JP2007038372A - Laminated polishing pad and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polishing pad, hardly causing separation between a polishing layer and a cushion layer, a manufacturing method thereof, and a manufacturing method of a semiconductor device using a laminated polishing pad. <P>SOLUTION: In this laminated polishing pad, a polishing layer and a cushion layer are stuck to each other through a pressure sensitive adhesive layer, and the arithmetic average roughness (Ra) of the surface coming into contact with the adhesive layer of the polishing layer is 1 μm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 polishing pad is disclosed in which a relatively hard first layer and a relatively soft second layer are laminated, and a groove having a predetermined pitch or a protrusion having a predetermined shape is provided on the polishing surface of the first layer. (Patent Document 1).

  Also, a first sheet-like member having elasticity and having irregularities formed on the surface, and a surface that is provided on the surface of the first sheet-like member on which the irregularities are formed and that faces the surface to be polished of the substrate to be processed. An abrasive cloth having a second sheet-like portion is disclosed (Patent Document 2).

  Further, a polishing pad is disclosed that includes a polishing layer and a support layer that is laminated on one surface of the polishing layer and is a foam having a larger compressibility than the polishing layer (Patent Document 3).

  Further, a polishing pad is disclosed in which a polishing layer and a cushion layer are bonded with a double-separated double-sided tape (Patent Document 4).

  Furthermore, a manufacturing method of a polishing pad is disclosed in which a polishing layer and a cushion layer are preliminarily bonded with a double-sided tape, and then main bonding is performed (Patent Document 5).

  However, since the conventional laminated polishing pad is manufactured by bonding the polishing layer and the cushion layer with a double-sided tape (adhesive layer), the slurry enters between the polishing layer and the cushion layer during polishing. There was a problem that the adhesive force of the double-sided tape was weakened, and as a result, the polishing layer and the cushion layer were peeled off. In particular, when polishing metal films for wiring (Al, W, Cu, etc.), an acidic slurry having a pH of about 2 to 4 containing an oxidizing agent such as iron nitrate, hydrogen peroxide solution or potassium iodate is used. When such an acidic slurry was used, the polishing layer and the cushion layer were easy to peel off.

JP 2003-53657 A JP-A-10-329005 JP 2004-25407 A JP 2004-140215 A JP 2004-193390 A

  An object of this invention is to provide the lamination | stacking polishing pad which does not peel between a polishing layer and a cushion layer, and its manufacturing method. It is another object of the present invention to provide a method for manufacturing a semiconductor device using the laminated polishing pad.

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

  That is, the present invention is a laminated polishing pad in which the polishing layer and the cushion layer are bonded together via an adhesive layer, and the arithmetic average roughness (Ra) of the surface contacting the adhesive layer of the polishing layer is 1 μm or less, About.

  The polishing layer of a conventional laminated polishing pad is: 1) A method in which a resin material is poured into a mold to produce a resin block, and the resin block is sliced with a slicer. 2) A resin material is poured into a mold and pressed. It was manufactured by a method of forming a thin sheet, 3) a method of dissolving a resin as a raw material, and extruding from a T-die to form a sheet directly. And the polishing layer produced by such a method is usually buffed with sandpaper or the like in order to reduce the thickness variation.

  The present inventors considered that the polishing layer and the cushion layer of the conventional laminated polishing pad are easily separated from each other in the buffing step of the polishing layer. That is, the buffing reduces the thickness variation of the polishing layer, but grinding marks are generated on the surface of the polishing layer at that time. Then, when the polishing layer and the cushion layer are bonded together via the adhesive layer, a gap due to the grinding marks is likely to occur at the interface between the polishing layer and the adhesive layer. As a result, it is considered that the slurry easily enters the gap and the adhesive force of the adhesive layer is weakened. In particular, when an acidic slurry is used, it is considered that the oxidizing agent is decomposed in the gaps to generate bubbles, whereby the polishing layer and the adhesive layer are more easily separated.

  On the other hand, the laminated polishing pad of the present invention has an arithmetic average roughness (Ra) of the surface contacting the adhesive layer of the polishing layer of 1 μm or less, and there is almost no gap at the interface between the polishing layer and the adhesive layer. It can be effectively prevented. Therefore, the polishing layer and the cushion layer do not peel off during polishing. Since the laminated polishing pad of the present invention can effectively prevent peeling even when polishing using an acidic slurry, it is suitably used for polishing a metal film for wiring. Moreover, when the optical detection window is provided in the polishing layer, the polishing layer and the adhesive layer are in close contact with each other without any gap, so that water leakage from the detection window can be prevented.

  In the laminated polishing pad, it is preferable that the thickness of the adhesive layer in contact with the polishing layer is 100 to 200 μm. The thickness of the adhesive layer of the conventional double-sided tape is about 40 μm, and the followability to the grinding mark of the polishing layer is poor, and a gap is easily generated. By making the thickness of the adhesive layer in contact with the polishing layer 100 to 200 μm as in the present invention, the followability of the adhesive layer to the grinding mark is improved, and the gap between the polishing layer and the adhesive layer is further reduced. be able to.

  In the present invention, the surface of the polishing layer that comes into contact with the adhesive layer is buffed with an abrasive having an abrasive grain size of 600 to 1000, and the arithmetic average roughness (Ra) of the surface is adjusted to 1 μm or less. The present invention relates to a method for manufacturing a laminated polishing pad including a step of bonding, and a step of bonding the polishing layer and the cushion layer through an adhesive layer, and a laminated polishing pad produced by the method.

  In the method for producing the laminated polishing pad, before buffing the surface of the polishing layer that contacts the adhesive layer with an abrasive having an abrasive grain size of 600 to 1000, the abrasive grain size is 120 to 240. It is preferable to buff in a multistage manner using an abrasive and an abrasive having an abrasive grain size of 400 to 580. By buffing in multiple stages, the thickness variation can be reduced in a short time. Further, when buffing in multiple stages, the surface roughness of the polishing layer can be easily controlled by reducing the abrasive grain size of the abrasive in stages. In order to obtain a polishing layer having a small surface roughness, it is preferable to use one having a large abrasive grain size in the initial buffing and gradually changing to a grain having a small abrasive grain size. When the abrasive grain size is gradually reduced, grinding marks with initial large abrasive grains can be effectively removed.

  Moreover, in the said manufacturing method, it is preferable that the thickness of the adhesion layer which contacts a grinding | polishing layer is 100-200 micrometers.

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

  The polishing layer in the present invention is not particularly limited as long as it is a foam 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 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 component, low molecular weight polyol component), 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 component include polyether polyols represented by polytetramethylene ether glycol, polyester polyols represented by polybutylene adipate, polycaprolactone polyols, and a reaction product of a polyester glycol such as polycaprolactone and an alkylene carbonate. Exemplified polyester polycarbonate polyol, polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol, and then reacting the obtained reaction mixture with organic dicarboxylic acid, and polycarbonate obtained by transesterification reaction between polyhydroxyl compound and aryl carbonate A polyol etc. are mentioned. These may be used alone or in combination of two or more.

  The number average molecular weight of the high molecular weight polyol component 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 high molecular weight polyol component described above as the polyol component, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1, A low molecular weight polyol component such as 4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene is preferably used in combination. Low molecular weight polyamine components such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine may be used. The (number average) molecular weight of the low molecular weight polyol component or the low molecular weight polyamine component is less than 500, preferably 250 or less.

  The ratio of the high molecular weight polyol to the low molecular weight polyol 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 Diamines, N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and polyamines exemplified by p-xylylenediamine, or the above-described low molecular weight polyol components and low molecular weight polyamine components Can be mentioned. 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 suitable silicon-based surfactants 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 micro-bubble type polyurethane foam constituting the polishing layer 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 flatness of the polished material (wafer) after polishing tends to decrease.

  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 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.

  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 the method for reducing the variation in the thickness of the polishing layer include a method of buffing one side or both sides of the sheet-like polishing layer obtained by the above method.

  In the method for producing a laminated polishing pad of the present invention, when buffing the polishing layer, the abrasive grain size is 600 to 1000 in order not to generate large grinding marks on the surface of the polishing layer to be bonded to the adhesive layer (the back surface of the polishing layer). Buffing is performed using a count abrasive, and the arithmetic average roughness (Ra) of the back surface of the polishing layer after buffing is adjusted to 1 μm or less. The abrasive grain size of the abrasive is preferably 800 to 1000. In addition, before buffing the back surface of the polishing layer using the above-mentioned abrasive, buffing is performed in multiple stages using an abrasive having an abrasive grain size of 120 to 240 and an abrasive having an abrasive grain size of 400 to 580. It is preferable to do.

  The arithmetic average roughness (Ra) of the back surface of the polishing layer after buffing by the above method is preferably 0.9 μm or less. When the arithmetic average roughness (Ra) on the back surface of the polishing layer exceeds 1 μm, a large gap is generated when the polishing layer and the adhesive layer are bonded together, and it is impossible to prevent the slurry from entering the interlayer.

  In addition, when buffing the surface of the polishing layer that comes into contact with the material to be polished (wafer), a polishing material having an abrasive particle size of 120 to 240 and an abrasive particle size of 400 to 580 are used. It is preferable to buff in stages. The surface of the polishing layer that comes into contact with the material to be polished is usually conspicuous using a dresser before polishing the material to be polished, so it is not necessary to reduce the surface roughness as much as the back surface, but it is about 400 to 580. It is preferable that the final finishing is performed using this abrasive.

  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 laminated 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 material for the adhesive layer is not particularly limited, and known materials can be used. The pressure-sensitive adhesive layer may have a structure in which a pressure-sensitive adhesive is provided on both surfaces of a substrate such as a nonwoven fabric or a film, such as a double-sided tape. Examples of the composition of the pressure-sensitive adhesive include rubber-based and acrylic-based materials. Considering the metal ion content, the acrylic pressure-sensitive adhesive is preferable because the metal ion content is small. In addition, since the composition of the polishing layer and the cushion sheet may be different, the composition of each adhesive of the double-sided tape can be made different so that the adhesive strength of each layer can be optimized.

  The thickness of the pressure-sensitive adhesive layer in contact with the polishing layer (in the case of a double-sided tape, the thickness of the pressure-sensitive adhesive in contact with the polishing layer) is preferably 100 to 200 μm, more preferably 120 to 180 μm. When the thickness is less than 100 μm, the followability of the polishing layer to the grinding marks is poor and gaps are likely to occur. On the other hand, when the thickness exceeds 200 μm, it tends to cause cohesive failure of the adhesive layer itself when a shearing force is applied.

  Examples of the means for bonding the polishing layer and the cushion layer include a method in which the polishing layer and the cushion layer are sandwiched between an adhesive layer or a double-sided tape and pressed.

  The laminated 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 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 laminated 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 laminated polishing pad 1, a support table (polishing head) 5 that supports the semiconductor wafer 4, and the wafer. This is carried out using a backing material for performing uniform pressurization and a polishing apparatus equipped with a polishing agent 3 supply mechanism. The laminated 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 arranged so that the laminated 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 pressure mechanism for pressing the semiconductor wafer 4 against the laminated polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the laminated 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]
(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 arithmetic average roughness)
Based on JIS B0601-1994, the arithmetic average roughness (micrometer) of the surface which contacts the adhesion layer of a grinding | polishing layer was measured. However, the measurement was performed in a portion without bubbles.

(Measurement of average bubble diameter of polishing layer)
A sample for measuring the average bubble diameter was prepared by cutting the produced polishing layer as thin as possible to a thickness of 1 mm or less in parallel with a microtome cutter. The sample was fixed on a slide glass, and the total bubble diameter in an arbitrary 0.2 mm × 0.2 mm range was measured using an image processing apparatus (Image Analyzer V10, manufactured by Toyobo Co., Ltd.), and the average bubble diameter was calculated.

(Evaluation of peeling of laminated polishing pad)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, peeling evaluation of the produced laminated polishing pad was performed. Using the produced laminated polishing pad, an 8-inch silicon wafer having a 1 μm thick W film is polished by about 0.5 μm. The polishing process was repeated, and the number of wafers until the polishing layer and the cushion layer were peeled was measured. As polishing conditions, acidic slurry (CHS3000EM slurry, manufactured by Shibaura Mechatronics) was added at a flow rate of 200 ml / min during polishing. The polishing load was 300 g / cm ² , the polishing platen rotation speed was 63 rpm, and the wafer rotation speed was 60 rpm.

Example 1
(Production of laminated polishing pad)
Toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20) 14790 parts by weight, 4,4′-dicyclohexylmethane diisocyanate 3930 parts by weight, polytetramethylene glycol (number average molecular weight: 1006) 25150 parts by weight And 2756 parts by weight of diethylene glycol were mixed and heated and stirred at 80 ° C. for 120 minutes to obtain an isocyanate-terminated prepolymer (isocyanate equivalent: 2.1 meq / g). In the reaction vessel, 100 parts by weight of the prepolymer and 3 parts by weight of a silicone surfactant (manufactured by Toray Dow Silicone, SH192) were mixed, and the temperature was adjusted to 80 ° C. 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. 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Amine, Iharacamine MT) previously melted at 120 ° C. was added thereto to obtain a mixed solution. 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 was sliced using a band saw type slicer to obtain a polyurethane foam sheet. And the both surfaces of this polyurethane foam sheet were buffed using the buff machine (made by Amitech) provided with the 120th sandpaper. Thereafter, a 240th sandpaper and a 400th sandpaper were buffed in a multi-step manner in the same manner as described above to obtain a sheet (thickness: 1.27 mm) having a adjusted thickness accuracy. Further, one side of the sheet (the surface in contact with the adhesive layer) was buffed using a 600th sandpaper, and the arithmetic average roughness (Ra) of the surface was adjusted to 0.8 μm. The buffed sheet is punched out with a diameter of 61 cm, and concentric grooves with a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm are formed on the surface using a groove processing machine. A polishing layer (average cell diameter: 50 μm) was prepared. A pressure-sensitive adhesive layer (acrylic pressure-sensitive adhesive, thickness: 120 μm) was attached to the surface of the polishing layer opposite to the grooved surface (the surface in contact with the pressure-sensitive adhesive layer) using a laminator. Then, the corona-treated cushion layer (Toray Industries, polyethylene foam, Torepefu, thickness: 0.8 mm) was buffed and bonded to the adhesive layer using a laminator. Furthermore, a laminated polishing pad was prepared by laminating a double-sided tape on the other surface of the cushion layer using a laminator.

Comparative Example 1
A polyurethane foam block was obtained in the same manner as in Example 1.
The polyurethane foam block was sliced using a band saw type slicer to obtain a polyurethane foam sheet. And the both surfaces of this polyurethane foam sheet were buffed using the buff machine (made by Amitech) provided with the 120th sandpaper. Thereafter, a 240th sandpaper and a 400th sandpaper were buffed in a multi-step manner in the same manner as described above to obtain a sheet (thickness: 1.27 mm) having a adjusted thickness accuracy. The arithmetic average roughness (Ra) of one side of the sheet (the surface in contact with the adhesive layer) was 1.5 μm. The buffed sheet is punched out with a diameter of 61 cm, and concentric grooves with a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm are formed on the surface using a groove processing machine. A polishing layer was prepared. A pressure-sensitive adhesive layer (acrylic pressure-sensitive adhesive, thickness: 40 μm) was attached to the surface of the polishing layer opposite to the grooved surface (the surface in contact with the pressure-sensitive adhesive layer) using a laminator. Thereafter, a laminated polishing pad was produced in the same manner as in Example 1.

  When peeling evaluation was performed using the laminated polishing pad obtained in Example 1 and Comparative Example 1, the laminated polishing pad of Example 1 peeled off the polishing layer and the cushion layer even when 1000 wafers were polished. Although not generated, peeling of the polishing layer and the cushion layer occurred after polishing 400 laminated polishing pads of Comparative Example 1.

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

Explanation of symbols

1: Laminated 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 (7)

A laminated polishing pad, wherein a polishing layer and a cushion layer are bonded together via an adhesive layer, and an arithmetic average roughness (Ra) of a surface of the polishing layer that contacts the adhesive layer is 1 μm or less. The laminated polishing pad according to claim 1, wherein the thickness of the adhesive layer in contact with the polishing layer is 100 to 200 μm. Buffing the surface of the polishing layer that is in contact with the adhesive layer with an abrasive having an abrasive grain size of 600 to 1000, and adjusting the arithmetic average roughness (Ra) of the surface to 1 μm or less, and the polishing A method for producing a laminated polishing pad, comprising a step of bonding a layer and a cushion layer through an adhesive layer. Before buffing the surface of the polishing layer in contact with the adhesive layer with an abrasive having an abrasive grain size of 600 to 1000, the abrasive with an abrasive grain size of 120 to 240 and an abrasive grain size of 400 to 580 The manufacturing method of the lamination | stacking polishing pad of Claim 3 including the process of buffing in multiple steps using a count abrasive | polishing material. The method for producing a laminated polishing pad according to claim 3 or 4, wherein the pressure-sensitive adhesive layer in contact with the polishing layer has a thickness of 100 to 200 µm. A laminated polishing pad produced by the method according to claim 3. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the laminated polishing pad according to claim 1.

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