JP2013066977A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad having improved dressing properties while hardness is maintained.SOLUTION: The polishing pad has a polishing layer formed of a polyurethane resin foam. The polyurethane resin foam contains, as starting material components, (A) an isocyanate component, (B) a polyol component, (C) an aromatic compound that has one hydroxyl group and/or an aromatic compound that has one amino group, and (D) hollow microspheres.

Description

  The present invention performs stable and high polishing efficiency of optical materials such as lenses and reflecting mirrors, and silicon wafers, aluminum substrates, and materials that require high surface flatness such as general metal polishing. It is related with the polishing pad which can be performed. 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 that satisfies the above characteristics, a polishing pad made of a polyurethane resin foam has been proposed (Patent Documents 1 and 2). The polyurethane resin 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, From the viewpoint of wear and the like, polyether (polytetramethylene glycol having a number average molecular weight of 500 to 1600) and polycarbonate are used as suitable materials.

  Normally, when a large number of semiconductor wafers are planarized using a polishing pad, the fine irregularities on the surface of the polishing pad wear out, and the ability to supply an abrasive (slurry) to the processing surface of the semiconductor wafer is reduced. The flattening speed of the wafer processing surface is reduced or the flattening characteristics are deteriorated. For this reason, it is necessary to update and roughen (dress) the surface of the polishing pad using a dresser after the planarization of a predetermined number of semiconductor wafers. When dressing is performed for a predetermined time, innumerable fine irregularities are formed on the surface of the polishing pad, and the pad surface becomes fuzzy.

  However, the conventional polishing pad has a problem that the dressing speed at the time of dressing is low and the dressing takes too much time.

  In order to solve the above-mentioned problem, Patent Document 3 proposes a technique using a multimerized diisocyanate and an aromatic diisocyanate as an isocyanate component that is a raw material of a polyurethane resin foam.

  However, when the dimerized diisocyanate is used, the hardness of the polyurethane resin foam increases, and when a polishing pad made of the polyurethane resin foam is used, scratches tend to occur on the surface of the object to be polished.

JP 2000-17252 A Japanese Patent No. 3359629 JP 2006-297582 A

  An object of this invention is to provide the polishing pad which improved dressing property, maintaining hardness. 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.

  The present invention provides a polishing pad having a polishing layer made of a polyurethane resin foam, wherein the polyurethane resin foam has, as a raw material component, (A) an isocyanate component, (B) a polyol component, and (C) an aromatic having one hydroxyl group. The invention relates to a polishing pad comprising an aromatic compound and / or an aromatic compound having one amino group, and (D) a hollow microsphere.

  The reason why the conventional polishing pad is difficult to dress is that 1) the specific gravity of the polishing layer is high, and 2) there is “stickiness” in the material of the polishing layer itself. It is considered that the specific gravity should be lowered in order to facilitate dressing the surface of the polishing layer, but simply reducing the specific gravity is not preferable because the hardness of the entire polishing pad is lowered and the planarization characteristics are deteriorated. In order to maintain the hardness while reducing the specific gravity, it is conceivable to reduce the molecular weight of the high molecular weight polyol or increase the blending amount of the low molecular weight polyol, but in this case, surface abrasion of the polishing layer is necessary. It becomes larger as described above, and the life of the polishing pad is shortened, or the fuzz on the surface of the polishing layer after dressing tends to be removed immediately at the time of wafer polishing, and the polishing rate tends to decrease.

  The present invention is characterized by using (C) an aromatic compound having one hydroxyl group and / or an aromatic compound having one amino group as the active hydrogen group-containing compound to be reacted with the isocyanate component. Usually, as the active hydrogen group-containing compound to be reacted with the isocyanate component, a compound having two active hydrogen groups such as diol and diamine is used, and two active hydrogen groups of diol (or diamine) and 2 of the isocyanate component are used. A polyurethane resin is obtained by sequentially reacting with two isocyanate groups to form a polymer. On the other hand, since the aromatic compound used in the present invention has only one active hydrogen group in the molecule, polymerization can be partially inhibited. Accordingly, a polymer having a relatively low molecular weight can be dispersed in the polyurethane resin, and the “stickiness” of the polyurethane resin itself can be reduced while maintaining the hardness of the polyurethane resin.

The aromatic compound having one hydroxyl group is preferably a compound represented by the following general formula (1).
^{_{R 1 - (OCH 2 CHR 2}} ) n -OH (1)
(In the formula, R ¹ is an aromatic hydrocarbon group, R ² is hydrogen or a methyl group, and n is an integer of 1 to 5.)

  The aromatic compound having one amino group is preferably aniline or a derivative thereof.

  The content of the aromatic compound having one hydroxyl group and / or the aromatic compound having one amino group is such that the active hydrogen group (hydroxyl group and / or amino group) of the aromatic compound is equivalent to one equivalent of the isocyanate group of the isocyanate component. Group) It is preferable that the amount is equivalent to 0.01 to 0.3. When the active hydrogen group equivalent of the aromatic compound is less than 0.01, the content of the low molecular weight polymer to be dispersed in the polyurethane resin is reduced, so that the “stickiness” of the polyurethane resin itself is difficult to reduce. As a result, it becomes difficult to improve the dressing property of the polishing pad. On the other hand, when it exceeds 0.3, the content of the low molecular weight polymer dispersed in the polyurethane resin is excessively increased, so that the surface wear of the polishing layer is increased more than necessary and the life of the polishing pad is shortened. The fuzz on the surface of the polishing layer after dressing is immediately removed during wafer polishing, and the polishing rate is reduced.

  The cut rate of the polishing pad is preferably 3.5 to 10 μm / min. When the cut rate is less than 3.5 μm / min, the effect of shortening the dressing time is insufficient, and it becomes difficult to improve the manufacturing efficiency of the semiconductor wafer. On the other hand, when the cut rate exceeds 10 μm / min, the surface wear of the polishing layer is increased more than necessary, and the life of the polishing pad is shortened, or fluffing on the surface of the polishing layer after dressing is removed immediately during wafer polishing. Therefore, the polishing rate tends to decrease.

  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 has improved dressing properties while maintaining hardness. When the polishing pad is used, the dressing time can be shortened, so that the manufacturing efficiency of the semiconductor wafer can be remarkably improved.

It is a schematic block diagram which shows an example of the grinding | polishing apparatus used by CMP grinding | polishing.

  The polishing pad of the present invention has a polishing layer made of a polyurethane resin 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 resin contains, as raw material components, (A) an isocyanate component, (B) a polyol component (high molecular weight polyol, low molecular weight polyol, low molecular weight polyamine, etc.), and (C) an aromatic compound having one hydroxyl group and / or Or an aromatic compound having one amino group.

  As the isocyanate component, 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, polymeric MDI, carbodiimide-modified MDI (for example, commercial products) Name Millionate MTL, manufactured by Nippon Polyurethane Industry), 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate and other aromatic diisocyanates, ethylene diisocyanate, 2,2 Aliphatic diisocyanates such as 1,4-trimethylhexamethylene diisocyanate and 1,6-hexamethylene diisocyanate Hexane diisocyanate, cyclohexane diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, isophorone diisocyanate, alicyclic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  A multimerized diisocyanate may be used together with the diisocyanate. The multimerized diisocyanate 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, with isocyanurate type being particularly preferred.

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

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 5000 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 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.

  In addition to the high molecular weight polyols described above 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.

The aromatic compound having one hydroxyl group is not particularly limited as long as it is an aromatic hydrocarbon substituted with one hydroxyl group or an aromatic hydrocarbon substituted with an organic group having one hydroxyl group. Examples of the aromatic hydrocarbon include benzene, naphthalene, anthracene, biphenyl, and indene. In addition, the aromatic hydrocarbon may have a substituent other than the above. Examples of the organic group having one hydroxyl group include an alkanol group and a glycol group. In the present invention, it is particularly preferable to use a compound represented by the following general formula (1).
^{_{R 1 - (OCH 2 CHR 2}} ) n -OH (1)
(In the formula, R ¹ is an aromatic hydrocarbon group, R ² is hydrogen or a methyl group, and n is an integer of 1 to 5.)

  Examples of the compound represented by the general formula (1) include ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, polyoxyethylene monophenyl ether, propylene glycol monophenyl ether, dipropylene glycol monophenyl ether, and polyoxypropylene. Examples thereof include monophenyl ether and polyoxypropylene monomethyl phenyl ether.

  The aromatic compound having one amino group is not particularly limited as long as it is an aromatic hydrocarbon substituted with one amino group or an aromatic hydrocarbon substituted with an organic group having one amino group. Examples of the aromatic hydrocarbon are the same as those described above. Examples of the organic group having one amino group include an aminoalkyl group and an aminoalkenyl group. In the present invention, aniline and derivatives thereof are particularly preferably used.

  Examples of the aromatic compound having one amino group include aniline, methylaniline (toluidine), dimethylaniline (xylidine), methoxyaniline (anisidine), isopropylaniline (cumidine), N-methylaniline, and 2-phenylethylamine. Etc.

  The content of the aromatic compound is such that the active hydrogen group (hydroxyl group and / or amino group) equivalent of the aromatic compound is 0.1 equivalent to 1 equivalent of the isocyanate group of the isocyanate component (including the case of the isocyanate-terminated prepolymer). The amount is preferably from 01 to 0.3, and more preferably from 0.05 to 0.25.

  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 polyol component and the low molecular weight polyamine component described above. These may be used alone or in combination of two or more. In particular, it is preferable to use non-halogen aromatic diamines such as 3,5-bis (methylthio) -2,4-toluenediamine and 3,5-bis (methylthio) -2,6-toluenediamine.

  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.

  In the case of the prepolymer method, the aromatic compound may be previously reacted with an isocyanate component and incorporated into the structure of the isocyanate-terminated prepolymer, or when the isocyanate-terminated prepolymer synthesized from the isocyanate component and the polyol component is cured. You may add to.

  In the case of the prepolymer method, (1) an isocyanate-terminated prepolymer A containing an isocyanate component A, a high molecular weight polyol A, and a low molecular weight polyol; and (2) an isocyanate component B, a high molecular weight polyol B, and the above You may use together the isocyanate terminal prepolymer B obtained by reacting the raw material composition which contains an aromatic compound and whose NCO Index is 3-5.

  The isocyanate component A is preferably toluene diisocyanate and dicyclohexylmethane diisocyanate, and the high molecular weight polyol A is preferably a polyether polyol having a number average molecular weight of 500 to 5,000. NCO Index in particular when producing isocyanate terminal prepolymer A is not restrict | limited, Usually, it is about 1.5-2.5.

  The isocyanate component B is preferably isocyanurate type hexamethylene diisocyanate, and the high molecular weight polyol B is preferably a polyether polyol or polyester polyol having a number average molecular weight of 200 to 5,000. The number average molecular weight is more preferably 200 to 2,000.

  In the present invention, hollow microspheres are used to make the polyurethane resin into a foam. In the case of the prepolymer method, the hollow microspheres may be added to the first component containing the isocyanate-terminated prepolymer or may be added to the second component containing the chain extender, but are uniform in the polyurethane resin foam. It is preferable to add to the first component in order to disperse in the first component.

  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 Nippon Philite Co., Ltd.), Micropearl (manufactured by Matsumoto Yushi Kogyo), ARBOCEL (manufactured by Rettenmeier & Sone), Matsumoto Micro Examples include Sphere F (manufactured by Matsumoto Yushi Seiyaku).

  The amount of hollow microspheres added is not particularly limited, but it is preferably added to the polyurethane resin foam so as to be 1.5 to 2.5% by weight, more preferably 1.8 to 2.3% by weight. is there.

  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 resin foam constituting the polishing pad (polishing layer) will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
1) Mixing step of hollow microspheres (1) Hollow microspheres are added to the first component containing an isocyanate-terminated prepolymer so as to be 1.5 to 2.5% by weight in the polyurethane resin foam, and dispersed 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 component containing 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 case where an aromatic compound having one hydroxyl group is not incorporated into the structure of the isocyanate-terminated prepolymer, the aromatic compound is preferably added when preparing the dispersion because of its slow reaction.

  On the other hand, when the aromatic compound having one amino group is not incorporated in the structure of the isocyanate-terminated prepolymer, the aromatic compound is preferably added when the reaction solution is prepared because the reaction is fast.

  In the production method of polyurethane resin 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. It is.

  You may use the catalyst which accelerates | stimulates well-known polyurethane reactions, such as a 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 resin foam can be manufactured by batch feeding each component into a container and stirring, or by continuously supplying each component to the stirrer and stirring, sending out the reaction liquid and molding It may be a continuous production method for manufacturing products.

  Also, put the prepolymer and hollow microspheres that are the raw material of the polyurethane resin foam into the reaction vessel, and then add the chain extender, stir, and then cast into a casting mold of a predetermined size. A thin sheet may be formed in a method of slicing using a hook-shaped or band saw-shaped slicer, or in the above-described casting step. Alternatively, the raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.

  Moreover, as a manufacturing method of a polyurethane resin 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 together 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 resin foam using a mechanical foaming method will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
1) Foaming step for producing a cell dispersion liquid A hollow microsphere is added to the first component containing an isocyanate-terminated prepolymer so as to be 1.5 to 2.5% by weight in the polyurethane resin foam, and a silicon-based surfactant. Is added to the polyurethane resin foam in an amount of 0.05 to 10% by weight and stirred in the presence of a non-reactive gas to disperse the non-reactive gas as fine bubbles to obtain a cell 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 second component containing a chain extender 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.

  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 resin foam is preferably 20 to 60 μm, more preferably 30 to 50 μm.

  The average cell diameter of bubbles formed by the mechanical foaming method in the polyurethane resin foam is preferably 20 to 70 μm, more preferably 30 to 60 μm. The closed cell ratio of the bubbles is preferably 70% or more, more preferably 80% or more.

  The specific gravity of the polyurethane resin foam is preferably 0.5 to 0.95. When the specific gravity is less than 0.5, the surface strength of the polishing layer decreases, and the planarity of the object to be polished tends to decrease. On the other hand, when the ratio is larger than 0.95, the number of bubbles on the surface of the polishing layer is decreased and the planarity is good, but the polishing rate tends to decrease.

  The hardness of the polyurethane resin foam is preferably 25 to 70 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 25 degrees, the planarity of the object to be polished is lowered. On the other hand, when it exceeds 70 degrees, the planarity is good but the uniformity of the object to be polished is reduced. There is a tendency.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the object to be polished preferably has a surface shape that holds and renews the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and renewing the slurry. However, in order to more efficiently retain the slurry and renew the slurry, it is also a subject of polishing. In order to prevent destruction of the object to be polished due to adsorption with the object, it is preferable that the polishing surface has an uneven structure. 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 hole that does not penetrate, 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 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 polishing object having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire polishing object. 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 average bubble diameter)
A sample obtained 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 was used as a sample for measuring the average cell diameter. 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.) for the obtained image, the total bubble diameter 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 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).

(Measurement of hardness)
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).

(Cut rate measurement)
The prepared polishing pad is attached to a SpeedBam 9B double-side polishing machine, and the surface is evenly rotated using four diamond dressers (Speedfam, # 100 specification, 24 diamond pellets mounted). Dressed up. The dresser load at this time was 100 g / cm ² , the polishing platen rotation speed was 50 rpm, and the dressing time was 20 min. Then, the cut rate (μm / min) was calculated from the thickness of the polishing pad before and after the dress.

Production Example 1
(Prepolymer synthesis)
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 isocyanate-terminated prepolymer A (NCO concentration: 2.22 meq / g).

Example 1
100 parts by weight of the isocyanate-terminated prepolymer A adjusted to 70 ° C. and degassed under reduced pressure in the reaction vessel, 2.4 parts by weight of ethylene glycol monophenyl ether (equivalent of hydroxyl group to 1 equivalent of isocyanate group), and hollow microspheres 3.0 parts by weight (manufactured by Matsumoto Yushi Seiyaku, Matsumoto Microsphere F-105, average cell diameter 35 μm) was added, and the mixture was 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. Thereto, 24.1 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 disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block.
The polyurethane resin foam block heated to about 80 ° C. was sliced using a slicer (manufactured by Amitech, VGW-125) 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. 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.

Examples 2-8, Comparative Example 1
A polishing pad was prepared in the same manner as in Example 1 except that the formulation shown in Table 1 was adopted. The compounds in Table 1 are as follows.
Prepolymer A (NCO concentration: 2.22 meq / g)
N3300: Multimerized 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type)
MOCA: 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Co., Ltd., Iharacamine MT)
・ PhG: Ethylene glycol monophenyl ether (manufactured by Nippon Emulsifier Co., Ltd.)
・ PhDG: Diethylene glycol monophenyl ether (manufactured by Nippon Emulsifier Co., Ltd.)
-PhFG: Propylene glycol monophenyl ether (manufactured by Nippon Emulsifier Co., Ltd.)
F105: hollow microsphere (Matsumoto Yushi Seiyaku, Matsumoto Microsphere F-105, average cell diameter 35 μm)

  The polishing pad of the present invention provides stable and high leveling of flattening of optical materials such as lenses and reflecting mirrors, silicon wafers, aluminum substrates, and materials requiring high surface flatness such as general metal polishing. Can be done with 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. Can be used for

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

Claims (6)

In the polishing pad having a polishing layer made of a polyurethane resin foam, the polyurethane resin foam contains (A) an isocyanate component, (B) a polyol component, (C) an aromatic compound having one hydroxyl group as a raw material component, and / or A polishing pad comprising: an aromatic compound having one amino group; and (D) a hollow microsphere. The polishing pad according to claim 1, wherein the aromatic compound having one hydroxyl group is a compound represented by the following general formula (1).
^{_{R 1 - (OCH 2 CHR 2}} ) n -OH (1)
(In the formula, R ¹ is an aromatic hydrocarbon group, R ² is hydrogen or a methyl group, and n is an integer of 1 to 5.) The polishing pad according to claim 1 or 2, wherein the aromatic compound having one amino group is aniline or a derivative thereof. The content of the aromatic compound having one hydroxyl group and / or the aromatic compound having one amino group is such that the active hydrogen group (hydroxyl group and / or amino group) of the aromatic compound is equivalent to one equivalent of the isocyanate group of the isocyanate component. The polishing pad according to any one of Claims 1 to 3, wherein the polishing pad is an amount such that the equivalent weight is 0.01 to 0.3. The polishing pad according to any one of claims 1 to 4, wherein the cut rate is 3.5 to 10 µm / min. 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.

Images