JP5871978B2 - Polishing pad and manufacturing method thereof - 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.

  As the polishing characteristics of the polishing pad, it is required that the polishing object has excellent flatness (planarity) and in-plane uniformity and has 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 making the polishing layer a foam to increase the holding amount of the slurry, or making the polishing layer hydrophilic to increase the holding ability of the slurry.

  For example, in Patent Document 1, in order to improve water wettability of a polishing pad, (A) a crosslinked elastomer and (B) a carboxyl group, an amino group, a hydroxyl group, an epoxy group, a sulfonic acid group, and a phosphoric acid group. Characterized in that it contains a substance having at least one functional group selected from the group and a water-soluble substance, and (A) the crosslinked elastomer is a polymer obtained by crosslinking 1,2-polybutadiene. A polishing pad composition has been proposed.

  Further, Patent Document 2 is a polishing pad made of a polyurethane composition containing a urethane resin in which a compound having a hydrophilic group is copolymerized and containing a hydrophilic agent in order to make the slurry easily compatible with the polishing pad. The hydrophilic agent is 2,4,7,9-tetramethyl-5-decyne-4,7-diol-dipolyoxyethylene ether and 2,4,7,9-tetramethyl-5-decyne- There has been proposed a polishing pad that is at least one selected from the group consisting of 4,7-diol, and wherein the compound having a hydrophilic group is an ethylene oxide monomer.

In Patent Document 3, in order to obtain a polishing pad having good flatness, in-plane uniformity, polishing rate, little change in polishing rate, and excellent life characteristics, it is one of the raw material components of polyurethane resin foam. As a starting material, a hydrophilic isocyanate-terminated prepolymer comprising a hydrophilic high molecular weight polyol component having an ethylene oxide unit (—CH ₂ CH ₂ O—) of 25% by weight or more and a number average molecular weight of 500 or more and an isocyanate component as raw material components. It has been proposed to use polymer (B).

  Further, in Patent Document 4, in order to improve the hydrophilicity of the polishing layer, a resin constituting the polishing layer can be dissolved in an organic solvent that can be dissolved, and a partially acylated polysaccharide component hardly soluble or insoluble in water is used. A contained polishing layer has been proposed.

  However, when the polishing layer is made hydrophilic, the polishing rate increases, but there is a problem that the flatness of the object to be polished is deteriorated.

Japanese Patent No. 3826702 Japanese Patent No. 3851135 Japanese Patent No. 4189963 Japanese Patent No. 5189440

  An object of the present invention is to provide a polishing pad having a high polishing rate and excellent planarization characteristics, and a method for producing the same.

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

In the polishing pad having a polishing layer made of a polyurethane resin foam, the polyurethane resin as a material for forming the polyurethane resin foam is represented by the following general formula (1): a urethane group or a urea group of an isocyanate-terminated prepolymer; The present invention relates to a polishing pad wherein an alkoxysilyl group is introduced into a side chain by a reaction with an isocyanate group of an alkoxysilyl group-containing isocyanate.


(In the formula, X is OR ¹ or OH, R ¹ is each independently an alkyl group having 1 to 4 carbon atoms, and R ² is an alkylene group having 1 to 6 carbon atoms.)

  As described above, the present invention is characterized in that an alkoxysilyl group is introduced into the side chain of the polyurethane resin. The alkoxysilyl group present on the surface of the polishing layer is hydrolyzed by water in the slurry during polishing, and a silanol group is generated on the surface of the polishing layer. Since this silanol group is hydrophilic, the hydrophilicity of the polishing layer surface is improved. As a result, the holding ability of the slurry can be increased, and the polishing rate can be increased.

  On the other hand, since the alkoxysilyl group is introduced into the side chain of the polyurethane resin, the polyurethane resin hardly swells with the slurry. Further, the alkoxysilyl group present in the polishing layer is difficult to be hydrolyzed because it is difficult to contact the water in the slurry. Therefore, only the polishing layer surface can be hydrophilized, and a decrease in hardness of the entire polishing layer can be suppressed. As a result, the planarization characteristics of the polishing pad are unlikely to deteriorate.

  The alkoxysilyl group-containing isocyanate is preferably 3-isocyanatopropyltriethoxysilane.

  Moreover, it is preferable that the addition amount of the said alkoxysilyl group containing isocyanate is 1-10 weight part with respect to 100 weight part of isocyanate terminal prepolymers. Since the alkoxysilyl group is introduced into the side chain of the polyurethane resin, hydrophilicity is exhibited by the introduction of a small amount of the alkoxysilyl group. When the addition amount of the alkoxysilyl group-containing isocyanate is less than 1 part by weight, the surface of the polishing layer is hardly hydrophilized, and when it exceeds 10 parts by weight, it tends to be difficult to produce a polishing layer having excellent polishing characteristics.

The present invention also relates to a method for producing a polishing pad comprising a step of mixing a first component containing an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane resin foam.
In the step, a silicone-based surfactant is added to the first component containing the isocyanate-terminated prepolymer so as to be 0.05 to 10% by weight with respect to the total weight of the first component and the second component. After preparing a bubble dispersion in which one component is stirred with a non-reactive gas to disperse the non-reactive gas as bubbles, a second component containing a chain extender is mixed in the bubble dispersion and cured. A step of producing a polyurethane resin foam,
The said 2nd component is related with the manufacturing method of the polishing pad characterized by containing the alkoxy silyl group containing isocyanate represented by following General formula (1).


(In the formula, X is OR ¹ or OH, R ¹ is each independently an alkyl group having 1 to 4 carbon atoms, and R ² is an alkylene group having 1 to 6 carbon atoms.)

  According to the production method, the polyurethane in which the allophanate structure or the burette structure is formed by the reaction between the urethane group or urea group of the isocyanate-terminated prepolymer and the isocyanate group of the alkoxysilyl group-containing isocyanate, and the alkoxysilyl group is introduced into the side chain. A resin can be obtained.

  The alkoxysilyl group-containing isocyanate is preferably 3-isocyanatopropyltriethoxysilane.

  The addition amount of the alkoxysilyl group-containing isocyanate is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the isocyanate-terminated prepolymer.

  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 a high polishing rate and excellent planarization characteristics. In addition, the polishing pad of the present invention makes the polishing layer surface hydrophilic by the slurry during the polishing operation, so that the aggregation of abrasive grains in the slurry is difficult to occur, and it is effective that scratches are generated on the object to be polished. Can be suppressed.

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

  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 polyurethane resin, which is a material for forming the polyurethane resin foam, is produced by reacting the urethane group or urea group of the isocyanate-terminated prepolymer with the isocyanate group of the alkoxysilyl group-containing isocyanate represented by the following general formula (1). An alkoxysilyl group is introduced.


(In the formula, X is OR ¹ or OH, R ¹ is each independently an alkyl group having 1 to 4 carbon atoms, and R ² is an alkylene group having 1 to 6 carbon atoms.)

  The polyurethane resin is preferably a reaction cured product of a polyurethane raw material composition containing an isocyanate-terminated prepolymer, an alkoxysilyl group-containing isocyanate represented by the general formula (1), and a chain extender.

  The isocyanate-terminated prepolymer is obtained by reacting a prepolymer raw material composition containing an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol) and the like.

  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, cycloaliphatic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.).

  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 Etc. These may be used alone or in combination of two or more.

  Although the weight average molecular weight of high molecular weight polyol is not specifically limited, From viewpoints, such as the elastic characteristic of the polyurethane resin obtained, it is preferable that it is 500-3000. When the weight 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 weight average molecular weight exceeds 3000, a polishing pad made of a polyurethane resin obtained by using this becomes soft and it becomes difficult to obtain a sufficiently satisfactory planarity.

  In addition to the high molecular weight polyols described above, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3 -Butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) ) Benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) Cyclohexanol, diethanolamine, N- methyldiethanolamine, and can be used in combination of low molecular weight polyols such as triethanolamine. Moreover, low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine, can also be used in combination. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more.

Isocyanate-terminated prepolymer, with an isocyanate component and a polyol component, the equivalent ratio of isocyanate groups (NCO) and the active hydrogen ^{(H *) (NCO / H} *) is usually from 1.2 to 8, preferably 1.5 to It is produced by heating reaction in the range of 3.

  The isocyanate-terminated prepolymer has a urethane group in the molecule and may further have a urea group.

In the general formula (1), X is preferably OR ¹ . R ¹ is preferably a methyl group or an ethyl group. As the alkoxysilyl group-containing isocyanate represented by the general formula (1), 3-isocyanatopropyltriethoxysilane is preferably used.

  The alkoxysilyl group-containing isocyanate is preferably added in an amount of 1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the isocyanate-terminated prepolymer.

  A chain extender is used to cure the isocyanate-terminated 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, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl Diphenylmethane, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, m-xyl And polyamines exemplified by N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine, or the above-mentioned low molecular weight polyols and low molecular weight polyamines. be able to. 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.

  The number of isocyanate groups of the prepolymer relative to the number of active hydrogen groups (hydroxyl group, amino group) of the chain extender is an allophanate structure by efficiently reacting the urethane group or urea group of the prepolymer with the isocyanate group of the alkoxysilyl group-containing isocyanate. Or in order to form a bullet structure, it is preferable that it is 0.95-1.00.

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

  In particular, a mechanical foaming method using a silicone surfactant which is a copolymer of polyalkylsiloxane and polyether is preferable. Examples of the silicone surfactant include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8443, B8465 (manufactured by Goldschmidt), and the like. The silicone-based surfactant is preferably added to the polyurethane raw material composition so as to be 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight.

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

  The polyurethane resin foam may be a closed cell type or an open cell type, but it prevents the slurry from entering the polishing layer and prevents hydrolysis of the alkoxysilyl groups present in the polishing layer. In order to do so, it is preferable that it is a closed-cell type.

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 step for producing a cell dispersion of isocyanate-terminated prepolymer A silicone-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 bubbles to obtain a bubble dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Mixing step of alkoxysilyl group-containing isocyanate and chain extender An alkoxysilyl group-containing isocyanate and a chain extender (second component) are 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 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. The use of air that has been dried to remove moisture is most preferred in terms of cost.

  As a stirrer for dispersing the non-reactive gas in the form of bubbles in the first component containing the silicone-based surfactant, a known stirrer can be used without particular limitation. Specifically, a homogenizer, a dissolver, biaxial Examples include a planetary mixer (planetary mixer). 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 alkoxysilyl group containing isocyanate and 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 that is a raw material of the polyurethane resin foam is put into a reaction vessel, and then an alkoxysilyl group-containing isocyanate and a chain extender are added, stirred, and then poured into a casting mold of a predetermined size to produce a block. A thin sheet may be formed by slicing the block using a saddle-like or band saw-like slicer, or in the above-described casting step.

  The average cell diameter of the polyurethane resin foam is preferably 30 to 200 μm. When deviating from this range, the planarity (flatness) of the polished object after polishing tends to decrease.

  The hardness of the polyurethane resin foam is preferably 40 to 70 degrees with an Asker D hardness meter. When the Asker D hardness is less than 40 degrees, the planarity of the object to be polished is lowered. On the other hand, when it exceeds 70 degrees, the planarity is good, but the uniformity (uniformity) of the object to be polished is lowered. There is a tendency.

  The specific gravity of the polyurethane resin foam is preferably 0.5 to 1.3. When the specific gravity is less than 0.5, the surface strength of the polishing layer decreases, and the planarity of the object to be polished tends to decrease. On the other hand, when the ratio is larger than 1.3, the number of bubbles on the surface of the polishing layer is reduced and planarity is good, but the polishing rate 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. Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

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

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

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

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

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

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

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

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

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

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

[Measurement and evaluation methods]
(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.

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

(Measurement of hardness)
This was performed in accordance with JIS K6253-1997. The produced polyurethane resin foam was cut into a size of 2 cm × 2 cm (thickness: arbitrary) and used as a sample for hardness measurement, and was allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. . At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter). Further, the sample was immersed in water for 48 hours, and then the sample was taken out and lightly wiped off the surface moisture, and then the hardness was measured by the same method.

(Evaluation of polishing characteristics)
Using MAT-ARW-8C1A (manufactured by MAT Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the polishing amount obtained by polishing a thermal oxide film of 1 μm formed on an 8-inch silicon wafer for 60 seconds. An optical interference type film thickness measuring device (manufactured by Nanometrics, device name: Nanospec) was used for measuring the thickness of the oxide film. As a polishing condition, silica slurry (SS12 manufactured by Cabot Corporation) was added as a slurry at a flow rate of 120 ml / min during polishing. The polishing load was 4.5 psi, the polishing platen rotating speed was 93 rpm, and the wafer rotating speed was 90 rpm.

  The flattening characteristics were evaluated by the amount of scraping. 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 was deposited by p-TEOS to produce a patterned wafer having an initial step of 0.5 μm. This wafer was polished under the above conditions, and after polishing, each step was measured to calculate the amount of scraping. The amount of scraping is 270 μm when the step of the upper part of the lines of the two types of patterns is 2000 mm or less in a pattern in which 270 μm wide lines are arranged in a 30 μm space and a pattern in which 30 μm wide lines are arranged in a 270 μm space This is the amount of space shaving. When the amount of scraping of the space of 270 μm is small, the amount of shaving of the portion that is not desired to be shaved is small, indicating that the flatness is high.

  Scratch evaluation was performed by polishing three 8-inch dummy wafers under the above conditions, then polishing an 8-inch wafer on which a thermal oxide film having a thickness of 10,000 mm was polished for 1 minute, and a defect evaluation apparatus manufactured by KLA Tencor. (Surfscan SP1) was used to measure how many streaks of 0.19 μm or more exist on the polished wafer.

Example 1
In the reaction vessel, 100 parts by weight of a polyether-based prepolymer (manufactured by Uniroyal, Adiprene L-325) and 3 parts by weight of a silicone-based surfactant (manufactured by Goldschmidt, B8465) are added and mixed at 70 ° C And degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereafter, in a reaction vessel, 1 part by weight of 3-isocyanatopropyltriethoxysilane (hereinafter referred to as 3-IPESi) and 4,4′-methylenebis (o-chloroaniline) (hereinafter referred to as MOCA) previously melted at 120 ° C. 28.9 parts by weight were added (NCO Index: 1.0). The mixed liquid was stirred for about 70 seconds, and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block.
The polyurethane resin foam block heated to about 80 ° C. was sliced using a slicer (manufactured by Amitech, VGW-125) to obtain a polyurethane resin foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing layer. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Furthermore, the surface of the cushion sheet (Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) subjected to corona treatment was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
A polishing pad was produced in the same manner as in Example 1 except that the amount of 3-IPESi added was changed from 1 part by weight to 5 parts by weight.

Example 3
In a reaction vessel, polyethylene glycol (PEG, Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 1000) 40 parts by weight, polyethylene glycol (PEG, Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 600) 12.8 parts by weight, DEG 6 A weight part was added, and dehydration under reduced pressure was performed for 1 to 2 hours with stirring. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (41.2 parts by weight) was added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was terminated when the NCO% became almost constant (NCO%: 9.96). Thereafter, degassing under reduced pressure was performed for about 2 hours to obtain a hydrophilic isocyanate-terminated prepolymer (hereinafter referred to as a hydrophilic prepolymer).
In the reaction vessel, 80 parts by weight of a polyether-based prepolymer (Uniroy, Adiprene L-325), 20 parts by weight of a hydrophilic prepolymer, and 3 parts by weight of a silicone-based surfactant (Goldschmitt, B8465) Were added, mixed, adjusted to 70 ° C. and degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereafter, 1 part by weight of 3-IPESi and 29.4 parts by weight of MOCA previously melted at 120 ° C. were added into the reaction vessel (NCO Index: 1.0). The mixed liquid was stirred for about 70 seconds, 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. Thereafter, a polishing pad was produced in the same manner as in Example 1.

Example 4
A polishing pad was produced in the same manner as in Example 3 except that the amount of 3-IPESi added was changed from 1 part by weight to 5 parts by weight.

Comparative Examples 1-3
A polishing pad was prepared in the same manner as in Example 1 except that the formulation shown in Table 1 was adopted.

  The polishing pads of Examples 1 to 4 had a high polishing rate and excellent planarization characteristics. Moreover, it was possible to effectively suppress the generation of scratches on the wafer. On the other hand, the polishing pads of Comparative Examples 1 to 3 were insufficient in polishing rate and planarization characteristics. Moreover, the polishing pads of Comparative Examples 1 and 2 could not suppress the generation of scratches on the wafer.

  The polishing pad of the present invention provides stable and high leveling of flattening of optical materials such as lenses and reflecting mirrors, silicon wafers, aluminum substrates, and materials requiring high surface flatness such as general metal polishing. Can be done with efficiency. The polishing pad of the present invention is particularly suitable for a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before further laminating and forming these oxide layers and metal layers. Can be used for

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

Claims (6)

In a polishing pad having a polishing layer made of a polyurethane resin foam, the polyurethane resin as a material for forming the polyurethane resin foam includes at least one chemical structure represented by the following general formulas (2) to (4). A polishing pad, wherein an alkoxysilyl group is introduced into the side chain.

(In the formula, X is OR ¹ or OH, R ¹ is each independently an alkyl group having 1 to 4 carbon atoms, and R ² is an alkylene group having 1 to 6 carbon atoms.) In the general formula (2) ~ (4), X is an ethoxy group, ^{R 1} is an ethyl group, a polishing pad of claim 1, wherein ^{R 2} is a propylene group. In the method for producing a polishing pad comprising the steps of mixing a first component containing an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane resin foam,
In the step, a silicone-based surfactant is added to the first component containing the isocyanate-terminated prepolymer so as to be 0.05 to 10% by weight with respect to the total weight of the first component and the second component. After preparing a bubble dispersion in which one component is stirred with a non-reactive gas to disperse the non-reactive gas as bubbles, a second component containing a chain extender is mixed in the bubble dispersion and cured. A step of producing a polyurethane resin foam,
The said 2nd component contains the alkoxysilyl group containing isocyanate represented by following General formula (1), The manufacturing method of the polishing pad characterized by the above-mentioned.


(In the formula, X is OR ¹ or OH, R ¹ is each independently an alkyl group having 1 to 4 carbon atoms, and R ² is an alkylene group having 1 to 6 carbon atoms.) The alkoxysilyl group-containing isocyanate, 3-isocyanate propyl method for producing a polishing pad of a is claim 3, wherein triethoxysilane. The method for producing a polishing pad according to claim 3 or 4, wherein the addition amount of the alkoxysilyl group-containing isocyanate is 1 to 10 parts by weight with respect to 100 parts by weight of the isocyanate-terminated prepolymer. The method of manufacturing a semiconductor device including a step of polishing a surface of a semiconductor wafer using a polishing pad according to claim 1 or 2, wherein.