JP5037014B2 - Polishing pad manufacturing method and polishing pad - Google Patents

Description

  The present invention stabilizes flattening processing of optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing processing, The present invention also relates to a method of manufacturing 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.

  The technology for producing polyurethane resin foam includes a method of adding and dispersing a low-boiling organic solvent such as chlorofluorocarbon and methylene chloride to the foam-forming raw material composition, and foaming the polymer by vaporization by polymerization heat, foam formation A method is well known in which water is added to and dispersed in a raw material composition, and a polymer is foamed with a carbon dioxide gas generated by a reaction between an isocyanate group and water. The foam obtained by these methods has an average cell diameter of 100 μm as a lower limit, and it is difficult to obtain a foam having finer and uniform cells.

The following methods are known as a method for producing a polyurethane foam having fine bubbles.
(1) After solvent-soluble fine particles are dispersed in a polyurethane polymer and molded into a predetermined shape, the molded product is immersed in a solvent in which the fine particles are dissolved but the polyurethane polymer is not dissolved. A method of forming a resin, that is, a foam (Patent Document 1).
(2) A method of dispersing a fine hollow foam in a polyurethane resin-forming raw material composition (Patent Documents 2 and 3).

  However, according to the method of Patent Document 1, a large amount of solvent is required and a solvent containing the fine particle forming material needs to be processed, which is expensive in terms of cost. Moreover, the obtained foam is only open-celled and cannot be used for applications that require rigidity, which limits the applications. Moreover, the elution process and the process of drying a solvent are also required, and there is a problem that it takes a long time to produce a molded product having a large thickness.

  On the other hand, in the methods of Patent Documents 2 and 3, it is difficult to produce a uniform foam because the micro hollow foam tends to float in the polyurethane reaction stock solution due to the difference in density. The material is relatively expensive, and the material of the fine hollow foam remains in the foam, and there is a problem that the blade is damaged when the foam is cut. In addition, the hollow fine particles are likely to be scattered, which requires a large amount of cost for equipment for improving the working environment.

  By the way, the polyurethane resin foam is used as a polishing pad used for the production of silicon for manufacturing semiconductors and electronic substrates. With the increase in the density of circuits formed in the polishing pad, high-precision polishing is required. Depending on the type and size of the particles contained in the polishing slurry used for polishing, the polishing pad (polyurethane foam) ) Is also required in accordance with the hardness. For example, the ceria-based slurry has a larger particle size than the silica-based slurry, and when a ceria-based slurry is used as the polishing slurry, a polishing pad having a higher hardness than that of the silica-based slurry is required.

  As a method for solving each of the above problems, there is no need to use a chemically reactive foaming agent such as water, a vaporizable expansive foaming agent such as chlorofluorocarbon, a fine hollow foam, or a solvent-soluble substance, and uniform fine bubbles are used. However, a method for producing a polyurethane foam having a higher hardness than that of the same density, a so-called mechanical foaming method is disclosed (Patent Document 4). As the chain extender, 4,4'-methylenebis (o-chloroaniline) (MOCA) is preferably used from the viewpoints of reactivity and physical properties of the resulting polyurethane resin foam. However, when MOCA is used, there is a problem that the bubble diameter of the polyurethane resin foam becomes large or the bubble diameter tends to vary, which adversely affects the polishing characteristics.

JP-A-2-91279 Japanese National Patent Publication No. 8-500622 JP 2000-343412 A Japanese Patent No. 3490431

  An object of this invention is to provide the manufacturing method of the polishing pad which consists of a polyurethane resin foam which has a very uniform micro bubble, and the polishing pad obtained by this manufacturing method. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

The present invention provides a polishing pad production method comprising the step (1) of mixing a first component containing an isocyanate-terminated prepolymer and a second component containing a chain extender and producing a polyurethane resin foam by curing.
In the step (1), a silicon-based surfactant is added to the first component so as to be 0.05 to 10% by weight in the polyurethane resin foam, and the first component is further stirred with a non-reactive gas. Preparing a foam dispersion in which the non-reactive gas is dispersed as fine bubbles, and then mixing the second component in the foam dispersion and curing to produce a polyurethane resin foam, and the chain The extender is an aromatic polyamine having a melting point of 70 ° C. or less, and relates to a method for producing a polishing pad.

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

  By using an aromatic polyamine having a melting point of 70 ° C. or lower in place of the MOCA that has been suitably used in the past, the present inventor can obtain a polyurethane resin foam having a small bubble diameter variation and having fine bubbles. I found. The reason is considered as follows. MOCA has a melting point of 106 ° C., and is added in a molten state (about 120 ° C.) when mixed with the cell dispersion. The bubble dispersion is usually adjusted to about 60 to 80 ° C., and since the temperature difference from the molten MOCA is large, the bubbles in the bubble dispersion are locally broken by heat, broken, integrated, and expanded. . As a result, it is considered that the bubble diameter varies. By using an aromatic polyamine having a melting point of 70 ° C. or lower as the chain extender, the temperature difference from the bubble dispersion can be reduced, thereby suppressing variations in bubble diameter. The melting point of the aromatic polyamine is preferably 60 ° C. or less, particularly preferably 40 ° C. or less.

（ただし、ｍは２〜４の整数であり、ｎは１〜２０の整数である。） In the present invention, the aromatic polyamine is 3,5-bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) from the viewpoint of reactivity and physical properties of the resulting polyurethane resin foam. ) -2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 3,5-diethyl-2,6-toluenediamine, N, N′-di-sec-butyl-4,4 ′ -Diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, m-xylylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, p-xylylenediamine An at least one selected from the group consisting of an amine and a polyalkylene oxide-di-p-aminobenzoate represented by the following general formula (1): It is preferred.

(However, m is an integer of 2-4, and n is an integer of 1-20.)

  In the present invention, it is necessary to contain a silicon-based surfactant in the polyurethane resin foam in an amount of 0.05 to 10% by weight, preferably 0.5 to 5% by weight. When the content of the silicon-based surfactant is less than 0.05% by weight, it is not preferable because a foam with fine bubbles cannot be obtained. On the other hand, if it exceeds 10% by weight, a polyurethane resin foam with high hardness cannot be obtained due to the plasticizing effect of the surfactant, which is not preferable.

  In the present invention, the isocyanate-terminated prepolymer preferably contains a low molecular weight polyol component as a raw material component.

  Moreover, in this invention, it is preferable that the isocyanate component which is a raw material component of the said isocyanate terminal prepolymer is aromatic diisocyanate and alicyclic diisocyanate. The aromatic diisocyanate is preferably toluene diisocyanate, and the alicyclic diisocyanate is preferably dicyclohexylmethane diisocyanate. By using the diisocyanate, the reaction rate with the chain extender can be controlled within a suitable range, so that it is preferable not only from the viewpoint of work but also from the viewpoint of moldability of the polyurethane resin foam.

  Moreover, this invention relates to the polishing pad manufactured by the said method.

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

  In the method for producing a polishing pad of the present invention, a silicon-based surfactant is added to the first component containing an isocyanate-terminated prepolymer so as to be 0.05 to 10% by weight in the polyurethane resin foam. After stirring the component with a non-reactive gas to prepare a bubble dispersion in which the non-reactive gas is dispersed as fine bubbles, the bubble dispersion is mixed with a second component containing a chain extender and cured. The process (1) which produces a polyurethane resin foam is included. The polyurethane resin foam serves as a polishing layer of a polishing pad. The polishing pad of the present invention may be a polishing layer alone or a laminate of a polishing layer and another layer (for example, a cushion layer).

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

  As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. As the isocyanate component, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, Aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, etc. Aliphatic diisocyanates, 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophor Diisocyanate, alicyclic diisocyanates such as norbornane diisocyanate and the like. 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 component include those usually used in the technical field of polyurethane. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the obtained reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more.

  The number average molecular weight of these high molecular weight polyol components is not particularly limited, but is preferably about 500 to 5,000 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, the polyurethane resin obtained by using the polyurethane resin does not have sufficient elastic properties and tends to be a brittle polymer, the polishing pad made of this polyurethane resin becomes too hard, May cause scratches. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the life of the polishing pad. On the other hand, when the number average molecular weight exceeds 5000, a polishing pad made of a polyurethane resin obtained using the number average molecular weight becomes soft, and it is difficult to obtain a sufficiently satisfactory planarity, which is not preferable.

  In addition to the above-described high molecular weight polyol component, 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 (hydro Shimechiru) cyclohexanol, diethanolamine, N- methyldiethanolamine, and can be used in combination a low molecular weight polyol component such as triethanolamine. Moreover, low molecular weight polyamine components such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine can 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 the low molecular weight polyol, the low molecular weight polyamine or the like is not particularly limited, and is appropriately determined depending on the properties required for the polishing pad (polishing layer) to be produced, and is 20 to 70 mol% of the total polyol component. Is preferred.

Isocyanate-terminated prepolymer is used and the polyol component or the like and an isocyanate component, the equivalent ratio of isocyanate groups (NCO) and the active hydrogen ^{(H *) (NCO / H} *) is 1.2 to 5.0, preferably 1 It is produced by heating reaction in the range of 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.

  In the present invention, an aromatic polyamine having a melting point of 70 ° C. or lower is used as the chain extender. Examples of such aromatic polyamines include 3,5-bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, and 3,5-diethyl-2. , 4-toluenediamine, 3,5-diethyl-2,6-toluenediamine, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′- Diaminodiphenylmethane, m-xylylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, and polyalkylene oxide represented by the above general formula (1) -Di-p-aminobenzoate etc. are mentioned. In particular, it is preferable to use polytetramethylene oxide-di-p-aminobenzoate having a polymerization degree n of 2 to 5. These may be used alone or in combination of two or more.

  Moreover, you may use the said low molecular weight polyol and / or low molecular weight polyamine with the said chain extender as needed. However, when using these together, it is preferable to use the said chain extender 80 mol% or more, More preferably, it is 90 mol% or more. When the chain extender is less than 80 mol%, the bubble diameter tends to be large or the bubble diameter tends to vary, and the planarization characteristics of the polishing pad tend to deteriorate.

  The ratio of the prepolymer to the chain extender can be variously changed according to the molecular weight of each and the desired physical properties of the polishing pad produced therefrom. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the prepolymer relative to the number of functional groups of the chain extender is preferably in the range of 0.95 to 1.20, more preferably 0.99 to 1.15. It is.

  The polyurethane resin foam of the present invention is produced by a melting method in consideration of the need to take pores (bubbles) into the polyurethane resin, further considering the cost, working environment, and the like. Then, a polyurethane resin foam is produced by a mechanical foaming method using a silicon surfactant which is a copolymer of polyalkylsiloxane and polyether. As such a silicon surfactant, SH-192 (manufactured by Toray Dow Corning Silicon) and the like are exemplified as a suitable compound.

  In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed. These may be added to either the first component or the second component, but are preferably added when mixing both components.

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 and stirred in the presence of a non-reactive gas to disperse the non-reactive gas as fine bubbles. To make a bubble 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 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 method for producing the polyurethane resin foam, a known amine reaction catalyst such as a tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  Production of the polyurethane resin 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.

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

  The average cell diameter of the polyurethane resin foam is preferably 70 μm or less, more preferably 30 to 60 μm. When the average bubble diameter exceeds 70 μm, the planarity (flatness) of the polished material after polishing tends to decrease.

  Further, the variation in the cell diameter of the polyurethane resin foam is preferably 8.5 or less, more preferably 8 or less, based on the standard deviation. When the standard deviation exceeds 8.5, the flattening characteristics are deteriorated and the polishing rate becomes unstable.

  The specific gravity of the polyurethane resin foam is preferably 0.5 to 1.0. When the specific gravity is less than 0.5, the surface strength of the polishing layer decreases, and the planarity of the material to be polished tends to decrease. On the other hand, when the ratio is larger than 1.0, 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 hardness of the polyurethane resin foam is preferably 45 to 65 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 45 degrees, the planarity of the material to be polished is lowered. When the Asker D hardness is more than 65 degrees, the planarity is good but the uniformity of the material to be polished is lowered. There is a tendency.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the material 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, the polishing layer is also polished. In order to prevent destruction of the material to be polished due to adsorption with the material, it is preferable that the polished 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 thickness variation of the polishing layer is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large waviness, and there are portions where the contact state with the material to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with a dresser in which diamond abrasive grains are electrodeposited and fused in the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.

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

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

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

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

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

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

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

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

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

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

[Measurement and evaluation methods]
(Measurement of number average molecular weight)
The number average molecular weight 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 and standard deviation)
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 and standard deviation were calculated from the measured values.

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

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

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As 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 scraping. In the pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and the pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the level difference between the above two patterns is 2000 mm or less. The amount of scraping of the 270 μm space was measured. When the numerical value of the local step is low, it indicates that the flattening speed in a certain time is high with respect to the unevenness of the oxide film caused by the pattern dependence on the wafer. Further, when the amount of scraping of the space is small, the amount of shaving of the portion that is not desired to be shaved is small and the flatness is high.

(Dressing speed measurement)
The surface of the prepared polishing pad was uniformly dressed while being rotated using a diamond dresser (Asahi Diamond Co., Ltd., M type # 100, 20 cmφ circle). The dresser load at this time was 450 g / cm ² , the polishing platen rotation speed was 30 rpm, the dresser rotation speed was 15 rpm, and the dressing time was 100 min. Then, the dressing speed was calculated from the thickness of the polishing pad before and after the dressing.

Example 1
In a container, 1229 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetramethylene ether glycol 1901 having a number average molecular weight of 1018 Part by weight and 198 parts by weight of diethylene glycol were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer.
100 parts by weight of the prepolymer and 3 parts by weight of a silicon-based surfactant (SH-192, manufactured by Toray Dow Silicone Co., Ltd.) were added to the polymerization vessel, mixed, adjusted to 80 ° 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. Etacure 300 (Albemarle, 3,5-bis (methylthio) -2,6-toluenediamine and 3,5-bis (methylthio) -2,4-toluenediamine mixed in advance with a temperature adjusted to 70 ° C. ) 21 parts by weight were added. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block.
The polyurethane resin foam block 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 an abrasive sheet. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was applied to the surface of the polishing sheet opposite to the grooved surface using a laminator. Further, the surface of the corona-treated cushion sheet (manufactured by Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
In Example 1, instead of Etacure 300 whose temperature was adjusted to 70 ° C. in advance, Etacure 100 whose temperature was adjusted to 70 ° C. in advance (manufactured by Albemarle, 3,5-diethyl-2,6-toluenediamine and 3,5-diethyl) (Mixture with -2,4-toluenediamine) A polishing pad was prepared in the same manner as in Example 1 except that 18 parts by weight was used.

Example 3
In Example 1, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane (manufactured by Dorf Chemical Chemicals, Inc., temperature-adjusted in advance to 70 ° C., instead of etacure 300 in which the temperature was adjusted in advance to 70 ° C. Unilink 4200) A polishing pad was prepared in the same manner as in Example 1 except that 31 parts by weight were used.

Example 4
In Example 1, 3,3′-diethyl-4,4′-diaminodiphenylmethane (manufactured by Nippon Kayaku Co., Ltd., Kayahard A-A), which was previously temperature-adjusted to 70 ° C., instead of Etacure 300 whose temperature was adjusted to 70 ° C. in advance. ) A polishing pad was prepared in the same manner as in Example 1 except that 25 parts by weight were used.

Example 5
In Example 1, N, N′-di-sec-butyl-p-phenylenediamine (manufactured by Sumitomo Chemical Co., Ltd., Sumilyzer BPA) 22 that was previously temperature-adjusted to 70 ° C. instead of Etacure 300 that was previously adjusted to 70 ° C. A polishing pad was prepared in the same manner as in Example 1 except that parts by weight were used.

Example 6
In Example 1, polytetramethylene oxide-di-p-aminobenzoate whose temperature was adjusted to 70 ° C. in advance (Elastomer 250P, average polymerization degree, manufactured by Ihara Chemical Industry Co., Ltd.) instead of Etacure 300 whose temperature was adjusted to 70 ° C. in advance. n = 3.2) A polishing pad was prepared in the same manner as in Example 1 except that 48 parts by weight were used.

Comparative Example 1
In Example 1, the same procedure as in Example 1 was used except that 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. was used instead of Etacure 300 whose temperature was adjusted to 70 ° C. in advance. A polishing pad was prepared by the method described above.

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

  From the results in Table 1, a polishing pad having extremely uniform fine bubbles can be obtained by using an aromatic polyamine having a melting point of 70 ° C. or less as a chain extender. And it turns out that this polishing pad is excellent in the planarization characteristic than the conventional polishing pad.

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

Explanation of symbols

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

Claims (7)

In the method for producing a polishing pad comprising the step (1) 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 (1), a silicon-based surfactant is added to the first component so as to be 0.05 to 10% by weight in the polyurethane resin foam, and the first component is further stirred with a non-reactive gas. Preparing a foam dispersion in which the non-reactive gas is dispersed as fine bubbles, and then mixing and curing the second component in the foam dispersion to produce a polyurethane resin foam having an average cell diameter of 70 μm or less. And the chain extender is an aromatic polyamine having a melting point of 70 ° C. or less. The aromatic polyamine is 3,5-bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 3,5-diethyl-2,6-toluenediamine, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, m-xyl Range amine, N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, and polyalkylene oxide-di-p-amino represented by the following general formula (1) The method for producing a polishing pad according to claim 1, wherein the polishing pad is at least one selected from the group consisting of benzoate.

(However, m is an integer of 2-4, and n is an integer of 1-20.) The method for producing a polishing pad according to claim 1, wherein the isocyanate-terminated prepolymer contains a low molecular weight polyol component as a raw material component. The method for producing a polishing pad according to any one of claims 1 to 3, wherein the isocyanate component which is a raw material component of the isocyanate-terminated prepolymer is an aromatic diisocyanate and an alicyclic diisocyanate. The method for producing a polishing pad according to claim 4, wherein the aromatic diisocyanate is toluene diisocyanate, and the alicyclic diisocyanate is dicyclohexylmethane diisocyanate. A polishing pad manufactured by the method according to claim 1. 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 6.

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