JP2007077207A - Method for producing fine cell polyurethane foam and polishing pad made of fine cell polyurethane foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably producing a fine cell polyurethane foam containing uniformly dispersed cells and provide a polishing pad having excellent polishing performance and produced by using the fine cell polyurethane foam. <P>SOLUTION: The fine cell polyurethane foam is produced by using a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen-containing compound as main components, adding a silicon-based surfactant to at least one of the first component and the second component, stirring the product together with a non-reactive gas to prepare a foam-dispersed liquid containing the gas in the form of fine cells, mixing the remaining components to the foam-dispersed liquid and curing the mixture. The time (pot life) from the mixing of the first component and the second component to the state to start the hardening and lose the fluidity is 2-5 min. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing a fine-cell polyurethane foam that is optimal for a polishing layer of a polishing pad used when planarizing unevenness on a wafer surface by chemical mechanical polishing, and a polishing pad.

When manufacturing a semiconductor device, a process of forming a conductive layer on the wafer surface and forming a wiring layer by photolithography, etching, or the like, a process of forming an interlayer insulating film on the wiring layer, etc. These steps are performed, and irregularities made of a conductor such as metal or an insulator are generated on the wafer surface. In recent years, miniaturization of wiring and multilayer wiring have been advanced for the purpose of increasing the density of semiconductor integrated circuits, and along with this, technology for flattening the irregularities on the wafer surface has become important.

As a method for flattening the unevenness of the wafer surface, a chemical mechanical polishing (hereinafter referred to as CMP) method is generally employed. CMP is a technique of polishing using a slurry-like polishing agent (hereinafter referred to as slurry) in which abrasive grains are dispersed in a state where the surface to be polished of a wafer is pressed against the polishing surface of a polishing pad.

As a polishing pad used for high-precision polishing, a polishing pad in which hollow microspheres containing high-pressure gas are dispersed in a matrix resin such as polyurethane as described in Japanese Patent No. 3013105 (Patent Document 1). Is widely known.

In addition, JP-A-11-322877 (Patent Document 2) and JP-A-11-322878 (Patent Document 3) propose a polishing pad in which heat-expandable micro hollow spheres and expanded polystyrene beads are dispersed in polyurethane. In JP-A-2000-343412 (Patent Document 4), JP-A-2000-344850 (Patent Document 5), and JP-A 2000-344902 (Patent Document 6), micro hollow spheres expanded in polyurethane, heated and expanded. A polishing pad in which bubbles having different diameters are dispersed by combining a water-soluble hollow sphere and water is proposed.

As a means for producing the cell-dispersed polyurethane for forming these polishing pads, a general method is a method in which an isocyanate component-containing compound is mixed in advance with a component (such as a fine hollow sphere) that becomes a bubble, and an active hydrogen group-containing compound is added and reacted. It is. At this time, in order to uniformly disperse the bubbles in the polyurethane, it can be said that the time (pot life) until the isocyanate group-containing compound and the active hydrogen group-containing compound start to react and lose fluidity is a very important factor. . However, detailed discussion is not made in the above-mentioned Japanese Patent No. 3013105, Japanese Patent Laid-Open No. 11-322877, and the like.

In addition to the polyurethane in which these conventional micro hollow spheres are dispersed, a polyurethane sheet optimal for the polishing layer of the polishing pad can be produced from a micro-bubble polyurethane foam in which a gas is mechanically taken. Similarly, in the production of a microcellular polyurethane foam, the time (pot life) until the isocyanate group-containing compound and the active hydrogen group-containing compound start to react and lose fluidity can be said to be a very important factor.

However, the polishing pad is not discussed in detail regarding pot life.
Japanese Patent No. 3013105 Japanese Patent Laid-Open No. 11-322877 Japanese Patent Laid-Open No. 11-322878 JP 2000-343412 A JP 2000-344850 A JP 2000-344902 A

It is strongly desired that the polishing pad has stable polishing characteristics. For that purpose, when the polishing pad (polishing layer) is made of a cell-dispersed polyurethane, the cells need to be uniformly dispersed in the polyurethane, and it is necessary to stably produce such polyurethane. is there. In particular, when the cell-dispersed polyurethane is made and then sliced to a predetermined thickness, more uniform cell dispersibility is required.

Accordingly, an object of the present invention is to provide a fine-cell polyurethane foam in which bubbles (bubbles) are uniformly dispersed and can be stably produced. Furthermore, another object of the present invention is to provide a polishing pad having excellent polishing characteristics from this microcellular polyurethane foam.

  As a result of intensive studies in view of the above situation, the present inventors have obtained an isocyanate group-containing compound and an active hydrogen group-containing compound in order to obtain a fine-cell polyurethane foam that forms a polishing pad (polishing layer). It has been found that the above-mentioned problem can be solved by setting the time (pot life) until loss of fluidity within a certain range after starting the reaction.

That is, the present invention mainly comprises a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound, and a silicon-based surfactant is added to at least one of the first component or the second component. 0.1 to 6% by weight is added to the total amount of the first component and the second component, and the component to which the surfactant is further added is stirred with a non-reactive gas, and the non-reactive gas is made into fine bubbles. A method for producing a microcellular polyurethane foam, comprising: adjusting a cell dispersion dispersed as follows; and mixing and curing the remaining components in the cell dispersion, wherein the first component and the second component It is related with the manufacturing method of the fine foam polyurethane foam characterized by the time (pot life) until mixing loses fluidity | liquidity after mixing is 2-5 minutes.

In the present invention, a silicon surfactant is used to form fine bubbles. As the silicon-based surfactant, a silicon-based nonionic surfactant having no hydroxyl group is desirable because the physical properties of the polyurethane are not impaired and the bubbles are fine and uniform.

The addition amount of the silicon-based surfactant is 0.1 to 6% by weight with respect to the total amount of the first component and the second component. If it is less than 0.1% by weight, a foam having fine bubbles may not be obtained. On the other hand, if it exceeds 6% by weight, the number of cells in the fine-cell polyurethane foam increases, making it difficult to obtain a polyurethane foam with high hardness. Further, the hardness tends to decrease due to the plasticizing effect, and the addition amount of the silicon surfactant is preferably 0.1 to 6% by weight.

The non-reactive gas is a gas composed only of a normal temperature gas component that does not react with an isocyanate group or an active hydrogen group. The gas may be actively sent into the liquid, or only the situation where the gas is naturally involved during the stirring may be used. 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. Air that has been dried to remove moisture is most preferred in terms of cost.

The fine cell polyurethane foam has air bubbles having an average cell diameter (cell diameter) of 70 μm or less, preferably 50 μm or less.

In the manufacturing method of the microcellular polyurethane foam of this invention, the time (pot life) until it mixes a 1st component and a 2nd component and hardening starts and loses fluidity is 2 to 5 minutes. If it is less than 2 minutes, the time until the first component and the second component are mixed and poured into the shape of the polyurethane foam is too short, and it is difficult to obtain a uniform polyurethane due to poor mixing, and the operability is very high. Since it gets worse, it is not preferable. On the other hand, if the time exceeds 5 minutes, the first component and the second component are mixed and poured into the shape of the polyurethane foam, and then the time until curing is too long. It is not preferable because it becomes uneven in the direction. From the above, the pot life is desirably in the range of 2 to 5 minutes.

The pot life is a value measured according to JIS K 7301.

In the method for producing a microcellular polyurethane foam of the present invention, the isocyanate group-containing compound is an isocyanate group-terminated urethane prepolymer, and the isocyanate compound constituting the isocyanate group-terminated urethane prepolymer is an aromatic polyisocyanate compound (A1). And an aliphatic polyisocyanate compound (A2), and the ratio of A1 / A2 is 95/5 to 50/50 (molar ratio). In the urethane / ureaization reaction, aromatic isocyanate is faster in reaction than aliphatic isocyanate. Therefore, in order to adjust the pot life of the reaction between the first component containing the isocyanate group-containing compound and the second component containing the active hydrogen group-containing compound to 2 to 5 minutes, it is necessary to mix A1 and A2. When the ratio of A1 exceeds 95 mol%, the pot life is shortened, which is not preferable. If the proportion of A1 is less than 50 mol%, the pot life becomes too long, which is not preferable.

In the present invention, the aliphatic polyisocyanate compound is desirably a compound having an alicyclic structure. As described above, the pot life can be adjusted to the optimum range by mixing the aromatic polyisocyanate compound and the aliphatic polyisocyanate compound. On the other hand, however, mixing an aliphatic polyisocyanate compound makes it difficult to obtain a polyurethane having a high hardness as compared with a polyurethane composed only of an aromatic polyisocyanate compound. In order to obtain a microcellular polyurethane foam optimal for the polishing layer of the polishing pad, it is desirable that the polyurethane has a high hardness. However, if the aliphatic polyisocyanate compound has an alicyclic structure, a polyurethane having a relatively high hardness can be obtained.

The present invention relates to a polyurethane sheet (polishing layer) for a polishing pad comprising the fine-cell polyurethane foam. Since the polishing layer is a fine-cell polyurethane foam, the abrasive grains in the slurry can be held on the pad surface during the polishing operation, so that a satisfactory polishing rate can be obtained. When the fine-cell polyurethane foam is cut into a predetermined size of a polyurethane sheet for a polishing pad, it can be used as a polishing layer.

In the present invention, the polishing pad polyurethane sheet has a groove structure on the surface. A part of the groove structure may penetrate to the back surface. By using a fine foam polyurethane foam, it has many openings on the polishing surface and has the function of holding the slurry. However, in order to efficiently maintain the slurry and renew the slurry, In order to prevent destruction of the object to be polished due to adsorption with the object to be polished, it is preferable that the surface of the polishing layer has a groove structure (surface irregularities). There is no particular limitation as long as the surface shape holds and renews the slurry. For example, XY lattice grooves, concentric circular grooves, through holes, non-through holes, polygonal columns, cylinders, spiral grooves, eccentric circles And a combination of these grooves. These surface irregularities are generally regular, but the groove pitch, groove width, groove depth, etc. must be changed for each range to make the slurry retention and renewability desirable. Is also possible.

The present invention relates to a polishing pad obtained by bonding an underlayer to the back surface of the polyurethane sheet for polishing pad. The underlayer supplements the characteristics of the polishing layer. The underlying layer plays an important role in CMP in order to achieve both planarity and uniformity that are in a trade-off relationship. Planarity refers to the flatness of a pattern portion when an object to be polished having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire object to be polished. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the underlayer. In the polishing pad of the present invention, the underlayer is softer than the polishing layer.

The present invention relates to a polishing pad that uses a double-sided tape to bond a base layer to the back surface of the polyurethane sheet for polishing pad. As an advantage of using the double-sided tape, the composition of the polishing layer and the base layer may be different, so that the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive strength of each layer can be optimized.

The present invention relates to a polishing pad in which a double-sided tape is further bonded to the surface of the base layer opposite to the surface to which the polyurethane sheet for polishing pad is bonded. The advantage of using double-sided tape is that the composition of the base layer and the platen are often different, and the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force to the base layer and the platen can be optimized. Become.

The manufacturing method of the microcellular polyurethane foam of this invention has as a main component the 1st component containing an isocyanate group containing compound and the 2nd component containing an active hydrogen group containing compound.

As the isocyanate group-containing compound used in the present invention, an organic polyisocyanate compound known in the polyurethane field can be used without limitation. In particular, the use of a diisocyanate compound and a derivative thereof, particularly an isocyanate group-terminated prepolymer, is preferable because the physical properties of the resulting microcellular polyurethane foam are excellent. Incidentally, as a method for producing polyurethane, a prepolymer method and a one-shot method are known, but any method can be used in the present invention.

Examples of the organic polyisocyanate usable in the present invention include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, Aromatic diisocyanates such as 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1 Aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate Isocyanate, isophorone diisocyanate, alicyclic diisocyanates such as norbornane diisocyanate and the like.

As the organic polyisocyanate, 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.). These trifunctional or higher functional polyisocyanate compounds are preferably used by adding to the diisocyanate compound because they are easily gelled during prepolymer synthesis when used alone.

Use of these organic polyisocyanate compounds needs to satisfy the range of aromatic polyisocyanate compound (A1) / aliphatic polyisocyanate compound (A2) = 95/5 to 50/50 (molar ratio) as described above. .

In the present invention, the isocyanate group-containing compound suitable for use as the first component is an isocyanate prepolymer which is a reaction product of the above-described isocyanate compound and an active hydrogen group-containing compound. As such an active hydrogen group-containing compound, a polyol compound and a chain extender described later are used, and an equivalent ratio NCO / H ^{* of} the isocyanate group (NCO) and the active hydrogen (H ^* ) is 1.2 to 5.0. The isocyanate prepolymer which is an oligomer having an isocyanate group terminal is produced by a heat reaction in the range of preferably 1.6 to 2.6. The use of commercially available isocyanate prepolymers is also suitable.

The active hydrogen group-containing compound used in the present invention is an organic compound having at least two or more active hydrogen atoms, and is a compound usually referred to as a polyol compound or a chain extender in the technical field of polyurethane.

The active hydrogen group is a functional group containing hydrogen that reacts with an isocyanate group, and examples thereof include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH).

Examples of the polyol compound include those usually used as a polyol compound in the technical field of polyurethane. For example, polyester polyols such as polytetramethylene ether glycol and polyethylene glycol, polyester polyols such as polybutylene adipate, polycaprolactone polyol, and polyesters such as polycaprolactone A polyester polycarbonate polyol or an ethylene carbonate exemplified by a reaction product of glycol and alkylene carbonate is reacted with a polyhydric alcohol, and then the obtained reaction mixture is reacted. Examples thereof include polyester polycarbonate polyol reacted with an organic dicarboxylic acid, and polycarbonate polycarbonate obtained by transesterification of a polyhydroxyl compound with aryl carbonate. These may be used alone or in combination of two or more.

The number average molecular weights of these polyol compounds are not particularly limited, but are preferably 500 to 2,000 from the viewpoint of the elastic characteristics of the resulting fine-cell polyurethane foam.

When the number average molecular weight of the polyol compound is less than 500, the fine-cell polyurethane foam obtained by using the polyol compound does not have sufficient elastic properties and easily becomes a brittle polymer. It may become too hard and may cause scratches on the polished surface of the workpiece to be polished. 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, if the number average molecular weight exceeds 2000, the polishing layer made of a fine-cell polyurethane foam obtained by using this becomes soft, and a sufficiently satisfactory planarity cannot be obtained.

Examples of the polyol compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, in addition to the above-described high molecular weight polyol. 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene and other low molecular weight polyols may be used in combination. . These polyol compounds may be used alone or in combination of two or more.

Among the active hydrogen group-containing compounds, what is called a chain extender is a compound having a molecular weight of about 500 or less. Specifically, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3- Aliphatic low molecular weight glycols and triols typified by methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, trimethylolpropane, etc., 1,4-bis (2-hydroxyethoxy) benzene, m-xylylene diene Aromatic diols represented by ol, etc., 4,4′-methylenebis (o-chloroaniline), 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′-dimethyldiphenylmethane, and other polyamines. These may be used alone or in combination of two or more.

The ratio of the organic polyisocyanate, the polyol compound, and the chain extender in the present invention can be variously changed depending on the molecular weight of each and the desired physical properties of a polyurethane (for example, a polishing pad) produced therefrom. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the organic polyisocyanate with respect to the total number of functional groups of the polyol compound and the chain extender is desirably in the range of 0.95 to 1.15. It is more desirable that it is 99 to 1.10.

Polyurethane can be produced by applying known urethanization techniques such as a melting method and a solution method, but for the fine-celled polyurethane foam of the present invention, it is necessary to incorporate bubbles into the polyurethane, and further, the cost, In consideration of working environment and the like, it is preferable to manufacture by a melting method.

The said microcellular polyurethane foam mixes and hardens the 1st component containing an isocyanate group containing compound and the 2nd component containing an active hydrogen group containing compound. In the prepolymer method, the isocyanate-terminated prepolymer becomes an isocyanate group-containing compound, and the chain extender becomes an active hydrogen group-containing compound. In the one-shot method, the organic polyisocyanate becomes an isocyanate group-containing compound, and the chain extender and the polyol compound become active hydrogen group-containing compounds.

In the present invention, a stabilizer such as an antioxidant, a surfactant, a lubricant, a pigment, a filler, an antistatic agent, and other additives may be added to the polyurethane as necessary.

As a method for producing the fine foam polyurethane foam, there is a method of adding hollow beads, a foaming method by a chemical foaming method, etc., but from the viewpoint of uniform dispersibility of the bubbles, cost, etc., the mechanical foaming method Is desirable. In the mechanical foaming method, a polyurethane raw material (a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound) is mixed or stirred before mixing or stirring into the polyurethane raw material. Generally, a method of taking a bubble made of a non-reactive gas and then curing and foaming to produce a fine-cell polyurethane foam is adopted.

At that time, a silicone-based surfactant is added as a foam stabilizer to the polyurethane raw material (the first component containing the isocyanate group-containing compound and / or the second component containing the active hydrogen group-containing compound), and the surface activity is increased. Stirring the component to which the agent is added with a non-reactive gas and dispersing it as fine bubbles, then mixing the remaining components with this is a very effective means for stably producing fine bubbles. .

A foam stabilizer that does not react with the polyurethane raw material and can stably form fine bubbles can be used without limitation, but the physical properties of polyurethane are not impaired, and uniform fine bubbles are stably produced. From this point of view, a silicon-based surfactant is preferable. In particular, a surfactant of a copolymer of silicon and polyether is preferable. Here, examples of the polyether include polyethylene oxide, polypropylene oxide, and copolymers thereof. As such a silicon surfactant, SH-192 (manufactured by Toray Dow Corning Silicon) and the like are exemplified as a suitable compound.

As described above, the addition amount of the foam stabilizer is preferably 0.1 to 6% by weight with respect to the polyurethane. If it is less than 0.1% by weight, a fine foam having bubbles may not be obtained. From this viewpoint, it is preferable that the amount of foam stabilizer added is 1% by weight or more. On the other hand, if it exceeds 6% by weight, the number of cells in the polyurethane fine foam increases, and it is difficult to obtain a polyurethane foam with high hardness. From this point of view, the amount of foam stabilizer added is preferably 6% by weight or less.

The non-reactive gas is a gas composed only of a normal temperature gas component that does not react with an isocyanate group or an active hydrogen group. The gas may be actively sent into the liquid, or only the situation where the gas is naturally involved during the stirring may be used. 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. Air that has been dried to remove moisture is most preferred in terms of cost.

As a stirring device for dispersing non-reactive gas into a polyurethane raw material containing a silicon-based surfactant, particularly an isocyanate group-containing compound, in the form of fine bubbles, a known stirring device can be used without any particular limitation. Is exemplified by a homogenizer, a dissolver, a two-axis planetary mixer (planetary mixer), and the like. The shape of the stirring blade of the stirring device is not particularly limited, but the use of a whipper type stirring blade is preferable because fine bubbles can be obtained.

In addition, it is also a preferable aspect that the stirring in the dispersion | distribution process which produces a cell dispersion | distribution isocyanate group containing compound liquid and the stirring in the mixing process which adds a chain extension agent use a different stirring apparatus. 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 dispersion step and the mixing step, and it is also preferable to use the stirring device by adjusting the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

In the method for producing a microcellular polyurethane foam, heating and post-curing the foam that has reacted until the cell dispersion is poured into the mold and no longer flows has the effect of improving the physical properties of the foam, Very suitable. The bubble dispersion may be poured into the mold and immediately placed in a heating oven for post-cure. Under such conditions, heat is not immediately transferred to the reaction components, so the bubble diameter does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

In the production of the fine-cell polyurethane foam, a known catalyst for promoting a polyurethane reaction such as tertiary amine or organic tin 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, and its use is particularly effective when the pot life is too long.

The production of the fine-cell polyurethane foam is a batch method in which each component is weighed and put into a container and stirred. Alternatively, each component and a non-reactive gas are continuously supplied to the stirring device and stirred. It may be a continuous production method in which a cell dispersion is sent out to produce a molded product.

The microcellular polyurethane foam is sliced to a thickness suitable for a polishing pad sheet (polishing layer). The thickness of the polishing layer is about 0.8 mm to 2 mm, and a sheet having a thickness of about 1.2 mm is usually used. In addition to this method, the polyurethane component may be poured into a mold having a cavity having the same thickness as the target polishing layer.

The surface of the polishing layer preferably has a groove structure (surface irregularities) in order to efficiently maintain the slurry and renew the slurry, and also to prevent destruction of the object to be polished due to adsorption with the object to be polished. . There is no particular limitation as long as the surface shape holds and renews the slurry. For example, XY lattice grooves, concentric circular grooves, through holes, non-through holes, polygonal columns, cylinders, spiral grooves, eccentric circles And a combination of these grooves. In addition, these groove structures are generally regular, but the groove pitch, groove width, groove depth, etc. may be changed for each range in order to make the slurry retention and renewability desirable. Is also possible. The shape of the groove is not particularly limited, but the cross section may be rectangular, triangular, U-shaped, semicircular, etc., and may have a cross-sectional area through which fine powder passes.

The method for producing the groove structure on the surface of the polishing layer is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, or a mold having a predetermined surface shape before curing. Using a method in which microcellular polyurethane is poured and cured, a method in which microcellular polyurethane foam is pressed by a press plate having a predetermined surface shape, a method in which photolithography is used, and a printing method And a production method using a laser beam using a carbon dioxide laser or the like.

The underlayer to be bonded to the back surface of the polishing pad polyurethane sheet (polishing layer) is not limited as long as it is softer than the polishing layer. For example, fiber nonwoven fabrics such as polyester nonwoven fabric, nylon nonwoven fabric and acrylic nonwoven fabric, resin impregnated nonwoven fabrics such as polyester nonwoven fabric impregnated with polyurethane, polymer resin foams such as polyurethane foam and polyethylene foam, rubber properties such as butadiene rubber and isoprene rubber Examples thereof include resins and photosensitive resins.

As the double-sided tape for bonding the polyurethane sheet for the polishing pad (polishing layer) and the base layer, one having a general configuration in which an adhesive layer is provided on both sides of the substrate can be used. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of preventing the slurry from penetrating into the underlayer, 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 undercoat layer 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 double-sided tape to be applied to the surface of the underlayer opposite to the polishing layer has a general configuration in which an adhesive layer is provided on both surfaces of the substrate 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. In addition, the composition of the base layer and the platen is often different, and the composition of each adhesive layer of the double-sided tape is made different so that the adhesive force to the base layer and the platen can be optimized.

It can be said that the microcellular polyurethane foam of the present invention has excellent cell dispersibility and can be stably produced. In addition, the polishing pad of the present invention has a polishing property with a high polishing rate and excellent flatness.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[Measuring method]
(Pot life measurement)
Measured according to JIS K 7301 (Test Method 7.1 Pot Life for Tolylene Diisocyanate Type Prepolymer for Thermosetting Urethane Prepolymer). As a curing agent, 4,4′-methylenebis (o-chloroaniline) (Iharacamine MT manufactured by Ihara Chemical Co., Ltd.) was used.

(Average bubble diameter measurement)
A sample cut in parallel with a microtome cutter as thin as possible to 1 mm or less was used as an average bubble diameter measurement sample. The sample was fixed on a slide glass and measured using an image processing apparatus (Image Analyzer V10 manufactured by Toyobo Co., Ltd.).

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. A sample cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) was 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%. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Hardness measurement)
This was performed in accordance with JIS K6253-1997. A sample cut into a size of 2 cm × 2 cm (thickness: arbitrary) was used as a sample for hardness measurement, and allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 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 (Asker D-type hardness meter manufactured by Kobunshi Keiki Co., Ltd.).

(Storage elastic modulus measurement)
This was performed in accordance with JIS K7198-1991. A 3 mm x 40 mm strip (thickness; arbitrary) cut out was used as a sample for dynamic viscoelasticity measurement, and was allowed to stand in a container containing silica gel for 4 days under an environmental condition of 23 ° C. The accurate width and thickness of each sheet after cutting was measured with a micrometer. The storage elastic modulus E ′ was measured using a dynamic viscoelastic spectrometer (manufactured by Iwamoto Seisakusho, currently IS Engineering Co., Ltd.). The measurement conditions at that time are shown below.
Measurement conditions Measurement temperature: 40 ° C
Applied strain; 0.03%
Initial load: 20g
Frequency: 1 Hz

(Bubble dispersibility evaluation)
When slicing microcellular polyurethane foam into a sheet with the optimum thickness for the polishing layer, what is the specific gravity of the sheet near the top, the sheet at the middle part, and the sheet near the bottom when viewed in the thickness direction? I saw if they were ready. As the variation, the difference between the maximum value and the minimum value of the measured values at the three sites was used.

(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 the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. 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 shaving. 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 above two types of patterns have a step height of 2000 mm The amount of scraping of the 270 μm space was measured as follows. 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
Isocyanate group-containing compound 1
Toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20: hereinafter abbreviated as TDI) 33.9 parts by weight, 4,4′-dicyclohexylmethane diisocyanate (hereinafter abbreviated as HMDI) An isocyanate-terminated prepolymer (5.7 parts by weight) obtained from 54.6 parts by weight of polytetramethylene glycol (hereinafter abbreviated as PTMG) having a number average molecular weight of 1008 and 5.7 parts by weight of diethylene glycol (hereinafter abbreviated as DEG) ( Hereinafter, the composition molar ratio of the isocyanate group-containing compound 1 and the pot life of the reaction with 4,4′-methylenebis (o-chloroaniline) are as shown in Table 1.

Production of microcellular polyurethane foam In a reaction vessel coated with Teflon (registered trademark), 100 parts by weight of filtered isocyanate group-containing compound 1 (isocyanate group concentration 2.17 meq / g) and filtered silicon-based surface activity 3 parts by weight of an agent (SH192 manufactured by Toray Dow Corning Silicone) was mixed, and the reaction temperature was adjusted to 80 ° C. Using a Teflon (registered trademark) -coated stirring blade, vigorous stirring was performed so that bubbles were taken into the reaction system at a rotation speed of 900 rpm. Thereto, 27.0 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Iharacuamine MT: hereinafter abbreviated as MBOCA), which was previously melted at 120 ° C. and filtered, was added. After stirring for about 1 minute, the reaction solution was poured into a pan-type open mold coated with Teflon (registered trademark). When the fluidity of the reaction solution disappeared, it was placed in an oven and post-cured at 110 ° C. for 6 hours to obtain a microcellular polyurethane foam.

Production of fine foam polyurethane foam sheet and polishing pad A fine foam polyurethane foam sheet for a polishing pad was obtained from this fine foam polyurethane foam using a band saw type slicer (manufactured by Fecken). Next, this sheet was subjected to surface buffing to a predetermined thickness using a buffing machine (manufactured by Amitech Co., Ltd.) to obtain a sheet with a precise thickness.

Table 2 shows the cell dispersibility of the foam.

As a representative characteristic, a sheet at an intermediate portion of the foam was used for the following evaluation. Table 3 shows the average cell diameter, specific gravity, hardness, and storage elastic modulus of the obtained microcellular polyurethane foam sheet.

The buffed sheet is punched into a predetermined diameter, and a concentric groove with a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm is formed on the surface using a groove processing machine. The sheet that will be completed. A double-sided tape (double tack tape manufactured by Sekisui Chemical Co., Ltd.) was applied to the surface (polished surface) opposite to the grooved surface of this sheet using a laminator. Furthermore, as a base layer, a buffed and corona-treated polyethylene foam (Toray Pef manufactured by Toray Industries, Inc., thickness 0.8 mm) is bonded using a laminating machine, and the surface of the base layer bonded to the polishing layer A double-sided tape was bonded to the opposite surface using a laminator to prepare a polishing pad.

The polishing characteristics of the obtained polishing pad were as shown in Table 3.

Example 2
Isocyanate group-containing compound 2
Isocyanate-terminated prepolymer (hereinafter referred to as isocyanate group) obtained by using 25.0 parts by weight of TDI, 20.3 parts by weight of HMDI, 48.6 parts by weight of PTMG having a number average molecular weight of 844, and 6.1 parts by weight of DEG. The composition molar ratio and pot life of abbreviated to compound 2 were as shown in Table 1.

Production of microcellular polyurethane foam, sheet, and polishing pad As in Example 1, except that the isocyanate group-containing compound 1 was changed to the isocyanate group-containing compound 2 (isocyanate group concentration 2.12 meq / g). went. The evaluation results are shown in Tables 2 and 3.

Example 3
Isocyanate group-containing compound 3
Isocyanate-terminated prepolymer (hereinafter referred to as isocyanate group) obtained by using 30.8 parts by weight of TDI, 19.9 parts by weight of HMDI, 42.4 parts by weight of PTMG having a number average molecular weight of 645, and 7.0 parts by weight of DEG. The composition molar ratio and the pot life of the abbreviated compound 3 were as shown in Table 1.

Production of fine-cell polyurethane foam, sheet, and polishing pad: Isocyanate group-containing compound 1 to isocyanate group-containing compound 3 (isocyanate group concentration 2.42 meq / g), and MBOCA amount to 31.2 parts by weight The procedure was the same as in Example 1 except for the change. The evaluation results are shown in Tables 2 and 3.

Example 4
Isocyanate group-containing compound 4
An isocyanate-terminated prepolymer (hereinafter referred to as isocyanate) obtained by using 25.2 parts by weight of TDI, 8.4 parts by weight of HMDI, 54.0 parts by weight of PTMG having a number average molecular weight of about 1000, and 5.7 parts by weight of DEG. The composition molar ratio and the pot life of the abbreviated group-containing compound 4 were as shown in Table 1.

Production of microcellular polyurethane foam, sheet, and polishing pad: Isocyanate group-containing compound 1 to isocyanate group-containing compound 4 (isocyanate group concentration 2.22 meq / g), and MBOCA amount to 26.0 parts by weight The procedure was the same as in Example 1 except for the change. The evaluation results are shown in Tables 2 and 3.

Comparative Example 1
Isocyanate group-containing compound 5
Isocyanate-terminated prepolymer (hereinafter referred to as isocyanate group) obtained by using 37.5 parts by weight of TDI, 1.2 parts by weight of HMDI, 55.5 parts by weight of PTMG having a number average molecular weight of 1008, and 5.8 parts by weight of DEG. The composition molar ratio and the pot life of the abbreviated compound 5 were as shown in Table 1.

Production of microcellular polyurethane foam, sheet, and polishing pad As in Example 1, except that the isocyanate group-containing compound 1 was changed to the isocyanate group-containing compound 5 (isocyanate group concentration 2.21 meq / g). went. However, solidification of the reaction solution started in the middle of pouring into the mold, and a fine-cell polyurethane foam could not be obtained.

Comparative Example 2
Isocyanate group-containing compound 6
Isocyanate-terminated prepolymer (hereinafter referred to as isocyanate group) obtained by using 13.8 parts by weight of TDI, 31.1 parts by weight of HMDI, 49.9 parts by weight of PTMG having a number average molecular weight of 1008, and 5.2 parts by weight of DEG. The composition molar ratio and pot life of the abbreviated compound 6) are as shown in Table 1.

Fine-cell polyurethane foam, sheet, and the production <br/> isocyanate group-containing compound 1 isocyanate group-containing compound of the polishing pad 6 (isocyanate group concentration 1.99meq / g), 25.0 parts by weight The amount of MBOCA The procedure was the same as in Example 1 except for the change. The evaluation results are shown in Tables 2 and 3.

As is apparent from Table 2, it can be seen that the microcellular polyurethane foam of the present invention has excellent cell dispersibility. That is, it can be said that stable production is possible. Moreover, it can be seen from Table 3 that the polishing pad of the present invention has a polishing property with a high polishing rate and excellent flatness.

Claims (4)

The main component is a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound, and at least one of the first component and the second component is a silicon surfactant as the first component and the second component. 0.1 to 6% by weight based on the total amount of the above, and further the component added with the surfactant is stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles After the liquid is adjusted, the remaining component is mixed and cured in the cell dispersion, and the method comprises the steps of mixing the first component and the second component, and curing the mixture. A method for producing a microcellular polyurethane foam, characterized in that the time (pot life) from the start to loss of fluidity is 2 to 5 minutes. The isocyanate group-containing compound is an isocyanate group-terminated urethane prepolymer,
The isocyanate compound constituting the isocyanate group-terminated urethane prepolymer is a mixture of an aromatic polyisocyanate compound (A1) and an aliphatic polyisocyanate compound (A2), and the ratio of A1 / A2 is 95/5 to 50/50. The method for producing a microcellular polyurethane foam according to claim 1, wherein the molar ratio is (molar ratio). 3. The method for producing a microcellular polyurethane foam according to claim 2, wherein the aliphatic polyisocyanate compound has an alicyclic structure. A polishing pad comprising a fine-cell polyurethane foam produced by the production method according to claim 1.