JP5254727B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad including a polishing layer having a polishing surface for polishing an object to be polished and a cushion layer bonded to a surface opposite to the polishing surface.

  In materials (objects to be polished) such as semiconductor devices, since surface flatness is required, polishing using a polishing pad is performed. As a method for flattening the surface of a semiconductor device or the like, a chemical mechanical polishing (hereinafter abbreviated as CMP) method is generally used. In the CMP method, a so-called free abrasive grain method is generally employed in which a slurry (polishing liquid) in which abrasive grains (polishing particles) are dispersed in an alkali solution or an acid solution is supplied during polishing. That is, a surface to be polished (hereinafter referred to as a processed surface) of an object to be polished is polished by a mechanical action by abrasive grains in the slurry and a chemical action by an alkali solution or an acid solution. With the advancement of flatness required for the processed surface, polishing characteristics such as polishing accuracy and polishing efficiency required for the CMP method, in other words, performance required for the polishing pad is also increasing. At the time of polishing, a polishing pad is attached to the polishing machine, and while supplying the slurry, the surface of the polishing layer (polishing surface) is pressed to the processing surface through the slurry with a polishing pressure of about 4 Psi (27580 Pa), for example. Polishing is performed.

  In such semiconductor devices, as the degree of integration of semiconductor circuits increases, miniaturization and multilayer wiring for the purpose of higher density have progressed, and a technique for further flattening the surface has become important. That is, in a semiconductor circuit, the interval is approximately 65 nm, whereas in a so-called next-generation semiconductor device that has been densified and miniaturized, the interval is narrowed to approximately 45 nm and tends to be further reduced. It is in. In addition, since a flexible copper wiring is used as the wiring material, it is necessary to significantly reduce the defect rate. For this reason, countermeasures for so-called low-pressure polishing, in which damage to an object to be polished is reduced by reducing the polishing pressure to, for example, about 2 Psi (13790 Pa), are being promoted.

  In order to improve the flatness of the object to be polished, it is necessary to perform polishing while pressing the polishing pad substantially uniformly against the entire processing surface. However, the object to be polished may have not only local unevenness but also unevenness such as waviness over the entire processed surface. When polishing is performed using a polishing pad having a low hardness polishing layer, the polishing pad can be pressed evenly against the processing surface to reduce waviness, etc. It is easy to invite a roll-off drooping, and it becomes difficult to flatten local unevenness of the object to be polished. On the other hand, when polishing is performed using a polishing pad having a high hardness polishing layer, local unevenness of the object to be polished can be flattened, but it is difficult to reduce waviness, etc. The polishing rate is lowered because the follow-up to the surface deteriorates. Therefore, a two-layer polishing pad intended to improve the uniformity of flatness (uniformity) of the entire processed surface by a low hardness cushion layer and to improve local flatness by a high hardness polishing layer. It is disclosed (for example, see Patent Document 1). On the other hand, in a polishing machine used for polishing, vibration is generated as the surface plate rotates. When such vibration is transmitted to the object to be polished, polishing spots are generated and the flatness of the processed surface is impaired. In particular, when a polishing pad having a high hardness polishing layer is used, a fatal defect such as a scratch may occur on the object to be polished by vibration from the polishing machine. For this reason, reducing the influence of vibration from the polishing machine is also important for improving the flatness of the object to be polished. As a measure to reduce the influence of vibration, vibration is polished by placing an anti-vibration sheet mainly composed of silicone on the holding surface (surface opposite to the processing surface) for holding the object to be polished by the polishing machine. A technique for making it difficult to be transmitted to an object is disclosed (for example, see Patent Document 2).

Japanese Patent No. 3685066 JP 2001-277107 A

  However, in the polishing pad of Patent Document 1, although the micro rubber A hardness of the polishing layer is 80 degrees or more, it is soft within the hardness range that can be measured by the micro rubber A hardness. This makes it difficult to flatten the local unevenness, and a sufficient polishing rate cannot be obtained. Further, in the polishing pad of Patent Document 1, since the volume elastic modulus of the cushion layer is 40 MPa or more, the repulsive force and the resistance force against the polishing pressure are increased. Therefore, the cushion layer is not easily deformed when low-pressure polishing is performed. It becomes difficult to improve Mitty. On the other hand, regarding the vibration of the polishing machine, the technique of Patent Document 2 can suppress the vibration transmitted to the object to be polished via the surface plate by the vibration-proof sheet, but the suppression of the vibration transmitted to the object to be polished is sufficient. I can't say that.

  An object of the present invention is to provide a polishing pad capable of reducing the influence of vibration from a polishing machine and improving the flatness of an object to be polished even under low pressure polishing.

  In order to solve the above-mentioned problems, a polishing surface for polishing an object to be polished is provided, and a Shore D hardness range of 60 to 80 degrees is disposed on the side opposite to the polishing surface of the polishing layer. And the volume modulus of elasticity is in the range of 10 MPa to 30 MPa, and the mechanical loss coefficient tan δ at a frequency of 1 Hz is in the temperature range of 25 ° C. to 80 ° C. A cushion layer for suppressing vibration transmission to a polished object, and an adhesive layer for bonding the polishing layer and the cushion layer together to supplementarily suppress vibration transmission to the object to be polished, In the polishing pad, the loss coefficient tan δ of the polishing layer, the cushion layer, and the adhesive layer as a whole is in the range of 0.05 to 0.2 in the temperature range.

  In the present invention, the polishing layer has a Shore D hardness in the range of 60 to 80 degrees, the bulk modulus is in the range of 10 MPa to 30 MPa, and the loss coefficient tan δ is in the range of 0.05 to 0.4. And a cushion layer for suppressing vibration transmission to the object to be polished are bonded together with an adhesive layer for supplementarily suppressing vibration transmission to the object to be polished, and the overall loss coefficient tan δ is 0.05. Since it is in the range of ~ 0.2, it is possible to reduce the influence of vibration from the polishing machine during polishing processing, and even in low-pressure polishing, the pressing force on the object to be polished is equalized, and the flatness of the object to be polished is reduced. Can be improved.

  In this case, it is preferable that the difference between the maximum value and the minimum value in the temperature range of 25 ° C. to 80 ° C. of the loss coefficient tan δ of the cushion layer is 0.07 or less. The cushion layer may be made of a polyurethane resin having a foam structure in which cells are formed substantially uniformly. You may form an adhesion layer with the at least 1 sort (s) of adhesive selected from an acrylic type, an epoxy type, and a urethane type. The compression elastic modulus of the polishing layer is preferably in the range of 50% to 75%. The polishing layer may be made of a polyurethane resin having a foam structure in which cells are formed substantially uniformly. The polishing layer may be grooved or embossed on the polishing surface side.

  According to the present invention, a polishing layer having a Shore D hardness in the range of 60 to 80 degrees, a volume elastic modulus in the range of 10 MPa to 30 MPa, and a loss coefficient tan δ in the range of 0.05 to 0.4. A cushion layer for suppressing vibration transmission to the object to be polished, and an adhesive layer for assisting in suppressing vibration transmission to the object to be polished, so that the overall loss coefficient tan δ is 0. Since it is in the range of .05 to 0.2, the influence of vibration from the polishing machine during polishing can be reduced, and the pressing force against the object to be polished is equalized even in low-pressure polishing, and the object to be polished is flat. The effect that it can improve property can be acquired.

  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, a polishing pad 20 of this embodiment is disposed on a polishing sheet (polishing layer) 1 having a polishing surface P for polishing an object to be polished, on the side opposite to the polishing surface P of the polishing sheet 1. A cushion sheet (cushion layer) 5 and an adhesive sheet (adhesive layer) 3 to which the polishing sheet 1 and the cushion sheet 5 are bonded are provided.

  The abrasive sheet 1 is a polyurethane sheet having a foam structure in which foams (cells) 2 are formed substantially uniformly inside, and has an isocyanate group-containing compound as a main component. Abrasive sheet 1 slices a foam obtained by casting and curing a mixed solution of an isocyanate group-containing compound, a dispersion obtained by dispersing and diluting water in advance in a polyol compound, and a curing agent (chain extender). It is formed by doing. That is, the polishing sheet 1 is dry-molded.

  The foam 2 formed inside the polishing sheet 1 is formed in a substantially circular cross section by water added to the dispersion during dry molding. That is, the polishing sheet 1 is formed so that a plurality of foams 2 overlap in the thickness direction, and is formed substantially evenly in two directions intersecting the thickness direction. Since the polishing sheet 1 is formed of a slice of foam, a part of the foam 2 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 20 to 100 μm. The polishing sheet 1 has adjusted Shore D hardness and compression elastic modulus. Shore D hardness and compression elastic modulus can be made into a desired numerical range by adjusting the composition of the abrasive sheet 1, the number and size of the foams 2, and the like. In this example, the Shore D hardness range of the polishing sheet 1 is adjusted to 60 to 80 degrees, and the compression elastic modulus range is adjusted to 50 to 75%. Moreover, the thickness of the polishing sheet 1 is set in the range of 1.3 to 2.5 mm.

  On the other hand, the cushion sheet 5 has an elastic property such as polyurethane, polyethylene, polybutadiene, silicone and the like, and rubber such as natural rubber, nitrile rubber, polyurethane rubber and the like, and has vibration damping properties to suppress vibration transmission to the object to be polished. It is formed into a sheet with the material it has. In this example, a cushion sheet 5 made of polyurethane resin that is desolvated with an aqueous coagulating liquid (coagulating liquid containing water as a main component) and formed into a sheet (wet film formation) is used. The cushion sheet 5 has a foam structure in which foam 6 is formed inside. The cushion sheet 5 is adjusted in volume elastic modulus and mechanical loss coefficient tan δ (hereinafter simply referred to as loss coefficient). The loss factor is one of the indexes used for evaluating the vibration damping property of the material. The material having a larger loss factor has a higher vibration damping property. The loss coefficient is represented by loss coefficient = [loss elastic modulus (E ″) / storage elastic modulus (E ′)]. However, since it varies depending on the temperature and the frequency, in this example, 25 to 25 at a frequency of 1 Hz. The numerical value obtained at a heating rate of 5 ° C./min in the temperature range of 80 ° C. is defined as the loss coefficient, which depends on the composition of the cushion sheet 5, the number and size of the foam 6, the thickness, etc. In this example, the cushion sheet 5 is adjusted to have a bulk modulus of 10 to 30 MPa and a loss factor of 0.05 to 0.4, and the change of the loss factor with respect to temperature. The difference between the maximum value and the minimum value in the temperature range of 25 to 80 ° C. of the loss coefficient is adjusted to 0.07 or less, and the loss coefficient in the temperature range of 25 to 80 ° C. Change graph (characteristic diagram) changes To have no points, i.e., when a plot of loss factor for the temperature graph and is adjusted such that there is no inflection point in the graph of the loss factor in the temperature range of 25 to 80 ° C..

  The polishing sheet 1 and the cushion sheet 5 are bonded together with an adhesive sheet 3. The pressure-sensitive adhesive sheet 3 can be formed of at least one pressure-sensitive adhesive selected from, for example, acrylic, epoxy, and urethane. In this example, an acrylic adhesive is used and the thickness is set to 0.1 mm. The pressure-sensitive adhesive sheet 3 formed of such a pressure-sensitive adhesive plays a role of supplementarily suppressing vibration transmission to the object to be polished. For this reason, in this example, the whole loss coefficient of the polishing sheet 1, the cushion sheet 5, and the adhesive sheet 3 is in the range of 0.05 to 0.2.

(Manufacture of polishing pad)
The polishing pad 20 is manufactured through each process shown in FIG. That is, it is manufactured through an abrasive sheet forming step for forming the abrasive sheet 1, a cushion sheet forming step for forming the cushion sheet 5, and a joining step for joining the formed abrasive sheet 1 and cushion sheet 5 with the adhesive sheet 3. Hereinafter, it demonstrates in order of a process.

<Formation of polishing sheet>
In the polishing sheet forming step, the polishing sheet 1 is dry-molded. That is, a preparation step of preparing an isocyanate group-containing compound, a dispersion obtained by dispersing and diluting water in a polyol compound, and a curing agent, respectively, and mixing the isocyanate group-containing compound, the dispersion and the curing agent to prepare a mixed solution A mixing step, a casting step for injecting the mixed liquid into the mold, a curing molding step for foaming and curing in the mold to mold the foam, and slicing the foam into a sheet to form a plurality of polishing sheets 1 It is formed through a slicing step. Hereinafter, it demonstrates in order of a step.

  In the preparation step, an isocyanate group-containing compound, a dispersion obtained by dispersing and diluting water in a polyol compound, and a curing agent are prepared. As an isocyanate group-containing compound to be prepared, an isocyanate-terminated urethane prepolymer (hereinafter referred to as “polyisocyanate-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. , Simply 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 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 2 formed in the 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 2 that is substantially uniformly dispersed in the obtained 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 producing the prepolymer 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 polytetramethylene glycol (PTMG). Polyether polyol compounds such as, 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, a high molecular weight polyol compound such as a polycaprolactone polyol compound, etc. Can be used. Two or more of these polyol compounds may be used in combination.

  The polyol compound used for preparing the dispersion 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, PTMG, polyethylene glycol, polypropylene glycol ( Any high molecular weight polyol compound such as PPG) can be used. Since it becomes easy to disperse water uniformly in the mixing step by setting it to the same level as the viscosity of the solution of the prepolymer or the curing agent, it is preferable to use a polyol compound having a number average molecular weight of 500 to 2,000, and in particular, a number average molecular weight of 1,000 to 1,000. 2000 PPG is preferable in terms of dispersibility and heat resistance of the resulting polishing pad. In this example, PPG having a number average molecular weight of about 2000 is used in order to make the Shore D hardness and compression elastic modulus of the polishing sheet 1 within the above-described ranges, and water is dispersed at a ratio of 0.01 to 6% by weight. Dilute to prepare 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. By changing the amount of the dispersion liquid, the size and amount (number) of the foams 2 formed inside the polishing sheet 1 can be controlled. In this example, the amount of water is prepared such that the amount of water is 0.01 to 6 g with respect to 1 kg of the weight of the prepolymer mixed in the mixing step of the next step. For example, when the weight of the prepolymer is 1 kg and the dispersion is 100 g, the amount of water contained in this dispersion is 0.01 to 6 g.

  The curing agent is an organic compound having at least two active hydrogen groups, and examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, 3′-dichloro-4,4′-diaminodiphenylmethane (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5 -Bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2 , 6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl Polyamines exemplified by diphenylmethane, etc., or ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butyl Diol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene And low molecular weight polyols such as These may be used alone or in combination of two or more. In this example, MOCA is used as a curing agent. MOCA is used in a state where it is heated to about 120 ° C. and melted.

  In the mixing step, the prepolymer prepared in the preparation step, the dispersion, and the curing agent are mixed to prepare a mixed solution. In the casting step, the liquid mixture prepared in the mixing step is poured into a mold, and in the curing molding step, the foam is molded by foaming and curing in the mold. In this example, the mixing step, the casting step, and the curing molding step are performed continuously.

  In the mixing step, each component prepared in the preparation step is mixed with a mixer to prepare a mixed solution. The mixer includes a mixing tank with a built-in stirring blade. On the upstream side of the mixing tank, a supply tank containing a prepolymer as a first component, a MOCA of a curing agent as a second component, and a dispersion as a third component is arranged. The supply port from each supply tank is connected to the upstream end of the mixing tank. 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. The stirring blade is fixed to a rotating shaft extending from the upstream side to the downstream side at a substantially central portion in the mixing tank. As the rotating shaft rotates, the stirring blade rotates, and the first component, the second component, and the third component are sheared and mixed. In this example, the prepolymer: MOCA: dispersion was mixed in a weight ratio of 100 parts: 3-40 parts: 0.2-20 parts. The obtained mixed liquid is poured into the mold from a discharge port arranged at the downstream end of the mixing tank. In this example, the size of the mold is set to 1050 mm (length) × 1050 mm (width) × 50 mm (thickness).

  A 1st component, a 2nd component, and a 3rd component are supplied to a mixing tank, and are mixed with a stirring blade. By adjusting the shearing speed and the number of shearing of the stirring blade, each component is mixed substantially uniformly to prepare a mixed solution. When the shear rate of the stirring blade is too low, the size of the foam 2 formed in the obtained 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 and the mixed solution and the viscosity decreases, so that the bubbles in the mixed solution move (during molding) and the resulting foam Variation in the dispersed state of the foam 2 formed in the film tends to occur. On the other hand, if the number of times of shearing is too small, the size of the generated bubbles tends to be uneven (variation). On the other hand, if the number of shearing is too large, the viscosity decreases due to temperature rise, and the foam 2 is not formed substantially uniformly. In this example, in order to adjust the size and number of foams 2, in the mixing step, the shear rate is set in the range of 9,000-41,000 / second, the number of shears is set in the range of 300-10,000 times, and mixing is performed. To do. The mixing time (residence time) in the mixer 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 a mixed solution of about 100 kg in the casting 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 of blade tip of stirring blade (mm) × circumferential ratio × rotation speed of stirring blade (rpm) ÷ 60 ÷ clearance between blade tip of stirring blade and inner wall of mixing vessel (mm) ), The number of times of shearing (times) = the number of revolutions of the stirring blade (rpm) ÷ 60 × the residence time (seconds) of the mixed solution in the mixing tank × the number of blades of the stirring blade.

  In the casting step, the prepared mixed liquid is continuously poured from the mixer into the mold. When pouring the mixed liquid, the mixed liquid from the mixer is discharged from the discharge port of the mixing tank and, for example, through a flexible pipe, into a liquid injection port having a triangular cross section that reciprocates between two opposing sides of the mold. Introduce liquid. 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 solution is cast substantially evenly.

  In the curing molding step, the cast mixture is reacted in the mold to form a foam. At this time, the prepolymer is crosslinked and cured by the reaction between the prepolymer and the curing agent. 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 forms the foam 2. The foam 2 is formed in various shapes such as a circular shape and an elliptical shape in cross section.

  In the slicing step, the foam obtained in the curing molding step is sliced into sheets to form a plurality of polishing sheets 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. In addition, in the foam molded by the mold 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, and about 30 mm in the center portion. 10 to 25 polishing sheets 1 are formed. Since the foam in which the foam 2 is substantially uniformly formed is obtained in the curing molding step, in the plurality of polishing sheets 1 formed in the slicing step, the average value of the diameters of the openings 4 formed on the surface is Both are in the range of 20-100 μm.

<Cushion sheet formation>
In the cushion sheet forming step, the cushion sheet 5 is wet-formed. That is, a preparation step for preparing a resin solution in which a polyurethane resin is substantially uniformly dissolved in an organic solvent, the resin solution prepared in the preparation step is spread in a sheet shape, and the organic solvent is removed from the resin solution in an aqueous coagulation solution. A solidification regeneration step in which a polyurethane body is coagulated and regenerated by making a solvent, and a polyurethane body that has been coagulated and regenerated in the coagulation regeneration step is washed and dried to form a cushion sheet 5, and is formed through each step of the washing and drying step. These will be described in the order of steps.

  In the preparation step, a polyurethane resin and an additive are dissolved in an organic solvent to prepare a resin solution. The resin solution is prepared by dissolving the polyurethane resin and additives almost uniformly in a water-miscible organic solvent capable of dissolving the polyurethane resin, removing aggregates and the like by filtration, and then defoaming under vacuum. . As the organic solvent, N, N-dimethylformamide (hereinafter abbreviated as DMF), dimethylacetamide (hereinafter abbreviated as DMAc), or the like can be used. In this example, DMF is used as the organic solvent. As the polyurethane resin, a polyester resin, a polyether resin, a polycarbonate resin, or the like is selected and used. As additives, pigments such as carbon black, hydrophilic activators that promote foaming, and hydrophobic activators that stabilize the coagulation and regeneration of polyurethane resins can be used. By changing the type and amount of the additive, the size and amount (number) of the foam 6 formed inside the cushion sheet 5 can be controlled. The volume modulus and loss factor of the cushion sheet 5 can be adjusted by setting the polyurethane resin, the selection of the organic solvent, the mixing ratio of the resin and the organic solvent, the size and amount of the foam 6, and the thickness of the cushion sheet 5. . In this example, 45 to 62 parts of polyurethane resin and 8 to 30 parts of DMF are set to 100 parts of the resin solution, respectively.

  In the coagulation regeneration step, the polyurethane resin is coagulated and regenerated into a sheet by continuously applying the resin solution prepared in the preparation step to the film-forming substrate (spreading into a sheet) and immersing it in an aqueous coagulation liquid. . The resin solution prepared in the preparation step is applied substantially uniformly to the belt-shaped film forming substrate at a normal temperature by a coating machine such as a knife coater. At this time, the coating thickness (coating amount) of the resin solution is adjusted by adjusting the gap (clearance) between the coating machine and the film forming substrate. In this example, the application amount is adjusted so that the thickness of the cushion sheet 5 is in the range of 0.4 to 1.0 mm. A flexible film, a nonwoven fabric, a woven fabric, etc. can be used for the film-forming substrate. When using non-woven fabrics or woven fabrics, pre-treatment (sealing) soaking in water or DMF aqueous solution (mixed solution of DMF and water) or the like in advance to suppress penetration into the film-forming substrate during application of the resin solution ) Is performed. In the case where a flexible film made of PET or the like is used as the film forming substrate, pretreatment is not necessary because it does not have liquid permeability. In this example, a PET film is used as the film formation substrate.

  The film-forming substrate to which the resin solution is applied is immersed in an aqueous coagulating liquid whose main component is water which is a poor solvent for the polyurethane resin. In the aqueous coagulation liquid, first, micropores constituting a skin layer are formed on the surface of the applied resin solution over a thickness of about several μm. Thereafter, the polyurethane body is coagulated and regenerated into a sheet form on one side of the film forming substrate by the progress of substitution between the DMF in the resin solution and the aqueous coagulating liquid. By removing DMF from the resin solution and replacing DMF and the aqueous coagulating liquid, a large number of foams 6 are formed in the polyurethane body inside the skin layer, and the foams 6 communicate with each other in a three-dimensional network (not shown). The communication hole is formed. At this time, since the PET film of the film forming substrate does not penetrate water, desolvation occurs on the surface side (skin layer side) of the resin solution, and foam 6 having a larger pore diameter on the film forming substrate side than the surface side is formed. Is done. That is, inside the polyurethane body, a large number of foams 6 having a substantially triangular cross section rounded along the thickness direction of the polyurethane body are formed in a substantially uniformly dispersed state.

  In the cleaning / drying step, the belt-like (long) polyurethane body coagulated and regenerated in the coagulation regeneration step is washed and dried to form the cushion sheet 5. That is, the polyurethane body is peeled off from the film-forming substrate and washed in a cleaning liquid such as water to remove DMF remaining in the polyurethane body. In this example, cleaning was performed using warm water to enhance the cleaning effect. After washing, the polyurethane body is dried with a cylinder dryer. The cylinder dryer includes a cylinder having a heat source therein. The polyurethane body is dried by passing along the peripheral surface of the cylinder, and the cushion sheet 5 is formed.

<Joint process>
In the bonding step, the formed abrasive sheet 1 and cushion sheet 5 are bonded (bonded) with the adhesive sheet 3. The pressure-sensitive adhesive sheet 3 serves to supplementarily suppress vibration transmission to the object to be polished, and the overall loss factor of the polishing sheet 1 and the cushion sheet 5 bonded together with the pressure-sensitive adhesive sheet 3 is 0.05 to 0.2. The composition and thickness of the pressure-sensitive adhesive sheet 3 are set so as to be in the range. In this example, the pressure-sensitive adhesive sheet 3 is formed using an acrylic pressure-sensitive adhesive so as to have a thickness of 0.1 mm. That is, the acrylic adhesive is applied to the surface opposite to the polishing surface P of the polishing sheet 1 to a substantially uniform thickness. The polishing sheet 1 and the cushion sheet 5 are brought into pressure contact with the surface opposite to the polishing surface P of the polishing sheet 1 and the surface of the cushion sheet 5 (the surface on which the skin layer is formed) via the applied adhesive. Are bonded together with an adhesive sheet 3. Then, after cutting into a desired shape such as a circle, inspection such as confirming that there is no adhesion of dirt, foreign matter, etc. is performed to complete the polishing pad 20.

  When polishing the object to be polished with the obtained polishing pad 20, for example, a single-side polishing machine is used. In a single-side polishing machine, a polishing surface plate on which a polishing pad 20 for polishing an object to be polished is mounted and a holding surface plate for holding the object to be polished are disposed opposite to each other. At the time of polishing, the polishing pad 20 is mounted on the polishing surface plate, and the object to be polished is held on the holding surface plate. While pressing the polishing object held on the holding surface plate toward the polishing pad 20 and rotating the polishing surface plate or holding surface plate while supplying the polishing liquid from the outside, one side (processing surface) of the polishing object Polish the side. At the time of polishing, the temperature of the polishing pad 20 rises to approximately 30 to 40 ° C. due to frictional heat. Further, the vibration generated in the polishing machine is related to the number of rotations of the polishing surface plate or holding surface plate. For example, when polishing is performed by rotating a polishing platen or holding platen at a rotation number of 60 rpm, vibration with a frequency of about 1 Hz is generated.

(Action etc.)
Next, the operation and the like of the polishing pad 20 of this embodiment will be described.

  In the present embodiment, the loss coefficient of the cushion sheet 5 is adjusted to the above-described range of 0.05 to 0.4. When the loss factor is smaller than 0.05, the elasticity of the cushion sheet 5 becomes too large, and thus there is a possibility that the influence of vibration from the polishing machine cannot be reduced. On the other hand, when the loss coefficient is larger than 0.4, the vibration energy absorbed by the cushion sheet 5 increases, and therefore the cushion sheet 5 deteriorates due to the heat generated by converting the vibration energy into heat, and the polishing pad 20 In the polishing process by the CMP method, chemical polishing is promoted by the generated heat, and the object to be polished may be excessively polished. Further, if the difference between the maximum value and the minimum value of the loss coefficient in the temperature range of 25 to 80 ° C. is greater than 0.07, the elastic characteristics of the cushion seat 5 greatly change due to the temperature rise during the polishing process. It becomes difficult to perform stable polishing. When the loss factor has an inflection point in the temperature range of 25 to 80 ° C., the response (elasticity and absorption) to the vibration of the cushion seat 5 changes when the temperature rises beyond the inflection point. there's a possibility that. In this embodiment, the loss coefficient at a frequency of 1 Hz is in the temperature range of 25 to 80 ° C., and the difference between the maximum value and the minimum value is 0.07 or less and the change of the loss coefficient with temperature is small. Even if the temperature rises, the cushioning property is maintained and stable polishing can be performed.

  Moreover, in this embodiment, the cushion sheet 5 can reduce the influence of vibration from the polishing machine during the polishing process, and the adhesive sheet 3 that joins the polishing sheet 1 and the cushion sheet 5 to the object to be polished. Suppresses vibration transmission in an auxiliary manner. For this reason, since the loss coefficient of the polishing pad 20 as a whole is in the range of 0.05 to 0.2, the influence of the vibration of the polishing machine can be reduced during the polishing process, and the flatness of the object to be polished can be improved. .

  Furthermore, in this embodiment, the polishing sheet 1 is in the range of Shore D hardness 60 to 80 degrees, the compression elastic modulus is in the range of 50 to 75%, and the volume elastic modulus of the cushion sheet 5 is in the range of 10 to 30 MPa. . When the Shore D hardness of the polishing sheet 1 is less than 60 degrees, it becomes difficult to flatten fine irregularities by low-pressure polishing. On the other hand, when the Shore D hardness is larger than 80 degrees, abrasive particles or the like are strongly rubbed against the object to be polished, and scratches may occur on the processed surface of the object to be polished. Further, since the polishing rate tends to decrease as the hardness of the polishing sheet 1 increases, the compression elastic modulus is set to the above-described range in order to avoid this. When the compressive elastic modulus is less than 50%, the retention of the slurry is improved and the polishing rate is improved. However, the response time required for recovery of deformation of the polishing pad 20 is long, so it is difficult to flatten the processing surface. Become. On the other hand, when the compression elastic modulus is larger than 75%, the elasticity is too large and the retention of the slurry is lowered, so that the polishing rate is lowered and the efficiency of the polishing process is deteriorated. On the other hand, when the volume elastic modulus of the cushion sheet 5 is smaller than 10 MPa, it is difficult to perform stable polishing because the cushion sheet 5 may be greatly deformed. On the other hand, when the volume modulus of elasticity is greater than 30 MPa, the cushion sheet 5 is not easily deformed, and thus it is difficult to reduce the swell over the entire surface of the object to be polished. In the present embodiment, the cushioning property of the cushion sheet 5 is optimized by setting the volume modulus of elasticity to the above-described range, and the processed surface is pressed almost uniformly by the polishing sheet 1, so even when low-pressure polishing is performed. Further, it is possible to reduce waviness and improve flatness uniformity (uniformity) over the entire processed surface. Further, since the hardness and rigidity of the polishing sheet 1 are larger than those of the cushion sheet 5, it is possible to polish only fine convex portions of the processed surface while ensuring a polishing rate, and improve the local flatness of the object to be polished. Can be made. Therefore, it can be suitably used for polishing processing of a so-called next-generation type semiconductor device or the like whose density has been increased and miniaturized.

  Furthermore, in this embodiment, the polishing rate is ensured even when low-pressure polishing is performed as described above. For this reason, the object to be polished can be polished in a short time, the load on the polishing pad 20 can be reduced, and the life of the polishing pad 20 can be improved. Further, by polishing the object to be polished in a short time, the consumption of slurry can be reduced, so that the cost of polishing can be reduced.

  In the present embodiment, the example in which the difference between the maximum value and the minimum value in the temperature range of 25 to 80 ° C. of the loss coefficient of the cushion sheet 5 is set to 0.07 or less, but the present invention is limited to this. It is not something. Considering the responsiveness to the vibration of the cushion sheet 5 due to the temperature change, it is preferable that the difference between the maximum value and the minimum value of the loss coefficient is 0.05 or less.

  Moreover, in this embodiment, the prepolymer which reacted the polyol compound and the diisocyanate compound was illustrated as a prepolymer at the time of formation of the polishing sheet 1, However, This invention is not limited to this. As long as the Shore D hardness and compression modulus of the polishing sheet 1 described above can be satisfied, for example, an active hydrogen compound having a hydroxyl group, an amino group, or the like is used instead of the polyol compound, and a polyisocyanate compound or its compound is used instead of the diisocyanate compound. You may make it obtain by using these and making these react. In addition, since various kinds of isocyanate-terminated prepolymers are commercially available, commercially available products can be used. Furthermore, although the example which uses MOCA as a hardening | curing agent and uses distilled water in order to form the foam 2 was shown, this invention is not limited to this. Usually used curing agents and foam forming means may be used.

  Furthermore, although the example which uses a polyurethane resin as the cushion sheet 5 was shown in this embodiment, this invention is not limited to this. For example, other materials having elasticity and vibration damping properties such as resins such as polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber may be used. Also, the foam structure is not particularly limited, and may not have a foam structure.

  Furthermore, in the present embodiment, an example in which an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive sheet 3 and the thickness of the pressure-sensitive adhesive sheet 3 is 0.1 mm is shown, but the present invention is not limited to this. Instead of the acrylic adhesive, another adhesive such as epoxy or urethane may be used. Two or more pressure-sensitive adhesives may be combined. The thickness of the pressure-sensitive adhesive sheet 3 is not particularly limited. However, in consideration of the polishing performance of the polishing pad 20 and the suppression of vibration transmission to the object to be polished, about 0.05 to 0.2 mm. It is preferable to make it. Furthermore, at the time of manufacturing the polishing pad 20, an example of bonding on the surface (surface on which the skin layer is formed) side of the cushion sheet 5 is shown, but the present invention is not limited to this, and bonding is performed on the opposite side. May be.

  Furthermore, although not particularly mentioned in the present embodiment, the polishing surface P of the polishing pad 20 may be grooved or embossed. In the low-pressure polishing process, the surface plate is rotated at a high speed from the viewpoint of securing a polishing rate in order to reduce the pressing force on the object to be polished. For this reason, there is a possibility that a so-called hydroplaning phenomenon occurs in which the slurry exists in a layer form between the polishing surface P and the processing surface and hinders the polishing processing. This phenomenon can be suppressed by subjecting the polished surface P to grooving or embossing. In addition, it is possible to promote the discharge of polishing debris and the movement of the polishing liquid. The shape of the groove may be any of a radial shape and a spiral shape, and the cross-sectional shape may be any of a U shape, a V shape, and a semicircular shape. The pitch, width, and depth of the grooves are not particularly limited. In addition, in order to improve the flatness of the polishing pad 20, a surface grinding process such as a buff process may be performed on the polishing surface P side of the polishing pad 20 or on the surface side opposite to the polishing surface P.

  Further, in the present embodiment, although not particularly mentioned, for example, a double-sided tape or the like is bonded to the surface of the cushion sheet 5 opposite to the pressure-sensitive adhesive sheet 3, and the polishing pad 20 may be attached to the polishing machine. . At this time, the base material of the double-sided tape may also serve as a support layer for supporting the polishing pad 20, or another support layer such as a PET film may be bonded between the cushion sheet 5 and the double-sided tape. It may be. Further, instead of attaching the double-sided tape, for example, an adhesive or the like may be applied to the surface of the cushion sheet 5 opposite to the pressure-sensitive adhesive sheet 3 and the polishing pad 20 may be attached to the polishing machine.

  Furthermore, in this embodiment, an example of forming the sheet by slicing the foam at the time of forming the polishing sheet 1 is shown, but the present invention is not limited to this, for example, one sheet at a time It may be cured and molded into a shape. In this case, for example, the opening can be formed by buffing the polishing surface side.

  Furthermore, in this embodiment, although the example which uses DMF as an organic solvent at the time of manufacture of the cushion sheet 5 was shown, this invention is not restrict | limited to this. As long as the cushion sheet 5 satisfies the above-described bulk modulus and loss factor, for example, an organic solvent such as DMAc may be used in addition to DMF, or another organic solvent may be mixed with DMF.

  Hereinafter, examples of the polishing pad 20 manufactured according to the present embodiment will be described. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, a terminal isocyanate group-containing urethane prepolymer (Adiprene LF-700D) having an isocyanate group content of 8 to 8.5% was used as a prepolymer for the production of the polishing sheet 1, and this was heated to 55 ° C. under reduced pressure. Degassed underneath. The curing agent MOCA was dissolved at 120 ° C. and degassed under reduced pressure. The dispersion is composed of 50 parts of PPG having a number average molecular weight of about 2000, 2 parts of water, 1 part of a catalyst (Toyocat ET, manufactured by Tosoh Corporation), silicon surfactant (SH-193, manufactured by Dow Corning). ) Was added and mixed with stirring, and then degassed under reduced pressure. The prepolymer: MOCA: dispersion was mixed in a weight ratio of 100 parts: 25 parts: 5 parts. The obtained mixed liquid was cast and cured to obtain a foam. The foam was sliced to a thickness of 1.3 mm to prepare a polishing sheet 1. On the other hand, polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin for the production of the cushion sheet 5. To 100 parts of 30% polyurethane resin solution, 25 parts of DMF as a solvent, 40 parts of DMF dispersion containing 20% of carbon black as a pigment, and 2 parts of hydrophobic activator as a film forming stabilizer were added and mixed to form polyurethane. A resin solution was prepared. The obtained resin solution was applied with a thickness of 0.7 mm, and an organic solvent was removed from the resin solution in an aqueous coagulating liquid to prepare a cushion sheet 5. Polishing pad 20 of Example 1 was manufactured by bonding polishing sheet 1 and cushion sheet 5 with adhesive sheet 3 having a thickness of 0.1 mm, and bonding a double-sided tape to the surface of cushion sheet 5 opposite to adhesive sheet 3. .

(Comparative Example 1 and Comparative Example 2)
In Comparative Example 1, a polishing pad was produced in the same manner as in Example 1 except that a commercially available shock absorbing sheet (Miyasaka Rubber Co., Ltd., Miya Freak) was used as the cushion sheet. In Comparative Example 2, a polishing pad was produced in the same manner as in Example 1 except that the prepolymer: MOCA: dispersion was mixed at a ratio of 100 parts: 40 parts: 5 parts by weight in the production of the polishing sheet. That is, the polishing pad of Comparative Example 1 is obtained by bonding the same polishing sheet 1 as in Example 1 to a cushion sheet different from Example 1, and the polishing pad of Comparative Example 2 is an example of a polishing sheet different from Example 1. 1 is joined to the same cushion sheet 5.

(Evaluation of the physical properties)
The physical properties of the Shore D hardness and compression modulus of the polishing sheet used for the polishing pad of each Example and Comparative Example, and the volume modulus of elasticity and loss factor of the cushion sheet were measured. The Shore D hardness was determined from the indentation depth of the push needle pressed against the surface of the test piece via a spring in accordance with Japanese Industrial Standard (JIS K 6253). The compressive elastic modulus was determined using a shopper type thickness measuring instrument (pressure surface: circular shape with a diameter of 1 cm) in accordance with Japanese Industrial Standard (JIS L 1021). Specifically, the thickness t ₀ after pressing for 30 seconds with an initial load was measured, and then the thickness t ₁ after standing for 5 minutes under the final pressure was measured. All the loads were removed, and after standing for 5 minutes, the thickness t ₀ ′ after pressing for 30 seconds with the initial load again was measured. The compressive elastic modulus was calculated by compressive elastic modulus (%) = (t ₀ ′ −t ₁ ) / (t ₀ −t ₁ ) × 100. At this time, the initial load was 100 g / cm ² and the final pressure was 1120 g / cm ² . The bulk modulus was obtained using a bulk modulus measuring device (TMS manufactured by Toshiba Tungaloy Co., Ltd., UMS-MS). The loss factor was determined using a dynamic viscoelasticity measuring device (manufactured by TA Instruments Japan Co., Ltd., RSA-III). Specifically, the cushion sheets of Examples and Comparative Examples were press-molded using a 220 ° C. hot press to produce a film having a thickness of 0.1 mm, and a test piece (length × width = 5 mm × 30 mm) was prepared from this film. ) Was collected. The test piece was heated using a dynamic viscoelasticity measuring device at a frequency of 1 Hz and a temperature increase rate of 5 ° C./min in the temperature range of 25 to 80 ° C., and the storage elastic modulus ( E ′) and the loss modulus (E ″) were measured to calculate the loss factor. A graph (characteristic diagram) showing the change of the loss factor with respect to temperature is shown in FIG. 3. Shore D hardness, compression modulus, bulk modulus The measurement results are shown in Table 1. The maximum and minimum values of the loss coefficient in the temperature range of 25 to 80 ° C. are also shown in Table 1.

  As shown in Table 1, it was found that the abrasive sheet of Comparative Example 1 had a Shore D hardness of 51 degrees and a compression elastic modulus of 52%, and had a low hardness and was easily deformed. On the other hand, the polishing sheet of Comparative Example 2 showed a Shore D hardness of 72 degrees and a compression modulus of 65%, indicating that the hardness was high and deformation was difficult. On the other hand, the polishing sheet 1 of Example 1 has a Shore D hardness of 65 degrees and a compression modulus of 81%, is harder than the polishing sheet of Comparative Example 1, and hardly deforms. It was found that the hardness was lower than that of the sheet and it was easily deformed. Further, the cushion sheet of Comparative Example 1 showed a volume modulus of elasticity of 8 MPa, a maximum loss coefficient and a minimum value of 0.51 and 0.38, and was found to be easily deformed and have high vibration damping properties. On the other hand, the cushion sheet 5 of Example 1 and Comparative Example 2 has a volume modulus of 24 MPa, maximum values of loss coefficients, and minimum values of 0.28 and 0.25, which are deformed from the cushion sheet of Comparative Example 1. It was difficult to do so and it was found that the vibration damping property was low. Furthermore, as shown in FIG. 3, in Comparative Example 1, it was found that the loss coefficient has an inflection point in the temperature range of 25 to 80 ° C., and the change due to temperature is large. In contrast, in Example 1 and Comparative Example 2, it was found that there was no inflection point in the temperature range of 25 to 80 ° C., and the change due to temperature was small.

(Polishing performance evaluation)
Further, using the polishing pads of Examples and Comparative Examples, a silicon wafer having an oxide film surface having a diameter of 8 inches was polished under the following polishing conditions, and the polishing rate was measured. The polishing rate is the amount of polishing per minute expressed by thickness, and was calculated from the polishing amount obtained from the weight reduction of the silicon wafer before and after polishing, the polishing area of the silicon wafer, and the specific gravity. Further, the flatness of the processed surface after polishing was evaluated. The thickness was measured at an arbitrary 49 points in the processed surface after polishing, and the average value R and standard deviation σ of the polishing rate were determined, and the flatness (%) = (σ / R) × 100 was determined. A smaller flatness value indicates flattening. The measurement results of the polishing rate and flatness are shown in Table 2 below.
(Polishing conditions)
Polishing machine used: Speedfam, 9B-5P polishing machine Temperature: 25 ° C
Polishing platen rotation speed: 100rpm
Polishing head rotation speed: 97 rpm
Processing pressure: 2Psi (13790Pa)
Slurry: Colloidal silica slurry (pH: 11.5)
Slurry supply amount: 100cc / min
Workpiece: silicon wafer having an oxide film surface with a diameter of 8 inches

  As shown in Table 2, since the polishing pad of Comparative Example 1 has low hardness and is easily deformed, the followability to the processed surface is improved and the polishing rate is 1900 Å / min, which is higher than Example 1, but the deformation Therefore, the flatness of the processed surface deteriorated to 12% due to the influence of roll-off (see also Table 1). On the other hand, since the polishing pad of Comparative Example 2 has high hardness, it is difficult to follow the processed surface, the polishing rate is as low as 1500 Å / min, and it is difficult to deform and has a small loss factor. The influence of vibration could not be reduced, and the difference in polishing amount between the wafer outer peripheral part and the central part became large, and the flatness became 8% (see also Table 1). On the other hand, the polishing pad 20 of Example 1 was excellent at a polishing rate of 1800 ｍｉｎ / min. Moreover, the difference of the grinding | polishing amount in the outer peripheral part and center part of a to-be-polished object was also small, flatness showed 3%, and the flatness higher than Comparative Examples 1 and 2 was shown. From the above, by bonding the cushion sheet 5 to the polishing sheet 1 with the pressure-sensitive adhesive sheet 3, the flatness of the object to be polished can be improved at a sufficient polishing rate even if low-pressure polishing is performed with 2 Psi (13790 Pa). It became clear that we could do it.

  Since the present invention provides a polishing pad that can reduce the influence of vibration from a polishing machine and can improve the flatness of an object to be polished even under low pressure polishing, it contributes to the manufacture and sale of polishing pads. Have industrial applicability.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is process drawing which shows the principal part of the manufacturing method of the polishing pad of embodiment. It is a characteristic view which shows the change of the loss coefficient with respect to the temperature of the cushion sheet which comprises the polishing pad of an Example and a comparative example.

Explanation of symbols

1 Polishing sheet (polishing layer)
3 Adhesive sheet (adhesive layer)
5 Cushion sheet (cushion layer)
20 Polishing pad P Polished surface

Claims (7)

A polishing layer having a polishing surface for polishing an object to be polished and having a Shore D hardness range of 60 degrees to 80 degrees;
The polishing layer is disposed on the opposite side of the polishing surface, the bulk modulus is in the range of 10 MPa to 30 MPa, and the mechanical loss coefficient tan δ at a frequency of 1 Hz is 0.05 to 25 ° C. to 80 ° C. A cushion layer for showing a range of ~ 0.4 and suppressing vibration transmission to the object to be polished;
Bonding the polishing layer and the cushion layer, an adhesive layer for assisting in suppressing vibration transmission to the object to be polished;
With
The polishing pad, wherein the loss coefficient tan δ of the polishing layer, the cushion layer, and the adhesive layer as a whole is in the range of 0.05 to 0.2 in the temperature range.   2. The polishing pad according to claim 1, wherein the cushion layer has a difference between a maximum value and a minimum value in the temperature range of the loss coefficient tan δ of 0.07 or less.   The polishing pad according to claim 2, wherein the cushion layer is made of a polyurethane resin having a foam structure in which cells are substantially uniformly formed.   The polishing pad according to claim 1, wherein the adhesive layer is formed of at least one adhesive selected from acrylic, epoxy, and urethane.   The polishing pad according to claim 1, wherein the polishing layer has a compression elastic modulus in a range of 50% to 75%.   The polishing pad according to claim 5, wherein the polishing layer is made of a polyurethane resin having a foam structure in which cells are substantially uniformly formed.   The polishing pad according to claim 1, wherein the polishing layer is grooved or embossed on the polishing surface side.

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