JP5288715B2 - 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 laminated polishing pad that can be performed with high polishing efficiency and a method for manufacturing the same. The laminated 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. Preferably used.

  When manufacturing a semiconductor device, a step of forming a conductive layer on the wafer surface and forming a wiring layer by photolithography, etching, or the like, or a step of forming an interlayer insulating film on the wiring layer These steps cause irregularities made of a conductor such as metal or an insulator 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 irregularities on the wafer surface, chemical mechanical polishing (hereinafter referred to as CMP) is generally employed. CMP is a technique for polishing using a slurry in which abrasive grains are dispersed in a state where a surface to be polished of a wafer is pressed against a polishing surface of a polishing pad. As shown in FIG. 1, for example, a polishing apparatus generally used in CMP includes a polishing surface plate 2 that supports a polishing pad 1 and a support base (polishing head) 5 that supports a material to be polished (semiconductor wafer) 4. And a backing material for uniformly pressing the wafer, and an abrasive supply mechanism. 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 material to be polished 4 supported by each of the polishing surface plate 2 and the support base 5 are opposed to each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the workpiece 4 against the polishing pad 1 is provided on the support base 5 side.

  Conventionally, as a polishing pad used for high-precision polishing, a polyurethane foam sheet is generally used. However, although the polyurethane foam sheet is excellent in local flattening ability, it is difficult to apply a uniform pressure to the entire wafer surface because of insufficient cushioning properties. For this reason, usually, a soft cushion layer is separately provided on the back surface of the polyurethane foam sheet, and is used for polishing as a laminated polishing pad. For example, the following polishing pads have been developed.

  A semiconductor wafer polishing pad has been developed in which a polishing layer, a second layer having a higher elastic modulus than the polishing layer, and a third layer having a lower elastic modulus than the second layer are laminated in this order (Patent Document 1). ).

  In addition, a polishing pad having a laminated structure having an upper layer made of a hard material and a lower layer made of a soft material and having two or more waterproof material layers made of a plurality of different waterproof materials in a part of the upper layer has been developed. (Patent Document 2).

  In recent years, in order to manufacture as many semiconductor chips as possible from one wafer, a polishing pad that can be uniformly flattened to the wafer edge portion has been demanded. The polishing head is provided with a retainer ring to improve the uniformity of the wafer edge. However, the polishing pad is pressed and deformed by the retainer ring during polishing, and the deformation makes it difficult to polish the extreme part of the wafer. was there.

Japanese Patent No. 3788729 Japanese Patent No. 3152188

  An object of this invention is to provide the polishing pad which can grind | polish uniformly to a wafer extreme part. 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 shown below, and have completed the present invention.

  That is, the present invention provides a polishing pad in which a polishing layer and a cushion layer are laminated via a double-sided tape, and an intermediate layer made of the same material as the polishing layer and thicker than the polishing layer is interposed between the polishing layer and the cushion layer. The present invention relates to a polishing pad which is provided and is characterized in that a base material of a double-sided tape between a polishing layer and an intermediate layer is a resin film.

  The reason why the extreme wafer portion is difficult to be polished when a conventional polishing pad is used is considered as follows. Normally, the periphery of the wafer is held by a retainer ring so as not to be detached from the polishing head. At the time of polishing, the wafer is pressed against the surface of the polishing pad together with the retainer ring by a pressure mechanism. At this time, the polishing pad under the retainer ring is compressed and deformed by pressure, and accordingly, the polishing pad just inside the retainer ring is also dented. For this reason, it is considered that the pressure at which the extreme portion of the wafer comes into contact with the polishing pad is smaller than other portions of the wafer, and the extreme portion of the wafer is difficult to be polished. Moreover, it is considered that the conventional polishing pad absorbs the slurry and easily changes its elastic modulus over time and is easily compressed and deformed, so that the extreme portion of the wafer is less likely to be polished.

  The inventors prevent the slurry from entering the lower layer by laminating a double-sided tape whose base material is a resin film on the lower surface of the polishing layer, and the same as the polishing layer on the other side of the double-sided tape. It has been found that by providing an intermediate layer made of a material and thicker than the polishing layer, it is possible to suppress a change in elastic modulus over time without impairing the polishing characteristics of the polishing layer. The intermediate layer needs to be made of the same material as the polishing layer. This is because a laminated body composed of a polishing layer, a double-sided tape, and an intermediate layer is used as a pseudo-polishing layer so as not to impair the polishing characteristics of the entire laminated body. Moreover, since it can manufacture efficiently by using the same material, there exists a merit also in terms of cost. The intermediate layer must be thicker than the polishing layer. This is because when the intermediate layer is thinner than the polishing layer, the change in the elastic modulus of the entire laminate becomes large, and the wafer is easily compressed and deformed, making it difficult to polish the extreme portion of the wafer.

  In the present invention, the polishing layer has a thickness of 0.3 to 1.5 mm, the intermediate layer has a thickness of 0.5 to 2 mm, and the cushion layer has a thickness of 0.5 to 2 mm. preferable. By adjusting the thickness of each layer to the above range, not only the extreme difficulty of polishing the extreme wafer portion can be improved, but also polishing characteristics such as planarization characteristics can be improved.

  Moreover, it is preferable that the base material of the double-sided tape between a grinding | polishing layer and an intermediate | middle layer is a polyester film. The polyester film has an excellent property of preventing permeation of water, and can effectively prevent water from entering the intermediate layer.

  The shear stress of the double-sided tape between the polishing layer and the intermediate layer is preferably 700 kPa or more. By using a double-sided tape having a shear stress of 700 kPa or more, the durability of the double-sided tape against “shear” generated during polishing is improved, and it becomes difficult to peel between the polishing layer and the intermediate layer.

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

  The polishing layer and the intermediate layer in the present invention are not particularly limited as long as they are foams having fine bubbles. For example, halogen resins such as polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin resin (polyethylene, polypropylene, etc.) 1 type, or 2 or more types of mixtures, such as an epoxy resin and a photosensitive resin. Polyurethane resins are particularly preferred materials for forming the polishing layer and the intermediate layer because they are excellent in abrasion resistance and can easily obtain a polymer having desired physical properties by 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.).

  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 polycarbonate 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 pad manufactured from this polyurethane resin becomes too hard and causes scratches 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 pad produced from this polyurethane resin tends to have poor planarization characteristics.

  In addition to the above-described high molecular weight polyol as a polyol component, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4 -It is preferable to use a low molecular weight polyol such as cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene or the like. Low molecular weight polyamines such as ethylenediamine, tolylenediamine, diphenylmethanediamine and diethylenetriamine may be used.

  The ratio of the high molecular weight polyol, the low molecular weight polyol, and the low molecular weight polyamine in the polyol component is determined by the properties required for the polishing layer produced therefrom.

  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, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl Diphenylmethane, N, N′-di-sec-butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, m-xyl And polyamines exemplified by N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine, or the above-mentioned low molecular weight polyols and low molecular weight polyamines. be able to. These may be used alone or in combination of two or more.

  The 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 pad 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.

  As the isocyanate-terminated prepolymer, those having a molecular weight of about 800 to 5000 are preferable because of excellent processability and physical characteristics.

  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 silicone surfactant which is a copolymer of polyalkylsiloxane and polyether and does not have an active hydrogen group is preferable. Examples of the silicon surfactant include SH-192, SH-193 (manufactured by Toray Dow Corning Silicone), L5340 (manufactured by Nippon Unica), 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 fine closed-cell type polyurethane foam constituting the polishing layer and the intermediate layer will be described below. By using the closed cell type, absorption of the slurry can be suppressed. 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 closed cells 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 flatness 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 45 to 70 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 70 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 may have a concavo-convex 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 appropriately adjusted in consideration of the relationship with the intermediate layer and the cushion layer and polishing characteristics, but is preferably 0.3 to 1.5 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.

  The thickness of the intermediate layer is appropriately adjusted in consideration of the relationship with the polishing layer and the cushion layer and the polishing characteristics, but it needs to be at least thicker than the polishing layer, and is preferably 0.5 to 2 mm. The intermediate layer having the thickness can be produced in the same manner as the polishing layer.

  On the other hand, the cushion layer in the present invention supplements the characteristics of the polishing layer. The cushion layer is necessary in order to achieve both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a material to be polished having minute 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 layer. In the polishing pad of the present invention, the cushion layer is softer than the polishing layer.

  The material for forming the cushion layer is not particularly 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.

  The thickness of the cushion layer is appropriately adjusted in consideration of the relationship with the polishing layer and the intermediate layer and polishing characteristics, but is preferably 0.5 to 2 mm, and more preferably 0.8 to 1.5 mm.

  FIG. 2 is a schematic sectional view showing the structure of the polishing pad of the present invention. The polishing pad 1 of the present invention has a structure in which a polishing layer 8, an intermediate layer 9 and a cushion layer 10 are laminated via double-sided tapes 11 and 12.

  The double-sided tape 11 between the polishing layer and the intermediate layer is one in which an adhesive layer is provided on both sides of a substrate made of a resin film. Examples of the resin film include polyester films such as polyethylene terephthalate film and polyethylene naphthalate film; polyolefin films such as polyethylene film and polypropylene film; nylon films and the like.

  As a base material for the double-sided tape 11, a polyester film is preferably used. The polyester film has an excellent property of preventing permeation of water, and can effectively prevent water from entering the intermediate layer.

  The double-sided tape 12 between the intermediate layer and the cushion layer is not particularly limited, and examples thereof include those in which an adhesive layer is provided on both surfaces of a non-woven fabric or a substrate made of the resin film.

  The shear stress of the double-sided tapes 11 and 12 is preferably 700 kPa or more. By using a double-sided tape having a shear stress of 700 kPa or more, the durability of the double-sided tape against “slipping” generated during polishing is improved, and it becomes difficult to peel between the polishing layer and the intermediate layer and between the intermediate layer and the cushion layer. . As a method of adjusting the shear stress of the double-sided tape to 700 kPa or more, a method of increasing the crosslinking degree of the adhesive by mixing a polyfunctional monomer such as a trifunctional monomer, a substrate having a high shear stress (for example, PET, PEN) Etc.).

  When the substrate is a resin film, the thickness is about 5 to 250 μm, preferably 10 to 125 μm, considering the strength and shear stress.

  Examples of the composition of the adhesive include rubber and acrylic. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. It is also possible to optimize the adhesive strength of each layer by making the composition of each adhesive of the double-sided tape different.

  The thickness of the adhesive layer is preferably 10 to 200 [mu] m, more preferably 40 to 150 [mu] m, considering the adhesive force and shear stress.

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

  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 sides of a substrate can be used as described above.

  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 the polishing pad 1, a support table (polishing head) 5 that supports the semiconductor wafer 4, and the wafer. This is performed using a backing material for performing uniform pressurization and a polishing apparatus equipped with a polishing agent 3 supply mechanism. 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 adjusted as appropriate.

  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]
(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

(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 temperature 23 ° C ± 2 ° C and humidity 50% ± 5%. did. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(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 was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

(Shear stress)
The both ends (each 20 mm length) of the double-sided tape having a width of 20 mm were bonded to the polishing layer produced at a pressure of 78.5 kPa. Thereafter, the both ends were pulled at a pulling speed of 200 mm / min, and the shear stress (kPa) at this time was measured.

(In-plane uniformity)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as the polishing apparatus, the in-plane uniformity was evaluated (Max-Min method) 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. 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-plane uniformity was evaluated by polishing for 2 minutes under the above-described polishing conditions using a 1-μm thick thermal oxide film deposited on an 8-inch silicon wafer. As shown in FIG. The maximum polishing rate, the minimum polishing rate, and the average polishing rate were obtained from the measured film thickness values before and after the (interval), and the values were calculated by substituting these values into the following formula. In-plane uniformity of the 1000th wafer is shown in Table 1. Note that the smaller the in-plane uniformity value, the higher the uniformity of the wafer surface.
Max-Min method In-plane uniformity (%) = {(maximum polishing rate−minimum polishing rate) / average polishing rate} × 100

(Unpolished)
Using an SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, the degree of unpolishing at a position of 2 mm from the peripheral edge of the wafer to the inside was measured using the prepared polishing pad. The degree of unpolished was measured by the following method. Using an 8 inch silicon wafer deposited with 1 μm of thermal oxide film, polishing was performed under the following polishing conditions until the thermal oxide film reached about 0.5 μm, and the same operation was repeated 500 times. Then, on the 500th wafer, as shown in FIG. 3, the average polishing rate was calculated from the film thickness measurement values before and after polishing at 77 specific positions on the wafer (at intervals of 5 mm). Further, the polishing rate X at a position 2 mm inward from the peripheral edge of the wafer was measured. 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.
The unpolished degree is calculated by the following formula. In addition, it represents that it is an unpolished state, so that the value of unpolished degree becomes smaller than one. The unpolished degree is preferably 0.90 or more, more preferably 0.92 or more. If the degree is not less than the above value, it can be said that the polishing state is desirable.
Unpolished = Polishing speed X / Average polishing speed

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 (manufactured by Toray Dow Corning Silicon, SH-192) 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 put in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block.
The polyurethane foam block heated to about 80 ° C. was sliced using a slicer (AGW, manufactured by VGW-125), and a polyurethane foam sheet (average cell diameter: 50 μm, specific gravity: 0.86, hardness: 52 degrees). ) Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 0.3 mm to obtain a sheet with adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing layer.

  The polyurethane foam sheet obtained by slicing by the above-described method was subjected to surface buffing with a buffing machine until the thickness reached 2 mm to obtain a sheet with adjusted thickness accuracy. The buffed sheet was punched out with a diameter of 61 cm to obtain an intermediate layer.

  Double-sided tape (Sekisui Chemical Co., Ltd., # 5673JX, substrate: PET film with a thickness of 23 μm, adhesive layer: acrylic with a thickness of 50 μm) using a laminator on the surface opposite to the grooved surface of the polishing layer System adhesive layer, shear stress: 710 kPa), and an intermediate layer was bonded to the other surface of the double-sided tape. Then, the double-sided tape was further bonded to the other surface of the intermediate layer, and a cushion layer (polyethylene foam, thickness 1.27 mm) was bonded to the other surface of the double-sided tape to prepare a polishing pad.

Example 2
A polishing pad was produced in the same manner as in Example 1 except that the thickness of the intermediate layer was changed from 2 mm to 0.5 mm.

Example 3
A polishing pad was produced in the same manner as in Example 1 except that the thickness of the polishing layer was changed from 0.3 mm to 1.5 mm.

Comparative Example 1
The thickness of the polishing layer was changed from 0.3 mm to 2 mm, an intermediate layer was not provided, and as a double-sided tape, # 5782 manufactured by Sekisui Chemical Co., Ltd. (base material: non-woven fabric, adhesive layer: acrylic adhesive layer, shear stress) : 400 kPa) was used to prepare a polishing pad in the same manner as in Example 1.

Comparative Example 2
A polishing pad was prepared in the same manner as in Example 1 except that the intermediate layer was not provided and # 5782 was used as the double-sided tape.

表１から、本発明の研磨パッドは面内均一性に優れ、ウエハ極端部まで均一に研磨できることがわかる。 Comparative Example 3
A polishing pad was produced in the same manner as in Example 1 except that the thickness of the polishing layer was changed from 0.3 mm to 2.3 mm, the intermediate layer was not provided, and # 5782 was used as a double-sided tape.

From Table 1, it can be seen that the polishing pad of the present invention is excellent in in-plane uniformity and can be polished uniformly to the extreme part of the wafer.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic sectional view showing the structure of the polishing pad of the present invention Schematic showing 77 film thickness measurement positions on the 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 8: Polishing layer 9: Intermediate layer 10: Cushion layer 11, 12: Double-sided tape

Claims (2)

In the polishing pad in which the polishing layer and the cushion layer are laminated via a double-sided tape, an intermediate layer made of the same material as the polishing layer and thicker than the polishing layer is provided between the polishing layer and the cushion layer.
The thickness of the polishing layer is 0.3 to 1.5 mm, the thickness of the intermediate layer is 0.5 to 2 mm, the thickness of the cushion layer is 0.5 to 2 mm,
A polishing pad, wherein the base material of the double-sided tape between the polishing layer and the intermediate layer is a polyester film. A method for manufacturing a semiconductor device, comprising: holding a semiconductor wafer with a retainer ring; and polishing the surface of the semiconductor wafer by pressing the semiconductor wafer together with the retainer ring against a polishing pad by a pressure mechanism,
The method of manufacturing a semiconductor device, wherein the polishing pad is the polishing pad according to claim 1 .

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