JP2008252017A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad in which dimension stability is maintained at a high level at the time of moisture absorption or water absorption, and polishing properties such as a planarization property, in-plane uniformity and the like are hardly deteriorated, and to provide a method for manufacturing the pad and a method for manufacturing a semiconductor device that use the polishing pad. <P>SOLUTION: In the polishing pad having a polish layer composed of a polyurethane foam, the polyurethane foam comprises a reaction cured body of (1) an isocyanate terminal prepolymer A which contains an isocyanate monomer, high molecular weight polyol α, and low-molecular weight polyol; (2) an isocyanate terminal prepolymer B which contains a large amount of diisocynate, or a large amount of diisocynate and high molecular weight polyol β; and a (3) a chain extender and a hollow microsphere. <P>COPYRIGHT: (C)2009,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 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 that satisfies the above characteristics, polishing pads made of polyurethane foam have been proposed (Patent Documents 1 and 2). The polyurethane foam is produced by reacting an isocyanate-terminated prepolymer with a chain extender (curing agent). As the polymer polyol component of the isocyanate prepolymer, hydrolysis resistance, elastic properties, abrasion resistance From the viewpoint of properties, polyether (polytetramethylene glycol having a number average molecular weight of 500 to 1600) and polycarbonate are used as suitable materials.

  However, in the polishing layer, the cohesive force of the hard segment is reduced during moisture absorption or water absorption, and the dimensional stability of the polishing layer is likely to be reduced. In a severe case, there is a problem that warping and waviness occur in the polishing pad, thereby gradually reducing polishing characteristics such as planarization characteristics and in-plane uniformity.

  Patent Document 3 discloses a polishing pad polymer composition having a volume swelling rate of 20% or less when immersed in water at a temperature of 23 ° C. for 72 hours for the purpose of improving the retention of the slurry. Yes. However, the polishing pad polymer composition uses a thermoplastic polymer as the polishing pad polymer, and it is difficult to maintain high dimensional stability of the polishing pad during moisture absorption or water absorption.

JP 2000-17252 A Japanese Patent No. 3359629 JP 2001-47355 A

  An object of the present invention is to provide a polishing pad that can maintain high dimensional stability at the time of moisture absorption or water absorption, and in which polishing characteristics such as flattening characteristics and in-plane uniformity are hardly deteriorated, and a method for manufacturing the same. 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 object can be achieved by the polishing pad shown below, and have completed the present invention.

That is, the present invention provides a polishing pad having a polishing layer comprising a polyurethane foam, wherein the polyurethane foam is:
(1) Isocyanate-terminated prepolymer A comprising an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol,
(2) a polymerized diisocyanate, or an isocyanate-terminated prepolymer B comprising a polymerized diisocyanate and a high molecular weight polyol β, and (3) a chain extender,
And a polishing pad characterized by containing hollow microspheres.

  Since the conventional polishing layer is a polyurethane foam having a hard segment formed only by physical crosslinking, it is considered that the cohesive force of the hard segment easily decreases during moisture absorption or water absorption. Therefore, it is considered that the dimensional change increases due to elongation, warpage, etc., as the polishing layer absorbs moisture or absorbs water.

  As a raw material of the polyurethane foam, the present inventors have (1) an isocyanate-terminated prepolymer A containing an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol, and (2) a multimerized diisocyanate, or Combined with an isocyanate-terminated prepolymer B containing a multimerized diisocyanate and a high-molecular-weight polyol β, and (3) a chemical crosslinking is regularly introduced into the polymer by reaction with a chain extender (three-dimensional crosslinking) It was found that by forming the structure regularly, the cohesive strength of the hard segments during moisture absorption or water absorption can be increased, and the dimensional stability of the polishing layer can be maintained high. In addition, by adding hollow microspheres to polyurethane resin to form foam, the hollow microspheres act like aggregates in polyurethane resin, and maintain higher dimensional stability of the polishing layer during moisture absorption or water absorption. I found out that I can do it.

  The high molecular weight polyol α is a polyether polyol having a number average molecular weight of 500 to 5000, and the isocyanate monomer is preferably toluene diisocyanate and dicyclohexylmethane diisocyanate. The high molecular weight polyol β is a polyether polyol having a number average molecular weight of 200 to 1000, and the multimerized diisocyanate is preferably an isocyanurate type and / or burette type multimerized hexamethylene diisocyanate. By using these, a polyurethane foam can be produced with good handling properties, and the effects of the present invention are more excellent.

  The addition amount of the multimerized diisocyanate or isocyanate-terminated prepolymer B is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the isocyanate-terminated prepolymer A. When the addition amount of the multimerized diisocyanate or isocyanate-terminated prepolymer B is less than 5 parts by weight, the ratio of chemical crosslinking in the polymer becomes insufficient, so that the cohesive strength of the hard segment at the time of moisture absorption or water absorption is insufficient, It tends to be difficult to maintain high dimensional stability of the polishing layer. On the other hand, when the amount exceeds 30 parts by weight, the ratio of chemical crosslinking in the polymer becomes excessive, and the hardness of the polishing layer becomes too high, so that the in-plane uniformity of the material to be polished is reduced, and the polyurethane foam has a resistance to resistance. Abrasion tends to decrease and the life of the polishing pad tends to be shortened. In addition, scratches are likely to occur on the surface of the material to be polished.

  The polyurethane foam preferably contains 1.5 to 2.5% by weight of hollow microspheres. When the content of the hollow microsphere is less than 1.5% by weight, the dimensional stability of the polishing layer at the time of moisture absorption or water absorption cannot be further improved, and polishing characteristics such as flattening characteristics and in-plane uniformity Tend to decrease gradually. On the other hand, when it exceeds 2.5% by weight, poor dispersion of the hollow microspheres tends to occur.

  Moreover, it is preferable that the average cell diameter of a hollow microsphere is 20-60 micrometers. When the average cell diameter is less than 20 μm, poor dispersion of the hollow microspheres tends to occur, and when it exceeds 60 μm, the strength of the polyurethane foam tends to decrease.

  The polyurethane foam preferably has a dimensional change rate of 0.5% or less at the time of water absorption and a change rate of bending elastic modulus at the time of water absorption of 25% or less. When the value is outside the range, the dimensional change increases when the polishing layer absorbs moisture or absorbs water, and the polishing characteristics such as flattening characteristics and in-plane uniformity tend to gradually decrease.

  The polyurethane foam preferably has an Asker D hardness of 45 to 65 degrees. When Asker D hardness is less than 45 degrees, the flatness of the material to be polished tends to decrease. On the other hand, when it is larger than 65 degrees, the flatness is good, but the in-plane uniformity of the material to be polished tends to be lowered. In addition, scratches are likely to occur on the surface of the material to be polished.

Further, the present invention provides a polishing pad production method comprising a step of mixing a first component containing at least an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane foam.
In the step, after preparing a dispersion in which hollow microspheres are added and dispersed in a polyurethane foam so as to be 1.5 to 2.5% by weight in the first component containing at least an isocyanate-terminated prepolymer, Mixing a second component containing a chain extender into the dispersion and curing to produce a polyurethane foam;
The first component is
(1) An isocyanate-terminated prepolymer A containing an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol, and (2) a multimerized diisocyanate, or a multimerized diisocyanate and a high molecular weight polyol β. Isocyanate-terminated prepolymer B,
A method for producing a polishing pad, comprising:

Further, the present invention provides a polishing pad production method comprising a step of mixing a first component containing at least an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane foam.
In the step, the first component containing at least an isocyanate-terminated prepolymer has hollow microspheres in the polyurethane foam in an amount of 1.5 to 2.5% by weight, and the silicon surfactant in the polyurethane foam. After adding 0.05 to 10% by weight and further stirring the first component with a non-reactive gas to prepare a bubble dispersion in which the non-reactive gas is dispersed as fine bubbles, the bubbles Mixing a second component containing a chain extender into the dispersion and curing to produce a polyurethane foam,
The first component is
(1) An isocyanate-terminated prepolymer A containing an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol, and (2) a multimerized diisocyanate, or a multimerized diisocyanate and a high molecular weight polyol β. Isocyanate-terminated prepolymer B,
A method for producing a polishing pad, comprising:

  Furthermore, the present invention 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 has a polishing layer made of polyurethane foam. The polishing pad of the present invention may be only the polishing layer or a laminate of the polishing layer and another layer (for example, a cushion layer).

  Polyurethane resin is a particularly preferable material for forming the polishing layer because it has excellent wear resistance and a polymer having desired physical properties can be easily obtained by variously changing the raw material composition.

  The polyurethane foam comprises (1) an isocyanate-terminated prepolymer A containing an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol, and (2) a multimerized diisocyanate, or a multimerized diisocyanate and a high molecular weight polyol β. And (3) a reaction cured product with a chain extender.

  As the isocyanate monomer, a known compound in the field of polyurethane can be used without particular limitation. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene Aromatic diisocyanates such as diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, nor Cycloaliphatic diisocyanates such as Renan diisocyanate. These may be used alone or in combination of two or more. Of these, it is preferable to use toluene diisocyanate and dicyclohexylmethane diisocyanate in combination.

  On the other hand, the multimerized diisocyanate in the present invention is an isocyanate-modified product or a mixture thereof that has been multimerized by adding three or more diisocyanates. Examples of the modified isocyanate include 1) trimethylolpropane adduct type, 2) burette type, and 3) isocyanurate type, among which isocyanurate type and burette type are particularly preferable.

  In the present invention, aliphatic diisocyanate is preferably used as the diisocyanate forming the multimerized diisocyanate, and 1,6-hexamethylene diisocyanate is particularly preferably used. The multimerized diisocyanate may be modified by urethane modification, allophanate modification, burette modification or the like.

  High molecular weight polyols α and β include polyether polyols typified by polytetramethylene ether glycol, polyester polyols typified by polybutylene adipate, reaction products of polyester glycol such as polycaprolactone polyol and polycaprolactone and alkylene carbonate. Polyester polycarbonate polyol exemplified by the above, obtained by reacting ethylene carbonate with polyhydric alcohol, then reacting the resulting reaction mixture with organic dicarboxylic acid, and transesterification of polyhydroxyl compound with aryl carbonate And polycarbonate polyol. These may be used alone or in combination of two or more.

  The number average molecular weight of the high molecular weight polyol α is not particularly limited, but is preferably 500 to 5000, more preferably 1000 to 2000, from the viewpoint of the viscoelastic properties of the obtained 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 5,000, the polyurethane resin using the number average molecular weight becomes too soft, so that the polishing pad produced from this polyurethane resin tends to have poor planarization characteristics.

  The number average molecular weight of the high molecular weight polyol β is not particularly limited, but is preferably 200 to 1000, more preferably 250 to 650, from the viewpoint of dimensional change and water absorption of the resulting polyurethane resin upon water absorption. is there. If the number average molecular weight is less than 200, the distance between crosslinks is shortened, so that it tends to be difficult to retain water. On the other hand, when the number average molecular weight exceeds 1000, the distance between crosslinks becomes long, so that the water absorption becomes high and the dimensional change at the time of water absorption tends to increase.

  The low molecular weight polyol is an essential raw material for the isocyanate-terminated prepolymer A. Examples of the low molecular weight polyol include 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 triethanolamine, and the like. These may be used alone or in combination of two or more. A low molecular weight polyol may be appropriately used as a raw material for the isocyanate-terminated prepolymer B.

  Moreover, low molecular weight polyamines such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine can also be used in combination as raw materials for the isocyanate-terminated prepolymers A and B. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These 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 characteristics required for the polishing pad (polishing layer) to be produced, but all active hydrogen which is a raw material of the isocyanate-terminated prepolymer A It is preferable that it is 10-25 mol% of a group containing compound.

  In preparing the isocyanate-terminated prepolymer B, it is preferable to blend the dimerized diisocyanate and the high molecular weight polyol β so that the NCO Index is 3 to 5, more preferably the NCO Index is 3 to 4.

  On the other hand, the NCO Index for producing the isocyanate-terminated prepolymer A is not particularly limited, and is usually about 1.5 to 2.5.

  When the polyurethane resin is produced by the 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 above-mentioned low molecular weight polyols and low molecular weight polyamines. These may be used alone or in combination of two or more.

  The ratio of (1) isocyanate-terminated prepolymer A, (2) multimerized diisocyanate or isocyanate-terminated prepolymer B, and (3) chain extender in the present invention can be varied depending on the molecular weight of each, the desired physical properties of the polishing pad, etc. . The addition amount of the multimerized diisocyanate or isocyanate-terminated prepolymer B is preferably 5 to 30 parts by weight, more preferably 10 to 20 parts by weight with respect to 100 parts by weight of the isocyanate-terminated prepolymer A. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the prepolymer relative to the number of active hydrogen groups (hydroxyl groups, amino groups) of the chain extender is 0.8 to 1.2. Preferably, it is 0.99 to 1.15. 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 polyurethane resin can be produced by applying a known urethanization technique such as a melting method or a solution method, but it is preferably produced by a melting method in consideration of cost, working environment, and the like.

  The polyurethane foam of the present invention is produced by a prepolymer method. The polyurethane resin obtained by the prepolymer method is suitable because of its excellent physical properties.

  The isocyanate-terminated prepolymers A and B are preferably those having a molecular weight of about 800 to 5000 because of excellent processability and physical characteristics.

  The polyurethane resin is heated by mixing (1) an isocyanate-terminated prepolymer A, (2) a first component containing a multimerized diisocyanate or an isocyanate-terminated prepolymer B, and (3) a second component containing a chain extender. Hardened and manufactured.

  In the present invention, hollow microspheres are used to make the polyurethane resin into a foam. The hollow microspheres may be added to a first component comprising (1) an isocyanate-terminated prepolymer A, and (2) a multimerized diisocyanate or an isocyanate-terminated prepolymer B, and (3) a second component comprising a chain extender. However, it is preferable to add to the first component in order to disperse it uniformly in the polyurethane foam.

  The hollow microsphere has a hollow inside and an outer shell made of resin. In the present invention, known hollow microspheres can be used without particular limitation. For example, EXPANSEL DE (manufactured by Japan Philite), Micropearl (manufactured by Matsumoto Yushi Kogyo), ARBOCEL (manufactured by Rettenmeier & Sone), Matsumoto Micro Examples include Sphere F (manufactured by Matsumoto Yushi Seiyaku).

  The addition amount of the hollow microspheres is not particularly limited, but is preferably added to the polyurethane foam so as to be 1.5 to 2.5% by weight, more preferably 1.6 to 2.4% by weight. .

  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 thermosetting polyurethane foam constituting the polishing pad (polishing layer) will be described below. The manufacturing method of this polyurethane foam has the following processes.
1) Mixing step of hollow microspheres (1) Hollow microspheres in polyurethane foam as a first component containing isocyanate-terminated prepolymer A and (2) multimerized diisocyanate or isocyanate-terminated prepolymer B Add to 5 wt% and disperse uniformly to obtain a dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Mixing step of curing agent (chain extender) A second reaction component containing (3) a chain extender is added to and mixed with the dispersion to obtain a reaction solution.
3) Casting step The reaction solution is poured into a mold.
4) Curing step The reaction solution poured into the mold is heated to cause reaction curing.

  In the production method of polyurethane foam, heating and post-curing the foam that has reacted until the reaction liquid is poured into the mold and no longer flows is effective in improving the physical properties of the foam and is extremely suitable. is there.

  You may use the catalyst which accelerates | stimulates well-known polyurethane reactions, such as tertiary amine type | system | group. 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 foam can be produced by batch feeding each component into a container and stirring, or by continuously feeding each component to the stirring device and stirring, then sending out the reaction solution and molding. May be a continuous production method.

  Also, prepolymers and hollow microspheres that are the raw materials for polyurethane foam are 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 prepare a block. In the method of slicing using a slicer or a band saw slicer, or in the above-mentioned casting step, a thin sheet may be formed. Alternatively, a raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane foam.

  Moreover, as a manufacturing method of a polyurethane foam, you may use together well-known methods, such as a mechanical foaming method and a chemical foaming method. In particular, it is preferable to use in combination with a mechanical foaming method using a silicon surfactant which is a copolymer of polyalkylsiloxane and polyether. Examples of the silicon-based surfactant include SH-192, L-5340 (manufactured by Toray Dow Corning Silicon), and the like.

An example of a method for producing a micro-bubble type thermosetting polyurethane foam using a mechanical foaming method will be described below. The manufacturing method of this polyurethane foam has the following processes.
1) Foaming step for preparing a cell dispersion (1) Hollow microspheres in a polyurethane foam as a first component containing isocyanate-terminated prepolymer A and (2) multimerized diisocyanate or isocyanate-terminated prepolymer B Add a silicone-based surfactant in the polyurethane foam to 0.05 to 10% by weight so as to be ˜2.5% by weight, and stir in the presence of a non-reactive gas. Gas is dispersed 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 (3) A second component containing a chain extender is added to the 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.

  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.

  A known stirring device can be used without particular limitation as a stirring device for dispersing non-reactive gas in the form of fine bubbles and dispersed in the first component containing the silicon-based surfactant. Specifically, a homogenizer, a dissolver, 2 A shaft planetary mixer (planetary mixer) is exemplified. 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. .

  The average cell diameter of the hollow microspheres in the polyurethane foam is preferably 20 to 60 μm, more preferably 30 to 50 μm. Further, the polyurethane foam preferably has a dimensional change rate at the time of water absorption of 0.5% or less, more preferably 0.4% or less. The polyurethane foam preferably has a flexural modulus change rate of 25% or less at the time of water absorption, more preferably 20% or less. In addition, the measuring method of each said physical property is based on description of an Example.

  Moreover, it is preferable that the average bubble diameter of the bubble formed by the mechanical foaming method in the said polyurethane foam is 20-70 micrometers, More preferably, it is 30-60 micrometers.

  The polyurethane foam preferably has an Asker D hardness of 45 to 65 degrees, more preferably 50 to 60 degrees.

  The polishing surface that contacts the material to be polished of the polishing pad (polishing layer) of the present invention has a concavo-convex structure for holding and updating 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 1.5 to 2.5 mm. As a method for producing the polishing layer having the thickness, a method of making the foam block a predetermined thickness by using a band saw type or canna type slicer, a resin is poured into a mold having a cavity of a predetermined thickness and cured. Examples thereof include a method and a method using a coating technique or a sheet forming technique.

  The thickness variation of the polishing layer is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large waviness, and there are portions where the contact state with the material to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with a dresser in which diamond abrasive grains are electrodeposited and fused in the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.

  Examples of a method for suppressing the variation in the thickness of the polishing layer include a method of buffing the surface of the polishing sheet sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

  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.

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

[Measurement and evaluation methods]
(Measurement of number average molecular weight)
The number average molecular weight was measured by GPC (gel permeation chromatography) and converted by standard polystyrene.
GPC device: manufactured by Shimadzu Corporation, LC-10A
Column: Polymer Laboratories, (PLgel, 5 μm, 500 mm), (PLgel, 5 μm, 100 mm), and (PLgel, 5 μm, 50 mm) connected to three columns, flow rate: 1.0 ml / min
Concentration: 1.0 g / l
Injection volume: 40 μl
Column temperature: 40 ° C
Eluent: Tetrahydrofuran

(Measurement of average cell diameter or average bubble diameter)
A sample for measuring the average cell diameter or average cell diameter was prepared by cutting the produced polyurethane foam as thin as possible to a thickness of 1 mm or less in parallel with a microtome cutter. The sample was fixed on a slide glass and observed at 100 times using SEM (S-3500N, Hitachi Science Systems, Ltd.). Using the image analysis software (WinRoof, Mitani Shoji Co., Ltd.), the obtained cells were measured for the total cell diameter (including the outer diameter) of hollow microspheres in an arbitrary range, and the average cell diameter was calculated. Similarly, the total bubble diameter of bubbles formed by a mechanical foaming method in an arbitrary range was measured, and the average bubble diameter was calculated.

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

(Measurement of hardness)
This was performed in accordance with JIS K6253-1997. A sample obtained by cutting the produced polyurethane foam into a size of 2 cm × 2 cm (thickness: arbitrary) was used as a sample for hardness measurement and 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 the produced polyurethane 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 48 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

(Measurement of change rate of flexural modulus during water absorption)
A sample obtained by cutting the produced polyurethane foam into a size of width 1 mm × length 3 mm × thickness 2 mm was used as a sample. The bending elastic modulus was measured under the following conditions using a measuring device (manufactured by Instron, 5864 tabletop testing machine system).
・ Jig for bending strength measurement: Distance between supporting points 22mm
・ Crosshead speed: 0.6mm / min
・ Moving displacement: 6.0mm
The sample was immersed in distilled water at 25 ° C. for 48 hours. Thereafter, the flexural modulus was measured by the same method as described above. The rate of change in flexural modulus at the time of water absorption was calculated by the following formula.
Rate of change (%) = [(bending elastic modulus when dry−flex elastic modulus after immersion) / flexural elastic modulus when dry] × 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 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. Table 1 shows the polishing rates for the 100th, 300th, and 500th wafers. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As polishing conditions, silica slurry (SS12, manufactured by Cabot Corporation) was added as a slurry at a flow rate of 150 ml / min. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.

  In the evaluation of planarization characteristics, after depositing a thermal oxide film of 0.5 μm on an 8-inch silicon wafer, performing a predetermined patterning, an oxide film of 1 μm is deposited by p-TEOS, and an initial step of 0.5 μm is formed. A wafer with a pattern was prepared, and this wafer was polished under the above conditions.

  The amount of scraping was measured as the flattening characteristic. In a pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and a pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the cutting of the space of 270 μm when the level difference of the upper part of the above two types of patterns is 2000 mm or less The amount was measured. If the amount of shaving is small, the amount of shaving that is not desired to be shaved is small and the flatness is high. Table 1 shows the amount of wear on the 100th, 300th and 500th wafers.

In-plane uniformity is evaluated by polishing for 2 minutes under the above polishing conditions using a 1-μm thick thermal oxide film deposited on an 8-inch silicon wafer, and polishing at 25 specific positions on the wafer as shown in FIG. The maximum polishing rate and the minimum polishing rate were obtained from the measured film thickness before and after, and the values were calculated by substituting them into the following formula. Table 1 shows the in-plane uniformity of the 100th, 300th and 500th wafers. Note that the smaller the in-plane uniformity value, the higher the uniformity of the wafer surface.
In-plane uniformity (%) = {(maximum polishing rate−minimum polishing rate) / (maximum polishing rate + minimum polishing rate)} × 100

Example 1
In a container, 1229 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetramethylene ether glycol 1901 having a number average molecular weight of 1018 Part by weight and 198 parts by weight of diethylene glycol were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer A.
100 parts by weight of the prepolymer A adjusted to 70 ° C. and degassed under reduced pressure, 10 parts by weight of multimerized 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type), and hollow micro Matsumoto Microsphere F-105 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd., average cell diameter: 35 μm) as a sphere was added to a polymerization vessel and mixed with a hybrid mixer (manufactured by Keyence) for 3 minutes. The obtained mixture was degassed under reduced pressure at 70 ° C. for 1 hour to obtain a dispersion. Thereto, 32.9 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. was added and mixed for 1 minute with a hybrid mixer to prepare a reaction solution. Then, the reaction solution was poured into a pan-type open mold (casting container). When the fluidity of the reaction solution ceased, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block.
The polyurethane foam block heated to about 80 ° C. was sliced using a slicer (AGW Tech, VGW-125) to obtain a polyurethane 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. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing sheet (polishing layer). A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was applied to the surface of the polishing sheet opposite to the grooved surface using a laminator. Furthermore, the surface of the cushion sheet (Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) subjected to corona treatment 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 a container, 100 parts by weight of 1,6-hexamethylene diisocyanate (Sumika N-3300, isocyanurate type), and 16.2 parts by weight of polytetramethylene ether glycol having a number average molecular weight of 250 are manufactured. (NCO Index: 4.0) and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer B1.
In Example 1, Prepolymer B1 (12 parts by weight) was used instead of 10 parts by weight of the multimerized 1,6-hexamethylene diisocyanate, and the amount of Matsumoto Microsphere F-105 added was changed from 3.36 parts by weight to 3. The polishing pad was changed in the same manner as in Example 1 except that the amount of 4,4′-methylenebis (o-chloroaniline) was changed from 32.9 parts by weight to 31.5 parts by weight. Produced.

Example 3
In a container, 100 parts by weight of 1,6-hexamethylene diisocyanate (Sumijour N-3300, isocyanurate type) manufactured by Sumika Bayer Urethane Co., Ltd. and 42.1 parts by weight of polytetramethylene ether glycol having a number average molecular weight of 650 (NCO Index: 4.0) and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer B2.
In Example 1, Prepolymer B2 (14.5 parts by weight) was used in place of 10 parts by weight of 1,6-hexamethylene diisocyanate, and Matsumoto Microsphere F-105 was added from 3.36 parts by weight. Polishing was performed in the same manner as in Example 1 except that the amount was changed to 3.44 parts by weight and the addition amount of 4,4′-methylenebis (o-chloroaniline) was changed from 32.9 parts by weight to 31.5 parts by weight. A pad was prepared.

Example 4
100 parts by weight of 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type) and 64.8 parts by weight of polytetramethylene ether glycol having a number average molecular weight of 1000 are placed in a container. (NCO Index: 4.0) and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer B3.
In Example 1, Prepolymer B3 (17.5 parts by weight) was used instead of 10 parts by weight of the multimerized 1,6-hexamethylene diisocyanate, and the amount of Matsumoto Microsphere F-105 added was changed from 3.36 parts by weight. Polishing was performed in the same manner as in Example 1 except that the amount of 4,4′-methylenebis (o-chloroaniline) was changed from 32.9 parts by weight to 31.5 parts by weight. A pad was prepared.

Example 5
100 parts by weight of the prepolymer A adjusted to 70 ° C. and degassed under reduced pressure, the prepolymer B1 (12 parts by weight), Matsumoto Microsphere F-105 (manufactured by Matsumoto Yushi Seiyaku, average cell diameter: 35 μm) as hollow microspheres 2 .25 parts by weight and 3.3 parts by weight of a silicon-based surfactant (manufactured by Toray Dow Corning Silicon, SH-192) were added to the polymerization vessel and mixed for 3 minutes with a hybrid mixer (manufactured by Keyence). The obtained mixture was degassed under reduced pressure at 70 ° C. for 1 hour to obtain a dispersion. Then, it stirred violently using the stirring blade until it reached the liquid level of the target density so that a bubble might be taken in in a reaction system at the rotation speed of 900 rpm. Thereto was added 31.5 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. The obtained reaction liquid was stirred for about 70 seconds, and then poured into a pan-type open mold (casting container). When the fluidity of the mixed solution disappeared, it was put in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block. Thereafter, a polishing pad was produced in the same manner as in Example 1.

Comparative Example 1
100 parts by weight of the prepolymer A and 3.0 parts by weight of a silicon-based surfactant (SH-192, manufactured by Toray Dow Corning Silicon) were added to the polymerization vessel, mixed, adjusted to 70 ° 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. To this, 26.6 parts by weight (NCO Index: 1.05) of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. was added. The mixed liquid was stirred for about 70 seconds, and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was put in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block. Thereafter, a polishing pad was produced in the same manner as in Example 1.

  As is apparent from the results in Table 1, the polishing pad of the present invention has high dimensional stability at the time of moisture absorption or water absorption, is excellent in polishing rate, flattening characteristics, and in-plane uniform characteristics, and variation in the characteristics is also suppressed. You can see that

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic showing 25 film thickness measurement positions on 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 (11)

In a polishing pad having a polishing layer made of polyurethane foam, the polyurethane foam is:
(1) Isocyanate-terminated prepolymer A comprising an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol,
(2) a polymerized diisocyanate, or an isocyanate-terminated prepolymer B comprising a polymerized diisocyanate and a high molecular weight polyol β, and (3) a chain extender,
A polishing pad comprising a reaction cured body and hollow microspheres. The polishing pad according to claim 1, wherein the high molecular weight polyol α is a polyether polyol having a number average molecular weight of 500 to 5,000, and the isocyanate monomer is toluene diisocyanate and dicyclohexylmethane diisocyanate. The polishing pad according to claim 1, wherein the high molecular weight polyol β is a polyether polyol having a number average molecular weight of 200 to 1,000, and the multimerized diisocyanate is an isocyanurate type and / or burette type multimerized hexamethylene diisocyanate. The polishing pad according to any one of claims 1 to 3, wherein the addition amount of the multimerized diisocyanate or the isocyanate-terminated prepolymer B is 5 to 30 parts by weight with respect to 100 parts by weight of the isocyanate-terminated prepolymer A. The polishing pad according to any one of claims 1 to 4, wherein the polyurethane foam contains 1.5 to 2.5% by weight of hollow microspheres. The polishing pad according to any one of claims 1 to 5, wherein the hollow microsphere has an average cell diameter of 20 to 60 µm. The polishing pad according to any one of claims 1 to 6, wherein the polyurethane foam has a dimensional change rate at the time of water absorption of 0.5% or less and a change rate of the flexural modulus at the time of water absorption of 25% or less. The polishing pad according to any one of claims 1 to 7, wherein the polyurethane foam has an Asker D hardness of 45 to 65 degrees. In a method for producing a polishing pad comprising a step of mixing a first component containing at least an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane foam,
In the step, after preparing a dispersion in which hollow microspheres are added and dispersed in a polyurethane foam so as to be 1.5 to 2.5% by weight in the first component containing at least an isocyanate-terminated prepolymer, Mixing a second component containing a chain extender into the dispersion and curing to produce a polyurethane foam;
The first component is
(1) An isocyanate-terminated prepolymer A containing an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol, and (2) a multimerized diisocyanate, or a multimerized diisocyanate and a high molecular weight polyol β. Isocyanate-terminated prepolymer B,
A method for producing a polishing pad comprising: In a method for producing a polishing pad comprising a step of mixing a first component containing at least an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane foam,
In the step, the first component containing at least an isocyanate-terminated prepolymer has hollow microspheres in the polyurethane foam in an amount of 1.5 to 2.5% by weight, and the silicon surfactant in the polyurethane foam. After adding 0.05 to 10% by weight and further stirring the first component with a non-reactive gas to prepare a bubble dispersion in which the non-reactive gas is dispersed as fine bubbles, the bubbles Mixing a second component containing a chain extender into the dispersion and curing to produce a polyurethane foam,
The first component is
(1) An isocyanate-terminated prepolymer A containing an isocyanate monomer, a high molecular weight polyol α, and a low molecular weight polyol, and (2) a multimerized diisocyanate, or a multimerized diisocyanate and a high molecular weight polyol β. Isocyanate-terminated prepolymer B,
A method for producing a polishing pad comprising: The manufacturing method of a semiconductor device including the process of grind | polishing the surface of a semiconductor wafer using the polishing pad in any one of Claims 1-8.

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