JP5107683B2 - Polishing pad and method of manufacturing polishing pad - Google Patents

Description

  The present invention relates to a polishing pad and a method for manufacturing the polishing pad, and more particularly to a polishing pad mainly composed of an isocyanate group-containing compound and a method for manufacturing the polishing pad.

  In materials (objects to be polished) such as semiconductor wafers and glass substrates for liquid crystal displays, surface flatness is required, and therefore polishing using a polishing pad is performed. In semiconductor wafers, 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 surface has become important. On the other hand, with a glass substrate for a liquid crystal display, higher flatness of the surface is required as the liquid crystal display becomes larger.

  As a method for planarizing the surface of a semiconductor wafer or a glass substrate, a chemical mechanical planarization (hereinafter abbreviated as CMP) method is generally used. In the CMP method, a polishing liquid (slurry) in which abrasive particles are dispersed in an alkaline solution is supplied in a state where the surface (processing surface) of an object to be polished is pressed against a polishing pad, and the processing surface is polished. Polishing is performed by mechanical action by abrasive particles in the slurry and chemical action by an alkaline solution. With the advancement of flatness required for the processed surface, the polishing accuracy required for the CMP method, in other words, the performance required for the polishing pad is also increasing.

  In the CMP method, rigid foam polyurethane is widely used as a polishing pad. In the production of such a polishing pad, usually, a prepolymer containing an isocyanate group-containing compound and a chain extender containing an active hydrogen compound are cured by reaction to form a foam. The obtained foam is sliced into a sheet to form a polishing pad. Since foam is formed inside the foam, an opening that can hold the slurry during polishing is formed on the surface of the polishing pad formed by slicing.

Various techniques have been disclosed for forming foam inside when molding a foam of rigid polyurethane foam. For example, there is a technique of internally adding hollow fine particles during molding (see Patent Document 1, Patent Document 2, and Patent Document 3). Further, as a technique for forming foam by adding water at the time of molding, there is a technique of a polishing pad in which a composition of an isocyanate group-containing compound or an active hydrogen compound is determined to form a foam having a diameter of 50 to 150 μm (see Patent Document 4). It is disclosed. Furthermore, as a technique for forming foam by enclosing an inert gas at the time of molding, a silicon-based activator is added so that the number of independent foams is 200 to 600 / mm ² and the average foam diameter is 30 to 60 μm. A pad technology (see Patent Document 5) is disclosed.

Japanese Patent No. 3013105 Japanese Patent Laid-Open No. 11-322877 Japanese Patent Laid-Open No. 11-322878 JP 2005-68168 A Japanese Patent No. 3455208

  However, in the techniques of Patent Documents 1 to 3, since the components of the hollow fine particles are present as contaminants between the processed surface and the polishing pad at the time of polishing, an unexpected adverse effect due to the slurry used. May be invited. In this respect, the techniques of Patent Document 4 and Patent Document 5 do not use hollow fine particles, and therefore can prevent the influence of impurities. However, in the technique of Patent Document 4, foaming is formed by the addition of water, but it is difficult to equalize the dispersion state of water. Therefore, in the molded foam, the foaming is biased and the average pore diameter is also different. There is a problem that it is likely to occur. For this reason, the polishing performance varies among a plurality of polishing pads obtained from one foam. Further, in the technology of Patent Document 5, if the average pore diameter is foam of about several μm, it is easier to control than the formation of foam by water, but it is difficult to form and equalize a slightly large foam having an average pore diameter of several tens of μm. There is a problem. Since enormous foaming may be formed by enclosing an inert gas, it is difficult to make the hole diameter uniform, and scratches are generated on the object to be polished during polishing, resulting in a decrease in flatness. It becomes.

  An object of the present invention is to provide a polishing pad capable of improving the flatness of an object to be polished by forming the holes substantially uniformly and substantially uniformly, and a method for manufacturing the polishing pad.

In order to solve the above problems, a first aspect of the present invention, an isocyanate group-containing compound, a chain extender and water to 200g ^/ m ³ ~3000g / m 3 including water vapor or the isocyanate group-containing compound and the chain It is characterized by being obtained by slicing a foam formed from a mixed solution obtained by mixing a gas that is non-reactive with an extender and a gas mixture of the water vapor.

  In the first aspect, since fine bubbles are generated in the mixed liquid by the water vapor or the mixed gas mixed in the mixed liquid, the water contained in the water vapor or the mixed gas is dispersed almost uniformly in the mixed liquid. By reacting with the group-containing compound, foams having a substantially uniform size are formed in the foam in a substantially uniform manner. For this reason, substantially uniform openings are formed substantially evenly on the surface of the polishing pad obtained by slicing. Therefore, the polishing liquid can be supplied substantially uniformly between the object to be polished and the polishing pad while holding the polishing liquid during the polishing process, and the flatness of the object to be polished can be improved.

  In the first embodiment, if the viscosity of the isocyanate group-containing compound at a temperature of 50 ° C. to 80 ° C. is in the range of 500 mPa · s to 4000 mPa · s, the movement of foaming is suppressed in the mixed solution, so Can be suppressed. Openings are formed on the surface by the slice of the foam, and if the average opening diameter of the openings is in the range of 10 μm to 100 μm, the retention of the polishing liquid can be improved during polishing. If the ratio of the hardness when immersed in water at a temperature of 70 ° C. for the same fixed time with respect to the hardness when immersed in water at a temperature of 20 ° C. for a fixed time is 80% or more, friction or the like may occur during polishing using a polishing liquid. Even when heat is generated, the hardness in a wet state is unlikely to change, so that a reduction in polishing performance can be suppressed. When multiple polishing pads are formed with foam slices, the difference in the average hole diameter and the density of the holes formed on each surface are within ± 3% of the average value. If it is inside, the average pore diameter is the same for the plurality of polishing pads, and the proportion of the space occupied by the foam is the same, so that variation in polishing performance can be suppressed.

The second aspect of the present invention, the isocyanate group-containing compound and, while mixing the chain extender, water and 200g ^/ m ³ ~3000g / m 3 including water vapor or the isocyanate group-containing compound and the chain extender A foam is formed in the foam forming step by preparing a mixed liquid while blowing a mixed gas of the non-reactive gas and the water vapor, and forming a foam from the mixed liquid, and the foam formed in the foam forming step And a slicing step for forming a polishing pad.

  In the second aspect, after preparing the liquid mixture in the foam formation step, the foam may be continuously formed. If the amount of water vapor or mixed gas blown in the foam formation step is 0.5 to 3.4 liters per 1 kg of the total weight of the isocyanate group-containing compound and the chain extender, the water vapor or Since the amount of the mixed gas is limited, the formation of extremely large foam can be suppressed. Moreover, it is preferable to prepare a liquid mixture on the conditions of a shear rate of 9,000-41,000 / sec and the frequency | count of shear of 300-10,000 times in a foam formation step.

  According to the present invention, since fine bubbles are generated in the mixed liquid by the water vapor or the mixed gas mixed in the mixed liquid, the water contained in the water vapor or the mixed gas is dispersed substantially uniformly in the mixed liquid. By reacting with the group-containing compound, foam of a substantially uniform size is formed in the foam to be substantially uniformly dispersed, so that a substantially uniform opening is substantially formed on the surface of the polishing pad obtained by slicing. Since it is formed evenly, the polishing liquid can be supplied substantially uniformly between the object to be polished and the polishing pad while holding the polishing liquid during the polishing process, and the flatness of the object to be polished can be improved. be able to.

  Hereinafter, embodiments of a polishing pad 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 is a rigid foam type polyurethane sheet, and contains an isocyanate group-containing compound as a main component. The polishing pad 1 has a polishing surface P that abuts a processed surface of an object to be polished via a slurry during polishing. The polishing pad 1 includes an isocyanate group-containing compound, a chain extender, a water vapor containing 200 to 3000 g / m ^{3 of} water, a gas that is non-reactive with the isocyanate group-containing compound and the chain extender (hereinafter, non-reactive gas). ) And a mixed gas (hereinafter abbreviated as a water vapor mixed gas), and a foam obtained by casting and curing a mixed liquid in a mold. That is, the polishing pad 1 is formed by dry molding.

  Inside the polishing pad 1, foam 3 having a substantially circular cross section is formed in a substantially uniform manner by reaction of water in the water vapor mixed gas mixed at the time of dry molding and the isocyanate group-containing compound. Since the polishing pad 1 is formed by slicing a foam, a part of the foam 3 is opened on the polishing surface P, and an opening 4 is formed. The opening 4 formed in the polishing surface P has an average opening diameter adjusted to a range of 10 to 100 μm. The thickness of the polishing pad 1 is set in the range of 1.3 to 2.5 mm. This polishing pad 1 has a wet hardness retention rate of 80 defined by the ratio of the hardness when immersed in water (hot water) at a temperature of 70 ° C. for the same fixed time with respect to the hardness when immersed in water at a temperature of 20 ° C. for a certain time. % Or more is set.

  Further, 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. The double-sided tape has an adhesive layer formed on both surfaces of a base material 7 such as a polyethylene terephthalate (hereinafter abbreviated as PET) film. As an adhesive of an adhesive layer, an acrylic adhesive etc. can be mentioned, for example. The double-sided tape is bonded to the polishing pad 1 with a pressure-sensitive adhesive layer on one side, and the surface of the pressure-sensitive adhesive layer on the other side (the lowermost side in FIG. 1) is covered with a release paper (not shown).

(Manufacture of polishing pad)
The polishing pad 1 is manufactured through each process shown in FIG. That is, a preparation step for preparing an isocyanate group-containing compound, a chain extender, and a water vapor mixed gas, and a mixing step for preparing a mixed solution by mixing the isocyanate group containing compound, the chain extender, and the water vapor mixed gas (foam) A part of the forming step), a casting process in which the mixed liquid is poured into the mold (a part of the foam forming step), and a curing molding process in which the foam is formed by foaming and curing in the mold (foam forming) Part of the step), a slicing process (slicing step) in which the foam is sliced into a sheet to form the polishing pad 1, and a laminating process in which the polishing pad 1 and the double-sided tape are bonded together. Hereinafter, it demonstrates in order of a process.

(Preparation process)
In the preparation step, an isocyanate group-containing compound, a chain extender, and a water vapor mixed gas are prepared.

  As an isocyanate group-containing compound, an isocyanate-terminated urethane prepolymer (hereinafter simply referred to as “isocyanate-terminated urethane prepolymer”) produced by reacting a polyol compound having two or more hydroxyl groups in the molecule with a diisocyanate compound having two isocyanate groups in the molecule. Abbreviated as prepolymer). When the polyol compound and the diisocyanate compound are reacted, 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 to be used has a too high viscosity, the fluidity becomes poor and it becomes difficult to mix substantially uniformly in the subsequent mixing step. When the temperature is raised and the viscosity is lowered, the pot life is shortened. On the contrary, mixing spots are generated, and the size of the foam 3 formed in the foam varies. On the other hand, when the viscosity is too low, bubbles generated by the water vapor mixed gas move in the mixed solution, and it becomes difficult to form the foam 3 dispersed substantially uniformly in the foam. For this reason, it is preferable that a prepolymer sets the viscosity in the temperature of 50-80 degreeC in the range of 500-4000 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.

  Examples of the diisocyanate compound used for producing the prepolymer include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, and diphenylmethane-4. , 4′-diisocyanate, 3,3′-dimethoxy-4,4′-biphenyl diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, xylylene-1,4-diisocyanate, 4,4′-diphenyl Propane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate DOO, 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.

  On the other hand, the polyol compound used for the production of the prepolymer may be a diol compound, a triol compound, or the like, for example, a low molecular weight polyol compound such as ethylene glycol or butylene glycol, and a polyether polyol such as polytetramethylene glycol. 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.

  The chain extender may be a compound having two or more active hydrogen groups that react with the isocyanate group of the prepolymer in order to constitute a hard segment (urethane bond portion imparting rigidity with a high melting point). For example, as a polyamine compound, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane (hereinafter abbreviated as MOCA). And polyamine compounds having the same structure as MOCA. The polyol compound may be a diol compound, a triol compound, etc., for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, Low molecular weight polyol compounds such as 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and polytetramethylene glycol (hereinafter abbreviated as PTMG). ), Polyethylene glycol, polypropylene glycol (hereinafter abbreviated as PPG), and any other high molecular weight polyol compound can be used. Further, amine-based compounds having a hydroxyl group, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2 -Hydroxypropylethylenediamine or the like may be used.

  In the case where the chain extender is solid at room temperature such as MOCA and a polyamine compound having the same structure as MOCA, since the viscosity of the chain extender is equal to that of the prepolymer, it becomes easy to mix uniformly in the mixing step. And heated and fed in a melted state to an appropriate viscosity. Further, when the chain extender is a polyol compound, it is preferable in terms of viscosity to use a polyol compound having a number average molecular weight of 500 to 3000, and in particular, a polishing pad in which PTMG or PPG having a number average molecular weight of 800 to 3000 is dispersible or obtained. More preferable in terms of heat resistance. In this example, MOCA as a polyamine compound and PPG having a number average molecular weight of about 2000 as a polyol compound are used separately as a chain extender and used separately, but in combination with a polyol compound that can dissolve the polyamine compound If present, by mixing, dissolving, and using the polyamine compound and the polyol compound in advance, the viscosity close to that of the prepolymer can be achieved at a temperature lower than the temperature at which the polyamine compound is heated and melted. In the preparation of such a chain extender, a general stirring device may be used for stirring and mixing, and the polyamine compound and the polyol compound may be mixed substantially uniformly.

The water vapor mixed gas prepared in the preparation step is adjusted so as to contain 200 to 3000 g / m ^{3 of} water. If the amount of water contained in the steam mixed gas is too small, the foam 3 and consequently the opening 4 become too small and clogging is caused by a polishing liquid or the like during polishing, which is not preferable. On the other hand, if the amount of water is too large, an extremely large foam is formed by the reaction between water and the isocyanate group of the prepolymer. For this reason, it is preferable to adjust the amount of water in the above-described range, and it is possible to adjust the amount to be in the range of 500 to 1500 g / m ^{3 in} view of ensuring the polishing liquid retention and preventing clogging. More preferred. Moreover, water turns into water vapor | steam by heating (heating) and supplying water vapor | steam mixed gas by a mixing process, and humidity will be 50-100%. Examples of the non-reactive gas mixed with water vapor include air, nitrogen, oxygen, carbon dioxide, helium, and argon.

(Mixing process, casting process, curing molding process)
As shown in FIG. 2, in a mixing process, the liquid mixture which mixed the prepolymer prepared in the preparatory process, the chain extender, and water vapor | steam mixed gas is prepared. In the casting process, the liquid mixture prepared in the mixing process is cast into a mold, and in the curing molding process, the 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.

  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. To form a foam. 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, there are a supply tank that contains a prepolymer as the first component, a second component, and a chain extender as the third component, respectively, and a supply device 16 that supplies the steam mixed gas into the mixing tank 12. Has been placed. The supply port from each supply tank is connected to the upstream end of the mixing tank 12, and the supply port from the supply device 16 is located about 1/3 from the upstream end with respect to the entire length of the mixing tank 12. It is connected to the. The stirring blade 14 is fixed to a rotating shaft arranged from the upstream side to the downstream side at a substantially central portion in the mixing tank 12. As the rotating shaft rotates, the stirring blade 14 rotates and mixes the first component, the second component, and the steam mixed gas so as to shear. The obtained liquid mixture is poured into the mold 25 from a discharge port formed at the downstream end of the mixing tank 12. The upper part of the mold 25 is open, and in this example, the size is set to 1050 mm (length) × 1050 mm (width) × 50 mm (thickness).

  Since most of the first component prepolymer, second component, and third component chain extender are solid or difficult to flow at room temperature, each supply tank is heated so that each component can flow. ing. Moreover, in order to supply water in the mixing tank 12 as a water vapor mixed gas, the supply device 16 is heated (heated) to a temperature of 80 to 160 ° C. The supplied steam mixed gas becomes fine bubbles by the rotation of the stirring blade 14 in the mixing tank 12, and these bubbles are dispersed almost uniformly in the mixed liquid. If the supply amount of the water vapor mixed gas is too small, the dispersion state of the bubbles tends to be biased. On the other hand, if the supply amount is too large, extremely large bubbles are generated. For this reason, it is preferable to adjust the supply amount of the steam mixed gas so as to be a ratio of 0.5 to 3.4 L with respect to 1 kg of the total weight of the prepolymer and the chain extender. The mixing tank 12 is not particularly heated and is exposed to a normal temperature environment.

  The first component, the second component, and the third component are supplied to the mixing tank 12 and the water vapor mixed gas is supplied at a stage where the components are mixed to some extent by the stirring blade 14. By adjusting the mixing conditions in the mixer 20, that is, the shearing speed and the number of shearing of the stirring blade 14, the respective components and the water vapor mixed gas are mixed substantially uniformly to prepare a mixed liquid. If the shear rate of the stirring blade 14 is too low, the size of the foam 3 formed in the 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 foam is obtained. Variation in the dispersed state of the foam 3 formed on the body is 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 is 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 cast the mixed solution into the mold 25 of about 100 kg in the casting process 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 casting the mixed solution into the mold 25 in the casting step, the mixed solution 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 liquid mixture is cast into the mold 25 substantially evenly.

  In the curing molding step, the cast mixture is reacted in the mold 25 to form a foam. At this time, the prepolymer is crosslinked and cured by the reaction between the prepolymer and the chain extender. Since the upper part of the mold 25 is open, the cross-linking and curing proceeds under atmospheric pressure, and a foam is formed. Simultaneously with the progress of the crosslinking and curing, the water supplied in the steam mixed gas reacts with the isocyanate group of the prepolymer to generate carbon dioxide. Since the cross-linking and curing proceeds, the generated carbon dioxide forms the foam 3 without escaping outside. In addition, the foam 3 is formed in various shapes such as a circular shape and an elliptical shape in cross section.

(Slicing process)
As shown in FIG. 2, in the slicing step, the foam obtained in the curing molding step is sliced into a sheet shape to form the polishing pad 1. A general slicing machine can be used for slicing. At the time of slicing, the lower layer portion of the 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. Further, in the 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 of the foam is not used due to scratches and the like. 10 to 25 polishing pads 1 can be formed from 30 mm. Since a foam in which the foam 3 is substantially uniformly formed is obtained in the hardening molding process, when a plurality of polishing pads 1 are formed in the slicing process, the average value of the hole diameters of the openings 4 formed on the surface Are in the range of 10 to 100 μm. Further, in each polishing pad 1, the difference in the average opening diameter of the openings 4 is in a range of ± 3% with respect to the average value, and the difference in density is in a range of ± 3% with respect to the average value. If the average aperture diameter of the apertures 4 is less than 10 μm, clogging is easily caused by the abrasive particles in the polishing liquid during the polishing process, so that the life of the polishing pad is likely to be shortened. It becomes difficult to control the hole diameter, and the flatness of the object to be polished is not sufficiently improved. In addition, the magnitude | size of the foam 3 and by extension, the hole diameter of the opening 4 can be controlled by adjusting the quantity and mixing conditions of the water-vapor mixed gas mixed with a liquid mixture.

(Lamination process)
In the laminating process, the polishing pad 1 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. The processing surface of the object to be polished is polished by rotating the polishing platen while applying pressure to the object to be polished and supplying a polishing liquid (slurry) containing abrasive particles.

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

  In this embodiment, the water vapor mixed gas is mixed with the liquid mixture prepared in the mixing step. The fine bubbles generated when this steam mixed gas is mixed are dispersed almost evenly in the liquid mixture, so that a bubbling effect is produced and the water in the steam mixed gas is contained almost evenly in the fine foaming. It is. For this reason, the water in the steam mixed gas is dispersed substantially uniformly in the mixed liquid. Since substantially uniformly dispersed water reacts with the isocyanate groups of the prepolymer to generate carbon dioxide, foaming is formed. Therefore, the foam 3 having a substantially uniform size is substantially formed inside the foam obtained in the curing molding process. Formed evenly distributed. Thereby, since the opening 4 is formed substantially uniformly and substantially uniformly on the surface (polishing surface P) of the polishing pad 1 obtained by slicing in the slicing step, stable polishing performance can be ensured. . Moreover, since the water vapor in the water vapor mixed gas is not a gas after exhibiting the bubbling effect, it is possible to suppress the generation of extra giant bubbles. Furthermore, by mixing the mixed liquid as a water vapor mixture with the liquid mixture, water dispersion due to the mixer 20 is less likely to occur, so that foaming can be made uniform. Further, the amount of the steam mixed gas to be mixed is adjusted to a ratio of 0.5 to 3.4 liters with respect to 1 kg of the total weight of the prepolymer and the chain extender. For this reason, since the quantity of the water-vapor mixed gas in a liquid mixture is restrict | limited, it can suppress that an extremely big foam is formed inside the obtained foam. Thereby, the magnitude | size of the foam 3 formed in the inside of a foam can be equalize | homogenized. Therefore, in the polishing process using the polishing pad 1, the polishing liquid can be supplied substantially evenly between the object to be polished and the polishing pad 1 while holding the polishing liquid in the opening 4, and the flatness of the object to be polished. Can be improved.

Moreover, in this embodiment, the quantity of the water mixed with a liquid mixture is set to 200-3000 g / m < ³ >. For this reason, it is possible to suppress the formation and bias of extremely large foams due to excessive water. Furthermore, in this embodiment, water is mixed with a liquid mixture as water vapor | steam mixed gas. Conventional CMP soft polishing pads reduce (eliminate) urea bonds to make them mainly urethane bonds (only urethane bonds), so the pore size can be controlled by increasing the prepolymer viscosity and extending the solidification time during foam molding. It was difficult. On the other hand, in this embodiment, since the foaming reaction is also accelerated by mixing the steam mixed gas, the solidification time can be shortened, and the average pore diameter between the plurality of polishing pads obtained by slicing the foam Can be reduced. Therefore, by increasing the size of the foam (enlarging the mold 25), it is possible to easily meet the demand for larger size (area, thickness).

  Furthermore, since the polyol compound blended in the chain extender is present in the mixed solution, the hydroxyl group of the polyol compound reacts with the isocyanate group of the prepolymer to form a urethane bond. Plays a role in making changes less likely. For this reason, in the plurality of polishing pads 1 obtained by slicing the foam, all have the same wet hardness retention rate, that is, the same as water at a temperature of 70 ° C. with respect to the hardness when immersed in water at a temperature of 20 ° C. The ratio of hardness when immersed for a certain time can be 80% or more. In particular, the wet hardness retention can be improved by using PPG as the polyol compound. Therefore, in the polishing pad 1 having improved thermal stability in a wet state, even if heat is generated due to friction or the like during polishing using a slurry, the change in hardness is suppressed, and the polishing performance can be stabilized.

  Furthermore, in this embodiment, since the polishing pad 1 is obtained by the slice of the foam in which the substantially uniform foam 3 is formed substantially uniformly, the average value of the hole diameters of the openings 4 formed in the polishing surface P Is adjusted in the range of 10 to 100 μm. For this reason, the slurry is held in the opening 4 during polishing and is stably supplied to the processed surface (surface to be polished) of the object to be polished, so that the polishing efficiency can be improved. Further, when a plurality of polishing pads 1 are formed from a foam, the difference in average opening diameter and the difference in (apparent) density of the openings 4 formed on the respective surfaces are within a range of ± 3%. Can be inside. When the variation in the aperture diameter increases, the aperture 4 is likely to be locally clogged by abrasive particles (abrasive grains), polishing scraps, etc. in the slurry during the polishing process, and the flatness of the object to be polished is lowered. Further, since the hardness becomes too small (soft) when the density is reduced, it is difficult to improve the flatness of the object to be polished. On the contrary, if the density is increased, the hardness is increased too much, so that the polishing efficiency is lowered and the object to be polished is easily damaged. In the present embodiment, since the average opening diameter of the openings 4 is equal between the plurality of polishing pads 1, local clogging can be suppressed. In addition, since the proportion of the space occupied by the foam 3 in each polishing pad 1 is equal and the hardness is also equal, even if the polishing pad 1 is replaced, it is possible to suppress variation in polishing performance.

  Furthermore, in this embodiment, the viscosity of the prepolymer at a temperature of 50 to 80 ° C. is set in a range of 500 to 4000 mPa · s. For this reason, since the movement of foaming is suppressed in the mixed solution, the unevenness of foaming can be suppressed and the foaming can be dispersed substantially uniformly. Further, in the mixing step, the mixture is prepared under conditions of a shear rate of 9,000 to 41,000 / second and a shearing frequency of 300 to 10,000. For this reason, since the water in water vapor | steam mixed gas is disperse | distributed substantially equally, the dispersion state of the foam 3 can be equalized.

In the present embodiment, an example in which a water vapor mixed gas containing water is mixed with a liquid mixture has been described, but the present invention is not limited to this. Instead of the steam mixed gas, the steam itself may be mixed. Also in this case, it adjusts so that the quantity of the water contained in water vapor | steam may be 200-3000 g / m < ³ >. Moreover, since the amount of water contained in the water vapor is the same as that in the case of the water vapor mixed gas, the amount supplied to the mixing tank 12 is also adjusted to be the same.

  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.

  Furthermore, in this embodiment, although the example which mixes and uses MOCA of a polyamine compound and PPG of a polyol compound was shown as a chain extender, this invention is not limited to this. Any compound that can react with the terminal isocyanate group of the prepolymer and has active hydrogen in the molecule may be used, and the molecular weight is not particularly limited. Considering mixing with the prepolymer, the viscosity of the chain extender is preferably adjusted to the same level as that of the prepolymer, and the chain extender preferably contains a high molecular weight polyol compound.

  Furthermore, in the present embodiment, an example in which the mixing step, the casting step, and the curing molding step are performed continuously has been shown, but the present invention is not limited to this, and each step is performed independently. May be. In the present embodiment, an example is shown in which casting is performed from the mixer 20 to the mold 25 and molding is performed under atmospheric pressure, but the present invention is not limited to this. For example, the liquid mixture may be prepared in a container and cured and molded in the container, or the container may be sealed and cured and molded under pressure. Furthermore, in the present embodiment, a mixed liquid in which an isocyanate group-containing compound, a water vapor mixed gas, and a chain extender are mixed is used. If necessary, fillers such as cerium oxide, zirconium oxide, and titanium oxide, pigments, surface activity You may add additives, such as an agent and a catalyst, suitably.

  Further, although not particularly mentioned in the present embodiment, the polishing surface P of the polishing pad 1 may be grooved in consideration of supply of slurry and discharge of polishing waste. 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. When grooving is performed on the polishing pad, for example, if an opening having a large hole diameter is formed on the surface of the polishing pad, the opening and the groove overlap to form a protrusion-like corner, and therefore, the polishing pad is covered during polishing. Scratches will occur in the polished material. In this embodiment, since the opening 4 of the polishing pad 1 is substantially uniform in the range of 10 to 100 μm in the average value of the hole diameter, it is possible to suppress the generation of scratches on the object to be polished even if groove processing is performed.

  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. Further, 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 by changing the supply amount and flow rate of the steam mixed gas according to the present embodiment will be described. A comparative example prepared for comparison is also shown.

(Example)
In the examples, as shown in Table 1 below, the polishing pads 1 of Sample 1 to Sample 4 were produced by changing the supply amount and flow rate of the water vapor mixed gas. A terminal isocyanate group-containing urethane prepolymer (Adiprene L-325) having an isocyanate group content of 9 to 9.3% was used as the first component prepolymer, which was heated to 55 ° C. and degassed under reduced pressure. As the second component chain extender, MOCA was dissolved at 120 ° C. The third component is a PPG having a number average molecular weight of about 2000 as a chain extender, and further a part of a catalyst (Toyocat ET, manufactured by Tosoh Corporation), a silicon surfactant (SH-193, manufactured by Dow Corning). Were added and mixed with stirring, and then degassed under reduced pressure. The prepolymer: MOCA: PPG was supplied to the mixing vessel 12 so that the weight ratio was as shown in Table 1 below. 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, the steam mixed gas was supplied into the mixing tank 12 in the amount, temperature, and flow rate of water shown in Table 1 below. The obtained mixed liquid was poured into a mold 25 and cured, and then the formed foam was extracted from the mold 25. This foam was sliced to a thickness of 1.3 mm to produce a polishing pad 1.

(Comparative example)
In the comparative example, as shown in Table 1 below, polishing pads of Sample 5 to Sample 7 were manufactured by changing the amount of water supplied and the method of supplying water. That is, in the sample 5, 2 parts of water is directly supplied to the mixing tank 12 with respect to 1000 parts of the prepolymer, and only the non-reactive gas not containing water is adjusted to a temperature of 30 ° C. to 0.6 liter / solid content. Sample 1 was used except that it was supplied to mixing tank 12 at a flow rate of 1 kg. Sample 6 was the same as Sample 5 except that 2 parts of water per 1000 parts of the prepolymer were mixed with PPG in advance and supplied to the mixing tank 12. Sample 7 was the same as Sample 5 except that water was not supplied.

  About each sample of an Example and a comparative example, evaluation of the homogeneity by the measurement of a density and an aperture diameter, and heat resistance by the measurement of wet hardness and hardness retention rate were performed. Each measurement item was measured by the following measurement method.

(Evaluation of homogeneity)
In the evaluation of homogeneity, the density and pore diameter of the polishing pad 1 obtained by slicing from the upper layer part, middle layer part and lower layer part of the cured molded foam are measured, and the homogeneity is determined from the difference in the measured values in each layer. Evaluated. The density was calculated from the volume obtained from the size obtained by measuring the weight of the sample cut into a predetermined size. In addition, the aperture diameter was observed with a microscope (manufactured by KEYENCE, VH-6300) by enlarging the range of about 1.3 mm by 175 times, and the obtained image was image processing software (Image Analyzer V20LAB Ver.1. It processed and calculated by 3). At this time, the presence / absence of extremely large pores (large pores of 500 μm or more) was also determined.

(Evaluation of heat resistance)
In the evaluation of heat resistance, wet (WET) hardness and hardness retention were measured for the polishing pad 1 obtained from the middle layer of the foam. The wet hardness was determined by immersing the polishing pad 1 in water at a temperature of 20 ° C. for 30 minutes, and then measuring the Shore A hardness as the hardness according to Japanese Industrial Standard (JIS K 7311). The hardness retention is determined by immersing the same polishing pad 1 in hot water at a temperature of 70 ° C. for 30 minutes, measuring the Shore A hardness in the same manner, and determining the percentage of the hardness at 70 ° C. relative to the hardness at 20 ° C. as a percentage. It was. Table 2 shows the results of evaluation of density, average pore diameter, wet hardness, hardness retention rate, and presence / absence of giant pores.

  As shown in Tables 1 and 2, in Comparative Sample 5 and Sample 6 in which water and a non-reactive gas were mixed, the average pore diameter was large and the density was small. In addition, variation was observed in the upper layer, middle layer, and lower layer, and giant pores were also observed. On the other hand, in the sample 7 of the comparative example in which only the non-reactive gas was supplied without supplying water, the average pore diameter was smaller than those of the samples 5 and 6, but the density increased correspondingly and no giant pores were recognized. Variations were observed in each layer. On the other hand, in the sample 1 and sample 2 of the example in which the steam mixed gas was supplied, both the density and the average pore diameter are substantially uniform (within ± 3% of the average value) in the upper layer, the middle layer, and the lower layer. In addition, it was found that the wet hardness and hardness retention rate were also excellent. In the sample 3 of the example in which the flow rate of the steam mixed gas was 11.0 liters / solid content 1 kg, the flow rate was too high, so the average pore diameter was increased and the density was decreased. On the other hand, in sample 4 of the example in which the flow rate of water vapor was 0.3 liter / solid content 1 kg, the flow rate was too small, and therefore, the average pore diameter and density varied in each layer. From this, it was found that it is preferable to adjust the flow rate of water vapor to 0.5 to 3.4 liters / solid content of 1 kg.

From the above results, the polishing pad 1 obtained by slicing a foam formed from a mixture of a water vapor mixed gas containing 200 to 3000 g / m ^{3 of} a prepolymer, a chain extender, and water is substantially uniform on the surface. It became clear that the open holes 4 were formed substantially evenly. For this reason, since polishing liquid is hold | maintained at the opening 4 at the time of a grinding | polishing process, it turns out that polishing liquid can be supplied substantially uniformly between to-be-polished objects and a polishing pad, and the flatness improvement of to-be-polished objects can be anticipated. did.

  Since the present invention provides a polishing pad capable of improving the flatness of an object to be polished by forming holes substantially uniformly and substantially uniformly and a method for manufacturing the polishing pad, the present invention contributes to the manufacture and sales of the polishing pad. Have industrial applicability.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing pad 3 Foaming 4 Opening hole P Polishing surface 20 Mixer

Claims (9)

Gas mixture and an isocyanate group-containing compound, a chain extender, and non-reactive gas with the water vapor to water a 200g ^/ m 3 ~3000g / m steam or the isocyanate group-containing compound containing ³ and the chain extender And a polishing pad obtained by slicing a foam formed from a mixed liquid.   2. The polishing pad according to claim 1, wherein the isocyanate group-containing compound has a viscosity at a temperature of 50 ° C. to 80 ° C. in a range of 500 mPa · s to 4000 mPa · s.   The polishing pad according to claim 1, wherein an opening is formed on a surface of the foam slice, and an average opening diameter of the opening is in a range of 10 μm to 100 μm.   2. The polishing pad according to claim 1, wherein the ratio of the hardness when immersed in water at a temperature of 70 ° C. for 80 hours or more to the hardness when immersed in water at a temperature of 20 ° C. for a certain time is 80% or more. .   When a plurality of polishing pads were formed with the slices of the foam, the difference in the average hole diameter of the holes formed on the respective surfaces and the difference in density were both ± 3% of the average value. The polishing pad according to claim 1, wherein the polishing pad is within a range. And an isocyanate group-containing compounds, while mixing the chain extender, the steam and non-reactive gas to water to 200g ^/ m ³ ~3000g / m 3 including water vapor or the isocyanate group-containing compound and the chain extender A foam formation step of preparing a liquid mixture while blowing a mixed gas and forming a foam from the liquid mixture;
A slicing step of slicing the foam formed in the foam forming step to form a polishing pad;
A method for producing a polishing pad comprising:   The manufacturing method according to claim 6, wherein, in the foam formation step, the foam is continuously formed after preparing the mixed solution.   The amount of water vapor or mixed gas blown in the foam forming step is a ratio of 0.5 to 3.4 liters per 1 kg of the total weight of the isocyanate group-containing compound and the chain extender. Item 7. The manufacturing method according to Item 6.   The manufacturing method according to claim 6, wherein in the foam formation step, the mixed solution is prepared under conditions of a shear rate of 9,000 to 41,000 / second and a shearing frequency of 300 to 10,000.

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