JP4786347B2 - 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 layers and metal layers in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC, LSI, and other 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.

  The polishing characteristics of the polishing pad are required to be excellent in the flatness (planarity) and in-plane uniformity of the object to be polished and to have a high polishing rate. The flatness and in-plane uniformity of the object to be polished can be improved to some extent by increasing the elastic modulus of the polishing layer. The polishing rate can be improved by using a foam containing bubbles and increasing the amount of slurry retained.

  As a polishing pad that satisfies the above characteristics, a polishing pad made of a polyurethane resin foam has been proposed (Patent Documents 1 and 2). The polyurethane resin foam is produced by reacting an isocyanate-terminated prepolymer with a chain extender (curing agent). As the polymer polyol component of the isocyanate prepolymer, hydrolysis resistance, elastic properties, From the viewpoint of wear and the like, polyether (polytetramethylene glycol having a number average molecular weight of 500 to 1600) and polycarbonate are used as suitable materials.

  Normally, when a large number of semiconductor wafers are planarized using a polishing pad, the fine irregularities on the surface of the polishing pad wear out, and the ability to supply an abrasive (slurry) to the processing surface of the semiconductor wafer is reduced. The flattening speed of the wafer processing surface is reduced or the flattening characteristics are deteriorated. For this reason, it is necessary to update and roughen (dress) the surface of the polishing pad using a dresser after the planarization of a predetermined number of semiconductor wafers. When dressing is performed for a predetermined time, innumerable fine irregularities are formed on the surface of the polishing pad, and the pad surface becomes fuzzy.

  However, the conventional polishing pad has a problem that the dressing speed at the time of dressing is low and the dressing takes too much time.

JP 2000-17252 A Japanese Patent No. 3359629

  An object of the present invention is to provide a polishing pad having improved dressing properties while maintaining the flattening characteristics and polishing rate of a conventional polishing pad. 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 is characterized in that, in a polishing pad having a polishing layer made of a polyurethane resin foam having fine bubbles, the isocyanate component which is a raw material of the polyurethane resin foam is a multimerized diisocyanate and an aromatic diisocyanate. The present invention relates to a polishing pad.

  The polishing pad of the present invention has improved dressing properties while maintaining the flattening characteristics and polishing rate of conventional polishing pads. When the polishing pad is used, the dressing time can be shortened, so that the manufacturing efficiency of the semiconductor wafer can be remarkably improved. The reason why the conventional polishing pad is difficult to dress is that 1) the specific gravity of the polishing layer is high, and 2) there is “stickiness” in the material of the polishing layer itself. It is considered that the specific gravity should be lowered in order to facilitate dressing the surface of the polishing layer, but simply reducing the specific gravity is not preferable because the hardness of the entire polishing pad is lowered and the planarization characteristics are deteriorated. In order to maintain the hardness while reducing the specific gravity, it is conceivable to reduce the molecular weight of the high molecular weight polyol, but in this case, the surface wear of the polishing layer is increased more than necessary, and the life of the polishing pad is increased. There is a tendency that fluffing on the surface of the polishing layer after dressing is shortened or removed immediately at the time of wafer polishing and the polishing rate is reduced.

  The inventors of the present invention are able to reduce the “stickiness” of the material itself while maintaining high hardness by using together the dimerized diisocyanate and the aromatic diisocyanate as the isocyanate component that is the raw material of the polyurethane resin foam. I found it.

  The polyurethane resin foam is preferably a reaction cured product of an isocyanate-terminated prepolymer containing a multimerized diisocyanate and an aromatic diisocyanate and a chain extender. A polyurethane resin foam obtained by the prepolymer method is preferable because of its excellent polishing characteristics.

  The content weight ratio of the multimerized diisocyanate to the aromatic diisocyanate (the former / the latter) is preferably from 1/99 to 65/35, more preferably from 5/95 to 50/50. When the blending ratio of the multimerized diisocyanate is less than 1% by weight, the “stickiness” of the polyurethane resin itself cannot be sufficiently reduced, so that the dressing property of the polishing layer cannot be sufficiently improved. In addition, the pot life when the isocyanate component and the chain extender are reacted tends to be short, and the handling property tends to be poor. On the other hand, when the blending ratio of the dimerized diisocyanate exceeds 65% by weight, it is not preferable because the dressing speed becomes too high and the life of the polishing pad becomes too short.

  In the present invention, the multimerized diisocyanate is preferably a multimerized aliphatic diisocyanate, and the aromatic diisocyanate is preferably toluene diisocyanate. In particular, the multimerized aliphatic diisocyanate is preferably a multimerized hexamethylene diisocyanate. By using these, a polyurethane resin foam can be produced with good handling properties, and the planarization characteristics and dressing properties can be improved without reducing the polishing rate. The multimerized diisocyanate is preferably urethane-modified. By using urethane-modified multimerized diisocyanate, it is possible to improve polishing characteristics such as planarization characteristics.

  Moreover, it is preferable that the specific gravity of a polyurethane resin foam is 0.5-1.0, More preferably, it is 0.7-0.9. When the specific gravity is less than 0.5, the hardness of the entire polishing layer is lowered and the planarization characteristics are deteriorated, the surface wear of the polishing layer is increased more than necessary, and the life of the polishing pad is shortened. The fuzz on the surface of the subsequent polishing layer tends to be removed immediately at the time of wafer polishing and the polishing rate tends to decrease. On the other hand, when the specific gravity exceeds 1.0, the dressing property of the polishing layer cannot be sufficiently improved.

  The polyurethane resin foam preferably has an Asker D hardness of 45 to 65 degrees, more preferably 50 to 60 degrees. When Asker D hardness is less than 45 degrees, the flatness of the material to be polished tends to decrease. On the other hand, when it is larger than 65 degrees, the flatness is good, but the in-plane uniformity of the material to be polished tends to be lowered. In addition, scratches are likely to occur on the surface of the material to be polished.

  Moreover, in this invention, it is preferable that the said polyurethane resin foam contains 0.05-10 weight% of silicon-type nonionic surfactant, More preferably, it is 0.5-5 weight%. When the amount of the silicon-based nonionic surfactant is less than 0.05% by weight, a fine-bubble foam tends to be not obtained. On the other hand, when it exceeds 10% by weight, a polyurethane resin foam having a high hardness tends to be difficult to obtain due to the plasticizing effect of the surfactant.

  Further, the dressing speed of the polishing pad of the present invention is preferably 4.5 to 10 μm / min, more preferably 5 to 8 μm / min. When the dressing speed is less than 4.5 μm / min, the effect of shortening the dressing time is insufficient, and it becomes difficult to improve the manufacturing efficiency of the semiconductor wafer. On the other hand, when the dressing speed exceeds 10 μm / min, the surface wear of the polishing layer is increased more than necessary, and the life of the polishing pad is shortened, and fluffing on the surface of the polishing layer after dressing is immediately removed during wafer polishing. Therefore, the polishing rate tends to decrease.

  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 pad of the present invention has a polishing layer made of a polyurethane resin foam having fine bubbles. The polishing pad of the present invention may be only the polishing layer or a laminate of the polishing layer and another layer (for example, a cushion layer).

  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.

  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, it is necessary to use a multimerized diisocyanate and an aromatic diisocyanate in combination.

  The multimerized diisocyanate in the present invention is an isocyanate-modified product or a mixture thereof that has been multimerized by adding three or more diisocyanates. Examples of the modified isocyanate include 1) trimethylolpropane adduct type, 2) burette type, and 3) isocyanurate type, with isocyanurate type being particularly preferred. In the case of a mixture, it is necessary that the isocyanate-modified product contains 50% by weight or more, and preferably 60% by weight or more. Moreover, in the case of a mixture, it is preferable that 25 weight% or more of trimerization diisocyanates are contained, More preferably, it is 35 weight% or more.

  As the diisocyanate, a compound known in the field of polyurethane can be used without particular limitation. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, Aromatic diisocyanates such as 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate; ethylene diisocyanate, 2,2,4 -Aliphatic diisocyanates such as trimethylhexamethylene diisocyanate and 1,6-hexamethylene diisocyanate; 1,4-cyclohexanediisocyanate DOO, cyclohexane diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, isophorone diisocyanate, and cycloaliphatic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  In the present invention, aliphatic diisocyanate is preferably used as the diisocyanate forming the multimerized diisocyanate, and 1,6-hexamethylene diisocyanate is particularly preferably used. The multimerized diisocyanate may be modified by urethane modification, allophanate modification, burette modification or the like.

  In the present invention, the aromatic diisocyanate is preferably toluene diisocyanate.

  Examples of the high molecular weight polyol component include polyether polyols typified by polytetramethylene ether glycol, polyester polyols typified by polybutylene adipate, polycaprolactone polyol, and a reaction product of polyester glycol such as polycaprolactone and 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, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis ( 2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-teto Tetrakis (hydroxymethyl) cyclohexanol, diethanolamine, N- methyldiethanolamine, and can be used in combination a low molecular weight polyol component such as triethanolamine. Moreover, low molecular weight polyamine components such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine can be used in combination. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more. The blending amount of the low molecular weight polyol, the low molecular weight polyamine or the like is not particularly limited, and is appropriately determined depending on the properties required for the polishing pad (polishing layer) to be produced, and is 20 to 70 mol% of the total polyol component. Is preferred.

  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 resin 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 polyol component and the low molecular weight polyamine component described above. These may be used alone or in combination of two or more. In particular, it is preferable to use non-halogen aromatic diamines such as 3,5-bis (methylthio) -2,4-toluenediamine and 3,5-bis (methylthio) -2,6-toluenediamine.

  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 resin 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, work environment, and the like.

  The polyurethane resin foam can be produced by either the prepolymer method or the one-shot method. However, an isocyanate-terminated prepolymer is synthesized beforehand from an isocyanate component and a polyol component, and this is reacted with a chain extender. The polymer method 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 resin 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 a polyurethane resin foam include a method of adding hollow beads, a mechanical foaming method, and a chemical foaming method.

  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. As such a silicon-based nonionic surfactant, L-5340 (manufactured by Nippon Unica) and the like are exemplified as a suitable compound.

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

An example of a method for producing a fine cell type polyurethane resin foam constituting the polishing pad (polishing layer) will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
1) Foaming process for producing a cell dispersion of isocyanate-terminated prepolymer A silicon-based nonionic surfactant is added to the isocyanate-terminated prepolymer (first component), and the mixture is stirred in the presence of a non-reactive gas to produce a non-reactive gas. Is dispersed as fine bubbles to obtain a bubble dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing Agent (Chain Extender) Mixing Step A chain extender (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.

  As the stirring device for dispersing the non-reactive gas in the form of fine bubbles and dispersing in the first component containing the silicon-based nonionic surfactant, a known stirring device can be used without particular limitation. Specifically, a homogenizer, a dissolver, A two-axis planetary mixer (planetary mixer) is exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained.

  In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a cell dispersion in a foaming process, and the stirring which adds and mixes the chain extender in a mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the foaming step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

  In the method for producing a polyurethane resin foam, heating and post-curing the foam that has reacted until the foaming reaction liquid is poured into the mold and no longer flows has the effect of improving the physical properties of the foam. Is preferred. The foam reaction solution may be poured into the mold and immediately put into a heating oven for post cure, and heat is not immediately transferred to the reaction components under such conditions, so the bubble size does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

  In the polyurethane resin foam, a known catalyst that promotes a 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 resin foam can be manufactured by batch feeding each component into a container and stirring, or by continuously supplying each component and non-reactive gas to the stirring device and stirring, It may be a continuous production method in which a dispersion is sent out to produce a molded product.

  In addition, the prepolymer that is the raw material of the polyurethane resin foam is placed in a reaction vessel, and then a chain extender is added and stirred, and then poured into a casting mold of a predetermined size to produce a block, and the block is shaped like a bowl or a band saw. In the method of slicing using a slicer, or in the above-described casting step, a thin sheet may be used. Alternatively, a raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.

  The average cell diameter of the polyurethane resin foam is preferably 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 polishing surface of the polishing pad (polishing layer) of the present invention that comes into contact with the material to be polished has 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. 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 1.5 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 a method for suppressing the variation in the thickness of the polishing layer include a method of buffing the surface of the polishing sheet sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

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

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

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

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

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

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

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

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

  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 content of dimerized diisocyanate)
The content of the multimerized diisocyanate was measured by GPC and calculated from the number average molecular weight converted by standard PPG and the peak area ratio.
GPC device: manufactured by Shimadzu Corporation, LC-10A
Column: Two Polymer Laboratories (PLgel, 3 μm, Mix E) are connected and used Flow rate: 0.7 ml / min
Concentration: 2.0 g / l
Injection volume: 40 μl
Column temperature: 40 ° C
Eluent: Tetrahydrofuran

(Average bubble diameter measurement)
A sample obtained by cutting the produced polyurethane resin foam in parallel with a microtome cutter as thin as possible to a thickness of 1 mm or less was 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 measurement)
This was performed according to JIS Z8807-1976. The produced polyurethane resin foam was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) and used as a sample for measuring specific gravity, and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. I put it. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

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

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.

  In the evaluation of the planarization characteristics, after depositing a thermal oxide film of 0.5 μm on an 8-inch silicon wafer and performing predetermined patterning, an oxide film of 1 μm is deposited by p-TEOS, and an initial step of 0.5 μm is formed. A wafer with a pattern was prepared, this wafer was polished under the above-mentioned conditions, and after polishing, each step was measured to evaluate the planarization characteristics.

  Two steps were measured as the flattening characteristics. One is a local step, which is a step in a pattern in which lines having a width of 270 μm are arranged in a space of 30 μm, and the step after one minute was measured. The other is the amount of scraping. In the pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and the pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the level difference between the above two patterns is 2000 mm or less. The amount of scraping of the 270 μm space was measured. When the numerical value of the local step is low, it indicates that the flattening speed in a certain time is high with respect to the unevenness of the oxide film caused by the pattern dependence on the wafer. Further, when the amount of scraping of the space is small, the amount of shaving of the portion that is not desired to be shaved is small and the flatness is high.

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

Example 1
1206 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20, hereinafter abbreviated as TDI) in a container, urethane modified product of multimerized 1,6-hexamethylene diisocyanate (Nippon Polyurethane Co., Ltd.) Manufactured, Coronate HX, isocyanurate type, trimer: 42 wt%, pentamer: 27 wt%, heptamer: 13 wt%) 253 parts by weight, number average molecular weight 1018 polytetramethylene ether glycol (hereinafter, 1954 parts by weight of PTMG) and 188 parts of diethylene glycol (hereinafter abbreviated as DEG) were added and reacted at 70 ° C. for 4 hours to obtain isocyanate-terminated prepolymer A. Coronate HX / TDI (weight ratio) is 17/83.
100 parts by weight of the prepolymer A and 3 parts by weight of a silicon-based nonionic surfactant (manufactured by Nippon Unika Co., Ltd., L-5340) 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. 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) (hereinafter abbreviated as MOCA) previously melted at 120 ° C. was added thereto. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block.
The polyurethane resin foam block heated to about 80 ° C. was sliced using a slicer (manufactured by Amitech, VGW-125) to obtain a polyurethane resin foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing sheet (polishing layer). A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was applied to the surface of the polishing sheet opposite to the grooved surface using a laminator. Furthermore, the surface of the cushion sheet (Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) subjected to corona treatment was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
The container was charged with 1063 parts by weight of TDI, 471 parts by weight of Coronate HX, 1885 parts by weight of PTMG, and 181 parts by weight of DEG, and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer B. Coronate HX / TDI (weight ratio) is 31/69.
A polishing pad was produced in the same manner as in Example 1 except that isocyanate-terminated prepolymer B was used instead of isocyanate-terminated prepolymer A and MOCA was added from 27 parts by weight to 27 parts by weight. did.

Example 3
882 parts by weight of TDI, 879 parts by weight of coronate HX, 1678 parts by weight of PTMG, and 161 parts by weight of DEG were placed in a container and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer C. Coronate HX / TDI (weight ratio) is 50/50.
A polishing pad was prepared in the same manner as in Example 1 except that the isocyanate-terminated prepolymer C was used in place of the isocyanate-terminated prepolymer A and the MOCA addition amount was changed from 26 parts by weight to 28 parts by weight. did.

Example 4
In Example 2, instead of MOCA (27 parts by weight) previously melted at 120 ° C., 3,5-bis (methylthio) -2,4-toluenediamine and 3,5-bis ( A polishing pad was prepared in the same manner as in Example 2 except that 21 parts by weight of a mixture of methylthio) -2,6-toluenediamine (Albemarle, Etacure 300) was used.

Example 5
In Example 2, instead of MOCA (27 parts by weight) previously melted at 120 ° C., polytetramethylene oxide-di-p-aminobenzoate (Ihara Chemical Industries, Elastomer 250P, average temperature adjusted to 70 ° C. in advance) Degree of polymerization: 3.2) A polishing pad was prepared in the same manner as in Example 2 except that 49 parts by weight were used.

Example 6
1173 parts by weight of TDI in a container, multimerized 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type, trimer: 55% by weight, pentamer: 22% by weight Hexamer: 11 wt%) 298 parts by weight, 1943 parts by weight of PTMG, and 187 parts by weight of DEG were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer D. N-3300 / TDI (weight ratio) is 20/80.
A polishing pad was prepared in the same manner as in Example 1 except that isocyanate-terminated prepolymer D was used instead of isocyanate-terminated prepolymer A in Example 1.

Example 7
1169 parts by weight of TDI in a container, multimerized 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumidur N-3200, burette type, trimer: 55% by weight, pentamer: 22% by weight, Heptamer: 11% by weight) 297 parts by weight, PTMG 1947 parts by weight, DEG 187 parts by weight were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer E. N-3200 / TDI (weight ratio) is 20/80.
A polishing pad was prepared in the same manner as in Example 1 except that isocyanate-terminated prepolymer E was used instead of isocyanate-terminated prepolymer A.

Example 8
In a container, 1058 parts by weight of TDI, 582 parts by weight of 1,6-hexamethylene diisocyanate (manufactured by Nippon Polyurethane, Coronate HL, trimethylolpropane adduct type, 75% ethyl acetate solution), 1788 parts by weight of PTMG, DEG After adding 172 parts by weight and reacting at 70 ° C. for 4 hours, ethyl acetate was removed under reduced pressure to obtain isocyanate-terminated prepolymer F. The coronate HL / TDI (weight ratio) is 29/71.
In Example 2, an isocyanate-terminated prepolymer F was used in place of the isocyanate-terminated prepolymer B, and a polishing pad was prepared in the same manner as in Example 2 except that the amount of MOCA added was changed from 27 parts by weight to 24 parts by weight. did.

Comparative Example 1
In a container, add 1229 parts by weight of TDI, 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, 1901 parts by weight of PTMG, and 198 parts by weight of DEG, and react for 4 hours at 70 ° C. to give isocyanate-terminated prepolymer G. Obtained.
A polishing pad was prepared in the same manner as in Example 1 except that isocyanate-terminated prepolymer G was used in place of isocyanate-terminated prepolymer A and MOCA was added from 26 parts by weight to 30 parts by weight. did.

Comparative Example 2
In a container, 1350 parts by weight of TDI, 2053 parts by weight of PTMG, and 197 parts by weight of DEG were placed and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer H.
A polishing pad was prepared in the same manner as in Example 1 except that isocyanate-terminated prepolymer H was used instead of isocyanate-terminated prepolymer A in Example 1.

Comparative Example 3
In a container, 631 parts by weight of TDI, 1352 parts by weight of Coronate HX, 1476 parts by weight of PTMG, and 142 parts by weight of DEG were allowed to react at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer I. Coronate HX / TDI (weight ratio) is 68/32.
A polishing pad was prepared in the same manner as in Example 1 except that the isocyanate-terminated prepolymer I was used in place of the isocyanate-terminated prepolymer A and the MOCA addition amount was changed from 26 parts by weight to 29 parts by weight. did.

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

  As is apparent from the results in Table 1, the polishing pad of the present invention using the dimerized diisocyanate and aromatic diisocyanate as the isocyanate component has improved dressing properties while maintaining the flattening characteristics and polishing rate. When the polishing pad is used, the dressing time can be shortened, so that the manufacturing efficiency of the semiconductor wafer can be remarkably improved.

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

Explanation of symbols

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

Claims (10)

In the polishing pad having a polishing layer comprising a polyurethane resin foam having fine bubbles, the polyurethane resin foam is a starting material isocyanate component Ri polymerized diisocyanate and an aromatic diisocyanate der, the polymerized diisocyanate and an aromatic diisocyanate a polishing pad containing weight ratio (the former / the latter) is characterized in 5 / 95-50 / 50 der Rukoto. 2. The polishing pad according to claim 1, wherein the polyurethane resin foam is a reaction cured product of an isocyanate-terminated prepolymer containing a multimerized diisocyanate and an aromatic diisocyanate and a chain extender. The polishing pad according to claim 1 or 2 , wherein the multimerized diisocyanate is a multimerized aliphatic diisocyanate, and the aromatic diisocyanate is toluene diisocyanate. The polishing pad according to claim 3 , wherein the multimerized aliphatic diisocyanate is a multimerized hexamethylene diisocyanate. Polymerized diisocyanate, the polishing pad according to any one of claims 1 to 4, which has been urethane modified. The polishing pad according to any one of claims 1 to 5 , wherein the polyurethane resin foam has a specific gravity of 0.5 to 1.0. The polishing pad according to any one of claims 1 to 6 , wherein the polyurethane resin foam has an Asker D hardness of 45 to 65 degrees. Polyurethane foam, a polishing pad according to any one of claims 1 to 7, containing nonionic silicone surfactant 0.05 to 10 wt%. The polishing pad according to any one of claims 1-8 dress rate is 4.5~10μm / min. The method of manufacturing a semiconductor device including a step of polishing a surface of a semiconductor wafer using a polishing pad according to any one of claims 1-9.