-containing compound, polyamine compound and water, according to claim 4. The manufacturing method as described.   9. The manufacturing method according to claim 8, wherein, in the foam forming step, the mixed solution is prepared under a mixing condition of a shear rate of 9,000 to 41,000 / second and a shearing number of 300 to 10,000. .   The manufacturing method according to claim 1, wherein the polishing layer formed in the polishing layer forming step is subjected to grooving or embossing on the polishing surface side.   The light transmitting portion that allows light transmission for optically detecting a polishing processing state during polishing processing is formed on at least a part of the polishing layer formed in the polishing layer forming step. 2. The production method according to 1.   The manufacturing method according to claim 14, wherein the light transmission part is formed over the entire thickness direction of the polishing layer.

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