JP2011073112A - Polishing pad and method of manufacturing polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad capable of improving flatness accuracy in a polishing object, by securing cushion performance. <P>SOLUTION: This polishing pad 10 has a urethane sheet 2 having a polishing surface Sp and cross-linking and hardening the whole after forming a film by a wet solidification method. In the urethan sheet 2, a skin layer when forming the film is removed, and a large number of longitudinally long cells 3 are formed in the thickness direction inside. A large cell 3a having the size in the longitudinally long direction of 50% or more to a thickness (t) of the urethane sheet 2, has a maximum hole diameter A in a position separated from the polishing surface Sp by the length of exceeding 1/2 of the size in the longitudinally long direction. In the urethane sheet 2, an average value per unit area of the ratio A/B of the maximum hole diameter A to an average hole diameter B of an opening hole formed of the cells 3 in a cross section parallel to the polishing surface Sp on the inside by 5% of the thickness (t) from the polishing surface Sp, is adjusted in a range of 5-20. Hardness of the urethane sheet 2 is enhanced, and the large cell 3a is deformed by polishing pressure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polishing pad and a method for manufacturing the polishing pad, and in particular, a polishing provided with a resin sheet having a polishing surface for polishing an object to be polished by forming a number of vertically elongated foams in the thickness direction by a wet coagulation method. The present invention relates to a pad and a method for manufacturing the polishing pad.

  Conventionally, various materials such as semiconductor devices have been polished using a polishing pad to ensure flatness. In the manufacture of a semiconductor device, a copper (Cu) wiring layer and an insulating layer are usually formed sequentially to be multilayered, and the surface (processed surface) after forming each layer is polished. In recent years, as the degree of integration of semiconductor circuits has increased rapidly, miniaturization and multilayer wiring have been promoted for the purpose of higher density, and a technique for further flattening the processed surface has become important.

  Generally, in the manufacture of semiconductor devices, a chemical mechanical polishing (hereinafter abbreviated as CMP) method is used. In the CMP method, a slurry (polishing liquid) in which abrasive grains (polishing particles) are dispersed in an alkali solution or an acid solution is usually supplied. That is, the object to be polished (the processed surface thereof) is flattened by a mechanical polishing action by the abrasive grains in the slurry and a chemical polishing action by the alkali solution or acid solution.

  In polishing processing of a semiconductor device by the CMP method, a polishing pad is generally used that is formed by a dry molding method and includes a resin sheet in which an opening is formed on a polishing surface for polishing an object to be polished. At the time of polishing, the processed surface is flattened by being supplied so that the abrasive grains are dispersed in the processed surface while being held in the openings formed in the polished surface. In other words, it is indispensable for the polishing pad for semiconductor devices to have an opening formed in the polishing surface. Such an opening can be formed by forming a resin foam by a dry molding method and grinding the surface of the obtained foam or slicing the foam. As a technique for forming a foam by a dry molding method, for example, a technique in which hollow fine particles are added to a resin solution at the time of molding is disclosed (Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4). , See Patent Document 5). In addition, a technique for generating gas at the time of molding by adding water to the resin solution (for example, see Patent Document 6), a technique for dispersing an inert gas in the resin solution and molding (for example, see Patent Document 7). Also disclosed is a technique for adding water-soluble fine particles to a resin solution (see, for example, Patent Document 8).

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, since the techniques of Patent Documents 1 to 8 are all formed by a dry molding method, the obtained resin sheet is hard and mainly an independent foam type. For this reason, there exists a problem that the opening formed in the grinding | polishing surface becomes clogged with an abrasive grain, grinding | polishing waste, etc., and becomes easy to block | close. When the opening is closed, the abrasive grains and the like are likely to aggregate, and as a result, there is a risk of causing scratches (scratches) on the processed surface of the workpiece. In the polishing process of a semiconductor device, if a scratch is generated, there is a risk of cutting the wiring, which is a fatal defect. If the polishing process is interrupted and the surface is dressed, the holes are regenerated and the polishing process can be continued. However, since the dressing is essential, the polishing efficiency is lowered. Moreover, since a hard resin sheet has insufficient cushioning properties, it needs to be bonded to another sheet having cushioning properties. Compared with a resin sheet obtained by a dry molding method, a resin sheet obtained by a wet coagulation method is generally easy to obtain cushioning properties by forming a vertically long foam in the thickness direction. On the other hand, by having flexibility, the flatness tends to be lowered at the outer edge portion of the object to be polished, and dishing and erosion are easily caused. As described above, with the advancement of flatness required for the processing surface of semiconductor devices, the demand for polishing performance such as polishing accuracy and polishing efficiency by the CMP method is also increasing, and along with this, the opening diameter of the polishing pad is also finer. There is a growing demand for equalization and uniformity. Furthermore, a polishing pad that can suppress fatal defects such as scratches is desired in order to improve yield and achieve efficient production.

  An object of the present invention is to provide a polishing pad capable of ensuring cushioning properties and improving the flatness accuracy of an object to be polished, and a method for manufacturing the polishing pad.

  In order to solve the above problems, a first aspect of the present invention includes a resin sheet having a polishing surface for polishing a workpiece to be polished, in which a number of vertically long foams are formed in the thickness direction by a wet coagulation method. In the polishing pad, the entire resin sheet is crosslinked and cured, and the length in the thickness direction of the foam observed in the cross section in the thickness direction is 50% or more with respect to the entire thickness. Has a maximum pore diameter A at a position away from the polishing surface by a length exceeding 1/2 of the length of the large foam, and is 5% inside the entire thickness from the polishing surface. The average value per unit area of the ratio A / B of the maximum pore diameter A to the average pore diameter B of the foamed pores including the large foam formed is in the range of 5 to 20.

  In the first aspect, the hardness of the entire resin sheet formed by the wet coagulation method is increased by crosslinking and hardening, and the maximum pore diameter of large foam having a length in the thickness direction of 50% or more with respect to the entire thickness. Since the average value per unit area of the ratio A / B to the average pore diameter B of the foamed pores including large foams formed within 5% of the total thickness from the polished surface is generally 5 to 20, Since the cushioning property lost by the cross-linking and curing is ensured, excessive polishing at the outer edge of the object to be polished can be suppressed and the flatness accuracy can be improved.

  In the first aspect, the Shore D hardness of the resin sheet can be in the range of 25 degrees to 65 degrees. In the resin sheet, the average pore diameter B may be in the range of 5 μm to 40 μm. At this time, in the resin sheet, the maximum pore diameter A of large foam may be in the range of 50 μm to 300 μm. The resin sheet can be made of polyurethane resin. At this time, the resin sheet may have a continuous foam structure in which micropores are formed between foams including large foams, and foams including large foams and the micropores communicate with each other.

  According to a second aspect of the present invention, there is provided a polishing pad manufacturing method according to the first aspect, wherein a resin is dissolved in an organic solvent, and a crosslinking agent in which a plurality of reactive functional groups are protected with a protective group is contained. A solution preparation step for preparing a resin solution; a coagulation regeneration step for regenerating the resin by spreading the resin solution prepared in the solution preparation step into a sheet and then coagulating it in a coagulation liquid containing water as a main component; A crosslinking curing step of heating the resin regenerated in the coagulation regeneration step to dissociate the protecting group from the crosslinking agent and crosslinking and cure the entire resin with the crosslinking agent from which the protecting group has been dissociated. Including.

  In the second aspect, the crosslinking agent contained in the resin solution in the solution preparation step can be a blocked isocyanate compound protected with a blocking agent. At this time, the organic solvent used in the solution preparation step is preferably N, N-dimethylacetamide or N-methyl-2-pyrrolidone.

  According to the present invention, the hardness of the entire resin sheet formed by wet coagulation is increased by crosslinking and hardening, and the maximum pore diameter of large foam having a length in the thickness direction of 50% or more with respect to the entire thickness. Since the average value per unit area of the ratio A / B to the average pore diameter B of the pores of the foam including the large foam formed inside 5% of the total thickness from the polished surface is 5-30, Since the cushioning property lost by the crosslinking and curing is ensured, it is possible to obtain the effect that the excessive polishing process at the outer edge portion of the object to be polished can be suppressed and the flatness accuracy can be improved.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is explanatory drawing which shows typically the magnitude | size of the foam formed in the polishing pad of embodiment. It is process drawing which shows the outline of the manufacturing process of the polishing pad of embodiment.

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

(Constitution)
The polishing pad 10 of this embodiment is provided with the urethane sheet 2 as a resin sheet made of a polyurethane resin, as shown in FIG. The entire urethane sheet 2 is formed by cross-linking and curing after film formation by the wet coagulation method, and has a polishing surface Sp for polishing an object to be polished on one surface side.

  In the urethane sheet 2, the skin layer formed at the time of film formation is removed by a grinding process. Inside the urethane sheet 2, a large number of cells 3 are formed in a substantially uniformly dispersed state. The cell 3 is formed in a vertically long and rounded conical shape (longitudinal triangular shape in cross section) in the thickness direction of the urethane sheet 2, and the surface of the polishing surface Sp side is opposite to the polishing surface Sp (hereinafter referred to as the back surface Sr). It is smaller than the side. That is, the diameter of the cell 3 is reduced on the polishing surface Sp side. The polyurethane resin between the cells 3 is formed in the shape of a partition that defines the cells 3, and micropores (not shown) smaller than the cells 3 are formed inside. That is, the polyurethane resin constituting the urethane sheet 2 is microporous. The urethane sheet 2 has a continuous foaming structure in which the cells 3 and the micropores not shown are communicated in a mesh pattern, and foaming is formed continuously. Openings of the cells 3 are formed on the polished surface Sp formed by removing the skin layer at the time of film formation.

  The size of the cell 3 in the longitudinal direction varies within the range of the thickness of the urethane sheet 2. In other words, the urethane sheet 2 has a large cell 3a in which the size in the longitudinal direction is 50% or more of the thickness t with respect to the thickness t of the urethane sheet 2, that is, 0.5t or more, and the size in the longitudinal direction. Is formed with a small cell 3b of less than 50% of the thickness t, that is, less than 0.5t. As shown in FIG. 2, the large cell 3a formed in the urethane sheet 2 has a maximum hole diameter A at a position away from the polishing surface Sp by a length exceeding 1/2 of the size in the longitudinal direction. . Considering the possibility of some distortion being formed in the vertically long large cells 3a during film formation by the wet coagulation method, exceptional large cells 3a may also be formed depending on how the cross section in the thickness direction is taken. Specifically, almost all large cells 3a have the maximum hole diameter A at the same position. In this example, the maximum pore diameter A is adjusted to a range of 50 to 300 μm. In this urethane sheet 2, the average hole diameter B of the holes formed by the cells 3 in the cross section parallel to the polishing surface Sp on the inner side by 5% of the thickness t from the polishing surface Sp, that is, 0.05t inside, In the range of 5 to 40 μm. In the large cell 3a, the average value per unit area of the ratio A / B of the maximum pore diameter A to the average pore diameter B is adjusted to a range of 5-20. That is, in the large cell 3a, the maximum pore diameter A is 5 to 20 times as large as the average with respect to the average pore diameter B on the polishing surface P side. Moreover, since the urethane sheet 2 is crosslinked and cured after film formation by the wet coagulation method, the Shore D hardness is in the range of 25 to 65 degrees.

  In addition, the polishing pad 10 has a double-sided tape 7 attached to the polishing machine 10 on the back surface Sr side of the urethane sheet 2. The double-sided tape 7 has, for example, a base material 7a of a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET), and an adhesive such as an acrylic adhesive on both surfaces of the base material 7a. Each layer (not shown) is formed. The double-sided tape 7 is bonded to the urethane sheet 2 with an adhesive layer on one side of the base material 7a, and the adhesive layer on the other side (opposite to the urethane sheet 2) is covered with a release paper 7b. The base material 7 a of the double-sided tape 7 also serves as the base material of the polishing pad 10.

(Manufacturing)
The polishing pad 10 is produced by producing a urethane sheet 2 by crosslinking and curing the entire sheet formed of polyurethane resin by a wet coagulation method, and bonding the obtained urethane sheet 2 and double-sided tape 7 together. . That is, as shown in FIG. 2, a preparation step (solution preparation step) for preparing a polyurethane resin solution, a coating step (part of a coagulation regeneration step) for applying a polyurethane resin solution to a film forming substrate in a sheet form, a polyurethane resin A coagulation regeneration process in which the solution is coagulated in a coagulation liquid to regenerate the polyurethane resin (part of the coagulation regeneration step), and after the regenerated sheet-like polyurethane resin is washed, it is heated and crosslinked to cure the whole. (Crosslinking and curing step) Polishing pad 10 after undergoing a buffing process to crosslink and cure the sheet-like polyurethane resin after crosslinking and curing, and a laminating process for bonding the obtained urethane sheet 2 and double-sided tape 7 together Is manufactured. Hereinafter, it demonstrates in order of a process.

(Preparation process)
In the preparation step, the polyurethane resin is dissolved by mixing the polyurethane resin, a water-miscible organic solvent capable of dissolving the polyurethane resin, an additive, and a crosslinking agent. As the organic solvent, N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone or the like can be used. Is used. Although the following can be used as the polyurethane resin, in this example, diphenylmethane-4,4′-diisocyanate (MDI) -polyester polyol compound-ethylenediamine-based polyurethane resin is used, and the polyurethane resin is 35 wt. % To dissolve in DMAc. As additives, to control the size and quantity (number) of cells 3 (large cells 3a and small cells 3b), pigments such as carbon black, hydrophilic active agents that promote foaming, and solidification regeneration of polyurethane resin are stabilized. Hydrophobic activator or the like can be used.

  As the polyurethane resin, a polyisocyanate compound and a polyol compound, or a product obtained by reacting a polyisocyanate compound, a polyol compound, and a polyamine compound as main components can be used. In order to obtain a urethane sheet with high hardness, it is preferable to use a polyurethane resin (polyurethane polyurea resin) containing a polyamine compound. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, tolylene diisocyanate (TDI), MDI, xylylene diisocyanate, naphthalene-1,5-diisocyanate, p-phenylene diisocyanate, dibenzyl diisocyanate, diphenyl ether diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate Aromatic diisocyanate monomers such as triphenylmethane triisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane-4,4′-diisocyanate, hydrogenated xylylene diisocyanate, cyclohexyl-1,4 -Alicyclic diisocyanate monomers such as diisocyanate and isophorone diisocyanate, 1,4-tetramethylene diisocyanate, , It may be mentioned 6-aliphatic diisocyanates monomers such as hexamethylene diisocyanate and the like. Two or more of these may be used, and various modified polyisocyanates such as polyisocyanurate type polyisocyanates or biuret type polyisocyanates having three or more functionalities based on these diisocyanate monomers may be used. it can.

  Examples of the polyol compound to be reacted with such a polyisocyanate compound include a low molecular weight polyol compound and a high molecular weight polyol compound. As a low molecular weight polyol compound, what is necessary is just a diol compound, a triol compound, etc., For example, ethylene glycol, butylene glycol, 1, 4- butanediol etc. can be mentioned. Examples of the high molecular weight polyol compound include polyether polyol compounds such as polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetramethylene glycol (PTMG), reaction products of ethylene glycol and adipic acid, and butylene glycol and adipic acid. Examples thereof include polyester polyol compounds such as reactants, polycarbonate polyol compounds, and polycaprolactone polyol compounds. Moreover, you may use 2 or more types of these.

  As the polyamine compound to be reacted with the polyisocyanate compound, an aliphatic or aromatic polyamine compound can be used. For example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4 ′. Examples include -diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), polyamine compounds having the same structure as MOCA, and the like. Further, the polyamine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, and di-2-hydroxy. Examples include ethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. Moreover, you may use 2 or more types of these.

  The crosslinking agent to be blended in the polyurethane resin solution is stable to the organic solvent used for dissolving the polyurethane resin and water used for the regeneration of the polyurethane resin in consideration of the production process by the wet coagulation method (not exhibiting reactivity). It is preferably a compound that exhibits reactivity upon heating. In this example, a crosslinking agent in which a plurality of reactive functional groups are protected with a protecting group is used. As such a crosslinking agent, a blocked isocyanate compound obtained by reacting one or more polyvalent isocyanate compounds with one or more blocking agents which are compounds having active hydrogen can be used. In this blocked isonate compound, the blocking agent is dissociated by heating to regenerate the isocyanate group, so that it reacts with the polyurethane resin having active hydrogen at the terminal to form a cross-linked bond.

  As the polyvalent isocyanate compound used for the blocked isocyanate compound, any generally known isocyanates can be used. For example, TDI, MDI, xylylene diisocyanate, naphthalene-1,5-diisocyanate, p-phenylene diisocyanate, Aromatic diisocyanate monomers such as dibenzyl diisocyanate, diphenyl ether diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, aromatic triisocyanate monomers such as triphenylmethane triisocyanate, hydrogenated tolylene diisocyanate, Hydrogenated diphenylmethane-4,4′-diisocyanate, hydrogenated xylylene diisocyanate, cyclohexyl-1,4-diisocyanate Cycloaliphatic diisocyanates monomers such as isophorone diisocyanate, 1,4-tetramethylene diisocyanate, can be mentioned 1,6-aliphatic diisocyanates monomers such as hexamethylene diisocyanate and the like. Two or more of these may be used, and various modified polyisocyanates such as polyisocyanurate type polyisocyanates or biuret type polyisocyanates having three or more functionalities based on these diisocyanate monomers may be used. it can. Furthermore, a urethane prepolymer obtained by reacting the terminal of these isocyanates with a polyol compound can also be used as the polyvalent isocyanate compound. It is preferable to use a urethane prepolymer for the polyvalent isocyanate compound because it has an appropriate flexibility even after the curing reaction and hardly causes cracking. Examples of the polyol compound used here include a low molecular weight polyol compound and a high molecular weight polyol compound. As a low molecular weight polyol compound, what is necessary is just a diol compound, a triol compound, etc., For example, ethylene glycol, butylene glycol, 1, 4- butanediol etc. can be mentioned. Examples of the high molecular weight polyol compound include polyether polyol compounds such as PEG, PPG, and PTMG, polyester polyol compounds such as a reaction product of ethylene glycol and adipic acid, a reaction product of butylene glycol and adipic acid, a polycarbonate polyol compound, and polycaprolactone. A polyol compound etc. can be mentioned. Moreover, you may use 2 or more types of these.

  On the other hand, as the blocking agent for blocking the isocyanate group of the polyvalent isocyanate compound, any compound having a generally known active hydrogen can be used. For example, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n -Alcohols such as butanol, isobutanol, t-butanol and 2-ethylhexanol, ketoximes such as methyl ethyl ketoxime, phenol, ε-caprolactam, ethyl acetoacetate, diethyl malonate and the like. These may be used alone or in combination of two or more. Considering the dissociation property of the blocking agent, it is preferable to use methyl ethyl ketoxime or ε-caprolactam as the blocking agent. In this example, two unreacted isocyanate groups at the end of a urethane prepolymer obtained by reacting 2,4-tolylene diisocyanate and PTMG having a number average molecular weight of 650 in a ratio of 2: 1 as a crosslinking agent are respectively protected with methyl ethyl ketoxime. A blocked isocyanate compound is used. This blocked isocyanate compound is mixed so as to have a ratio of 3 to 50% by weight with respect to the polyurethane resin dissolved in DMAc. The resulting solution is degassed under reduced pressure to obtain a polyurethane resin solution.

(Coating process)
In the application step, the polyurethane resin solution obtained in the preparation step is applied substantially uniformly in a sheet form to the belt-shaped film forming substrate at a normal temperature by an application device such as a knife coater. At this time, the coating thickness (coating amount) of the polyurethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater or the like and the film forming substrate. Although a cloth, a nonwoven fabric, etc. can also be used as a film-forming base material, in this example, a PET film is used.

(Coagulation regeneration process)
In the coagulation regeneration step, the polyurethane resin solution applied to the film forming substrate is continuously guided to a coagulation liquid (water-based coagulation liquid) whose main component is water which is a poor solvent for the polyurethane resin. In order to adjust the coagulation regeneration speed of the polyurethane resin, an organic solvent such as an organic solvent used in the polyurethane resin solution or other polar solvent may be added to the coagulation liquid. In this example, an aqueous solution containing 5% by weight of DMAc is used. The polyurethane resin solution coagulates in the coagulating liquid, and the polyurethane resin having a continuous foam structure is regenerated. In the coagulation liquid, first, a film is formed at the interface between the polyurethane resin solution and the coagulation liquid, and fine micropores constituting the skin layer are formed in the polyurethane resin immediately adjacent to the film. Thereafter, regeneration of the polyurethane resin proceeds by a cooperative phenomenon between the diffusion of the organic solvent in the polyurethane resin solution into the coagulating liquid and the penetration of water into the urethane resin, that is, solvent substitution. In the recycled polyurethane resin, the cohesive force increases, so that the polyurethane resin solution rapidly solidifies on the surface of the film, and the amount of polyurethane resin inside decreases. And the diffusion of the organic solvent in the polyurethane resin solution into the coagulating liquid is suppressed by the dense pore film formed on the surface, and the cell 3 is formed inside. 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 polyurethane resin solution, and cells 3 having a larger film formation substrate side than the surface side are formed. . In addition, when the organic solvent in the polyurethane resin solution is desolvated from the polyurethane resin solution and the organic solvent and the coagulating liquid (water) are replaced, a part of the micropores formed in the immediate vicinity of the skin layer surface is expanded. Diameter is formed to form a channel, and micropores (not shown) are formed in the polyurethane resin. Along with the solvent replacement, the fine pores of the skin layer, the cells 3 and the fine pores not shown are communicated in a network. At this time, the blocked isocyanate compound as a crosslinking agent is mixed in the regenerated polyurethane resin without being reacted.

(Crosslinking curing process)
As shown in FIG. 2, in the cross-linking curing process, the solidified and regenerated sheet-like polyurethane resin (hereinafter referred to as film-forming resin) is washed in a cleaning solution such as water to remove the organic solvent remaining in the film-forming resin. To do. The film-forming resin after washing is subjected to a heat treatment for 5 to 30 minutes in a temperature range of 140 to 180 ° C. When heat-treating, for example, it is continuously conveyed in a heated atmosphere. By heating, the blocking agent is dissociated from the blocked isocyanate compound contained in the film-forming resin, and the reactive isocyanate group is regenerated. The isocyanate group reacts with active hydrogen at the terminal of the polyurethane resin, active hydrogen constituting a urethane bond or a urea bond, thereby forming a crosslinked bond in the polyurethane resin. In addition, the film forming resin dries with this heating. The obtained sheet-shaped film-forming resin after crosslinking and curing is cut into an appropriate length and placed flat.

(Grinding process)
In the grinding treatment step, a grinding treatment is performed to make the thickness uniform by buffing the skin layer formed on the surface of the cross-linked and cured sheet-like polyurethane 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, some cells 3 are opened in the polishing surface Sp, the thickness of the polyurethane resin is made uniform, and the urethane sheet 2 is obtained.

(Lamination process)
In the laminating step, the urethane sheet 2 after the grinding treatment and the double-sided tape 7 are bonded together. At this time, the back surface Sr of the urethane sheet 2 and the adhesive layer on one side of the double-sided tape 7 are bonded together. Then, after cutting into a desired shape or size such as a circle or a square, an inspection is performed to confirm that there is no adhesion of scratches, dirt, foreign matter, etc., and the polishing pad 10 is completed.

  When polishing an object to be polished, for example, a semiconductor device, the polishing pad 10 is mounted on a polishing surface plate of a polishing machine. When the polishing pad 10 is mounted on the polishing surface plate, the release paper 7b is removed and the exposed adhesive layer is attached. An object to be polished is held on a holding platen arranged opposite to the polishing platen. The object to be polished is pressed between the polishing surface plate and the holding surface plate, and the processing surface of the object to be polished is polished by rotating the polishing surface plate or holding surface plate while supplying the slurry.

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

  In this embodiment, the entire film-forming resin in which the urethane sheet 2 is formed by a wet coagulation method is formed by crosslinking and curing. For this reason, while the film-forming resin originally obtained by the wet coagulation method is soft, the hardness of the urethane sheet 2 can be increased, and the Shore D hardness can be in the range of 25 to 65 degrees. This hardness range is close to a hard urethane foam formed by a so-called dry molding method in which an isocyanate compound having a terminal isocyanate group is reacted with a chain extender, and is markedly compared with a soft resin sheet by a conventional wet coagulation method. It is a large range. Accordingly, it has been found that the outer edge portion of the object to be polished is excessively polished in the conventional soft sheet to reduce the flatness, whereas the polishing pad 10 using the urethane sheet 2 is excessively polished at the outer edge portion. Processing can be suppressed.

  Moreover, in the urethane sheet 2 of this embodiment, the cell 3 peculiar to the wet coagulation method is formed. In the large cell 3a of the cells 3, the average value per unit area of the ratio A / B of the maximum pore diameter A to the average pore diameter B is adjusted to a range of 5-20. For this reason, the cushioning properties are generally lost by crosslinking and curing, but even if the urethane sheet 2 is crosslinked and cured, the large cells 3 are deformed by the polishing pressure at the time of polishing to ensure the cushioning properties. can do. Thereby, since the hardness is increased and the cushioning property is ensured, the flatness accuracy of the object to be polished can be improved during the polishing process. If the ratio A / B is less than 5, sufficient cushioning properties cannot be obtained, and the polishing scraps are not sufficiently accommodated, resulting in scratches. On the contrary, if the ratio A / B exceeds 20, the flatness of the object to be polished is lowered, which is not preferable.

  Furthermore, since the cell 3 is vertically long and has a diameter that increases with distance from the polishing surface Sp, if the urethane sheet 2 is worn by the polishing process, polishing scraps and the like accompanying the polishing process are accommodated in the cell 3, particularly in the large cell 3a. The Rukoto. Thereby, since the accumulation of polishing scraps on the polishing surface Sp is suppressed, it is possible to suppress the occurrence of scratches on the object to be polished. In addition, since the polishing waste is accommodated in the cells 3, the opening is less likely to be clogged, so that the dressing operation that needs to be performed by interrupting the polishing process can be reduced. Thereby, the efficiency of the polishing process can be improved, and the polishing process can be continued stably for a long time.

  Furthermore, in this embodiment, the large cell 3a formed in the urethane sheet 2 is formed such that the size in the longitudinal direction is 50% or more of the thickness t of the urethane sheet 2, and is 1 / of the size in the longitudinal direction. The maximum hole diameter A is provided at a position exceeding 2 and away from the polishing surface Sp. Further, the average pore diameter B of the holes formed in the cells 3 in a cross section parallel to the polishing surface Sp on the inner side by 5% of the thickness t from the polishing surface Sp of the urethane sheet 2 is adjusted to a range of 5 to 40 μm. The maximum pore diameter A of the large cell 3a is adjusted in the range of 50 to 300 μm. Therefore, in the urethane sheet 2, considering the portion divided into two in the thickness direction, the gap due to the cells 3 is formed larger on the back surface Sr side than on the polishing surface Sp side. Thereby, the cushioning property at the time of a grinding | polishing process is ensured, and the flatness improvement of a to-be-polished object can be aimed at. If the average pore diameter B is less than 5 μm, clogging is likely to occur during polishing, and if it exceeds 40 μm, the flatness of the object to be polished is lowered. In addition, if the maximum hole diameter A is less than 50 μm, sufficient cushioning properties cannot be obtained, and polishing waste is insufficiently accommodated and scratches easily occur. On the other hand, if it exceeds 300 μm, the flatness of the object to be polished decreases. This is not preferable.

  Furthermore, in the manufacturing method of this embodiment, the polyurethane resin solution prepared in the preparation step contains a blocked isocyanate compound, and the crosslinking agent is dissociated by heating in the cross-linking curing step to form a cross-linking bond in the polyurethane resin. Let For this reason, the conventional wet coagulation method can be applied, and the polishing pad 10 provided with the urethane sheet 2 which has been crosslinked and cured as a whole can be manufactured without requiring complicated steps and special equipment.

  In the present embodiment, the example in which the urethane sheet 2 by the wet coagulation method of polyurethane resin is used as the resin sheet is shown, but the present invention is not limited to this. For example, a polyurea resin or an acrylic resin may be used instead of the polyurethane resin, as long as a continuous foam structure is formed by a wet coagulation method. Further, for example, a polyurethane resin may be mixed and used, and other resins such as a polyurethane resin and a polyurea resin, an acrylic resin, and an acylated polysaccharide resin may be blended and used. In order to obtain a urethane sheet with high hardness, it is preferable to blend a polyurea resin or an acrylic resin.

  Moreover, in the manufacturing method of this embodiment, although the example using the blocked isocyanate compound which blocked the isocyanate group of polyvalent isocyanate with the blocking agent was shown as a crosslinking agent, this invention is not restrict | limited to this. . If the polyurethane resin is dissolved in an organic solvent and the polyurethane resin is regenerated in the aqueous coagulation liquid, then the crosslinker is reacted to form a cross-linked bond, the organic solvent for dissolving the resin and the aqueous coagulation liquid And stable. Moreover, it is preferable that it is a compound which can express reactivity by the heating in a bridge | crosslinking hardening process, and it is suitable to use a block isocyanate compound from such a viewpoint. In other words, in order to confirm that the urethane sheet is cross-linked, for example, the urethane sheet is placed in 100 parts by weight of DMF, left at room temperature overnight, and stirred for 30 minutes. Can be determined by not completely dissolving.

  Furthermore, in the manufacturing method of this embodiment, although the example which uses DMAc for melt | dissolution of a polyurethane resin in the preparatory process was shown, this invention is not limited to this. Although DMSO and THF described above can be used, it is preferable to use DMAc or NMP as the organic solvent in view of increasing the hardness and increasing the density of the resulting urethane sheet 2.

  Furthermore, although not particularly mentioned in the present embodiment, a buff process or a slice process may be performed on the back surface Sr side of the urethane sheet 2. Since the thickness of the urethane sheet 2 can be made uniform by buffing or slicing, the pressing force on the object to be polished can be equalized and the flatness of the object to be polished can be improved. Furthermore, in this embodiment, although not particularly mentioned, grooving or embossing may be performed on the surface Sp side of the urethane sheet 2 so as to promote supply of polishing liquid and discharge of polishing waste.

  Furthermore, in the present embodiment, an example in which the double-sided tape 7 having the base material 7a is bonded to the back surface Sr side of the urethane sheet 2 and the base material 7a also serves as the base material of the polishing pad 10 is shown. It is not limited to. For example, even if only the adhesive is provided in place of the double-sided tape 7, it can be attached to the polishing machine. Further, another base material may be bonded between the double-sided tape 7 and the urethane sheet 2. In consideration of handling when the polishing pad 10 is transported or mounted on a surface plate, it is preferable to have a base material.

  Although not particularly mentioned in the present embodiment, the urethane sheet 2 has at least a light transmitting portion that allows light transmission for optically detecting the polishing state of the object to be polished. It may be. This light transmission portion is preferably formed so as to penetrate through the entire thickness t of the urethane sheet 2. In this way, for example, a light-emitting element such as a light-emitting diode provided on the polishing machine side or a light-receiving element such as a phototransistor detects the polishing state of the processing surface of the object to be polished through the light transmitting part during polishing. can do. As a result, the end point of the polishing process can be properly detected, and the polishing efficiency can be improved.

  Hereinafter, 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, a polyester polyol compound-MDI-ethylenediamine-based polyurethane resin (polyurethane polyurea resin) was used for producing the urethane sheet 2. As a crosslinking agent, a blocked isocyanate compound in which an unreacted isocyanate group at the end of a urethane prepolymer obtained by reacting 2,4-tolylene diisocyanate with PTMG having a number average molecular weight of 650 at a ratio of 2: 1 is protected with methyl ethyl ketoxime, This blocked isocyanate compound was mixed at a ratio of 10% by weight with respect to the polyurethane resin to prepare a DMAc solution of the polyurethane resin. Further, in order to form a foamed structure having a high hardness and a ratio A / B of the maximum pore diameter A to the average pore diameter B in the above-described range, the solid content concentration is set to 35% by weight using DMAc as the organic solvent of the polyurethane resin solution, An aqueous solution containing 5% by weight of DMAc was used as the coagulation liquid. When applying the polyurethane resin solution to the film forming substrate, the clearance of the coating apparatus was set to 1.6 mm. In the crosslinking and curing step, heating was performed at a temperature of 160 ° C. for 20 minutes. A surface buffing treatment was performed after the crosslinking and curing, and the obtained urethane sheet 2 having a thickness of 1.3 mm and the double-sided tape 7 were bonded together to produce a polishing pad 10.

(Comparative Example 1)
In Comparative Example 1, the same procedure as in Example 1 was conducted, except that no crosslinking agent was added to the polyurethane resin solution, DMF was used as the organic solvent for the polyurethane resin solution, the solid content concentration was 28 wt%, and the coagulation liquid was water. A polishing pad was produced. That is, Comparative Example 1 is a polishing pad manufactured by a conventional wet coagulation method.

(Evaluation 1)
About the polishing pad of Example 1 and Comparative Example 1, the Shore D hardness, the size of the cell 3 in the cross section, and the presence or absence of crosslinking were evaluated. In the measurement of Shore D hardness, a sample piece (10 cm × 10 cm) is cut out from a urethane sheet, and a plurality of sample pieces are stacked so as to have a thickness of 4.5 mm or more, and a D-type hardness meter (Japanese Industrial Standard, JIS K). 7311). For example, when the thickness of one sample piece is 1.3 mm, four samples are stacked and measured. In the measurement of the size of the cell 3, the maximum pore diameter A of the large cell 3a and the average pore diameter B of the cell 3 are measured from the cross-sectional photograph of the urethane sheet 2 by a scanning electron microscope, and the average per unit area of the ratio A / B The value was calculated. Confirmation of the presence or absence of cross-linking is a case where a urethane sheet is placed in 100 parts by weight of DMF, left standing at room temperature overnight and stirred for 30 minutes, and dissolved when there is no cross-linking and a gel-like residue is observed. It was determined that there was crosslinking. The results of Shore D hardness, maximum pore diameter A, average pore diameter B, ratio A / B and presence / absence of crosslinking are shown in Table 1 below.

  As shown in Table 1, in Comparative Example 1, although the ratio A / B was 20.5, it was a relatively soft material having a D hardness of 5 degrees. On the other hand, in Example 1, the D hardness was increased to 30 degrees, and the solid content concentration was 35% by weight using DMAc as the organic solvent of the polyurethane resin solution, and the coagulating liquid was DMAc 5% by weight. Ratio A / B showed 9.6 because it was set as the aqueous solution containing. From this, in Example 1, it can be expected that the outer edge portion of the object to be polished is excessively polished and the flatness is improved.

(Evaluation 2)
Polishing of the aluminum substrate for hard disk using the polishing pad of Example 1 and Comparative Example 1 and the hard closed foam type polishing pad (Nitta Haas IC1000, Shore D hardness 55 degrees) as Comparative Example 2 is as follows. The polishing performance was evaluated based on the presence or absence of roll-off and scratch. Roll-off occurs when the outer edge of the object to be polished is excessively polished from the center, and is one of the measurement items for evaluating flatness. As a measuring method, for example, a two-dimensional profile image is obtained within a range of 1.5 mm in the radial direction from a position of 0.5 mm from the outer peripheral end to the center with an optical surface roughness meter. In the obtained two-dimensional profile image, when the radial direction is the X axis and the thickness direction is the Y axis, the values of the Y axis at the coordinate positions of X = 0.5 mm and X = 1.5 mm from the outer peripheral end are Y Leveling correction was performed so that = 0, and the PV value of X = 0.5 to 1.5 mm of the two-dimensional profile image at this time was obtained. A surface roughness measuring machine (manufactured by Zygo, model number New View 5022) was used for the roll-off measurement. Presence / absence of scratch was determined by visual observation of the polished object after polishing. The measurement results for the presence or absence of roll-off and scratch are shown in Table 2 below.
Polishing machine used: 9B-5P polishing machine, manufactured by Speed Fem Co., Ltd. Rotation speed: (Surface plate) 30 r / m
Polishing pressure: 90 g / cm ²
Abrasive: Colloidal silica slurry (average particle size: 0.05 μm)
Object to be polished: 95 mmφ hard disk aluminum substrate Polishing time: 300 seconds

  As shown in Table 2, in Comparative Example 1, although no scratch was observed, the roll-off showed 258 nm, and sufficient flatness could not be obtained at the outer edge of the object to be polished. Further, in Comparative Example 2, although the roll-off was superior to that of Comparative Example 1, it was an independent foaming type, so that generation of scratches was observed. On the other hand, in Example 1, not only the scratch was not recognized, but also the roll-off was improved to 21 nm, and the flatness accuracy was improved. This is hardened by producing a urethane sheet 2 using a polyurethane resin solution blended with a cross-linking agent, and using DMAc as the organic solvent of the polyurethane resin solution to a solid content concentration of 35% by weight, It is considered that a foamed structure having a ratio A / B in the above-described range was obtained by using an aqueous solution containing 5% by weight of DMAc as a coagulating liquid.

  INDUSTRIAL APPLICABILITY Since the present invention contributes to the manufacture and sale of a polishing pad in order to provide a polishing pad and a method for manufacturing the polishing pad that can secure cushioning properties and improve the flatness accuracy of an object to be polished, Have potential.

Sp Polishing surface 2 Urethane sheet (resin sheet)
3 cells (foaming)
3a Large cell (large foam)
10 Polishing pad

Claims (9)

  In a polishing pad having a resin sheet having a polishing surface for polishing a workpiece to be polished, a large number of vertically long foams are formed in the thickness direction by a wet coagulation method. Yes, and large foaming of 50% or more of the foam in the thickness direction of the foam observed in the cross section in the thickness direction exceeds 1/2 of the length of the large foam. It has a maximum pore diameter A at a position separated from the polishing surface by a length, and the average pore diameter B of the foamed holes including the large foam formed inside the polishing surface by 5% of the entire thickness. The polishing pad, wherein the average value per unit area of the ratio A / B of the maximum pore diameter A is in the range of 5-20.   The polishing pad according to claim 1, wherein the resin sheet has a Shore D hardness in a range of 25 degrees to 65 degrees.   The polishing pad according to claim 2, wherein the resin sheet has an average pore diameter B in a range of 5 μm to 40 μm.   The polishing pad according to claim 3, wherein the resin sheet has a maximum pore diameter A in a range of 50 μm to 300 μm.   The polishing pad according to claim 1, wherein the resin sheet is made of polyurethane resin.   6. The resin sheet according to claim 5, wherein micropores are formed between the foams including the large foam, and the resin sheet has a continuous foam structure in which the foam including the large foams and the micropores communicate with each other. Polishing pad. It is a manufacturing method of the polishing pad according to claim 1,
A solution preparing step of dissolving a resin in an organic solvent and preparing a resin solution containing a crosslinking agent in which a plurality of reactive functional groups are protected by a protecting group;
After spreading the resin solution prepared in the solution preparation step into a sheet shape, the coagulation regeneration step in which the resin is regenerated by coagulating in a coagulation liquid containing water as a main component;
The resin regenerated in the coagulation regeneration step is heated to dissociate the protective group from the cross-linking agent, and the cross-linking and curing step to cross-link and cure the entire resin with the cross-linking agent from which the protective group has been dissociated,
Manufacturing method.   The production method according to claim 7, wherein the crosslinking agent contained in the resin solution in the solution preparation step is a blocked isocyanate compound protected with a blocking agent.   9. The production method according to claim 8, wherein the organic solvent used in the solution preparation step is N, N-dimethylacetamide or N-methyl-2-pyrrolidone.

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