JP5738729B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad (for rough polishing or finish polishing) used for polishing surfaces of optical materials such as lenses and reflection mirrors, silicon wafers, and aluminum substrates. In particular, the polishing pad of the present invention is suitably used as a polishing pad for finishing.

  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 having open cells, wherein the polyurethane resin foam contains (A) an isocyanate component, (B) a polyol component, and (C) a hydroxyl group as raw material components. The present invention relates to a polishing pad comprising an aromatic compound having one and / or an aromatic compound having one amino group.

  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 having open cells. 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 base material layer or 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. Of these, aromatic diisocyanate is preferably used, and carbodiimide-modified MDI is more preferably used.

  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 those usually used in the technical field of polyurethane. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol, and then reacting the obtained reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate And polymer polyol which is a polyether polyol in which polymer particles are dispersed.These may be used alone or in combination of two or more.

  In order to make the polyurethane resin foam into an open-cell structure, it is preferable to use a polymer polyol, and it is particularly preferable to use a polymer polyol in which polymer particles made of acrylonitrile and / or a styrene-acrylonitrile copolymer are dispersed. The polymer polyol is preferably contained in the total high molecular weight polyol in an amount of 20 to 100% by weight, more preferably 30 to 60% by weight.

  Moreover, it is preferable to contain the said high molecular weight polyol (a polymer polyol is included) 60 to 95 weight% in a polyol component, More preferably, it is 70 to 90 weight%. By using a specific amount of the high molecular weight polyol, the cell membrane is easily broken, and an open cell structure is easily formed.

  Of the high molecular weight polyols, it is preferable to use a high molecular weight polyol having a hydroxyl value of 30 to 350 mgKOH / g. The hydroxyl value is more preferably 100 to 320 mgKOH / g. When the hydroxyl value is less than 30 mgKOH / g, the amount of hard segment of the polyurethane resin tends to decrease and the durability tends to decrease. When it exceeds 350 mgKOH / g, the degree of crosslinking of the polyurethane resin becomes too high. Tend to be brittle.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 3500 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 tends to be a brittle polymer. Therefore, the polishing layer made of this polyurethane resin foam becomes too hard, and scratches are likely to occur on the surface of the object to be polished. On the other hand, when the number average molecular weight exceeds 3,500, a polyurethane resin using the number average molecular weight becomes too soft. Therefore, the durability of the polishing layer made of this polyurethane resin foam tends to deteriorate.

  Along with high molecular weight polyol, 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, tri Methylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclo Hexanol, diethanolamine, N- methyldiethanolamine, and low molecular weight polyols such as triethanolamine may be used in combination. 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.

  Among these, it is preferable to use a low molecular weight polyol having a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight polyamine having an amine value of 400 to 1870 mgKOH / g. The hydroxyl value is more preferably 900 to 1500 mgKOH / g, and the amine value is more preferably 400 to 950 mgKOH / g. When the hydroxyl value is less than 400 mgKOH / g or the amine value is less than 400 mgKOH / g, the effect of improving the formation of open cells tends to be insufficient. On the other hand, when the hydroxyl value exceeds 1830 mgKOH / g or the amine value exceeds 1870 mgKOH / g, scratches tend to occur on the wafer surface. In particular, it is preferable to use diethylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, or trimethylolpropane.

  In order to make the polyurethane resin foam into an open-cell structure, the low molecular weight polyol, the low molecular weight polyamine and the alcohol amine are preferably contained in a total of 5 to 40% by weight, more preferably 10 to 30% by weight in the polyol component. It is. By using a specific amount of the low molecular weight polyol or the like, not only the bubble film is easily broken and it becomes easy to form open cells, but also the mechanical properties of the polyurethane resin foam are improved.

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.

  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.

  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 a polyol component, and this is reacted with a chain extender. The prepolymer method is preferable because the physical properties of the resulting polyurethane resin are excellent.

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

  The polyurethane resin foam, which is a material for forming the polishing layer of the present invention, can be produced by a mechanical foaming method (including a mechanical floss method) using a silicon surfactant.

  In particular, a mechanical foaming method using a silicon surfactant which is a polyalkylsiloxane or a copolymer of an alkylsiloxane and a polyetheralkylsiloxane is preferable. Examples of suitable silicon surfactants include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8443, B8465 (manufactured by Goldschmidt), and the like.

  The silicon-based surfactant is preferably added to the polyurethane resin foam in an amount of 0.1 to 10% by weight, more preferably 0.5 to 7% by weight.

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

  An example of a method for producing a polyurethane resin foam constituting the polishing layer will be described below. The manufacturing method of this polyurethane resin foam has the following processes.

  (1) The first component obtained by adding a silicon surfactant to an isocyanate-terminated prepolymer obtained by reacting an isocyanate component and a high molecular weight polyol is mechanically stirred in the presence of a non-reactive gas, and the non-reactive gas is removed. Disperse as fine bubbles to obtain a cell dispersion. Then, a second component containing a chain extender and the like is added to the cell dispersion and mixed to prepare a cell-dispersed urethane composition. A catalyst may be appropriately added to the second component.

  (2) A silicon-based surfactant was added to at least one of the first component containing the isocyanate component (or isocyanate-terminated prepolymer) and the second component containing the active hydrogen group-containing compound, and the silicon-based surfactant was added. The components are mechanically stirred in the presence of a non-reactive gas, and the non-reactive gas is dispersed as fine bubbles to obtain a bubble dispersion. Then, the remaining components are added to the cell dispersion and mixed to prepare a cell-dispersed urethane composition.

  (3) A silicon-based surfactant is added to at least one of the first component containing the isocyanate component (or isocyanate-terminated prepolymer) and the second component containing the active hydrogen group-containing compound, and the first component and the second component are added. Is mechanically stirred in the presence of a non-reactive gas, and the non-reactive gas is dispersed as fine bubbles to prepare a cell-dispersed urethane composition.

  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 may be added to the second component.

  In the case of the one-shot method, the aromatic compound may be added to the first component, the second component, or both.

  The cell dispersed urethane composition may be prepared by a mechanical floss method. The mechanical floss method is a method in which raw material components are put into a mixing chamber of a mixing head and a non-reactive gas is mixed and mixed and stirred by a mixer such as an Oaks mixer to make the non-reactive gas into a fine bubble state in the raw material mixture. It is a method of dispersing in. The mechanical floss method is a preferable method because the density of the polyurethane resin foam can be easily adjusted by adjusting the amount of the non-reactive gas mixed therein. Moreover, since the polyurethane resin foam having substantially spherical fine cells can be continuously molded, the production efficiency is good.

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

  As a stirring device for dispersing the non-reactive gas in the form of fine bubbles, a known stirring device can be used without any particular limitation. Specifically, a homogenizer, a dissolver, a two-axis planetary mixer (planetary mixer), a mechanical A floss foaming machine etc. are illustrated. 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 order to obtain the target polyurethane resin foam, the rotational speed of the stirring blade is preferably 500 to 2000 rpm, more preferably 800 to 1500 rpm. The stirring time is appropriately adjusted according to the target density.

  In addition, it is also a preferable aspect that the stirring for preparing the cell dispersion in the foaming step and the stirring for mixing the first component and the second component use different stirring devices. The agitation in the mixing step may not be agitation that forms bubbles, and it is preferable to use an agitation 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 for preparing the bubble dispersion and the mixing step for mixing each component, and the stirring conditions such as adjusting the rotation speed of the stirring blades are adjusted as necessary. It is also suitable to use after adjustment.

  Thereafter, the cell-dispersed urethane composition prepared by the above method is applied onto a release sheet, and the cell-dispersed urethane composition is cured to form a polyurethane resin foam.

  In addition, the cell-dispersed urethane composition prepared by the above method is applied on a base material layer or cushion layer, the cell-dispersed urethane composition is cured, and the polyurethane resin foam (polishing) is directly applied on the base material layer or cushion layer. Layer) may be formed.

  The substrate layer is not particularly limited. For example, plastic films such as polypropylene, polyethylene, polyester, polyamide, and polyvinyl chloride, polymer resin foams such as polyurethane foam and polyethylene foam, rubber properties such as butadiene rubber and isoprene rubber. Examples thereof include resins and photosensitive resins. Among these, it is preferable to use polymer resin foams such as plastic films such as polypropylene, polyethylene, polyester, polyamide, and polyvinyl chloride, polyurethane foam, and polyethylene foam. Moreover, you may use a double-sided tape and a single-sided adhesive tape (a single-sided adhesive layer is for affixing on a platen) as a base material layer.

  The base material layer is preferably as hard as a polyurethane resin foam or harder in order to impart toughness to the polishing pad. Moreover, the thickness of the base material layer (the base material in the case of double-sided tape and single-sided adhesive tape) is not particularly limited, but is preferably 20 to 1000 μm, more preferably 50 to 50 μm from the viewpoint of strength, flexibility, and the like. 800 μm.

  The cushion layer supplements the characteristics of the polishing layer. The cushion layer is necessary in order to achieve 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 layer.

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

  As a method for applying the cell-dispersed urethane composition onto the base material layer, for example, a roll coater such as gravure, kiss, or comma, a die coater such as slot or phanten, a squeeze coater, or a curtain coater is adopted. Any method may be used as long as a uniform coating film can be formed on the base material layer.

  Heating and post-curing the polyurethane resin foam that has reacted until the cell-dispersed urethane composition is applied to the base layer and no longer flows has the effect of improving the physical properties of the polyurethane resin foam. Is preferred. Post-cure is preferably performed at 30 to 80 ° C. for 10 minutes to 6 hours, and it is preferable to perform at normal pressure because the bubble shape becomes stable.

  In the production of a polyurethane resin foam, a known catalyst that promotes a polyurethane reaction, such as a tertiary amine, may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for application on the base material layer after the mixing step of each component.

  The polyurethane resin foam may be manufactured by a batch method in which each component is weighed and put into a container and mechanically stirred, or each component and a non-reactive gas are continuously supplied to a stirring device to mechanically stir. In addition, a continuous production method in which the cell-dispersed urethane composition is sent out to produce a molded product may be used.

  Moreover, after forming a polyurethane resin foam on a base material layer, or simultaneously with forming a polyurethane resin foam, it is preferable to adjust the thickness of a polyurethane resin foam uniformly. The method for uniformly adjusting the thickness of the polyurethane resin foam is not particularly limited, and examples thereof include a method of buffing with an abrasive and a method of pressing with a press plate.

  Moreover, the cell-dispersed urethane composition prepared by the above method is applied on the base material layer, and a release sheet is laminated on the cell-dispersed urethane composition. Thereafter, the polyurethane foam may be formed by curing the cell-dispersed urethane composition while making the thickness uniform by a pressing means.

  On the other hand, the cell-dispersed urethane composition prepared by the above method is applied onto a release sheet, and a base material layer is laminated on the cell-dispersed urethane composition. Thereafter, the polyurethane foam may be formed by curing the cell-dispersed urethane composition while making the thickness uniform by a pressing means.

  The material for forming the release sheet is not particularly limited, and examples thereof include general resin and paper. The release sheet preferably has a small dimensional change due to heat. The surface of the release sheet may be subjected to a release treatment.

  The pressing means for making the thickness of the sandwich sheet composed of the base material layer, the cell-dispersed urethane composition (cell-dispersed urethane layer), and the release sheet is not particularly limited. For example, the thickness may be constant by a coater roll, a nip roll, or the like. The method of compressing is mentioned. In consideration of the fact that the bubbles in the foam are increased by about 1.2 to 2 times after compression, (coating or nip clearance)-(base layer and release sheet thickness) = (after curing) The thickness of the polyurethane resin foam is preferably 50 to 85%.

  Then, after making the thickness of the sandwich sheet uniform, the reacted polyurethane resin foam is heated until it does not flow, and post-cure to form a polishing layer. Post cure conditions are the same as described above.

  Thereafter, the release sheet on the upper surface side or the lower surface side of the polyurethane resin foam is peeled to obtain a polishing pad. In this case, since the skin layer is formed on the polyurethane resin foam, the skin layer is removed by buffing or the like. Further, when the polyurethane resin foam is formed by the mechanical foaming method as described above, the variation in bubbles is smaller on the lower surface side than on the upper surface side of the polyurethane resin foam. Therefore, when the release sheet on the lower surface side is peeled off and the lower surface side of the polyurethane resin foam is used as the polishing surface, the polishing surface has less variation in bubbles, and thus the stability of the polishing rate is further improved.

  Alternatively, the polyurethane resin foam (polishing layer) may not be formed directly on the base material layer or the cushion layer, and the polishing layer may be formed and then bonded to the base material layer or the cushion layer using a double-sided tape or the like.

  The polyurethane resin foam mainly has substantially spherical open cells, and the open cell ratio is preferably 60% or more, more preferably 70% or more.

  The average cell diameter of the polyurethane resin foam is preferably 20 to 300 μm, more preferably 35 to 200 μm. When deviating from this range, the planarity (flatness) of the polished object after polishing tends to decrease.

  The specific gravity of the polyurethane resin foam is preferably 0.3 to 0.7, more preferably 0.4 to 0.6. When the specific gravity is less than 0.3, the durability of the polishing layer tends to decrease. On the other hand, when the ratio is larger than 0.7, it is necessary to make the material have a low crosslinking density in order to obtain a certain elastic modulus. In that case, the permanent set increases and the durability tends to deteriorate.

  The polyurethane resin foam preferably has a hardness of 10 to 95 degrees, more preferably 40 to 90 degrees, as measured by an Asker C hardness meter. When the Asker C hardness is less than 10 degrees, the durability of the polishing layer tends to decrease, or the surface smoothness of the polished object after polishing tends to deteriorate. On the other hand, if it exceeds 95 degrees, scratches are likely to occur on the surface of the object to be polished.

  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. 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 shape of the polishing pad of the present invention is not particularly limited, and may be a long shape of about several meters in length or a round shape having a diameter of several tens of centimeters.

  The thickness of the polishing layer is not particularly limited, but is usually about 0.2 to 2 mm, and preferably 0.5 to 1.5 mm.

  The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen.

  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, and for example, as shown in FIG. This is performed using a backing material for performing uniform pressurization and a polishing apparatus equipped with a polishing agent 3 supply mechanism. 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.

  Thereby, the surface roughness of the surface of the semiconductor wafer 4 is improved, and scratches are removed. 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. The lens can also be finished and polished by the same method as described above.

  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 razor blade as thin as possible to a thickness of 1 mm or less was used as a sample. The sample was fixed on a glass slide 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. However, in the case of an oval spherical bubble, the area was converted to a circle area, and the equivalent circle diameter was taken as the bubble diameter.

(Measurement of open cell ratio)
The open cell ratio was measured according to the ASTM-2856-94-C method. However, a measurement sample was obtained by stacking 10 polyurethane resin foams punched into a circle. As a measuring instrument, an air comparison type hydrometer 930 type (manufactured by Beckman Co., Ltd.) was used. The open cell ratio was calculated by the following formula.
Open cell ratio (%) = [(V−V1) / V] × 100
V: Apparent volume calculated from sample size (cm ³ )
V1: Sample volume (cm ³ ) measured using an air-comparing hydrometer

(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, which was allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Measurement of hardness)
This was performed according to JIS K-7312. The produced polyurethane resin foam was cut into a size of 5 cm × 5 cm (thickness: arbitrary) as a sample and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. At the time of measurement, the samples were overlapped to have a thickness of 10 mm or more. Using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker C type hardness meter, pressure surface height: 3 mm), the hardness 60 seconds after contacting the pressure surface was measured.

(Measurement of storage modulus)
The storage elastic modulus E ′ (40 ° C.) at 40 ° C. of the produced polyurethane resin foam was measured under the following conditions using a dynamic viscoelasticity measuring device (DMA861e, manufactured by METTLER TOLEDO).
Frequency: 1.6Hz
Temperature increase rate: 2.0 ° C / min
Measurement temperature range: 0-60 ° C
Sample shape: length 19.5mm, width 3.0mm, thickness 1.0mm

(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.

Example 1
Polycaprolactone diol (manufactured by Daicel Chemical Industries, PCL210N, functional group number: 2, hydroxyl value: 110 mgKOH / g) 60 parts by weight in a container, polycaprolactone triol (manufactured by Daicel Chemical Industries, PCL305, functional group number: 3, hydroxyl value: 305 mg KOH / g) 25 parts by weight, propylene oxide adduct of trimethylolpropane (Asahi Glass Co., Ltd., EX-890MP, functional group number: 3, hydroxyl value: 865 mg KOH / g) 2 parts by weight, diethylene glycol (DEG, functional group number: 2, Hydroxyl value: 1058 mg KOH / g) 13 parts by weight, ethylene glycol monophenyl ether (manufactured by Nippon Emulsifier Co., Ltd., 10 parts by weight of hydroxyl group equivalent to 1 equivalent of isocyanate group), silicon-based surfactant (manufactured by Goldschmidt, B8443) 6 The amount unit, and a catalyst were mixed put (manufactured by Kao Corporation, Kao No.25) 0.06 parts by weight. And 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. Thereafter, 95.88 parts by weight of Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.) was added and stirred for about 1 minute to prepare a cell dispersed urethane composition.

  The prepared cell-dispersed urethane composition was applied onto a release-treated release sheet (manufactured by Toyobo, polyethylene terephthalate, thickness: 0.1 mm) to form a cell-dispersed urethane layer. And the base material layer (polyethylene terephthalate, thickness: 0.2 mm) was covered on this cell dispersion | distribution urethane layer. The cell-dispersed urethane layer was made 1.2 mm thick with a nip roll, and then cured at 70 ° C. for 3 hours to form a polyurethane resin foam. Thereafter, the release sheet was peeled from the polyurethane resin foam. Next, the surface of the polyurethane resin foam was sliced using a band saw type slicer (manufactured by Fecken) to adjust the thickness accuracy to 1.0 mm, and the thickness accuracy was adjusted. Thereafter, a double-sided tape (double tack tape, manufactured by Sekisui Chemical Co., Ltd.) was bonded to the surface of the base material layer using a laminator to prepare a polishing pad.

Examples 2 to 6 and 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.
PCL210N (manufactured by Daicel Chemical Industries, polycaprolactone diol, number of functional groups: 2, hydroxyl value: 110 mgKOH / g)
PTMG1000 (manufactured by Mitsubishi Chemical Corporation, polytetramethylene ether glycol, number of functional groups: 2, hydroxyl value: 112 mgKOH / g)
PCL305 (manufactured by Daicel Chemical Industries, polycaprolactone triol, number of functional groups: 3, hydroxyl value: 305 mgKOH / g)
-EX-890MP (Asahi Glass Co., Ltd., propylene oxide adduct of trimethylolpropane, functional group number: 3, hydroxyl value: 865 mgKOH / g)
DEG (diethylene glycol, functional group number: 2, hydroxyl value: 1058 mg KOH / g)
・ PhG (Nippon Emulsifier Co., Ethylene glycol monophenyl ether)
・ PhDG (manufactured by Nippon Emulsifier Co., Ltd., diethylene glycol monophenyl ether)
・ PhFG (Nippon Emulsifier, Propylene glycol monophenyl ether)
・ B8443 (manufactured by Goldschmidt, silicon surfactant)
・ Kao No. 25 (made by Kao Corporation, catalyst)
・ Millionate MTL (Nippon Polyurethane, carbodiimide-modified MDI)

  The polishing pad of the present invention is used when polishing surfaces of optical materials such as lenses and reflection mirrors, silicon wafers, and aluminum substrates. In particular, the polishing pad of the present invention is suitably used as a polishing pad for finishing.

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 a polishing pad having a polishing layer made of a polyurethane resin foam having open cells, the polyurethane resin foam has (A) an isocyanate component, (B) a polyol component, and (C) one hydroxyl group as raw material components. A polishing pad comprising an aromatic compound and / or an aromatic compound having one amino group. 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.

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