JP4930837B2 - Polishing pad - Google Patents

Description

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

  A typical material that requires high surface flatness is a single crystal silicon disk called a silicon wafer for manufacturing a semiconductor integrated circuit (IC, LSI). Silicon wafers have a highly accurate surface in each process of stacking and forming oxide films and metal films in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC and LSI 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.

  Examples of the metal film for wiring include Al, W, and Cu. Among these, Cu has advantages such as low resistance and high electromigration resistance, and is expected as a next-generation wiring material. When polishing the Cu film, the polishing operation is performed with low pressure and high speed rotation.

  In such a polishing operation at high speed, the polishing characteristics of the polishing pad are required to have excellent in-plane uniformity and excellent polishing rate stability. As a polishing pad for polishing a metal film, for example, the following has been proposed.

  A base, an elastic material, a hydraulic pressure module when the compression force of 4 psi to 20 psi is applied is 250 psi for a compression force of 1 psi, an elastic material, and the first layer A flattening pad comprising a first layer larger than the hydraulic module is disclosed (Patent Document 1).

  A base, a first layer made of an elastic material having a strain constant greater than 6 microns / psi when subjected to a compression pressure greater than about 4 psi, and about 3 microns / psi when subjected to the predetermined compression pressure A polishing pad comprising a second layer made of an elastic flexible material having a smaller strain constant is disclosed (Patent Document 2).

  The polishing pad has excellent planarization characteristics, but has a problem in terms of stability of polishing rate.

JP-A-6-21028 Japanese Patent No. 3444272

  An object of the present invention is to provide a polishing pad having excellent in-plane uniformity and excellent polishing rate stability in polishing operation at high speed rotation. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

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

  That is, the present invention provides a polishing pad having a polishing layer and a cushion layer, wherein the cushion layer has a dynamic storage elastic modulus ratio (R = E′100 / E′1) at 100 Hz and 1 Hz of 1.3 or less. It is related with the polishing pad characterized by these.

  Since the cushion layer is usually softer than the polishing layer, the strain of the cushion layer during polishing tends to be larger than that of the polishing layer. When the polishing operation is performed at a low pressure and at a high speed, a vibration in a wide frequency range is applied to the polishing pad as compared with a normal polishing operation, and the influence of the vibration is considered to be greater in the cushion layer than in the polishing layer. By using a cushion layer having a small change in the dynamic storage elastic modulus in a wide frequency range (that is, a change in the dynamic hardness is small), the inventors have excellent in-plane uniformity and a polishing rate. It has been found that a polishing pad having excellent stability can be obtained.

  The reason for adopting the dynamic storage elastic modulus at 100 Hz and 1 Hz of the cushion layer is that polishing of a metal film such as Cu is usually performed with a polishing load of 10 to 40 kPa, a polishing platen rotation speed of 50 to 150 rpm, and a wafer rotation speed of 50 to 50. This is because it is presumed that the frequency range of the main vibration generated at this time is in the range of 1 to 100 Hz, and a smaller frequency dependency is required in a wider range.

  The cushion layer includes 1) a polyurethane foam having an open cell structure, 2) a heat-molded polyurethane foam having an open cell structure, or 3) impregnating a polyurethane foam having an open cell structure with a curable resin, It is preferable to be one obtained by heat compression molding and further curing the curable resin. By using the material as the cushion layer, the ratio of the dynamic storage elastic modulus can be easily adjusted to 1.3 or less.

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

  The polishing layer of the present invention is not particularly limited as long as it is a foam having fine bubbles. For example, polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, halogen resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin resin (polyethylene, polypropylene, etc.), epoxy resin 1 type, or 2 or more types of mixtures, such as a photosensitive resin, is mentioned. Polyurethane resin is a particularly preferable material for forming the polishing layer because it has excellent wear resistance and a polymer having desired physical properties can be easily obtained by variously changing the raw material composition. Hereinafter, the polyurethane resin will be described on behalf of the foam.

  The polyurethane resin comprises an isocyanate component, a polyol component (high molecular weight polyol, low molecular weight polyol, etc.), and a chain extender.

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

  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.).

  Of the above isocyanate components, it is preferable to use an aromatic diisocyanate and an alicyclic diisocyanate in combination, and it is particularly preferable to use toluene diisocyanate and dicyclohexylmethane diisocyanate in combination.

  Examples of the high molecular weight polyol include polyether polyols typified by polytetramethylene ether glycol, polyester polyols typified by polybutylene adipate, polycaprolactone polyol, and a reaction product of a polyester glycol such as polycaprolactone and alkylene carbonate. Polyester polycarbonate polyol, polyester carbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the resulting reaction mixture with organic dicarboxylic acid, and polycarbonate polyol obtained by transesterification reaction between polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 2000 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, a polyurethane resin using the number average molecular weight does not have sufficient elastic properties and becomes a brittle polymer. Therefore, the polishing layer produced from this polyurethane resin becomes too hard and causes a scratch on the wafer surface. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the pad life. On the other hand, when the number average molecular weight exceeds 2000, a polyurethane resin using the number average molecular weight becomes too soft, and a polishing layer produced from this polyurethane resin tends to have poor planarization characteristics.

  Along with high molecular weight polyol, 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, tri Methylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclo Hexanol, diethanolamine, N- methyldiethanolamine, and low molecular weight polyols such as triethanolamine may be used in combination. 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.

  When a polyurethane foam is produced by a prepolymer method, a chain extender is used for curing the 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, polytetramethylene oxide-di-p-aminobenzoate, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4, 4'-diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetra Sopropyldiphenylmethane, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane, 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 And polyamines exemplified by p-xylylenediamine and the like, or the low molecular weight polyols and low molecular weight polyamines mentioned above. These may be used alone or in combination of two or more.

  The ratio of the isocyanate component, the polyol component, and the chain extender in the present invention can be variously changed depending on the molecular weight of each, the desired physical properties of the polishing pad, and the like. In order to obtain a polishing layer having desired polishing characteristics, the number of isocyanate groups of the isocyanate component relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the polyol component and the chain extender is 0.80 to 1.20. Is more preferable, and 0.99 to 1.15 is more preferable. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity and hardness cannot be obtained, and the polishing characteristics tend to be deteriorated.

  The polyurethane 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, working environment and the like.

  Polyurethane foam can be produced by either the prepolymer method or the one-shot method, but an isocyanate-terminated prepolymer is synthesized in advance from an isocyanate component and a polyol component, and this is reacted with a chain extender. Is preferred because the resulting polyurethane resin has excellent physical properties.

  In the production of the polyurethane foam, a first component containing an isocyanate group-containing compound and a second component containing an active hydrogen group-containing compound are mixed and cured. 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 isocyanate component becomes an isocyanate group-containing compound, and the chain extender and the polyol component become active hydrogen group-containing compounds.

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

  In particular, a mechanical foaming method using a silicon surfactant which is a copolymer of polyalkylsiloxane and polyether is preferable. Examples of suitable silicon-based surfactants include SH-192 and L-5340 (manufactured by Toray Dow Corning Silicone), B8465 (manufactured by Goldschmidt), and the like.

  In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed.

An example of a method for producing a micro-bubble type polyurethane foam will be described below. The manufacturing method of this polyurethane 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 production method of polyurethane foam, heating and post-curing the foam that has reacted until the foaming reaction liquid is poured into the mold and no longer flows is effective in improving the physical properties of the foam and is extremely suitable. It is. 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 foam, a known catalyst that promotes polyurethane reaction such as tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  Polyurethane foam can be produced by weighing each component, putting it in a container and stirring it, or by continuously supplying each component and non-reactive gas to the stirrer and stirring to disperse the bubbles. It may be a continuous production method in which a liquid is fed to produce a molded product.

  Also, put the prepolymer that is the raw material of the polyurethane foam into the reaction vessel, and then add the chain extender, and after stirring, cast it into a casting mold of a predetermined size to make the block into a bowl shape or a band saw shape In the method of slicing using the above slicer, or in the casting step described above, a thin sheet may be formed. Alternatively, a raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane foam.

  The average cell diameter of the polyurethane foam is preferably 30 to 80 μm, more preferably 30 to 60 μm. When deviating from this range, the polishing rate tends to decrease, or the planarity of the polished material (wafer) after polishing tends to decrease.

  The specific gravity of the polyurethane 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 material 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 foam preferably has a hardness of 40 to 65 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 40 degrees, the planarity of the material to be polished is lowered. When the Asker D hardness is larger 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 layer that comes into contact with the material to be polished preferably has an uneven structure for holding and renewing the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and updating the slurry. By forming a concavo-convex structure on the polishing surface, the slurry can be held and updated more efficiently. It can be performed well, and destruction of the material to be polished due to adsorption with the material to be polished can be prevented. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

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

  The thickness of the polishing layer is not particularly limited, but is usually about 0.8 to 4 mm, and preferably 1.0 to 2.5 mm. As a method for producing the polishing layer having the above thickness, a method in which the block of the fine foam is made to have a predetermined thickness using a band saw type or canna type slicer, a resin is poured into a mold having a cavity having a predetermined thickness, and curing is performed. And a method using a coating technique or a sheet forming technique.

  In the present invention, a cushion layer having a dynamic storage elastic modulus ratio (R = E′100 / E′1) at 100 Hz and 1 Hz of 1.3 or less is used. The ratio of the dynamic storage elastic modulus is preferably 1.25 or less, more preferably 1.2 or less.

  Examples of the cushion layer having the above characteristics include polyurethane foam having an open cell structure.

  Examples of the material for forming the polyurethane foam include the same materials as those for forming the polishing layer.

As a method for forming polyurethane into foam, for example, a) A low molecular gas such as CO ₂ is dissolved in a resin at a predetermined temperature and pressure, and then the dissolved gas is supersaturated by a rapid pressure reduction / temperature increase operation. A physical foaming method that generates bubbles in the resin, b) a method in which a low-boiling organic compound is mixed with a polymerizable resin raw material and cured simultaneously with foaming, and c) a chemical foaming agent (reactant) in the resin raw material. After kneading, a chemical foaming method in which a gas such as CO ₂ and N ₂ is generated by causing a decomposition reaction under a predetermined temperature condition to generate bubbles in the resin. D) The molten resin is mechanically stirred to contain bubbles. And a mechanical foaming method in which the bubbles are forcibly confined by cooling and solidifying, or mechanically stirring the resin raw material to solidify by a polymerization reaction.

  The polyurethane foam can be produced by, for example, an extrusion molding method, an injection molding method, a molding method, or the like. Examples of a method for forming a polyurethane foam into an open cell structure include a method of crushing cells after forming the foam, and a method of selecting and adjusting the type and blending amount of the surfactant and catalyst. The open cell ratio of the polyurethane foam is preferably 90% or more, more preferably 95% or more.

  In order to make the polyurethane foam into an open-cell structure, a polymer polyol may be used, and examples thereof include a polymer polyol in which polymer particles made of acrylonitrile and / or a styrene-acrylonitrile copolymer are dispersed.

  In order to make the polyurethane foam into an open cell structure, a low molecular weight polyol having a hydroxyl value of 400 to 1830 mgKOH / g and / or a low molecular weight polyamine having an amine value of 400 to 1870 mgKOH / g may be used. The hydroxyl value is preferably 700 to 1250 mgKOH / g, and the amine value is preferably 400 to 950 mgKOH / g. In particular, it is preferable to use diethylene glycol, triethylene glycol, or 1,4-butanediol. The low molecular weight polyol and the like are preferably contained in the polyol component in a total amount of 2 to 15% by weight, more preferably 5 to 10% by weight. By using a specific amount of the low molecular weight polyol or the like, the bubble film is easily broken and an open cell structure is easily formed.

  The foaming ratio of the polyurethane foam is preferably 1.2 to 4 times, more preferably 1.5 to 2.5 times. The foaming ratio of the polyurethane foam can be adjusted by, for example, the amount of low molecular gas, low boiling point organic compound, or foaming agent added to the resin, and in the case of the mechanical foaming method, the rotational speed of the stirring blade or the stirring time. it can.

  The Asker C hardness of the polyurethane foam is preferably 40 to 80 degrees, more preferably 50 to 70 degrees. The Asker C hardness of the polyurethane foam can be set to a target value by appropriately adjusting the molecular weight, crosslink density, expansion ratio, etc. of the polymer.

  Moreover, you may use the heat compression polyurethane foam which heat-press-molded the polyurethane foam which has the said open cell structure as a cushion layer. By performing the heat compression molding, the ratio of the dynamic storage elastic modulus can be further reduced. The temperature at the time of hot compression is preferably 100 to 250 ° C, more preferably 170 to 210 ° C. Moreover, it is preferable that the time at the time of heat compression is 1 to 5 minutes, More preferably, it is 2 to 3 minutes. Moreover, it is preferable that the compression rate at the time of heat compression is 30 to 80%, More preferably, it is 40 to 60%. The Asker C hardness of the heat-compressed polyurethane foam is preferably 40 to 80 degrees, more preferably 50 to 70 degrees.

  Further, as the cushion layer, a resin-impregnated heat-compressed polyurethane foam obtained by impregnating a polyurethane foam having the open cell structure with a curable resin, heat compression molding, and further curing the curable resin may be used. The ratio of the dynamic storage elastic modulus can be further reduced by impregnating and curing the curable resin and hot compression molding. Examples of the curable resin to be impregnated include moisture curable polyurethanes, moisture curable silicone resins, moisture curable silicone rubbers, moisture curable acrylic resins, and moisture curable epoxy resins; and thermosetting polyurethanes. , Thermosetting resins such as thermosetting phenolic resins, thermosetting epoxy resins, thermosetting acrylic resins, thermosetting silicone resins, and thermosetting silicone rubbers; UV curable polyester acrylate, UV curable urethane acrylate, Examples include ultraviolet curable resins such as ultraviolet curable epoxy acrylate and ultraviolet curable silicone rubber. Among these, thermosetting resins and moisture curable resins are preferably used because they can be cured simultaneously with the heat compression molding. The curable resin is preferably impregnated in an amount of 3 to 50 parts by weight, more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the polyurethane foam. Various conditions at the time of thermal compression are the same as described above. The Asker C hardness of the resin-impregnated hot-pressed polyurethane foam is preferably 40 to 80 degrees, more preferably 50 to 70 degrees.

  The thickness of the cushion layer is not particularly limited, but is usually about 0.5 to 5 mm, preferably 0.5 to 2 mm.

  The polishing pad of the present invention is produced by, for example, a method in which the polishing layer and the cushion layer are bonded together with a double-sided tape, a method in which the forming material for the polishing layer is applied on the cushion layer and cured to be integrally formed.

  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. It is also possible to use a tape that does not have a 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 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 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, one having an adhesive layer on both sides of a substrate can be used as described above. In consideration of peeling from the platen after use of the polishing pad, it is preferable to use a film for the substrate.

  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.

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

[Measurement and evaluation methods]
(Average bubble diameter)
The produced polyurethane foam was cut as thin as possible to a thickness of 1 mm or less in parallel with a microtome cutter, and used as a sample for measuring the average cell diameter. The sample was fixed on a slide glass and observed at 100 times using SEM (S-3500N, Hitachi Science Systems, Ltd.). Using the image analysis software (WinRoof, Mitani Shoji Co., Ltd.) for the obtained image, the total bubble diameter in an arbitrary range was measured, and the average bubble diameter was calculated.

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

(D hardness)
This was performed in accordance with JIS K6253-1997. A sample obtained by cutting the produced polyurethane foam 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 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 after 60 seconds was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

(C hardness)
This was performed according to JIS K-7312. Samples obtained by cutting out the cushion layers of Examples and Comparative Examples into a size of 5 cm × 5 cm (thickness: arbitrary) were used as samples, and left 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 have a thickness of 10 mm or more. Using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker C-type hardness meter, pressure surface height: 3 mm), the hardness 30 seconds after contacting the pressure surface was measured.

(Storage modulus)
This was performed in accordance with JIS K7198-1991. The cushion layer punched out with a φ7 mm punch was used as a sample for dynamic viscoelasticity measurement, and the sample was allowed to stand for 24 hours or more under environmental conditions of a temperature of 23 ° C. and a humidity of 50%. For measurement, a dynamic viscoelastic spectrometer (manufactured by UBM, Rheogel E-4000) was used, and storage elastic moduli E′1 and E′100 at 1 Hz and 100 Hz were measured. The measurement conditions at that time are shown below.
<Measurement conditions>
Jig: Compression jig φ15mm
Shape: φ7mm
Static load: 300 g / cm ²
Frequency: 1Hz, 100Hz
Compression strain: 1μm
Measurement temperature: 23 ± 2 ° C

(Measurement of open cell ratio)
The open cell ratio was measured according to the ASTM-2856-94-C method. However, a sample obtained by stacking 10 cushion layers punched out in a circle was used as a measurement sample. As a measuring instrument, an air comparison type hydrometer 930 type (manufactured by Beckman Co., Ltd.) was used. The open cell ratio was calculated by the following formula.
Open cell ratio (%) = [(V−V1) / V] × 100
V: Apparent volume calculated from sample size (cm ³ )
V1: Sample volume (cm ³ ) measured using an air-comparing hydrometer

(Evaluation of polishing rate stability)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, the polishing rate stability of the manufactured polishing pad was evaluated. The polishing rate stability was evaluated by the rate of change in polishing rate. The polishing rate change rate was calculated by the following method. First, the prepared polishing pad was initially dressed for 30 minutes under the following conditions.
<Initial dress conditions>
Dresser: Asahi Diamond M type No100
Pressure: 10 g / cm ²
Rotation speed: Dresser 10rpm, Polishing surface plate 20rpm
Using the initially dressed polishing pad, the dummy wafer was polished under the following polishing conditions, and then the polishing pad was Ex-situ dressed under the following conditions. The above operation was repeated for four dummy wafers to adjust the condition of the polishing pad.
<Polishing conditions>
Slurry: Silica slurry (SS12, manufactured by Cabot Corporation)
Slurry amount: 150 ml / min
Polishing pressure: 450 g / cm ² (low speed condition), 150 g / cm ² (high speed condition)
Polishing platen rotation speed: 35 rpm (low speed condition), 120 rpm (high speed condition)
Wafer rotation speed: 35 rpm (low speed condition), 120 rpm (high speed condition)
Polishing time: 1 minute <Ex-situ dress conditions>
Dresser: Asahi Diamond M type No100
Pressure: 10 g / cm ²
Rotation speed: Dresser 10rpm, Polishing surface plate 20rpm
Dressing time: 20 seconds Thereafter, using the polishing pad, a sample obtained by depositing 1 μm of a thermal oxide film on an 8-inch silicon wafer was polished under the polishing conditions, and an initial polishing rate (Å / min) was measured. Thereafter, the polishing pad was dressed for 24 hours under the initial dressing conditions, and the condition of the polishing pad was adjusted by the same method as described above. Thereafter, using the polishing pad, a sample obtained by depositing 1 μm of a thermal oxide film on an 8-inch silicon wafer was polished under the above polishing conditions, and the polishing rate (速度 / min) after 24 hours was measured. The rate of change in the polishing rate was calculated from the following formula from the initial polishing rate and the polishing rate after 24 hours. The rate of change in the polishing rate is preferably 10% or less, more preferably 9% or less in the case of low-speed polishing conditions.
Polishing rate change rate (%) = [(initial polishing rate−polishing rate after 24 hours) / initial polishing rate] × 100

(Evaluation of in-plane uniformity)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As polishing conditions, silica slurry (SS12, manufactured by Cabot Corporation) was added as a slurry at a flow rate of 150 ml / min. Polishing load is 450 g / cm ² (low speed condition), 150 g / cm ² (high speed condition), polishing platen rotation speed is 35 rpm (low speed condition), 120 rpm (high speed condition), wafer rotation speed is 35 rpm (low speed condition), 120 rpm (High speed conditions).
In-plane uniformity is obtained by polishing for 1 minute under the above polishing conditions using a sample in which a thermal oxide film is deposited on an 8-inch silicon wafer, and before and after polishing at 25 specific positions on the wafer as shown in FIG. The maximum polishing rate and the minimum polishing rate were obtained from the film thickness measurement values, and the values were calculated by substituting them into the following formula. Note that the smaller the in-plane uniformity value, the higher the uniformity of the wafer surface.
In-plane uniformity (%) = {(maximum polishing rate−minimum polishing rate) / (maximum polishing rate + minimum polishing rate)} × 100

Example 1
(Preparation of polishing layer)
In the reaction vessel, 100 parts by weight of a polyether-based prepolymer (manufactured by Uniroyal, Adiprene L-325) and 3 parts by weight of a silicon-based surfactant (manufactured by Goldschmidt, B8465) are mixed, and the temperature is 80 ° C. Adjusted. Using a stirring blade, the mixture was vigorously stirred for about 4 minutes so that bubbles were taken into the reaction system at 900 rpm. Thereto was added 27 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Iharacamine MT, manufactured by Ihara Chemical Co.) previously melted at 120 ° C. Thereafter, stirring was continued for about 1 minute, and the reaction solution was poured into a pan-shaped open mold. When the reaction solution lost its fluidity, it was placed in an oven and post-cured at 110 ° C. for 6 hours to obtain a polyurethane foam block. This polyurethane foam block was sliced using a band saw type slicer (manufactured by Fecken) to obtain a polyurethane foam sheet. Next, this sheet was subjected to surface buffing to a predetermined thickness using a buffing machine (Amitech Co., Ltd.) to obtain a sheet with adjusted thickness accuracy (sheet thickness: 1.27 mm). The buffed sheet was punched to a diameter of 61 cm, and a perforation process of φ1.6 mm was performed on the surface to prepare a polishing layer. The produced polishing layer had an average bubble diameter of 45 μm, a specific gravity of 0.86, and Asker D hardness of 53 degrees. Thereafter, a double-sided tape (Sekisui Chemical Co., Ltd., double tack tape) was bonded to the polishing layer using a laminator.

(Production of cushion layer)
In a reaction vessel, 90 parts by weight of polypropylene glycol (Mitsui Takeda Chemical Co., EP330N), 10 parts by weight of diethylene glycol, 5 parts by weight of a silicon-based surfactant (SH-192, manufactured by Toray Dow Corning Silicone Co., Ltd.), catalyst (Kao Corporation) Manufactured, Kao-No25) 0.5 part by weight was mixed, and the temperature was adjusted to 40 ° C. Using a stirring blade, the mixture was vigorously stirred for about 5 minutes so that air bubbles were taken into the reaction system at a rotation speed of 900 rpm. And 40 parts by weight of Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.) was added. Thereafter, stirring was continued for about 1 minute, and the reaction solution was poured into an open mold of φ800 mm. When the fluidity of the reaction solution ceased, it was placed in an oven and post-cured at 80 ° C. for 8 hours to obtain a polyurethane foam. The obtained polyurethane foam was sliced to about 1.5 mm using a slicing machine (Amitech, VGW-125), and subsequently buffed using a buffing machine (Amitech) to cushion the cushion layer (thickness). : 1.25 mm).

(Preparation of polishing pad)
The cushion layer was bonded to a double-sided tape provided on one side of the polishing layer. And the said double-sided tape was bonded together using the laminating machine on the other surface of the cushion layer, and the protrusion part of the cushion layer was cut off along the outer periphery of the polishing layer, and the polishing pad was produced.

Example 2
In producing the cushion layer, the obtained polyurethane foam was sliced to about 2.5 mm using a slicing machine, and subsequently compressed by a hot press machine at 200 ° C. for 2 minutes. (Thickness: 1.25 mm) was produced. A polishing pad was produced in the same manner as in Example 1 except that the cushion layer was used.

Example 3
In making the cushion layer, the obtained polyurethane foam was sliced to about 2.6 mm using a slicing machine, and the foam was impregnated with moisture-curing urethane adhesive (Nippon Polyurethane Co., Ltd., Wood Cure 220). A cushion layer (thickness: 1.25 mm) was produced in the same manner as in Example 1 except that the impregnation resin was cured for 2 minutes with a 200 ° C. hot press. The weight of the impregnating resin was 10 parts by weight with respect to 100 parts by weight of the polyurethane foam. A polishing pad was produced in the same manner as in Example 1 except that the cushion layer was used.

Comparative Example 1
A polishing pad was produced in the same manner as in Example 1 except that suba400 (manufactured by Haas Nitta) having a thickness of 1.27 mm was used as the cushion layer.

Comparative Example 2
A polishing pad was produced in the same manner as in Example 1 except that PORON HH-48C (Rogers Inoac Corp., closed cell type polyurethane foam) having a thickness of 1.0 mm was used as the cushion layer.

Comparative Example 3
A polishing pad was produced in the same manner as in Example 1 except that suba800 (manufactured by Haas Nitta) having a thickness of 1.27 mm was used as the cushion layer.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic showing 25 film thickness measurement positions on wafer

Explanation of symbols

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

Claims (5)

In the polishing pad having a polishing layer and a cushion layer, the cushion layer is characterized in that a ratio of dynamic storage elastic modulus at 100 Hz and 1 Hz (R = E′100 / E′1) is 1.3 or less. Polishing pad to do. The polishing pad according to claim 1, wherein the cushion layer is a polyurethane foam having an open cell structure. The polishing pad according to claim 1, wherein the cushion layer is obtained by heat compression molding a polyurethane foam having an open cell structure. The polishing pad according to claim 1, wherein the cushion layer is obtained by impregnating a polyurethane foam having an open cell structure with a curable resin, heat compression molding, and further curing the curable resin. 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.

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