JP5189440B2 - Polishing method - Google Patents

Description

  The present invention relates to a polishing method, and in particular, a polishing pad having a polishing layer having a polishing surface having a polishing surface for polishing an object to be polished and having cells formed therein is mounted on a surface plate of a polishing machine. The present invention also relates to a polishing method for polishing an object to be polished with a polishing pad while supplying a polishing liquid.

  In materials (objects to be polished) such as semiconductor devices and glass substrates for liquid crystal displays, surface flatness is required, and therefore polishing using a polishing pad is performed. In semiconductor devices, as the degree of integration of semiconductor circuits rapidly increases, miniaturization and multilayer wiring for the purpose of higher density have progressed, and a technique for further flattening the surface has become important. On the other hand, with a glass substrate for a liquid crystal display, higher flatness of the surface is required as the liquid crystal display becomes larger.

  As a method for planarizing the surface of a semiconductor device, 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. In the CMP method, a polishing pad having a polishing layer mainly composed of a polyurethane resin that is hardly deteriorated by an alkali solution or an acid solution is widely used. At the time of polishing, the polishing pad is attached to the polishing machine, and the polishing is performed by bringing the surface of the polishing layer (polishing surface) into contact with the processing surface through the slurry while supplying the slurry.

  If the familiarity between the polishing pad and the slurry is poor during polishing, the slurry will be difficult to hold on the polishing pad, and the slurry will not spread over the entire processing surface, making it difficult to improve the polishing rate and causing scratches. It becomes easy. For this reason, the running-in operation is conventionally performed in order to improve the familiarity between the polishing pad and the slurry. However, this running-in operation takes time and causes a reduction in polishing efficiency. In view of this, a proposal has been made to improve the familiarity with the slurry by improving the hydrophilicity (wetting property) of the polishing layer. Specifically, a technique in which a polishing layer is formed from polyurethane containing a hydrophilic polyol component (see Patent Documents 1 and 2), a technique in which a hydrophilic polymer solid is internally added to a polishing layer component (patent) Document 3 and Patent Document 4) are disclosed respectively. However, in these polishing pads, since the entire polishing layer has hydrophilicity, the entire polishing layer swells due to moisture such as slurry during polishing, and physical properties such as hardness of the polishing layer are likely to change. It becomes difficult to sufficiently improve the flatness of an object. Therefore, a technique for hydrophilizing only the polishing surface side of the polishing layer by plasma treatment is disclosed (see Patent Document 5).

JP 2004-42250 A JP 2004-167680 A JP 2001-47355 A JP 2001-179608 A JP 2005-328881 A

  However, the polishing pad of Patent Document 5 is hydrophilized by introducing hydrophilic groups such as hydroxyl groups on the polishing surface side of the polishing layer with plasma generated with a large electric power of several tens of kV. At this time, a part of the main chain of the polymer material (resin) constituting the polishing layer may be cut, resulting in physical properties such as partial deterioration of the resin, and the deteriorated resin is polished. Since the processing surface may be damaged as a foreign object during processing, it becomes difficult to sufficiently improve 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 method capable of improving the flatness of an object to be polished.

In order to solve the above-described problems, the present invention includes a polishing layer having a foam structure having a polishing surface for polishing an object to be polished and having cells formed therein, and at least one polishing layer excluding the cells. A polishing pad comprising a partially acylated polysaccharide component which is partly acylated and is soluble in an organic solvent capable of dissolving the resin constituting the polishing layer and hardly soluble or insoluble in water A polishing process is performed with a polishing pad mounted in the mounting process while supplying an alkaline polishing liquid capable of deacylating the partially acylated polysaccharide component. The partially acylated polysaccharide contained in the polishing layer by infiltrating the polishing liquid into the polishing surface side of the polishing pad mounted in the mounting step in the polishing step. Small amount of ingredients Wherein a portion of the partially acylated polysaccharide component of Kutomo the polishing surface is deacylated.

In the present invention, a partially acylated polysaccharide component that is at least partially acylated, is soluble in an organic solvent capable of dissolving the resin constituting the polishing layer, and is hardly soluble or insoluble in water. Since the polishing pad provided in the mounting step with the contained polishing layer is supplied in the polishing step, at least a part of the partially acylated polysaccharide component on the polishing surface side is deacylated. The polishing surface side of the polishing layer is more hydrophilic and swellable than the portion excluding the polishing surface side of the polishing layer, and the swelling property over the entire thickness of the polishing layer is suppressed. Since the familiarity with the polishing liquid is improved and the retention of the slurry is ensured, the flatness of the object to be polished can be improved.

In this case, it is preferable that the polishing liquid supplied in the polishing step has a pH of 10 or more. Abrasive particles may be contained in the polishing liquid. The polishing layer of the polishing pad to be mounted in the mounting process can be mainly composed of polyurethane resin. Moreover, the partially acylated polysaccharide component may be contained in the polishing layer excluding the cell in a proportion of 5 wt% to 40 wt%. The partially acylated polysaccharide component contained in the polishing pad attached in the attaching step can be at least one selected from a reaction product of cellulose, chitosan or dextrin and a carboxylic acid derivative. At this time, the partially acylated polysaccharide component may be acetyl cellulose.

According to the present invention, a partially acylated polysaccharide which is a polysaccharide component which is at least partially acylated and which is soluble in an organic solvent capable of dissolving the resin constituting the polishing layer and hardly soluble or insoluble in water. The polishing pad equipped with the polishing layer containing the component and mounted in the mounting step is deacylated at least part of the partially acylated polysaccharide component on the polishing surface side by the polishing liquid supplied in the polishing step. The polishing surface side of the polishing layer is more hydrophilic and swellable than the portion excluding the polishing surface side of the polishing layer, and the swelling property over the entire thickness of the polishing layer is suppressed. Since the familiarity with the polishing liquid is improved and the retention of the slurry is ensured, the flatness of the object to be polished can be improved.

  Hereinafter, embodiments of a polishing method according to the present invention will be described with reference to the drawings.

(Polishing pad)
As shown in FIG. 1, a polishing pad 20 used in the polishing method of the present embodiment is a polishing sheet (polishing layer) 1 having a polishing surface P for polishing an object to be polished, the main component of which is polyurethane resin. I have. The abrasive sheet 1 is desolvated with a water-based coagulating liquid (coagulating liquid containing water as a main component) and formed into a sheet (wet film formation). The abrasive sheet 1 has a foam structure in which cells (foam) are formed. On the polishing surface P side of the polishing sheet 1, a skin layer (not shown) is formed in which fine pores (not shown) are densely formed over a thickness of about several μm. On the inner side of the skin layer of the polishing sheet 1, a large number of foams 2 having a substantially triangular cross-section rounded along the thickness direction of the polishing sheet 1 are formed in a substantially uniformly dispersed state. Foam 2 is formed such that the hole diameter on the polishing surface P side (upper side in FIG. 1) is smaller than the hole diameter on the surface side opposite to the polishing surface P (lower side in FIG. 1). Between the foams 2 inside the polishing sheet 1, foam (not shown) having a pore diameter smaller than the foam 2 is formed. The foam 2 and the foam (not shown) are communicated in a three-dimensional network through a communication hole (not shown).

  A partly acylated polysaccharide component as a polysaccharide component at least partially acylated is contained in the polishing sheet 1 excluding foam 2, foam not shown and communication holes not shown. That is, the partially acylated polysaccharide component is contained in the polyurethane resin that forms the polishing sheet 1. The partially acylated polysaccharide component is one in which an acyl group is introduced into at least a part of the hydroxyl group or amino group of the polysaccharide component. In this example, acetylcellulose having an acetylation degree of 54.3% and a polymerization degree of 270 is used as the partially acylated polysaccharide component, and is contained in the polishing sheet 1 in a proportion of 5 to 40% by weight. The degree of acetylation represents the percentage by weight of bound acetic acid per unit weight of cellulose. In this example, the acetylation degree is determined by ASTM: D-817-91 “Testing Method for Cellulose Acetate”. Measured accordingly.

  Also, on the opposite side of the polishing sheet 1 from the polishing surface P, a double-sided tape 7 for attaching the polishing pad 20 to the polishing surface plate of the polishing machine is bonded. The double-sided tape 7 has a base material 7a of a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET), and an acrylic adhesive or the like is not shown on both surfaces of the base material 7a. An adhesive layer is formed. The double-sided tape 7 is bonded to the polishing sheet 1 with an adhesive layer on one side of the base material 7a, and the adhesive layer on the other side (the side opposite to the polishing sheet 1) is covered with a release paper 7b.

(Production method)
The polishing pad 20 used in the polishing processing method of the present embodiment was prepared by a preparation step and a preparation step for preparing a solution (hereinafter referred to as a mixed solution) in which a polyurethane resin and acetylcellulose are substantially uniformly dissolved in an organic solvent. The mixed solution is spread in a sheet form, and the coagulation regeneration process (regeneration process) for coagulating and regenerating the polyurethane body containing acetylcellulose by desolvating the organic solvent from the mixed solution in the aqueous coagulation liquid, coagulating in the coagulation regeneration process. The recycled polyurethane body is manufactured through a cleaning / drying process for forming a polishing sheet 1 by cleaning / drying and a laminating process for applying a double-sided tape 7 to the polishing sheet 1. .

  In the preparation step, the polyurethane resin and the acetyl cellulose are respectively dissolved in the same organic solvent to prepare a polyurethane resin solution and an acetyl cellulose solution. The polyurethane resin solution is prepared by dissolving the polyurethane resin and additives almost uniformly in a water-miscible organic solvent that can dissolve the polyurethane resin, removing aggregates, etc. by filtration, and then degassing under vacuum. The The acetylcellulose solution is prepared by dissolving acetylcellulose substantially uniformly in the same organic solvent as the polyurethane resin solution and degassing under vacuum. A polyurethane resin solution and an acetylcellulose solution are mixed to prepare a mixed solution. In this example, a mixed solution is prepared so that acetylcellulose is contained in the polishing sheet 1 excluding foaming in a proportion of 5 to 40% by weight. As the organic solvent, a water-miscible organic solvent capable of dissolving a polyurethane resin such as N, N-dimethylformamide (hereinafter abbreviated as DMF) or dimethylacetamide (hereinafter abbreviated as DMAc) is used. it can. 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.

  In this example, acetylcellulose used as the partially acylated polysaccharide component can be dissolved in DMF because it has an acetylation degree of 54.3% and a polymerization degree of 270. In other words, the acetylation degree is adjusted so that the acetyl cellulose to be used can be dissolved in DMF. The degree of acetylation can be adjusted by acetylation conditions. In this example, the acetyl cellulose is one obtained by treating linter pulp having an α-cellulose content of 90 to 97% by the acetic acid method.

  In the coagulation regeneration step, the polyurethane solution is coagulated and regenerated into a sheet by continuously applying the mixed solution prepared in the preparation step to the film-forming substrate (spreading into a sheet) and immersing it in an aqueous coagulation solution. . That is, the organic solvent is removed from the mixed solution by a wet method. The mixed solution prepared in the preparation step is applied substantially uniformly to the belt-shaped film forming substrate with a coating machine such as a knife coater at room temperature. At this time, the coating thickness (coating amount) of the mixed solution is adjusted by adjusting the gap (clearance) between the coating machine and the film forming substrate. A flexible film, a nonwoven fabric, a woven fabric, etc. can be used for the film-forming substrate. When using a nonwoven fabric or a woven fabric, a pretreatment that is preliminarily immersed in water or an aqueous solution of DMF (mixed solution of DMF and water) in order to suppress the penetration of the mixed solution into the film-forming substrate when the mixed solution is applied. (Stop) 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 mixed solution has been 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 coagulating liquid, first, micropores constituting a skin layer are formed on the surface of the applied mixed liquid 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 as the substitution of DMF in the mixed liquid and the aqueous coagulating liquid proceeds, and acetylcellulose solidifies. That is, a polyurethane body in which acetylcellulose is dispersed substantially uniformly is formed. By removing DMF from the mixed liquid and replacing DMF and the aqueous coagulating liquid, a large number of foams 2 and foam (not shown) are formed in the polyurethane body inside the skin layer. A communication hole (not shown) that communicates in a three-dimensional network is formed. At this time, since the PET film of the film formation substrate does not allow water to permeate, desolvation occurs on the surface side (skin layer side) of the mixed solution, and an opening is formed on the surface side. Foam 2 having a larger pore diameter than the side is formed.

  In the washing / drying step, the belt-like (long) polyurethane body coagulated and regenerated in the coagulation regeneration step is washed and dried to form the abrasive sheet 1. 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. 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 polishing sheet 1 is formed.

  In the laminating step, the other surface side of the double-sided tape 7 covered with the release paper 7b is pasted with an adhesive layer on the side opposite to the skin layer of the polishing sheet 1 formed in the cleaning / drying step. After cutting into a desired size and shape, an inspection such as confirmation that there is no adhesion of dirt or foreign matter is performed, and the polishing pad 20 is completed.

(Polishing method)
As shown in FIG. 3, the polishing method of this embodiment includes a mounting step of mounting the polishing pad 20 on a polishing surface plate of a polishing machine, and a polishing pad mounted in the mounting step while supplying an alkaline polishing liquid. 20 is carried out through each step of the polishing step of polishing the object to be polished.

  Here, the polishing machine will be described. Examples of the polishing machine include a single-side polishing machine that polishes one surface of an object to be polished and a double-side polishing machine that polishes both surfaces of the object to be polished. In a single-side polishing machine, a polishing surface plate on which a polishing pad for polishing an object to be polished is mounted and a holding surface plate for holding the object to be polished are opposed to each other. At the time of polishing, a polishing pad is mounted on the polishing surface plate, and the object to be polished is held on the holding surface plate. One side (processing surface) side of the object to be polished by pressing the object to be polished held on the holding surface plate toward the polishing pad and rotating the polishing surface plate or holding surface plate while supplying the polishing liquid from the outside. Is polished. On the other hand, in the double-side polishing machine, two polishing surface plates are arranged opposite to each other. At the time of polishing, each polishing pad is mounted on the polishing surface plate, pressed to sandwich the object to be polished with the polishing pad, and at least one of the polishing surface plates is rotated while supplying the polishing liquid from the outside. Polish both sides of the polished object. In this example, a single-side polishing machine is used as the polishing machine.

(Installation process)
In the mounting step, the polishing pad 20 is mounted on the polishing surface plate of a single-side polishing machine. When the polishing pad 20 is mounted on the polishing surface plate, the release paper 7b of the double-sided tape 7 is removed, and the surface is adhered and fixed to the polishing surface plate with the exposed adhesive layer. On the other hand, a holding tool for holding an object to be polished is attached to the holding surface plate. In this example, a wet-formed polyurethane sheet is used as the holder.

(Polishing process)
In the polishing step, an object to be polished is removed with the polishing pad 20 mounted in the mounting step while supplying an alkaline polishing liquid capable of deacetylating (deacylating) the acetylcellulose contained in the polishing sheet 1 excluding foaming. Polishing. In this example, a colloidal silica slurry of pH 10 in which colloidal silica (abrasive particles) having a particle diameter of 75 nm is dispersed substantially uniformly in an alkaline solution containing potassium hydroxide as an alkaline polishing liquid capable of deacetylating acetylcellulose. Is used. The work surface is polished by a mechanical action by colloidal silica and a chemical action by making it alkaline.

  Here, the hydrophilization and swelling of the polishing sheet 1 in the polishing step will be described. On the polishing surface P of the polishing sheet 1, fine pores of the skin layer associated with solvent removal are formed. Inside the polishing sheet 1, foam is formed that communicates in a three-dimensional network. For this reason, the alkaline solution of the slurry supplied in the polishing step infiltrates substantially evenly on the polishing surface P side of the polishing sheet 1. Further, in the polishing process, the polishing surface or holding surface plate is rotated while the polishing surface P of the polishing pad 20 and the processing surface of the object to be polished are brought into pressure contact with each other through a slurry. The temperature rises to about 30-40 ° C.

  As shown in FIG. 2, at least a portion of acetylcellulose deacetylates on the polishing surface P side of the polishing sheet 1 due to an increase in temperature due to the alkaline solution and frictional heat infiltrated into the polishing sheet 1, and A surface layer 1a having a substantially uniform thickness is formed over the entire surface. On the other hand, the polishing sheet 1 excluding the surface layer 1a (hereinafter referred to as the inner layer 1b) is less likely to infiltrate the alkaline solution, and the contained acetylcellulose is less likely to be deacetylated. For this reason, in the acetyl cellulose contained in the surface layer 1a, the proportion of hydroxyl groups is larger than that in the inner layer 1b, and the acetylation degree of the surface layer 1a is 35% or less. ing. As the proportion of acetyl groups introduced into acetylcellulose, that is, the degree of acetylation decreases, the proportion of hydroxyl groups increases, and hydrophilicity (wetting properties) and swelling properties are improved. For this reason, the surface layer 1a has higher hydrophilicity and swelling property than the inner layer 1b. In other words, when the workpiece is polished in the polishing process, the polishing surface P side of the polishing sheet 1 of the polishing pad 20 mounted in the mounting process is hydrophilized and swollen.

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

  In this embodiment, the polishing pad 20 provided with the polishing sheet 1 made of polyurethane resin containing acetyl cellulose in the mounting step is mounted on the polishing surface plate of the polishing machine, and the acetyl cellulose can be deacetylated in the polishing step. While the colloidal silica slurry is supplied, the object to be polished is polished with the polishing pad 20 mounted in the mounting step. For this reason, at least a part of the acetylcellulose contained on the polishing surface P side (surface side) of the polishing sheet 1 is deacetylated, and the entire surface of the polishing surface P is more hydrophilic and swellable than the inner layer 1b. A surface layer 1a having a high thickness is formed. Moreover, even if the swelling property of the surface layer 1a is improved, the swelling property of the inner layer 1b is suppressed, so that the swelling property over the entire thickness of the polishing sheet 1 is suppressed. Furthermore, the polyurethane resin constituting the polishing sheet 1 has resistance to an alkaline slurry. Therefore, the surface of the polishing sheet 1 is hydrophilized and swollen over the entire surface without degrading the polyurethane resin constituting the polishing sheet 1, and the object to be polished is polished while suppressing the swelling property of the polishing sheet 1 as a whole. can do.

  In the present embodiment, as described above, in the polishing step, the surface layer 1a is formed over the entire polishing surface P side of the polishing sheet 1, and the surface layer 1a is more hydrophilic and swellable than the inner layer 1b. Becomes higher. In addition, even when the abrasion of the surface layer 1a progresses with the polishing process, since a slurry capable of deacetylating acetylcellulose is supplied, at least a part of the acetylcellulose is removed on the polishing surface P side of the polishing sheet 1. It is acetylated and the surface layer 1a is continuously formed over the entire polishing surface P. At this time, although an acetyl cellulose is deacetylated, an acid component is generated, but since an alkaline slurry having a pH of 10 or more is supplied, it does not affect the polishing process. For this reason, a familiar state with the slurry is maintained at the time of polishing processing, and the retention of the slurry is ensured, so that the polishing rate is improved by spreading the slurry sufficiently over the entire processing surface of the object to be polished, By gently polishing the processed surface of the object to be polished, generation of scratches can be suppressed and the flatness of the object to be polished can be improved.

  Furthermore, in this embodiment, alkaline colloidal silica slurry is used in the polishing step. A CMP method is used for polishing a semiconductor device that has been miniaturized and multilayered. In the CMP method, a processed surface of an object to be polished using an alkaline or acidic slurry in which abrasive particles are dispersed in an alkaline solution or an acid solution, a mechanical action by the abrasive particles in the slurry, and a chemical action by the alkaline solution or the acid solution are used. Polishing with the target action. In general, it is known that the alkaline solution has a higher dispersion stability of the abrasive particles in the solution than the acid solution. There is a possibility of scratching. In the polishing method of the present embodiment, acetylcellulose can be deacetylated and an alkaline slurry is used. Therefore, the polishing method can be suitably used for polishing a semiconductor device.

  In the present embodiment, in the mounting step, the polishing pad 20 has the double-sided tape 7, and the polishing pad 20 is bonded and fixed (attached) to the polishing surface plate of the polishing machine with the adhesive layer of the double-sided tape 7. However, the present invention is not limited to this. For example, the polishing pad 20 does not have the double-sided tape 7, and an adhesive is applied to the opposite side of the polishing surface P of the polishing sheet 1 so that the polishing pad 20 is mounted on the polishing surface plate of the polishing machine. Also good. Moreover, although the double-sided tape 7 was bonded to the polishing sheet 1 and the base material 7a of the double-sided tape 7 also serves as a support layer for supporting the polishing pad 20, the present invention is not limited to this. Alternatively, another support layer such as a PET film may be bonded between the polishing sheet 1 and the double-sided tape 7. Furthermore, in this embodiment, although the example which uses a single-side polisher as a polisher was shown, this invention is not limited to this.

  Further, in this embodiment, as an alkaline polishing liquid capable of deacylating a partially acylated polysaccharide component, a pH of 10 having colloidal silica having a particle diameter of 75 nm dispersed substantially uniformly in an alkaline solution containing potassium hydroxide. Although the example using colloidal silica slurry was shown, this invention is not limited to this. It is preferable to use an alkaline slurry having a pH of 10 or more because deacetylation of the acetylcellulose contained in the polishing sheet 1 is difficult to proceed with an alkaline slurry having a pH of less than 10. In consideration of the polishing action by the abrasive particles, the abrasive particles are preferably contained. Examples of the alkali used in the alkaline polishing liquid include alkali metal hydroxides such as sodium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, and ammonia. It is not particularly limited as long as the partially acylated polysaccharide component contained in the polishing sheet 1 can be deacylated. As the abrasive particles, alumina or the like can be mentioned, but any conventional particles may be used.

  Furthermore, in the present embodiment, an example is shown in which polishing is performed immediately after the polishing pad 20 is mounted on the polishing machine, but the present invention is not limited to this. For example, before performing the polishing process in the polishing process, an alkaline solution capable of deacetylating acetylcellulose is supplied to the polishing pad 20 mounted in the mounting process so that the surface is previously provided on the polishing surface P side of the polishing pad 20. The layer 1a may be formed. Conventionally, a break-in operation is performed to improve the familiarity between the polishing pad and the slurry before the polishing process. However, this break-in operation takes time and causes a reduction in polishing efficiency. In the present embodiment, the surface layer 1a formed on the polishing surface P side during the polishing process has good familiarity with the slurry (wetting with respect to the slurry), so that the polishing efficiency can be improved without performing a break-in operation. Can do.

  Furthermore, in this embodiment, as the polysaccharide (partially acetylated polysaccharide) component at least partly acetylated, acetylation is obtained by treating linter pulp having an α-cellulose content of 90 to 97% by the acetic acid method. Although an example using acetylcellulose having a degree of 54.3% and a degree of polymerization of 270 has been shown, the present invention is not limited to this. The acetyl cellulose is not particularly limited as long as it is obtained by treating wood pulp or linter pulp having an α-cellulose content of 90 to 97% by a conventional method such as a sulfuric acid catalyst method or a methylene chloride method. Diacetyl cellulose or triacetyl cellulose having an acetylation degree of 30 to 62.5% and a polymerization degree of 200 to 4000 may be used. Considering the solubility in an organic solvent (DMF, DMAc, etc.) used in the preparation process during production, it is preferable to use acetylcellulose having an acetylation degree of 45 to 62% and a polymerization degree of 200 to 350. In addition to the partially acetylated polysaccharide component, a partially acylated polysaccharide component may be used. For example, the partially acylated polysaccharide component may be selected from cellulose, chitosan or a reaction product of dextrin and a carboxylic acid derivative, and specific examples include butyryl chitosan. There is no particular limitation as long as it is deacylated with slurry and can be hydrophilized and swollen over the entire surface of the polishing sheet 1.

  Furthermore, in this embodiment, although the example in which acetylcellulose is contained in the range of 5 to 40% by weight in the polishing sheet 1 excluding foaming is shown, the present invention is not limited to this. When the content of acetyl cellulose is less than 5% by weight, the amount of acetyl cellulose for improving hydrophilicity is reduced by deacetylation, and it is difficult to improve hydrophilicity on the surface side of the polishing sheet 1. . On the other hand, when the content of acetyl cellulose is more than 40% by weight, physical properties such as hardness of the entire polishing sheet 1 change, and it becomes difficult to improve the flatness of the object to be polished. Therefore, it is preferable that a partially acylated polysaccharide component such as acetylcellulose is contained in the polishing sheet 1 excluding foaming in the range of 5 to 40% by weight.

  Further, in the present embodiment, the example in which the polishing sheet 1 has a polyurethane resin as a main component is shown, but the present invention is not limited to this. Resins that are resistant to alkaline solutions and are typically used for polishing pads can be used. In consideration of including a partially acylated polysaccharide component, it is preferable to use a polyurethane resin. In this case, the polyurethane resin and the partially acylated polysaccharide component can be dissolved in the same organic solvent.

  Further, in the present embodiment, the wet film formation in which the polyurethane body is coagulated and regenerated by immersing in an aqueous coagulating liquid in the coagulation regenerating process at the time of manufacturing the polishing pad 20 is illustrated, but the present invention is limited to this. Instead, the polyurethane body may be regenerated by another method. For example, dry film formation in which an organic solvent is removed from a mixed solution in a hot air atmosphere to regenerate a polyurethane body may be used. Moreover, in this embodiment, although the example which uses DMF as an organic solvent at the time of manufacture of the polishing sheet 1 was shown, this invention is not limited to this, The water miscible organic solvent which can melt | dissolve a polyurethane resin is shown. Can be used. For example, an organic solvent such as DMAc may be used in addition to DMF, and the polishing sheet 1 may be formed by mixing DMF with another organic solvent. Furthermore, in this embodiment, although the example which dissolves acetylcellulose in the same organic solvent as a polyurethane resin was shown, it cannot be overemphasized that this invention is not restrict | limited to this.

  Furthermore, although not particularly mentioned in the present embodiment, the polishing surface P of the polishing pad 20 may be subjected to grooving or embossing for promoting the discharge of polishing debris or the movement of the polishing liquid. The shape of the groove may be any of a radial shape, a spiral shape, and the like, 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 as long as the polishing waste can be discharged and the polishing liquid can be moved. 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.

  Hereinafter, examples in which the polishing pad 20 is manufactured and used for polishing according to the present embodiment will be described. A polishing process using a polishing pad of a comparative example manufactured for comparison is also described.

Example 1
In Example 1, polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin. A polyurethane resin solution was prepared by mixing 40 parts of a DMF dispersion containing 30% by weight of pigment carbon black and 2 parts of a hydrophobic activator with 100 parts of this DMF solution of polyurethane resin. As the partially acylated polysaccharide component, acetylcellulose having an acetylation degree of 54.3% and a polymerization degree of 270 was used to prepare an acetylcellulose solution. A mixed liquid was prepared by mixing the polyurethane resin solution with the acetylcellulose solution so that 10% by weight of acetylcellulose was contained in the polishing sheet 1 excluding foaming. After the mixed solution was applied to a PET film-forming substrate, the polyurethane body formed by coagulation regeneration was washed and dried to form the polishing sheet 1 to manufacture the polishing pad 20.

(Comparative Example 1)
In Comparative Example 1, a polishing pad was produced in the same manner as in Example 1 except that it did not contain acetylcellulose. That is, after applying a polyurethane resin solution containing no acetylcellulose (no acetylcellulose solution mixed with polyurethane resin solution) to a PET film-forming substrate, the polyurethane body formed by coagulation regeneration is washed and dried. Thus, a polishing sheet was formed to manufacture a polishing pad. In Comparative Example 1, since acetylcellulose is not contained, the surface layer 1a and the inner layer 1b like the polishing pad 20 are not formed at the time of polishing, but polishing is performed using an alkaline slurry as in Example 1. Since it is processed, the surface side portion will be described below as a surface layer, and the other portion as an internal layer.

(Polishing performance)
Next, the polishing pads of Example 1 and Comparative Example 1 were mounted on a polishing surface plate of a polishing machine, and an alkaline slurry capable of deacetylating acetylcellulose was supplied for 20 minutes under the following polishing conditions for a hard disk. The aluminum substrate was polished 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 aluminum substrate before and after polishing, the polishing area of the aluminum substrate, and the specific gravity. Moreover, the waviness of the processed surface of the aluminum substrate after polishing and the presence or absence of scratches were measured. Waviness is one of the measurement items for evaluating the surface accuracy (flatness) of disk substrates, silicon wafers, etc., and the amount of surface image waviness per unit area observed with an optical non-contact surface roughness meter ( Wa) is expressed in units of angstroms (Å). Evaluation was performed using Optiflat as a test evaluation machine. The presence / absence of scratch was determined visually by the presence / absence of scratch on the aluminum substrate by polishing. Table 1 shows the measurement results of the polishing rate, the waviness of the processed surface, and the presence or absence of scratches.
(Polishing conditions)
Polishing machine used: Speedfam, 9B-5P polishing machine Polishing speed (rotation speed): 30 rpm
Processing pressure: 100 g / cm ²
Slurry: Colloidal silica slurry (pH: 10)
Slurry supply amount: 100cc / min
Workpiece: Aluminum substrate for hard disk (outer diameter 95mmφ, inner diameter 25mm, thickness 1.27mm)

  As shown in Table 1, the polishing pad of Comparative Example 1 showed a polishing rate of 0.188 μm / min, and scratches were generated on the polished processed surface. In contrast, with the polishing pad 20 of Example 1, the polishing rate was 0.198 μm / min, and no scratch was generated on the polished surface. Since the polishing pad 20 of Example 1 contains acetylcellulose and was polished while supplying a slurry capable of deacetylating acetylcellulose, it is considered that the surface layer 1a was formed on the polishing surface P side. For this reason, since the hydrophilicity and swelling property on the surface side are higher than those of the polishing pad of Comparative Example 1, the familiarity between the polishing surface P and the slurry is improved during polishing, and the slurry is spread over the entire processed surface of the object to be polished. It is considered that the polishing rate is improved by spreading sufficiently, and the generation of scratches is suppressed by polishing the processed surface softly. Further, in the polishing pad of Comparative Example 1, the waviness was 10 mm. On the other hand, in the polishing pad 20 of Example 1, the waviness was 6%. In the polishing pad 20 of Example 1, since the familiarity between the polishing surface P and the slurry is improved during polishing and the retention of the slurry is ensured, it is considered that the flatness of the object to be polished has been improved.

(Evaluation of the physical properties)
Next, after removing the polishing pads of Example 1 and Comparative Example 1 after measuring the polishing performance described above from the polishing platen of the polishing machine, washing the slurry with distilled water and drying it once, water on the surface The contact angle was measured. Moreover, the swelling degree of the polishing sheet of Example 1 and Comparative Example 1 and the surface layer was measured. The contact angle of water was measured by a droplet method using an automatic contact angle meter (DropMaster 500 manufactured by Kyowa Interface Science Co., Ltd.). That is, distilled water is put into a syringe of an automatic contact angle meter, and under the conditions of a temperature of 20 ° C. and a humidity of 60%, a drop of water is dropped from the injection needle onto the surface of the polishing sheet, and contact is made 10 seconds after dropping. I read the corner. The degree of swelling was obtained by cutting a polishing sheet into a 4 cm × 4 cm square to form a sample, placing the sample under conditions of a temperature of 20 ° C. and a humidity of 60% for 12 hours, and then measuring the original weight A with a precision balance. Next, after immersing this sample in distilled water and immersing in water for 24 hours, the sample was taken out, only the moisture on the surface was wiped off, and the weight B of the sample after immersion in water was measured with a precision balance. Using these weight values, the degree of swelling was calculated by the following equation. That is, the degree of swelling (%) = {(BA) / A} × 100. Similarly, the inner layer obtained by grinding and removing the surface layer of the polishing sheet by 100 ± 10 μm was cut into a square of 4 cm × 4 cm to form a sample, and after placing it under conditions of a temperature of 20 ° C. and a humidity of 60% for 12 hours, The weight a was measured with a precision balance. Next, after immersing this sample in distilled water and immersing in water for 24 hours, the sample was taken out, only the moisture on the surface was wiped off, and the weight b of the sample after immersion in water was measured with a precision balance. Using these weight values, the degree of swelling of the surface layer of the polishing sheet was calculated by the following formula. Swelling degree (%) = [{(B−b) − (A−a)} / (A−a)] × 100. The measurement results of the water contact angles of Example 1 and Comparative Example 1 are shown in Table 2 below. Moreover, the measurement result of the swelling degree of the polishing sheet of Example 1 and Comparative Example 1 and the surface layer is shown together in Table 2 below.

  As shown in Table 2, the polishing pad of Comparative Example 1 showed a water contact angle of 61.4 ° and a surface layer swelling degree of 1.5%. On the other hand, in the polishing pad 20 of Example 1, the contact angle of water was 10.3 °, and the swelling degree of the surface layer 1a was 13.0%. In the polishing pad 20 of Example 1, compared with the polishing pad of the comparative example 1, it turned out that the contact angle of water is small and the swelling degree of a surface layer is large. In Example 1, since the surface layer 1a was formed by deacetylating at least part of the acetylcellulose contained on the polishing surface P side of the polishing pad 20 by the alkaline slurry, the hydrophilicity and the swelling property of the surface were improved. It was confirmed. On the other hand, in the entire polishing sheet of Comparative Example 1, the degree of swelling was 1.5%. On the other hand, in the entire polishing sheet 1 of Example 1, the degree of swelling was 3.5%. Since the surface layer 1a is formed on the polishing sheet 1 of Example 1, the swelling property is higher than that of the polishing sheet of Comparative Example 1, but it is confirmed that it is suppressed to 5% or less. It was.

  Since the present invention provides a polishing method capable of improving the flatness of an object to be polished, it contributes to the manufacture and sale of polishing pads, and thus has industrial applicability.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is sectional drawing which shows typically the polishing pad of embodiment at the time of grinding | polishing process. It is process drawing which shows the principal part of the grinding | polishing processing method of embodiment.

Explanation of symbols

1 Polishing sheet (polishing layer)
1a Surface layer (part of polishing layer)
1b Inner layer (part of polishing layer)
2 Foam (cell)
20 Polishing pad P Polished surface

Claims (7)

A polysaccharide component having a polishing layer having a foam structure having a polishing surface for polishing an object to be polished and having cells formed therein, the polishing layer excluding the cells being at least partially acylated. A mounting step of mounting a polishing pad, which is soluble in an organic solvent capable of dissolving the resin constituting the polishing layer and contains a partially acylated polysaccharide component hardly soluble or insoluble in water, on a surface plate of a polishing machine; ,
A polishing step of polishing an object to be polished with the polishing pad mounted in the mounting step while supplying an alkaline polishing liquid capable of deacylating the partially acylated polysaccharide component;
Including
In the polishing step, the polishing liquid infiltrates the polishing surface side of the polishing pad mounted in the mounting step, so that at least the polishing surface side of the partially acylated polysaccharide component contained in the polishing layer. A polishing method for an object to be polished, wherein a part of the partially acylated polysaccharide component is deacylated.   The polishing method according to claim 1, wherein the polishing liquid supplied in the polishing step has a pH of 10 or more.   The polishing method according to claim 2, wherein the polishing liquid supplied in the polishing step contains abrasive particles.   The polishing method according to claim 1, wherein the polishing layer mounted in the mounting step has the polishing layer containing a polyurethane resin as a main component. The polishing pad mounted in the mounting step includes the partially acylated polysaccharide component in a proportion of 5 wt% to 40 wt% in a polishing layer excluding the cell. Polishing method. The partially acylated polysaccharide component contained in the polishing pad attached in the attaching step is at least one selected from a reaction product of cellulose, chitosan or dextrin and a carboxylic acid derivative. 2. The polishing method according to 1. The polishing method according to claim 6, wherein the partially acylated polysaccharide component is acetylcellulose.

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