JP2006320982A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad having high polishing speed and excellent flattening characteristic, and a method of manufacturing a semiconductor device using the polishing pad. <P>SOLUTION: This polishing pad 1 includes a polishing layer formed of polyurethane resin foam having micro cells, wherein high molecular weight polyol component, which is raw material component of the polyurethane resin foam, is hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850, and the polyurethane resin foam 10 to 20 wt.% silicone nonionic surface active agent having no hydroxyl group. <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, 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 high molecular weight polyol component of the isocyanate prepolymer, hydrolysis resistance, elastic properties, From the viewpoint of wear and the like, polyether (particularly, polytetramethylene glycol having a number average molecular weight of 500 to 1600) and polycarbonate are used as suitable materials.

  However, when the polishing layer is made to have a high elastic modulus (high hardness) in order to improve the planarization characteristics of the polishing pad, the specific gravity increases, and as a result, the number of bubbles per unit area decreases and the polishing rate decreases. There was a problem.

JP 2000-17252 A Japanese Patent No. 3359629

  An object of this invention is to provide the polishing pad which has a high polishing rate and is excellent in the planarization characteristic. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

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

  That is, the present invention provides a polishing pad having a polishing layer made of a polyurethane resin foam having fine bubbles, wherein the high molecular weight polyol component, which is a raw material component of the polyurethane resin foam, has a number average molecular weight of 500 to 850. The polyurethane resin foam according to the present invention relates to a polishing pad comprising 10 to 20% by weight of a silicon-based nonionic surfactant having a molecular weight polyol and having no hydroxyl group.

  The polishing pad of the present invention has a high polishing rate and excellent planarization characteristics.

  The present inventors use a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850 as a high molecular weight polyol component that is a raw material component of a polyurethane resin foam, thereby reducing the molecular weight between crosslinks of the polyurethane, It has been found that the elastic modulus can be increased without increasing the specific gravity of the foam (without reducing the number of bubbles). In addition, when a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850 is used, the dressing property of the polyurethane resin is increased, and thus fluffing on the surface of the polishing layer after dressing is immediately removed during wafer polishing. The hydrophobicity of the polyurethane resin is increased and the wettability with the slurry is deteriorated. As a result, the polishing rate tended to decrease. The present inventors have found that the problem of decrease in the polishing rate can be solved by using a specific amount of a silicon-based nonionic surfactant together with a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850. In addition, the use of the hydrophobic high molecular weight polyol increases the brittleness of the polyurethane resin foam, and the workability of the polishing layer tends to be remarkably impaired. However, a specific amount of the silicon-based nonionic surfactant is added. It was found that the problem of workability can be solved.

  When the number average molecular weight of the hydrophobic high molecular weight polyol is less than 500, the polyurethane resin foam becomes too brittle, the polishing layer is chipped or cracked, or the surface wear of the polishing layer is more than necessary. The polishing pad becomes longer and the life of the polishing pad is shortened, and the fluffing on the surface of the polishing layer after dressing is immediately removed at the time of wafer polishing, and the polishing rate is reduced. On the other hand, when the number average molecular weight exceeds 850, it becomes difficult to increase the elastic modulus (high hardness) of the polishing layer, and the planarization characteristics cannot be improved.

  The number average molecular weight of the hydrophobic high molecular weight polyol is preferably 550 to 800, more preferably 600 to 700.

  Further, the polyurethane resin foam needs to contain 10 to 20% by weight, preferably 11 to 15% by weight, of a silicon-based nonionic surfactant having no hydroxyl group. When the content of the silicon-based nonionic surfactant is less than 10% by weight, the polyurethane resin foam becomes too brittle, the chipping or cracking occurs in the polishing layer, and the workability is remarkably deteriorated. In addition, the dressing property of the polyurethane resin becomes high, or the hydrophobicity of the polyurethane resin becomes too strong and the wettability with the slurry becomes poor, so the polishing rate tends to decrease. On the other hand, if it exceeds 20% by weight, the number of bubbles in the foam becomes too large, and it becomes difficult to increase the elastic modulus (hardness) of the polishing layer, and the planarization characteristics cannot be improved. .

  The polyurethane resin foam is preferably a reaction cured product of an isocyanate-terminated prepolymer containing the hydrophobic high molecular weight polyol and an isocyanate component, and a chain extender. A polyurethane resin foam obtained by the prepolymer method is preferable because of its excellent polishing characteristics.

  In the present invention, the hydrophobic high molecular weight polyol is preferably a polyester polyol in order to increase the cohesive strength of the polyurethane resin and ensure high rigidity. It is also a preferred embodiment that the hydrophobic high molecular weight polyol is polytetramethylene glycol.

  Moreover, it is preferable that the said isocyanate component is aromatic diisocyanate and alicyclic diisocyanate. Furthermore, the aromatic diisocyanate is preferably toluene diisocyanate and the alicyclic diisocyanate is preferably dicyclohexylmethane diisocyanate. When the above raw materials are used, not only the physical properties of the polyurethane resin foam can be easily adjusted, but also a polishing pad having excellent polishing properties can be obtained.

  In the present invention, the chain extender is preferably an aromatic diamine. By using an aromatic diamine as the chain extender, it becomes easy to adjust the curing time, the specific gravity, hardness, etc. of the polishing layer. The aromatic diamine is preferably a non-halogen aromatic diamine in consideration of environmental aspects and the like.

  The polyurethane resin foam preferably has a specific gravity of 0.65 to 0.86, more preferably 0.7 to 0.8. When the specific gravity is less than 0.65, the surface hardness of the polishing layer is lowered, the flatness of the object to be polished (wafer) is lowered, and the life characteristics tend to be deteriorated. On the other hand, when the specific gravity exceeds 0.86, the number of bubbles per unit area decreases and the polishing rate tends to decrease.

  The polyurethane resin foam preferably has an Asker D hardness of 50 to 65 degrees. When the Asker D hardness is less than 50 degrees, the flatness of the object to be polished decreases. When the Asker D hardness is greater than 65 degrees, the flatness is good, but the in-plane uniformity of the object to be polished tends to decrease. is there.

  The polyurethane resin foam preferably has a tensile strength of 15 to 25 MPa. When the tensile strength is less than 15 MPa, the planarization characteristics of the polishing pad tend to be reduced. On the other hand, when the tensile strength exceeds 25 MPa, scratches are likely to occur on the object to be polished (wafer).

  The polyurethane resin foam preferably has a tensile elongation at break of 25 to 100%. When the tensile elongation at break is less than 25%, the surface wear becomes unnecessarily large, and the life of the polishing pad is shortened. Tend to be. On the other hand, when it exceeds 100%, the flatness of the polishing object tends to be lowered.

Moreover, this invention mixes the 1st component containing an isocyanate terminal prepolymer, and the 2nd component containing a chain extender, it hardens | cures, and the manufacturing method of the polishing pad containing the process (1) which produces a polyurethane resin foam In
In the step (1), a silicon-based nonionic surfactant having no hydroxyl group is added to the first component containing the isocyanate-terminated prepolymer so as to be 10 to 20% by weight in the polyurethane resin foam. After preparing a bubble dispersion in which one component is stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles, a second component containing a chain extender is mixed in the bubble dispersion and cured. A high molecular weight polyol component, which is a raw material component of the isocyanate-terminated prepolymer, is a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850. The present invention relates to a manufacturing method and a polishing pad manufactured by the method.

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

  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 a polishing layer alone or a laminate of a polishing layer and another layer (for example, a cushion layer).

  The polyurethane resin foam contains at least an isocyanate component and a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850 as raw material components.

  The hydrophobic high molecular weight polyol does not have a hydrophilic group other than a hydroxyl group that reacts with an isocyanate group.

A hydrophilic group other than a hydroxyl group is a functional group or salt that generally contains an element such as oxygen, nitrogen, or sulfur. For example, —NH ₂ , —CONH ₂ , —NHCONH ₂ , —SH, —SO ₃ H _{, -OSO 3 H, - (CH} 2 CH 2 O) n -, - functional groups such as COOH, _-SO 3 M (M: an alkali _{metal), - OSO 3 M, -COOM} , -NR 3 X (R: And a salt such as an alkyl group, X: halogen).

  Examples of the hydrophobic high molecular weight polyol include hydroxy-terminated polyester polyol, polycarbonate polyol, polyester polycarbonate polyol, polyether polyol, polyether polycarbonate polyol, polyester amide, phenol resin polyol, epoxy polyol, polybutadiene polyol, and polyisoprene polyol. Can be mentioned.

  Examples of the polyester polyol include polypropylene adipate, polybutylene adipate, polyhexamethylene adipate, and polycaprolactone polyol.

  Examples of the polyether polyol include polyhexamethylene glycol (PHMG), polytetramethylene glycol (PTMG), and polypropylene glycol (PPG).

  Examples of the polyether polycarbonate polyol include diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, polypropylene glycol and / or polytetramethylene glycol, phosgene, diallyl carbonate (for example, diphenyl carbonate). ) Or a reaction product with a cyclic carbonate (for example, propylene carbonate).

  As the polyester polycarbonate polyol, a reaction product of a polyester glycol such as polycaprolactone polyol and alkylene carbonate, ethylene carbonate is reacted with polyhydric alcohol, and then the obtained reaction mixture is reacted with an organic dicarboxylic acid. The product etc. which become are illustrated.

  The hydrophobic high molecular weight polyol may be a single type of the above polyol or a combination of two or more types.

  In the present invention, the hydrophobic high molecular weight polyol is preferably a polyester polyol. In another preferred embodiment, the hydrophobic high molecular weight polyol is polytetramethylene glycol.

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

  As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.).

  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.

  In addition to the above-described hydrophobic high molecular weight polyol component, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-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-hexane Low molecular weight such as triol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, triethanolamine Polyol component, ethylenediamine, tolylenediamine, diphenylmethane diamine, can be used together low molecular weight polyamine component, such as diethylenetriamine, and the like. These low molecular weight polyol components and low molecular weight polyamine components may be used alone or in combination of two or more. The blending amount of the low molecular weight polyol component or the low molecular weight polyamine component is not particularly limited, and is appropriately determined depending on the characteristics required for the polishing pad (polishing layer) to be produced. The molecular weight of the low molecular weight polyol component or the low molecular weight polyamine component is less than 500, preferably 250 or less.

  When the polyurethane resin foam is produced by the 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. In particular, it is preferable to use a non-halogen aromatic polyamine.

  The ratio of the isocyanate component, hydrophobic high molecular weight polyol, and 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 hydrophobic high molecular weight polyol and the chain extender is 0.80 to 1.20. It is preferable that it is 0.99 to 1.15. When the number of isocyanate groups is less than 0.80, the required hardness tends not to be obtained. On the other hand, if it exceeds 1.20, curing failure due to unreacted isocyanate occurs, and the polishing characteristics tend to deteriorate.

  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.

  Polyurethane resin foam can be produced by either the prepolymer method or the one-shot method, but an isocyanate-terminated prepolymer is synthesized beforehand from an isocyanate component and a hydrophobic high molecular weight polyol, and a chain extender is added thereto. The prepolymer method to be reacted is preferable because the physical properties of the resulting polyurethane are excellent.

  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 hydrophobic high molecular weight polyol 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, L5340 (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 room 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 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, the raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.

  In this invention, it is preferable that the average cell diameter of the said polyurethane resin foam is 70 micrometers or less, More preferably, it is 30-60 micrometers. When deviating from this range, the planarity (flatness) of the polished object after polishing tends to decrease.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the object to be polished preferably has a surface shape that holds and renews the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and renewing the slurry. However, in order to more efficiently retain the slurry and renew the slurry, it is also a subject of polishing. In order to prevent destruction of the object to be polished due to adsorption with the object, it is preferable that the polishing surface has an uneven structure. The concavo-convex structure is not particularly limited as long as the shape 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 1.5 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 undulation, and there are portions where the contact state with the object 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 polishing object having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire polishing object. 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

(Average bubble diameter measurement)
A sample obtained by cutting the produced polyurethane resin foam in parallel with a razor blade as thin as possible to a thickness of 1 mm or less was used as an average cell diameter measurement sample. 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. . 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).

(Measurement of tensile elongation at break and tensile strength)
The produced polyurethane resin foam was punched in the shape of dumbbell No. 3 in accordance with JIS K7312-1996 to obtain a sample. The sample was trained for 24 hours at 22 ° C. and 66% RH, and then a tensile test was performed. Tensile break elongation and tensile strength were measured. As a tensile tester, an Instron universal tester (type 4300, manufactured by Instron) was used, and as a software, a video extensometer controlled by a series IX was used.

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as the polishing apparatus, the polishing rate was evaluated using the prepared polishing pad. The initial polishing rate was calculated from the time obtained by polishing only 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. Further, polishing was repeated in the same manner, and accumulated for 10 hours, and the polishing rate after 10 hours was measured. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.
The flatness was evaluated by depositing a thermal oxide film of 0.5 μm on an 8-inch silicon wafer, and then patterning L / S (line and space) = 25 μm / 5 μm and L / S = 5 μm / 25 μm. Then, 1 μm of an oxide film (TEOS) was further deposited to produce a patterned wafer with an initial step of 0.5 μm. This wafer was polished under the above-mentioned polishing conditions and evaluated by measuring the amount of scraping of the bottom portion of the 25 μm space when the global level difference was 2000 mm or less. It can be said that the flatness is better as the value is smaller.

(Measure the number of scratches)
An SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) was used as a polishing apparatus, and a thermal oxide film of 1 μm formed on an 8-inch silicon wafer was polished by about 0.5 μm using the manufactured polishing pad. As polishing conditions, silica slurry (SS12, manufactured by Cabot Corporation) was added as a polishing 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. After polishing, a wafer surface inspection apparatus (WM2500) manufactured by Topcon Corporation was used to measure how many streaks of 0.2 μm or more exist on the wafer.

Example 1
In a reaction vessel, 35 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20 manufactured by Mitsui Takeda Chemical Co., Ltd.), 15.75 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetra 44.3 parts by weight of methylene glycol (Mitsubishi Chemical Corporation, number average molecular weight 650) and 4.95 parts by weight of 1,3-butylene glycol (manufactured by Nakarai Co., Ltd.) were added, and the mixture was stirred and heated at 80 ° C. for 120 minutes. Prepolymer A (NCO wt%: 11.6 wt%) was obtained.
Then, 100 parts by weight of isocyanate-terminated prepolymer A and 20 parts by weight of silicon-based nonionic surfactant L5340 (manufactured by Nippon Unica) (13% by weight in polyurethane resin) were placed in the reaction vessel, and the temperature was adjusted to 80 ° C. Thereafter, vigorous stirring was performed for about 4 minutes using a stirring blade so that bubbles were taken into the reaction system at a rotation speed of 900 rpm. Thereto was added 34 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Iharacamine MT, manufactured by Ihara Chemical Co.) previously melted at 120 ° C. After stirring for about 1 minute, the reaction solution was poured into a pan-type open mold. When the fluidity of the reaction solution ceased, it was placed in an oven and post-cured at 110 ° C. for 6 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block was sliced using a band saw type slicer (manufactured by Fecken) to obtain a polyurethane resin foam sheet. Next, this sheet was subjected to surface buffing so as to have a predetermined thickness by using a buffing machine (manufactured by Amitech Co., Ltd.) to obtain a sheet with adjusted thickness accuracy (sheet thickness: 1.27 mm). The buffed sheet is punched into a predetermined diameter (61 cm), and a groove processing machine (manufactured by Toho Steel Machine Co., Ltd.) is used to form a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm. A concentric groove was processed to prepare a polishing layer. Thereafter, a cushioning material (cushion layer) in which a commercially available nonwoven fabric was impregnated with polyurethane was laminated on the back surface of the polishing layer to prepare a polishing pad.

Example 2
In Example 1, instead of 34 parts by weight of 4,4′-methylenebis (o-chloroaniline), Etacure 300 (manufactured by Albemarle, 3,5-bis (methylthio) -2,6-toluenediamine and 3,5 A polishing pad was prepared in the same manner as in Example 1 except that 28 parts by weight of a mixture of bis (methylthio) -2,4-toluenediamine) was used.

Example 3
A polishing pad was produced in the same manner as in Example 1, except that the silicon-based nonionic surfactant L5340 was changed from 20 parts by weight to 15 parts by weight.

Example 4
In a reaction vessel, 35 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20, manufactured by Mitsui Takeda Chemical Co., Ltd.), 15.75 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, adipic acid And 44.5 parts by weight of a polyester polyol (number average molecular weight 650) obtained by polycondensation with diethylene glycol at 150 ° C. and 4.95 parts by weight of 1,3-butylene glycol (manufactured by Nacalai Co., Ltd.) The mixture was heated and stirred for 120 minutes to obtain isocyanate-terminated prepolymer B (NCO wt%: 11.5 wt%).
In Example 1, a polishing pad was prepared in the same manner as in Example 1 except that 100 parts by weight of isocyanate-terminated prepolymer B was used instead of 100 parts by weight of isocyanate-terminated prepolymer A.

Comparative Example 1
A polishing pad was produced in the same manner as in Example 1 except that the silicon-based nonionic surfactant L5340 was changed from 20 parts by weight to 5 parts by weight in Example 1.

Comparative Example 2
A polishing pad was produced in the same manner as in Example 1, except that the silicon-based nonionic surfactant L5340 was changed from 20 parts by weight to 40 parts by weight.

Comparative Example 3
Toluene diisocyanate (Mitsui Takeda Chemical Co., Ltd., mixture of 2,4-isomer / 2,6-isomer = 80/20) 32.1 parts by weight in a reaction vessel, 4,4′-dicyclohexylmethane diisocyanate 8.5 parts by weight, 54.3 parts by weight of polytetramethylene glycol (manufactured by Mitsubishi Chemical Corporation, number average molecular weight 1000) and 4.9 parts by weight of 1,3-butylene glycol (manufactured by Nakarai Co., Ltd.) were added, and the mixture was heated and stirred at 80 ° C. for 120 minutes. An isocyanate-terminated prepolymer C (NCO wt%: 9.1 wt%) was obtained.
In Example 1, instead of 100 parts by weight of isocyanate-terminated prepolymer A, 100 parts by weight of isocyanate-terminated prepolymer C was used, except that 4,4′-methylenebis (o-chloroaniline) was changed from 34 parts by weight to 26 parts by weight. A polishing pad was produced in the same manner as in Example 1.

  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 clear from the results of Table 1, a hydrophobic non-molecular weight polyol having a number average molecular weight of 500 to 850 is used as the polyol component, and a silicon-based nonionic surfactant having no hydroxyl group is added to 10 to 10 in the polyurethane resin foam. By adding 20% by weight, a polishing pad having a high polishing rate and excellent planarization characteristics can be obtained. The polishing pad can also suppress the generation of scratches on the wafer.

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: Polishing object (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (15)

In a polishing pad having a polishing layer made of a polyurethane resin foam having fine bubbles, the high molecular weight polyol component which is a raw material component of the polyurethane resin foam is a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850, and The polyurethane resin foam contains 10 to 20% by weight of a silicon-based nonionic surfactant having no hydroxyl group. The polishing pad according to claim 1, wherein the polyurethane resin foam is a reaction cured product of an isocyanate-terminated prepolymer containing the hydrophobic high molecular weight polyol and an isocyanate component, and a chain extender. The polishing pad according to claim 1 or 2, wherein the hydrophobic high molecular weight polyol is a polyester polyol. The polishing pad according to claim 1 or 2, wherein the hydrophobic high molecular weight polyol is polytetramethylene glycol. The polishing pad according to any one of claims 2 to 4, wherein the isocyanate component is an aromatic diisocyanate and an alicyclic diisocyanate. The polishing pad according to claim 5, wherein the aromatic diisocyanate is toluene diisocyanate, and the alicyclic diisocyanate is dicyclohexylmethane diisocyanate. The polishing pad according to any one of claims 2 to 6, wherein the chain extender is an aromatic diamine. The polishing pad according to claim 7, wherein the aromatic diamine is a non-halogen aromatic diamine. The polishing pad according to claim 1, wherein the polyurethane resin foam has a specific gravity of 0.65 to 0.86. The polishing pad according to any one of claims 1 to 9, wherein the polyurethane resin foam has an Asker D hardness of 50 to 65 degrees. The polishing pad according to any one of claims 1 to 10, wherein the polyurethane resin foam has a tensile strength of 15 to 25 MPa. The polishing pad according to claim 1, wherein the polyurethane resin foam has a tensile elongation at break of 25 to 100%. In the method for producing a polishing pad comprising the step (1) of mixing a first component containing an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane resin foam,
In the step (1), a silicon-based nonionic surfactant having no hydroxyl group is added to the first component containing the isocyanate-terminated prepolymer so as to be 10 to 20% by weight in the polyurethane resin foam. After preparing a bubble dispersion in which one component is stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles, a second component containing a chain extender is mixed in the bubble dispersion and cured. A high molecular weight polyol component, which is a raw material component of the isocyanate-terminated prepolymer, is a hydrophobic high molecular weight polyol having a number average molecular weight of 500 to 850. Production method. A polishing pad manufactured by the method according to claim 13. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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