JP5166188B2 - Polishing sheet and polishing pad used for polishing pad for polishing processing - Google Patents

Description

  The present invention relates to a polishing sheet and a polishing pad used for a polishing pad for polishing, and in particular, an isocyanate group-containing compound produced by the reaction of a polyisocyanate compound and a polyol compound, a polyamine compound, water, and a non-reactive material. The present invention relates to a polishing sheet made of a polyurethane resin having a foam structure formed by mixing gas and having a polishing surface for polishing an object to be polished, and a polishing pad provided with the polishing sheet.

  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 includes a polishing sheet having a polishing surface for polishing the processed surface of an object to be polished. Yes. The polishing sheet has a foam structure, and an opening is formed in the polishing surface by grinding processing 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. 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.

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 is performed with water in the formation of the foam structure, the discharge when pouring the raw material liquid for forming the polishing pad into the mold is performed. Since the large apertures are formed by slowing down the speed, there is a problem that the dispersion state of the large apertures is likely to vary. Also, 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. There is a problem that variations tend to occur. Furthermore, aggregates due to abrasive particles and polishing scraps are likely to be generated due to the large openings, and the generation 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, in order to give dressing properties to the polishing pad, a prepolymer using a specific polyol component and a general prepolymer are mixed as a raw material liquid for forming the polishing pad, and a chain extender 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. For this reason, 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 3 has a problem in that although the change in the polishing rate or 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 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.

  In view of the above circumstances, the present invention provides a polishing sheet that is used for a polishing pad for polishing and that can optimize the degree of wear and stabilize the polishing performance, and a polishing pad including the polishing sheet. Let it be an issue.

In order to solve the above-mentioned problems, a first aspect of the present invention is a polishing sheet used for a polishing pad for polishing, comprising an isocyanate group-containing compound produced by a reaction of a polyisocyanate compound and a polyol compound, and a polyamine In a polishing sheet made of a polyurethane resin having a foamed structure formed by mixing a compound, water, and a non-reactive gas and having a polishing surface, the hydroxyl group of the polyol compound and the polyamine with respect to the isocyanate group of the polyisocyanate compound The total equivalent ratio of amino groups of the compound is in the range of 0.7 to 0.9, the hard segment content formed by the reaction of the isocyanate group-containing compound and the polyamine compound is in the range of 32% to 42%, range density of ^{0.45g / cm 3 ~0.55g / cm 3} , a Shore a The mixing amount of the polyisocyanate compound, polyol compound, polyamine compound, water and non-reactive gas is adjusted so that the degree is 85 degrees or more, and the abrasive grains having a particle diameter of 63 μm to 100 μm are formed on the surface. When the polishing surface is brought into contact with a wear ring having a polishing paper adhered to the outer periphery and rotated, the wear loss per 1000 rotations on the polishing surface is in the range of 100 mg to 200 mg. It is characterized by having.

  In the first aspect, the bulk density correlating with the foam structure, the equivalent ratio correlating with hardness and brittleness, the hard segment content, and the Shore A hardness are limited to the respective ranges. Since the abrasion loss on the polished surface for polishing the workpiece is in the range of 100 to 200 mg, the degree of wear should be optimized even if the bulk density and hardness are changed according to the workpiece. Since the polished surface is regenerated timely due to abrasion during polishing, the polishing performance can be stabilized.

  In the first embodiment, 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. Further, when the equivalent ratio is R, the hard segment content is HSC, the bulk density is D, and the Shore A hardness is A, F = −13.8 · HSC−726 · R + 773 · D−7. The F value obtained with 95 · A + 1516 can be in the range of 100 to 200. Small pores with an average pore diameter in the range of 30 μm to 200 μm and large apertures with a pore diameter in the range of 300 μm to 3000 μm can be formed substantially uniformly on the polished surface. Moreover, the groove | channel processing or embossing may be given to the grinding | polishing surface side. At least a part may have a light transmitting portion that allows light transmission for optically detecting the polishing state during polishing. At this time, it is preferable that the light transmission part is formed over the entire thickness direction.

  According to a second aspect of the present invention, there is provided a polishing pad comprising the polishing sheet according to the first aspect. In this aspect, by providing the polishing sheet of the first aspect, it is possible to optimize the degree of wear of the polishing sheet and stabilize the polishing performance.

  According to the present invention, the bulk density correlating with the foam structure, the equivalent ratio correlating with hardness and brittleness, the hard segment content, and the Shore A hardness are limited to the respective ranges. Since the abrasion loss on the polished surface for polishing the workpiece is in the range of 100 to 200 mg, the degree of wear should be optimized even if the bulk density and hardness are changed according to the workpiece. Since the polished surface is regenerated timely due to wear during polishing, the effect of stabilizing the polishing performance can be obtained.

  Hereinafter, an embodiment of a polishing pad for primary polishing of a silicon wafer, which includes a polishing sheet to which the present invention is applied, 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 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, a polyisocyanate compound, a dispersion, and It is formed by slicing a polyurethane foam obtained by casting and curing a mixed liquid obtained by mixing a gas that is 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. The foam 3 formed with water in the dispersion has an average pore size in the range of 30 to 200 μm, and the foam 5 formed of non-reactive gas has a pore size in the range of 300 to 3000 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 the foam 3 and the foam 5, the average hole diameter is 30 to 200 μm in the opening 4 and the hole diameter is 300 to 3000 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 the urethane sheet 2, the total equivalent ratio R 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 in the range of 0.7 to 0.9, and is generated by the reaction of the polyisocyanate compound and the polyol compound. The hard segment content HSC (%) formed by the reaction of the isocyanate group-containing compound and the polyamine compound is in the range of 32 to 42%, and the bulk density D (g / cm ³ ) is 0.45 to 0.55 g / It is adjusted and formed such that the hardness A (degree) of the range of cm ³ and Shore A hardness is 85 degrees or more. The equivalence ratio R, the content ratio HSC, the bulk density D, and the hardness A can be adjusted by the mixing amount of a polyisocyanate compound, a polyol compound, a polyamine compound, water, and a non-reactive gas.

  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 hard segment 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.

  The hard segment content HSC is expressed by the following formula (hereinafter referred to as formula (1)), that is, HSC = 100 · (r−1) · (Mdi + Mda) / (Mg + r · Mdi + (r−1) · Mda). Can be expressed as In the formula (1), 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 (1) 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 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.

  The bulk density D correlates with the foam structure of the urethane sheet 2. That is, when the pore diameters of the foam 3 and foam 5 are 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. 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 degree of polymerization 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, so it is preferable to set the Shore D hardness to 75 degrees or less. 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 non-reactive gas. It can be adjusted by changing.

  Since the polishing pad 1 is used for primary polishing of a silicon wafer, the urethane sheet 2 in which the equivalent ratio R, the content ratio HSC, the bulk density D, and the hardness A are adjusted to the above-described ranges is used in Japan Industrial Standard (JIS K 6902). In accordance with a method according to the Taber abrasion test of (Abrasion resistance A method), the polishing surface P is brought into contact with a wear ring having abrasive paper with a grain size of 63 to 100 μm attached to the outer surface and affixed to the outer periphery. When it is rotated, the wear loss per 1000 rotations on the polishing surface P is in the range of 100 to 200 mg. In such a urethane sheet 2, F = −13.8 · HSC-726 · R + 773 · D-7.95 · A + 115 (hereinafter referred to as formula (2) depending on the equivalent ratio R, content HSC, bulk density D and hardness A. The F value obtained in () is in the range of 100 to 200.

  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 (2) can be obtained. Therefore, the F value obtained by the equation (2) represents the ease of wear of the urethane sheet 2. This F value is determined by the rotation on the polishing surface P when the polishing surface P is brought into contact with a wear ring in which abrasive paper having a particle size of 63 to 100 μm attached to the surface is affixed to the outer periphery. This corresponds to a weight loss (mg) per several thousand times. In the urethane sheet 2, the amount of water and the amount of non-reactive gas mixed in the polyisocyanate compound, polyol compound, polyamine compound, mixed liquid described above are adjusted so that the F value is in the range of 100 to 200. Yes. By setting the F value within this range, the degree of wear of the urethane sheet 2 is optimized, and the polishing pad 1 can be suitably used for polishing 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 A, for example, by reducing the equivalent ratio R, the foam structure and the hardness A can be changed without greatly changing The value can be increased. 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 (2), 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 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 Mixing step for preparing a mixed liquid by mixing the isocyanate group-containing compound thus obtained, the dispersion liquid, the polyamine compound, and a gas that is non-reactive with the polyisocyanate compound, the dispersion liquid and the polyamine compound. A casting process in which the polyurethane foam is cast, a curing molding process in which the polyurethane foam is formed by foaming and curing in the mold, and a slice in which the polyurethane foam is sliced to form a plurality of urethane sheets 2 Process, urethane sheet 2 and double-sided tape bonded together It is produced through a laminating step of forming a head 1. 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 A 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 performance. 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. By making the viscosity of the isocyanate group-containing compound and the polyamine compound approximately equal to the viscosity of the solution, it becomes easy to uniformize the dispersion of water and non-reactive gas in the mixing step. Therefore, a polyol compound having a number average molecular weight of 500 to 3000 should be used. preferable. 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 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 1 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, 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 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 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 and polyol compound used for the production of the prepolymer and the polyamine compound. 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 (1). 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 within the above-described ranges, the F value is obtained by the above-described formula (2).

  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 diameters are all in the range of 30 to 200 μm, and the hole diameters of the openings 6 are in the range of 300 to 3000 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 300 μm, the effect of improving the slurry holding ability cannot be obtained sufficiently. Conversely, if the hole diameter exceeds 3000 μm, aggregation of slurry and polishing scraps is caused, 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 focusing on the operation of the urethane sheet 2.

  In the conventional polishing process, a polishing pad provided with a polishing sheet having a foamed 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 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. This embodiment is a polishing pad provided with a polishing sheet that can solve these problems.

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, in the polishing sheet formed of the polyurethane resin, the total equivalent ratio R 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 formed by the reaction of the prepolymer (isocyanate group-containing compound) and the polyamine compound. From the hard segment content HSC (%), bulk density D (g / cm ³ ), and hardness A, Formula (2), that is, F = −13.8 · HSC−726 · R + 773 · D−7. The F value obtained by 95 · A + 1516 shows excellent correlation with the ease of wear of the abrasive sheet.

  In the urethane sheet 2 of this embodiment, F value obtained by Formula (2) 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 affects the hardness A, for example, by reducing the equivalent ratio R, the foam structure and the hardness A are greatly changed. The F value can be increased without any problem. In other words, even if the content ratio 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, the equivalence ratio R, the bulk density D, and the hardness A so as to satisfy the appropriate range of the F value obtained by the above formula (2), it is possible to compensate for the disadvantages caused by the respective factors. it can. 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 hard segment 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. When 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, resulting in insufficient durability. 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, so that 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, and clogging is likely to occur. 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. On the other hand, the hardness A is a value that varies depending on the equivalent ratio R, the content ratio HSC, and the bulk density D, but also varies depending on the average degree of polymerization and molecular weight distribution of the urethane resin constituting the urethane sheet 2 and the shape and distribution of the pores. Therefore, fluctuations due to these are also considered. That is, if the hardness A 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 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 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 (2). For this reason, the fault which arises by each factor can be compensated.

  Furthermore, in this embodiment, the F value obtained by Formula (2) 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 300 to 3000 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, since the plurality of urethane sheets 2 obtained 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.

  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, although the example which makes F value obtained by Formula (2) into the range of 100-200 was shown, this invention is not limited to this, The granule of a particle size of 63-100 micrometers When the polishing surface P is brought into contact with a wear ring having a polishing paper adhered to the outer surface and rotated, the wear loss per 1000 revolutions on the polishing surface P is in the range of 100 to 200 mg. I just need it. Since the F value obtained by the formula (2) shows excellent correlation with the ease of wear of the urethane sheet 2, the F value is in the range of about 100 to 200 when the wear loss is in the range of 100 to 200 mg. Since the polishing pad 1 is used for primary polishing of a silicon wafer, the equivalent ratio R is in the range of 0.7 to 0.9, the content HSC is in the range of 32 to 42%, and the bulk density D is 0.45 to 0.4. By adjusting the range of 55 g / cm ³ and the hardness A to be 85 degrees or more, the weight loss of the urethane sheet 2 can be adjusted to an appropriate range.

  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 an end with an isocyanate content of 9.6% obtained by reacting 64 parts of diethylene glycol This was heated to 55 ° C. using an isocyanate group-containing urethane prepolymer and defoamed 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 hard segment content 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.

(Comparative Example 2)
In Comparative Example 2, 181 parts of 2,4-TDI as the prepolymer of the first component, 192 parts of PTMG having a number average molecular weight of about 1000, and 43 parts of diethylene glycol were reacted with a terminal isocyanate having an isocyanate content of 9.1%. A urethane sheet was prepared and a polishing pad was obtained in the same manner as in Example 1 except that the group-containing urethane prepolymer was used. As shown in Table 1, in Comparative Example 2, the content rate HSC is 37% and the equivalent ratio R is 0.6.

(Evaluation 1)
About the Example and the comparative example, the bulk density D of the urethane sheet, the average hole diameter of the opening 4, and the hole distribution of the opening 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 average pore diameter of the apertures 4 was observed by magnifying a range of about 1.3 mm by 175 times with a microscope (manufactured by KEYENCE, VH-6300), and the obtained image was image processing software (Image Analyzer V20LAB Ver. 1.3) processed and calculated. The opening 6 was observed with a microscope (manufactured by KEYENCE, VH-6300) at 10 points in a 3.0 cm square area 10 times larger, and the variation CV% of the number of openings of 500 μm or more was CV = 100. X Standard deviation / average value. For the urethane sheet, the Shore A hardness was measured as the hardness A in accordance with Japanese Industrial Standard (JIS K 7311). Table 2 shows the bulk density D, the average pore diameter of the apertures 4, the CV% of the apertures 6, the results of the hardness A, and the F value obtained by the formula (2).

As shown in Table 2, in Comparative Example 1 and Comparative Example 2, the CV% of the opening 6 was 6.2% and 8.5%, respectively, and the distribution of the opening 6 may vary. understood. For this reason, the bulk density D was as small as 0.47 g / cm ³ . On the other hand, in Example 1 and Example 2, the CV% of the opening 6 is reduced to 3.5% and 3.7%, respectively, and the bulk density D is 0.49 g / cm ³ and 0.52 g, respectively. / Cm ³ and increased. Compared with Example 1 and Example 2, in Comparative Example 1, since the content ratio HSC was reduced and the equivalent ratio R was increased, the F value showed a small value of 74, and in Comparative Example 2, the content ratio HSC Since the equivalence ratio R was reduced, the F value was as large as 232.

(Evaluation 2)
Next, with respect to the polishing pads of each Example and Comparative Example, the wear 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 wear loss are shown in Table 3 below.

  As shown in Table 3, in Comparative Example 1, the wear loss was as small as 74 mg, and it was confirmed that most of the openings 4 were clogged by the evaluated polishing pad. Further, in Comparative Example 2, the weight loss of wear is as large as 238 mg, and it is expected that defects such as variations in polishing performance and scratches due to polishing scraps are likely to occur. On the other hand, in Example 1 and Example 2, the weight loss by wear shows moderate values of 151 mg and 152 mg, respectively, and the clogging of the opening 4 may be less than that in Comparative Example 1 even in the polishing pad after evaluation. confirmed. Further, it is clear that the wear loss of each of the examples and comparative examples is in a range that approximates the F value of the equation (2) (see also Table 2).

(Evaluation 3)
Moreover, using the polishing pads of the examples and comparative examples, bare silicon for silicon wafers was polished under the following polishing conditions, and the polishing rate was measured. The polishing rate represents the amount of polishing per minute in terms of thickness, and was calculated from the amount of polishing determined from the weight reduction of bare silicon before and after polishing, the polishing area and specific gravity of bare silicon. 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: Bare silicon for silicon wafer (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. In Comparative Example 2, although the polishing rate was improved as compared with Comparative Example 1, it was confirmed that scratches considered to be caused by abrasion debris of the polishing pad were generated. 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, by adjusting the equivalent ratio R, the content rate HSC, the bulk density D, and the hardness A to the ranges described above, the F value obtained by the formula (2) is Since the wear loss is optimized within the above-described range, the variation in the distribution of the apertures 6 is reduced, the apertures 4 are less likely to be clogged, exhibit a good polishing rate, and the occurrence of scratches can be suppressed. Became clear.

  The present invention is used for a polishing pad for polishing processing, and provides a polishing sheet capable of optimizing the degree of wear and stabilizing polishing performance, and a polishing pad provided with the polishing sheet. Since it contributes to sales, it has industrial applicability.

It is sectional drawing which shows typically the polishing pad of embodiment provided with the urethane sheet 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 (polishing sheet)
3, 5 Foam 4, 6 Opening

Claims (9)

A polishing sheet used for a polishing pad for polishing processing, which is formed by mixing an isocyanate group-containing compound, a polyamine compound, water, and a non-reactive gas generated by the reaction of a polyisocyanate compound and a polyol compound. In the polishing sheet made of polyurethane resin having a foamed structure and having a polishing surface, the equivalent ratio of the total 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 0.7 to 0.9. The hard segment formed by the reaction of the isocyanate group-containing compound and the polyamine compound is in the range of 32% to 42%, and the bulk density is in the range of 0.45 g / cm ^{3 to} 0.55 g / cm ³ . The polyisocyanate has a Shore A hardness of 85 degrees or more. A compound paper, a polyol compound, a polyamine compound, water and a non-reactive gas are mixed and formed. Abrasive paper with abrasive grains of 63 to 100 μm attached to the surface is attached to the outer periphery. A polishing sheet characterized in that when the polishing surface is brought into contact with a worn wheel and rotated, the wear loss per 1000 rotations on the polishing surface is in the range of 100 mg to 200 mg.   The abrasive sheet according to claim 1, wherein the polyisocyanate compound contains at least 50% by weight of tolylene diisocyanate.   The polishing sheet according to claim 2, wherein the polyol compound contains at least 50% by weight of polytetramethylene ether glycol.   When the equivalent ratio is R, the hard segment content is HSC, the bulk density is D, and the Shore A hardness is A, F = −13.8 · HSC−726 · R + 773 · D− 4. The abrasive sheet according to claim 3, wherein the F value obtained by 7.95 · A + 1516 is in the range of 100 to 200.   2. The polishing surface according to claim 1, wherein small pores having an average pore diameter of 30 μm to 200 μm and large apertures having a pore diameter of 300 μm to 3000 μm are formed substantially evenly on the polished surface. Polishing sheet.   The polishing sheet according to claim 5, wherein the polishing surface is grooved or embossed.   The polishing sheet according to claim 1, further comprising a light transmitting portion that allows light transmission for optically detecting a polishing processing state during polishing processing.   The polishing sheet according to claim 7, wherein the light transmission part is formed over the entire thickness direction.   A polishing pad comprising the polishing sheet according to claim 1.

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