JP2010090258A - Method for selecting polishing sheet for polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for selecting a polishing sheet for a polishing pad, so as to appropriate a wear degree and stabilize polishing performances while taking the lifetime into consideration. <P>SOLUTION: The polishing pad has a urethane sheet of a foamed structure having a polishing face. The urethane sheet is selected from sheets prepared by slicing a foamed material comprising a mixture of a polyisocyanate compound, a polyol compound, water and a polyamine compound. A sheet having an F value, which is defined by F=-36.7×HSC-758.8×R+656×D-619×T+2,587, in a range from 100 to 200 is selected as a favorable product. In the above definition, HSC represents a content rate of a hard segment, R represents an equivalent ratio of the total of hydroxy groups in the polyol compound and amino groups in the polyamine compound with respect to isocyanate groups of the polyisocyanate compound, D represents bulk density and T represents a thickness. The F value correlates with easiness of wear on the polishing face while taking the lifetime into consideration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for selecting a polishing sheet for a polishing pad, and more particularly to a selection method for selecting a polishing sheet for a polishing pad from a plurality of sheets prepared by mixing a polyisocyanate compound, a polyol compound, a polyamine compound and water.

  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 have progressed for the purpose of higher density, 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 the 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 chemical mechanical polishing (hereinafter abbreviated as CMP) method is used for manufacturing a semiconductor device. In the CMP method, a so-called free abrasive grain method is generally employed in which a slurry (polishing liquid) in which abrasive grains (polishing particles) are dispersed in an alkali solution or an acid solution is supplied during polishing. That is, the object to be polished (the processed surface thereof) is flattened by the mechanical action by the abrasive grains in the slurry and the chemical action by the alkali solution or the acid solution. With the advancement of flatness required for the processed surface, polishing characteristics such as polishing accuracy and polishing efficiency required for the CMP method, in other words, performance required for the polishing pad is also increasing.

  A polishing pad used in the CMP method includes a polishing sheet 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 a processed surface of an object to be polished. The polishing sheet has a foamed structure, and an opening is formed in the polishing surface by grinding treatment or the like, so that the slurry supplied during polishing is held in the opening, and the gap between the polishing surface and the processing surface is maintained. The slurry is discharged almost evenly. Further, in order to improve the supply of slurry and the ability to discharge polishing scraps generated by the polishing process, the polishing surface may be subjected to groove processing or the like.

  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. On the contrary, the elasticity of the polishing sheet 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.

  On the other hand, when clogging occurs in the opening of the polished surface, the polishing process is interrupted, and the polishing surface is dressed, that is, the clogged surface layer is removed to expose the new surface layer, thereby improving the polishing performance. It is also possible to recover. 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 technology in which the weight loss (degree of wear) by the Taber abrasion test is 150 to 350 mg is disclosed (see Patent Document 1). Further, by adding polyether polyol, polyester polycarbonate polyol or polycarbonate polyol as an alkali-resistant polyol compound in an amount of 50% by weight or more based on the total polyol compound, the polishing sheet is adjusted to 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 (see Patent Document 2).

JP 2001-277101 A Japanese Patent No. 3570681

  However, in the technique of Patent Document 1, 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 the two types of prepolymers are likely to occur, the foamed structure is non-uniform, and the pore diameter on the polished surface becomes large, so that there is a problem of low hardness and the abrasive sheet being 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 rate becomes large. It is enough. Further, the technique of Patent Document 2 has a problem that although the change in the polishing rate and the like is reduced by improving the alkali resistance, the wear loss itself is insufficient, and 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 appropriately abrading the polishing surface during polishing, but if the wear loss becomes too large, inconveniences such as scratches may occur due to wear debris of the polishing pad (polishing sheet). For this reason, it is important to optimize the weight loss according to the object to be polished.

  An object of the present invention is to provide a selection method for selecting a polishing sheet for a polishing pad that can optimize the degree of wear and stabilize the polishing performance in consideration of the lifetime.

In order to solve the above-mentioned problems, the present invention slices a foam formed from a mixed liquid obtained by mixing an isocyanate group-containing compound obtained by reacting a polyisocyanate compound and a polyol compound, a polyamine compound, and water. A selection method for selecting a polishing sheet for a polishing pad having a polishing surface for polishing an object to be polished from a plurality of sheets produced by cutting, wherein the polyol for the isocyanate group of the polyisocyanate compound The total equivalent ratio of the hydroxyl group of the compound and the amino group of the polyamine compound is R, the hard segment content formed by the reaction of the isocyanate group-containing compound and the polyamine compound is HSC (%), and the bulk of the sheet the density D (g / ^cm 3), when the thickness was T (mm) Characterized in that the F value obtained by F = -36.7 · HSC-758.8 · R + 656 · D-619 · T + 2587 is for sorting sheets ranging from 100 to 200 non-defective of the abrasive sheet.

  In the present invention, the bulk density D correlates with the foam structure of the sheet prepared by mixing water, the content HSC correlates with the hardness and brittleness of the sheet, the equivalent ratio R, and the thickness T correlates with the life. Since the F value represents the ease of wear in consideration of the life of the sheet, each polishing sheet was used as a polishing pad by selecting sheets having an F value in the range of 100 to 200 as non-defective polishing sheets. At times, the degree of wear is optimized in accordance with the object to be polished, so that the polishing performance can be stabilized by the thickness T, and the performance variation among a plurality of polishing pads using a good polishing sheet can be achieved. Can be suppressed.

  In this case, a plurality of sheets produced by slicing and cutting the foam are made into one group, and a group in which the difference between the maximum value and the minimum value of the F values is 50 or less is selected as a non-defective product. Also good. Sheets prepared by slicing and cutting foam may be prepared by adjusting the amounts of polyisocyanate compound, polyol compound and polyamine compound such that the equivalent ratio R is in the range of 0.7 to 0.9. preferable. At this time, it is preferable that the amount of the isocyanate group-containing compound and the polyamine compound is adjusted so that the sheet has a content ratio HSC of 32% to 42%. The polyisocyanate compound may contain at least 50% by weight of tolylene diisocyanate. At this time, the polyol compound may contain at least 50% by weight of polytetramethylene ether glycol.

  According to the present invention, the bulk density D correlates with the foam structure of the sheet prepared by mixing water, the content ratio HSC correlates with the hardness and brittleness of the sheet, the equivalent ratio R, and the thickness T correlates with the lifetime. Since the F value obtained represents the ease of wear taking into account the life of the sheet, each polishing sheet is used as a polishing pad by selecting a sheet with an F value in the range of 100 to 200 as a good polishing sheet. When used, the degree of wear is optimized according to the object to be polished, so that it is possible to stabilize the polishing performance by the thickness T and between a plurality of polishing pads using a good polishing sheet. An effect that performance variation can be suppressed can be obtained.

  Hereinafter, an embodiment of a polishing pad provided with a polishing sheet selected by applying the present invention and used for polishing by a CMP method will be described with reference to the drawings.

(Polishing pad)
As shown in FIG. 1, the polishing pad 1 of this embodiment includes a urethane sheet 2 as a polishing sheet made of polyurethane resin. The urethane sheet 2 has a polishing surface P for polishing an object to be polished. The urethane sheet 2 is a mixed liquid in which 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, and a polyamine compound. It is formed by slicing and cutting a polyurethane foam cast and cured in a frame. That is, the urethane sheet 2 constituting the polishing pad 1 is formed by dry molding.

  Inside the urethane sheet 2, foam 6 having a circular or elliptical cross section is formed in a substantially uniform manner by water in the dispersion during dry molding. That is, the polyurethane sheet 2 has a foam structure. The foam 6 is formed in the range of 20 to 60 μm with an average pore diameter of 100 μm or less. Since the urethane sheet 2 is formed by slicing a polyurethane foam, a part of the foam 6 is opened on the polishing surface P, and an opening 4 is formed. Since the opening 4 is formed by the opening of the foam 6, the average hole diameter of the opening 4 is in the range of 20 to 60 μm. The thickness of the urethane sheet 2 is set in the range of 0.5 to 2.0 mm.

The urethane sheet 2 is obtained from a plurality of sheets obtained by slicing and cutting polyurethane foam, and F = −36.7 · HSC−758.8 · R + 656 · D−619 · T + 2587 (hereinafter referred to as the formula (1)) The sheet having the F value in the range of 100 to 200 obtained in (1) is selected. 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. Is the total equivalent ratio of the hydroxyl group of the polyol compound and the amino group of the polyamine compound to D, D is the bulk density (g / cm ³ ) of the urethane sheet 2, and T is the thickness (mm) of the urethane sheet 2. .

  Here, each factor in the formula (1), that is, the content ratio HSC, the equivalent ratio R, the bulk density D, and the thickness T 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. The flatness of the polished product may be reduced. 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 formed. In other words, the content HSC can be adjusted by the compounding ratio of each compound used at the time of formation. 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 rate HSC can be obtained even after the urethane sheet 2 is formed.

  In addition, 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 forming the urethane sheet 2 as in the case of the content rate HSC. It can also be calculated. If the equivalent ratio R is too small, unreacted isocyanate groups are likely to remain. Therefore, in the formed 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 contrary, 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, so that stickiness is generated and the opening 4 is easily clogged. 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 the foam 6 is too small or the number of foams is too small, the bulk density D increases. When the hole diameter of the foam 6 is reduced, the opening 4 is also reduced, so that clogging is likely to occur. When the number of foams is reduced, the number of the openings 4 is also reduced, and it is difficult to obtain sufficient polishing performance such as a polishing rate. Become. 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 varies depending on the equivalent ratio R, the content ratio HSC, and the bulk density D. In addition to these, the average polymerization degree and molecular weight distribution of the polyurethane resin constituting the urethane sheet 2 and the shape and distribution of the pores are also affected. It is important to take account of these variations as they can change. If the hardness is too low, the urethane sheet 2 is too soft, so that not only the flatness of the object to be polished is impaired, but also stickiness is likely to occur, and the opening 4 is likely to be clogged. On the other hand, if the hardness is too high, scratches are likely to occur. In this example, the Shore A hardness is adjusted to be 85 degrees or more as the hardness. This is equivalent to 60 degrees or less if expressed by Shore D hardness. The bulk density D and hardness can be adjusted by changing the size and quantity of the foam 6, in other words, changing the amount of water in the dispersion, although it depends on the material of the polyurethane resin.

  Further, the thickness T correlates with the life of the polishing pad 1. That is, if the thickness T is too small, it wears out relatively early and the life is shortened. On the other hand, if the thickness T is too large, deformation due to pressing (polishing pressure) at the time of polishing increases, and on the contrary, the flatness of the object to be polished is impaired. For this reason, in this example, the thickness T is set in the range of 0.5 to 2.0 mm.

  As described above, the content ratio HSC, the equivalent ratio R, and the bulk density D in the urethane sheet 2 are each related to the degree of wear and ease of clogging of the urethane sheet 2, and the thickness T is related to the life. . 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 while considering the life of the urethane sheet 2. This F value is determined by following a method according to the Taber abrasion test of Japanese Industrial Standard (JIS K 6902, abrasion resistance A method). This corresponds to a weight loss (mg) per 1000 rotations on the polishing surface P when the polishing surface P is brought into contact with the attached wear wheel and rotated. In the urethane sheet 2, the amount of the polyisocyanate compound, the polyol compound, the polyamine compound, and water described above is 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 polishing by the CMP method. 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, hardness, and thickness T even if the content ratio HSC and the equivalent ratio R are changed in accordance with the characteristics of the object to be polished. That is, by adjusting the content rate HSC, the equivalence ratio R, the bulk density D, and the thickness T so as to satisfy the range of the F value obtained by the above-described formula (1), the drawbacks caused by the respective factors can be compensated. it can. As a result, at the time of polishing the object to be polished, the polishing surface P is worn and regenerated timely, and clogging of the opening 4 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 of preparing a polyisocyanate compound, a polyol compound, a dispersion obtained by dispersing and diluting water in a polyol compound, and a polyamine compound, respectively, reacting a polyisocyanate compound and a polyol compound in advance to produce an isocyanate group-containing compound A mixing step of preparing and mixing the obtained isocyanate group-containing compound, dispersion, and polyamine compound, and then pouring the mixture into a mold and foaming and curing in the mold to form a polyurethane foam Curing and forming step to form, Slicing and cutting step of slicing and cutting polyurethane foam into a sheet to form a plurality of sheets, F value is calculated for the obtained plurality of sheets, and F value is in the range of 100 to 200 F-number calculation / sorting process to sort the sheet as a good product of urethane sheet 2, sorted good product It is produced through a laminating process for 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. In consideration of adjusting the hardness of the urethane sheet 2 to the above-described range, it is preferable that at least 50% by weight of 2,6-TDI or 2,4-TDI tolylene diisocyanate is contained.

  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 such as polytetramethylene ether glycol (PTMG). Any of a high molecular weight polyol compound such as a compound, a reaction product of ethylene glycol and adipic acid, a polyester polyol compound such as a reaction product of butylene glycol and adipic acid, a polycarbonate polyol compound, and a polycaprolactone polyol compound can be used. . Two or more of these polyol compounds may be used in combination. In consideration of adjusting the ratio of the soft segment of the urethane sheet 2 and adjusting the content rate HSC to the above-described range, it is preferable that PTMG is contained at least 50% by weight.

  Moreover, since the polyol compound used for the preparation of the dispersion reacts with the isocyanate group of the isocyanate group-containing compound to form a soft segment, it is possible to suppress elution during polishing and thus adverse effects on the polishing characteristics. In the dispersion liquid, water is dispersed in a polyol compound that does not participate in foaming, and thus plays a role of reducing mixed spots of water in the subsequent mixing step. 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 polyol compounds can be used. Since it becomes easy to homogenize water dispersion in the mixing step by setting the viscosity to the same level as the viscosity of the isocyanate group-containing compound 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 0.01 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 be a ratio of 0.01-6g with respect to 1 kg of the weight of the isocyanate group containing compound 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 isocyanate group-containing compound is 1 kg and the dispersion is 100 g, the amount of water contained in this dispersion is 0.01 to 6 g.

  A polyamine compound forms a hard segment by reacting with an isocyanate group of an isocyanate group-containing compound. 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, 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. The obtained prepolymer is mixed with the dispersion and polyamine compound prepared in the preparation step to prepare a mixed solution. In the curing molding process, the mixed liquid prepared in the mixing process is poured into a mold, and foamed and cured in the mold to mold a polyurethane foam. In this example, the mixing process and the 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 6 formed in the polyurethane foam obtained by producing the 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 6 dispersed almost uniformly 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 curing molding step, the prepared mixed solution is continuously cast from the mixer 20 into a mold 25 and cured to form polyurethane. A 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 supply tank containing a prepolymer as the first component, a polyamine compound as the second component, and a dispersion as the third component is disposed. The supply port from each supply tank is connected to the upstream end of the mixing tank 12. The stirring blade 14 is fixed to a rotating shaft extending 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, and the first component, the second component, and the third component are sheared and mixed. 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). Since 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, each supply tank is added so that each component can flow. It is warm.

  The first component, the second component, and the third component are supplied to the mixing tank 12 and mixed, but since the viscosity of each component is adjusted to the same level, the temperature of the solution in which each component is mixed is 50 to 80 ° C. The viscosity is in the range of 2000 to 20000 mPa · s. By adjusting the shearing speed and the number of times of shearing of the stirring blade 14, the components are mixed substantially uniformly to prepare a mixed solution. If the shear rate of the stirring blade 14 is too low, the size of the foam 6 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 Variation in the dispersed state of the foam 6 formed in the foam tends to occur. On the other hand, if the number of times of shearing is too small, the size of the generated bubbles tends to be uneven (dispersion). On the other hand, if the number of shearing is too large, the viscosity decreases as the temperature rises, and the foam 6 is not formed substantially uniformly. 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.

  When the mixed liquid is poured into the mold 25 in the curing molding process, the mixed liquid from the mixer 20 is discharged from the discharge port of the mixing tank 12 and, 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. The injected liquid mixture 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 6 is formed.

(Slicing and cutting process)
As shown in FIG. 2, in the slicing / cutting step, the polyurethane foam obtained in the curing molding step is sliced into a sheet shape and cut into a desired shape and size such as a circle to form a plurality of sheets. 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 the range of 0.5 to 2.0 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. Sliced into 15-60 sheets. At the time of cutting, it may be punched with a mold having a desired shape, or may be cut with a cutting machine. Since a polyurethane foam in which the foam 6 is substantially uniformly formed inside is obtained in the curing molding process, the average pore diameter of the openings 4 formed on the surface of the plurality of sheets formed in the slicing / cutting process is increased. Is in the range of 20 to 60 μm, which is 100 μm or less. When the average pore diameter of the apertures 4 exceeds 100 μm, it becomes difficult to control the substantially uniform pore diameter. On the other hand, when the average pore diameter is less than 20 μm, the slurry is easily clogged during the polishing process, and the life of the polishing pad is likely to be reduced.

(F value calculation / selection process)
In the F value calculation / selection step, the bulk density D and the thickness T are measured for each of the plurality of sheets obtained in the slicing / cutting step. At this time, by using the cut piece at the time of cutting as a measurement sample, it is possible to avoid (contact) measurement with a non-defective sheet that can be a product. The bulk density D is calculated from the volume obtained from the size and the measured weight by measuring the weight of the sample cut into a predetermined size. The thickness T is measured using a dial gauge and applying a load of 100 g / cm ² . On the other hand, the average molecular weight Mdi, Mg, Mda per each bifunctionality is determined by the polyisocyanate compound, polyol compound and polyamine compound used for the production of the prepolymer, and the equivalent amount of the mixed polyisocyanate compound and the amount of the polyol compound is equivalent. The ratio r is obtained. From these numerical values, the hard segment content HSC is obtained by the above-described equation (2). Moreover, the equivalent ratio R is calculated | required from each quantity of the mixed polyisocyanate compound, a polyol compound, and a polyamine compound.

  From the measured bulk density D and thickness T, and the obtained content ratio HSC and equivalent ratio R, the F value is calculated for each of a plurality of sheets by the above-described equation (1). Those having a calculated F value in the range of 100 to 200 are determined as non-defective products and selected as the urethane sheet 2.

(Lamination process)
In the laminating process, the non-defective urethane sheet 2 selected in the F value calculation / selecting process and the double-sided tape are bonded together. Then, the polishing pad 1 is completed by performing an inspection such as confirming that there is no adhesion of dirt or foreign matter.

  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 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 opening 4 is polished without clogging. 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 focusing on a method for selecting the urethane sheet 2 that constitutes the polishing pad 1.

  In the conventional polishing process by the CMP method, a polishing pad having a foamed structure and having a hole formed in the polishing surface is used. At the time of polishing, a polishing liquid (slurry) containing abrasive particles is supplied between the object to be polished and the polishing pad, and this polishing liquid is held in the openings formed on the polishing surface and the entire processed surface of the object to be polished The object to be polished is polished by being supplied to. However, the opening may be clogged with abrasive particles or polishing debris generated during polishing. When clogging of the holes occurs, not only does the processing surface have polishing scratches, but the flatness is deteriorated, 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 sheet) and to give the polishing pad itself dressing properties, it is necessary to use a specific polyol compound, and the relationship between the foam structure and the physical properties of the polishing sheet 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 sheet decreases, and on the contrary, the polishing performance is impaired.

The present inventors diligently studied to optimize the wear loss of the abrasive sheet including the relationship with the foam structure and physical properties, and found the following relationship. That is, a polishing sheet formed of a polyurethane resin is formed by the reaction of a polyisocyanate compound and a 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 thickness is T (mm), Formula (1), that is, F = −36.7 · HSC— F value obtained by 758.8 * R + 656 * D-619 * T + 2587 is to show excellent correlation with the ease of abrasion of the abrasive sheet. In other words, as described above, such an F value is obtained by bringing the polishing surface P into contact with a wear ring in which abrasive paper having a grain size of 63 to 100 μm attached to the surface is attached to the outer periphery. This corresponds to a weight loss (mg) per 1000 rotations on the polishing surface P when rotated.

  In the urethane sheet 2 constituting the polishing pad 1 of the present embodiment, those having an F value in the range of 100 to 200 obtained by the formula (1) are selected as non-defective products. Since the bulk density D correlates with the foam structure of the urethane sheet 2, the hard segment content HSC affects the hardness, and the thickness T correlates with the life, for example, by reducing the equivalent ratio R, the foam structure The F value can be increased without significantly changing the service life. 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 thickness T. That is, by adjusting the content ratio HSC, the equivalent ratio R, the bulk density D, and the thickness T so as to satisfy the appropriate range of the F value obtained by the above-described formula (1), the defect caused by each factor is compensated. Can do. For this reason, at the time of polishing of an object to be polished, clogging of the opening 4 is suppressed because the polishing surface P is worn and regenerated in a timely manner. Thus, since the slurry is supplied to the entire processing surface while being held, the polishing performance can be stabilized by the thickness T.

  On the other hand, if the content HSC is too small, stickiness due to low crystallinity tends to occur and the hardness tends to be insufficient, so that the opening 4 is likely to be 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 hard because of its high crystallinity, so that the circulation of the slurry is impaired. When the equivalence ratio R is too small, the dimensional stability is lowered as described above, so that 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 contrary, if the equivalent ratio R is too large, the elasticity of the urethane sheet 2 is impaired, so that stickiness is generated and the opening 4 is 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 the foam 6 is reduced or the number of foams is reduced, the bulk density D is increased, so that clogging is likely to occur. When the hole diameter of the foam 6 is reduced, the opening 4 is also reduced, so that clogging is likely to occur. When the number of foams is reduced, the number of openings 4 is also reduced, and it is difficult to obtain sufficient polishing performance such as a polishing rate. Further, the thickness T correlates with the life of the polishing pad 1. That is, if the thickness T is too small, it wears out relatively early and the life is shortened. On the other hand, when the thickness T is too large, deformation due to pressing during polishing is increased, and on the contrary, the flatness of the object to be polished is impaired. In the present embodiment, the content HSC, the equivalence ratio R, the bulk density D, and the thickness T 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 the present embodiment, a non-defective urethane sheet 2 selected from those having an F value in the range of 100 to 200 obtained by the formula (1) is used. 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 polishing by the CMP method.

  Furthermore, in this embodiment, the prepolymer, the dispersion and the polyamine compound are mixed substantially uniformly in the mixing step to prepare a mixed solution. For this reason, the dispersion state of the water in a liquid mixture can be equalize | distributed by carrying out dispersion | distribution dilution of the water in a polyol compound previously. Thereby, the carbon dioxide generated by the reaction of water and the isocyanate group of the prepolymer is also dispersed substantially uniformly. Therefore, the foam 6 can be formed in the obtained polyurethane foam, the size of which is controlled and is evenly dispersed. By slicing and cutting in the slicing / cutting process, a plurality of sheets having substantially uniform apertures 4 formed substantially uniformly on the surface can be obtained, and a good urethane sheet 2 having the same F value is used. In the plurality of polishing pads 1, variations in polishing performance can be suppressed.

  Furthermore, in this embodiment, since the amount of water in the dispersion is set to a ratio of 0.01 to 6 g with respect to 1 kg of the weight of the prepolymer, the amount of water dispersed in the mixture is limited. , Extremely large foam formation and bias can be suppressed. Thereby, in the obtained several urethane sheet 2, all can make the average hole diameter of the opening 4 into the range of 20-60 micrometers. Therefore, the polishing scraps are accommodated in the apertures 4 while the slurry is held in the apertures 4 during the polishing process, so that the polishing efficiency can be improved. Moreover, it becomes easy to mix each component substantially uniformly by making the viscosity in the temperature of 50-80 degreeC of a prepolymer into the range of 2000-20000 mPa * s, and it can equalize the dispersion state of the water in a liquid mixture. it can. Thereby, the deviation of the foam 6 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, since the obtained plurality of urethane sheets 2 have improved thermal stability in a wet state, the hardness of the polishing pad 1 (urethane sheet 2) even if heat is generated due to friction during polishing using a slurry. The change is suppressed and the polishing performance can be stabilized.

  In the present embodiment, a specific compound is not specifically illustrated, 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.

  Moreover, 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 content ratio HSC is in the range of 32 to 42%, the equivalent ratio R is in the range of 0.7 to 0.9, the bulk density D is in the range of 0.45 to 0.55 g / cm ³ , and the thickness. Although the example which makes T the range of 0.5-2.0 mm was shown, this invention is not limited to these, The thing whose F value obtained by Formula (1) is the range of 100-200 is selected. You just have to do it. In other words, as long as the F value satisfies the preferred range, the content ratio HSC, the equivalence ratio R, the bulk density D, and the thickness T may be different from the above-described ranges. These ranges are preferable because the polishing pad 1 is used for polishing by the CMP method, but may be changed as appropriate depending on the characteristics of the object to be polished and the required polishing accuracy. Further, a plurality of sheets formed in the slicing / cutting process are grouped into one group, and all the sheets of the group having the difference between the maximum value and the minimum value of the F value, that is, the maximum value-minimum value of 50 or less are selected as non-defective products. It may be. By doing this, it is possible to sort non-defective products on a group basis, and it is possible to shorten the time required for sorting during manufacturing. Further, in the non-defective product group, the variation in F value is reduced, so that the polishing performance such as the polishing rate and the flatness of the object to be polished are suppressed among the plurality of polishing pads 1 obtained, and the polishing process is stabilized. Can be achieved. In order to further improve the stability of the polishing process and make the flatness of the object to be polished uniform, it is preferable to select a group in which the difference between the maximum F value and the minimum F value is 20 or less. When it is not determined as a non-defective product in group units, in other words, for a group in which the difference between the maximum value and the minimum value exceeds 50, a sheet having an F value in the range of 100 to 200 can be individually selected as a good product.

  Further, 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.

  Furthermore, in this embodiment, although not particularly mentioned, 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. You may do it. 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.

  Moreover, 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 and a slicing machine, 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, as the prepolymer of the first component, 279 parts of 2,4-TDI, 284 parts of PTMG having a number average molecular weight of about 1000 and 64 parts of diethylene glycol were reacted with a terminal isocyanate having an isocyanate content of 9.6%. This was heated to 55 ° C. using a group-containing urethane prepolymer 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. In Example 1, the content ratio 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. 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, and the bulk density D and the thickness T were measured on 23 sheets cut into a circular shape having a diameter of 800 mm. The F value was calculated for each sheet, and 20 sheets having an F value in the range of 100 to 200 were selected as non-defective products of the urethane sheet 2. That is, the three sheets were out of the range of F-values of 100 to 200, and were defective. The polishing pads 1 of Sample 1 to Sample 20 were obtained using each non-defective urethane sheet 2. The bulk density D, thickness T, and F value of each sample are shown in Table 1 below.

(Comparative Example 1)
In Comparative Example 1, a polyurethane foam produced in the same manner as in Example 1 was sliced to a thickness of 1.3 mm, and 23 circular sheets having a diameter of 800 mm were cut out. Also in Comparative Example 1, the content HSC is 39% and the equivalent ratio R is 0.7. Ten sheets were randomly extracted from each of the obtained sheets without performing selection based on the F value to obtain urethane sheets. The bulk density D and thickness T of each urethane sheet were measured, and the F value was calculated. The polishing pads of Sample 1 to Sample 10 were obtained using each urethane sheet. Table 2 shows the bulk density D, thickness T, and F value of each sample.

(Evaluation 1)
About each urethane sheet 2 of Example 1 and Comparative Example 1, abrasion loss was measured according to Japanese Industrial Standard (JIS K6902). That is, when the polishing surface of the polishing pad is brought into contact with a wear ring having abrasive grains having a particle size of 63 μm to 100 μm attached to the outer surface and a polishing wheel is attached to the outer periphery, the number of rotations on the polishing surface is 1000 times. The wear loss per hit was measured. The following wear tester was used for the measurement of wear loss. That is, the wear tester has a rotating disk on which a test sample is attached and which is pivotally supported so as to be rotationally driven. Above the turntable, a pair of cylindrical wear wheels are arranged with their end faces facing each other. The outer peripheral surface of the wear wheel is disposed so as to be in contact with the test sample attached to the rotating disk. The wear wheels are arranged on both sides in the radial direction of the rotating disk so as to be equidistant from the rotation axis of the rotating disk. Abrasive paper (for example, JIS R 6252 abrasive paper) having aluminum oxide abrasive grains having a particle size of 63 μm to 100 μm attached to the surface is affixed to the outer periphery of the wear wheel. The abrasive paper has a mass per unit area of 70 to 100 g / m ² , and is affixed so that no gaps are formed on the outer peripheral surface of the wear ring and do not overlap each other. When measuring the wear loss, a test sample (polishing pad) cut into the same shape as the turntable is attached to the turntable. The wear wheel with the abrasive paper is brought into contact with the upper surface of the test sample and pressed so that the load exerted on the contact surface is 5.20 ± 02N. By rotating the turntable, a pair of wear wheels whose outer peripheral surfaces are in contact with the test sample rotate in opposite directions. As a result, the surface of the test sample is worn and an annular wear mark is left. In this example, the weight change of the test sample before and after rotating the turntable 1000 times was defined as wear reduction. The measurement results of the weight loss are shown in Tables 1 and 2.

  As shown in Tables 1 and 2, the actual weight loss obtained by actual measurement is almost the same as the F value calculated by Equation (1). Accordingly, it has been clarified that the F value corresponds to the weight loss on the polished surface P.

(Evaluation 2)
Next, with respect to each of the urethane sheets 2 of Sample 6 to Sample 15 of Example 1 and each of the urethane sheets of Sample 1 to Sample 10 of Comparative Example 1, the average value of the F values calculated by Expression (1), measured by Evaluation 1 The average value of wear loss was obtained. Also, the variation in wear loss was calculated as CV (%) = 100 × standard deviation / average value. Table 3 below shows the average value of the obtained F values, the average value of weight loss and CV%.

  As shown in Table 3, in each sample of Comparative Example 1 that was not selected by the F value, the CV% was as high as 55.4%, and thus it was found that there was variation in wear loss. In comparison with Sample 6 to Sample 15 of Example 1 selected based on the F value, the CV% was 8.3%, which was low, and thus it became clear that the variation in wear loss was reduced. It was. In Samples 1 to 10 of Comparative Example 1, some F values exceed 200, and it is expected that the polishing performance of the resulting polishing pad and the flatness of the object to be polished will vary. On the other hand, the difference between the maximum value and the minimum value of the F value is 82 in the entire group of samples 1 to 20 of Example 1, whereas the maximum value of the F value is measured in the group of measured samples 6 to 15. Further, since the difference between the minimum values is 17 which is 20 or less, the variation in wear loss is small (see also Table 1). For this reason, if the groups such as Sample 6 to Sample 15 of Example 1 are selected as non-defective products, the polishing performance of the resulting polishing pad 1 is stabilized and the flatness of the object to be polished is improved. I can expect that. Therefore, since the F value obtained from the equation (1) and the wear loss on the polished surface P are in an approximate range, the wear loss of the polishing sheet can be determined by estimating the wear loss by the F value. It has been found that it is possible to make it appropriate to meet the requirements, and to reduce or minimize the variation in the product lot.

  Since the present invention provides a selection method for selecting a polishing sheet for a polishing pad that can optimize the degree of wear and stabilize the polishing performance in consideration of the lifetime, it contributes to the manufacture and sale of the polishing pad. Have industrial applicability.

It is sectional drawing which shows typically the polishing pad of embodiment provided with the polishing sheet which applied and selected this invention. 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 (polishing sheet)
4 Opening 6 Foaming

Claims (6)

From a plurality of sheets prepared by slicing and cutting a foam formed from a mixed liquid obtained by mixing an isocyanate group-containing compound obtained by reacting a polyisocyanate compound and a polyol compound, a polyamine compound, and water, A screening method for selecting a polishing sheet for a polishing pad having a polishing surface for polishing an object to be polished,
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 is R, and the content of hard segments formed by the reaction of the isocyanate group-containing compound and the polyamine compound is When HSC (%), the bulk density of the sheet is D (g / cm ³ ), and the thickness is T (mm), F = −36.7, HSC−758.8, R + 656, D−619, A sorting method, wherein a sheet having an F value in the range of 100 to 200 obtained by T + 2587 is sorted as a non-defective product of the polishing sheet.   The plurality of sheets produced by slicing and cutting are grouped into one group, and a group in which the difference between the maximum value and the minimum value of the F values is 50 or less is selected as a non-defective product. The sorting method described in 1.   The sheet is prepared by adjusting the amounts of the polyisocyanate compound, the polyol compound, and the polyamine compound so that the equivalent ratio R is in a range of 0.7 to 0.9. Item 2. The screening method according to Item 1.   The said sheet | seat is prepared by adjusting the quantity which the said isocyanate group containing compound and a polyamine compound mix so that the said content rate HSC may be in the range of 32%-42%. The sorting method described in 1.   The screening method according to claim 4, wherein the polyisocyanate compound contains at least 50% by weight of tolylene diisocyanate.   6. The screening method according to claim 5, wherein the polyol compound contains at least 50% by weight of polytetramethylene ether glycol.

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