JP2008184597A - Method of producing polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently producing a polishing pad with a uniform thickness useful for precisely polishing a material to be polished, such as a semiconductor wafer with high polishing efficiency. <P>SOLUTION: The production method for the polishing pad involves a process of forming a sheet-like molded article by the injection compression molding of a thermoplastic resin. The production of the sheet-like molded article having a groove pattern is carried out, for example, by forming a sheet-like molded product free of a groove pattern by injection compression molding of a thermoplastic resin, and then the groove pattern is formed thereon, or by forming the sheet-like molded article having the groove pattern by injection compression molding of a thermoplastic resin with use of a mold equipped with a stamper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a polishing pad. According to the present invention, it is possible to efficiently manufacture a polishing pad having a uniform thickness that is useful for polishing an object to be polished such as a semiconductor wafer with high accuracy and high polishing efficiency.

  As a polishing pad used for mirror processing of a semiconductor wafer used as a base material for forming an integrated circuit, a fiber-resin composite material such as a velor tone or a suede tone, or a thermoplastic polyurethane resin is generally used as a nonwoven fabric. Sheets that were impregnated and wet-solidified and that had a large compression deformation characteristic and were relatively soft were frequently used.

  In recent years, as semiconductor wafers have been highly integrated and multilayered, there has been an increasing demand for lower prices in addition to higher quality such as higher planarization. Accordingly, the polishing pad is also required to have high functionality such as enabling flattening more than before and to be usable for a long time.

  Conventional relatively soft non-woven polishing pad has good contact with the semiconductor wafer and good holding of the polishing slurry used during polishing, but the surface to be polished is flattened due to its flexibility. Is not enough. In addition, the polishing slurry and polishing scraps generated during polishing are clogged in the voids of the nonwoven fabric, which easily causes scratches on the surface of the semiconductor wafer. Also, when the polishing slurry or polishing debris is clogged, it is difficult to remove these because they have penetrated deep into the gap, resulting in a problem that the life of the polishing pad is shortened. It was.

  On the other hand, a polishing pad using a polymer foam is also known, and since the rigidity is higher than that of a non-woven type polishing pad, it is often used for applications requiring higher leveling. In addition, the polishing pad using the polymer foam having the closed cell structure is relatively easy to clean the polishing pad because the polishing slurry and polishing debris do not penetrate into the back of the gap like the nonwoven fabric type polishing pad. Can withstand long-term use. As such a polymer foam, polyurethane foam is often used because it is particularly excellent in abrasion resistance.

  A polishing pad using foamed polyurethane is usually produced by appropriately grinding or slicing foamed polyurethane. Conventionally, the foamed polyurethane used for the polishing pad has been produced by casting foam curing using a two-component curable polyurethane (see Patent Documents 1 to 4, etc.). However, in this method, it is difficult to make the reaction and foam uniform, and it is difficult to efficiently produce a polishing pad having a uniform thickness.

  As a polishing pad having a uniform thickness, for example, a polishing pad having a thickness variation of 100 μm or less by buffing a sheet obtained by slicing a foamed polyurethane block is known (see Patent Document 5). ). However, this method has a problem that the pad manufacturing process by slicing and buffing is complicated, and the abrasive particles in the buffing remain on the surface of the polishing pad, and scratches occur when polishing a wafer or the like. .

  In addition, a matrix phase made of polystyrene resin, polyolefin resin, or the like is dispersed in a matrix made of polyester resin or the like to form an extruded sheet, and then interfacial peeling is performed by stretching to have pores. A method of making a polishing pad with a uniform thickness is known (see Patent Document 6). However, according to this method, it is difficult to manufacture a polishing pad having a precise thickness accuracy because the thickness unevenness generated when the extruded sheet is manufactured becomes the unevenness of the polishing pad. There was a need to adjust.

JP 2000-178374 A JP 2000-248034 A JP 2001-89548 A Japanese Patent Laid-Open No. 11-322878 JP 2002-192455 A JP 2001-88013 A

  The present invention has been made in view of the above circumstances, and a polishing pad having a uniform thickness, which is useful for polishing an object to be polished such as a semiconductor wafer with high accuracy and high polishing efficiency. The object is to provide a method of manufacturing.

  As a result of repeated studies to achieve the above object, the present inventors have found that the desired polishing pad can be efficiently obtained by molding a thermoplastic resin by a specific molding method, and further studies have been made. The present invention has been completed.

That is, the present invention
[1] A method for producing a polishing pad comprising a step of injection compression molding a thermoplastic resin into a sheet-like molded body,
[2] In the injection compression molding, the compression rate defined by the value obtained by dividing the mold movement width from the half mold open state before injection to the mold clamped state after injection divided by the thickness of the molded product is 5 to 400%. The production method of [1] above,
[3] The production method according to [1] or [2] above, wherein a thermoplastic resin is injection compression molded into a sheet-like molded body having no groove pattern, and then a groove pattern is formed on the sheet-shaped molded body.
[4] The method according to [1] or [2] above, wherein a thermoplastic resin is injection compression molded using a mold equipped with a stamper to obtain a sheet-like molded body having a groove pattern,
[5] Tensile modulus at 50 ° C after the thermoplastic resin is saturated and swelled with water at 50 ° C is 130 to 800 MPa, loss tangent (tan δ) at 50 ° C is 0.2 or less, contact angle with water The production method according to any one of the above [1] to [4], wherein is 80 degrees or less,
[6] The method according to [5], wherein the thermoplastic resin is a thermoplastic polyurethane,
About.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing efficiently the polishing pad with uniform thickness useful in order to grind | polish to-be-polished objects, such as a semiconductor wafer, with high polishing efficiency is provided.

  The manufacturing method of the polishing pad of this invention includes the process of carrying out the injection compression molding of the thermoplastic resin to make a sheet-like molded object. In the injection compression molding method, after the molten resin is injected and filled into the mold, a part of the mold (movable mold) is moved, or the molded product is applied while applying uniform pressure to the entire molten resin using the clamping force. This is a molding method for manufacturing. Specific methods of injection compression molding include, for example, a low link method, a micro mold method, and the like. In the Low Links method, the mold is slightly expanded in advance or the cavity volume is increased by the resin pressure at the time of injection, and after filling the cavity with resin, the mold is completely closed and pressurized, This is a method of molding by pressing a resin. In the micromold method, a part of the cavity is made a movable mold, the mold is injected with the volume of a part of the cavity increased, and after filling the cavity with resin, the movable mold is compressed and molded. Is the method. The micromold method has an advantage that a necessary portion of the molded body can be compressed by a necessary amount. However, in the manufacturing method of the present invention, the entire sheet-shaped molded body can be compressed uniformly, and the residual strain is reduced. Therefore, it is preferable to employ a low link method because a sheet-like molded body having a small thickness variation and a small thickness unevenness can be obtained.

  Compression in injection compression molding is defined by a compression ratio defined by the value obtained by dividing the mold movement width (compression width) from the half mold open state before injection to the mold clamping state after injection divided by the thickness of the molded product. Is done. In the method for producing a polishing pad according to the present invention, the compression rate is preferably in the range of 5% to 400%. When the compression ratio is less than 5%, the obtained sheet-like molded product has a large strain and flatness tends to be lowered. On the other hand, when the compression ratio exceeds 400%, the thickness unevenness of the sheet-like molded product tends to increase. From the viewpoint of obtaining a polishing pad having high flatness and small thickness unevenness, the compression rate is more preferably in the range of 30 to 300%.

Although the cylinder temperature in the injection compression molding depends on the thermoplastic resin used, for example, when using thermoplastic polyurethane, it is preferably in the range of 160 to 250 ° C. When the cylinder temperature is lower than 160 ° C., sufficient fluidity cannot be obtained, and molding defects such as short shots may occur, or distortion may occur in the sheet-like molded product, resulting in reduced flatness. On the other hand, when the cylinder temperature exceeds 250 ° C., the thermoplastic polyurethane may be decomposed and the physical properties of the resulting polishing pad may be lowered.
The mold temperature is preferably in the range of 20 to 80 ° C. When the mold temperature is less than 20 ° C., molding defects such as short shots may occur, or distortion may occur in the sheet-like molded product, resulting in a decrease in flatness. On the other hand, when the mold temperature exceeds 80 ° C., the releasability from the mold tends to decrease.

The thickness of the sheet-like molded product obtained by injection compression molding can be appropriately set depending on the intended polishing pad, but is preferably in the range of 1.0 to 4.0 mm. When the thickness of the sheet-shaped molded body is less than 1.0 mm, the groove formation tends to be difficult when the groove formation described later is performed, while the thickness of the sheet-shaped molded body is 4.0 mm. If it exceeds 1, cooling after injection compression molding takes a long time, and the production efficiency of the polishing pad tends to decrease. From the viewpoint of the ease of groove formation and the production efficiency of the polishing pad, the thickness of the sheet-like molded body is more preferably in the range of 1.5 to 2.5 mm.
Further, the size and shape of the sheet-like molded body can be appropriately set depending on the intended polishing pad, and preferably a circular shape having a diameter of 300 to 1000 mm, and further a circular shape having a diameter of 500 to 900 mm. preferable.

  The sheet-like molded body obtained by injection compression molding can be used as a polishing pad as it is or after groove formation described later is performed, but in order to obtain a sheet-like molded body having smaller thickness spots. Further, the surface of the sheet-like molded body may be further flattened by a method such as buffing or surface cutting using a cutting tool. The thickness unevenness of the sheet-like molded body after the planarization is preferably 30 μm or less, and more preferably 10 μm or less.

  The polishing pad produced according to the present invention preferably has a groove pattern. The polishing pad having the groove pattern is, for example, a sheet-like molded body having no groove pattern by injection compression molding of a thermoplastic resin, and then forming the groove pattern in the sheet-like molded body (Method A), Alternatively, a thermoplastic resin can be injection compression molded using a mold equipped with a stamper to obtain a sheet-like molded body having a groove pattern (Method B), and can be produced from the sheet-like molded body having these groove patterns.

  The stamper in the above-mentioned method B is (1) A method of transferring a pattern by electroforming after directly imparting an uneven pattern to a flat substrate such as a metal plate or glass plate by a method such as etching or machining, (2 ) Apply a photoresist on a flat substrate such as a metal plate or glass plate and expose it through a mask, or directly expose it with a laser beam, etc., then develop it to give a concavo-convex pattern, then electroforming The pattern can be obtained by a method of transferring the pattern. When the stamper is mounted on the mold, it is preferable to provide a heat insulating layer formed of polyimide or the like on the mold side of the stamper because the reproducibility of the groove pattern shape can be further improved.

Examples of the shape of the groove pattern include concentric circles, spirals, cross hatches, XY lattices, hexagons, triangles, and combinations thereof.
The groove depth of the groove pattern is preferably in the range of 0.2 to 2 mm. When the groove depth is less than 0.2 mm, the life of the polishing pad is shortened. On the other hand, when the groove depth is more than 2 mm, the polishing pad becomes flexible, and the polishing characteristics such as level difference relaxation tend to be lowered. There is. From the viewpoint of the life and polishing characteristics of the polishing pad, the groove depth is more preferably in the range of 0.4 to 1.8 mm.

  The groove width of the groove pattern is preferably in the range of 0.3 to 3 mm. When the groove width is less than 0.3 mm, the polishing slurry used at the time of polishing is not efficiently excreted, and the polishing speed tends to decrease. On the other hand, when the groove width exceeds 3 mm, the polishing pad is flexible. As a result, the polishing characteristics such as the step relaxation property tend to be lowered. From the viewpoint of polishing characteristics such as polishing speed and leveling mitigation, the groove width is more preferably in the range of 0.5 to 2.5 mm.

  The groove pitch of the groove pattern is preferably in the range of 1 to 20 mm. When the groove pitch is less than 1 mm, the polishing pad becomes flexible and the polishing characteristics such as the step-relieving property tend to deteriorate. On the other hand, when the groove pitch exceeds 20 mm, the polishing slurry is not efficiently excreted. The polishing rate tends to decrease. From the viewpoint of polishing characteristics such as polishing rate and leveling mitigation, the groove pitch is more preferably in the range of 1.5 to 18 mm.

  Examples of the thermoplastic resin used in the present invention include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polystyrene, polyvinyl chloride, polyester, polyamide, polyurethane and the like. A thermoplastic resin may be used individually by 1 type, or may use 2 or more types together. Among the thermoplastic resins described above, polyurethane (thermoplastic polyurethane) is particularly preferable because the resulting polishing pad has excellent wear resistance.

  The thermoplastic polyurethane can be produced by reacting a polymer diol, an organic diisocyanate, and a chain extender. The thermoplastic polyurethane thus obtained becomes a block copolymer in which a soft segment is composed of a polymer diol and a hard segment is composed of an organic diisocyanate and a chain extender.

  Examples of the polymer diol used for the production of the thermoplastic polyurethane include polyether diol, polyester diol, polycarbonate diol and the like. These polymer diols may be used alone or in combination of two or more. The polymer diol is preferably a polyether diol and / or a polyester diol.

  Examples of the polyether diol include poly (ethylene glycol), poly (propylene glycol), poly (tetramethylene glycol), poly (methyltetramethylene glycol), glycerin-based polyalkylene ether glycol, and the like. These polyether diols may be used alone or in combination of two or more. Among these, poly (ethylene glycol) and poly (tetramethylene glycol) are preferable.

  As the above polyester diol, for example, those produced by direct esterification or transesterification of an ester-forming derivative such as dicarboxylic acid or its ester or anhydride and a low molecular diol according to a conventional method are used. can do.

  Examples of the dicarboxylic acid constituting the polyester diol include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid, and 3-methylpentane diacid. C2-C12 aliphatic dicarboxylic acid such as acid, 2-methyladipic acid, 3-methyladipic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid Long chain aliphatic dicarboxylic acids such as dimerized aliphatic dicarboxylic acids having 14 to 48 carbon atoms (dimer acid) obtained by dimerization of unsaturated fatty acids obtained by fractionation of triglycerides and hydrogenated products thereof (hydrogenated dimer acid); Acid; alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid; terephthalic acid, isophthalic acid, orthophthalic acid, etc. And aromatic dicarboxylic acids. These dicarboxylic acids may be used alone or in combination of two or more. Among these, C2-C12 aliphatic dicarboxylic acid is preferable and adipic acid is more preferable.

  Examples of the low molecular diol constituting the polyester diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, and 1,4-butane. Diol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octane Examples thereof include aliphatic diols such as diol, 1,9-nonanediol, and 1,10-decanediol; alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. These low molecular diols may be used alone or in combination of two or more. Among these, diols having 6 to 12 carbon atoms are preferable, diols having 8 to 10 carbon atoms are more preferable, and diols having 9 carbon atoms are more preferable.

  As said polycarbonate diol, what is obtained by reaction with carbonate compounds, such as low molecular diol, dialkyl carbonate, alkylene carbonate, diaryl carbonate, can be used. As the low molecular weight diol constituting the polycarbonate diol, the low molecular weight diol exemplified above as a constituent component of the polyester diol can be used. Examples of the dialkyl carbonate include dimethyl carbonate and diethyl carbonate. Examples of the alkylene carbonate include ethylene carbonate. Examples of the diaryl carbonate include diphenyl carbonate.

  As the polymer diol, one kind or two or more kinds of polymer diols can be used, but the number average molecular weight of at least one kind of polymer diol is preferably in the range of 1300 to 5000. If the number average molecular weight of the polymer diol is less than 1300, a clear phase separation between the hard segment and the soft segment does not occur, and the resulting thermoplastic polyurethane has a high elastic modulus, and when it is used as a polishing pad, scratches are generated. It tends to occur easily. On the other hand, when the number average molecular weight of the polymer diol exceeds 5000, a thickening phenomenon occurs in the molding machine at the time of extrusion molding or injection molding when producing a thermoplastic polyurethane, and insoluble matter is likely to be generated. You may have to interrupt and clean the inside. Hard segment and soft segment can form a phase-separated structure to produce a thermoplastic polyurethane having an appropriate elastic modulus, and does not cause a thickening phenomenon during extrusion molding or injection molding when producing a thermoplastic polyurethane. Therefore, the number average molecular weight of the at least one polymer diol to be used is more preferably in the range of 1400 to 4000, more preferably in the range of 1500 to 3500, and particularly preferably in the range of 1500 to 2500. The number average molecular weight of the polymer diol referred to in this specification means the number average molecular weight calculated based on the hydroxyl value measured according to JIS K1557.

  As the organic diisocyanate used in the production of the thermoplastic polyurethane, any of organic diisocyanates conventionally used in the production of ordinary polyurethanes may be used. For example, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, Hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, Isopropylidenebis (4-isocyanatocyclohexyl), lysine diisocyanate, 2, -Diisocyanatomethyl caproate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, bis (2-isocyanate) Aliphatic or cycloaliphatic diisocyanates such as natoethyl) -4-cyclohexene; 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-tri Diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4, 4'-diiso Anat biphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, chloro-phenylene-2,4-diisocyanate, and aromatic diisocyanates such as tetramethylxylylene diisocyanate and the like. These organic diisocyanates may be used alone or in combination of two or more. Among these, 4,4'-diphenylmethane diisocyanate is preferable from the viewpoint of wear resistance of the resulting polishing pad.

  As the chain extender used in the production of the thermoplastic polyurethane, any chain extender conventionally used in the production of ordinary polyurethane may be used. As the chain extender, it is preferable to use a low molecular weight compound having a molecular weight of 300 or less having two or more active hydrogen atoms capable of reacting with an isocyanate group, for example, ethylene glycol, diethylene glycol, 1,2-propanediol. 1,3-propanediol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4- Butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,4-bis (β-hydroxyethoxy) benzene, bis ( β-hydroxyethyl) terephthalate, m-xylylene glycol, p-xylylene glycol, 1,4 -Diols such as cyclohexanediol and 1,4-cyclohexanedimethanol; hydrazine, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylene Diamine, dodecamethylenediamine, 1,2-diaminopropane, 3-methylpentamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, o-phenylenediamine, m-phenylene Diamine, p-phenylenediamine, 2,4-diaminochlorobenzene, tolylenediamine, xylylenediamine, 2,2'-diamino-1,1'-binaphthalene, 1,2-dia Noanthraquinone, 1,4-diaminoanthraquinone, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, isophoronediamine, piperazine, adipic acid dihydrazide, isophthalic acid dihydrazide, 4,4'-diamino Diphenylmethane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone 3,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 3,4-diaminobenzophenone, 4,4′-diaminobenzophenone, 4,4′-methy -Bis (2-chloroaniline), 4,4'-diaminobibenzyl, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (4-aminophenoxy) alkane, 1 1, n-bis (4-aminophenoxy) alkane (n is 3 to 10) such as 1,4-bis (4-aminophenoxy) alkane, 1,5-bis (4-aminophenoxy) alkane, 1,2- And diamines such as bis [2- (4-aminophenoxy) ethoxy] ethane, 9,9-bis (4-aminophenyl) fluorene, 4,4′-diaminobenzanilide, and the like. It is. These chain extenders may be used individually by 1 type, or may use 2 or more types together. Among these, 1,4-butanediol and 1,4-cyclohexanedimethanol are preferable.

  The thermoplastic polyurethane can be produced by melt-kneading the above polymer diol, organic diisocyanate and chain extender in a predetermined ratio. The use ratio of each of the above components is appropriately determined in consideration of the physical properties to be imparted to the thermoplastic polyurethane, the wear resistance, etc., but it is organic with respect to 1 mol of active hydrogen atoms contained in the polymer diol and the chain extender. It is preferable to use each component in such a ratio that the isocyanate group contained in the diisocyanate is 0.95 to 1.3 mol. If the proportion of isocyanate group is lower than 0.95 mol, the mechanical strength and abrasion resistance of the resulting polishing pad may be reduced. On the other hand, if it exceeds 1.3 mol, the productivity and storage stability of thermoplastic polyurethane are reduced. May decrease. From the viewpoints of mechanical strength, abrasion resistance, and thermoplastic polyurethane productivity and storage stability of the resulting polishing pad, the polymer diol, organic diisocyanate and chain extender are included in the polymer diol and chain extender. More preferably, the isocyanate group contained in the organic diisocyanate is used in a ratio in the range of 0.96 to 1.10, and the ratio in the range of 0.97 to 1.05 with respect to 1 mol of the active hydrogen atom. Further preferred.

  The thermoplastic polyurethane can be produced by any of the pre-polymer method and the one-shot method using the above-mentioned polymer diol, organic diisocyanate, and chain extender and utilizing a known urethanization reaction. The thermoplastic polyurethane is preferably produced by a method of melt polymerization substantially in the absence of a solvent, and more preferably produced by a method of continuous melt polymerization using a multi-screw extruder.

  The thermoplastic resin used in the present invention preferably has a tensile elastic modulus at 50 ° C. of 130 to 800 MPa after saturated swelling with 50 ° C. water. If the tensile elastic modulus at 50 ° C. after the saturated swelling of the thermoplastic resin used with water at 50 ° C. is less than 130 MPa, the resulting polishing pad becomes too soft and the flatness of the surface to be polished decreases. Or the polishing efficiency may decrease. On the other hand, if it exceeds 800 MPa, scratches are likely to occur during polishing. From the viewpoint of the flatness of the surface to be polished and the suppression of scratches, the tensile elastic modulus at 50 ° C. of the thermoplastic resin used after saturation swelling with 50 ° C. water is more preferably in the range of 180 to 750 MPa. Preferably, the range of 200 to 700 MPa is more preferable.

  The loss tangent (tan δ) at 50 ° C. of the thermoplastic resin used in the present invention is preferably 0.2 or less. If the loss tangent (tan δ) at 50 ° C. of the thermoplastic resin used exceeds 0.2, the resulting polishing pad becomes too soft, so that the flatness of the surface to be polished is lowered, or the polishing efficiency is lowered. There is a case. From the viewpoint of flatness of the surface to be polished, the loss tangent (tan δ) of the thermoplastic resin at 50 ° C. is more preferably 0.15 or less, and further preferably 0.13 or less. The loss tangent (tan δ) is a ratio (E ″ / E ′) between the loss elastic modulus (E ″) and the storage elastic modulus (E ′).

  The contact angle with water of the thermoplastic resin used in the present invention is preferably 80 degrees or less. If the contact angle of the thermoplastic resin used with water exceeds 80 degrees, scratches are likely to occur when polishing is performed using the resulting polishing pad. From the viewpoint of suppressing scratching during polishing, the contact angle of the thermoplastic resin with water is more preferably 75 ° or less.

  Also for the thermoplastic polyurethane preferably used as the thermoplastic resin, the tensile modulus at 50 ° C. after saturation swelling with 50 ° C. water is 130 to 800 MPa, the loss tangent (tan δ) at 50 ° C. is 0.2 or less, The contact angle with water is preferably 80 degrees or less. Such thermoplastic polyurethane uses, for example, a polymer diol having a number average molecular weight of 1400 to 5000, and the content of nitrogen atoms derived from isocyanate groups in the obtained thermoplastic polyurethane is 4.8% by mass or more and 6. It can be produced by reacting a polymer diol, an organic diisocyanate and a chain extender so as to be less than 0% by mass.

  The thermoplastic resin used in the present invention includes an organic filler, an inorganic filler, a crosslinking agent, a crosslinking accelerator, a crosslinking aid, a softening agent, and a tackifier within a range not impairing the effects of the present invention. , Thickener, processing aid, lubricant, blooming inhibitor, mold release agent, adhesion promoter, crystal nucleating agent, anti-aging agent, heat stabilizer, weathering stabilizer, antioxidant, antistatic agent, conductive agent Additives such as colorants, flame retardants, flame retardant aids, and pyrolytic foaming agents (chemical foaming agents) can be blended. The blending amount of these additives is preferably 50% by mass or less, more preferably 20% by mass or less, and more preferably 5% by mass or less, based on the total mass of the thermoplastic resin blended with the additive. More preferably.

  The polishing pad obtained by the production method of the present invention can be used for chemical mechanical polishing (CMP) together with a polishing slurry known per se. The polishing slurry contains components such as a liquid medium such as water and oil; an abrasive such as silica, aluminum oxide, cerium oxide, zirconium oxide, and silicon carbide; a base, an acid, and a surfactant. Moreover, when performing CMP, you may use lubricating oil, a coolant, etc. together with polishing slurry as needed.

  CMP can be carried out by using a known CMP apparatus and bringing the surface to be polished and the polishing pad into contact with each other at a constant speed under a pressure for a certain period of time via a polishing slurry. The article to be polished is not particularly limited, and examples thereof include quartz, silicon, glass, an optical substrate, an electronic circuit substrate, a multilayer wiring substrate, and a hard disk. In particular, the object to be polished is preferably a silicon wafer or a semiconductor wafer. Specific examples of semiconductor wafers include, for example, insulating films such as silicon oxide, silicon oxyfluoride, and organic polymers, wiring metal films such as copper, aluminum, and tungsten, and barrier metals such as tantalum, titanium, tantalum nitride, and titanium nitride. Examples thereof include those having a film or the like on the surface.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The physical properties of the thermoplastic polyurethane and polishing pad described in the examples were evaluated by the following methods.

<Evaluation of physical properties of thermoplastic polyurethane>
A tensile elastic modulus thermoplastic polyurethane at 50 ° C. after saturated swelling with water at 50 ° C. is formed into a film having a thickness of 300 μm by a hot press method, and a No. 2 type test piece (JIS K7113) is punched out from the film. What was immersed in warm water for 3 days was used as a water swelling sample. Using the sample, “Autograph AG5000” manufactured by Shimadzu Corporation, and mounting the sample at a distance between chucks of 40 mm, left standing at an ambient temperature of 50 ° C. for 5 minutes, and then tensile elasticity at a pulling speed of 50 mm / min. The rate was measured.

Loss tangent at 50 ° C (tan δ)
Using thermoplastic polyurethane as an injection-molded sheet having a thickness of 2 mm and using a test piece obtained by heat-treating the sheet at 90 ° C. for 5 hours, a dynamic viscoelasticity measuring device “DVE Rheospectr” manufactured by Rheology Co., Ltd. is used. The storage elastic modulus (E ′) and the loss elastic modulus (E ″) were determined by measuring the dynamic viscoelastic modulus at a predetermined temperature at a frequency of 11 Hz. The loss tangent (tan δ, E ″ / E ′) was calculated.

A contact angle thermoplastic polyurethane with water was formed into a film having a thickness of 300 μm by a hot press method, and a sample of the film was allowed to stand at 20 ° C. and 65% RH for 3 days. The contact angle with water was measured.

<Evaluation of physical properties of polishing pad>
Polishing rate and number of scratches (polishing characteristics evaluation)
The polishing pads obtained in the following Examples and Comparative Examples were installed in a CMP polishing apparatus “PPO-60S” manufactured by Nomura Seisakusho Co., Ltd., and a diamond dresser “MEC100-L” manufactured by Mitsubishi Materials Corporation was used. The surface of the polishing pad was ground (seasoned) for 18 minutes at 8 kgf / cm ² and a dresser rotational speed of 110 revolutions / minute.
Next, a solution obtained by diluting Cabot polishing slurry SS25 twice with distilled water under the conditions of a platen rotation speed of 50 rotations / minute, a head rotation speed of 49 rotations / minute, a polishing pressure of 45 KPa, and a polishing time of 100 seconds is 120 mL / A silicon wafer having an oxide film surface of 8 inches in diameter was polished for 100 seconds while supplying an amount of minutes. The polishing rate on the surface of the silicon wafer after polishing was evaluated by measuring the change in film thickness before and after polishing using an ellipsometer “DVA-36LS” manufactured by Mizoji Optical Co., Ltd. Further, the number of scratches having a size of 0.16 μm or more present on the surface of the polished silicon wafer was measured using “Surfscan SP1” manufactured by KLA-Tencor, and used as the number of scratches.

[Production Example 1]
Production of Thermoplastic Polyurethane (PU-1) Poly (tetramethylene glycol) [abbreviation: PTMG2000] with number average molecular weight 2000, Poly (2-methyl-1,8-octamethylene-co-nonamethylene adipate with number average molecular weight 2000 ) [Abbreviation: PNOA, molar ratio of nonamethylene unit to 2-methyl-1,8-octamethylene unit = 7 to 3], 1,4-cyclohexanedimethanol [abbreviation: CHDM], 1,4-butanediol [ Abbreviation: BD], and 4,4′-diphenylmethane diisocyanate [abbreviation: MDI] in a mass ratio of PTMG2000: PNOA: CHDM: BD: MDI of 20.1: 8.4: 5.7: 14.2: 51. .6 (nitrogen atom content: 5.8% by mass), and the total supply amount is 300 g / min. As shown in the figure, it is continuously supplied to a twin-screw extruder (30 mmφ, L / D = 36, cylinder temperature: 75 to 260 ° C.) that is coaxially rotated by a metering pump, and subjected to continuous melt polymerization and thermoplasticity. A polyurethane was produced. The resulting thermoplastic polyurethane melt was continuously extruded into water in a strand form, then chopped into pellets with a pelletizer, and the pellets were dehumidified and dried at 70 ° C. for 20 hours to obtain a thermoplastic polyurethane (hereinafter referred to as “polyurethane polyurethane”). This was called PU-1. Table 1 shows the tensile modulus of elasticity at 50 ° C., loss tangent (tan δ) at 50 ° C., and contact angle with water after saturation swelling of PU-1 with 50 ° C. water.

[Production Example 2]
Production of thermoplastic polyurethane (PU-2) PNOA [molar ratio of nonamethylene units to 2-methyl-1,8-octamethylene units = 7 to 3], poly (ethylene glycol) having a number average molecular weight of 600 [abbreviation: PEG600 ], CHDM, BD, and MDI have a PNOA: PEG600: CHDM: BD: MDI mass ratio of 31.0: 5.0: 2.4: 13.6: 48.0 (nitrogen atom content: 5 .4 mass%) and a twin-screw extruder (30 mmφ, L / D = 36, cylinder) rotating coaxially with a metering pump so that the total supply amount is 300 g / min. (Temperature: 75-260 ° C.) and a continuous melt polymerization was carried out to produce a thermoplastic polyurethane. The resulting thermoplastic polyurethane melt was continuously extruded into water in a strand form, then chopped into pellets with a pelletizer, and the pellets were dehumidified and dried at 70 ° C. for 20 hours to obtain a thermoplastic polyurethane (hereinafter referred to as “polyurethane polyurethane”). This was referred to as PU-2). Table 1 shows the tensile modulus of elasticity at 50 ° C., the loss tangent (tan δ) at 50 ° C., and the contact angle with water after saturation swelling of PU-2 with water at 50 ° C.

[Example 1]
The PU-1 pellets were charged into an injection compression molding machine “MDIP1400” manufactured by Meiki Seisakusho Co., Ltd., having a nickel layer with a thickness of 300 μm on the surface, and a heat insulating layer made of polyimide with a thickness of 400 μm, forming a groove. In a 50 ° C. mold equipped with a laminated structure that does not have a pattern for filling, a cylinder temperature of 170 to 220 ° C. and a nozzle temperature of 220 ° C. are filled and compressed in the mold at a compression ratio of 140%. A circular sheet-like molded body having a thickness of 2 mm (thickness unevenness 50 μm) and a diameter of 510 mm was produced.
The obtained circular sheet-like molded body was mounted on a surface processing apparatus having a rotary surface plate, and the surface was ground with a metal tool. A sheet having a thickness of 10 μm was obtained by grinding 20 μm by one grinding and grinding twice. The obtained sheet was mounted on a groove forming apparatus to form an XY lattice type groove having a groove depth of 1.2 mm, a groove width of 2.2 mm, and a groove pitch of 15 mm to obtain a polishing pad. Table 2 shows the ease of production of the polishing pad and the evaluation results of the polishing characteristics.

[Example 2]
A pellet of PU-1 was charged into an injection compression molding machine “MDIP1400” manufactured by Meiki Seisakusho Co., Ltd., and a concentric convex pattern having a height of 0.4 mm, a width of 0.5 mm, and a pitch of 1.5 mm was formed on the surface. After filling with a cylinder temperature of 170-220 ° C. and a nozzle temperature of 220 ° C. in a 50 ° C. mold equipped with a heat insulation stamper having a nickel layer of 600 μm thickness on the surface and a heat insulation layer made of polyimide of 400 μm thickness Compressed in a mold at a compression rate of 140% to produce a circular sheet-like molded body having a thickness of 2 mm and a diameter of 510 mm.
The obtained circular sheet-like molded product has a concentric groove pattern with a groove depth of 0.4 mm, a groove width of 0.5 mm, and a groove pitch of 1.5 mm, The thickness unevenness was 30 μm and was used as a polishing pad as it was. Table 2 shows the ease of production of the polishing pad and the evaluation results of the polishing characteristics.

[Example 3]
The PU-2 pellets are charged into an MDMP1400 injection compression molding machine manufactured by Meiki Seisakusho Co., Ltd., having a nickel layer with a thickness of 300 μm on the surface and a heat insulating layer made of polyimide with a thickness of 400 μm, forming a groove. In a 50 ° C. mold equipped with a laminated structure that does not have a pattern for filling, a cylinder temperature of 170 to 220 ° C. and a nozzle temperature of 220 ° C. are filled and compressed in the mold at a compression ratio of 140%. A circular sheet-like molded body having a thickness of 2 mm (thickness unevenness 50 μm) and a diameter of 510 mm was produced.
The obtained circular sheet-like molded body was mounted on a surface processing apparatus having a rotary surface plate, and the surface was ground with a metal tool. A sheet having a thickness of 10 μm was obtained by grinding 20 μm by one grinding and grinding twice. The obtained sheet was mounted on a groove forming apparatus to form a concentric groove having a groove depth of 1.0 mm, a groove width of 0.5 mm, and a groove pitch of 1.5 mm to obtain a polishing pad. Table 2 shows the ease of production of the polishing pad and the evaluation results of the polishing characteristics.

[Comparative Example 1]
Rolls with a gap interval of 1.8 mm were prepared by feeding PU-1 pellets into a single screw extruder (90 mmφ), extruding from a T-die at a cylinder temperature of 215 to 225 ° C and a die temperature of 225 ° C, and adjusting the temperature to 60 ° C. Was made into a sheet-like molded body having a thickness of 2 mm (thickness unevenness 300 μm).
The obtained sheet-like molded body was mounted on a surface processing apparatus having a rotary surface plate, cut into a circular shape with a diameter of 510 mm with a metal cutter, and then the surface was ground with a metal tool. A sheet having a thickness of 10 μm was obtained by grinding 20 μm by one grinding and grinding 15 times. The obtained sheet was mounted on a groove forming apparatus to form an XY lattice type groove having a groove depth of 1.2 mm, a groove width of 2.2 mm, and a groove pitch of 15 mm to obtain a polishing pad. Table 2 shows the ease of production of the polishing pad and the evaluation results of the polishing characteristics.

[Comparative Example 2]
The pellets of PU-1 were put into an injection molding machine “1450em” manufactured by Mitsubishi Heavy Industries Plastic Technology Co., Ltd., and filled in a 50 ° C. mold at a cylinder temperature of 170 to 220 ° C. and a nozzle temperature of 220 ° C., with a thickness of 2 mm. A circular sheet-like molded body having a diameter of 510 mm was produced. The obtained sheet-like molded product was low in flatness due to distortion generated in injection molding, and could not be evaluated as a polishing pad.

[Comparative Example 3]
The PU-1 pellets were loaded into a press-type compression molding machine with a side cylinder manufactured by Kansai Roll Co., Ltd. After pressing at 220 ° C, the mold was cooled to 50 ° C and a circular sheet with a thickness of 2 mm and a diameter of 510 mm A molded body was produced. At this time, it took 15 minutes to cool from 220 ° C. to 50 ° C., and during that time, the molecular weight decreased due to deterioration of the thermoplastic polyurethane, and the physical properties of the sheet-like molded product significantly decreased. There wasn't.

  As is apparent from Table 2, in Examples 1 to 3, a polishing pad with a small thickness variation was manufactured despite the small number of grindings in the manufacturing process of the polishing pad, and polishing with a small thickness variation was performed. It can be seen that the pad is easily manufactured. On the other hand, in Comparative Example 1, since an extrusion molding machine was used, the obtained circular sheet-shaped molded body had large thickness spots, and it was necessary to grind as many as 15 times in order to reduce the thickness spots. This is not an efficient production.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing efficiently the polishing pad with uniform thickness useful in order to grind | polish to-be-polished objects, such as a semiconductor wafer, with high polishing efficiency is provided.

Claims (6)

  A method for producing a polishing pad comprising a step of injection compression molding a thermoplastic resin into a sheet-like molded body.   In the injection compression molding, the compression ratio defined by the value obtained by dividing the mold movement width from the half mold open state before injection to the mold clamped state after injection by the thickness of the molded product is 5 to 400%. Item 2. The manufacturing method according to Item 1.   The manufacturing method according to claim 1 or 2, wherein a thermoplastic resin is injection compression molded to form a sheet-like molded body having no groove pattern, and thereafter the groove pattern is formed on the sheet-shaped molded body.   The production method according to claim 1 or 2, wherein a thermoplastic resin is injection compression molded using a mold equipped with a stamper to form a sheet-like molded body having a groove pattern.   The thermoplastic resin has a tensile modulus at 130 ° C. of 130 to 800 MPa after saturation swelling with water at 50 ° C., a loss tangent (tan δ) at 50 ° C. of 0.2 or less, and a contact angle with water of 80 degrees. It is the following, The manufacturing method in any one of Claims 1-4.   The manufacturing method according to claim 5, wherein the thermoplastic resin is a thermoplastic polyurethane.