JP2011073085A - Polishing pad - Google Patents

Abstract

A polishing pad capable of improving the flatness of an object to be polished is provided.
A foamed sheet 2 made of a polyurethane resin for a polishing pad 10 is provided. The foam sheet 2 is formed by forming foam 3 into a continuous foam shape. The foamed sheet 2 contains hollow resin fine particles 4 in a thickness range of 50% with respect to the entire thickness from the polished surface P so that 60% or more of the resin particles 4 are localized. A grinding process is performed on the polishing surface P side of the foam sheet 2, and the fine particles 4 are opened on the polishing surface P side to form openings 5. The foam sheet 2 is formed per unit area of the polishing surface P, and the number of the openings 5 formed by the fine particles 4 is larger than the number of the openings formed by the foam 3 among the openings having an opening diameter exceeding 1 μm. It is formed to be large. The dispersed supply of slurry is made uniform.
[Selection] Figure 1

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad provided with a resin foam having a polishing surface for polishing an object to be polished, in which foam is formed into a continuous foam by a wet film forming method.

  Conventional materials such as lenses, parallel flat plates, reflection mirrors, hard disk substrates, semiconductors, silicon wafers for semiconductor devices, glass substrates for liquid crystal displays, etc. Polishing using a polishing pad is performed. In semiconductor devices, as the degree of integration of semiconductor circuits increases rapidly, miniaturization and multilayer wiring for the purpose of higher density have progressed, and techniques for flattening the polished surface have 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.

  In general, a chemical mechanical polishing (hereinafter abbreviated as CMP) method is used as a polishing method for hard disk substrates, semiconductor device silicon wafers, and the like. 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 alkaline solution or an acid solution is supplied during polishing. That is, the object to be polished (the processed surface thereof) is polished by a mechanical polishing action by abrasive grains in the slurry and a chemical polishing 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.

  In the CMP method, a polishing pad having a polyurethane foam is widely used. In the production of such a polishing pad, a polishing pad provided with a polyurethane resin foam formed by a wet film forming method and a dry molding method is used. In the wet film forming method, a resin solution in which a polyurethane resin is dissolved in a water-miscible organic solvent is applied to a sheet-shaped film forming substrate, and then the resin is solidified and regenerated into a sheet form in an aqueous coagulating liquid. In the obtained foam, a large number of foams are formed inside the polyurethane resin due to coagulation regeneration. That is, it has a surface layer (skin layer) in which micropores are formed on the polishing surface side for polishing the object to be polished, and foam is continuously formed inside the surface layer. Usually, an opening is formed on the surface (polished surface) by performing grinding treatment or dressing treatment (light sanding) on the surface layer side. On the other hand, in the dry molding method, a polyurethane foam having a foam structure is formed by curing an isocyanate group-containing compound and an active hydrogen compound by reaction. In order to form a foam structure, for example, a technique of mixing hollow spherical fine particles having a resinous outer shell (see Patent Documents 1 to 5), a technique of adding water (see Patent Document 6), an inert gas, and the like (See Patent Document 7) and a technique for mixing water-soluble fine particles (see Patent Document 8). The surface of the obtained polyurethane foam is ground, or the polyurethane foam is sliced into a sheet to produce a polishing pad having openings formed on the surface. In the polishing pad manufactured by these techniques, the slurry is held in the opening formed in the polishing surface during the polishing process, so that the object to be polished can be polished by the free abrasive grain method.

Japanese Patent No. 3013105 Japanese Patent No. 3425894 Japanese Patent No. 3801998 JP 2006-186394 A JP 2007-184638 A JP 2005-68168 A Japanese Patent No. 3455208 JP 2000-34416 A

  However, in the techniques of Patent Document 6 to Patent Document 7, although pores are formed on the surface by water or inert gas, foaming failure may occur in the polyurethane foam due to the reaction of moisture with isocyanate groups, The foam structure is non-uniform. In the technique of Patent Document 8, pores are formed on the surface by elution of the water-soluble fine particles by slurry, but it is not easy to uniformly disperse the water-soluble fine particles in the polyurethane foam, and the pore sizes are not uniform. It is easy to become. In addition, since water-soluble fine particles tend to contain moisture, even a slight amount of moisture forms huge foam, the foam structure becomes uneven, and the supplied abrasive grains cause secondary agglomeration, scratching the processed surface of the workpiece. (Scratches) may occur. In this regard, in the techniques of Patent Documents 1 to 5, since hollow spherical fine particles are mixed, poor foaming can be suppressed. However, when the hollow spherical fine particles do not open on the polished surface, the hard spherical fine particles are hardened. In some cases, the outer shell component may cause scratches or the like as foreign matter, and reduce the flatness of the object to be polished.

  In view of the above-described case, an object of the present invention is to provide a polishing pad that can improve the flatness of an object to be polished.

  In order to solve the above problems, in a polishing pad comprising a resin foam in which foam is formed into a continuous foam by a wet film forming method and an opening is formed in a polishing surface for polishing an object to be polished. The foam contains a large number of hollow resin fine particles so as to be localized in a certain thickness range from the polished surface, and is formed per unit area of the polished surface and has an opening diameter exceeding 1 μm. Among the holes, the number of openings formed by the fine particles is larger than the number of openings formed by the foaming.

  In the present invention, since the number of openings formed by fine particles is larger than the number of openings formed by foaming among the openings formed per unit area of the polishing surface and having an opening diameter exceeding 1 μm, the polishing liquid is It can be held on the polishing surface substantially uniformly and can perform stable polishing processing, and the foaming is formed in a continuous foam shape to provide cushioning properties, so that the fine particles can be kept at a constant surface pressure on the polishing surface. Since it is supported, the effect of suppressing scratches is increased, and the flatness of the object to be polished can be improved.

In this case, the foam is preferably contained so that 60% or more of the fine particles are localized in a thickness range of 50% with respect to the entire thickness of the foam from the polished surface. In addition, when the foam is removed from the polished surface by 5% of the total thickness, the average pore diameter is in the range of 5 to 40 μm, and the number of apertures with an aperture diameter exceeding 50 μm is 10 / mm. It can be adjusted to ² or less. When the foam has a thickness of 50% of the entire thickness removed from the polished surface, the pore diameter may be more than 15 μm / mm ² . The Shore A hardness of the foam can be in the range of 20 to 90 degrees. The foam is preferably integrally formed by a wet film formation method. The fine particles preferably have a uniform pore size. The fine particles can be spherical or polyhedral. Furthermore, the foam may be continuously formed with micropores having a pore size smaller than that of the fine particles.

  According to the present invention, since the number of apertures formed by fine particles is larger than the number of apertures formed by foaming among the apertures formed per unit area of the polished surface and having an aperture diameter exceeding 1 μm, polishing is performed. The liquid is held almost evenly on the polishing surface and stable polishing can be performed, and the foaming is formed in a continuous foam shape to provide cushioning properties, so that the surface pressure of the polishing surface is constant. Since the fine particles are supported, the effect of suppressing scratches is enhanced, and the flatness of the object to be polished can be improved.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied.

  Hereinafter, embodiments of a polishing pad to which the present invention is applied will be described with reference to the drawings.

(Constitution)
As shown in FIG. 1, the polishing pad 10 of the present embodiment includes a foam sheet 2 as a resin foam. The foam sheet 2 is integrally formed of a polyurethane resin by a wet film forming method and has a substantially flat polished surface P.

  In this example, the foam sheet 2 has a surface layer (skin layer) on which fine micropores are formed during wet film formation removed by grinding or dressing, and a polished surface P is formed on the surface. The foam sheet 2 contains hollow resin fine particles 4 so as to be localized in a certain thickness range from the polishing surface P. The foamed sheet 2 is formed with a foam 3 having a triangular shape that is vertically long and round along the thickness direction of the foamed sheet 2. The foam 3 is formed such that the diameter on the polishing surface P side is smaller than the diameter on the surface opposite to the polishing surface P. That is, the diameter of the foam 3 is reduced on the polishing surface P side. In the polyurethane resin between the foams 3, micropores having a pore size smaller than that of the foams 3 are formed, but these micropores are omitted in FIG. 1. The foam 3 and the micropores are connected in a mesh pattern with communication holes (not shown). That is, the foam sheet 2 has a continuous foam structure formed by a wet film forming method.

  The fine particles 4 are contained in the foamed sheet 2 so that 60% or more is localized in a thickness range of 50% with respect to the entire thickness from the polishing surface P. The content of the fine particles 4 is set to a weight ratio of 1 to 50 parts with respect to 100 parts of the foamed sheet 2. 60% or more of the contained fine particles 4 are localized on the polishing surface P side. Since the foamed sheet 2 is subjected to a grinding process or a dressing process on the polishing surface P, some fine particles 4 located in the vicinity of the surface are opened on the polishing surface P to form openings 5. Among the openings formed per unit area of the polished surface P and having an opening diameter exceeding 1 μm, the number of the openings 5 formed by the fine particles 4 is formed to be larger than the number of the openings formed by the foam 3. Has been. Moreover, the pore diameter of the fine particles 4 is adjusted to a range of 5 to 40 μm and is adjusted to be uniform. For this reason, the slurry supplied during the polishing process is distributed and supplied substantially uniformly on the processed surface of the object to be polished.

  As the fine particles 4, spherical or polyhedral particles can be used. For example, microspheres in which low-boiling hydrocarbons are encapsulated and the outer shell is formed of a thermoplastic resin can be used. It is preferable that the softening temperature of the thermoplastic resin forming the outer shell is higher than the boiling point of the encapsulated low-boiling hydrocarbon. When the heat of the thermoplastic resin is higher than the softening temperature of the thermoplastic resin, the unexpanded fine particles are softened while the low-boiling hydrocarbons are vaporized and become hollow. Examples of the outer shell thermoplastic resin include acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, styrene polymer, silicone resin, urethane resin, amide resin, and the like. These outer shell thermoplastic resins are preferably stable with respect to a water-miscible organic solvent capable of dissolving the polyurethane resin used in the production of the foamed sheet 2, and are subjected to a crosslinking treatment or the like as necessary. It is preferable. Examples of the low-boiling hydrocarbons encapsulated include isobutane, pentane, isopentane, petroleum ether, and the like. By adjusting the amount of low-boiling hydrocarbons to be included, the particle size after expansion can be adjusted. In this example, the particle size of the expanded fine particles 4 is 5 to 5 in advance. The thing of the range of 40 micrometers is used.

The total thickness t of the foam sheet 2 is adjusted to a range of 0.3 to 3 mm. When the 5% thickness (0.05 t) is removed from the polishing surface P side with respect to the total thickness t, the average aperture diameter is 5 to 40 μm, and the aperture diameter exceeds 10 μm. It is adjusted so as to be less than pieces / mm ² . Further, when the thickness (0.5 t) of 50% of the entire thickness t is removed from the polishing surface P side, the number of apertures having a pore diameter exceeding 50 μm is 15 to 50 / mm ² . It has been adjusted to be. In the foam sheet 2, the Shore A hardness is adjusted to a range of 20 to 90 degrees. In this way, since the hardness of the foamed sheet 2 is optimized, the occurrence of scratches or the like can be reduced during polishing.

  The polishing pad 10 has a double-sided tape 6 attached to the surface opposite to the polishing surface P of the foam sheet 2 for mounting the polishing pad 10 on a polishing machine. The double-sided tape 6 has an adhesive layer on both surfaces of a substrate such as a polyethylene terephthalate (hereinafter abbreviated as PET) film. In FIG. 1, the base material and the adhesive layer are omitted. Examples of the adhesive of the adhesive layer include an acrylic adhesive. The double-sided tape 6 is bonded to the foam sheet 2 with an adhesive layer on one side, and the adhesive layer on the other side is covered with a release paper 7.

(Manufacturing)
The polishing pad 10 is a preparation step for preparing a resin solution in which a polyurethane resin is dissolved and containing fine particles 4, a coating step for continuously applying the resin solution to a film forming substrate, and a polyurethane resin in a sheet form in an aqueous coagulating liquid. Through a coagulation regeneration process for coagulation and regeneration, a washing / drying process for washing and drying the coagulated and regenerated polyurethane resin, a buffing process for making the thickness uniform by buffing, and a laminating process for attaching the double-sided tape 6 to the foamed sheet 2 Manufactured. Hereinafter, it demonstrates in order of a process.

  In the preparation step, polyurethane resin, N, N-dimethylformamide (hereinafter abbreviated as DMF), a water-miscible organic solvent capable of dissolving polyurethane resin, fine particles 4 and additives are mixed to dissolve the polyurethane resin. . The water-miscible organic solvent may be an organic solvent that mixes with water at an arbitrary ratio. In addition to DMF, for example, N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), Acetone or the like may be used. The polyurethane resin is selected from resins such as polyester, polyether, polycarbonate, and the like. For example, the polyurethane resin is dissolved in DMF so that the polyurethane resin becomes 30% by weight. The fine particles 4 are mixed and dispersed substantially uniformly. As additives, in order to control the length of foam 3 in the thickness direction and the number per unit volume, pigments such as carbon black, a hydrophilic activator that promotes the formation of foam, and the solidification regeneration of polyurethane resin are stabilized. A hydrophobic active agent or the like can be used. The obtained solution is degassed under reduced pressure to obtain a resin solution.

  In the application step, the resin solution obtained in the preparation step is continuously applied to the belt-shaped film forming substrate with a knife coater or the like at room temperature so as to be substantially uniform. At this time, the application thickness (application amount) of the polyurethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. A resin-made nonwoven fabric or film such as PET resin can be used for the film-forming substrate, but in this example, a PET film is used as the film-forming substrate.

  In the coagulation regeneration process, the resin solution applied to the film forming substrate is guided to a coagulation liquid mainly composed of water which is a poor solvent for the polyurethane resin. In the coagulation liquid, first, micropores are formed on the surface side of the applied resin solution, and a skin layer having a thickness of about several μm is formed. Thereafter, the polyurethane resin coagulates and regenerates into a sheet on the film-forming substrate as the substitution of the DMF in the resin solution and the coagulating liquid proceeds. When the DMF is removed from the resin solution and the DMF and the coagulating liquid are replaced, the foam 3 and the micropores are formed in the polyurethane resin inside the skin layer, and the foam 3 and the micropores communicate with each other in a mesh shape. At this time, since the PET sheet of the film forming substrate does not permeate water, desolvation occurs on the surface side (skin layer side) of the resin solution, and foam 3 having a larger film forming substrate side than the surface side is formed. As DMF is desolvated from the resin solution and moves to the surface side, the fine particles 4 are dispersed so as to be localized on the surface side.

  In the cleaning / drying process, the sheet-like polyurethane resin solidified and regenerated in the coagulation regeneration process (hereinafter referred to as a film-forming resin) is peeled off from the film-forming substrate, washed in a cleaning solution such as water and washed into the film-forming resin. Residual DMF is removed. After cleaning, the film forming resin is dried with a cylinder dryer. The cylinder dryer includes a cylinder having a heat source therein. The film-forming resin is dried by passing along the peripheral surface of the cylinder. The film-forming resin after drying is rolled up.

  In the buffing process, buffing is performed on the skin layer side formed on the surface of the film-forming resin. That is, the substantially flat surface of the pressure welding jig is pressed against the surface opposite to the skin layer of the film forming resin, and the buff treatment is performed on the skin layer side. Thereby, a part of the fine particles 4 are opened in the polishing surface P to form the openings 5, the thickness of the film forming resin is made uniform, and the foam sheet 2 is obtained.

  In the laminating process, the double-sided tape 6 is bonded to the surface opposite to the polishing surface P of the foam sheet 2. The other side of the double-sided tape 6 is covered with a release paper 7. The polishing pad 10 is completed by performing an inspection such as confirming that there is no adhesion of dirt or foreign matter.

(Action etc.)
Next, the operation and the like of the polishing pad 10 of this embodiment will be described.

  In the polishing pad 10 of the present embodiment, the fine particles 4 are contained so as to localize on the polishing surface P side of the foam sheet 2. On the polished surface P, apertures 5 are formed by the apertures of the fine particles 4. Of the openings formed per unit area of the polished surface P and having an opening diameter exceeding 1 μm, the number of the openings 5 formed by the fine particles 4 is larger than the number of the openings formed by the foam 3. For this reason, since the slurry supplied at the time of polishing is held in the opening 5 and contributes to the polishing by moving the processing surface of the object to be polished substantially uniformly, that is, the dispersion of the slurry is made uniform. Polishing characteristics such as polishing efficiency and polishing accuracy can be stabilized.

  Further, in the polishing pad 10 of the present embodiment, the foam 3 and the micropores are connected in a mesh shape with the communication holes, and are formed in a continuous foam shape. For this reason, the fine particles 4 are supported so that the surface pressure of the polishing surface P is constant by exhibiting cushioning properties during the polishing process. Thereby, since it is suppressed that a pressure rises locally by the outer shell of the fine particle 4, the suppression effect of a scratch increases and the flatness of a to-be-polished object can be improved.

  Furthermore, in the polishing pad 10 of the present embodiment, the fine particles 4 are contained so as to be localized 60% or more in a thickness range of 50% from the polishing surface P of the foam sheet 2 with respect to the total thickness. Fine particles 4 are opened to form openings 5. At the time of polishing, the polishing surface P side of the foam sheet 2 is worn. In addition, a dressing process is performed on the polishing surface P side in order to improve polishing efficiency. The fine particles 4 contained in the vicinity of the polishing surface P are opened at any time by dressing treatment or wear on the polishing surface P side, and the opening 5 is formed. For this reason, even if the wear progresses, the openings 5 are formed on the polishing surface P as needed, so that the slurry can be dispersed substantially uniformly on the processed surface of the object to be polished and the slurry retainability can be maintained. . If the fine particles 4 are not localized in the thickness range of 50% from the polishing surface P of the foam sheet 2 in the thickness range of 60% or more, the ratio of the fine particles 4 contained in the portion where the pore diameter of the foam 3 is large is obtained. Therefore, the ratio of the useless fine particles 4 not involved in the polishing is increased, and the stable cushioning property is easily impaired.

Furthermore, in the polishing pad 10 of this embodiment, when 5% of the total thickness is removed from the polishing surface P, the average opening diameter is in the range of 5 to 40 μm, and the opening diameter is 50 μm. The number of openings exceeding 10 holes / mm ² is adjusted. Further, when the thickness of 50% of the entire thickness is removed from the polished surface P, the number of apertures having an aperture diameter exceeding 50 μm is adjusted to a range of 15 to 50 holes / mm ² . That is, as the foam sheet 2 wears during polishing, the foam 3 opens and the hole diameter increases. For this reason, since the grinding | polishing waste (sludge) and the outer shell component of the microparticles | fine-particles 4 which generate | occur | produce by grinding | polishing enter in the foam 3, it can suppress that a scratch is formed in a to-be-polished object. If the average hole diameter when the thickness of 5% of the entire thickness is removed from the polished surface P is smaller than 5 μm, clogging due to polishing dust (sludge) and slurry aggregates is likely to occur, and conversely, 40 μm. If it is larger, it is difficult to obtain flatness of the object to be polished, which is not preferable. Further, if the opening diameter at this time exceeds 10 μm / mm ² , the flatness of the object to be polished is impaired. When removing 50% of the total thickness from the polished surface P, if the number of apertures exceeding 50 μm is less than 15 holes / mm ² , sufficient cushioning properties are difficult to obtain. On the contrary, if it is more than 50 / mm ² , the polishing surface pressure is likely to vary and the flatness of the object to be polished is impaired.

  Moreover, in the polishing pad 10 of this embodiment, the Shore A hardness of the foam sheet 2 is adjusted in the range of 20 to 90 degrees. For this reason, hardness is optimized, it becomes easy to remove wear debris from the polished surface P, and dressability can be improved. In addition, since there is no possibility of excessive wear, the polishing process can be continued for a long time, and the life can be extended.

  Furthermore, in the polishing pad 10 of this embodiment, the foam sheet 2 is integrally formed by a wet film forming method. For this reason, compared with what laminated | stacked another material on the foam sheet, it does not peel in the surface laminated | stacked during the grinding process. In addition, the bonded pad may cause uneven thickness of the polishing pad as the thickness increases, but the polishing pad 10 can prevent uneven thickness because the foamed sheet 2 is integrally formed, and the object to be polished can be prevented. The flatness of the film can be improved.

  Furthermore, in the polishing pad 10 of this embodiment, the fine particles 4 are spherical or polyhedral and are adjusted so as to have a uniform pore diameter. Thereby, the opening 5 can be easily formed so that an opening diameter becomes substantially uniform. Therefore, at the time of polishing, the slurry can move substantially uniformly on the processed surface of the object to be polished, the retention of the slurry is ensured, and clogging is suppressed, so that the polishing efficiency and polishing accuracy can be improved. it can. In addition, the formation of agglomerates such as abrasive particles is suppressed by preventing clogging without forming extremely large apertures, improving flatness without causing scratches on the workpiece. Can be made.

  In the present embodiment, a polyurethane resin sheet is exemplified as the foam sheet, but the present invention is not limited to this, and other resins may be used. For example, polyvinyl chloride resin or the like may be used. If a polyurethane resin is used, a continuous foam structure can be easily formed by a wet film forming method.

  In this embodiment, the polyurethane resin is coagulated and regenerated at the time of producing the foam sheet 2, and then the film forming substrate is peeled off and the double-sided tape 6 is bonded. However, the present invention is limited to this. Is not to be done. For example, after peeling off the film forming substrate, a support may be bonded between the double-sided tape 6 and the foamed sheet 2. Alternatively, after the polyurethane resin is solidified and regenerated, the film forming substrate may not be peeled off, and the double-sided tape 6 may be attached to use the film forming substrate as a support. For example, when a non-woven fabric is used as the film forming substrate, it is difficult to peel off the foamed sheet. Therefore, the film forming substrate may be dried as it is without being peeled off. That is, the non-woven fabric film forming substrate serves as a support for the polishing pad 10. Furthermore, as the double-sided tape 6, an adhesive may be applied to both surfaces of the base material, and may be composed of only the adhesive without having the base material.

  Furthermore, in this embodiment, the example in which the double-sided tape 6 is bonded to the foam sheet 2 is shown, but the present invention is not limited to this. For example, in the manufacturing process, for example, a PET-PU (polyurethane) copolymer resin is applied on a film-forming substrate, dried, and then polyurethane is formed on the side opposite to the film-forming substrate of the PET-PU copolymer resin. A resin solution may be applied to coagulate and regenerate the polyurethane resin. In this way, since the PET-PU copolymer resin serves as an adhesive for fixing and fixing the film forming substrate (support) and the polyurethane resin (foamed sheet), the foamed sheet and the support are supported during the polishing process. It can suppress that a body peels.

  Furthermore, in the present embodiment, an example in which the skin layer is removed by performing grinding processing on the polishing surface P side of the foam sheet by a buffing machine, a slicing machine, or the like is shown, but the present invention is not limited to this. . For example, grinding processing may be performed on the surface opposite to the polishing surface P side of the foam sheet 2. In this way, it is possible to improve the thickness variation and the like while leaving the skin layer. Further, the skin layer may be left without performing the grinding process on the polishing surface P side of the foam sheet 2.

  Furthermore, in the present embodiment, although not particularly mentioned, a light transmissive portion that allows light transmission for optically detecting the polishing state of the object to be polished is provided on the foam sheet 2, for example, a light transmissive portion. May be formed so as to penetrate through the entire thickness direction of the foam sheet 2. Forming the light transmission part can be realized, for example, by forming a through-hole in the foamed sheet 2 and fitting a member having light transmittance different from that of the foamed sheet 2 into the through-hole. Moreover, before the material which comprises the foam sheet 2 or the material which comprises a light transmissive part solidifies, it can also implement | achieve by making both contact and integrate. If the light transmission part is formed, for example, a light-emitting element such as a light-emitting diode provided on the polishing machine side, or a light-receiving element such as a phototransistor, the polishing state of the processing surface of the object to be polished through the light transmission part during polishing processing Can be detected. As a result, the end point of the polishing process can be properly detected, and the polishing efficiency can be improved.

  In the present embodiment, an example in which the foamed sheet 2 is formed with the foam 3 having a triangular cross section and the fine pores in a continuous foam shape is shown, but the present invention is not limited thereto. For example, by adding another organic solvent to the polyurethane resin solution in the preparation step and delaying the solidification of the polyurethane resin solution in the coagulation regeneration step, the micro-foam smaller than the foam 3 is uniformly formed in the thickness direction without forming the foam 3 Alternatively, a three-dimensional network may be formed. In this case, a polyurethane resin having a relatively low viscosity is used. Fine particles 4 having a small specific gravity are dispersed, applied to the film forming substrate, and then the fine particles 4 are localized on the opposite side of the film forming substrate, and then coagulated and regenerated. Let In this way, the fine particles 4 can be localized in a certain thickness range from the polishing surface, and polishing can be performed at a stable polishing rate as described above.

  Furthermore, in this embodiment, although the example using the microparticle 4 expanded beforehand was shown, this invention is not restrict | limited to this. For example, a state before the fine particles 4 are expanded may be used. In this case, the fine particles 4 expand when heated in the cleaning / drying process. In the present embodiment, the microspheres in which the low-boiling point hydrocarbons are encapsulated in the fine particles 4 are exemplified, but the present invention is not limited thereto. For example, a low-boiling hydrocarbon may not be encapsulated and may be originally hollow. Further, the outer shell may not be completely covered. For example, the outer shell may be hollow fine particles having a horseshoe shape or a semicircular shape with a cross section opened to such an extent that the polyurethane resin does not substantially fill the void. Further, the outer shell such as hollow silica or aluminosilicate microballoon may be made of an inorganic material.

  Next, examples of the polishing pad 10 manufactured according to the present embodiment will be described. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, polyester MDI (diphenylmethane diisocyanate) was used as the polyurethane resin. 10 parts of fine particles 4, 45 parts of DMF for viscosity adjustment, 40 parts of DMF dispersion containing 30% by weight of carbon black, 100 parts of a solution obtained by dissolving 30% by weight of this polyurethane resin in DMF, hydrophobic A polyurethane resin solution was prepared by mixing 2 parts of the surfactant. The fine particle 4 is an expanded spherical hollow fine particle (trade name: EXPANCEL 551 DE20 manufactured by Expancel Co., Ltd.) having a shell portion made of an acrylonitrile-vinylidene chloride copolymer and encapsulating isobutane gas in the shell. The average particle size is 20 μm. The obtained polyurethane resin solution was applied to a film forming substrate, and then coagulated and regenerated in a coagulating liquid. After washing and drying, the foam sheet 2 was produced, and the polishing pad 10 of Example 1 was produced.

(Comparative Example 1)
In Comparative Example 1, a polishing pad of Comparative Example 1 was produced in the same manner as in Example 1 except that the fine particles 4 were not contained. That is, Comparative Example 1 is a conventional polishing pad that does not contain fine particles 4.

(Evaluation 1)
With respect to the polishing pads of Example 1 and Comparative Example 1, the thickness, the average hole diameter on the polishing surface P, the number of holes with an opening diameter exceeding 50 μm, the localization rate of the fine particles 4 and the Shore A hardness of the foamed sheet were measured. In the thickness measurement, a dial gauge (minimum scale 0.01 mm) was used and a weight of 100 g / cm ² was applied. A foam sheet having a length of 1 m and a width of 1 m was read up to 1/10 (0.001 mm) of the minimum scale at a pitch of 10 cm in length and width, and the average value of the thickness was determined. In the Shore A hardness measurement, a sample piece (10 cm × 10 cm) is cut out from the foam sheet, and a plurality of sample pieces are stacked so that the thickness is 4.5 mm or more, and an A-type hardness meter (Japanese Industrial Standard, JIS K). 7311). For example, when the thickness of one sample piece was 1.4 mm, measurement was performed with four sheets stacked. In the measurement of the average hole diameter and the number of holes having an opening diameter exceeding 50 μm, a scanning electron microscope (JSM-5500LV, manufactured by JEOL Ltd.) expanded the range of about 1 mm square to 5000 times and observed nine places. This image was processed with image processing software (Image Analyzer V20LAB Ver. 1.3) to calculate the aperture diameter (average value) and the number of apertures. In the measurement of the localization rate of the fine particles 4, the cross section of the sample piece was enlarged 100 to 1000 times with a scanning electron microscope, the number of fine particles in the thickness direction with respect to a certain width was counted at nine places, and the thickness of the entire foam was measured. The proportion of fine particles in a thickness range of 50% with respect to the thickness was calculated. Table 1 below shows the measurement results of the thickness, the average pore diameter on the polished surface P, the number of apertures having an aperture diameter exceeding 50 μm, the localization rate of the fine particles 4 and the Shore A hardness of the foam sheet.

As shown in Table 1, in the polishing pad of Comparative Example 1, the average opening diameter of the openings formed when the thickness of 5% of the entire thickness was removed from the polishing surface was 35 μm, and the opening diameter was 24 holes / mm ² with a diameter exceeding 50 μm, and 22 holes / mm with an opening diameter exceeding 50 μm formed when the thickness of the polished surface is removed by 50% of the total thickness. ^2. A hardness was 38 degrees. On the other hand, in the polishing pad 10 of Example 1, the average aperture diameter is 20 μm, the number of apertures having an aperture diameter exceeding 50 μm is 5 / mm ² , and the thickness is 50% of the total thickness from the polishing surface. When the minute was removed, the number of apertures formed when the aperture diameter exceeded 50 μm was 21 holes / mm ² , and the A hardness was 42 degrees. In Comparative Example 1, fine particles 4 were not contained, and only the pores due to the foam 3 were formed. Therefore, the pore diameter formed when the thickness of 5% of the entire thickness was removed from the polished surface. Shows a large value of the number of openings exceeding 50 μm. On the other hand, in Example 1, since the fine particles 4 were contained, the number of pores having a pore diameter exceeding 50 μm was smaller than that in Comparative Example 1. For this reason, in Example 1, the slurry supplied to the apertures 5 by the fine particles 4 during the polishing process is easily held uniformly, and the uniform dispersibility of the slurry is ensured and the polishing characteristics can be improved. It is done. Further, in Example 1, among the openings formed per unit area of the polishing surface P and having an opening diameter exceeding 1 μm, the number of the openings 5 formed by the fine particles 4 is the number of the openings formed by the foam 3. Since it is larger than the number, the slurry is held substantially uniformly on the processed surface of the object to be polished, so that stable polishing characteristics can be expected. Furthermore, in Example 1, 75% of the fine particles 4 are localized in the thickness range of 50% from the polishing surface P to the entire thickness of the foam sheet 2, and from the polishing surface P to the entire thickness. Since 21 holes / mm ² having an opening diameter exceeding 50 μm formed when the thickness of 50% is removed are formed, stable cushioning properties can be expected.

(Evaluation 2)
Using the polishing pads of Example 1 and Comparative Example 1, the aluminum substrate was polished under the following polishing conditions. The appearance of the polished aluminum substrate was visually evaluated for the presence or absence of scratches on the surface.
(Polishing conditions)
Polishing machine used: Speedfam, 9B-5P polishing machine Polishing speed (rotation speed): 30 rpm
Processing pressure: 90 g / cm ²
Slurry: Alumina slurry (average particle size: 0.8 μm)
Slurry supply amount: 100cc / min
Object to be polished: 95 mmφ hard disk aluminum substrate polishing time: 300 seconds

  As a result of polishing with the polishing pad of Comparative Example 1 and evaluating the presence or absence of scratches, many scratches were observed on the surface of the aluminum substrate. On the other hand, when polishing was performed with the polishing pad 10 of Example 1 and the appearance was evaluated for the presence or absence of scratches, no scratches were found. This is because the continuous foam structure is formed in the polishing pad 10 of Example 1, so that cushioning properties are exhibited during the polishing process, and the fine particles 4 are supported so that the surface pressure of the polishing surface P is constant. This is considered to be because the effect of suppressing scratches was improved. Therefore, it has been found that the polishing pad 10 of Example 1 can ensure the slurry retention and improve the flatness of the object to be polished.

  Since the present invention provides a polishing pad that can improve the flatness of an object to be polished, it contributes to the manufacture and sale of the polishing pad, and thus has industrial applicability.

P Polished surface t Total thickness of foam 2 Foam sheet (resin foam)
3 Foam 4 Fine particles (resin fine particles)
5 Opening 10 Polishing pad

Claims (9)

  In a polishing pad comprising a resin foam in which foam is formed into a continuous foam by a wet film forming method and an opening is formed in a polishing surface for polishing an object to be polished, the foam is the polishing surface A large number of hollow resin fine particles are contained so as to be localized in a certain thickness range, and are formed with the fine particles out of the pores formed per unit area of the polished surface and having a pore diameter exceeding 1 μm. A polishing pad, wherein the number of openings formed is greater than the number of openings formed by the foaming.   2. The foam is contained so that 60% or more of the fine particles are localized in a thickness range of 50% with respect to the thickness of the whole foam from the polished surface. The polishing pad as described. The foam has an average opening diameter of 5 μm to 40 μm, and an opening diameter of 50 μm, when 5% of the total thickness is removed from the polished surface. The polishing pad according to claim 2, wherein the number of openings exceeds 10 holes / mm ² . The foam is formed by removing 50% of the total thickness from the polished surface, and the number of apertures having an aperture diameter exceeding 50 μm is 15 / mm ² to 50 / mm ² . The polishing pad according to claim 3, wherein the polishing pad is in a range.   The polishing pad according to claim 4, wherein the foam has a Shore A hardness in a range of 20 degrees to 90 degrees.   The polishing pad according to claim 5, wherein the foam is integrally formed by a wet film forming method.   The polishing pad according to claim 1, wherein the fine particles have a uniform pore diameter.   The polishing pad according to claim 7, wherein the fine particles are spherical or polyhedral.   The polishing pad according to claim 8, wherein the foam is continuously formed with micropores having a pore size smaller than the fine particles.

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