JP5875300B2 - 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 suitably used in a step of flattening a semiconductor device having a Cu film (including a Cu alloy film) formed on a wafer to form a Cu wiring pattern.

  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 using a foam containing bubbles and increasing the amount of slurry retained.

  Examples of a method for increasing the amount of slurry retained include a method for making the polishing pad itself hydrophilic. Specifically, (1) a method for introducing a hydrophilic group such as a hydroxyl group into a matrix material, (2 ) A method of mixing a matrix material and a hydrophilic substance is mentioned. For example, a polishing pad composition containing (A) a crosslinked elastomer and (B) a substance having a functional group such as a hydroxyl group is disclosed (Patent Document 1). Further, a polishing tool is disclosed in which a hydrophilic substance is further added to a material constituting the polishing tool or a hydrophilic group is added (modified) (Patent Document 2). Further, a polishing pad made of a thermosetting polymer matrix resin containing a sheet that is hydrophilic and substantially insoluble in water is disclosed (Patent Document 3). Furthermore, a polishing pad made of a polyurethane composition containing a urethane resin copolymerized with a compound having a hydrophilic group and containing a hydrophilic agent is disclosed (Patent Document 4).

  However, when the polishing pad itself is made hydrophilic, there is a problem in that the discharge performance of the slurry containing polishing waste is deteriorated and the polishing rate is gradually reduced.

  On the other hand, in order to impart excellent demoldability, surface smoothness, and adhesion in coating to a thermosetting urethane resin, a technique using a one-end diol polysiloxane as a raw material for an NCO-terminated prepolymer has been proposed ( Patent Document 5).

JP 2002-134445 A JP 2003-11066 A JP 2002-59358 A JP 2003-128910 A JP-A-7-133337

  An object of this invention is to provide the polishing pad excellent in polishing-rate stability, and its manufacturing method.

  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.

The present invention provides a polishing pad having a polishing layer comprising a polyurethane resin foam obtained by a mechanical foaming method, wherein the polyurethane resin foam is represented by an isocyanate component, a high molecular weight polyol, and the following general formula (1): A reaction cured product of a polyurethane raw material composition comprising an isocyanate-terminated prepolymer containing a polysiloxane group-containing diol and a chain extender;
Content of the said polysiloxane group containing diol is related with the polishing pad characterized by being 1 to 5 weight% in a polyurethane raw material composition.

(In the formula, R ₁ is an alkyl group having 1 to 12 carbon atoms, n is an integer of 10 to 380, and m is an integer of 1 to 12).

  By using the polysiloxane group-containing diol represented by the general formula (1) as a raw material for the isocyanate-terminated prepolymer, the polyurethane resin foam can be hydrophobized. As a result, since the slurry discharging property of the polishing layer is improved, the water absorption and swelling properties of the polishing layer are reduced, so that a reduction in polishing rate can be suppressed even when a polishing operation is performed for a long time. .

  In addition, in the polishing of a Cu film having a strong chemical polishing action, when the polishing layer is hydrophilic, the slurry after the chemical reaction tends to remain on the polishing layer. The speed tends to decrease gradually. By using a polishing layer made of a polyurethane resin foam that has been hydrophobized, it is possible to quickly discharge a chemically-reacted slurry without leaving it on the polishing layer, and to supply a new slurry quickly. And the polishing rate can be kept high.

  It is necessary to introduce the polysiloxane group-containing diol into the isocyanate-terminated prepolymer in advance. When a polysiloxane group-containing diol is added alone to the polyurethane raw material composition, bubbles are broken even when a silicone surfactant (foam stabilizer) is added during mechanical foaming, producing a micro-bubble polyurethane resin foam. It becomes difficult to do.

  The content of the polysiloxane group-containing diol is 1 to 5% by weight in the polyurethane raw material composition. When the content of the polysiloxane group-containing diol is less than 1% by weight, the polyurethane resin foam cannot be sufficiently hydrophobized, so that it is difficult to suppress a decrease in the polishing rate. On the other hand, when it exceeds 5% by weight, even if a silicon surfactant (foam stabilizer) is added at the time of mechanical foaming, bubbles are broken and it becomes difficult to produce a polyurethane resin foam with fine bubbles.

  The hydroxyl value of the polysiloxane group-containing diol is preferably 7 to 120 mgKOH / g. When the hydroxyl value is less than 7 mgKOH / g, the polyurethane resin foam has insufficient hydrophobicity, and the intended effect tends to be difficult to obtain. On the other hand, when it exceeds 120 mgKOH / g, the compatibility with other raw materials is deteriorated and mechanical properties are lowered, or the hydrophobicity of the polyurethane resin foam is too strong and the polishing rate tends to be lowered. .

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 silicon surfactant is first added to a first component containing an isocyanate-terminated prepolymer containing an isocyanate component, a high molecular weight polyol, and a polysiloxane group-containing diol represented by the following general formula (1). Add to 0.05 to 10% by weight with respect to the total weight of the component and the second component, and further stir the first component with a non-reactive gas to disperse the non-reactive gas as fine bubbles. And preparing a polyurethane resin foam by mixing a second component containing a chain extender in the cell dispersion and curing the prepared cell dispersion.
The content of the polysiloxane group-containing diol is 1 to 5% by weight based on the total weight of the first component and the second component.

(In the formula, R ₁ is an alkyl group having 1 to 12 carbon atoms, n is an integer of 10 to 380, and m is an integer of 1 to 12).

  According to this production method, a polyurethane resin foam having a uniform fine cell structure can be obtained.

  The silicon-based surfactant needs to be added so as to be 0.05 to 10% by weight with respect to the total weight of the first component and the second component. When the amount of the silicon-based surfactant is less than 0.05% by weight, a fine-bubble foam tends to be not obtained. On the other hand, when it exceeds 10% by weight, the number of bubbles in the foam becomes too large, and it tends to be difficult to obtain a polyurethane resin foam having high hardness.

  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 higher hydrophobicity than conventional polishing pads, and improves the slurry drainability of the polishing layer and decreases the water absorption and swelling properties of the polishing layer. Even if it is a case, the fall of a grinding | polishing rate can be suppressed. In addition, when the polishing pad of the present invention is used for Cu film polishing, it is possible to quickly discharge a chemically-reacted slurry without remaining on the polishing layer, and to supply a new slurry quickly. And the polishing rate can be kept high.

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 isocyanate-terminated prepolymer used in the present invention contains at least an isocyanate component, a high molecular weight polyol, and a polysiloxane group-containing diol represented by the following general formula (1) as raw material components.


(In the formula, R ₁ is an alkyl group having 1 to 12 carbon atoms, n is an integer of 10 to 380, and m is an integer of 1 to 12).

  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. Among these, it is preferable to use polytetramethylene ether glycol from the viewpoint of enhancing the mechanical properties of the polishing layer and the hydrophobicity of the polishing layer.

  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 (hydroxy) Chill) 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. The blending amount of these low molecular weight polyols, low molecular weight polyamines and the like is not particularly limited and is appropriately determined depending on the properties required for the polishing pad, but is preferably 20 to 70 mol% of the total polyol components.

The polysiloxane group-containing diol represented by the general formula (1) is introduced into the isocyanate-terminated prepolymer by reaction with the isocyanate component. Since the prepolymer has a polysiloxane group in the side chain, it can impart hydrophobicity to the polyurethane resin. In the general formula (1), R ₁ is preferably a butyl group, and m is preferably 3.

  The polysiloxane group-containing diol preferably has a hydroxyl value of 7 to 120 mgKOH / g, more preferably 20 to 120 mgKOH / g.

The polysiloxane group-containing diol can be synthesized, for example, by dehydrating and condensing a polysiloxane having a hydroxyl group and trimethylolpropane. Commercial examples of the polysiloxane group-containing diol, for example, FM-DA11 (Chisso Corporation, _{R 1:} butyl group, m: 3, weight average molecular weight: 1000, hydroxyl value: 112.2mgKOH / g), FM-DA21 (Chisso Corporation, R ₁ : butyl group, m: 3, weight average molecular weight: 5000, hydroxyl value: 22.4 mgKOH / g), FM-DA26 (Chisso Corporation, R ₁ : butyl group, m: 3, weight average molecular weight: 15000, hydroxyl value: 7.5 mg KOH / g) and the like.

  The polysiloxane group-containing diol needs to be blended in the polyurethane raw material composition so as to be 1 to 5% by weight, and preferably 1 to 3% by weight.

The isocyanate-terminated prepolymer uses the polyol, a polysiloxane group-containing diol, and an isocyanate component, and has an equivalent ratio (NCO / H ^* ) of isocyanate group (NCO) to active hydrogen (H ^* ) of 1.2 to 5. It is produced by heating reaction in the range of 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, when it exceeds 5.0, a large amount of unreacted isocyanate remains, so that the reaction with the chain extender is accelerated and the molding processability of the polyurethane resin foam tends to deteriorate.

  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.

  In the production of the polyurethane resin foam, the first component containing the isocyanate-terminated prepolymer and the second component containing the chain extender are mixed and cured.

  As a method for producing a polyurethane resin foam, a mechanical foaming method (including a mechanical floss method) is used.

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

  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 amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

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

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

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

  The polyurethane resin foam preferably has a hardness of 40 to 70 degrees as measured by 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 polyurethane resin foam preferably has a water absorption of 3.8% or less, more preferably 3.5% or less. The polyurethane resin foam preferably has a bending elastic change rate (wet / dry) of 40% or less, more preferably 35% or less. In addition, the measuring method of each said physical property is based on description of an Example.

  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 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 weight average molecular weight of polyol component)
The weight 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.

(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).

(Measurement of water absorption)
The measurement was performed according to JIS K7312. A sample obtained by cutting out the produced polyurethane resin foam into a size of width 20 mm × length 50 mm × thickness 1.27 mm was used as a sample. The sample was immersed in distilled water at 25 ° C. for 48 hours, and the water absorption was calculated by substituting the weight before and after immersion into the following formula.
Water absorption rate (%) = [(weight after immersion−weight before immersion) / weight before immersion] × 100

(Measurement of bending elastic change rate)
A sample obtained by cutting the produced polyurethane resin foam into a size of 1 cm in width, 3 cm in length, and 2 mm in thickness was used as a sample. Using a 5864 tabletop test system manufactured by Instron as a measuring device, the stress and strain of the sample under the conditions of the distance between the intersections of the bending strength measuring jig 22 mm, the crosshead speed 0.6 mm / min, and the displacement 6.0 mm. Was measured, and the flexural modulus was calculated by the following formula.
Flexural modulus = (Stress difference between two points on a straight line) / (Strain difference between the same two points)
Further, the sample was immersed in distilled water at 23 ° C. ± 2 ° C. for 48 hours, and then the flexural modulus was calculated by the same method as described above.
The bending elastic change rate was calculated by the following formula.
Bending elastic change rate (%) = (bending elastic modulus before dipping−bending elastic modulus after dipping) / (bending elastic modulus before dipping) × 100

(Measurement of polishing rate)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as the polishing apparatus, the polishing rate was measured using the prepared polishing pad. The polishing rate was as follows: a thermal oxide film of 2000 mm, Ta100 mm, TaN100 mm, and Cu-seed 800 mm were deposited in this order on an 8-inch silicon wafer, and a Cu plating of 25000 mm was formed thereon and polished for 60 seconds. It was calculated from the polishing amount at this time. The initial polishing rate was the fourth polishing rate. The late polishing rate was the 12th polishing rate. And the polishing rate maintenance rate was computed by the following formula.
Polishing rate maintenance rate (%) = [1-{(initial polishing rate−late polishing rate) / initial polishing rate}] × 100
A non-contact resistance measuring system (manufactured by Napson, Model-NC-80M) was used for the film thickness measurement of the Cu film. As polishing conditions, a slurry prepared by adding 1 wt% of hydrogen peroxide to a neutral slurry for Cu (manufactured by Fujimi Incorporated, PL7101) was added at a flow rate of 200 ml / min. The polishing load was 2 psi, the polishing platen rotation speed was 70 rpm, and the wafer rotation speed was 70 rpm. After the prepared polishing pad was attached to the platen, the surface of the polishing pad was dressed for 30 minutes using a diamond abrasive disc (M # 100, manufactured by Asahi Diamond Co., Ltd.). The dressing conditions were a disk load of 0.6 psi, a polishing surface plate rotation speed of 30 rpm, and a disk rotation speed of 15 rpm.

Example 1
In a container, 1173 parts by weight of toluene diisocyanate (mixture of 2,4-form / 2,6-form = 80/20), 264 parts by weight of isophorone diisocyanate, polysiloxane group-containing diol A represented by the general formula (1) Ltd., FM-DA11, R ₁ : butyl group, m: 3, weight average molecular weight: 1000, hydroxyl value: 112.2 mgKOH / g) 48 parts by weight, polytetramethylene ether glycol 1638 parts by weight of weight average molecular weight 1000, 283 parts by weight of polytetramethylene ether glycol having a weight average molecular weight of 650 and 195 parts by weight of diethylene glycol were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer A (NCO wt%: 9.25 wt%).
100 parts by weight of the prepolymer and 3 parts by weight of a silicon surfactant (manufactured by Goldschmidt, B8465) were added to the polymerization vessel, 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. Thereto was added 26.4 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. (NCO Index: 1.1). 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 put in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block.
The polyurethane foam block heated to about 80 ° C. was sliced using a slicer (AGW Tech, VGW-125) to obtain a polyurethane foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing layer. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Furthermore, the surface of the cushion sheet (Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) subjected to corona treatment was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Examples 2-5, Comparative Examples 1-4
A polishing pad was prepared in the same manner as in Example 1 except that the formulation shown in Table 1 was adopted. However, in Comparative Example 2, the polysiloxane group-containing diol was added together with 4,4′-methylenebis (o-chloroaniline) during curing without being introduced into the isocyanate-terminated prepolymer. The polysiloxane group-containing diols B and C in Table 1 are as follows.
Polysiloxane group-containing diol B represented by the general formula (1) (Chisso Corporation, FM-DA21, R ₁ : butyl group, m: 3, weight average molecular weight: 5000, hydroxyl value: 22.4 mgKOH / g)
Polysiloxane group-containing diol C represented by the general formula (1) (Chisso Corporation, FM-DA26, R ₁ : butyl group, m: 3, weight average molecular weight: 15000, hydroxyl value: 7.5 mgKOH / g)

  The polishing pad of the present invention is used to flatten optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing. Used for processing. In particular, the polishing pad of the present invention is suitably used in a step of planarizing a semiconductor device having a Cu film (including a Cu alloy film) formed on a wafer to form a Cu wiring pattern.

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 (4)

In the polishing pad having a polishing layer made of Polyurethane resin foam, the polyurethane resin foam comprising an isocyanate component, a polysiloxane group-containing diol represented by the high molecular weight polyol, and the following general formula (1) It is a reaction cured product of a polyurethane raw material composition containing an isocyanate-terminated prepolymer and a chain extender,
The polishing pad according to claim 1, wherein the content of the polysiloxane group-containing diol is 1 to 5% by weight in the polyurethane raw material composition.

(In the formula, R ₁ is an alkyl group having 1 to 12 carbon atoms, n is an integer of 10 to 380, and m is an integer of 1 to 12).   The polishing pad according to claim 1, wherein the polysiloxane group-containing diol has a hydroxyl value of 7 to 120 mgKOH / g. 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 silicon surfactant is first added to a first component containing an isocyanate-terminated prepolymer containing an isocyanate component, a high molecular weight polyol, and a polysiloxane group-containing diol represented by the following general formula (1). Add to 0.05 to 10% by weight with respect to the total weight of the component and the second component, and further stir the first component with a non-reactive gas to disperse the non-reactive gas as fine bubbles. And preparing a polyurethane resin foam by mixing a second component containing a chain extender in the cell dispersion and curing the prepared cell dispersion.
Content of the said polysiloxane group containing diol is 1 to 5 weight% with respect to the total weight of a 1st component and a 2nd component, The manufacturing method of the polishing pad characterized by the above-mentioned.

(In the formula, R ₁ is an alkyl group having 1 to 12 carbon atoms, n is an integer of 10 to 380, and m is an integer of 1 to 12). A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.