JP5502539B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad provided with a resin sheet that is manufactured by a wet coagulation method and has an opening formed on a polishing surface for polishing an object to be polished.

  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 a polishing pad for a semiconductor device, a resin sheet formed of a polyurethane resin foam is mainly used. In addition, an opening is formed on the surface (polishing surface) of the resin sheet in order to easily hold the slurry during the polishing process. However, since polyurethane resin generally has water repellency, it has low wettability with respect to the slurry, and therefore, it is necessary to make the slurry conform to the slurry by a break-in operation in a preparatory step before polishing. It is desirable to shorten the time required for the break-in operation because it leads to loss of production time. In addition, agglomeration is formed due to accumulation of abrasive grains and polishing debris (sludge) in the slurry in the openings formed in the polished surface, which may cause scratches (polishing scratches) on the processed surface.

  In order to avoid these problems, for example, an ester-based polyurethane resin is used instead of an ether-based polyurethane resin in the main chain structure, ethylene glycol is introduced into the main chain structure, and a surfactant is added. It is known to impart hydrophilicity by blending or the like. By imparting such hydrophilicity, agglomeration of abrasive grains and sludge is suppressed, so that generation of scratches can also be suppressed (see, for example, Patent Document 1).

JP 2002-9026 A

  However, when hydrophilicity is imparted as in the technique of Patent Document 1, the hydrolysis resistance of the resin is reduced, or the surfactant component is eluted in the polishing liquid and causes unexpected aggregation. A problem occurs. On the other hand, in the technique of forming a polyurethane resin foam by a wet coagulation method, a suede type resin sheet having relatively excellent wettability and flexibility can be obtained. The break-in operation can be shortened by having excellent wettability, and the occurrence of fatal scratches can be slightly reduced by having excellent flexibility. On the other hand, even if hydrophilicity is imparted, the generation of scratches is not improved, and on the other hand, it can be seen that it increases, and because of the formation of huge pores unique to the wet coagulation method, abrasive grains are more easily taken in. In some cases, fine scratches may occur due to retention or aggregation. Such fine scratches are not negligible while further accuracy and miniaturization of the workpiece is required. When aiming at yield improvement and efficient manufacture, the polishing pad which can suppress such a fault is anxious.

  In view of the above-described problem, an object of the present invention is to provide a polishing pad that can suppress scratches and improve flatness accuracy.

  As a result of intensive studies on the relationship between the characteristics of the polishing pad and the occurrence of scratches, the present inventors have adjusted the hydrophilicity of the resin sheet, and the scratches from the relationship between the water absorption time on the polishing surface, the pore structure, and the compressibility. As a result, it was found that the reduction can be achieved.

In order to solve the above problems, the present invention provides a polishing pad comprising a resin sheet produced by a wet coagulation method and having an opening formed in a polishing surface for polishing an object to be polished. It is formed of at least two kinds of resin components having a difference in SP value indicating a solubility coefficient within a range of 1 to 3, and has a microporous structure in which micropores communicate with each other. It is formed, and the water absorption time when a 1 μL water droplet is deposited on the polished surface is in the range of 10 to 60 seconds.

In the present invention, the resin sheet is formed of at least two kinds of resins having different SP values in the range of 1 to 3, so that hydrophilicity is optimized without unnecessarily swelling, and a microporous structure is provided. Since the water absorption time when a 1 μL water droplet is deposited on the polished surface of the resin sheet is 10 to 60 seconds, it is difficult to absorb the polishing liquid supplied during the polishing process, and the abrasive particles adhere to the polished surface. Since the abrasive grains are less likely to agglomerate due to being suppressed, scratching can be suppressed and the flatness accuracy can be improved.

  In this case, it is good also considering the average hole diameter per unit area of the opening formed in the grinding | polishing surface as the range of 3 micrometers-15 micrometers. The resin sheet may be made of a resin mainly composed of a polyurethane resin. At this time, all of the resin components are soluble in a polar solvent having an SP value in the range of 9 to 13, and may have an SP value in the range of 8 to 13. At this time, the resin sheet is formed by mixing resin components, and the overall SP value can be in the range of 9-11. The resin sheet may be formed by mixing at least two kinds of resins selected from polyurethane resin, acrylic resin, polyvinyl chloride resin and polysulfone resin. A polyurethane resin as a resin component may be blended in the resin sheet in a range of 50 wt% to 98 wt%. The compression rate of the resin sheet can be in the range of 0.5% to 3.0%.

According to the present invention, the resin sheet is formed of at least two kinds of resins having a difference in SP value in the range of 1 to 3, so that hydrophilicity is optimized without unnecessarily swelling, and microporous. Since the water absorption time when a 1 μL water droplet is deposited on the polished surface of the resin sheet having a structure is in the range of 10 seconds to 60 seconds, the polishing liquid supplied at the time of polishing processing becomes difficult to be absorbed, and the polished surface of the abrasive grains By suppressing the adhesion to the abrasive grains, it becomes difficult for the abrasive grains to agglomerate. Therefore, it is possible to obtain an effect of suppressing the scratches and improving the flatness accuracy.

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

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

(Constitution)
As shown in FIG. 1, the polishing pad 10 of the present embodiment includes a resin sheet 2 in which two types of resin components are mixed. The resin sheet 2 is formed into a sheet shape by a wet coagulation method, and has a polishing surface P for polishing an object to be polished on one surface side.

  The resin sheet 2 is formed in a state where a large number of micropores 4 are dispersed substantially uniformly throughout the resin. The microporous 4 is formed in a spherical shape, and has an average diameter of 3 to 15 μm. The micropores 4 communicate with each other in a network form with channels smaller than the micropores 4 due to solvent substitution during film formation by the wet coagulation method. That is, the resin sheet 2 has a microporous structure. In the resin sheet 2, a dense microporous skin layer formed at the time of film formation by the wet coagulation method is removed by a grinding process (buff process).

  On the polishing surface P, an opening 5 in which the micropore 4 is opened is formed. The average pore diameter of the apertures 5 per unit area is in the range of 3 to 15 μm, which is the same as the average diameter of the micropores 4. By forming the opening 5, a large number of micropores 4 formed inside the resin sheet 2 communicate with the opening 5 through the channel. In the resin sheet 2 having such a continuously formed microporous structure, deformation due to compression is less likely to occur as compared with a sheet in which giant pores are formed by a conventional wet coagulation method. The range of 5-3.0% is shown.

The resin sheet 2 is formed by mixing two different resin components having a difference in SP value, which is a solubility coefficient, in the range of 1 to 3, and the hydrophilicity is adjusted. That is, the water absorption time with respect to the polishing surface P of the resin sheet 2 is adjusted to a range of 10 to 60 seconds. For SP values, see J.H. H. Hildebrand et al. (JHHildebrand
and RLScott, “The Solubility of Nonelectrolytes”, published by Reinhold Publishing Corp., published in 1950), and the SP value δ [unit: (cal · cm ³ ) ^1/2 ] is expressed by the following formula (1) It is represented by In the formula (1), ΔE represents the molecular aggregation energy (unit: cal / mol), V represents the molar volume (unit: ml / mol), and the SP value corresponds to the square root of the aggregation energy density. In the case of mixing two kinds of resins, the closer the SP value is, the smaller the cohesive energy density and the higher the affinity. Hansen et al. (J.
Paint Technology, Vol. 39, No. 505, pages 104-117 and No. 511, pages 505-514 (issued in 1967) and Hoy (J. Paint
Technology, Vol. 42, No. 541, pages 76-118, issued in 1970), the dipole force and the hydrogen bond force are also taken into account, and based on the molecular attractive constant method, the SP value can be calculated by the following equation (2). it can. In the formula (2), ΔF is the sum of molecular attraction constants (unit: (Cal · cm ³ ) ^1/2 mol ⁻¹ ) (for the molecular attraction constant of each atomic group, for example, Hoy method Material Technology Study Group 41 pages of "Handbook for Painting and Printing of Plastics" edited by Editorial Board (published by General Technology Publishing), Okitsu et al., Adhesive Research Presentation, Vol. 27, 125-126 (issued in June 1989), Annual Meeting of the Adhesion Society of Japan (Abstract, 28, 85-86 (issued in June 1990)). Further, the SP value of the entire resin obtained by mixing a plurality of resins can be calculated by the following equation (3). In equation (3), δmix is the SP value of the entire mixed resin, Xn is the molar fraction of component n, Vn is the molar volume of component n, and δn is the SP value of component n. From the above, in the polishing pad 10, the resin sheet 2 is dissolved in a polar solvent, each resin component is separated by gel filtration or the like, and each molecular structure analysis is performed to thereby determine the SP value of each resin component and the mixed resin. The overall SP value can be calculated.

  Further, the polishing pad 10 has a double-sided tape 7 attached to the surface opposite to the polishing surface P of the resin sheet 2 for mounting the polishing pad 10 on a polishing machine. 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 resin sheet 2 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 resin 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)
For the polishing pad 10, a resin sheet 2 is prepared by using a wet coagulation method using two kinds of resin components having different SP values in the range of 1 to 3, and the obtained resin sheet 2 and the double-sided tape 7 are bonded together. Manufactured by. That is, a preparation step for preparing a resin solution, a coating step for applying a resin solution to a film forming substrate in a sheet form, a coagulation regeneration step for coagulating the resin solution in a coagulation liquid to regenerate the resin, and a regenerated sheet resin The polishing pad 10 is manufactured through a washing / drying step for washing and drying, a buffing step for removing the skin layer by buffing, and a laminating step for bonding the obtained resin sheet 2 and the double-sided tape 7 together. Hereinafter, it demonstrates in order of a process.

  In the preparation step, the resin component is dissolved by mixing two kinds of resin components having different SP values in the range of 1 to 3, a water-miscible polar solvent capable of dissolving the resin component, an additive, and a crosslinking agent. As the polar solvent, those having an SP value in the range of 9 to 13 are used. For example, N, N-dimethylformamide (DMF) with SP value of 12.1, N, N-dimethylacetamide (DMAc) with SP value of 10.8, tetrahydrofuran (THF) with SP value of 9.1, SP value Dimethyl sulfoxide (DMSO) having an SP value of 9.9, acetonitrile having an SP value of 11.9, N-methylpyrrolidone (NMP) having an SP value of 11.3, and the like can be used. If the SP value is smaller than 9 or larger than 13, it is not preferable because substitution with a poor solvent (water) at the time of coagulation regeneration is insufficient, and sheet production becomes difficult. In this example, DMF with an SP value of 12.1 is used.

  On the other hand, the two types of resin components having different SP values in the range of 1 to 3 include those soluble in the polar solvent described above, such as polyurethanes such as polyurethane and polyurethane polyurea, polyacrylates, polyacrylonitrile and the like. Acrylic, polyvinyl chloride, polyvinyl acetate, vinyl type such as polyvinylidene fluoride, polysulfone type such as polysulfone and polyethersulfone, acylated cellulose type such as acetylated cellulose and butyryl cellulose, polyamide type, polystyrene type, Etc. The combination of the two resin components is preferably selected so that the SP value of the entire resin is in the range of 9-11. If the overall SP value is smaller than 9, it is not preferable because the wettability with respect to the slurry is lowered. Conversely, if the SP value is larger than 11, it is not preferable because the slurry easily penetrates and adheres. Moreover, as each SP value of a resin component, it is preferable that it is the range of 8-13. If the SP value of the resin component is smaller than 8, it is not preferable because the wettability with respect to the slurry is lowered. Conversely, if the SP value is larger than 13, the slurry adheres even if the SP value of the entire resin is in the range of 9-11. Since it may become easy, it is not preferable. Suitable resin components include two types of combinations selected from polyurethane resins, acrylic resins, polyvinyl chloride resins, and polysulfone resins.

  Among the resin components described above, when the polyurethane resin is blended in the range of 50 to 98% by weight with respect to the entire resin component, appropriate elasticity and desired effects can be easily obtained. The polyurethane resin may be any of polyester, polyether, polyether polyester, polycarbonate, polyester polycarbonate, polycaprolactone, and the like. Examples of the acrylic resin include (meth) acrylic acid alkyl esters having 1 to 13 carbon atoms in the alkyl group such as methyl (meth) acrylate and butyl (meth) acrylate, cyclohexyl (meth) acrylate, and hydroxyethyl (meth) ) Acrylate, hydroxypropyl (meth) acrylate, acrylonitrile, (meth) acrylamide, N-dimethylmethacrylamide, vinyl acetate, styrene, α-methylstyrene, (meth) acrylic acid, crotonic acid, itaconic acid, N-methylol (meth) ) One or more polymers of monomers such as acrylamide, glycidyl methacrylate, ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, and the like can be mentioned. As the polyvinyl chloride resin, a vinyl chloride monomer copolymerized with various monomers can be used. Examples of the monomer to be copolymerized include the above-mentioned acrylic resin monomers and alkyl allyl ethers. Examples of the polysulfone resin include polyphenylsulfone and polyethersulfone.

  What is necessary is just to select two types of resin components from which the difference of SP value differs in the range of 1-3 among these resin components. For example, a polyether polyurethane resin having an SP value of 11.0 and a methyl (meth) acrylate acrylic resin having an SP value of 9.1 have a weight ratio of 1: 1, and the SP value of the entire resin is 10.1. A polyester polyurethane resin having an SP value of 12.3 and a polyether polyurethane resin having an SP value of 10.5 may be used at a weight ratio of 1: 5, and the SP value of the entire resin is 10.8. May be. If the difference between the SP values of the two resin components is smaller than 1, it is not preferable because the slurry easily permeates and tends to cause adhesion and aggregation. On the contrary, if the difference in SP value is larger than 3, it is not preferable because the compatibility of the resin component is deteriorated and stable production becomes difficult. In this example, a polyether polyurethane resin having an SP value of 11.0 and a methyl (meth) acrylate acrylic resin having an SP value of 9.1 are mixed at a weight ratio of 1: 1, and the resin component is 30% by weight. Dissolve in DMF. In this case, the SP value of the entire resin is 10.1. As the additive, a pigment such as carbon black, a hydrophilic activator that promotes foaming, a hydrophobic activator that stabilizes the coagulation regeneration of the resin, and the like are used to control the size and amount (number) of the micropores 4. be able to.

  In addition, an adjustment solvent is added to a solution in which the resin component is dissolved in DMF in order to delay substitution of DMF with water. By delaying the replacement of DMF with water, the above-described microporous resin sheet can be formed. As the adjustment solvent, a solvent having a solubility in water smaller than that of DMF and capable of being uniformly mixed and dispersed with the resin component solution without solidifying (gelling) the resin component dissolved in DMF is used. As such an adjustment solvent, ethyl acetate, isopropyl alcohol, or the like can be used. In this example, ethyl acetate is used. The adjustment solvent is mixed so as to be in the range of 20 to 45 parts with respect to 100 parts of the resin component solution, and then defoamed under reduced pressure to obtain a resin solution.

  In the coating step, the resin solution obtained in the preparation step is applied substantially uniformly in a sheet form to the belt-shaped film forming substrate by a coating device such as a knife coater at room temperature. At this time, the application thickness (application amount) of the resin solution is adjusted by adjusting the gap (clearance) between the knife coater 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.

  In the coagulation regeneration step, the 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 resin component. In order to adjust the coagulation regeneration rate of the polyurethane resin, an organic solvent such as DMF or a polar solvent other than DMF may be added to the coagulation liquid. In this example, water is used. The resin solution is solidified in the coagulation liquid, and the resin having a microporous structure is regenerated.

  Here, the formation of the microporous structure accompanying the regeneration of the resin will be described. In the coagulation liquid, first, a film is formed at the interface between the resin solution and the coagulation liquid, and fine micropores constituting the skin layer are formed in the resin immediately adjacent to the film. Thereafter, regeneration of the resin proceeds by a cooperative phenomenon of diffusion of DMF in the resin solution into the coagulating liquid and intrusion of water into the resin, that is, solvent substitution. Since the solubility of the adjustment solvent added to the resin solution in water is smaller than that of DMF, the elution of the adjustment solvent in water (coagulation liquid) is slower than in DMF. In addition, the amount of DMF in the resin solution is reduced by adding the adjustment solvent. For this reason, since the substitution rate of DMF and the adjustment solvent and the coagulating liquid is slow, the formation of giant pores is suppressed. Thereby, the micropore 4 is formed inside the skin layer of the resin. Since the replacement rate of DMF and adjusting solvent with the coagulation liquid is slow, the size of the micropores 4 becomes larger than the micropores of the skin layer formed immediately after being immersed in the coagulation liquid. In addition, when DMF is removed from the resin solution and DMF and the coagulating liquid are replaced, a channel is formed between the micropores 4, and the micropores and micropores 4 of the skin layer communicate with each other in a mesh shape. Accordingly, the obtained sheet-like resin has a substantially uniform and substantially uniform microporous structure in which huge pores are not formed.

  In the cleaning / drying step, the solidified and regenerated sheet-like resin (hereinafter referred to as film-forming resin) is washed in a cleaning solution such as water to remove DMF remaining in the film-forming resin, and then dried. In this example, a cylinder dryer having a cylinder having a heat source is used for drying the film-forming resin. The film-forming resin is dried by passing along the peripheral surface of the cylinder. The film-forming resin after drying is rolled up.

  In the buffing process, a buffing process is performed on the surface side on which the skin layer of the film-forming resin dried in the cleaning / drying process is formed. In the film-forming resin, thickness variation occurs during wet film formation, so that unevenness appears on the surface on the skin layer side by pressing a pressure welding jig having a flat surface on the surface opposite to the skin layer. This unevenness is removed by buffing. In this example, the film-forming resin produced continuously is subjected to buffing continuously or intermittently while being pressed against the pressing roller. In the resin sheet 2 formed by buffing the film-forming resin, the thickness is made uniform, and the opening 5 is formed on the surface.

  In the laminating process, the resin sheet 2 and the double-sided tape 7 are bonded together. At this time, the surface opposite to the polishing surface P of the resin 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 such as a circle or a square and a desired size, an inspection is performed to confirm that there are no scratches, dirt, foreign matter, or the like, 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. The slurry used here is colloidal silica having an average particle diameter of 50 nm as abrasive grains, and the abrasive grains are dispersed at a ratio of 5% by weight.

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

  In the present embodiment, the resin sheet 2 is made of two types of resin components having different SP values within a range of 1 to 3. In addition, the resin sheet 2 has a continuous microporous structure in which the micropores 4 communicate with the apertures 5 through the channels. By determining the SP value, hydrophilicity is optimized without unnecessarily swelling the resin sheet. Moreover, compared with the case where a huge pore is conventionally formed, the water absorption time with respect to the grinding | polishing surface P of the resin sheet 2 is restrict | limited by having a microporous structure. Thereby, the water absorption time of the resin sheet 2 will show the range of 10 to 60 seconds. Accordingly, the water absorption time is limited by the hydrophilicity of the resin and the microporous structure, so that the slurry supplied at the time of polishing processing is hardly absorbed, and the polishing surface P of the abrasive grains contained in the slurry and the inner surface of the opening 5 Adhesion to the surface is suppressed and the abrasive grains are less likely to aggregate. As a result, since the generation of scratches on the object to be polished is suppressed, the flatness accuracy can be improved. Moreover, since the wettability of the resin sheet 2 with respect to the polishing liquid is also optimized, the time required for the break-in operation before the polishing process can be shortened, and the polishing efficiency can be improved.

  Further, in the present embodiment, the skin layer formed at the time of film formation by the wet coagulation method is removed by buffing, and the opening 5 is formed on the polished surface P. The opening 5 has an average pore diameter per unit area adjusted to a range of 3 to 15 μm. For this reason, since the slurry is held at the time of polishing processing while being distributed substantially evenly between the object to be polished and the polishing pad 10, the flatness accuracy of the object to be polished can be improved.

  Furthermore, in this embodiment, the resin sheet 2 has a continuous microporous structure. For this reason, a compression rate will show the range of 0.5 to 3.0% because a huge pore is not formed, and a softness | flexibility will be suppressed. When huge pores are formed, it becomes easier to take in abrasive grains and polishing debris from the openings formed in the polishing surface due to increased flexibility, causing retention and aggregation and impairing the flatness of the object to be polished. Become. Therefore, in the resin sheet 2 having a microporous structure, the flexibility is optimized and the opening 5 is less likely to be blocked, so that the flatness of the object to be polished can be improved stably for a long period of time.

  In the present embodiment, an example in which a polyurethane resin and an acrylic resin are used as a resin component to produce the resin sheet 2 by a wet coagulation method is shown, but the present invention is not limited to this. For example, as described above, instead of acrylic resin, polyurethane resin, polyvinyl chloride resin, polysulfone resin or the like having different SP values may be used, and the SP value is in the above-described range. Any structure can be used. Moreover, in the resin sheet obtained by making small SP value of the resin component to mix | blend, since a softness | flexibility and water absorption are suppressed, adhesion of the abrasive grain with respect to the grinding | polishing surface or the inner surface of a hole can be suppressed. Furthermore, in the present embodiment, the resin sheet 2 formed by blending two kinds of resin components is exemplified, but the present invention is not limited to this, and three or more kinds of the resin components described above are blended. It may be.

  Moreover, in this embodiment, the adjustment solvent is added to the resin solution at the time of film formation by the wet coagulation method, so that the solvent substitution at the time of coagulation regeneration is delayed and the resin sheet 2 having a microporous structure is formed. Although shown, the present invention is not limited to this. In order to obtain a microporous structure, the solvent substitution at the time of coagulation regeneration may be slowed. Instead of using the adjustment solvent, for example, a polar solvent used for dissolving the resin component is mixed in the coagulation liquid. Can also be realized. In this case, since the concentration of the polar solvent in the coagulating liquid is high when the resin solution applied to the film forming substrate is guided into the coagulating liquid, elution of the polar solvent from the resin solution is suppressed. . For this reason, solvent substitution at the initial stage of solidification is delayed, and a dense skin layer is hardly formed. As a result, a resin sheet having a microporous structure can be obtained.

  Furthermore, in this embodiment, although the example which performs the buff process to the skin layer side of the film-forming resin obtained after coagulation reproduction was shown, this invention is not restrict | limited to this. In order to make the thickness of the resin sheet uniform, the surface side opposite to the skin layer may be buffed, or both the skin layer side and the surface opposite to the skin layer may be buffed. Good. In addition, a slice process or the like can be performed instead of the buff process. By equalizing the thickness of the resin sheet, the pressing force applied to the object to be polished during the polishing process is equalized, and the flatness of the object to be polished can be improved.

  Furthermore, in this embodiment, the double-sided tape 7 having the base material 7 a is bonded to the surface opposite to the polishing surface P of the resin sheet 2, and the base material 7 a also serves as the base material of the polishing pad 10. However, the present invention is not limited to this. 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 resin 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.

  Furthermore, in the present embodiment, although not particularly mentioned, the resin sheet 2 has at least a light transmission part that allows light transmission for optically detecting the polishing state of the object to be polished. You may do it. The light transmission part is preferably formed so as to penetrate through the entire thickness of the resin 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, the weight ratio of a polyether MDI (diphenylmethane diisocyanate) polyurethane resin having an SP value of 11.0 and a methyl (meth) acrylate acrylic resin having an SP value of 9.1 was 1 for producing the resin sheet 2. : 1 and the total resin SP value was 10.1. These resin components were dissolved in DMF so as to be 30% by weight, and ethyl acetate was further added as a adjusting solvent. When applying the obtained resin solution to the film-forming substrate, the clearance of the coating apparatus was set to 1.6 mm. After buffing the film-forming resin after the coagulation regeneration, the resulting resin sheet 2 having a thickness of 1.3 mm and the double-sided tape 7 were bonded together to produce a polishing pad 10. In the resin sheet 2 constituting the polishing pad 10 of Example 1, the polyurethane resin component is 50% by weight of the entire resin.

(Example 2)
In Example 2, a polyester TDI (tolylene diisocyanate) polyurethane resin having an SP value of 12.3 and a polyether TDI polyurethane resin having an SP value of 10.5 are blended at a weight ratio of 1: 5 in the production of the resin sheet 2. The polishing pad 10 was manufactured in the same manner as in Example 1 except that the resin having an SP value of 10.8 was used. In the resin sheet 2 constituting the polishing pad 10 of Example 2, the polyurethane resin component is 100% by weight of the entire resin.

(Example 3)
In Example 3, the production of the resin sheet 2 was carried out by blending a polyether sulfone resin having an SP value of 12.6 and a polyether TDI polyurethane resin having an SP value of 10.5 at a weight ratio of 1: 5. A polishing pad 10 was produced in the same manner as in Example 1 except that one having an SP value of 10.9 was used. In the resin sheet 2 constituting the polishing pad 10 of Example 2, the polyurethane resin component is 83% of the entire resin.

(Comparative Example 1)
In Comparative Example 1, a polishing pad was produced in the same manner as in Example 1 except that only the polyether MDI polyurethane resin having an SP value of 11.0 was used. That is, the polishing pad of Comparative Example 1 is a conventional polishing pad having a resin sheet formed of one resin component.

(Comparative Example 2)
In Comparative Example 2, a polishing pad was produced in the same manner as Comparative Example 1 except that the adjusted organic solvent ethyl acetate was not added. That is, the polishing pad of Comparative Example 2 is a conventional polishing pad in which huge pores are formed in a resin sheet.

(Comparative Example 3)
In Comparative Example 3, the polyether MDI polyurethane resin used in Example 1 and the methyl (meth) acrylate acrylic resin were blended at a weight ratio of 1: 2, and the total resin SP value was 9.7. A polishing pad was produced in the same manner as Example 1 except for the above. That is, the polishing pad of Comparative Example 3 is a polishing pad having a resin sheet in which the SP value of the entire resin is smaller than the above range.

(Comparative Example 4)
Comparative Example 4 was carried out except that the polyether sulfone resin and the polyether TDI polyurethane resin used in Example 3 were blended at a weight ratio of 1: 2, and the SP value of the entire resin was 11.2. A polishing pad was produced in the same manner as in Example 3. That is, the polishing pad of Comparative Example 4 is a polishing pad having a resin sheet in which the SP value of the entire resin is larger than the above range.

(Evaluation 1)
About the polishing pad of each Example and the comparative example, the average hole diameter, the water absorption time, and the compressibility were measured. In the measurement of the average pore diameter, a scanning electron microscope (JSM-5500LV, JSM-5500LV) was used. This image was processed with image processing software (Image Analyzer V20LAB Ver. 1.3) to calculate the average pore size. In the measurement of the water absorption time, a 1 μL droplet (water droplet) was deposited on the sample surface of the resin sheet, and the time from immediately after the droplet deposition until the droplet was absorbed into the sample and could not be identified was measured. The compression rate was determined using a shopper type thickness measuring instrument (pressure surface: circular shape with a diameter of 1 cm) in accordance with Japanese Industrial Standard (JIS L 1021). Specifically, the thickness t1 after applying the initial load (100 g / cm ² ) for 30 seconds from the no-load state is measured, and then the final pressure (1120 g / cm ² ) is set to 30 from the state of the thickness t1. The thickness t2 after applying for 2 seconds was measured. The compression rate was calculated by the equation: compression rate (%) = 100 × (t1−t2) / t1. The measurement results of average pore diameter, water absorption time and compressibility are shown in Table 1 below.

  As shown in Table 1, in Comparative Example 2, the average pore diameter was 32.4 μm, and the compression rate was 14.3%. It is thought that the compression rate increased due to the formation of giant pores. The water absorption time was 0.4 seconds. From this, it is considered that the amount of water entering the large pores has increased and the water absorption time has decreased. Further, when immersed in the polishing liquid, it is considered that the abrasive grains easily adhere to the surface including the inner surface of the large pores when the polishing liquid enters the large pores. On the other hand, in Comparative Example 1 in which giant pores were not formed, the water absorption time was 1.5 seconds. From this, it is considered that even if the giant pores are not formed, the water absorption time is short and the polishing liquid easily penetrates into the inside, so that the abrasive grains are likely to adhere. In Comparative Example 3, the average pore diameter was 4.4 μm and the compression rate was 1.0%. However, since the water absorption time is as long as 68.5 seconds, it is considered that the wettability with respect to the slurry is lowered. On the contrary, in Comparative Example 4, the compression rate was 0.8%, but the water absorption time was as short as 8.5 seconds, although the average pore diameter was as small as 2.8 μm. For this reason, when immersed in the polishing liquid, it is considered that the abrasive grains easily adhere to the surface including the inner surface of the pores. On the other hand, in Example 1, Example 2, and Example 3, the average pore diameters are 4.3 μm, 4.8 μm, and 3.5 μm, respectively, and the water absorption time is 55.2 seconds, 23.1 seconds, respectively. 13.2 seconds were shown, and the compression ratios were 0.7%, 2.7%, and 1.0%, respectively. Compared with that of Comparative Example 1, it is considered that the compressibility was reduced and the average pore diameter was also reduced by having a microporous structure. Further, it was found that the water absorption time becomes longer because the huge pores are not formed. Furthermore, in Example 1 and Example 3, it is thought that there exists an even more excellent effect by making the ratio of the polyurethane resin with respect to the whole resin into the range of 50 to 98% by mix | blending an acrylic resin and a polysulfone resin, respectively.

(Evaluation 2)
Moreover, using the holding pads of the examples and comparative examples, polishing was performed under the following polishing conditions, and the polishing rate, the waviness Wa, and the presence or absence of scratches were measured. As an object to be polished, an aluminum disk substrate for magnetic recording media on which nickel-phosphorus plating was applied was used. The polishing rate represents the amount of polishing per minute in terms of thickness, and was calculated from the polishing amount obtained from the weight reduction of the substrate before and after polishing, the polishing area of the substrate, and the specific gravity. In addition, the amount of surface image waviness per unit area in an optical non-contact surface roughness meter (manufactured by Zygo, New View 5022) in a short wavelength region of 0 to 80 μm and in a medium wavelength region of 80 to 500 μm, respectively, ) Calculated in units. Further, the amount of waviness before polishing was measured in the same manner. For the evaluation of scratch, the polished aluminum substrate was irradiated with light from a high-intensity halogen lamp and visually evaluated for the presence or absence of scratches on the surface of the aluminum substrate. The measurement results of the polishing rate, the waviness Wa and the scratch are shown in Table 2 below.
(Polishing conditions)
Polishing machine used: DSM9B-5P-IV, manufactured by Speedfam
Polishing speed (rotation speed): 30 rpm
Processing pressure: 100 g / cm ²
Slurry: Colloidal silica slurry (pH: 1.5)

  As shown in Table 2, in Comparative Example 1, the polishing rate was 0.105 μm / min. Further, in the undulation Wa, the undulation after polishing was improved compared to that before polishing in any wavelength range, but were 2.22 mm and 5.28 mm after polishing. On the other hand, in Examples 1, 2 and 3, although the average pore diameter was smaller than that in Comparative Example 1, the polishing rate was slightly improved and 0.120 μm / min, 0.114 μm / min, 0, respectively. .110 μm / min. In Example 1, the waviness Wa improved from 3.47 mm before polishing to 1.78 mm after polishing in the short wavelength region, and from 7.21 mm before polishing to 4.54 mm after polishing in the middle wavelength region. In Example 2, 3.61 mm before polishing was improved to 1.85 mm after polishing in the short wavelength range, and 7.45 mm before polishing was improved to 4.71 mm after polishing in the middle wavelength range. In Example 3, 3.51 mm before polishing was improved to 1.78 mm after polishing in the short wavelength range, and 7.45 mm before polishing was improved to 4.67 mm after polishing in the middle wavelength range. From this, it became clear that the flatness accuracy can be improved in the polishing pads 10 of Examples 1, 2 and 3 in which the water absorption time and the compressibility are balanced. In Comparative Example 3 and Comparative Example 4, both the polishing rate and the waviness Wa were inferior to those of the Examples. In Comparative Example 3, the water absorption time is too long, so that the wettability with respect to the slurry is low. In Comparative Example 4, although the average pore diameter is small, the water absorption time is too short, so the flatness accuracy is considered to have been reduced. . In particular, in Comparative Example 4, since scratches were also confirmed, it is considered that the abrasive grains easily adhered to the surface including the inner surface of the pores.

  Since the present invention provides a polishing pad that can suppress scratches and improve the flatness accuracy, it contributes to the manufacture and sale of the polishing pad, and thus has industrial applicability.

P Polishing surface 2 Resin sheet 4 Microporous 5 Open hole 10 Polishing pad

Claims (7)

In a polishing pad provided with a resin sheet produced by a wet coagulation method and having an opening formed in a polishing surface for polishing an object to be polished, the resin sheet has an SP value difference of 1 to 3 indicating a solubility coefficient. And having a microporous structure in which micropores communicate with each other, an opening is formed in the polishing surface by the micropore, and 1 μL of the polishing surface is formed on the polishing surface . A polishing pad, wherein the water absorption time when a water droplet is deposited is in the range of 10 to 60 seconds.   2. The polishing pad according to claim 1, wherein the opening formed in the polishing surface has an average pore diameter per unit area in a range of 3 μm to 15 μm.   2. The polishing pad according to claim 1, wherein each of the resin components is soluble in a polar solvent having an SP value in the range of 9 to 13 and has an SP value in the range of 8 to 13.   The polishing pad according to claim 3, wherein the resin sheet is formed by mixing the resin components and has an overall SP value in the range of 9 to 11. 5.   The polishing pad according to claim 4, wherein the resin sheet is formed by mixing at least two kinds of resins selected from a polyurethane resin, an acrylic resin, a polyvinyl chloride resin, and a polysulfone resin.   2. The polishing pad according to claim 1, wherein the resin sheet contains a polyurethane resin in the range of 50 wt% to 98 wt% as the resin component.   The polishing pad according to claim 6, wherein the resin sheet has a compressibility in a range of 0.5% to 3.0%.

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