JP5506008B2 - Polishing pad - Google Patents

Description

  The present invention stabilizes flattening processing of optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing processing, In addition, the present invention relates to a polishing pad that can be performed with high polishing efficiency. The polishing pad of the present invention is particularly suitable for a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before further laminating and forming these oxide layers and metal layers. Used for.

  A typical material that requires high surface flatness is a single crystal silicon disk called a silicon wafer for manufacturing a semiconductor integrated circuit (IC, LSI). Silicon wafers have a highly accurate surface in each process of stacking and forming oxide layers and metal layers in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC, LSI, and other manufacturing processes. It is required to finish flat. In such a polishing finishing process, a polishing pad is generally fixed to a rotatable support disk called a platen, and a workpiece such as a semiconductor wafer is fixed to a polishing head. A polishing operation is performed by generating a relative speed between the platen and the polishing head by both movements, and continuously supplying a polishing slurry containing abrasive grains onto the polishing pad.

  The polishing characteristics of the polishing pad are required to be excellent in the flatness (planarity) and in-plane uniformity of the 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.

  Considering the development of next-generation devices, a polishing pad with high hardness that can further improve the flatness is required. In order to improve the flatness, it is possible to use a non-foamed hard polishing pad. However, when such a hard pad is used, there arises a problem that the surface to be polished of the polishing object is scratched. In addition, the non-foaming type polishing pad is not desirable from the viewpoint of the polishing rate because it cannot sufficiently hold the abrasive grains in the slurry on the pad surface during the polishing operation.

  A polishing pad in which a water-soluble substance is dispersed in a water-insoluble thermoplastic polymer has been proposed (Patent Document 1). This polishing pad is a non-foamed material, but the water-soluble substance dispersed in the polishing pad dissolves during polishing to form foam-like holes on the surface of the polishing pad, and the polishing pad swells to polish the polishing pad. Since the surface hardness decreases, it is effective in reducing scratches and improving the polishing rate. However, since the pad surface swells and the hardness decreases, the polishing pad is insufficient in terms of planarization characteristics.

  In addition, for the purpose of achieving both planarity improvement and scratch reduction, an isocyanate-terminated prepolymer and a chain extender obtained by reacting an organic polyisocyanate, a high-molecular weight polyol containing a water-soluble high-molecular polyol, and a low-molecular weight polyol; A polishing pad made of the above polymer is disclosed (Patent Document 2). However, since the pad surface also swells and the hardness decreases, the polishing pad cannot sufficiently satisfy the planarization characteristics required in the future.

  In addition, aromatic diisocyanate and alicyclic diisocyanate as the isocyanate component, and number average molecular weight of 500 to 500 as the polyol component for the purpose of suppressing a decrease in flattening characteristics even when a temperature increase due to frictional heat generated in the polishing process occurs. A polishing pad using a polyurethane resin foam obtained by reacting an isocyanate-terminated prepolymer containing 5000 polyether polyol and a low molecular weight polyhydric alcohol with a chain extender is disclosed (Patent Document) 3). And it is described that low molecular weight polyhydric alcohols such as diethylene glycol and triethanolamine, and low molecular weight polyhydric amines such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine may be used in combination. However, the polishing pad also does not sufficiently satisfy the planarization characteristics required in the future.

JP 2001-47355 A Japanese Patent No. 3571334 Japanese Patent No. 3494640

  An object of the present invention is to provide a polishing pad having improved planarization characteristics without reducing the polishing rate. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the polishing pad shown below, and have completed the present invention.

That is, the present invention provides a polishing pad having a polishing layer comprising a polyurethane resin foam, wherein the polyurethane resin foam comprises an isocyanate-terminated prepolymer comprising an isocyanate component and a high molecular weight polyol component, a chain extender, The reaction-cured product further contains at least one amino group-containing active hydrogen compound selected from the group consisting of the following general formulas (1) to (3) as a raw material component. And a polishing pad.
HOCH ₂ CH ₂ NR ¹ R ² (1)
In [general formula (1), ^{R 1} is H or CH _3, ^{R 2} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

HOCH ₂ CH ₂ CH ₂ NR ³ R ⁴ (2)
In [general formula (2), ^{R 3} is H or CH _3, ^{R 4} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH 2 CH ₂ O) _n H, (CH ₂ CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

HOCH (CH ₃ ) CH ₂ NR ⁵ R ⁶ (3)
In [general formula (3), ^{R 5} is H or CH _3, ^{R 6} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

  The inventors of the present invention can increase the hardness of the polyurethane resin foam by using the amino group-containing active hydrogen compound as a raw material component, and use the polyurethane resin foam as a polishing layer to obtain a polishing rate. It has been found that the planarization characteristics can be improved without lowering.

  The amino group-containing active hydrogen compound is at least one selected from the group consisting of monoethanolamine, 2- (2-aminoethylamino) ethanol, diethanolamine, N-methyl-diethanolamine, monopropanolamine, and diisopropanolamine. It is preferable that

  Moreover, it is preferable that the said isocyanate terminal prepolymer contains an isocyanate component, a high molecular weight polyol component, and the said amino group containing active hydrogen compound. By producing an isocyanate-terminated prepolymer using an amino group-containing active hydrogen compound, the physical properties and polishing properties of the polyurethane resin foam are improved.

  In the present invention, the isocyanate component is preferably an aliphatic isocyanate and / or an alicyclic isocyanate, and the alicyclic isocyanate is particularly preferably isophorone diisocyanate. The high molecular weight polyol component is preferably polytetramethylene ether glycol having a number average molecular weight of 500 to 1,500.

  By using a prepolymer comprising the above components, the reaction rate with the chain extender and the like can be controlled within a suitable range, so that not only is preferable in terms of work, but also preferable in terms of moldability of the polyurethane resin foam. Further, the polishing pad using the specific material is particularly excellent in the effect of improving the planarization characteristics.

  In the present invention, the molar ratio (the former / the latter) of the high molecular weight polyol component and the amino group-containing active hydrogen compound is preferably 0.4 to 9. When the molar ratio is less than 0.4, the reaction rate between the isocyanate-terminated prepolymer and the chain extender becomes too fast (because the pot life becomes too short), not only the workability is deteriorated but also the polyurethane resin. The moldability of the foam also tends to deteriorate. On the other hand, when the molar ratio exceeds 9, since it becomes difficult to increase the elastic modulus of the polyurethane resin foam, the planarization characteristics of the polishing pad tend not to be sufficiently improved.

  The isocyanate-terminated prepolymer may further contain a low molecular weight polyol component as a raw material component. The low molecular weight polyol component is preferably diethylene glycol.

  In the present invention, the chain extender is preferably an aromatic polyamine, more preferably a non-halogen aromatic polyamine. In particular, 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, 4,4'-diamino-3,3'-diethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 4,4 '-Diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3', 5,5'-tetraethyldiphenylmethane, 4,4'-diamino-3,3 ' , 5,5'-tetraisopropyldiphenylmethane, and at least one non-halogen selected from the group consisting of trimethylene glycol-di-p-aminobenzoate It is preferred to use aromatic polyamines. By using an aromatic polyamine as the chain extender, the polishing layer can have a high elastic modulus, so that the flatness and in-plane uniformity of the object to be polished are improved. Moreover, the aromatic polyamine which does not contain chlorine is particularly preferable from the viewpoint of planarization characteristics and environmental aspects at the time of disposal.

  Moreover, it is preferable that the specific gravity of a polyurethane resin foam is 0.5-1.0, More preferably, it is 0.7-0.9. When the specific gravity is less than 0.5, the hardness of the entire polishing layer is lowered and the planarization characteristics are deteriorated, 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 subsequent polishing layer tends to be removed immediately at the time of wafer polishing and the polishing rate tends to decrease. On the other hand, when the specific gravity exceeds 1.0, the dressing waste when dressing becomes large, the dressing waste is clogged into the grooves and fine holes, and clogging occurs, and the polishing rate tends to decrease.

  The polyurethane resin foam preferably has an Asker D hardness of 45 to 70 degrees, more preferably 50 to 60 degrees. When Asker D hardness is less than 45 degrees, the flatness of the object to be polished tends to decrease. On the other hand, when it is larger than 70 degrees, the flatness is good, but the in-plane uniformity of the object to be polished tends to decrease. In addition, scratches are likely to occur on the surface of the object to be polished.

  In the present invention, the polyurethane resin foam preferably contains a silicon-based nonionic surfactant in an amount of 0.05% by weight to less than 10% by weight, more preferably 0.5 to 4.5% by weight. is there. When the amount of the silicon-based nonionic surfactant is less than 0.05% by weight, a fine-bubble foam tends to be not obtained. On the other hand, when the content is 10% by weight or more, the number of bubbles in the foam is too large, and it is difficult to obtain a polyurethane resin foam having high hardness.

  Furthermore, the present invention relates to a semiconductor device manufacturing method including a step of polishing a surface of a semiconductor wafer using the polishing pad.

  The polishing pad of the present invention may be only a polishing layer made of a polyurethane resin foam, or may be a laminate of a polishing layer and another layer (such as a cushion layer).

  The isocyanate-terminated prepolymer used in the present invention contains at least an isocyanate component and a high molecular weight polyol component as raw material components. By using an isocyanate-terminated prepolymer, the physical properties of the resulting polyurethane resin foam are excellent.

  As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. As the isocyanate component, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, etc. Aliphatic diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate Isocyanate, alicyclic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more. The diisocyanate may be modified by urethane modification, allophanate modification, biuret modification, isocyanurate modification or the like.

  As the isocyanate component, in addition to the above diisocyanate, a polyfunctional polyisocyanate having three or more functions can be used. As the polyfunctional isocyanate, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo).

  Among the above isocyanate components, it is preferable to use aliphatic isocyanate and / or alicyclic isocyanate. When using together, it is preferable to use 50 weight% or more of alicyclic isocyanate. In particular, it is preferable to use isophorone diisocyanate alone.

  Examples of the high molecular weight polyol component 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 Etc. These may be used alone or in combination of two or more. Among these, it is particularly preferable to use polytetramethylene ether glycol.

  The number average molecular weight of these high molecular weight polyol components is not particularly limited, but is preferably 500 to 1500 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, the polyurethane resin obtained by using the polyurethane resin does not have sufficient elastic properties and tends to be a brittle polymer, the polishing pad made of this polyurethane resin becomes too hard, and the surface of the object to be polished is May cause scratches. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the life of the polishing pad. On the other hand, when the number average molecular weight exceeds 1500, a polishing pad made of a polyurethane resin obtained by using this becomes soft and it is difficult to obtain a sufficiently satisfactory planarity, which is not preferable.

When synthesizing an isocyanate-terminated prepolymer, it is preferable to use at least one amino group-containing active hydrogen compound selected from the group consisting of the following general formulas (1) to (3) as a raw material component.
HOCH ₂ CH ₂ NR ¹ R ² (1)
In [general formula (1), ^{R 1} is H or CH _3, ^{R 2} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

HOCH ₂ CH ₂ CH ₂ NR ³ R ⁴ (2)
In [general formula (2), ^{R 3} is H or CH _3, ^{R 4} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH 2 CH ₂ O) _n H, (CH ₂ CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

HOCH (CH ₃ ) CH ₂ NR ⁵ R ⁶ (3)
In [general formula (3), ^{R 5} is H or CH _3, ^{R 6} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

  In particular, at least one amino group-containing active hydrogen compound selected from the group consisting of monoethanolamine, 2- (2-aminoethylamino) ethanol, diethanolamine, N-methyl-diethanolamine, monopropanolamine, and diisopropanolamine Is preferably used.

  When an isocyanate-terminated prepolymer is synthesized using an amino group-containing active hydrogen compound, the molar ratio (the former / the latter) of the high molecular weight polyol component and the amino group-containing active hydrogen compound is preferably 0.4 to 9. More preferably, it is 0.6-3.

  In addition to the above raw materials, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3 -Methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane Low molecular weight polyol components such as methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, and triethanolamine . These low molecular weight polyol components may be used alone or in combination of two or more. Among these, it is particularly preferable to use diethylene glycol.

  When the amino group-containing active hydrogen compound and the low molecular weight polyol component are used in combination, the molar ratio (the former / the latter) of [high molecular weight polyol component] and [amino group-containing active hydrogen compound + low molecular weight polyol component] is 0. It is preferable that it is 4-9, More preferably, it is 0.6-3. Further, the molar ratio (the former / the latter) of the amino group-containing active hydrogen compound and the low molecular weight polyol component is preferably 0.1 or more, more preferably 0.15 or more. When the molar ratio is less than 0.1, it is difficult to increase the elastic modulus of the polyurethane resin foam, and thus the planarization characteristics of the polishing pad tend not to be sufficiently improved.

The isocyanate-terminated prepolymer uses the polyol component, amino group-containing active hydrogen compound, low molecular weight polyol component and isocyanate component, and has an equivalent ratio (NCO / H ^* ) of isocyanate group (NCO) to active hydrogen (H ^* ). It is produced by heating reaction in the range of 1.2 to 5.0, preferably 1.6 to 2.6. If the ratio is less than 1.2, the prepolymer tends to be solidified or gelled with a high molecular weight during synthesis. On the other hand, if it exceeds 5.0, a large amount of unreacted isocyanate remains, so that the reaction with the chain extender becomes faster, and the molding processability of the polyurethane resin foam and the flattening characteristics of the polishing pad tend to deteriorate. is there.

  As the isocyanate-terminated prepolymer, those having a molecular weight of about 800 to 5000 are preferable because of excellent processability and physical characteristics.

  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, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl Diphenylmethane, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′-diethyldiphenylmethane, 4,4′- Amino-3,3′-diethyl-5,5′-dimethyldiphenylmethane, 4,4′-diamino-3,3′-diisopropyl-5,5′-dimethyldiphenylmethane, 4,4′-diamino-3,3 ′ , 5,5′-tetraethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraisopropyldiphenylmethane, m-xylylenediamine, N, N′-di-sec-butyl-p-phenylene Examples include polyamines exemplified by diamine, m-phenylenediamine, and p-xylylenediamine, and the low molecular weight polyol component described above. These may be used alone or in combination of two or more. In particular, 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, 4,4'-diamino-3,3'-diethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 4,4 '-Diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3', 5,5'-tetraethyldiphenylmethane, 4,4'-diamino-3,3 ' , 5,5'-tetraisopropyldiphenylmethane, and at least one non-halogen selected from the group consisting of trimethylene glycol-di-p-aminobenzoate It is preferable to use an aromatic diamine.

  When synthesizing the isocyanate-terminated prepolymer, when the amino group-containing active hydrogen compound is not used as a raw material component, a reaction cured product is prepared using the amino group-containing active hydrogen compound together with a chain extender. In that case, the molar ratio of the chain extender to the amino group-containing active hydrogen compound (the former / the latter) is preferably 5000 or less, more preferably 0.1 to 3000, and particularly preferably 1 to 2000. is there. Even when the amino group-containing active hydrogen compound is used as a raw material component when synthesizing an isocyanate-terminated prepolymer, a reaction cured product is obtained using the amino group-containing active hydrogen compound together with a chain extender. It may be produced.

  The ratio between the isocyanate-terminated prepolymer and the chain extender can be variously changed depending on the molecular weight of each and the desired physical properties of the polishing pad produced therefrom. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the prepolymer relative to the number of functional groups of the chain extender is preferably in the range of 0.95 to 1.20, more preferably 0.99 to 1.15. It is. The same applies when a chain extender and an amino group-containing active hydrogen compound are used in combination.

  The polyurethane resin foam can be produced by applying a known urethanization technique such as a melting method or a solution method, but is preferably produced by a melting method in consideration of cost, work environment, and the like.

  The polyurethane resin foam is produced by mixing and curing a first component containing an isocyanate-terminated prepolymer and a second component containing a chain extender (and an amino group-containing active hydrogen compound).

  Examples of the method for producing a polyurethane resin foam include a method of adding hollow beads, a mechanical foaming method, and a chemical foaming method.

  In particular, a mechanical foaming method using a silicone surfactant which is a copolymer of polyalkylsiloxane and polyether and does not have an active hydrogen group is preferable. Examples of suitable silicon-based nonionic surfactants include SH-193 (manufactured by Toray Dow Corning Silicone) and L-5340 (manufactured by Nippon Unica).

  If necessary, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added to the polyurethane resin foam.

An example of a method for producing a fine cell type polyurethane resin foam constituting the polishing pad (polishing layer) will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
1) Foaming process for producing a cell dispersion of isocyanate-terminated prepolymer A silicon-based surfactant is added to the isocyanate-terminated prepolymer (first component), and the mixture is stirred in the presence of a non-reactive gas to remove the non-reactive gas. Disperse as fine bubbles to obtain a cell dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing Agent (Chain Extender) Mixing Step A chain extender (second component) is added to the above cell dispersion, mixed and stirred to obtain a foaming reaction solution.
3) Casting process The above foaming reaction liquid is poured into a mold.
4) Curing process The foaming reaction liquid poured into the mold is heated and reacted and cured.

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

  A known stirring device can be used without particular limitation as a stirring device for dispersing non-reactive gas in the form of fine bubbles and dispersed in the first component containing the silicon-based surfactant. Specifically, a homogenizer, a dissolver, 2 A shaft planetary mixer (planetary mixer) is exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained.

  In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a cell dispersion in a foaming process, and the stirring which adds and mixes the chain extender in a mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the foaming step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

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

  In the polyurethane resin foam, a known catalyst that promotes a polyurethane reaction such as tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  Polyurethane resin foam can be manufactured by batch feeding each component into a container and stirring, or by continuously supplying each component and non-reactive gas to the stirring device and stirring, It may be a continuous production method in which a dispersion is sent out to produce a molded product.

  In addition, a prepolymer as a raw material of the polyurethane resin foam is put into a reaction vessel, and then a chain extender or the like is added, stirred, and then poured into a casting mold of a predetermined size, and the block is shaped like a bowl, or A thin sheet may be formed in the method of slicing using a band saw slicer or the above-described casting step. Alternatively, the raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.

  In this invention, it is preferable that the average cell diameter of the said polyurethane resin foam is 70 micrometers or less, More preferably, it is 30-60 micrometers. When deviating from this range, the planarity (flatness) of the polished object after polishing tends to decrease.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the object to be polished preferably has a surface shape that holds and renews the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and renewing the slurry. However, in order to more efficiently retain the slurry and renew the slurry, it is also a subject of polishing. In order to prevent destruction of the object to be polished due to adsorption with the object, it is preferable that the polishing surface has an uneven structure. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

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

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

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

  The polishing pad of the present invention may be a laminate of the polishing layer and a cushion sheet.

  The cushion sheet (cushion layer) supplements the characteristics of the polishing layer. The cushion sheet is necessary for achieving both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a polishing object having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire polishing object. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the cushion sheet. In the polishing pad of the present invention, it is preferable to use a cushion sheet that is softer than the polishing layer.

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

  Examples of means for attaching the polishing layer and the cushion sheet include a method of pressing the polishing layer and the cushion sheet with a double-sided tape.

  The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. In consideration of preventing the penetration of the slurry into the cushion sheet, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. In addition, since the composition of the polishing layer and the cushion sheet may be different, the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force of each layer can be optimized.

  The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen. As the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of peeling from the platen after use of the polishing pad, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low.

  The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 1, a polishing surface plate 2 that supports a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. The polishing pad 1 is attached to the polishing surface plate 2 by attaching it with a double-sided tape, for example. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the semiconductor wafer 4 supported on each of the polishing surface plate 2 and the support table 5 face each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the semiconductor wafer 4 against the polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the polishing pad 1 while rotating the polishing surface plate 2 and the support base 5, and polishing is performed while supplying slurry. The flow rate of the slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited and are appropriately adjusted.

  As a result, the protruding portion of the surface of the semiconductor wafer 4 is removed and polished flat. Thereafter, a semiconductor device is manufactured by dicing, bonding, packaging, or the like. The semiconductor device is used for an arithmetic processing device, a memory, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Measurement and evaluation methods]
(Measurement of number average molecular weight of polyol component)
The number average molecular weight of the polyol component was measured by GPC (gel permeation chromatography) and converted by standard polystyrene.
GPC device: manufactured by Shimadzu Corporation, LC-10A
Column: Polymer Laboratories, (PLgel, 5 μm, 500 mm), (PLgel, 5 μm, 100 mm), and (PLgel, 5 μm, 50 mm) connected to three columns, flow rate: 1.0 ml / min
Concentration: 1.0 g / l
Injection volume: 40 μl
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (Measurement of average bubble diameter)
A sample for measurement was prepared by cutting the produced polyurethane resin foam in parallel with a microtome cutter as thin as possible to a thickness of 1 mm or less. The sample surface was photographed at 100 times with a scanning electron microscope (S-3500N, manufactured by Hitachi Science Systems). Then, using an image analysis software (WIN-ROOF, manufactured by MITANI Corporation), the equivalent circle diameter of all bubbles in an arbitrary range was measured, and the average bubble diameter was calculated from the measured value.

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

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

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As polishing conditions, silica slurry (SS12, manufactured by Cabot Corporation) was added as a slurry at a flow rate of 150 ml / min. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.

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

  Two steps were measured as the flattening characteristics. One is a local step, which is a step in a pattern in which lines having a width of 270 μm are arranged in a space of 30 μm, and the step after one minute was measured. The other is the amount of scraping. In the pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and the pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the level difference between the above two patterns is 2000 mm or less. The amount of scraping of the 270 μm space was measured. When the numerical value of the local step is low, it indicates that the flattening speed in a certain time is high with respect to the unevenness of the oxide film caused by the pattern dependence on the wafer. Further, when the amount of scraping of the space is small, the amount of shaving of a portion that is not desired to be shaved is small and flatness is high.

Example 1
In a container, 1551 parts by weight of isophorone diisocyanate (hereinafter abbreviated as IPDI), 1849 parts by weight of polytetramethylene ether glycol (hereinafter abbreviated as PTMG) having a number average molecular weight of 1018, and N-methyl-diethanolamine (hereinafter abbreviated as NMDEA). 200 parts by weight were added and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer (A). PTMG / NMDEA (molar ratio) is 1.08.
100 parts by weight of the prepolymer (A) and 3 parts by weight of a silicon surfactant (manufactured by Toray Dow Corning Silicone, SH-193) are added to the polymerization vessel and mixed, adjusted to 80 ° C. and depressurized under reduced pressure. Foamed. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. 25 parts by weight of 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane (hereinafter abbreviated as MED) previously melted at 90 ° C. was added thereto. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block. The polyurethane resin foam block was sliced using a band saw type slicer to obtain a polyurethane resin foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and is polished by using a groove processing machine to process concentric grooves with a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm. A sheet was obtained. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was applied to the surface of the polishing sheet opposite to the grooved surface using a laminator. Further, the surface of the corona-treated cushion sheet (manufactured by Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
A container is charged with IPDI (1566 parts by weight), PTMG (1867 parts by weight), monoethanolamine (hereinafter abbreviated as MEA) 17 parts by weight, and diethylene glycol (hereinafter abbreviated as DEG) 150 parts by weight. It was made to react for 3 hours and the isocyanate terminal prepolymer (B) was obtained. PTMG / (MEA + DEG) (molar ratio) is 1.08. The MEA / DEG (molar ratio) is 0.2.
A polishing pad was prepared in the same manner as in Example 1 except that 100 parts by weight of the isocyanate-terminated prepolymer (B) was used instead of 100 parts by weight of the isocyanate-terminated prepolymer (A).

Example 3
IPDI (1573 parts by weight), PTMG (1875 parts by weight), MEA (39 parts by weight), and DEG (113 parts by weight) are placed in a container and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer (C). It was. PTMG / (MEA + DEG) (molar ratio) is 1.08. The MEA / DEG (molar ratio) is 0.6.
In Example 1, a polishing pad was prepared in the same manner as in Example 1 except that 100 parts by weight of the isocyanate-terminated prepolymer (C) was used instead of 100 parts by weight of the isocyanate-terminated prepolymer (A).

Example 4
In a container, IPDI (1243 parts by weight), urethane-modified trimerized hexamethylene diisocyanate (Coronate HX, manufactured by Nippon Polyurethane) 457 parts by weight, PTMG (1744 parts by weight), MEA (16 parts by weight), and DEG (140 parts by weight) And reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer (D). PTMG / (MEA + DEG) (molar ratio) is 1.08. The MEA / DEG (molar ratio) is 0.2 .
In Example 1, a polishing pad was prepared in the same manner as in Example 1 except that 100 parts by weight of the isocyanate-terminated prepolymer (D) was used instead of 100 parts by weight of the isocyanate-terminated prepolymer (A).

Example 5
In a container, IPDI (1561 parts by weight), PTMG (1861 parts by weight), diethanolamine (hereinafter abbreviated as DEA) 30 parts by weight, and DEG (149 parts by weight) are allowed to react at 100 ° C. for 3 hours. Polymer (E) was obtained. PTMG / (DEA + DEG) (molar ratio) is 1.08. DEA / DEG (molar ratio) is 0.2.
In Example 1, instead of 100 parts by weight of the isocyanate-terminated prepolymer (A), 100 parts by weight of the isocyanate-terminated prepolymer (E) was used, and the MED was changed from 25 parts by weight to 24 parts by weight. A polishing pad was produced in the same manner.

Example 6
In a container, IPDI (1561 parts by weight), PTMG (1861 parts by weight), 2- (2-aminoethylamino) ethanol (hereinafter abbreviated as AEAE) 29 parts by weight, and DEG (149 parts by weight) are placed, and 100 ° C. For 3 hours to obtain an isocyanate-terminated prepolymer (F). PTMG / (AEAE + DEG) (molar ratio) is 1.08. AEAE / DEG (molar ratio) is 0.2.
In Example 1, instead of 100 parts by weight of the isocyanate-terminated prepolymer (A), 100 parts by weight of the isocyanate-terminated prepolymer (F) was used, and the MED was changed from 25 parts by weight to 24 parts by weight. A polishing pad was produced in the same manner.

Comparative Example 1
IPDI (1561 parts by weight), PTMG (1861 parts by weight), and DEG (179 parts by weight) were placed in a container and reacted at 100 ° C. for 3 hours to obtain an isocyanate-terminated prepolymer (G). PTMG / (DEG) (molar ratio) is 1.08.
A polishing pad was produced in the same manner as in Example 1 except that 100 parts by weight of the isocyanate-terminated prepolymer (G) was used instead of 100 parts by weight of the isocyanate-terminated prepolymer (A).

Comparative Example 2
In a container, 1229 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, PTMG (1901 parts by weight), and DEG (198 Part by weight) and reacted at 70 ° C. for 6 hours to obtain an isocyanate-terminated prepolymer (H). PTMG / (DEG) (molar ratio) is 1.
In Example 1, instead of 100 parts by weight of the isocyanate-terminated prepolymer (A), 100 parts by weight of the isocyanate-terminated prepolymer (H) was used, and instead of MED (25 parts by weight) previously melted at 90 ° C., 120 parts by weight was used. A polishing pad was produced in the same manner as in Example 1 except that 4,4′-methylenebis (o-chloroaniline) (hereinafter abbreviated as MOCA) (30 parts by weight) melted at 0 ° C. was used.

Comparative Example 3
IPDI (1653 parts by weight), PTMG (1744 parts by weight), triethanolamine (hereinafter abbreviated as TEA) 100 parts by weight and DEG (103 parts by weight) are placed in a container and reacted at 100 ° C. for 3 hours to produce isocyanate. Terminal prepolymer (I) was obtained. PTMG / (TEA + DEG) (molar ratio) is 1.05. TEA / DEG (molar ratio) is 0.69.
In Example 1, instead of 100 parts by weight of the isocyanate-terminated prepolymer (A), 100 parts by weight of the isocyanate-terminated prepolymer (I) was used, and the MED was changed from 25 parts by weight to 27 parts by weight. A polishing pad was produced in the same manner.

A polishing test was performed using the polishing pads obtained in the examples and comparative examples, and the polishing characteristics were evaluated. The results are shown in Table 1.

  From the results shown in Table 1, the polishing pad of the present invention is superior in flattening characteristics because of its higher hardness than conventional polishing pads, and is also excellent in terms of environment because it is halogen-free.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing

Explanation of symbols

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 (13)

In a polishing pad having a polishing layer made of a polyurethane resin foam, the polyurethane resin foam comprises an isocyanate component and a high molecular weight polyol component having a number average molecular weight of 500 to 1500 (excluding the following amino group-containing active hydrogen compound) . A reaction cured product of a polyurethane raw material composition containing an isocyanate-terminated prepolymer obtained by reacting the prepolymer raw material composition and a chain extender (except the following amino group-containing active hydrogen compound) (however, The prepolymer raw material composition and / or the polyurethane raw material composition is at least one selected from the group consisting of the following general formulas (1) to (3): A polishing pad comprising an amino group-containing active hydrogen compound.
HOCH ₂ CH ₂ NR ¹ R ² (1)
In [general formula (1), ^{R 1} is H or CH _3, ^{R 2} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

HOCH ₂ CH ₂ CH ₂ NR ³ R ⁴ (2)
In [general formula (2), ^{R 3} is H or CH _3, ^{R 4} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH 2 CH ₂ O) _n H, (CH ₂ CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]

HOCH (CH ₃ ) CH ₂ NR ⁵ R ⁶ (3)
In [general formula (3), ^{R 5} is H or CH _3, ^{R 6} is _{H, CH 3, (CH 2} ) n CH 3, (CH 2 CH 2 O) n H, (CH 2 CH (CH ₃ ) O) _n H, (CH ₂ ) _n NH ₂ , (CH ₂ ) _n OH, or (CH ₂ ) _n SH. However, n = 1-9. ]
The amino group-containing active hydrogen compound is at least one selected from the group consisting of monoethanolamine, 2- (2-aminoethylamino) ethanol, diethanolamine, N-methyl-diethanolamine, monopropanolamine, and diisopropanolamine. The polishing pad according to claim 1. The polishing pad according to claim 1 or 2 , wherein the isocyanate component is an aliphatic isocyanate and / or an alicyclic isocyanate. The polishing pad according to claim 3 , wherein the alicyclic isocyanate is isophorone diisocyanate. High molecular weight polyol component, the polishing pad according to any one of claims 1 to 4, which is a port polytetramethylene ether glycol. The polishing pad according to any one of claims 1 to 5 , wherein a molar ratio (the former / the latter) of the high molecular weight polyol component and the amino group-containing active hydrogen compound is 0.4 to 9 . Prepolymer raw material composition, as raw material component further, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1 , 4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6-hexane Group consisting of triol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, and triethanolamine The polishing pad according to any one of claims 1 to 6 and containing not at least one low molecular weight polyol component selected. The polishing pad according to claim 7 , wherein the low molecular weight polyol component is diethylene glycol. The polishing pad according to any one of claims 1 to 8 , wherein the chain extender is an aromatic polyamine. The polishing pad according to claim 9 , wherein the aromatic polyamine is a non-halogen aromatic polyamine. Non-halogen aromatic polyamines are 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, 4,4'-diamino-3,3'-diethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'- Dimethyldiphenylmethane, 4,4′-diamino-3,3′-diisopropyl-5,5′-dimethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4,4′- At least one selected from the group consisting of diamino-3,3 ′, 5,5′-tetraisopropyldiphenylmethane and trimethylene glycol-di-p-aminobenzoate The polishing pad of claim 10, wherein. The polishing pad according to any one of claims 1 to 11 , wherein the polyurethane resin foam contains 0.05 wt% or more and less than 10 wt% of a silicon-based nonionic surfactant. The method of manufacturing a semiconductor device including a step of polishing a surface of a semiconductor wafer using a polishing pad according to any one of claims 1 to 12.

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