JPWO2020138198A1 - Abrasive pad - Google Patents

Abstract

Providing a polishing pad with a high polishing rate in a non-woven fabric type polishing pad that has excellent polishing stability and smoothness of the object to be polished and has a feature that the change in polishing performance is small even if polishing is continued for a long time. do. A polishing pad in which a non-porous polymer elastic body is impregnated with a non-porous polymer elastic body, and the porous polymer elastic body contains thermoplastic polyurethane, with respect to the mass of the porous polymer elastic body. A polishing pad having a mass ratio of the non-porous polymer elastic body of 0.49 or less.

Description

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

Chemical mechanical polishing (CMP) is known as a mirror surface processing of a semiconductor wafer used as a base material for forming an integrated circuit. As the polishing pad used for CMP, a non-woven fabric type sheet obtained by impregnating a non-woven fabric with wet-solidified polyurethane or a wet polyurethane having a wet-solidified polyurethane resin on the upper layer of a film or fiber structure is arranged on the surface layer (wet polyurethane). PU) A sponge type sheet or a molded sheet of a polymer elastic body such as polyurethane having a closed cell structure is used. Non-woven fabric type sheets and wet PU sponge types are relatively soft because they are easily compressed and deformed, while polymer elastic molded sheets have high rigidity.

In recent years, with the increasing integration and multi-layer wiring of semiconductor wafers and semiconductor devices, there is an increasing demand for quality improvement such as higher flattening and lower price. Attempts have been made to use copper alloys as wiring materials in place of conventional aluminum alloys, _{and low dielectric constant materials as insulating materials in place of conventional SiO 2.} With such changes in materials, it is possible to flatten the polishing pad more than before, reduce scratches on the wafer surface, increase the polishing rate, improve the stability in polishing, and use it for a long time. Further enhancement of functionality such as being possible is required. In addition, silicon wafers, liquid crystal displays, hard disks, glass lenses, etc. are also being highly integrated and highly accurate, so polishing pads can be flattened more than before, and surface scratches can be achieved. It is required to further improve the functionality such as reducing the number of wafers, increasing the polishing rate, improving the stability in polishing, and being able to use it for a long time.

The foamed polyurethane used for the polishing pad of the molded sheet is generally manufactured by casting foam curing using a two-component curable polyurethane (see, for example, Patent Documents 1 to 4). However, with these methods, it is difficult to make the reaction and foam uniform, and there is a limit to the hardness of the obtained polyurethane foam, so the polishing characteristics such as the flatness and flattening efficiency of the surface to be polished vary. Furthermore, since the foamed structure is an independent hole, the polishing slurry and polishing debris used in the polishing process invade the voids and are easily clogged, resulting in a decrease in the polishing rate (polishing speed). There was a problem such as short pad life. Therefore, the above-mentioned required performance (further improvement of flattening efficiency, reduction of scratches on the wafer surface, improvement of polishing rate, stability in polishing, improvement of polishing pad life, etc.) is fully satisfied. No polishing pad using a molded sheet made of foamed polyurethane has been obtained.
Therefore, especially for materials that are easily scratched, such as copper wiring and low dielectric constant materials, and materials that have weak interface adhesion, scratches and interface peeling are more likely to occur, and new polishing pads that can deal with these problems. Development is required.

On the other hand, the non-woven fabric type polishing pad generally has a concavo-convex structure due to fibers on the surface, and has voids and communication hole structures due to the structure of the non-woven fabric. Therefore, features such as good slurry retention during polishing (hereinafter, also referred to as slurry retention) and easy increase in polishing rate, good cushioning, flexibility, and good contact with wafers. It is used in various polishing fields. However, the conventional non-woven fabric type polishing pad does not have sufficient ability to flatten due to the large number of voids and flexibility, and the stability in polishing and the life of the polishing pad are not sufficient. Therefore, various studies have been made for improving the performance (see, for example, Patent Documents 6 to 14).
However, in each case, there are the following problems. That is, (1) the diameter of the fiber is about several tens of μm, and the unevenness of the surface of the polishing pad caused by the fiber is relatively huge with respect to the step of the wafer, so that there is a limit to the improvement of flatness and the fiber is ground. When grains agglomerate, it tends to cause scratches. Further, when ultrafine fibers are used, the sheet made of ultrafine fibers has a very soft property, so that the hardness is insufficient, or when the hardness is increased by using a very hard polymer elastic body, the hardness is high. The hardness and brittleness of the molecular elastic body make it easy for the wafer to be scratched. (2) Since the density of the fibers of the non-woven fabric is low, the number of naps on the surface (density of the uneven structure) due to the fibers is small, and the effect of combining the fibers with the polymer elastic body is not sufficient. (3) Since the density of the sheet is low and there are many voids, it is difficult to obtain a sheet with high hardness, and since there are inhomogeneous huge non-woven fabric voids on the order of several hundred μm on the surface, there is a limit to the improvement of flatness. Furthermore, the performance such as hardness tends to change with time during polishing, which causes problems in polishing stability and the life of the polishing pad. (4) When the polymer elastic body is completely filled to eliminate the voids in the nonwoven fabric, the surface irregularities formed by the fibers and the features caused by the voids in the nonwoven fabric structure and the communication hole structure are lost.

Therefore, the performance required from the market (further improvement of flattening efficiency, reduction of scratches on the wafer surface, improvement of polishing rate, stability in polishing, improvement of life of polishing pad, etc.) is fully satisfied. Non-woven type polishing pads have not yet been found.

Japanese Unexamined Patent Publication No. 2000-178374 Japanese Unexamined Patent Publication No. 2000-248034 Japanese Unexamined Patent Publication No. 2001-89548 Japanese Unexamined Patent Publication No. 11-322878 Japanese Unexamined Patent Publication No. 2002-9026 Japanese Unexamined Patent Publication No. 11-99479 Japanese Unexamined Patent Publication No. 2005-212055 Japanese Unexamined Patent Publication No. 3-234475 Japanese Unexamined Patent Publication No. 10-1289797 Japanese Unexamined Patent Publication No. 2004-311731 Japanese Unexamined Patent Publication No. 10-225864 Japanese Patent Publication No. 2005-518286 Japanese Patent Application Laid-Open No. 2003-201676 Japanese Unexamined Patent Publication No. 2005-334997

INDUSTRIAL APPLICABILITY The present invention is a non-woven fabric type polishing pad having excellent polishing performance in polishing stability and smoothness of an object to be polished, and having a feature that the change in polishing performance is small even if polishing is continued for a long time, and the polishing rate is high. It is intended to provide a polishing pad.

One aspect of the present invention is a polishing pad in which a non-porous polymer elastic body and a porous polymer elastic body are impregnated into a non-porous polymer elastic body, and the porous polymer elastic body contains thermoplastic polyurethane, and the porous polymer elastic body is contained. The polishing pad is characterized in that the ratio of the mass of the non-porous polymer elastic body to the mass of the polymer elastic body is 0.49 or less.

Further, a polishing pad having a porous structure in which the average pore area of the porous polymer elastic body is 10 to 100 μm ^{2 is preferable.} Further, a polishing pad having a coagulation rate of 0.1 to 1.5 mol of the polymer diol forming the thermoplastic polyurethane contained in the porous polymer elastic body is preferable, and heat contained in the porous polymer elastic body is preferable. A polishing pad having a D hardness of plastic polyurethane of 35 to 85 is preferable.

Further, the fibers constituting the non-woven fabric are polyester fibers, and a polishing pad having an average single fiber diameter of 1 to 10 μm is preferable.

According to such a configuration, in a non-woven fabric type polishing pad, which has excellent polishing performance in polishing stability and smoothness of the object to be polished, and has a feature that the change in polishing performance is small even if polishing is continued for a long time. A polishing pad with a high polishing rate can be obtained.

Further, the porous thermoplastic polyurethane contains a thermoplastic polyurethane obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender, and the polymer diol is poly (ethylene adipate) or poly (butylene adipate). , Poly (caprolactone diol), poly (3-methyl-1,5-pentamethylene adipate), poly (hexamethylene adipate), poly (3-methyl-1,5-pentamethylene terephthalate), poly (diethylene glycol adipate), Poly (nonamethylene adipate), poly (2-methyl-1,8-octamethylene adipate), poly (2-methyl-1,8-octamethylene-co-nonamethylene adipate), poly (ethylene glycol), poly ( It contains at least one selected from the group consisting of diethylene glycol), poly (tetramethylene glycol), and poly (propylene glycol), and the organic diisocyanate is 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6. -Contains at least one selected from the group consisting of toluene diisocyanate and isophorone diisocyanate, and the chain extender is ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentane. It is preferable to contain at least one selected from the group consisting of diols, 1,6-hexanediols and cyclohexanedimethanol.

The apparent density of the polishing pad is preferably ^{0.50 to 0.90 g / cm 3.}

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

Further, the present invention relates to a step of imparting a water-based non-porous polymer elastic body to a non-woven fabric made of ultrafine fiber-generating fibers, a step of converting ultrafine fiber-generating fibers into ultrafine fibers to form an ultrafine fiber non-woven fabric, and a high solvent-based method. The molecular elastic body is impregnated and wet-solidified, and the porous polymer elastic body is imparted so that the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body is 0.49 or less. It is a method for manufacturing a polishing pad, characterized in that the steps are sequentially performed.

According to the present invention, in a non-woven fabric type polishing pad, a polishing pad having a high polishing rate can be obtained.

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

The polishing pad of the present embodiment is a polishing pad in which a non-porous polymer elastic body and a porous polymer elastic body are impregnated into a non-porous polymer elastic body, and the porous polymer elastic body contains thermoplastic polyurethane, and the porous polymer elastic body is contained. The polishing pad is characterized in that the ratio of the mass of the non-porous polymer elastic body to the mass of the quality polymer elastic body is 0.49 or less.
In the present invention, the non-porous polymer elastic body is impregnated with the porous polymer elastic body, and the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body is determined. Since it is adjusted to 0.49 or less, the change in polishing performance is small even if polishing is continued for a long time, and the polishing rate can be increased.
In the present invention, the non-porous polymer elastic body means a substance having substantially no pores, specifically, ^{a substance having a pore area of less than 10 μm 2 in} the measurement of the average pore area described later, and is referred to as a porous polymer elastic body. ^{Refers to a molecule of 10 μm 2} or more in the measurement of the average pore area described later.

The non-woven fabric is not particularly limited as long as it is a non-woven fabric of fibers containing a polyester resin as a main component, such as nylon, polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). In particular, when the non-woven fabric is made of polyester fiber, the storage elastic modulus E'is less likely to fluctuate because water is not easily absorbed during polishing, and the polishing efficiency is stable. For example, in the case of a fiber having high water absorption such as nylon fiber, the storage elastic modulus E'varies due to the high water absorption rate during polishing, the polishing pad is easily deformed, and the polishing efficiency is lowered. It will be easier.

The average single fiber diameter of the polyester fiber is preferably 1 to 10 μm, more preferably 1.5 to 8.5 μm. When the average single fiber diameter is 1 μm or more, the fibers are less likely to break during dressing, which is preferable. Further, when the average single fiber diameter is 10 μm or less, the load on the polishing target can be suppressed low, so that the occurrence of scratches can be reduced.
Further, as a method for obtaining ultrafine fibers having an average single fiber diameter, a known method for converting ultrafine fiber-generating fibers into ultrafine fibers is used. From the viewpoint of environmental friendliness, the ultrafine fiber-generating fiber is preferably composed of a water-soluble polymer component and a poorly water-soluble polymer component. The water-soluble polymer component indicates a component from which the component is extracted and removed by an aqueous solution, and the poorly water-soluble polymer component is represented by a component whose component is difficult to be extracted and removed by an aqueous solution, that is, the above-mentioned nylon. A polyester resin represented by a polyamide resin or a polyethylene terephthalate is shown. The ultrafine fiber-generating fiber composed of a water-soluble polymer component and a water-insoluble polymer component is such as a sea-island type composite fiber, a mixed spinning type fiber, etc., as long as at least one component is extracted and removed by an extraction treatment with an aqueous solution. Any of the multi-component composite fibers may be used.
As the water-soluble polymer component used in the present invention, a known polymer can be used as long as it is a polymer that can be extracted with an aqueous solution, but polyvinyl alcohol copolymers that can be dissolved in an aqueous solution (hereinafter referred to as "PVA"). It may be abbreviated). PVA can be easily dissolved and removed with hot water, and structural crimping occurs in the ultrafine fiber-generating fibers, which are ultrafine fiber components, due to the shrinkage behavior when extracting and removing with an aqueous solvent, making the non-woven fabric bulky and dense. In addition, there is no limitation on the thermoplastic resin and polymer elastic component used for the ultrafine fiber component because the decomposition reaction of the ultrafine fiber component and the polymer elastic component does not substantially occur during the extraction process. It is preferably used because it is environmentally friendly.

The polishing pad of the present embodiment preferably contains a non-porous polymer elastic body impregnated with a non-woven fabric of polyester fibers and a porous thermoplastic polyurethane having a D hardness of 35 to 85.
Non-porous polymer elastic material is mainly used to maintain morphological stability in the manufacturing process of non-woven fabric. Further, the porous thermoplastic polyurethane having a D hardness of 35 to 85 improves the retention of the polishing slurry during CMP polishing by adjusting the hardness of the polishing pad and imparting fine bubbles to the surface layer. Contribute to. The non-porous polymer elastic body can be imparted, for example, by impregnating a non-woven fabric with an emulsion of the non-porous polymer elastic body and drying it. Further, the porous thermoplastic polyurethane can be imparted by impregnating the nonwoven fabric with a solution of the thermoplastic polyurethane that forms the porous thermoplastic polyurethane and then wet-coagulating it.

Specific examples of the non-porous polymer elastic body include non-porous polymer elastic materials such as polyurethane, acrylonitrile elastomer, olefin elastomer, polyester elastomer, polyamide elastomer, and acrylic elastomer. Of these, polyurethane is preferred.

As the non-porous polymer elastic body, it is preferable to use water-based non-porous polymer elasticity, and for example, non-porous polyurethane is preferably formed by using an aqueous emulsion. Specific examples of the water-based polyurethane emulsion include a polycarbonate-based polyurethane, a polyester-based polyurethane, a polyether-based polyurethane, and a polycarbonate / ether-based polyurethane water-based emulsion.

The non-porous polymer elastic body has a glass transition temperature of −10 ° C. or lower, and the storage elastic modulus at 23 ° C. and 50 ° C. is preferably 1 to 40 MPa, more preferably 1 to 35 MPa, and at 50 ° C. Polyurethane having a water absorption rate of 0.2 to 5% by mass when saturated water absorption is preferable is preferable. When the storage elastic modulus at 23 ° C. and 50 ° C. is at least the above lower limit value, the polishing pad is less likely to be deformed, which is preferable. Further, when the storage elastic modulus is not more than the upper limit value, it does not become too hard, so that the occurrence of scratches can be suppressed. Further, when the water absorption rate is too low, the amount of slurry retained during polishing tends to be small, and the polishing uniformity tends to decrease. Further, when the water absorption rate is too high, characteristics such as hardness tend to change during polishing, and polishing stability tends to decrease.

When the porous polymer elastic body contained in the polishing pad is thermoplastic polyurethane, the thermoplastic polyurethane has a solidification rate of preferably 0.1 to 1.5 mol, more preferably 0.3 to 1.2 mol, and further. It is preferable to use a polymer diol which is preferably 0.4 to 1.0 mol, more preferably 0.5 to 0.9 mol. By controlling the solidification rate of the polymer diol, the average pore area of the porous polyurethane ^{can be controlled to 10 to 100 μm 2} , the retention of the polishing slurry can be improved, and the polishing pad with excellent polishing stability. Is obtained.
In the present invention, the coagulation rate of the polymer diol can be measured by the method described in Examples.
Further, the porous thermoplastic polyurethane may be 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 even more preferably 40 to 80. preferable.
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 to 90. As a result, high durability can be maintained and appropriate pad followability can be maintained. Further, the porous thermoplastic polyurethane having a solidification rate of preferably 0.1 to 1.5 mol, more preferably 0.6 to 1.0 mol, and having a D hardness of preferably 35 to 80 is polished. By adjusting the hardness of the pad and imparting fine bubbles to the surface layer, it contributes to improving the retention of the polishing slurry. As a result, the pores formed during polishing are less likely to disappear, and as a result, the slurry holding power 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 the formed bubbles are prevented from melting and disappearing during polishing. As a result, the slurry holding power of the polishing pad is improved and the polishing rate is increased. Further, when the D hardness is 90 or less, the storage elastic modulus during polishing does not become too high, the pad followability is improved, and the polishing rate is improved.

It is preferable that the average pore area of the porous structure formed by using the porous thermoplastic polyurethane is 10 to 100 μm ² from the viewpoint that the slurry holding power can be improved and the polishing rate can be maintained high. In this respect, the average pore area of the porous structure is preferably 15 to 90 m ^2, more preferably 20～90Myuemu ^2, more preferably 25～70Myuemu ^2, even more preferably 25 to 50 m ^2. When the average pore area is 10 μm ² or more, the porous structure of the surface layer of the polishing pad is less likely to be damaged during dressing, and the amount of slurry retained during polishing can be maintained, so that the polishing rate does not decrease and the polishing uniformity is maintained. It will be easier. On the other hand, when ^{it is 100 μm 2} or less, the polishing debris is less likely to stay, so that the scratch property is improved.
In the present invention, the average pore area can be measured by the method described in Examples.

The thermoplastic polyurethane (hereinafter, may be simply referred to as “polyurethane”) that forms the porous thermoplastic polyurethane will be described in detail. The method for producing polyurethane is not particularly limited, and for example, a method of reacting a polymer diol, an organic diisocyanate and a chain extender at a predetermined ratio in a good solvent, a method of melt-polymerizing in the absence of a solvent, and the like. , A prepolymer method or a one-shot method using a known urethanization reaction is used. Among these, a method of impregnating a non-woven fabric and polymerizing the polishing pad in a solution from the viewpoint of production is particularly preferably used. Solution polymerization is a method in which a polymer diol, an organic diisocyanate, a chain extender, and an additive to be blended as necessary are blended in a predetermined ratio and reacted in a fixed amount using a reaction vessel.

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

Specific examples of the high molecular weight diol include poly (ethylene adipate), poly (butylene adipate), poly (caprolactone diol), poly (3-methyl-1,5-pentamethylene adipate), and poly (hexamethylene adipate). , Poly (3-methyl-1,5-pentamethylene terephthalate), Poly (diethylene glycol adipate), Poly (nonamethylene adipate), Poly (2-methyl-1,8-octamethylene adipate), Poly (2-methyl- It is at least one selected from the group consisting of 1,8-octamethylene-co-nonamethylene adipate), poly (ethylene glycol), poly (diethylene glycol), poly (tetramethylene glycol), and poly (propylene glycol). Among them, poly (butylene adipate), poly (caprolactone diol), poly (hexamethylene adipate), poly (ethylene glycol), and poly (tetramethylene glycol) are preferable. Further, poly (caprolactone diol) and poly (hexamethylene adipate) are preferable in terms of forming a porous structure.

As the organic diisocyanate, any of the organic diisocyanates conventionally used in the production of ordinary thermoplastic polyurethane may be used, and 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6- It is at least one selected from the group consisting of toluene diisocyanate and isophorone diisocyanate, and two or more thereof may be used in combination. Among these, 4,4'-diphenylmethane diisocyanate is preferable from the viewpoint of wear resistance of the obtained polishing pad.

As the chain extender, any of the chain extenders conventionally used in the production of ordinary polyurethane may be used. As the chain extender, it is preferable to use a low molecular weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group and having a molecular weight of 300 or less, such as ethylene glycol, 1,3-propanediol, and 1,4. -At least one chain extender selected from the group consisting of butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol may be used alone or two kinds. The above may be used together.

The polishing pad of the present embodiment preferably contains a non-porous polymer elastic body impregnated with a non-woven fabric and a porous thermoplastic polyurethane having a D hardness of 35 to 90. The shape of the pores of the porous thermoplastic polyurethane is preferably a porous structure in terms of slurry retention and clogging suppression.
Further, in the polishing pad of the present embodiment, the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body (mass of the porous thermoplastic polyurethane) is 0.49 or less. When the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body (mass of the porous thermoplastic polyurethane) exceeds 0.49, the amount of the porous thermoplastic polyurethane in the polishing pad is small. Therefore, the slurry retention during polishing is lowered and the polishing rate is lowered. Further, the hardness of the polishing pad is also lowered, and the polishing uniformity tends to be lowered. Further, it is preferable that the lower limit of the mass ratio of the content of the non-porous polymer elastic body to the content of the porous thermoplastic polyurethane is 0.30 or more in terms of increasing the hardness of the polishing pad.
From these viewpoints, the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body is preferably 0.35 or more, more preferably 0.38 or more, and , 0.47 or less, more preferably 0.46 or less.

The polishing pad of the present embodiment preferably has an apparent density of 0.50 to 0.90 g / cm ³ . When the range of the apparent density is within the above range, the rigidity and the volume of the communication hole become appropriate, so that a high polishing rate can be obtained while suppressing scratches, which is preferable. In this respect, more preferably a 0.55~0.85g / cm ^3, more preferably 0.58~0.80g / cm ^3, in 0.60~0.75g / cm ³ It is more preferable to have. If the apparent density is too low, the rigidity tends to be low and the polishing rate tends to be low. If the apparent density is too high, the volume of the pores is reduced and polishing debris and abrasive grains of the polishing slurry are discharged. It becomes difficult and tends to reduce the scratch suppressing effect on the surface to be polished.
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, more preferably 85 or more. If the pad hardness is too low, the polishing pad becomes too soft and the polishing rate and flattening performance deteriorate. Further, if the pad hardness is too high, the pad becomes too hard and the followability to the surface to be polished is lowered, so that the polishing rate is lowered and the surface to be polished tends to be scratched. 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.

Further, the method for manufacturing the polishing pad of the present embodiment is a step of imparting a non-porous polymer elastic body to a non-porous fiber made of ultrafine fiber generating fiber, and a step of converting the ultrafine fiber generating fiber into ultrafine fiber to form an ultrafine fiber non-woven fabric. , Impregnated with a solvent-based polymer elastic body and wet-solidified, and the porosity is high so that the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body is 0.49 or less. It is a method for manufacturing a polishing pad, which comprises sequentially performing a step of applying a molecular elastic body. By first applying a non-porous polymer elastic body to the non-woven fabric made of ultrafine fiber-generating fibers in a smaller amount than the porous polymer elastic body, the shape can be easily maintained in the next step and thereafter at a low density, and further, the porous heat can be maintained. The impregnation property of the plastic polyurethane is improved, and further, the formation of a porous structure becomes easy.

Even as a single-layer polishing pad, the polishing pad of the present embodiment is impregnated with an elastomer sheet or elastomer having a foamed structure or a non-foamed structure in order to impart cushioning properties to the surface opposite to the polished surface. It may be used as a polishing pad having a multi-layer structure such that a known cushion layer made of a non-woven fabric or the like is laminated. The cushion layer is laminated on the sheet using an adhesive or an adhesive.

The thickness of the polishing pad is not particularly limited, but is preferably 0.8 to 3.5 mm, more preferably 1.0 to 3.0 mm, and more preferably 1.2 to 2.5 mm for polishing. Preferred from the standpoint of performance and pad life.
When the mass of the non-woven fabric constituting the polishing pad is Wa, the mass of the non-porous polymer elastic body is Wb, and the mass of the porous polymer elastic body is Wc, the polishing is performed with respect to the mass of the entire polishing pad (Wa + Wb + Wc). The ratio of the mass (Wa) of the non-woven fabric constituting the 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.

Further, it is preferable to form grooves and holes on the polished surface of the polishing pad to hold the aqueous slurry by grinding, laser processing, embossing or the like, if necessary.

The polishing target of 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, and a liquid crystal display. As a polishing method, a chemical mechanical polishing apparatus (CMP apparatus) and a chemical mechanical polishing method (CMP) using an aqueous slurry are preferably used. As the CMP, for example, a polishing pad is attached to the polishing platen of the CMP device, and while supplying an aqueous slurry to the polishing surface, pressure is applied while pressing the object to be polished against the polishing pad to press the polishing platen and the object to be polished. A method of polishing the surface of the object to be polished by rotating them together can be mentioned. Before or during polishing, it is preferable to condition and prepare the polished surface using a dresser such as a diamond dresser or a nylon brush, if necessary.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

First, the evaluation methods used in this example will be summarized below.

[Mass ratio of non-woven fabric of polyester fiber, mass ratio of non-porous polymer elastic body]
Based on the mass change in the manufacturing process of the polishing pad, the mass (Wa) of the non-woven fabric of polyester fiber, the mass (Wb) of the impregnated non-porous thermoplastic elastic material (non-porous polyurethane), and the impregnated porous heat. The mass (Wc) of the plastic polyurethane was determined, and the mass ratio of the non-woven fabric of the polyester fiber in the polishing pad was determined from the formula of Wa / (Wa + Wb + Wc). Further, the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body (mass of the porous thermoplastic polyurethane) was obtained from Wb / Wc.

[Measurement of solidification rate of polymer diol]
The high molecular weight diol was dissolved in dimethylformamide (DMF) to prepare a 10% by mass DMF solution, which was heated to 30 ° C. A 10% by mass aqueous solution of DMF was added dropwise to the heated DMF solution to make it cloudy. Coagulation rate from the average value calculated from the sum of the dropping amounts of the DMF 10% by mass concentration aqueous solution (the average value obtained by performing the same operation three times) with the start point of the white turbidity as the start point and the end point of the completely cloudy state as the end point. Asked.

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

[Hardness measurement]
Hardness measurement was performed according to JIS K 7311: 1995. Specifically, the D hardness was obtained from the average value of 10 points measured by stacking thermoplastic polyurethane sheets obtained by hot press molding so as to have a thickness of 6 mm or more, and the polishing pads were stacked so as to have a thickness of 6 mm or more. The C hardness was obtained from the average value of the measured 10 points.

[Single fiber diameter]
A cross section perpendicular to the thickness direction including the fibers of the polishing pad 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 K 7311: 1995.

[Polishing rate (polishing speed)]
The polishing rate of the obtained polishing pad was evaluated by the following method.
The obtained polishing pad was installed in a CMP polishing apparatus (“MAT-BC15” manufactured by MAT Co., Ltd.). Then, under the conditions of a platen rotation speed of 100 rpm, a head rotation speed of 99 rpm, and a polishing pressure of 57 kPa, 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. As the polishing slurry, a slurry prepared by diluting "Glanzox 1302" manufactured by Fujimi Incorporated Co., Ltd. in a 20-fold ratio was used. After that, the bare silicon wafers were replaced and polishing was repeated in the same manner to polish a total of five bare silicon wafers. Then, the polishing rate was calculated from the mass difference between the five polished bare silicon wafers before and after polishing. Then, the average value of the polishing rates of the five bare silicon wafers was calculated.

[Example 1]
265 sea-island type composite fiber strands with 25 islands containing polyethylene terephthalate (PET) as an island component and water-soluble thermoplastic polyvinyl alcohol (PVA) as a sea component and having a mass ratio of sea component / island component of 25/75. A sea-island type composite fiber was spun by discharging from a melt composite spinning mouthpiece at ° C., stretching the fiber, and cooling the fiber while refining the fiber. Then, a long fiber web was obtained by continuously collecting and pressing. Next, two long fiber webs were superposed, and needle punching treatment was alternately performed on both sides to entangle the long fiber webs with each other to obtain a three-dimensional entangled body.
Next, as a non-porous polymer elastic body, an aqueous emulsion having a polycarbonate polyurethane (Tg: −27 ° C., storage elastic modulus (23 ° C.): 32.6 MPa, storage elastic modulus (50 ° C.): 19.5 MPa) was used. It was impregnated by dip-niping into a three-dimensional entangled body and dried. It should be noted that this treatment corresponds to the "step of imparting a water-based non-porous polymer elastic body to a nonwoven fabric made of ultrafine fiber-generating fibers" in the production method of the present invention.
Then, by dipping niping the three-dimensional entangled fabric in hot water, the water-soluble thermoplastic PVA of the island component is dissolved and removed from the sea-island type composite fiber, and by drying, 25 bundles of PET having an average single fiber fineness of 0.05 dtex are obtained. A non-woven fabric made of fibers and a sheet having a thickness of 1.8 mm to which non-porous polyurethane was added were obtained. It should be noted that this treatment corresponds to the "step of converting ultrafine fiber generation type fibers into ultrafine fibers to form an ultrafine fiber non-woven fabric" in the production method of the present invention. The average single fiber diameter of the obtained nonwoven fabric was 3.0 μm.

[Synthesis of porous thermoplastic polyurethane]
Polycaprolactone diol (Plaxel 210 manufactured by Daicel Corporation), which is a high molecular weight diol, was placed in a 2 L glass flask and degassed at 80 ° C. After degassing, 1,4-butanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a chain extender, was charged, and dimethylformamide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further charged and stirred. After stirring, diphenylmethane diisocyanate (MILLIONATE MT manufactured by Tosoh Corporation), which is an isocyanate, was heated and stirred while charging, and the reaction was carried out while confirming the increase in viscosity. Diphenylmethane diisocyanate was sequentially charged and stirred so that the liquid viscosity changed from 500 mPa · s to 1500 mPa · s. After measuring the liquid viscosity, it was cooled at room temperature to obtain a thermoplastic polyurethane. Table 1 shows the composition and hardness of the thermoplastic polyurethane.

[Impregnated with porous thermoplastic polyurethane]
A sheet containing the obtained PET non-woven fabric and non-porous polyurethane was cut out to a size of 380 mm × 380 mm. Then, the cut out sheet was impregnated with a porous thermoplastic polyurethane having a D hardness of 80. Table 1 shows the composition and hardness of the porous thermoplastic polyurethane.

The impregnation was applied as follows. A 25% thermoplastic polyurethane DMF solution was heated to 30 ° C. The sheet was allowed to stand on it for 10 minutes to allow the DMF solution to permeate. It subsided in DMF solution for an additional 5 minutes. Next, the sheet was taken out and placed on a glass plate, and the adhered DMF solution was removed by tracing the surface of the sheet with a doctor knife. The same operation was performed on the back surface.

Next, the raw fabric impregnated with the DMF solution was immersed in a 10% aqueous solution having a DMF concentration maintained at 30 ° C. and left for 30 minutes to solidify the porous thermoplastic polyurethane. Then, the sheet obtained by coagulating and impregnating the porous thermoplastic polyurethane was immersed in hot water at 70 to 95 ° C., sandwiched between metal rolls, squeezed out, and then immersed in hot water again for washing with water. .. Then, the raw fabric washed with water was placed in a hot air dryer (device name: safety oven SPH-202 / ESPEC CO., LTD.) And dried at 100 ° C. for 40 minutes. In this way, the original fabric of the polishing pad (referred to as the pad original fabric intermediate) was obtained. In this treatment, the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body by impregnating and wet-solidifying the solvent-based polymer elastic body in the production method of the present invention is 0. It corresponds to "a step of imparting a porous polymer elastic body so as to be .49 or less".

[Flatization and grooving of pad original intermediate]
A polishing pad was prepared by buffing the surface of the pad raw material intermediate with sandpaper (count # 180) to eliminate thickness unevenness and flatten it. Then, an adhesive tape was attached to the surface to be polished. Then, a grid groove having a groove width of 2.0 mm, a groove depth of 0.5 mm, and a pitch of 15 mm was formed on the polished surface of the polishing pad by a flattening groove processing machine. Then, a grooved polishing pad was obtained by cutting out a polishing pad having a lattice groove formed into a circle having a diameter of 370 mm. Then, it was evaluated by the above-mentioned evaluation method. The results are shown in Table 1.

[Example 2]
In [Synthesis of Porous Thermoplastic Polyurethane] of Example 1, a grooved polishing pad was produced in the same manner as in Example 1 except that the polycaprolactone diol was changed to polyhexamethylene adipate, and the same method as in Example 1 was produced. Evaluated in. The results are shown in Table 1.

[Comparative Example 1]
Similar to the thermoplastic polyurethane described in Example 1, polycaprolactone diol (Plaxel 210 manufactured by Daicel Co., Ltd.) as a polymer diol and 1,4-butanediol (manufactured by Tokyo Kasei Kogyo Co., Ltd.) as a chain extender. A grooved polishing pad was obtained using a thermoplastic polyurethane produced using diphenylmethane diisocyanate (MILLIONATE MT manufactured by Toso Co., Ltd.) as an isocyanate, and a TMF solution having a thermoplastic polyurethane concentration of 25% in impregnation. Then, it was evaluated by the above-mentioned evaluation method. The results are shown in Table 1.

As shown in Table 1, the polishing pad of Example 1 controls the mass ratio of each component of the non-porous polymer elastic body and the porous polymer elastic body, that is, increases the amount of the porous polymer elastic body. Therefore, the polishing speed becomes high. On the other hand, in the case of Comparative Example 1, since the number of porous polymer elastic bodies in the polishing pad is small, the groove shape is damaged during polishing, and the polishing rate becomes low.

The polishing pad according to the present invention can be applied to polishing of various semiconductor devices, bare silicon, MEMS (Micro Electro Mechanical Systems), SiC semiconductors and the like in a manufacturing process.

Claims (9)

It is a polishing pad in which a non-porous polymer elastic body and a porous polymer elastic body are impregnated into a non-porous polymer, and the porous polymer elastic body contains thermoplastic polyurethane, with respect to the mass of the porous polymer elastic body. A polishing pad having a mass ratio of the non-porous polymer elastic body of 0.49 or less. The polishing pad according to claim 1, which has a porous structure in which the average pore area of the porous polymer elastic body is 10 to 100 μm ^2. The polishing pad according to claim 1 or 2, wherein the polymer diol forming the thermoplastic polyurethane contained in the porous polymer elastic body has a coagulation rate of 0.1 to 1.5 mol. The polishing pad according to any one of claims 1 to 3, wherein the thermoplastic polyurethane contained in the porous polymer elastic body has a D hardness of 35 to 85. The polishing pad according to any one of claims 1 to 4, wherein the fiber constituting the nonwoven fabric is a polyester fiber, and the average single fiber diameter thereof is 1 to 10 μm. The thermoplastic polyurethane contained in the porous polymer elastic body contains a thermoplastic polyurethane obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender.
The high molecular weight diols are poly (ethylene adipate), poly (butylene adipate), poly (caprolactone diol), poly (3-methyl-1,5-pentamethylene adipate), poly (hexamethylene adipate), and poly (3-). Methyl-1,5-pentamethylene terephthalate), poly (diethylene glycol adipate), poly (nonamethylene adipate), poly (2-methyl-1,8-octamethylene adipate), poly (2-methyl-1,8-octa) Includes at least one selected from the group consisting of methylene-co-nonamethylene adipate), poly (ethylene glycol), poly (diethylene glycol), poly (tetramethylene glycol), poly (propylene glycol).
The organic diisocyanate contains at least one selected from the group consisting of 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-toluene diisocyanate, and isophorone diisocyanate.
The chain extender is selected from the group consisting of ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol. The polishing pad according to any one of claims 1 to 5, which comprises at least one. The polishing pad according to any one of claims 1 to 6, wherein the apparent density of the polishing pad is 0.50 to 0.90 g / cm ^3. The polishing pad according to any one of claims 1 to 7, wherein the polishing pad has a C hardness of 80 or more. A process of imparting a water-based non-porous polymer elastic body to a non-woven fabric made of ultrafine fiber-generating fibers, a process of converting ultrafine fiber-generating fibers into ultrafine fibers to form an ultrafine fiber non-woven fabric, and a wet method impregnated with a solvent-based polymer elastic material. The steps of solidifying and imparting the porous polymer elastic body so that the ratio of the mass of the non-porous polymer elastic body to the mass of the porous polymer elastic body is 0.49 or less are sequentially performed. A method for manufacturing a polishing pad, which comprises.