CN113226642A

CN113226642A - Polishing pad

Info

Publication number: CN113226642A
Application number: CN201980085424.3A
Authority: CN
Inventors: 服部和正; 加藤晋哉; 冈本知大; 高冈信夫; 林浩一
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2018-12-27
Filing date: 2019-12-25
Publication date: 2021-08-06
Anticipated expiration: 2039-12-25
Also published as: WO2020138198A1; JP7370342B2; TWI827778B; KR20210106436A; CN113226642B; JPWO2020138198A1; TW202035534A

Abstract

The invention provides a polishing pad with high polishing rate, which has excellent polishing performance of polishing stability and smoothness of a polishing object and is characterized in that the polishing performance changes little even if the polishing is continued for a long time. The polishing pad is obtained by impregnating a non-porous polymer elastomer and a porous polymer elastomer into a nonwoven fabric, wherein the porous polymer elastomer contains thermoplastic polyurethane, and the mass ratio of the non-porous polymer elastomer to the porous polymer elastomer is 0.49 or less.

Description

Polishing pad

Technical Field

The present invention relates to a polishing pad useful for polishing semiconductor wafers, silicon wafers, semiconductor devices, liquid crystal displays, hard disks, glass mirrors, metals, and the like.

Background

For mirror finishing of a semiconductor wafer used as a base material for forming an integrated circuit, Chemical Mechanical Polishing (CMP) is known. As the polishing pad used in CMP, the following polishing pads were used: a nonwoven fabric type sheet or film obtained by impregnating the nonwoven fabric with the wet-set polyurethane; a wet Polyurethane (PU) sponge-type sheet in which a polyurethane resin that has been wet-solidified is disposed on a surface layer of an upper layer of a fiber structure; a molded sheet of a polymer elastomer such as polyurethane having a closed cell structure. The nonwoven fabric type sheet and the wet PU sponge type sheet are relatively soft because they are easily compressed and deformed, while the molded sheet of the polymer elastomer has high rigidity.

In recent years, with the increase in integration and multilayer wiring, there has been an increasing demand for further improvement in quality and reduction in price of semiconductor wafers and semiconductor devices, such as higher planarization. As a wiring material, a copper alloy has been tried to be used instead of the conventional aluminum alloy, and as an insulating material, a conventional SiO has been replaced₂Attempts have been made to use low dielectric constant materials. With such changes in materials, polishing pads are also required to have further improved functions such as planarization higher than the conventional level, reduction of scratches on the wafer surface, improvement of polishing rate, improvement of stability during polishing, and long-term use. In addition, forIn order to achieve higher integration and higher precision in silicon wafers, liquid crystal displays, hard disks, glass mirrors, and the like, polishing pads are also required to have higher functionality, such as higher planarization than the conventional level, less surface scratches, higher polishing rate, higher stability during polishing, and longer service life.

The foamed polyurethane used for the polishing pad of the molded sheet is generally produced by casting, foaming and curing using a two-component curable polyurethane (for example, see patent documents 1 to 4). However, in these methods, homogenization of reaction/foaming is difficult, and there is a limit to increase in hardness of the resulting foamed polyurethane, and therefore, polishing characteristics such as flatness and planarization efficiency of the surface to be polished are likely to vary; further, since the foam structure is closed, slurry and polishing dust used in the polishing process are likely to enter pores and to clog the pores, which causes problems such as a decrease in polishing rate (polishing speed) and a short pad life. Under such circumstances, a polishing pad using a molded sheet made of foamed polyurethane that sufficiently satisfies the above-described required performances (e.g., further improvement in planarization efficiency, reduction in scratches on the wafer surface, improvement in polishing rate, improvement in stability during polishing, and improvement in pad life) cannot be obtained.

Therefore, particularly for materials such as copper wiring and low dielectric constant materials which are easily scratched or materials having poor interfacial adhesion, scratching and interfacial peeling are more likely to occur, and development of a novel polishing pad capable of coping with these is required.

On the other hand, a nonwoven fabric type polishing pad generally has a surface with a concavo-convex structure due to fibers, and a porous or interconnected pore structure due to the structure of the nonwoven fabric. Therefore, the polishing composition has characteristics such as good liquid retention of slurry during polishing (hereinafter, sometimes referred to as slurry retainability) and easy improvement of polishing rate, good cushioning property, softness, and good contact property with a wafer, and is used in various polishing fields. However, the conventional nonwoven fabric type polishing pad has insufficient planarization ability due to its large number of voids and flexibility, and also has insufficient stability during polishing, life of the polishing pad, and the like. Therefore, various studies have been made to improve the performance (see, for example, patent documents 6 to 14).

However, in any case, the following problems exist. That is, (1) the diameter of the fiber is about several tens of μm, and the difference in height of the unevenness of the polishing pad surface with respect to the wafer due to the fiber is relatively large, so that there is a limit to improvement of flatness, and the abrasive grains are likely to cause scratches when they are gathered in the fiber. In addition, when the ultrafine fibers are used, the hardness of the sheet formed of the ultrafine fibers is insufficient because of the very soft characteristic, or when the hardness is increased by using a very hard elastic polymer, the wafer is easily scratched due to the hardness and brittleness of the elastic polymer. (2) Since the nonwoven fabric has a low fiber density, the number of raised fibers (the density of the uneven structure) on the surface formed by the fibers is small, and the effect of compounding the fibers with the polymer elastomer is insufficient. (3) Since the density of the sheet is low and the number of pores is large, it is difficult to obtain a sheet having high hardness; and because there are huge non-woven fabric gaps of several hundred μm order of unevenness on the surface, there is a limit to the improvement of flatness; in addition, properties such as hardness tend to change with time during polishing, and there are problems in polishing stability and polishing pad life. (4) When the polymer elastomer is completely filled and the voids in the nonwoven fabric are eliminated, the formation of surface irregularities due to the fibers, the voids in the nonwoven fabric structure, and the features due to the interconnected pore structure are eliminated.

Under such circumstances, a polishing pad of a nonwoven fabric type has not been found which sufficiently satisfies the performances required in the market (further improvement in planarization efficiency, reduction in scratches on the wafer surface, improvement in polishing rate, improvement in stability at the time of polishing, life of the polishing pad, and the like).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2000-178374

Patent document 2: japanese patent laid-open No. 2000-248034

Patent document 3: japanese patent laid-open publication No. 2001-89548

Patent document 4: japanese laid-open patent publication No. 11-322878

Patent document 5: japanese laid-open patent publication No. 2002-9026

Patent document 6: japanese laid-open patent publication No. 11-99479

Patent document 7: japanese laid-open patent publication No. 2005-212055

Patent document 8: japanese laid-open patent publication No. 3-234475

Patent document 9: japanese laid-open patent publication No. 10-128797

Patent document 10: japanese patent laid-open publication No. 2004-311731

Patent document 11: japanese laid-open patent publication No. 10-225864

Patent document 12: japanese Kokai publication No. 2005-518286

Patent document 13: japanese patent laid-open publication No. 2003-201676

Patent document 14: japanese laid-open patent publication No. 2005-334997

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a polishing pad having a high polishing rate among nonwoven fabric-type polishing pads that have excellent polishing performance in polishing stability and smoothness of an object to be polished, and that have the characteristics of being capable of polishing for a long period of time and causing little change in polishing performance.

Means for solving the problems

One aspect of the present invention is a polishing pad obtained by impregnating a nonwoven fabric with a nonporous polymer elastomer and a porous polymer elastomer, wherein the porous polymer elastomer contains thermoplastic polyurethane, and a ratio of a mass of the nonporous polymer elastomer to a mass of the porous polymer elastomer is 0.49 or less.

Further, it is preferable that the porous polymer elastomer has an average pore area of 10 to 100 μm²The polishing pad of (1). The polishing pad is preferably one in which the solidification rate of the polymer diol forming the thermoplastic polyurethane contained in the porous polymer elastomer is 0.1 to 1.5 mol.Preferably, the polishing pad contains thermoplastic polyurethane having a D hardness of 35 to 85.

The polishing pad is preferably a polishing pad in which the fibers constituting the nonwoven fabric are polyester fibers and the average single fiber diameter is 1 to 10 μm.

With such a configuration, it is possible to obtain a polishing pad having a high polishing rate among nonwoven fabric-type polishing pads having excellent polishing performance in polishing stability and smoothness of an object to be polished, and having characteristics such that polishing is continued for a long time and a change in polishing performance is small.

The porous thermoplastic polyurethane comprises a thermoplastic polyurethane obtained by reacting a high-molecular diol, an organic diisocyanate, and a chain extender, wherein the high-molecular diol comprises at least 1 selected from the group consisting of polyethylene adipate, polybutylene adipate, polycaprolactone diol, 3-methyl-1, 5-pentanediol adipate, polyhexamethylene adipate, 3-methyl-1, 5-pentanediol terephthalate, polydiethylene adipate, polynaphthylene adipate, 2-methyl-1, 8-octanediol adipate, polyethylene glycol, polydiethylene glycol, polytetramethylene glycol, and polypropylene glycol, and the organic diisocyanate comprises at least 1 selected from the group consisting of 4, 4' -diphenylmethane diisocyanate, poly (trimethylene terephthalate), poly (tetramethylene terephthalate), and poly (tetramethylene terephthalate), and the like, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, isophorone diisocyanate, and the chain extender preferably comprises at least 1 selected from the group consisting of ethylene glycol, 1, 3-propylene glycol, 1, 4-butanediol, neopentyl glycol, 1, 5-pentanediol, 1, 6-hexanediol, and cyclohexanedimethanol.

In addition, the apparent density of the polishing pad is preferably 0.50 to 0.90g/cm³。

Further, the C hardness of the polishing pad is preferably 80 or more.

Further, the present invention is a method for manufacturing a polishing pad, comprising the steps of, in order: a step of imparting an aqueous nonporous polymeric elastomer to a nonwoven fabric formed of ultrafine fiber-forming fibers; a step of forming ultrafine fibers into an ultrafine fiber nonwoven fabric by ultrafine-fibrillating the ultrafine fiber-forming fibers; and a step of impregnating a solvent-soluble polymer elastomer and wet-solidifying the impregnated polymer elastomer to give a porous polymer elastomer such that the ratio of the mass of the non-porous polymer elastomer to the mass of the obtained porous polymer elastomer is 0.49 or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a polishing pad having a high polishing rate among polishing pads of a nonwoven fabric type can be obtained.

Detailed Description

Hereinafter, one embodiment of the polishing pad of the invention will be described in detail.

The polishing pad of the present embodiment is a polishing pad obtained by impregnating a nonwoven fabric with a nonporous polymer elastomer and a porous polymer elastomer, wherein the porous polymer elastomer contains thermoplastic polyurethane, and the ratio of the mass of the nonporous polymer elastomer to the mass of the porous polymer elastomer is 0.49 or less.

In the present invention, since the non-porous polymer elastomer and the porous polymer elastomer are impregnated in the nonwoven fabric and the ratio of the mass of the non-porous polymer elastomer to the mass of the porous polymer elastomer is adjusted to 0.49 or less, the polishing performance is less changed even if the polishing is continued for a long time, and the polishing rate can be increased.

In the present invention, the nonporous polymeric elastomer means an elastomer substantially having no pores, and specifically means an elastomer having an average pore area of less than 10 μm in the measurement of the average pore area described later²The term "porous polymer elastomer" as used herein means an elastomer having an average pore area of 10 μm in the measurement of the average pore area described later²The elastomer described above.

The nonwoven fabric is not particularly limited as long as it is a nonwoven fabric made of fibers mainly composed of a polyester resin such as nylon, polybutylene terephthalate (PBT) or polyethylene terephthalate (PET). In particular, when the nonwoven fabric is formed of polyester fibers, the storage modulus E' is less likely to change and the polishing efficiency is stable because water is less likely to be absorbed during polishing. For example, in the case of a fiber having high water absorption such as a nylon fiber, the storage modulus E' fluctuates due to a high water absorption rate during polishing, so that the polishing pad is easily deformed, and the polishing efficiency is easily lowered.

The average filament diameter of the polyester fibers is preferably 1 to 10 μm, and more preferably 1.5 to 8.5 μm. An average filament diameter of 1 μm or more is preferable because the fibers are not easily cut during trimming. In addition, when the average single fiber diameter is 10 μm or less, the load on the polishing target can be suppressed to be low, and therefore, the occurrence of scratches can be reduced.

As a method for obtaining the ultrafine fibers having the average single fiber diameter, a known method for ultrafine fiber formation from ultrafine fiber-forming fibers can be used. From the viewpoint of environmental protection, the ultrafine fiber-forming fiber is particularly preferably composed of a water-soluble polymer component and a poorly water-soluble polymer component. The water-soluble polymer component means a component which is removed by extraction from an aqueous solution, and the water-insoluble polymer component means a component which is not removed by extraction from an aqueous solution, that is, a polyamide resin represented by the above-mentioned nylon, and a polyester resin represented by polyethylene terephthalate. In addition, as for the superfine fiber generating fiber composed of the water-soluble polymer component and the water-insoluble polymer component, any multicomponent composite fiber such as sea-island type composite fiber and mixed spinning type fiber can be used as long as at least 1 component is a component that can be extracted and removed by the extraction treatment with an aqueous solution.

The water-soluble polymer component used in the present invention may be any polymer that can be extracted with an aqueous solution, and a known polymer, preferably a polyvinyl alcohol copolymer (hereinafter, also simply referred to as "PVA") that is soluble in an aqueous solution, may be used. PVA may be suitably used in view of: PVA can be easily dissolved and removed with hot water, and the shrinkage behavior during the removal by extraction with an aqueous solvent causes structural curling in the microfine fiber-forming fibers of the microfine fiber component, thereby making the nonwoven fabric bulky and dense; and substantially no decomposition reaction of the ultrafine fiber component and the elastic polymer component occurs during the extraction treatment, and therefore the thermoplastic resin and the elastic polymer component used for the ultrafine fiber component are not limited; and in view of the environment, etc.

The polishing pad of the present embodiment preferably contains a nonporous polymeric elastomer impregnated into a nonwoven fabric provided with polyester fibers, and a porous thermoplastic polyurethane having a D-hardness of 35 to 85.

The nonporous polymeric elastomer is mainly used for maintaining the form stability in the process of producing a nonwoven fabric. The porous thermoplastic polyurethane having a D hardness of 35-85 adjusts the hardness of the polishing pad and provides fine bubbles to the surface layer, thereby contributing to an improvement in the retention of the polishing slurry during CMP polishing. The nonporous polymer elastomer can be provided by, for example, impregnating a nonwoven fabric with an emulsion of a nonporous polymer elastomer and drying the impregnated nonwoven fabric. The porous thermoplastic polyurethane may be provided by impregnating a nonwoven fabric with a solution of a thermoplastic polyurethane forming the porous thermoplastic polyurethane and allowing the solution to wet solidify.

Specific examples of the nonporous polymeric elastomer include nonporous polymeric elastomers such as polyurethane, acrylonitrile elastomer, olefin elastomer, polyester elastomer, polyamide elastomer, and acrylic elastomer. Among them, polyurethane is preferable.

The nonporous polymer elastomer is preferably an aqueous nonporous polymer elastomer. For example, non-porous polyurethanes are preferably formed using aqueous emulsions. Specific examples of the aqueous emulsion of polyurethane include aqueous emulsions of polycarbonate polyurethane, polyester polyurethane, polyether polyurethane, and polycarbonate/ether polyurethane.

The non-porous polymer elastomer is preferably polyurethane having a glass transition temperature of-10 ℃ or lower, a storage modulus at 23 ℃ and 50 ℃ of preferably 1 to 40MPa, more preferably 1 to 35MPa, and a water absorption rate of 0.2 to 5 mass% when saturated water absorption is performed at 50 ℃. When the storage modulus at 23 ℃ and 50 ℃ is not less than the above lower limit, the polishing pad is preferably not easily deformed. When the storage modulus is not more than the upper limit, the hardness is not too high, and therefore, the occurrence of scratches can be suppressed. When the water absorption is too low, the amount of slurry held during polishing tends to decrease, and polishing uniformity tends to decrease. If the water absorption rate is too high, properties such as hardness tend to change during polishing, and polishing stability tends to be lowered.

When the porous polymer elastomer contained in the polishing pad is a thermoplastic polyurethane, a polymer glycol having a coagulation rate of preferably 0.1 to 1.5mol, more preferably 0.3 to 1.2mol, still more preferably 0.4 to 1.0mol, and yet more preferably 0.5 to 0.9mol is preferably used as the thermoplastic polyurethane. The average pore area of the porous polyurethane can be controlled to be 10-100 mu m by controlling the solidification speed of the high-molecular diol²The retention of the polishing slurry can be improved, and a polishing pad having excellent polishing stability can be obtained.

In the present invention, the solidification rate of the polymer diol can be measured by the method described in examples.

The porous thermoplastic polyurethane is preferably a porous body of thermoplastic polyurethane having a D hardness of preferably 35 to 90, more preferably 35 to 85, still more preferably 35 to 80, and yet more preferably 40 to 80.

In the present invention, the D hardness of the porous thermoplastic polyurethane can be measured by the method described in examples.

The D hardness of the porous thermoplastic polyurethane is preferably 35-90. This makes it possible to maintain high durability and appropriate pad followability. The porous thermoplastic polyurethane, which contains a high molecular weight diol having a solidification rate of preferably 0.1 to 1.5mol, more preferably 0.6 to 1.0mol, and has a D hardness of preferably 35 to 80, contributes to improvement of the retention of the polishing slurry by adjusting the hardness of the polishing pad and providing fine bubbles to the surface layer. Thus, pores formed during polishing are less likely to disappear, and as a result, the slurry retainability of the polishing pad is improved and the polishing rate is increased. When the D hardness of the thermoplastic polyurethane is 35 or more, the durability is improved, and melting and disappearance of formed bubbles during polishing can be suppressed. Thus, the slurry holding ability of the polishing pad is improved, and the polishing rate is increased. When the D hardness is 90 or less, the storage modulus during polishing does not become too high, the pad followability becomes good, and the polishing rate is improved.

The average pore area of the porous structure formed by using the porous thermoplastic polyurethane is preferably 10 to 100 μm in view of improving the slurry holding ability and maintaining the polishing rate at a high level². From this viewpoint, the average pore area of the porous structure is preferably 15 to 90 μm²More preferably 20 to 90 μm²More preferably 25 to 70 μm²More preferably 25 to 50 μm². Average pore area of 10 μm²In the above case, the porous structure of the surface layer of the polishing pad is not easily damaged during dressing, and the amount of slurry held during polishing can be maintained, so that the polishing rate is not lowered, and the polishing uniformity is easily maintained. On the other hand, 100 μm²In the following case, since the polishing debris is less likely to stay, the scratching property is improved.

In the present invention, the average pore area can be measured by the method described in examples.

Thermoplastic polyurethane (hereinafter, also simply referred to as "polyurethane" in some cases) forming the porous thermoplastic polyurethane will be described in detail. The method for producing the polyurethane is not particularly limited, and for example, the following methods are used: a method of reacting a high-molecular diol, an organic diisocyanate, and a chain extender at a given ratio in a good solvent; a method of melt polymerization in the substantial absence of a solvent; a prepolymer method or a one-shot method of a known urethanization reaction is utilized. Among them, a method of solution polymerization is particularly preferably used in view of manufacturing a polishing pad by impregnating nonwoven fabric with the solution. The solution polymerization is a method of mixing a high molecular diol, an organic diisocyanate, a chain extender, and an additive as needed at a predetermined ratio and carrying out a certain amount of reaction using a reaction vessel.

The polymer diol, the organic diisocyanate, and the chain extender, which are raw materials for the polymerization of polyurethane, will be described in detail.

Specific examples of the polymer diol include at least 1 selected from the group consisting of poly (ethylene adipate), poly (butylene adipate), polycaprolactone diol, poly (3-methyl-1, 5-pentanediol adipate), poly (hexanediol adipate), poly (3-methyl-1, 5-pentanediol terephthalate), poly (diethylene adipate), poly (azelaic adipate), poly (2-methyl-1, 8-octanediol-nonanediol adipate), polyethylene glycol, poly (diethylene glycol), poly (tetramethylene glycol) and polypropylene glycol, and among these, poly (butylene adipate), polycaprolactone diol, poly (hexanediol adipate), polyethylene glycol, polypropylene glycol are preferable from the viewpoint of forming a porous structure, Polytetramethylene glycol, more preferably polycaprolactone diol or polyhexamethylene adipate.

As the organic diisocyanate, any of the organic diisocyanates conventionally used in the production of usual thermoplastic polyurethanes can be used, and at least 1 selected from 4, 4' -diphenylmethane diisocyanate, 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, and isophorone diisocyanate can be used, or 2 or more in combination. Among them, 4' -diphenylmethane diisocyanate is preferable from the viewpoint of abrasion resistance and the like of the polishing pad obtained.

As the chain extender, any of the chain extenders conventionally used in the production of general polyurethanes can be used. The chain extender is preferably a low molecular weight compound having 2 or more active hydrogen atoms reactive with an isocyanate group in the molecule and having a molecular weight of 300 or less, and at least 1 kind of chain extender selected from ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, 1, 5-pentanediol, 1, 6-hexanediol, and cyclohexanedimethanol may be used alone or 2 or more kinds may be used in combination.

The polishing pad of the present embodiment preferably comprises a nonporous polymeric elastomer impregnated into a nonwoven fabric and a porous thermoplastic polyurethane having a D hardness of 35 to 90. From the viewpoint of the retention of the slurry and the suppression of clogging, the porous thermoplastic polyurethane preferably has a porous structure in the pore shape.

In the polishing pad of the present embodiment, the ratio of the mass of the nonporous polymer elastomer to the mass of the porous polymer elastomer (mass of the porous thermoplastic polyurethane) is 0.49 or less. When the ratio of the mass of the nonporous polymer elastomer to the mass of the porous polymer elastomer (mass of the porous thermoplastic polyurethane) exceeds 0.49, the amount of the porous thermoplastic polyurethane in the polishing pad decreases, the slurry retainability during polishing decreases, and the polishing rate decreases. In addition, the polishing pad also has a reduced hardness, and polishing uniformity tends to be reduced. In addition, from the viewpoint of increasing the hardness of the polishing pad, the lower limit of the mass ratio of the content of the non-porous polymeric elastomer to the content of the porous thermoplastic polyurethane is preferably 0.30 or more.

From these viewpoints, the ratio of the mass of the nonporous polymer elastomer to the mass of the porous polymer elastomer is preferably 0.35 or more, more preferably 0.38 or more, and is preferably 0.47 or less, more preferably 0.46 or less.

The apparent density of the polishing pad of the present embodiment is preferably 0.50 to 0.90g/cm³. When the apparent density falls within the above range, the rigidity and the volume of the communicating pores become appropriate, and therefore, the polishing composition is preferable in terms of suppressing scratches and also achieving a high polishing rate. From this viewpoint, it is more preferably 0.55 to 0.85g/cm³More preferably 0.58 to 0.80g/cm³More preferably 0.60 to 0.75g/cm³. When the apparent density is too low, the rigidity tends to be lowered, and thus the polishing rate tends to be lowered, and when the apparent density is too high, the volume of pores is reduced, and therefore, polishing debris and abrasive grains of the polishing slurry are difficult to be discharged, and the effect of suppressing scratches on the surface to be polished tends to be lowered.

In the present invention, the apparent density of the polishing pad can be measured by the method described in examples.

The C hardness of the polishing pad of the present embodiment is preferably 80 or more, and more preferably 85 or more. When the pad hardness is too low, the polishing pad becomes excessively soft, and the polishing rate and planarization performance are lowered. In addition, when the pad hardness is too high, the pad hardness becomes too hard, and the followability to the surface to be polished is lowered, so that the polishing rate is lowered, and further, there is a tendency that scratches are easily generated on the surface to be polished, and therefore, the upper limit of the C hardness of the polishing pad is preferably 95 or less.

In the present invention, the C hardness of the polishing pad can be measured by the method described in examples.

The method for manufacturing a polishing pad according to the present embodiment includes the steps of: a step of imparting an aqueous nonporous polymeric elastomer to a nonwoven fabric formed of ultrafine fiber-forming fibers; a step of forming ultrafine fibers into an ultrafine fiber nonwoven fabric by ultrafine-fibrillating the ultrafine fiber-forming fibers; and a step of impregnating a solvent-soluble polymer elastomer and wet-solidifying the impregnated polymer elastomer to give a porous polymer elastomer such that the ratio of the mass of the non-porous polymer elastomer to the mass of the porous polymer elastomer is 0.49 or less. By initially providing a smaller amount of the nonporous polymeric elastomer than the porous polymeric elastomer to the nonwoven fabric formed of the ultrafine fiber-forming fibers, the shape can be easily maintained at a low density after the next step, the impregnation of the porous thermoplastic polyurethane is improved, and the formation of the porous structure is facilitated.

The polishing pad of the present embodiment may be a polishing pad having a multilayer structure in which known cushion layers made of an elastomer sheet having a foam structure or a non-foam structure, a nonwoven fabric containing an elastomer, or the like are laminated, in order to impart cushion properties to the surface opposite to the polishing surface even when the polishing pad is formed as a single layer. The cushion layer may be laminated to the sheet using an adhesive or a bonding agent.

The thickness of the polishing pad is not particularly limited, but is preferably 0.8 to 3.5mm, more preferably 1.0 to 3.0 mm. From the viewpoint of polishing performance and pad life, it is preferably 1.2 to 2.5 mm.

When the mass of the nonwoven fabric constituting the polishing pad is Wa, the mass of the nonporous polymer elastomer is Wb, and the mass of the porous polymer elastomer is Wc, the ratio of the mass (Wa) of the nonwoven fabric constituting the polishing pad to the mass (Wa + Wb + Wc) of the entire polishing pad is preferably 0.600 or more. When the mass ratio is 0.600 or more, the hardness of the polishing pad can be improved. From this viewpoint, the mass ratio is preferably 0.630 or more, more preferably 0.640 or more, and preferably 0.700 or less.

It is also preferable that grooves or holes for holding the aqueous slurry be formed on the polishing surface of the polishing pad by grinding, laser processing, embossing, or the like as necessary.

The object to be polished by the polishing pad is not particularly limited, and examples thereof include a semiconductor substrate such as a silicon wafer, a glass substrate, a semiconductor device, a liquid crystal display, and the like. As the polishing method, a chemical mechanical polishing method (CMP) using a chemical mechanical polishing apparatus (CMP apparatus) and an aqueous slurry can be preferably used. Examples of CMP include: a method of polishing the surface of an object to be polished by applying a polishing pad to a polishing platen of a CMP apparatus, pressing the object to be polished against the polishing pad while supplying an aqueous slurry to the polishing surface, and rotating the polishing platen together with the object to be polished. Before and during polishing, it is preferable to adjust the polishing surface by using a diamond dresser, a nylon brush, or the like as needed to dress the polishing surface.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples at all.

First, the evaluation method used in this example will be described in summary below.

[ weight ratio of nonwoven Fabric of polyester fiber and weight ratio of nonporous Polymer elastomer ]

The mass (Wa) of the nonwoven fabric of polyester fibers, the mass (Wb) of the impregnated nonporous polymer elastomer (nonporous polyurethane), and the mass (Wc) of the impregnated porous thermoplastic polyurethane were determined based on the mass change in the production process of the polishing pad, and the mass ratio of the nonwoven fabric of polyester fibers in the polishing pad was determined from the formula Wa/(Wa + Wb + Wc). Further, the ratio of the mass of the nonporous polymer elastomer to the mass of the porous polymer elastomer (mass of the porous thermoplastic polyurethane) was determined from Wb/Wc.

[ measurement of solidification Rate of Polymer diol ]

A10 mass% DMF solution was prepared by dissolving a polymer diol in Dimethylformamide (DMF), and the solution was heated to 30 ℃. An aqueous solution of DMF at a concentration of 10% by mass was added dropwise to the heated DMF solution to make it cloudy. The coagulation rate was determined from the average value (average value obtained by performing the same operation 3 times) calculated from the sum of the dropping amounts of the DMF 10 mass% aqueous solution at the starting point and the ending point, with the state of white turbidity starting as the starting point and the state of complete white turbidity as the ending point.

[ average cell area of cellular thermoplastic polyurethane ]

An arbitrary cross section in the thickness direction of the obtained polishing pad was photographed at a magnification of 500 times using a scanning microscope (SEM). Then, the porous cross-sectional area of the thermoplastic polyurethane was binarized by image processing based on the obtained SEM photograph, and the average pore area was calculated.

[ measurement of hardness ]

Hardness was measured according to JIS K7311: 1995. Specifically, the thermoplastic polyurethane sheets obtained by hot press molding were laminated to a thickness of 6mm or more, the D hardness was determined from the average value of 10 points measured, and the C hardness was determined from the average value of 10 points measured by laminating polishing pads to a thickness of 6mm or more.

[ diameter of single fiber ]

The cross section of the polishing pad perpendicular to the thickness direction containing the fibers was observed at 1000 times using a scanning electron microscope, and the measurement result was taken as a single fiber diameter.

[ apparent Density ]

The apparent density of the polishing pad was determined according to JIS K7311: 1995.

[ polishing Rate (polishing speed) ]

The polishing rate of the resulting polishing pad was evaluated by the following method.

The resulting polishing pad was set on a CMP polishing apparatus ("MAT-BC 15" manufactured by MAT corporation). Then, a bare silicon wafer having a diameter of 4 inches was polished for 10 minutes while supplying a polishing slurry at a rate of 200 mL/min under conditions of a platen rotation speed of 100rpm, a head rotation speed of 99rpm, and a polishing pressure of 57 kPa. As the polishing slurry, a slurry prepared by diluting "Glanzox 1302" manufactured by Fujimi Incorporated by 20 times was used. Then, the bare silicon wafers were replaced and polishing was repeated in the same manner, and a total of 5 bare silicon wafers were polished. Then, the polishing rate was calculated from the difference in mass of the polished 5 bare silicon wafers before and after polishing. Then, the average value of the polishing rates of 5 bare silicon wafers was calculated.

[ example 1]

A strand of a sea-island type composite fiber comprising polyethylene terephthalate (PET) as an island component, water-soluble thermoplastic polyvinyl alcohol (PVA) as a sea component, a mass ratio of the sea component/island component of 25/75, and 25 islands as the number was spun at 265 ℃ from a die for melt composite spinning, and the strand was drawn, refined, and cooled. Then, the continuous collection and pressing were performed to obtain a long fiber web. Next, 2 long fiber nets were stacked, and both surfaces were alternately subjected to needling treatment to wrap the long fiber nets together, thereby obtaining a three-dimensional wrapped body.

Then, an aqueous emulsion of polycarbonate urethane (Tg: -27 ℃, storage modulus (23 ℃): 32.6MPa, storage modulus (50 ℃): 19.5MPa) as a nonporous polymer elastomer was impregnated into the three-dimensional cohesive body, and then the three-dimensional cohesive body was applied by impregnation and dried. This treatment corresponds to "a step of applying an aqueous nonporous polymeric elastomer to a nonwoven fabric formed of ultrafine fiber-forming fibers" in the production method of the present invention.

Then, the three-dimensional cohesive body was padded in hot water to dissolve and remove the water-soluble thermoplastic PVA of the island component from the sea-island type composite fiber, and the resultant was dried, thereby obtaining a nonwoven fabric formed of 25 bundles of PET fibers having an average single fiber fineness of 0.05dtex and a sheet having a thickness of 1.8mm in which nonporous polyurethane was provided. This treatment corresponds to "a step of forming ultrafine fibers into an ultrafine fiber nonwoven fabric by ultrafine-fibrillating an ultrafine fiber-forming fiber" in the production method of the present invention. The average single fiber diameter of the obtained nonwoven fabric was 3.0. mu.m.

[ Synthesis of cellular thermoplastic polyurethane ]

Polycaprolactone diol (PLACCEL 210, manufactured by Daiiol Co., Ltd.) as a polymer diol was put into a 2L glass flask and degassed at 80 ℃. After degassing, 1, 4-butanediol (manufactured by Tokyo Chemical Co., Ltd.) was added as a chain extender, and dimethylformamide (manufactured by FUJIFILM Wako Pure Chemical Co., Ltd.) was further added and stirred. After stirring, diphenylmethane diisocyanate (millionite MT manufactured by tokyo co) as an isocyanate was charged and heated and stirred, and the reaction was carried out while confirming the increase in viscosity. Diphenylmethane diisocyanate was gradually charged and stirred so that the liquid viscosity became 1500mPa · s from 500mPa · s. After the liquid viscosity was measured, it was cooled at room temperature to obtain a thermoplastic polyurethane. Table 1 shows the composition and hardness of the thermoplastic polyurethane.

[ impregnation of porous thermoplastic polyurethane ]

A sheet comprising the obtained PET nonwoven fabric and non-porous polyurethane was cut into 380 mm. times.380 mm. Then, the cut pieces were impregnated with a porous thermoplastic polyurethane having a D hardness of 80. Table 1 shows the composition and hardness of the cellular thermoplastic polyurethane.

Impregnation was performed as follows. The thermoplastic polyurethane 25% strength DMF solution was heated to 30 ℃. The above sheet was allowed to stand thereon for 10 minutes to allow the DMF solution to permeate. Further, the solution was allowed to sink in DMF for 5 minutes. Next, the sheet was taken out, placed on a glass plate, and the surface of the sheet was lightly scratched with a spatula to remove the adhering DMF solution. The same operation was performed for the back surface.

Next, the raw material permeated with the DMF solution was immersed in a 10% DMF concentration aqueous solution maintained at 30 ℃ and left for 30 minutes, thereby solidifying the porous thermoplastic polyurethane. Then, the sheet obtained by solidifying the porous thermoplastic polyurethane and impregnating the sheet is immersed in hot water at 70 to 95 ℃, sandwiched between metal rolls, squeezed to obtain water, and then again immersed in hot water and washed with water. Then, the water-washed raw material was put into a hot air dryer (device name: Safety Ovens SPH-202/ESPEC Co.) and dried at 100 ℃ for 40 minutes. Thus, a raw material of the polishing pad (referred to as a pad raw material intermediate) was obtained. This treatment corresponds to "a step of impregnating a solvent-containing polymer elastomer and wet-coagulating the solvent-containing polymer elastomer to impart the porous polymer elastomer so that the ratio of the mass of the non-porous polymer elastomer to the mass of the porous polymer elastomer is 0.49 or less" in the production method of the present invention.

[ planarization and groove processing of pad raw material intermediate ]

The surface of the pad material intermediate was polished with sandpaper (model #180) to eliminate thickness unevenness and flatten the surface, thereby producing a polishing pad. Then, an adhesive tape is stuck to the polished surface. Then, lattice grooves having a groove width of 2.0mm, a groove depth of 0.5mm and a pitch of 15mm were formed on the polishing surface of the polishing pad by a flattening groove processing machine. Then, a polishing pad with grooves obtained by cutting the polishing pad formed with the lattice grooves into a circular shape having a diameter of 370mm was obtained. Then, evaluation was performed by the above-described evaluation method. The results are shown in Table 1.

[ example 2]

A polishing pad with grooves was produced in the same manner as in example 1 except that polycaprolactone diol was changed to polyhexamethylene adipate in [ synthesis of porous thermoplastic polyurethane ] of example 1, and evaluated in the same manner as in example 1. The results are shown in Table 1.

TABLE 1

Comparative example 1

A thermoplastic polyurethane produced using polycaprolactone diol (PLACCEL 210 manufactured by xylonite, ltd.) as a polymer diol, 1, 4-butanediol (manufactured by tokyo chemical industry co., ltd.) as a chain extender, and diphenylmethane diisocyanate (millrinate MT manufactured by tokyo co., ltd.) as an isocyanate was obtained in the same manner as the thermoplastic polyurethane described in example 1, and a polishing pad was obtained by further using a DMF solution having a thermoplastic polyurethane concentration of 25% for impregnation. Then, evaluation was performed by the above-described evaluation method. The results are shown in Table 1.

As shown in table 1, the polishing pad of example 1 had an increased polishing rate by controlling the mass ratio of each component of the nonporous polymer elastomer and the porous polymer elastomer, that is, by increasing the amount of the porous polymer elastomer. On the other hand, in the case of comparative example 1, since the porous polymer elastomer of the polishing pad was small, the groove shape was damaged during polishing, and the polishing rate was lowered.

Industrial applicability

The polishing pad of the present invention can be suitably used for polishing in the production processes of various semiconductor devices, bare silicon, Micro Electro Mechanical Systems (MEMS), SiC semiconductors, and the like.

Claims

1. A polishing pad obtained by impregnating a nonwoven fabric with a nonporous polymer elastomer and a porous polymer elastomer,

the porous polymer elastomer contains thermoplastic polyurethane, and the ratio of the mass of the nonporous polymer elastomer to the mass of the porous polymer elastomer is 0.49 or less.

2. The polishing pad according to claim 1, having an average pore area of the porous polymer elastomer of 10 to 100 μm²The porous structure of (3).

3. The polishing pad according to claim 1 or 2, wherein a solidification rate of the polymer diol forming the thermoplastic polyurethane contained in the porous polymer elastomer is 0.1 to 1.5 mol.

4. The polishing pad according to any one of claims 1 to 3, wherein the D hardness of the thermoplastic polyurethane contained in the porous polymer elastomer is 35 to 85.

5. The polishing pad according to any one of claims 1 to 4, wherein the fibers constituting the nonwoven fabric are polyester fibers having an average single fiber diameter of 1 to 10 μm.

6. The polishing pad according to any one of claims 1 to 5, wherein the thermoplastic polyurethane contained in the porous polymer elastomer comprises a thermoplastic polyurethane obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender,

the high molecular diol comprises at least 1 selected from polyethylene glycol adipate, polybutylene adipate, polycaprolactone diol, 3-methyl-1, 5-pentanediol adipate, polyhexamethylene adipate, 3-methyl-1, 5-pentanediol terephthalate, polyethylene glycol adipate, poly (azelaic adipate), 2-methyl-1, 8-octanediol adipate, polyethylene glycol, polytetramethylene glycol and polypropylene glycol,

the organic diisocyanate comprises at least 1 selected from 4, 4' -diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, isophorone diisocyanate,

the chain extender comprises at least 1 selected from ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, 1, 5-pentanediol, 1, 6-hexanediol, cyclohexanedimethanol.

7. The polishing pad of any one of claims 1 to 6, wherein the apparent density of the polishing pad is 0.50 to 0.90g/cm³。

8. The polishing pad of any one of claims 1 to 7, wherein the C hardness of the polishing pad is 80 or more.

9. A method of manufacturing a polishing pad, the method comprising sequentially performing the steps of:

a step of imparting an aqueous nonporous polymeric elastomer to a nonwoven fabric formed of ultrafine fiber-forming fibers;

a step of forming ultrafine fibers into an ultrafine fiber nonwoven fabric by ultrafine-fibrillating the ultrafine fiber-forming fibers;

and a step of impregnating a solvent-soluble polymer elastomer and wet-solidifying the impregnated polymer elastomer to give a porous polymer elastomer such that the ratio of the mass of the non-porous polymer elastomer to the mass of the porous polymer elastomer is 0.49 or less.