JP2008068334A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad, hardly lowering in-plane uniform characteristic, hardly causing a change in polishing speed even in the case of continuous use for a long time. <P>SOLUTION: In this polishing pad 1 having a polishing layer made of polyurethane resin foam body, the polyurethane resin foam body contains 0.5-30 wt.% solid micro-bodies, which are made of non-foam polyurethane resin having a coefficient of water absorption of 1.5% or less and the storage elastic modulus at 40°C of 600-3,000 MPa and have the average particle diameter of 10-150 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention stabilizes flattening processing of optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing processing, In addition, the present invention relates to a polishing pad that can be performed with high polishing efficiency. The polishing pad of the present invention is particularly suitable for a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before further laminating and forming these oxide layers and metal layers. Used for.

  A typical material that requires high surface flatness is a single crystal silicon disk called a silicon wafer for manufacturing a semiconductor integrated circuit (IC, LSI). Silicon wafers have a highly accurate surface in each process of stacking and forming oxide layers and metal layers in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC, LSI, and other manufacturing processes. It is required to finish flat. In such a polishing finishing process, a polishing pad is generally fixed to a rotatable support disk called a platen, and a workpiece such as a semiconductor wafer is fixed to a polishing head. A polishing operation is performed by generating a relative speed between the platen and the polishing head by both movements, and continuously supplying a polishing slurry containing abrasive grains onto the polishing pad.

  The polishing characteristics of the polishing pad are required to be excellent in the flatness (planarity) and in-plane uniformity of the object to be polished and to have a high polishing rate. The flatness and in-plane uniformity of the object to be polished can be improved to some extent by increasing the elastic modulus of the polishing layer. The polishing rate can be improved by using a foam containing bubbles and increasing the amount of slurry retained.

  As a polishing pad in which the polishing layer is a foam, a polishing pad having a polishing layer in which hollow polymer resin beads such as acrylic beads, styrene beads, or polycarbonate beads are dispersed in a polyurethane resin is disclosed (Patent Document 1). ). Further, a polishing pad having a polishing layer containing hollow resin particles made of an acrylic resin, a vinyl chloride resin, a polyester resin, a vinylidene chloride resin, or a copolymer thereof is disclosed (Patent Document 2).

  Further, a resin balloon and a silicon-based nonionic surfactant having no hydroxyl group so as to be 5 to 50% by weight in the fine-cell polyurethane foam are added to the first component containing the isocyanate prepolymer, and the first component is added. The components are stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles to form a bubble / resin balloon dispersion, and the bubble / resin balloon dispersion is mixed with a chain extender having a molecular weight of 500 or less and cured. A method for producing a microcellular polyurethane foam, characterized in that it is made to occur, is disclosed (Patent Document 3).

  In recent years, improvement in in-plane uniformity at the wafer edge portion (region of 2 to 3 mm from the wafer end portion) has been demanded. However, the conventional polishing pad has a large change in polishing characteristics due to water absorption, and there are problems that the in-plane uniformity characteristic is lowered and the polishing rate is easily changed as it is used.

JP 2002-192456 A JP 2002-198335 A Japanese Patent No. 3558273

  An object of the present invention is to provide a polishing pad in which the in-plane uniformity characteristics are not easily lowered even when used continuously for a long time, and the polishing rate is hardly changed. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following polishing pad, and have completed the present invention.

  The present invention provides a polishing pad having a polishing layer comprising a polyurethane resin foam, wherein the polyurethane resin foam has a water absorption of 1.5% or less and a storage elastic modulus at 40 ° C. of 600 to 3000 MPa. The present invention relates to a polishing pad comprising 0.5 to 30% by weight of solid fine particles having an average particle diameter of 10 to 150 μm.

  The present inventors have found that by adding a specific amount of the solid microparticles to the polishing layer, a decrease in hardness and a change in dimensions due to water absorption can be suppressed. As a result, a polishing pad was obtained in which the in-plane uniformity characteristics were less likely to deteriorate than the conventional polishing pad, and the polishing rate was less likely to change.

  The non-foamed polyurethane resin, which is a raw material for the solid fine body, needs to have a water absorption of 1.5% or less. When the water absorption rate exceeds 1.5%, the dimensional change of the polishing layer increases due to water absorption when continuously used for a long time, so that the in-plane uniform characteristics of the polishing pad deteriorate.

  In addition, the non-foamed polyurethane resin that is a raw material of the solid minute body needs to have a storage elastic modulus at 40 ° C. of 600 to 3000 MPa. When the storage elastic modulus is less than 600 MPa, the dimensional change of the polishing layer becomes large due to heat when continuously used for a long time, so that the in-plane uniform characteristics of the polishing pad deteriorate, and when it exceeds 3000 MPa, the surface of the wafer is scratched. Is not preferred because it tends to occur. The reason for evaluating the storage elastic modulus at 40 ° C. is that, since the temperature of the polishing pad surface rises to about 40 ° C. during normal polishing, it is necessary to evaluate the physical properties of the solid micro object at that temperature. .

  Further, the average particle size of the solid minute body needs to be 10 to 150 μm. When the average particle size is less than 10 μm, it becomes difficult to uniformly disperse into the foam, so that the polishing characteristics cannot be made uniform throughout the polishing layer. On the other hand, when the average particle diameter exceeds 150 μm, the bubble diameter in the polyurethane resin foam becomes large or the number of bubbles decreases, so that the polishing characteristics deteriorate.

  Further, the polishing layer needs to contain 0.5 to 30% by weight of solid fine bodies. When the content of the solid minute body is less than 0.5% by weight, it is not possible to suppress a decrease in hardness and a dimensional change due to water absorption. On the other hand, when it exceeds 30% by weight, the urethanization reaction is inhibited, so that the physical properties of the polishing layer are lowered.

  The present invention also relates to a semiconductor device manufacturing method including a step of polishing a surface of a semiconductor wafer using the polishing pad.

  The polishing pad of the present invention may be only a polishing layer made of a polyurethane resin foam, or may be a laminate of a polishing layer and another layer (such as a cushion layer).

  Polyurethane resin is a preferred material for forming the polishing layer because it is excellent in abrasion resistance and a polymer having desired physical properties can be easily obtained by variously changing the raw material composition. The polyurethane resin is composed of an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, etc.), and a chain extender.

  As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. As the isocyanate component, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, Aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate; ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, etc. Aliphatic diisocyanate; 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate Isocyanate, alicyclic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur N-3200 and N-3300 (manufactured by Bayer), which are hexamethylene diisocyanate modified products, and as trade name duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.). Yes.

  Of the above isocyanate components, it is preferable to use at least two selected from the group consisting of aromatic diisocyanates, alicyclic diisocyanates, and polyfunctional polyisocyanates, and particularly, toluene diisocyanate and dicyclohexylmethane diisocyanate are used in combination. It is preferable.

  Examples of the high molecular weight polyol include those usually used in the technical field of polyurethane. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the obtained reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more. Among these, it is particularly preferable to use polytetramethylene ether glycol.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 2000 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, a polyurethane resin using the number average molecular weight does not have sufficient elastic properties and becomes a brittle polymer. Therefore, the polishing pad manufactured from this polyurethane resin becomes too hard and causes scratches on the wafer surface. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the pad life. On the other hand, when the number average molecular weight exceeds 2000, a polyurethane resin using the number average molecular weight becomes too soft, and a polishing pad produced from this polyurethane resin tends to have poor planarization characteristics.

  In addition to the above-described high molecular weight polyol as the polyol component, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2 -Hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (Hydroxymethyl) cyclohexanol, diethanolamine, N- methyldiethanolamine, and can be used in combination of low molecular weight polyols such as triethanolamine. Moreover, low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine, can also be used in combination. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more. The blending amount of the low molecular weight polyol, the low molecular weight polyamine or the like is not particularly limited, and is appropriately determined depending on the properties required for the polishing pad (polishing layer) to be produced, and is 20 to 70 mol% of the total polyol component. Is preferred.

  When a polyurethane resin foam is produced by a prepolymer method, a chain extender is used for curing the prepolymer. The chain extender is an organic compound having at least two active hydrogen groups, and examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5 -Bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2 , 6-diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4, 4'-diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetra Sopropyldiphenylmethane, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane, N, N′-di-sec-butyl -4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, m-xylylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine And polyamines exemplified by p-xylylenediamine and the like, or the low molecular weight polyols and low molecular weight polyamines mentioned above. These may be used alone or in combination of two or more.

  The ratio of the isocyanate component, the polyol component, and the chain extender in the present invention can be variously changed depending on the molecular weight of each, the desired physical properties of the polishing pad, and the like. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the isocyanate component relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the polyol component and the chain extender is 0.80 to 1.20. Is more preferable, and 0.99 to 1.15 is more preferable. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity and hardness cannot be obtained, and the polishing characteristics tend to be deteriorated.

  The solid minute body used in the present invention is made of a non-foamed polyurethane resin having a water absorption of 1.5% or less and a storage elastic modulus at 40 ° C. of 600 to 3000 MPa. The non-foamed polyurethane resin having physical properties can be produced by a known urethanization technique using, for example, a hydrophobic high molecular weight polyol not containing a hydrophilic group other than a hydroxyl group that reacts with an isocyanate group, the isocyanate component, and the like.

A hydrophilic group other than a hydroxyl group is a functional group or salt that generally contains an element such as oxygen, nitrogen, or sulfur. For example, —NH ₂ , —CONH ₂ , —NHCONH ₂ , —SH, —SO ₃ H _{, -OSO 3 H, - (CH} 2 CH 2 O) n -, - functional groups such as COOH, _-SO 3 M (M: an alkali _{metal), - OSO 3 M, -COOM} , -NR 3 X (R: And a salt such as an alkyl group, X: halogen).

  Examples of the hydrophobic high molecular weight polyol include hydroxy-terminated polyester polyol, polycarbonate polyol, polyester polycarbonate polyol, polyether polyol, polyether polycarbonate polyol, polyester amide, phenol resin polyol, epoxy polyol, polybutadiene polyol, and polyisoprene polyol. .

  Examples of the polyester polyol include polypropylene adipate, polybutylene adipate, polyhexamethylene adipate, and polycaprolactone polyol.

  Examples of the polyether polyol include polyhexamethylene glycol (PHMG), polytetramethylene glycol (PTMG), and polypropylene glycol (PPG).

  Examples of the polyether polycarbonate polyol include diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, polypropylene glycol and / or polytetramethylene glycol, phosgene, and diallyl carbonate (for example, diphenyl carbonate). ) Or a reaction product with a cyclic carbonate (for example, propylene carbonate).

  As the polyester polycarbonate polyol, a reaction product of polyester glycol such as polycaprolactone polyol and alkylene carbonate, an ethylene carbonate is reacted with a polyhydric alcohol, and then the obtained reaction mixture is reacted with an organic dicarboxylic acid. The product etc. which become are illustrated.

  The said hydrophobic high molecular weight polyol may be used individually by 1 type, and may use 2 or more types together. The number average molecular weight of the hydrophobic high molecular weight polyol is preferably 550 to 800. In particular, polytetramethylene glycol having hydrolysis resistance and excellent mechanical strength is preferably used.

  Moreover, it is preferable that the solid minute body is formed from the same material as the polyurethane resin foam constituting the polishing layer. When the solid fine body and the polyurethane resin foam constituting the polishing layer are formed of the same material, the polishing characteristics can be made uniform throughout the polishing layer. In particular, a reaction cured product of an isocyanate-terminated prepolymer and a chain extender having an NCO weight% of 9.2 to 20% is preferable.

  The non-foamed polyurethane resin, which is a raw material for the solid minute body, needs to have a water absorption of 1.5% or less, preferably 1% or less.

  Further, the non-foamed polyurethane resin needs to have a storage elastic modulus at 40 ° C. of 600 to 3000 MPa, and preferably 1500 to 2000 MPa.

  In addition, the average particle size of the solid minute body needs to be 10 to 150 μm, and preferably 40 to 130 μm.

  The polyurethane resin foam can be produced by applying a known urethanization technique such as a melting method or a solution method, but is preferably produced by a melting method in consideration of cost, work environment, and the like.

  The polyurethane resin foam can be produced by either the prepolymer method or the one-shot method. However, an isocyanate-terminated prepolymer is synthesized beforehand from an isocyanate component and a polyol component, and this is reacted with a chain extender. The polymer method is preferred because the resulting polyurethane resin has excellent physical properties.

  As the isocyanate-terminated prepolymer, those having a molecular weight of about 800 to 5000 are preferable because of excellent processability and physical characteristics.

  In the production of the polyurethane resin foam, a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound are mixed and cured. In the prepolymer method, the isocyanate-terminated prepolymer becomes an isocyanate group-containing compound, and the chain extender becomes an active hydrogen group-containing compound. In the one-shot method, the isocyanate component becomes an isocyanate group-containing compound, and the chain extender and the polyol component become active hydrogen group-containing compounds.

  The polyurethane resin foam can be produced by a mechanical foaming method. In particular, a mechanical foaming method using a silicon surfactant which is a copolymer of polyalkylsiloxane and polyether is preferable. Examples of the silicon-based surfactant include SH-192, L-5340 (manufactured by Toray Dow Corning Silicone), B-8465 (manufactured by Gold schmidt), and the like.

  In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed.

An example of a method for producing a fine cell type polyurethane resin foam will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
1) Foaming process for producing a cell dispersion of isocyanate-terminated prepolymer A first component is prepared by mixing an isocyanate-terminated prepolymer, a solid microparticle, and a silicon surfactant, and the first component is made non-reactive. Stir in the presence of gas to disperse the non-reactive gas as fine bubbles to obtain a bubble dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing Agent (Chain Extender) Mixing Step A chain extender (second component) is added to the above cell dispersion, mixed and stirred to obtain a foaming reaction solution.
3) Casting process The above foaming reaction liquid is poured into a mold.
4) Curing process The foaming reaction liquid poured into the mold is heated and reacted and cured.

  The solid minute body is added to the first component so as to be 0.5 to 30% by weight in the polyurethane resin foam. The addition amount of the solid microparticles is preferably 2 to 15% by weight.

  The silicon-based surfactant is preferably added to the first component so as to be 0.05 to 10% by weight in the polyurethane resin foam, and more preferably 0.5 to 5% by weight. When the amount of the silicon-based surfactant is less than 0.05% by weight, it tends to be difficult to obtain a foam having fine bubbles. On the other hand, when it exceeds 10% by weight, it tends to be difficult to obtain a polyurethane resin foam having high hardness due to the plastic effect of the silicon surfactant.

  As the non-reactive gas used to form the fine bubbles, non-flammable gases are preferable, and specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof. In view of cost, it is most preferable to use air that has been dried to remove moisture.

  As a stirrer for dispersing the non-reactive gas in the form of fine bubbles and dispersing it in the first component, a known stirrer can be used without particular limitation. Specifically, a homogenizer, a dissolver, a two-axis planetary mixer (planetary) Mixer) and the like. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained.

  In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a cell dispersion in a foaming process, and the stirring which adds and mixes the chain extender in a mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the foaming step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

  In the method for producing a polyurethane resin foam, heating and post-curing the foam that has reacted until the foaming reaction liquid is poured into the mold and no longer flows has the effect of improving the physical properties of the foam. Is preferred. The foam reaction solution may be poured into the mold and immediately put into a heating oven for post cure, and heat is not immediately transferred to the reaction components under such conditions, so the bubble size does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

  In the polyurethane resin foam, a known catalyst that promotes a polyurethane reaction such as tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  Polyurethane resin foam can be manufactured by batch feeding each component into a container and stirring. Alternatively, each component and non-reactive gas can be continuously supplied to the stirrer and stirred. It may be a continuous production method in which a dispersion is sent out to produce a molded product.

  In addition, the prepolymer that is the raw material of the polyurethane resin foam is placed in a reaction vessel, and then a chain extender is added and stirred, and then poured into a casting mold of a predetermined size to produce a block, and the block is shaped like a bowl or a band saw. In the method of slicing using a slicer, or in the above-described casting step, a thin sheet may be used. Alternatively, a raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.

  The average cell diameter of the polyurethane resin foam of this invention is about 10-60 micrometers, Preferably it is 20-50 micrometers. When deviating from this range, the polishing rate tends to decrease when used continuously for a long time, or the planarity (flatness) of the polished material (wafer) after polishing tends to decrease.

  The specific gravity of the polyurethane resin foam of the present invention is preferably 0.5 to 1.0. When the specific gravity is less than 0.5, the surface strength of the polishing layer decreases, and the planarity of the material to be polished tends to decrease. On the other hand, if it is larger than 1.0, the planarity is good, but the polishing rate tends to decrease.

  The hardness of the polyurethane resin foam of the present invention is preferably 45 to 70 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 45 degrees, the planarity of the material to be polished is lowered. When the Asker D hardness is more than 70 degrees, the planarity is good but the uniformity of the material to be polished is lowered. There is a tendency.

  The polishing surface of the polishing layer that comes into contact with the material to be polished preferably has an uneven structure for holding and renewing the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and updating the slurry. By forming a concavo-convex structure on the polishing surface, the slurry can be held and updated more efficiently. It can be performed well, and destruction of the material to be polished due to adsorption with the material to be polished can be prevented. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

  The method for producing the concavo-convex structure is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, pouring a resin into a mold having a predetermined surface shape, and curing. Using a press plate having a predetermined surface shape, a method of producing a resin by pressing, a method of producing using photolithography, a method of producing using a printing technique, a carbon dioxide laser, etc. Examples include a manufacturing method using laser light.

  The thickness of the polishing layer is not particularly limited, but is usually about 0.8 to 4 mm, and preferably 1.0 to 2.5 mm.

  As a method for producing the polishing layer having the above thickness, a method in which the block of the fine foam is made to have a predetermined thickness using a band saw type or canna type slicer, a resin is poured into a mold having a cavity having a predetermined thickness, and curing is performed. And a method using a coating technique or a sheet forming technique.

  The polishing pad of the present invention may be a laminate of the polishing layer and a cushion sheet.

  The cushion sheet (cushion layer) supplements the characteristics of the polishing layer. The cushion sheet is necessary for achieving both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a material having fine irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire material to be polished. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the cushion sheet. In the polishing pad of the present invention, it is preferable to use a cushion sheet that is softer than the polishing layer.

  Examples of the cushion sheet include a fiber nonwoven fabric such as a polyester nonwoven fabric, a nylon nonwoven fabric, and an acrylic nonwoven fabric, a resin-impregnated nonwoven fabric such as a polyester nonwoven fabric impregnated with polyurethane, a polymer resin foam such as polyurethane foam and polyethylene foam, a butadiene rubber, Examples thereof include rubber resins such as isoprene rubber and photosensitive resins.

  Examples of means for attaching the polishing layer and the cushion sheet include a method of pressing the polishing layer and the cushion sheet with a double-sided tape.

  The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. In consideration of preventing the penetration of the slurry into the cushion sheet, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. In addition, since the composition of the polishing layer and the cushion sheet may be different, the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force of each layer can be optimized.

  The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen. As the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of peeling from the platen after use of the polishing pad, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low.

  The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 1, a polishing surface plate 2 that supports a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. The polishing pad 1 is attached to the polishing surface plate 2 by attaching it with a double-sided tape, for example. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the semiconductor wafer 4 supported on each of the polishing surface plate 2 and the support table 5 face each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the semiconductor wafer 4 against the polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the polishing pad 1 while rotating the polishing surface plate 2 and the support base 5, and polishing is performed while supplying slurry. The flow rate of the slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited and are appropriately adjusted.

  As a result, the protruding portion of the surface of the semiconductor wafer 4 is removed and polished flat. Thereafter, a semiconductor device is manufactured by dicing, bonding, packaging, or the like. The semiconductor device is used for an arithmetic processing device, a memory, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Measurement and evaluation methods]
(Measurement of water absorption of non-foamed polyurethane resin)
This was performed according to JIS K7312-1996. A sample obtained by cutting the produced non-foamed polyurethane resin sheet into a size of width 20 mm × length 50 mm × thickness 1.27 mm was used as a sample. The sample was immersed in distilled water at 25 ° C. for 24 hours, and the water absorption was calculated by substituting the weight before and after immersion into the following formula.
Water absorption (%) = [(weight after immersion−weight before immersion) / weight before immersion] × 100

(Measurement of storage modulus of non-foamed polyurethane resin)
The storage elastic modulus (MPa) at 40 ° C. of a non-foamed polyurethane resin sheet produced under the following measurement conditions was measured using a dynamic viscoelasticity measuring device (manufactured by METLER TOLEDO, DMA861e).
Measurement condition frequency: 1 Hz
Temperature: -60 to 150 ° C
Temperature increase rate: 2.5 ° C / min
Control load: 3N

(Measurement of average particle size of solid microparticles)
The average particle size of the solid microparticles was measured using a particle size distribution measuring device (SALD-2000A, manufactured by Shimadzu Corporation) under the following conditions. And the calculated average value was made into the average particle diameter.
Measurement condition mode: Dry measurement absorbance range: 0.200
Refractive index: 1.7-0.2i
Integration count: 64

(Measurement of average bubble diameter)
A sample for measurement was prepared by cutting the produced polyurethane resin foam in parallel with a microtome cutter as thin as possible to a thickness of 1 mm or less. The sample surface was photographed at 100 times with a scanning electron microscope (S-3500N, manufactured by Hitachi Science Systems). Then, using an image analysis software (WIN-ROOF, manufactured by MITANI Corporation), the equivalent circle diameter of all bubbles in an arbitrary range was measured, and the average bubble diameter was calculated from the measured value.

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. The produced polyurethane resin foam was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) and used as a sample for measuring specific gravity, and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5% I put it. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Hardness measurement)
This was performed in accordance with JIS K6253-1997. The produced polyurethane resin foam was cut into a size of 2 cm × 2 cm (thickness: arbitrary) and used as a sample for hardness measurement, and was allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. . At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

(Measurement of dimensional change rate during water absorption)
This was performed according to JIS K7312. A sample obtained by cutting out the produced polyurethane resin foam into a size of width 20 mm × length 50 mm × thickness 1.27 mm was used as a sample. The sample was immersed in distilled water at 25 ° C. for 120 hours, and the dimensional change rate was calculated by substituting the length before and after the immersion into the following formula.
Dimensional change rate (%) = [(length after immersion−length before immersion) / length before immersion] × 100

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. This operation is repeated, and the polishing rate after 30 minutes of continuous polishing is shown in Table 1. Further, the polishing layer of the prepared polishing pad was brought into contact with pure water for 120 hours, and then the polishing rate was measured by the same method as described above. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.

The in-plane uniformity is obtained by polishing a thermal oxide film 1 μm thick on an 8-inch silicon wafer under the above polishing conditions until the thermal oxide film becomes 0.5 μm, and as shown in FIG. The maximum polishing rate and the minimum polishing rate were determined from the film thickness measured before and after the polishing at 29 predetermined positions including the position of 2 mm from the above, and evaluated by substituting these values into the following equation. This operation is repeated, and the in-plane uniformity after continuous polishing for 30 minutes is shown in Table 1. Further, the polishing layer of the prepared polishing pad was brought into contact with pure water for 120 hours, and then in-plane uniformity was evaluated by the same method as described above. The smaller the in-plane uniformity value, the higher the wafer surface uniformity.
In-plane uniformity (%) = {(maximum polishing rate−minimum polishing rate) / (maximum polishing rate + minimum polishing rate)} × 100

Production Example 1
In a container, 37.3 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 16.8 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetrafluoroethylene having a number average molecular weight of 650 41.6 parts by weight of methylene ether glycol and 4.2 parts by weight of 1,3-butanediol were added and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer (NCO weight%: 14%). 100 parts by weight of the isocyanate-terminated prepolymer adjusted to 60 ° C. and 42 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical amine, Iharacamine MT) melted at 120 ° C. were mixed. Reacted. Thereafter, curing was carried out at 100 ° C. for 20 hours to produce an unfoamed polyurethane resin sheet a. The non-foamed polyurethane resin sheet a had a water absorption rate of 0.8% and a storage elastic modulus at 40 ° C. of 1988 MPa.
The non-foamed polyurethane chip obtained by cutting the non-foamed polyurethane resin sheet a to about 1 × 1 mm with a cutter is pulverized using an ultracentrifugal mill (Retsch, ZM100) and a screen mesh size of 80 μm. A real microparticle A (average particle size 45 μm) was prepared.

Production Example 2
The non-foamed polyurethane chip obtained by cutting the non-foamed polyurethane resin sheet a to about 1 × 1 mm with a cutter is pulverized using an ultracentrifugal crusher (Retsch, ZM100) and a screen mesh size of 250 μm. Real microparticles B (average particle size 123 μm) were prepared.

Production Example 3
Polyethylene glycol having 38.1 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 17.2 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, and number average molecular weight of 600 in a container 39 parts by weight and 5.4 parts by weight of diethylene glycol were added and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer (NCO weight%: 13.8%). 100 parts by weight of the isocyanate-terminated prepolymer adjusted to 60 ° C. and 42 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical amine, Iharacamine MT) melted at 120 ° C. were mixed. Reacted. Thereafter, curing was performed at 100 ° C. for 20 hours to produce a non-foamed polyurethane resin sheet b. The non-foamed polyurethane resin sheet b had a water absorption rate of 3.1% and a storage elastic modulus at 40 ° C. of 1830 MPa.
The non-foamed polyurethane chip obtained by cutting the non-foamed polyurethane resin sheet b to about 1 × 1 mm with a cutter is crushed using an ultracentrifugal mill (Retsch, ZM100) and a screen mesh size of 250 μm. Real microparticles C (average particle size 175 μm) were prepared.

Example 1
In a reaction vessel, 26 parts by weight of a polyether-based isocyanate-terminated prepolymer (manufactured by Uniroyal, Adiprene L-325), 1 part by weight of the solid microparticle A, and a silicon surfactant (manufactured by Toray Dow Corning Silicone, SH- 192) 1 part by weight was added and mixed, adjusted to 80 ° C. and degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereto was added 6.8 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Amine, Iharacamine MT) previously melted at 120 ° C. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of this mixed liquid disappeared, it was put in an oven and post-cured at 110 ° C. for 6 hours to obtain a polyurethane resin foam block (content of solid micro-body A: 2.87% by weight). .
The polyurethane resin foam block was sliced using a band saw type slicer (manufactured by Fecken) to obtain a polyurethane resin foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. This buffed sheet is punched out with a diameter of 60 cm, and a groove processing machine is used to process concentric grooves with a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm, A polishing layer was obtained. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Further, the surface of the corona-treated cushion sheet (manufactured by Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that the addition amount of the solid microparticles A was changed from 1 part by weight to 5 parts by weight. The content rate of the solid minute body A is 12.89% by weight.

Example 3
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that 1 part by weight of the solid minute body B was used instead of 1 part by weight of the solid minute body A1. The content rate of the solid minute body B is 2.87% by weight.

Comparative Example 1
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that 1 part by weight of the solid minute body C1 was used instead of 1 part by weight of the solid minute body A. The content rate of the solid minute body C is 2.87% by weight.

Comparative Example 2
A polishing pad in the same manner as in Example 1 except that 1 part by weight of β-cyclodextrin powder (manufactured by Nacalai Tesque), which is a water-soluble polymer, was used instead of 1 part by weight of the solid microparticle A in Example 1. Was made. The content of β-cyclodextrin is 2.87% by weight.

Comparative Example 3
In Example 1, a polishing pad was prepared in the same manner as in Example 1 except that 0.5 part by weight of a resin balloon (manufactured by Nippon Philite Co., Ltd., Expandel 551D) was used instead of 1 part by weight of the solid microparticle A1. did. The content of the resin balloon is 1.45% by weight.

表１の結果より、本発明の研磨パッドは、長時間連続使用した場合でも面内均一特性が低下しにくく、研磨速度が変化しにくいことがわかる。

From the results shown in Table 1, it can be seen that the polishing pad of the present invention is less likely to have in-plane uniformity characteristics even when used continuously for a long time, and the polishing rate is less likely to change.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic showing 29 film thickness measurement positions on the wafer

Explanation of symbols

1: Polishing pad (polishing layer)
2: Polishing surface plate 3: Abrasive (slurry)
4: Material to be polished (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (2)

In the polishing pad having a polishing layer made of a polyurethane resin foam, the polyurethane resin foam has an average particle size of an unfoamed polyurethane resin having a water absorption of 1.5% or less and a storage elastic modulus at 40 ° C. of 600 to 3000 MPa. A polishing pad comprising 0.5 to 30% by weight of solid fine bodies having a diameter of 10 to 150 μm. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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