JP2005131720A - Method of manufacturing polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polishing pad, efficiently workable in a state of sticking a polishing layer and a cushion layer, superior in grooving accuracy and thickness accuracy, and revealing a superior polishing characteristic. <P>SOLUTION: This polishing pad includes the polishing layer and the cushion layer, and grooves the polishing layer in a state of sticking the cushion layer composed of unfoamed elastomer to the polishing layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a polishing pad. In particular, the present invention relates to a method of manufacturing a polishing pad that can be suitably used for a process of mechanically flattening the surface of an insulating layer formed on a semiconductor substrate such as silicon or the surface of a metal wiring.

  As the density of semiconductor devices increases, the importance of multilayer wiring and the accompanying interlayer insulation film formation, electrode formation of plugs, damascene, and the like is increasing. These are formed by applying an optical lithography technique, but in order to ensure the processing accuracy, the importance of the flattening process of these interlayer insulating films and electrode metal films is increasing. As an efficient technique for this planarization process, a polishing technique called CMP (Chemical Mechanical Polishing) has become widespread. This is a method in which the workpiece is pressed against the rotating elastic pad, and the slurry, which is an abrasive, is supplied while performing relative motion, and the uneven surface of the workpiece surface is preferentially polished with the polishing pad. is there.

  By the way, a polishing pad generally used at present is a polishing layer for polishing a workpiece through a slurry in order to achieve both flattening and a uniform polishing amount over the entire workpiece. Many of them have a two-layer structure with a cushion layer for following the undulation of a semiconductor wafer (for example, Patent Document 1).

  As a specific example of such a widely used two-layer pad, a polishing pad “IC manufactured by Rodel Co., Ltd.” using a wet foamed polyurethane obtained by impregnating a polyurethane solution into a nonwoven fabric and then wet-forming it as a cushion layer. -1000 / Suba400 "(trade name) is known.

  In addition, the polishing layer has a polishing pad surface that supplies slurry between the workpiece and the polishing layer and discharges excess slurry, and also discharges waste generated during processing. Therefore, grooves such as a lattice, a concentric circle, and a spiral are formed.

  The inventors of the present invention have tried grooving on the surface of the polishing layer with respect to such a known polishing pad. When a tool for grooving touches the surface of the polishing layer, compressive stress is applied in the thickness direction of the polishing pad. It was confirmed that the cushion layer with a small volume modulus was compressed and deformed, the thickness of the polishing pad was changed, and a groove with the desired dimension could not be obtained or the groove depth was partially different. .

  In order to perform grooving without such deformation, it is conceivable to perform grooving on the polishing layer in advance and bond it to the cushion layer (Patent Document 2). However, in the method of applying a groove process to the polishing layer and then bonding it to the cushion layer, the processing waste generated by the groove process enters between the polishing layer and the cushion layer, or the pressure is applied where there is no groove at the time of bonding. However, since the pressing pressure is not sufficiently applied where there is a groove, air is caught between the polishing layer and the cushion layer, resulting in unevenness in the thickness of the polishing pad, which is essentially flat. It is difficult to obtain a sufficient polishing characteristic with the thickness spots used for the purpose of making the film. Although it is conceivable to include a process waste removal step before the step of bonding the polishing layer and the cushion layer, the number of steps increases, which is not preferable in terms of economy.

  In other words, the typical characteristics required for the polishing pad are preferentially polished on the uneven surface of the workpiece surface, resulting in good flatness, and following the undulation of the workpiece. Can be uniformly polished over the entire workpiece (uniformity), and surface defects such as scratches and dust are not caused by polishing on the surface of the workpiece. If the polishing pad has uneven thickness, the pressure concentrates on the locally thickened part, affecting the flatness and uniformity, and causing surface defects such as scratches and dust. Therefore, it is possible to achieve good stability of flatness and uniformity and to suppress surface defects. That is, it is very important that there is no variation in the thickness of the polishing pad itself.

In addition, since the groove formed in the polishing layer greatly affects the elastic characteristics of the polishing pad, if the groove depth varies, the elastic characteristics of the polishing pad also vary, resulting in flatness and uniformity. Variation may occur, or surface defects such as scratches and dust may occur due to uneven pressure.
JP-A-6-21028 JP 2000-238202 A

  The object of the present invention is to produce a polishing pad that can efficiently perform grooving while the polishing layer and the cushion layer are bonded together, and is excellent in thickness accuracy and grooving accuracy, and exhibits good polishing characteristics. Is to provide a method.

In order to solve the above problems, the present invention has the following configuration. That is,
(1) A method for producing a polishing pad, characterized by performing groove processing of the polishing layer in a state where the polishing layer and a cushion layer made of a non-foamed elastomer are bonded together,
(2) The method for producing a polishing pad according to (1), wherein the cushion layer has a volume modulus of elasticity of 40 MPa or more and a tensile modulus of 0.1 MPa or more and 20 MPa or less.

  According to the present invention, it is possible to provide a polishing pad that can be efficiently processed, has excellent groove processing accuracy and thickness accuracy, and has stable polishing characteristics.

  In the manufacturing method of the polishing pad of the present invention, it is necessary to use a non-foamed elastomer as a cushion layer. Non-foamed elastomer is an elastic body that does not have a foamed structure. For example, olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, ester-based thermoplastic elastomer, urethane-based thermoplastic elastomer, amide Examples thereof include thermoplastic elastomers such as thermoplastic elastomers, and rubber elastic bodies such as natural rubber, nitrile rubber, neoprene rubber, polybutadiene rubber, polyurethane rubber, and silicon rubber. By using non-foamed elastomer with a small amount of compressive deformation compared to the foam generally used as a cushion layer at present, when polishing the surface of the polishing layer to which the cushion layer is bonded, the polishing pad The amount of deformation can be minimized and highly accurate groove processing is possible. When a material having a foam structure is used as the cushion layer, when the groove is processed on the surface of the polishing layer, the cushion layer is easily compressed and deformed, and a highly accurate groove cannot be formed. Furthermore, if the foam structure is not uniform, the amount of deformation is partially different, and the accuracy of the groove is further lowered, which is not preferable.

  From the viewpoint of polishing characteristics, the cushion layer preferably has a bulk modulus of 40 MPa or more and a tensile modulus of 0.1 MPa or more and 20 MPa or less. More preferably, the volume modulus of elasticity of the cushion layer is 60 MPa or more, more preferably 90 MPa or more, a preferred tensile modulus is 0.5 MPa or more and 18 MPa or less, and a more preferred tensile modulus is 5 MPa or more and 15 MPa or less. The volume modulus is obtained by the following equation by applying an isotropic pressure to a measured object whose volume has been measured in advance and measuring the volume change.

Volume modulus = applied pressure / (volume change / original volume of measured object)
For example, if the original volume is 1 cm ³ and the volume change when the applied pressure is isotropically applied to 0.07 MPa is 0.00005 cm ³ , the bulk modulus is 1400 MPa. For the volume modulus, water at 25 ° C. is placed in a container equipped with a level gauge, and a sample having a volume of 1 cm ³ is immersed in the water in the container. Next, the container containing water and the sample is placed in a sealed container, and the inside of the sealed container is pressurized with nitrogen gas. The measurement pressure is obtained by a method of reading the volume change of the sample when the pressure is applied in the range from 0.03 MPa to 0.14 MPa from the liquid level change. Although there is no restriction | limiting in particular as an upper limit of this volume elastic modulus, About 300 Mpa or less is practical in order to fully ensure cushioning properties.

  In addition, the tensile elastic modulus is obtained by applying a tensile stress to the cushion layer with a dumbbell shape, and a tensile strain (= tensile length change / original length of the sample) in the range of 0.01 to 0.03. Measured and calculated by the following formula.

Tensile modulus = ((tensile stress when tensile strain is 0.03) − (tensile stress when tensile strain is 0.01)) / 0.02
Examples of the measuring device include Tensilon universal testing machine “RTM-100” (manufactured by Orientec). As measurement conditions, the test speed is 5 cm / min, and the shape of the test piece is a dumbbell shape having a width of 5 mm at the center of the test piece and a sample length of 50 mm.

  When the volume elastic modulus of the cushion layer is preferably set to 40 MPa or more and the tensile elastic modulus is set to 0.1 MPa or more and 20 MPa or less, when used for polishing the semiconductor substrate, the flatness uniformity over the entire surface of the semiconductor substrate ( Uniformity) is very good.

  Specific examples of such a cushion layer include non-foamed elastomers such as natural rubber, nitrile rubber, neoprene rubber, polybutadiene rubber, polyurethane rubber, and silicon rubber.

  A preferable thickness of the cushion layer is 0.1 to 100 mm. If it is smaller than 0.1 mm, the uniformity tends to deteriorate. Moreover, when larger than 100 mm, there exists a tendency for global flatness and local flatness to be impaired. A preferable thickness range is 0.2 to 5 mm, and more preferably 0.5 to 2 mm.

  In the present invention, layers other than the polishing layer and the cushion layer may be formed within a range not impairing the object of the present invention.

  A double-sided pressure-sensitive adhesive tape is preferably used for bonding the polishing layer and the cushion layer. Examples of the base material of the double-sided pressure-sensitive adhesive tape include paper, nonwoven fabric, cloth, glass cloth, polyethylene, polypropylene, polyester, vinyl chloride, polytetrafluoroethylene, polyimide and other resin films, polyethylene, polyurethane, acrylic foams, Examples thereof include metal foils such as aluminum and copper. Specific examples of the adhesive for the double-sided adhesive tape include rubber-based, acrylic-based, and silicone-based adhesives. Moreover, what used only the adhesive as the uniform film shape without using a base material can also be used as a double-sided adhesive tape. Moreover, the adhesive force of the adhesive surface of a double-sided adhesive tape may be the same on the front and back, or may differ. From the viewpoint of polishing properties, a double-sided adhesive tape that does not use a substrate is preferably used.

  In the present invention, the groove processing is performed on the surface of the polishing layer with the cushion layer bonded together, but the processing method of the groove is not particularly limited. Specifically, a method of forming a groove by cutting the surface of the polishing layer using a device such as a router, contacting a heated mold, hot wire, etc. on the surface of the polishing layer to dissolve the contact portion And a method of forming grooves. Further, the shape of the groove is not particularly limited. Specific examples include a grid shape, a spiral shape, a concentric circle shape, and a dimple shape.

  The polishing layer preferably has a foamed structure in that the polishing rate is high and dust and scratches can be reduced. A known method can be used as a method for forming the foam structure of the polishing layer. For example, various foaming agents are blended in the monomer or polymer, followed by foaming by heating or the like, hollow microbeads are dispersed and cured in the monomer or polymer, and the microbead portion is closed cell A method in which a molten polymer is mechanically stirred and foamed, and then cooled and cured, and a solution in which the polymer is dissolved in a solvent is formed into a sheet, and then in a poor solvent for the polymer. Examples include a method of immersing and extracting only the solvent, a method of impregnating a monomer into a sheet-like polymer having a foam structure, and then polymerizing and curing. The foamed structure of the polishing layer in the present invention may be either open-celled or closed-celled. However, in the case of open-celled, the abrasive penetrates into the polishing layer during polishing, and polishing such as hardness and elastic modulus is performed. Closed cells are preferred because the physical properties of the layer may change over time and the polishing characteristics may deteriorate. Among these, the formation of the foam structure of the polishing layer and the control of the bubble diameter are relatively simple, and the monomer is impregnated into the sheet-like polymer having the foam structure in that the preparation of the polishing layer is also simple. Thereafter, a polymerization and curing method is preferred.

  The material of the sheet-like polymer having the foamed structure is not particularly limited as long as the monomer can be impregnated. Specifically, polyurethane, polyurea, soft vinyl chloride, natural rubber, neoprene rubber, chloroprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, silicone rubber, fluoro rubber, etc. Resin sheet, cloth, nonwoven fabric, paper and the like. In addition, these sheet-like polymers may contain various additives such as abrasives, lubricants, antistatic agents, antioxidants, stabilizers and the like for the purpose of improving the characteristics of the polishing pads to be produced. good. Among these, a material mainly composed of polyurethane is preferable in that the bubble diameter can be controlled relatively easily. Polyurethane is a polymer synthesized based on polyisocyanate polyaddition reaction or polymerization reaction. The compound used as the object of the polyisocyanate is an active hydrogen-containing compound, that is, a compound containing two or more polyhydroxy groups or amino groups. Examples of the polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, but are not limited thereto. The polyhydroxy group-containing compound is typically a polyol, and examples thereof include polyether polyol, polytetramethylene ether glycol, epoxy resin-modified polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and silicone polyol. It is preferable to determine the combination and optimum amount of polyisocyanate and polyol, catalyst, foaming agent, and foam stabilizer depending on the hardness, the cell diameter and the expansion ratio.

  The average cell diameter of the sheet-like polymer having a foam structure should be determined by the type of the monomer and the sheet-like polymer used and the characteristics of the polishing layer to be produced. For example, when polyurethane is used, it is preferably 500 μm or less from the viewpoint of good flattening characteristics such as global flatness of a manufactured polishing layer and local flatness which is flatness of local unevenness of a semiconductor substrate. The average cell diameter is more preferably 300 μm or less, and even more preferably 100 μm or less. The average bubble diameter refers to a value measured by observing a cross section of the polishing layer with a magnification of 200 times, measuring the bubble diameter of the next recorded SEM photograph with an image processing apparatus, and taking the average value.

The density of the sheet-like polymer having a foamed structure should be determined by the type of monomer and sheet-like polymer to be used and the characteristics of the polishing layer to be produced. Is preferably 0.5 to 1.0 g / cm ³ . If it is lower than 0.5 g / cm ^{3, the} global flatness tends to be poor due to a decrease in the bending elastic modulus of the polishing layer to be manufactured, and if it is higher than 1.0 g / cm ³ , the bending elastic modulus of the polishing layer to be manufactured is higher. This is not preferable because the uniformity tends to deteriorate due to the increase in size, and scratches and dust tend to be generated on the polished semiconductor substrate surface. More preferably, it is 0.6 to 0.9 g / cm ³ . The density means a value measured by the method described in Japanese Industrial Standard (JIS) K7222.

  The monomer is not particularly limited as long as it undergoes a polymerization reaction such as addition polymerization, polycondensation, polyaddition, addition condensation, and ring-opening polymerization. Specific examples include vinyl compounds, epoxy compounds, isocyanate compounds, dicarboxylic acids and the like. Among these, a vinyl compound is preferable in terms of easy impregnation into a sheet-like polymer and polymerization. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, methyl (α-ethyl) acrylate, ethyl (α- Ethyl) acrylate, propyl (α-ethyl) acrylate, butyl (α-ethyl) acrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl Methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate , Isobornyl methacrylate, acrylic acid, methacrylic acid, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, dimethyl maleate, diethyl maleate, dipropyl maleate, N-isopropylmaleimide, N- Cyclohexylmaleimide, N-phenylmaleimide, N, N ′-(4,4′-diphenylmethane) bismaleimide, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride , Styrene, α-methylstyrene, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, Methacrylate, and the like. Among these, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, methyl (α-ethyl) Acrylate, ethyl (α-ethyl) acrylate, propyl (α-ethyl) acrylate, and butyl (α-ethyl) acrylate are preferable in terms of easy impregnation of the sheet-like polymer and polymerization. In addition, these monomers may be 1 type or may mix 2 or more types. These monomers may be added with various additives such as abrasives, lubricants, antistatic agents, antioxidants and stabilizers for the purpose of improving the properties of the polishing layer to be produced. .

  The monomer polymerization initiator and curing agent used in the polishing layer of the present invention are not particularly limited, and can be appropriately used depending on the type of the monomer. For example, when a vinyl compound is used as a monomer, azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide, isopropyl peroxydicarbonate Can be used. In addition, a redox polymerization initiator, for example, a combination of peroxide and amine can also be used. These polymerization initiators and curing agents can be used singly or in combination of two or more.

  Further, in the present invention, a method is adopted in which a monomer is brought into contact with a sheet-like polymer having a foam structure in a container containing the monomer, and the monomer is contained therein to be polymerized and cured. it can. In this case, it is also preferable to perform treatments such as heating, pressurization, decompression, stirring, shaking, and ultrasonic vibration for the purpose of increasing the impregnation rate.

  The amount of monomer impregnated into the sheet-like polymer having a foam structure should be determined by the type of monomer and sheet-like polymer used and the characteristics of the polishing layer to be produced. However, for example, when methyl methacrylate is used as the monomer and polyurethane is used as the sheet-like polymer, the content ratio of the polymer polymerized from the monomer in the polymerization cured product to the polyurethane is 40 by weight. It is preferable that it is / 60-70 / 30. When the content ratio of the polymer obtained from the monomer mixture is less than 40 by weight, it is not preferable because the flattening characteristics tend to be poor due to a decrease in hardness and bending elastic modulus. On the other hand, when the content ratio exceeds 70, the uniformity and hardness tend to increase due to the increase in hardness and flexural modulus, and dust and scratches tend to increase. The content ratio of the polymer polymerized from the monomer and the polyurethane is more preferably 40/60 to 65/35 by weight ratio. In addition, the polymer and polyurethane content obtained from the monomer in the polymerized cured product can be measured by a pyrolysis gas chromatography / mass spectrometry technique. As an apparatus that can be used in this method, a double shot pyrolyzer “PY-2010D” (manufactured by Frontier Laboratories) is used as a thermal decomposition apparatus, and “TRIO-1” (manufactured by VG) is used as a gas chromatograph / mass spectrometer. Can be mentioned.

  Examples of the polymerization curing method include a method in which a sheet-like polymer having a foam structure impregnated with a monomer is inserted into a mold made of a gas barrier material and heated, but is not limited to this method.

  Gas barrier materials include inorganic glass, metals such as aluminum, copper, iron, SUS, polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), resins having gas barrier properties such as polyamide, films, and multilayers. A laminated resin, a film, etc., of a resin having a gas barrier property such as polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), polyamide and the like, produced by a method such as extrusion molding, laminating, coating, etc. Can be mentioned. Among these, inorganic glass and metal are preferable in that they have heat resistance and the surface properties of the manufactured polishing pad are good.

  The method for inserting the sheet-like polymer having a foam structure impregnated with the monomer into the mold made of the gas barrier material is not particularly limited. Specifically, a gasket made of an elastic material having gas barrier properties such as soft vinyl chloride, neoprene rubber, butadiene rubber, styrene butadiene rubber, and ethylene propylene rubber is disposed around the sheet-like polymer, and 2 is interposed through the gasket. A method of sandwiching a sheet-like polymer between two sheets of a gas barrier material, a method of inserting and sealing a sheet-like polymer in a casing made of a gas barrier material, and a sheet polymer in a bag made of a gas barrier film The method of inserting and sealing is mentioned. Moreover, when there is a possibility of tearing during polymerization and curing like a bag, it is also preferable to put it in a casing having gas barrier properties. In addition, when polymerized and cured without being inserted into a mold made of a gas barrier material, the monomer is volatilized from the sheet-like polymer, and the quality reproducibility of the manufactured polishing layer tends to be insufficient. As a result, the polishing characteristics tend to become unstable, which is not preferable. The gas barrier material here refers to a material in which the monomer does not volatilize from the sheet-like polymer when the sheet-like polymer having a foam structure impregnated with the monomer is inserted and sealed.

  The order of the step of impregnating the monomer into the sheet-like polymer having a foam structure and the step of inserting the sheet-like polymer having the foam structure impregnated with the monomer into the mold made of a gas barrier material is particularly It is not limited. Specifically, (1) A method in which a sheet-like polymer is immersed in a tank containing a monomer so as to be impregnated with the monomer, and then taken out from the tank and inserted into a mold made of a gas barrier material. (2) A method in which a sheet-like polymer is inserted into a mold made of a gas barrier material, and then a monomer is injected into the mold, sealed, and impregnated with the monomer. Can be mentioned. Among these, (2) is preferable in that the monomer odor is not scattered and the working environment is good.

  The heating method for polymerization and curing is not particularly limited. Specifically, heating in an air bath such as a hot air oven, heating in a water bath or oil bath, heating by a jacket or hot press, and the like can be given. Among them, heating in a water bath, an oil bath, or a jacket is preferable because the heat capacity of the heat medium is large and the heat generated during polymerization can be quickly dissipated.

  The heating temperature and time should be determined by the monomer, the type and amount of the polymerization initiator, the thickness of the resin plate, etc., for example, methyl methacrylate as the monomer and azobisisobutyronitrile as the polymerization initiator. When polyurethane is used for the sheet-like polymer, it can be polymerized and cured by heating at 120 ° C. for about 3 hours after heating at 70 ° C. for about 10 hours.

  Examples of polymerization and curing methods other than heating include polymerization and curing by irradiation with light, electron beam, and radiation. In addition, it is preferable to mix | blend a polymerization initiator, a sensitizer, etc. in the monomer as needed in that case.

  For example, when a vinyl compound is used as the monomer and polyurethane is used as the sheet-like polymer, the polymerized cured product may contain a polymer obtained from the vinyl compound and polyurethane in an integrated manner when the polishing layer is formed. Is preferable because the polishing characteristics are stable. Here, the inclusion of the polymer obtained from the vinyl compound and the polyurethane in an integrated manner means that the polymer phase obtained from the vinyl compound and the polyurethane phase are not separated, but quantitatively expressed. Then, the infrared spectrum obtained by observing various portions of the polishing layer essentially having a polishing function with a micro-infrared spectrometer having a spot size of 50 μm shows the infrared spectrum of the polymer obtained from the vinyl compound. It has an absorption peak and an infrared absorption peak of polyurethane, and the infrared spectra at various points are almost the same. Examples of the microinfrared spectroscopic device used here include “IR μs” (manufactured by SPECTRA-TECH).

  The polishing layer can be completed by grinding the front and back surfaces of the polymerized cured product to the required thickness, or by slicing to the required thickness. The grinding process is not particularly limited, and devices such as NC routers, diamond discs, belt sanders, etc., and the slicing process is not particularly limited, such as a band knife, a cutting board, or the like, and known devices can be used.

  The thickness of the polishing layer is preferably 0.1 to 10 mm. If it is thinner than 0.1 mm, the mechanical properties of the cushion layer used as the base of the polishing pad or the polishing surface plate located under the cushion layer are more significantly reflected in the polishing properties than the mechanical properties of the polishing layer itself. On the other hand, if it is thicker than 10 mm, the mechanical characteristics of the cushion layer are not reflected, and the groove processing accuracy of the polishing layer surface and the processing accuracy of the polishing pad into a circle are improved. When used for polishing, the followability to the undulation of the semiconductor substrate tends to decrease and the uniformity tends to deteriorate. From the viewpoint of planarization characteristics of polishing, the thickness of the polishing layer is preferably 0.2 to 5 mm, more preferably 0.5 to 2 mm.

  In the case of closed cells, the average cell diameter of the polishing layer is preferably 500 μm or less from the viewpoint of good global flatness and local flatness. The average cell diameter is more preferably 300 μm or less, and even more preferably 100 μm or less.

The density of the polishing layer is preferably 0.5 to 1.0 g / cm ³ . If it is less than 0.5 g / cm ^{3, the} global flatness tends to be poor due to a decrease in the flexural modulus. If it is greater than 1.0 g / cm ^{3, the} uniformity is deteriorated due to an increase in the flexural modulus or after polishing. Since there is a tendency that scratches and dust are likely to be generated on the surface of the semiconductor substrate, it is not preferable. More preferably, it is 0.6 to 0.9 g / cm ³ .

  The polishing layer preferably has a micro rubber A hardness of 80 degrees or more. When the micro rubber A hardness is less than 80 degrees, the planarization characteristic tends to deteriorate, which is not preferable. More preferably, it is 90 degrees or more. The hardness of the layer adjacent to the outermost layer, that is, the cushion layer, is preferably lower than the hardness of the polishing layer, and more preferably 10 degrees or more in order to obtain good cushioning properties. In addition, the micro rubber A hardness in the present invention refers to a value measured with a micro rubber hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. The micro rubber hardness tester MD-1 is capable of measuring the hardness of thin and small samples that have been difficult to measure with a conventional hardness tester, and is approximately 1 / of the spring type rubber hardness tester (durometer) A type. Since it is designed and manufactured as a reduced model of 5, the measured value gives a measured value almost the same as the value measured with the spring type rubber hardness tester A type. In addition, since the thickness of a normal polishing pad or a hard layer is too thin with 5 mm or less, it is appropriate to obtain | require with the micro rubber hardness meter MD-1 rather than the spring type rubber hardness meter.

  The polishing target of the polishing pad produced according to the present invention is not particularly limited, but can be preferably used for polishing a semiconductor substrate. More specifically, the surface of an insulating layer or metal wiring formed on a semiconductor wafer is preferable as an object to be polished. Specifically, the insulating layer includes an interlayer insulating film or lower insulating film of metal wiring, shallow trench isolation (STI) used for element isolation, and the metal wiring includes aluminum, tungsten, copper, etc. Structurally, there are damascene, dual damascene, plug, etc. Currently, silicon oxide is mainly used as the insulating film. However, the use of a low dielectric constant insulating film is being studied due to the problem of delay time, and any of them can be polished in the polishing pad of the present invention. In addition, when copper is used for the metal wiring, a barrier metal such as silicon nitride is also subject to polishing. In addition to the semiconductor substrate, it can also be preferably used for polishing optical members such as magnetic heads, hard disks, color filters for liquid crystal displays, and back plates for plasma displays, ceramics, sapphire, and the like.

  Next, the method of polishing using the polishing pad produced according to the present invention is not particularly limited as a polishing apparatus to be used, but when used for polishing a semiconductor substrate, the polishing head, the present invention It is preferable to include a polishing surface plate for fixing the polishing pad, and means for rotating the polishing head, the polishing surface plate, or both.

  As a polishing method, first, the polishing pad of the present invention is fixed to a polishing surface plate of a polishing apparatus so that the polishing pad faces the polishing head. The semiconductor substrate is fixed to the polishing head by a method such as a vacuum chuck. The polishing surface plate is rotated, the polishing head is rotated in the same direction as the rotation direction of the polishing surface plate, and pressed against the polishing pad. At this time, the polishing agent is supplied from a position where the polishing agent enters between the polishing pad and the semiconductor substrate. The pressing pressure is usually performed by controlling the force applied to the polishing head. The pressing pressure is preferably 0.01 to 0.2 MPa because good polishing characteristics can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the description. Various evaluations of the polishing pad were performed as follows.

  The micro rubber A hardness of the polishing layer and the cushion layer was measured with a micro rubber A hardness meter “MD-1” (manufactured by Kobunshi Keiki Co., Ltd.).

  The density of the polishing layer was measured by the method described in JIS K7222.

  The average bubble diameter of the polishing layer was determined by analyzing a photograph obtained by observing the pad cross section at a magnification of 200 times with an image processing apparatus using a scanning electron microscope “SEM2400” (manufactured by Hitachi, Ltd.). All the bubble diameters present were measured, and the average value was taken as the average bubble diameter.

  The thickness of the polishing layer, cushion layer, and polishing pad is a dial gauge “ID-C112A” (manufactured by Mitutoyo Corporation), and the groove depth of the polishing layer is digital caliper “CD-15C” (manufactured by Mitutoyo Corporation). ). The thickness unevenness of the polishing pad and the groove depth of the polishing layer were measured at any 10 points of the polishing pad or the groove of the polishing layer, and the difference between the maximum value and the minimum value was 0.1 mm or more. It was rejected.

  Polishing evaluation was performed as follows.

1. Test wafer (1) Test wafer for global flatness evaluation A 10 mm square die is placed on a 101.6 mm (4 inch) silicon wafer (oxide film thickness: 2 μm) with an oxide film. Mask exposure using photoresist, 20μm wide, 0.7μm high lines are placed in a 10mm square die by line and space in the left half with 230μm space, 230μm wide, height by RIE A 0.7 μm line is arranged in a right-half line and space with a 20 μm space. The test wafer for global flatness evaluation thus produced was used.

(2) Scratch, test wafer for uniformity evaluation A 101.6 mm (4 inch) silicon wafer (oxide film thickness: 1 μm) with an oxide film was used.

2. Evaluation of polishing characteristics A double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) is applied to the surface of the polishing layer that is to be applied to the cushion surface, and this is bonded to the nonwoven fabric wet polyurethane as the cushion layer. Double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was applied to the other surface of the cushion layer to produce a two-layer polishing pad. Next, the polishing pad was affixed on the surface plate of a polishing machine “LM-15E” (manufactured by Lapmaster SFT). Then, using a diamond dresser “CMP-M” (Asahi Diamond Industrial Co., Ltd.) (diameter 142 mm), rotating in the same direction as the polishing platen at a pressing pressure of 0.04 MPa, a polishing platen rotation number of 25 rpm, and a dresser rotation number of 25 rpm. The polishing pad was conditioned for 5 minutes while supplying pure water onto the polishing pad at 10 ml / min. After cleaning the polishing pad for 2 minutes while supplying pure water onto the polishing pad at 100 ml / min, a test wafer for global flatness evaluation was attached to the polishing head, and a polishing slurry having a working concentration described in the instruction manual “ While SC-1 ″ (Cabot) was supplied onto the polishing pad at 35 ml / min, it was rotated in the same direction as the polishing platen at a polishing pressure of 0.04 MPa, a polishing platen rotation of 45 rpm, and a polishing head rotation of 45 rpm. Polishing was performed for a predetermined time. The surface of the wafer was not dried, and the surface of the wafer was washed with a polyvinyl alcohol sponge while applying pure water immediately, and dried by blowing dry compressed air. The thickness of the oxide film on the 20 μm line and 230 μm line in the center 10 mm die of the test wafer for global flatness evaluation was measured using “Lambda Ace” VM-2000 (manufactured by Dainippon Screen Mfg. Co., Ltd.). Was evaluated as global flatness. Polishing time within 240 seconds when the global level difference between the 20 μm wide wiring region and the 230 μm wide wiring region of the test wafer for global flatness evaluation became 0.2 μm was regarded as acceptable.

  In addition, the same conditioning as described above was performed, and the thickness of the oxide film on the surface was measured at 198 points determined in advance using “Lambda Ace” VM-2000 (manufactured by Dainippon Screen Mfg. Co., Ltd.). The test wafer was attached to the polishing head, and the polishing slurry “SC-1” (manufactured by Cabot) described in the instruction manual was supplied onto the polishing pad at a rate of 35 ml / min. Polishing was performed for a predetermined time by rotating in the same direction as the polishing platen at a polishing platen rotation number of 45 rpm and a polishing head rotation number of 45 rpm. The wafer surface is not dried, and the wafer surface is washed with polyvinyl alcohol sponge while applying pure water immediately, left to dry in a natural state, and then a wafer surface dust inspection device ("WM-3" manufactured by Topcon Corporation). )), The number of surface dusts having a diameter of 0.5 μm or more and the number of surface scratches having a width and length of 0.5 μm or more were measured, and a total of 100 or less surface defects, which was the sum of dust and scratches, was accepted. .

  Next, 198 points determined using “Lambda Ace” VM-2000 (manufactured by Dainippon Screen Mfg. Co., Ltd.) were measured for the thickness of the oxide film after polishing, and each point was determined by the following equation (2). Further, the polishing rate was calculated, and the uniformity was calculated by the following equation (3). Uniformity passed 15% or less.

Polishing rate = (thickness of oxide film before polishing−thickness of oxide film after polishing) / polishing time (2).

Uniformity (%) = (maximum polishing rate−minimum polishing rate) / (maximum polishing rate + minimum polishing rate) × 100
(3).

Example 1
Polyether polyol: “Sanix FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of monoethylene glycol, amine catalyst: “Dabco 33LV” "(Air Products Japan Co., Ltd.) 1.95 parts by weight, amine catalyst:" Toyocat ET "(Tosoh Co., Ltd.) 0.14 parts by weight, silicone foam stabilizer:" TEGOSTAB B 8462 "(Th. Goldschmidt AG) B) consisting of 9 parts by weight of A liquid prepared by mixing 1 part by weight of foaming agent: 0.55 parts by weight of water and isocyanate having a liquid temperature of 40 ° C .: “Sunfoam NC-703” The liquid was collided and mixed by a RIM molding machine at a discharge pressure of 16 MPa, and then discharged at a discharge rate of 800 g / sec into a mold maintained at 40 ° C. for 10 minutes. By location, foamed polyurethane block thickness 10.0 mm (micro rubber A hardness: 47 degrees, a density: 0.73 g / cm ^3, average cell diameter: 35 [mu] m) were produced. Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 2 mm.

Next, the foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added for 45 minutes. Next, the foamed polyurethane sheet impregnated with methyl methacrylate was sandwiched between two glass plates via a vinyl chloride gasket, and polymerized and cured by heating at 70 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. A polishing layer was prepared by grinding both surfaces of the hard foam sheet thus obtained to a thickness of 1.25 mm. The obtained polishing layer had a micro rubber A hardness of 92 degrees, a density of 0.76 g / cm ³ , an average cell diameter of 42 μm, and a polymethyl methacrylate content of 55 wt% in the polishing layer.

  Non-foamed nitrile rubber (volume elastic modulus = 140 MPa, tensile elastic modulus = 4.5 MPa) having a thickness of 1 mm is used for the cushion layer, and the polishing layer and double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) are used. And pasted together. Furthermore, double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was attached to the surface of the cushion layer opposite to the surface to which the polishing layer was bonded. This was subjected to a grid-like groove processing with a width of 2 mm, a depth of 0.5 mm, and a pitch width of 15 mm on the surface of the polishing layer with an NC router, and then cut into a circle with a diameter of 380 mm to prepare a polishing pad. When the depths of the grooves formed on the surface of the polishing pad were measured at 10 points determined in advance, all were 0.5 mm, and no machining unevenness was confirmed. Further, when the thickness of the polishing layer was measured at 10 points determined in advance, all of them were 2.45 mm and there was no variation. Next, this polishing pad was affixed on the surface plate of a polisher, and polishing evaluation was performed. Thirty-two surface defects were observed on the polished wafer. Further, the polishing time when the global level difference between the 20 μm wide wiring region and the 230 μm wide wiring region of the test wafer for global flatness evaluation was 0.2 μm was 180 seconds. Uniformity was 9.0%.

  The polishing pad thickness unevenness and the polishing layer groove depth unevenness were acceptable, and the polishing characteristics were also acceptable.

Example 2
Using the polishing layer used in Example 1, non-foamed chloroprene rubber (volume elastic modulus = 50 MPa, tensile elastic modulus = 11 MPa) having a thickness of 1 mm was used as a cushion layer, and the double-sided adhesive tape “442JS” was used as the polishing layer. They were pasted together (manufactured by Sumitomo 3M). Furthermore, double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was attached to the surface of the cushion layer opposite to the surface to which the polishing layer was bonded. This was subjected to a grid-like groove processing with a width of 2 mm, a depth of 0.5 mm, and a pitch width of 15 mm on the surface of the polishing layer with an NC router, and cut into a circle with a diameter of 380 mm to prepare a two-layer polishing pad. When the depths of the grooves formed on the surface of the polishing pad were measured at 10 points determined in advance, all were 0.5 mm, and no machining unevenness was confirmed. Further, when the thickness of the polishing layer was measured at 10 points determined in advance, all of them were 2.45 mm and there was no variation. Next, this polishing pad was affixed on the surface plate of a polisher, and polishing evaluation was performed. 35 surface defects were observed on the polished wafer. Further, the polishing time when the global level difference between the 20 μm wide wiring region and the 230 μm wide wiring region of the test wafer for global flatness evaluation was 0.2 μm was 240 seconds. The uniformity was 12.0%.

  The polishing pad thickness unevenness and the polishing layer groove depth unevenness were acceptable, and the polishing characteristics were also acceptable.

Example 3
Using a polishing pad “IC-1000” (trade name) (thickness: 1.25 mm) manufactured by Rodel as a polishing layer, a non-foamed polyurethane rubber (volume elastic modulus = 100 MPa, tensile elastic modulus = 10 MPa) having a thickness of 2 mm. The polishing layer and a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) were bonded together as a cushion layer. Furthermore, double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was attached to the surface of the cushion layer opposite to the surface to which the polishing layer was bonded. This was subjected to a grid-like groove processing with a width of 2 mm, a depth of 0.5 mm, and a pitch width of 15 mm on the surface of the polishing layer with an NC router, and then cut into a circle with a diameter of 380 mm to prepare a polishing pad. When the depth of the groove formed on the surface of the polishing pad was measured at 10 points determined in advance, all were 0.5 mm, and no machining unevenness was confirmed. Further, when the thickness of the polishing layer was measured at 10 points determined in advance, all were 3.45 mm and there was no variation. Next, this polishing pad was affixed on the surface plate of a polisher, and polishing evaluation was performed. 25 surface defects were observed on the polished wafer. In addition, the polishing time when the global step between the 20 μm wide wiring region and the 230 μm wide wiring region of the test wafer for global flatness evaluation was 0.2 μm was 210 seconds. The uniformity was 12.0%.

  The polishing pad thickness unevenness and the polishing layer groove depth unevenness were acceptable, and the polishing characteristics were also acceptable.

Comparative Example 1
Using the polishing layer used in Example 1, a nonwoven fabric wet foamed polyurethane having a thickness of 1 mm (volume elastic modulus = 3 MPa, tensile elastic modulus = 50 MPa) as a cushioning layer and the double-sided adhesive tape “442JS” (Sumitomo 3M) (Made by Co., Ltd.). Furthermore, double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was attached to the surface of the cushion layer opposite to the surface to which the polishing layer was bonded. This was subjected to a grid-like groove processing with a width of 2 mm, a depth of 0.5 mm, and a pitch width of 15 mm on the surface of the polishing layer with an NC router, and cut into a circle with a diameter of 380 mm to prepare a two-layer polishing pad. When the depth of the groove formed on the surface of the polishing pad was measured at 10 points determined in advance, 4 points were 0.3 mm, 3 points were 0.4 mm, and 2 points were 0.5 mm. confirmed. Further, when the thickness of the polishing layer was measured at 10 points determined in advance, all of them were 2.45 mm and there was no variation. Next, this polishing pad was affixed on the surface plate of a polisher, and polishing evaluation was performed. 185 surface defects were observed on the polished wafer. Further, the polishing time when the global level difference between the 20 μm wide wiring region and the 230 μm wide wiring region of the test wafer for global flatness evaluation was 0.2 μm was 240 seconds. Uniformity was 9.0%.

  The polishing pad thickness unevenness and the polishing layer groove depth unevenness were rejected. Also, the polishing characteristics were unacceptable.

Comparative Example 2
The polishing layer used in Example 1 was used, and the polishing layer was cut into a circle having a diameter of 380 mm with an NC router, and a lattice-like groove with a width of 2 mm, a depth of 0.5 mm, and a pitch width of 15 mm was formed on the surface. . Next, double-sided pressure-sensitive adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) is applied to the opposite surface of the polishing layer which has been grooved, and this is used as a cushion layer to form a non-foamed nitrile rubber (volume elastic modulus = 140 MPa, tensile elastic modulus = 4.5 MPa). Further, a double-sided pressure-sensitive adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) is applied to the surface of the cushion layer opposite to the surface to which the polishing layer is bonded, and the cushion layer and both surfaces protrude along the outer shape of the polishing layer. The adhesive tape was cut out to prepare a two-layer polishing pad. When the depth of the groove formed on the surface of the polishing pad was measured at 10 points determined in advance, all were 0.5 mm and there was no processing unevenness. Further, when the thickness of the polishing layer was measured at 10 points determined in advance, the variation was 2.45 mm for 3 points, 2.55 mm for 2 points, and 2.5 mm for 5 points. Next, this polishing pad was affixed on the surface plate of a polisher, and polishing evaluation was performed.

  124 surface defects were observed on the polished wafer. Further, the polishing time when the global level difference between the 20 μm wide wiring region and the 230 μm wide wiring region of the test wafer for global flatness evaluation was 0.2 μm was 240 seconds. Uniformity was 19.0%. When a cross-section at a point where the thickness of the polishing pad was larger than 2.5 mm was cut out and visually observed, it was confirmed that processing scraps considered to have been generated when the polishing layer surface was grooved entered.

  The polishing pad thickness unevenness and the polishing layer groove depth unevenness were rejected. Also, the polishing characteristics were unacceptable.

Claims (2)

A polishing pad manufacturing method, comprising: polishing a groove of a polishing layer in a state where a polishing layer and a cushion layer made of a non-foamed elastomer are bonded together. The method for producing a polishing pad according to claim 1, wherein the cushion layer has a volume modulus of elasticity of 40 MPa or more and a tensile modulus of 0.1 MPa to 20 MPa.