JP6155018B2 - Polishing pad - Google Patents

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 material to be polished and have a high polishing rate. The flatness and in-plane uniformity of the material 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).

  Moreover, in patent document 3, it is obtained by the prepolymer reaction using a polyol and polyfunctional aromatic isocyanate, and is formed with the isocyanate end-reacted substance which has 4.5 to 8.7 weight% of unreacted NCO, and a hardening | curing agent. A polishing pad comprising a polyurethane polymer material is disclosed.

  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 problem, Patent Document 4 proposes a technique using a multimerized diisocyanate and an aromatic diisocyanate as an isocyanate component which is a raw material of a polyurethane resin foam.

  However, when a 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 material to be polished.

JP 2000-17252 A Japanese Patent No. 3359629 US Patent Application Publication No. 2005/0171225 JP 2006-297582 A

  An object of the present invention is to provide a polishing pad that hardly causes scratches on the surface of a material to be polished and has improved dressing properties. 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 made of a polyurethane resin foam having fine bubbles, and the polyurethane resin foam has an Asker D hardness of 20 to 60 degrees and a wear parameter represented by the following formula: It is related with the polishing pad characterized by containing the polyurethane resin which is 1-3.
Wear parameter = {1 / (tensile breaking strength [MPa] × tensile breaking elongation [%] / 100)} × 100

  Since the polyurethane resin (non-foamed material) which is the material for forming the polishing layer of the present invention is softer and softer than the polyurethane resin used as the material for forming the conventional polishing layer, the surface of the material to be polished has scratches. Hard to occur. In general, a flexible polyurethane resin is excellent in plasticity, so that the wear parameter tends to be small. However, the polyurethane resin, which is a material for forming the polishing layer of the present invention, has a large wear parameter and excellent dressing properties despite being flexible. Therefore, by using the polyurethane resin specified in the present invention as a material for forming the polishing layer, not only can the surface scratch of the material to be polished be suppressed, but also the dressing time can be shortened, and the production efficiency of the material to be polished such as a semiconductor wafer can be reduced. Can be improved.

  When the Asker D hardness of the polyurethane resin is less than 20 degrees, the planarization characteristics of the polishing pad are deteriorated. On the other hand, when it exceeds 60 degrees, scratches are likely to occur on the surface of the material to be polished.

  Further, when the wear parameter of the polyurethane resin is less than 1, the dressing property is inferior, so that the polishing rate is lowered, and the dressing takes too much time, so that the production efficiency of a semiconductor wafer or the like is lowered. On the other hand, if the wear parameter exceeds 3, if the dressing layer is dressed with a dresser, the surface of the polishing layer becomes too rough, so that the surface of the material to be polished is likely to be scratched or the polishing rate is reduced. Or shorten the pad life.

  The polyurethane resin comprises an isocyanate-terminated prepolymer and a chain extender obtained by reacting a prepolymer raw material composition containing a multimerized diisocyanate and aromatic diisocyanate as an isocyanate component, a high molecular weight polyol, and an active hydrogen group-containing low molecular weight compound. It is preferable to contain as a raw material component. A polyurethane resin obtained by a prepolymer method is preferable because of its excellent polishing characteristics.

  The content of the multimerized diisocyanate is preferably 15 to 60% by weight with respect to the total isocyanate component, and the NCO wt% of the isocyanate-terminated prepolymer is preferably 5 to 8% by weight. By adjusting the content of the multivalent diisocyanate and the NCO wt% of the prepolymer to the above ranges, it becomes easy to produce a polyurethane resin having an Asker D hardness of 20 to 60 degrees and an abrasion parameter of 1 to 3.

  In the present invention, the multimerized diisocyanate is preferably a multimerized aliphatic diisocyanate, and the aromatic diisocyanate is preferably toluene diisocyanate. In particular, the multimerized aliphatic diisocyanate is preferably a multimerized hexamethylene diisocyanate. By using these, a polyurethane resin foam can be produced with good handling properties.

  The polyurethane resin foam produced using the polyurethane resin preferably has an Asker D hardness of 10 to 45 degrees. When Asker D hardness is less than 10 degrees, the flatness of the material to be polished tends to decrease. On the other hand, when the angle is larger than 45 degrees, the flatness is good, but the in-plane uniformity of the material to be polished tends to decrease. In addition, scratches are likely to occur on the surface of the material to be polished.

  Moreover, it is preferable that the specific gravity of the polyurethane resin foam produced using the said polyurethane resin is 0.5-1.0. When the specific gravity is less than 0.5, the hardness of the entire polishing layer becomes too low and the flattening characteristics deteriorate, the surface wear of the polishing layer becomes larger than necessary, and the life of the polishing pad is shortened, The fuzz on the surface of the polishing layer after dressing tends to be removed immediately during wafer polishing, and the polishing rate stability tends to be lowered. On the other hand, when the specific gravity exceeds 1.0, it is difficult to sufficiently improve the dressing property of the polishing layer.

  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.

  In the present invention, a polyurethane resin having an Asker D hardness of 20 to 60 degrees and an abrasion parameter of 1 to 3 is used as the polyurethane resin that is a material for forming the polishing layer. The polyurethane resin is low in hardness and flexible. Despite being, it has a feature that the wear parameter is large and the dressing property is excellent. Therefore, by using the polyurethane resin as a polishing layer forming material (polyurethane resin foam forming material), not only can the surface scratch of the material to be polished be suppressed, but also the dressing time can be shortened, and the production efficiency of semiconductor wafers, etc. Can be 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 having fine bubbles. 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).

  The polyurethane resin, which is a material for forming the polishing layer (polyurethane resin foam), has excellent abrasion resistance, and a polymer having desired physical properties can be easily obtained by changing the raw material composition. A particularly preferred material.

  The polyurethane resin comprises an isocyanate component, an active hydrogen group-containing compound (high molecular weight polyol, active hydrogen group-containing low molecular weight compound), a chain extender, and the like.

  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.

  In the present invention, it is preferable to use a multimerized diisocyanate and an aromatic diisocyanate in combination as the isocyanate component. As the diisocyanate forming the multimerized diisocyanate, it is preferable to use an aliphatic diisocyanate, and it is particularly preferable to use 1,6-hexamethylene diisocyanate. The multimerized diisocyanate may be modified by urethane modification, allophanate modification, burette modification or the like. The aromatic diisocyanate is preferably toluene diisocyanate.

  The multimerized diisocyanate is preferably used in an amount of 15 to 60% by weight, more preferably 19 to 55% by weight, based on the total isocyanate component.

  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. 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 polyol, an active hydrogen group-containing low molecular weight compound may be used. The active hydrogen group-containing low molecular weight compound is a compound having a molecular weight of less than 500, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butane. Diol, 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 Low molecular weight polyols such as 2,6,6-tetrakis (hydroxymethyl) cyclohexanol, diethanolamine, N-methyldiethanolamine, and triethanolamine; low molecular weight polyamines such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine; monoethanol Examples include amines, alcohol amines such as 2- (2-aminoethylamino) ethanol, and monopropanolamine. These active hydrogen group-containing low molecular weight compounds may be used alone or in combination of two or more.

  The ratio between the high molecular weight polyol and the active hydrogen group-containing low molecular weight compound is determined by the properties required for the polishing layer produced therefrom.

  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 low molecular weight polyols and low molecular weight polyamines mentioned above. These may be used alone or in combination of two or more.

  In the present invention, a polyurethane resin foam is produced using a polyurethane resin having an Asker D hardness of 20 to 60 degrees and an abrasion parameter of 1 to 3. The Asker D hardness of the polyurethane resin is preferably 25 to 60 degrees, more preferably 30 to 60 degrees.

  Polyurethane resin foam can be manufactured using the polyurethane resin raw material by applying known urethanization technology such as melting method and solution method. However, in consideration of cost, working environment, etc., it is manufactured by melting method. It is preferable to do.

  Polyurethane resin foam can be produced by either the prepolymer method or the one-shot method, but an isocyanate-terminated prepolymer is synthesized beforehand from an isocyanate component and an active hydrogen group-containing compound, and a chain extender is added thereto. The prepolymer method to be reacted is preferable because the obtained polyurethane resin has excellent physical properties.

  When synthesizing an isocyanate-terminated prepolymer, the number of isocyanate groups of the isocyanate component relative to the number of active hydrogen groups (hydroxyl group, amino group) of the active hydrogen group-containing compound is preferably 1.5 to 3.0, more preferably. Is 1.8 to 2.5.

  Moreover, when synthesizing the isocyanate-terminated prepolymer, the NCO wt% is preferably adjusted to 5 to 8 wt%, more preferably 5.8 to 8 wt%.

  The ratio of the isocyanate-terminated prepolymer and the chain extender can be variously changed depending on the molecular weight of each and the desired physical properties of the polishing pad. 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 preferably 0.80 to 1.20, more Preferably it is 0.99-1.15. 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.

  Examples of the method for producing the polyurethane resin foam include a method of adding hollow beads, a mechanical foaming method (including a mechanical floss method), and a chemical foaming method. In addition, although each method may be used together, the mechanical foaming method using the silicon type surfactant which is a copolymer of polyalkylsiloxane and polyether is especially preferable. Examples of the silicon-based surfactant include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8443, B8465 (manufactured by Goldschmidt), and the like. The silicon surfactant is preferably added in an amount of 0.05 to 10% by weight, more preferably 0.1 to 5% by weight, in the polyurethane raw material composition.

  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 producing a closed cell type thermosetting polyurethane resin foam constituting the polishing pad (polishing layer) by the prepolymer 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 silicon-based surfactant is added to the first component containing an isocyanate-terminated prepolymer so as to be 0.05 to 10% by weight in the polyurethane resin foam, and a non-reactive gas is added. And a non-reactive 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 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. .

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

  In the polyurethane resin foam, a known catalyst that promotes a polyurethane reaction such as tertiary amine may be used. The type and 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 and non-reactive gas to the stirring device and stirring, It may be a continuous production method in which a dispersion is sent out to produce a molded product.

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

  The average cell diameter of the polyurethane resin foam is preferably 30 to 100 μm, more preferably 30 to 80 μm. When deviating from this range, the planarity (flatness) of the polished material after polishing tends to decrease.

  The specific gravity of the polyurethane resin foam is preferably 0.5 to 1.0, more preferably 0.5 to 0.8, and particularly preferably 0.7 to 0.8.

  The hardness of the polyurethane resin foam is preferably 10 to 45 degrees, more preferably 15 to 35 degrees, and particularly preferably 20 to 35 degrees as measured by an Asker D hardness meter.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the material 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, the polishing layer is also polished. In order to prevent destruction of the material to be polished due to adsorption with the material, it is preferable that the polished 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 non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

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

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

  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 hardness)
This was performed in accordance with JIS K6253-1997. A non-foamed polyurethane resin sheet and a polyurethane resin foam sheet cut into a size of 2 cm × 2 cm (thickness: arbitrary) were used as samples for hardness measurement, and the temperature was 23 ° C. ± 2 ° C., and the humidity was 50% ± 5%. For 16 hours. At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness after 1 minute was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

(Measurement of tensile strength at break and tensile elongation at break)
The produced non-foamed polyurethane resin sheet was punched out in the shape of dumbbell No. 3 in accordance with JIS K7312-1996 to obtain a sample. The sample was trained for 24 hours at 22 ° C. and 66% RH, and then a tensile test was performed. Tensile breaking strength (MPa) and tensile breaking elongation (%) were measured. As a tensile tester, Autograph AG-X (manufactured by Shimadzu Corporation) was used, and a video extensometer was used. The pulling speed was 50 mm / min.

(Calculation of wear parameters)
The wear parameter was calculated by substituting the tensile rupture strength and tensile rupture elongation values obtained in the above measurement into the following equation.
Wear parameter = {1 / (tensile breaking strength [MPa] × tensile breaking elongation [%] / 100)} × 100

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

(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 polishing amount obtained by polishing a thermal oxide film of 1 μm formed on an 8-inch silicon wafer for 60 seconds. An optical interference type film thickness measuring device (manufactured by Nanometrics, device name: Nanospec) was used for measuring the thickness of the oxide film. As the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.

(Scratch evaluation)
Four 8-inch dummy wafers were polished under the above conditions, and then an 8-inch wafer on which a thermal oxide film having a thickness of 10,000 mm was deposited was polished for 1 minute. Then, using a defect evaluation apparatus (Surfscan SP1) manufactured by KLA Tencor, the number of streaks of 0.19 μm or more on the polished wafer was measured.

(Dressing speed measurement)
The surface of the prepared polishing pad was uniformly dressed while being rotated using a diamond dresser (Asahi Diamond Co., Ltd., M type # 100, 20 cmφ circle). The dresser load at this time was 50 g / cm ² or 450 g / cm ² , the polishing platen rotation speed was 30 rpm, the dresser rotation speed was 15 rpm, and the dressing time was 60 min. Then, the dressing speed was calculated from the thickness of the polishing pad before and after the dressing.

Example 1
(Preparation of non-foamed polyurethane resin sheet)
Toluene diisocyanate (Mitsui Chemicals, TDI-80, mixture of 2,4-isomer / 2,6-isomer = 80/20) 18.2 parts by weight, multimerized 1,6-hexamethylene diisocyanate (Suika) Bayer Urethane Co., Ltd., Sumidur N3300, isocyanurate type) 22.5 parts by weight, polytetramethylene ether glycol (Mitsubishi Chemical Corporation, PTMG1000, hydroxyl value: 112.2 KOHmg / g) 57.1 parts by weight, 1, 4 -Butanediol (manufactured by Nacalai Reagent Co., Ltd., 1,4-BG) (2.2 parts by weight) was added and reacted at 70 ° C. for 4 hours to obtain isocyanate-terminated prepolymer A. In addition, content of multimerized 1, 6- hexamethylene diisocyanate is 55 weight% with respect to all the isocyanate components.
100 parts by weight of the prepolymer A and 19.9 weights of 4,4′-methylenebis (o-chloroaniline) melted at 120 ° C. were put in a planetary stirring and defoaming apparatus and defoamed to prepare a polyurethane raw material composition. The composition was poured into an open mold (casting container) having a length and width of 200 mm and a depth of 2 mm, and post-curing was performed at 100 ° C. for 16 hours to prepare an unfoamed polyurethane resin sheet.

(Preparation of polishing pad)
100 parts by weight of the prepolymer A and 3 parts by weight of a silicon surfactant (manufactured by Goldschmidt, B8465) were added to the polymerization vessel, mixed, adjusted to 80 ° C. and degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. 19.9 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. was added thereto. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed 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 layer. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. 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 2-7, Comparative Examples 1-5
A non-foamed polyurethane resin sheet and a polishing pad were prepared in the same manner as in Example 1 except that the formulations shown in Tables 1 and 2 were adopted. The compounds in Tables 1 and 2 are as follows.
LF600D: manufactured by Chemtura, prepolymer synthesized from toluene diisocyanate and polytetramethylene ether glycol, NCOwt% = 7.25
LF950A: manufactured by Chemtura, prepolymer synthesized from toluene diisocyanate and polytetramethylene ether glycol, NCOwt% = 6.05
L167: manufactured by Chemtura Corporation, a prepolymer synthesized from toluene diisocyanate and polytetramethylene ether glycol, NCOwt% = 6.30

  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: Material to be polished (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (8)

In a polishing pad having a polishing layer made of a polyurethane resin foam having fine bubbles, the polyurethane resin foam has a Asker D hardness of 20 to 60 degrees and a wear parameter represented by the following formula of 1 to 3 A polishing pad comprising a resin.
Wear parameter = {1 / (tensile breaking strength [MPa] × tensile breaking elongation [%] / 100)} × 100   The polyurethane resin comprises an isocyanate-terminated prepolymer and a chain extender obtained by reacting a prepolymer raw material composition containing a multimerized diisocyanate and aromatic diisocyanate as an isocyanate component, a high molecular weight polyol, and an active hydrogen group-containing low molecular weight compound. The polishing pad according to claim 1, which is contained as a raw material component.   The polishing pad according to claim 2, wherein the content of the multimerized diisocyanate is 15 to 60 wt% with respect to the total isocyanate component, and the NCO wt% of the isocyanate-terminated prepolymer is 5 to 8 wt%.   The polishing pad according to claim 2 or 3, wherein the multimerized diisocyanate is a multimerized aliphatic diisocyanate, and the aromatic diisocyanate is toluene diisocyanate.   The polishing pad according to claim 4, wherein the multimerized aliphatic diisocyanate is a multimerized hexamethylene diisocyanate.   The polishing pad according to claim 1, wherein the polyurethane resin foam has an Asker D hardness of 10 to 45 degrees.   The polishing pad according to claim 1, wherein the polyurethane resin foam has a specific gravity of 0.5 to 1.0. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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