JP2017132012A - Manufacturing method for polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a polishing pad capable of suppressing occurrence of scratch, as well as improving a polishing speed.SOLUTION: A manufacturing method for a polishing pad comprises: a mechanical foaming step for preparing foam-dispersion urethane composition by a mechanical foaming method; and a curing step for curing the prepared composition to make a polyurethane foam. The mechanical foaming step comprises: a first agitation step for preparing a diphenylmethane diisocyanate-based compound including at least one type selected from a group of diphenylmethane diisocyanate and modified diphenylmethane diisocyanate, a toluene diisocyanate-based isocyanate-terminated prepolymer including a toluene diisocyanate as a raw material, a foam-dispersion isocyanate composition including surfactant having a hydroxy group; and a second agitation step for preparing the foam-dispersion isocyanate composition, and the foam dispersion urethane composition including an active hydrogen-containing compound.SELECTED DRAWING: Figure 1

Description

  The present invention is a polishing for flattening 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. The present invention relates to a method for manufacturing a pad.

  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 polishing rate can be improved by making the polishing layer a foam containing bubbles and increasing the amount of slurry retained (the polishing rate can be increased by making the polishing layer a foam containing bubbles and increasing the amount of slurry retained). For example, the following Patent Document 1).

Japanese Patent No. 3490431 JP 2013-144353 A JP 2006-320981 A

  The polishing rate of the conventional polishing pad is not sufficient. Therefore, it is conceivable to increase the elastic modulus of the polishing layer in order to further improve the polishing rate (for example, Patent Document 2). However, when the elastic modulus of the polishing layer is increased, the polishing rate can be improved, but there is a problem that scratches (scratches) are likely to occur on the surface to be polished of the object to be polished. On the other hand, when the polishing layer is simply made to have a low elastic modulus like the polishing pad described in Patent Document 3, the polishing rate is lowered.

  That is, with the conventional polishing pad, it is difficult to improve the polishing rate while suppressing the generation of scratches.

  An object of this invention is to provide the manufacturing method of the polishing pad which can improve polishing rate, suppressing generation | occurrence | production of a scratch.

  The polishing pad manufacturing method of the present invention includes a mechanical foaming step of preparing a cell-dispersed urethane composition by a mechanical foaming method, and a curing step of producing a polyurethane foam by curing the cell-dispersed urethane composition. A diphenylmethane diisocyanate-based compound in which the mechanical foaming step is at least one selected from the group consisting of diphenylmethane diisocyanate and modified diphenylmethane diisocyanate, a toluene diisocyanate-based isocyanate-terminated prepolymer containing toluene diisocyanate as a raw material, And a first stirring step for preparing a cell-dispersed isocyanate composition containing a surfactant having a hydroxyl group, and the cell containing the cell-dispersed isocyanate composition and the active hydrogen-containing compound A second agitation step of preparing a dispersion urethane composition.

  According to the polishing pad manufacturing method of the present invention, it is possible to manufacture a polishing pad capable of improving the polishing rate while suppressing the generation of scratches. The reason why the manufacturing method of the polishing pad of the present invention has such an effect is not clear, but is considered as follows.

  Diphenylmethane diisocyanate compounds are more reactive with active hydrogen-containing compounds than toluene diisocyanate isocyanate-terminated prepolymers. In the first stirring step, the reaction between the isocyanate group of the diphenylmethane diisocyanate compound and the hydroxyl group of the surfactant rather than the reaction between the isocyanate group of the toluene diisocyanate-based isocyanate-terminated prepolymer and the hydroxyl group of the surfactant. Therefore, the diphenylmethane diisocyanate compound gathers around the hydroxyl group of the surfactant present around the bubbles formed by the mechanical foaming method, and the hydroxyl group of the surfactant and the isocyanate group of the diphenylmethane diisocyanate compound are collected. It is thought to react. Thereafter, when the active hydrogen-containing compound is added and mixed in the second stirring step, the isocyanate group of the toluene diisocyanate-based isocyanate-terminated prepolymer reacts with the active hydrogen group of the active hydrogen-containing compound in the curing step. The polyurethane containing a large amount of the diphenylmethane diisocyanate compound as a constituent unit has a higher hardness than the polyurethane containing a large amount of the toluene diisocyanate isocyanate-terminated prepolymer as a constituent unit. While the matrix is low in hardness, a high-hardness polishing pad can be produced around the bubbles containing a large amount of the diphenylmethane diisocyanate compound as a constituent unit. The polishing pad obtained by the manufacturing method of the polishing pad of the present invention has a low hardness as a whole, so that it is difficult to scratch the surface of the material to be polished. The polishing rate is superior to a polishing pad obtained by a foaming method or a chemical foaming method. Therefore, according to the polishing pad manufacturing method of the present invention, it is considered that a polishing pad capable of improving the polishing rate while suppressing the generation of scratches can be manufactured.

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

  The polishing pad manufacturing method of the present embodiment includes a mechanical foaming step of preparing a cell-dispersed urethane composition by a mechanical foaming method, and a polishing step including a curing step of producing a polyurethane foam by curing the cell-dispersed urethane composition. A method for producing a pad, wherein the mechanical foaming step is at least one selected from the group consisting of diphenylmethane diisocyanate and modified diphenylmethane diisocyanate (hereinafter, diphenylmethane diisocyanate compound is also referred to as MDI, diphenylmethane diisocyanate compound) Is also referred to as an MDI compound), a toluene diisocyanate-based isocyanate-terminated prepolymer containing toluene diisocyanate as a raw material (hereinafter referred to as toluene diisocyanate as TDI). And a first stirring step of preparing a cell-dispersed isocyanate composition containing a surfactant having a hydroxyl group, and the cell-dispersed isocyanate composition, and a toluene diisocyanate-based isocyanate-terminated prepolymer) A second stirring step of preparing the cell-dispersed urethane composition containing an active hydrogen-containing compound.

<Mechanical foaming process>
The mechanical foaming step is a step of preparing a cell-dispersed urethane composition by a mechanical foaming method. The manufacturing method of the polishing pad of this embodiment uses a mechanical foaming method for the preparation of a cell-dispersed urethane composition from the viewpoint of suppressing the occurrence of scratches and improving the polishing rate. The mechanical foaming method does not use a different kind of material such as a chemically reactive foaming agent such as water or a vaporizing and expanding foaming agent such as chlorofluorocarbon, a fine hollow foam, or a solvent-soluble substance, and has uniform fine bubbles, and This is a method for producing a polyurethane foam having a hardness higher than that of the same density. For example, in Patent Document 1, Japanese Patent No. 3490431, Japanese Patent Application Laid-Open No. 2008-307683, Japanese Patent Application Laid-Open No. 2011-235418, etc. It is disclosed. In the production of a polyurethane foam by the mechanical foaming method, it is necessary to take pores (bubbles) into the polyurethane resin, and further, it is manufactured by a melting method in consideration of cost, work environment and the like. In the polishing pad manufacturing method of this embodiment, a polyurethane foam is manufactured by a mechanical foaming method using a surfactant having a hydroxyl group.

  The mechanical foaming step is a first stirring for preparing a cell-dispersed isocyanate composition containing an MDI compound, a TDI prepolymer, and a surfactant having a hydroxyl group from the viewpoint of suppressing generation of scratches and improving the polishing rate. A step and a second stirring step containing the cell-dispersed isocyanate composition and the active hydrogen-containing compound.

[First stirring step]
[Bubble-dispersed isocyanate composition]
The cell-dispersed isocyanate composition contains an MDI compound, a TDI prepolymer, and a surfactant having a hydroxyl group from the viewpoint of suppressing generation of scratches and improving the polishing rate.

(MDI compounds)
The MDI compound is at least one selected from the group consisting of MDI and modified MDI. The MDI compounds include 2,2′-MDI, 2,4′-MDI, 4,4′-MDI, polymeric MDI, uretonimine modified MDI, urethane modified MDI, isocyanurate modified MDI, acylurea diisocyanate, and carbodiimide. Examples thereof include at least one selected from the group consisting of modified MDI (for example, trade name Millionate MTL, manufactured by Nippon Polyurethane Industry). Among these, 4,4′-MDI is preferable from the viewpoint of suppressing generation of scratches and improving the polishing rate, and carbodiimide-modified 4,4′-MDI is more preferable.

  The NCO weight percent of the MDI compound is preferably 15 to 40 weight percent and more preferably 25 to 35 weight percent from the viewpoint of suppressing the occurrence of scratches and improving the polishing rate.

(TDI-based prepolymer)
The TDI prepolymer contains at least TDI and a high molecular weight polyol component as raw material components.

  The TDI is at least one selected from the group consisting of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate.

  The TDI prepolymer may contain an isocyanate component other than TDI as a raw material component as long as the effects of the present embodiment are not impaired. As isocyanate components other than the TDI, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, aromatic diisocyanates such as p-xylylene diisocyanate and m-xylylene diisocyanate, aliphatic diisocyanates such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and 1,6-hexamethylene diisocyanate, 1,4- Such as cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, etc. Cyclic diisocyanates, Desmodur -N (Bayer) and Duranate ™ (Asahi Kasei Kogyo) a polyfunctional polyisocyanate compound of three or more functional groups is a diisocyanate adduct compounds such like. However, since the reaction rate of the TDI prepolymer with respect to the hydroxyl group of the surfactant needs to be slower than the reaction rate of the MDI or the like with respect to the active hydrogen-containing compound, In the isocyanate component contained as a raw material component in the prepolymer, the content of TDI is preferably 50 mol% or more, and more preferably 70 mol% or more.

  As the high molecular weight polyol component, those usually used in the technical field of polyurethane can be used. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol, obtained by reacting ethylene carbonate with polyhydric alcohol, and then reacting the resulting reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more.

  The number average molecular weight of these high molecular weight polyol components is not particularly limited, but is preferably about 500 to 5,000 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, the polyurethane resin obtained by using the polyurethane resin does not have sufficient elastic properties and tends to be a brittle polymer, the polishing pad made of this polyurethane resin becomes too hard, May cause scratches. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the life of the polishing pad. On the other hand, when the number average molecular weight exceeds 5000, a polishing pad made of a polyurethane resin obtained using the number average molecular weight becomes soft, and it is difficult to obtain a sufficiently satisfactory planarity, which is not preferable.

  In addition to the high molecular weight polyol component, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, , 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-tetrakis (hydroxy) Chill) 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 TDI-based prepolymer uses the high molecular weight polyol component or the like and the TDI, and an equivalent ratio (NCO / H ^* ) of the active hydrogen (H ^* ) of the isocyanate group (NCO) of the TDI and the high molecular weight polyol component or the like ^. ) Is 1.2 to 5.0, preferably 1.6 to 2.6. When the equivalent ratio (NCO / H ^* ) of the isocyanate group (NCO) of the TDI to the active hydrogen (H ^* ) such as the high molecular weight polyol component is less than 1.2, the prepolymer is increased in molecular weight during synthesis. There is a tendency to solidify or gel. When the equivalent ratio (NCO / H ^* ) of the isocyanate group (NCO) of the TDI to the active hydrogen (H ^* ) such as the high molecular weight polyol component exceeds 5.0, a large amount of unreacted isocyanate remains. Therefore, the reaction with the active hydrogen-containing compound is accelerated, and the molding processability of the polyurethane resin foam tends to deteriorate.

  The NDI wt% of the TDI prepolymer is preferably 4.5 to 8.5 wt%, more preferably 6.5 to 8.2 wt% from the viewpoint of suppressing the occurrence of scratches and improving the polishing rate.

(Surfactant having a hydroxyl group)
The surfactant having a hydroxyl group is preferably a silicone surfactant having a hydroxyl group from the viewpoint of producing a polyurethane foam having uniform cells. Examples of the silicone surfactant having a hydroxyl group include SZ1718 (manufactured by Toray Dow Corning), L5420 (manufactured by Toray Dow Corning), SRX295 (manufactured by Toray Dow Corning), Tegostarb B8465 (manufactured by Evonik Japan), and the like. .

  The hydroxyl value of the surfactant having a hydroxyl group is preferably from 30 to 300 mgKOH / g, more preferably from 80 to 200 mgKOH / g, from the viewpoint of suppressing the occurrence of scratches and improving the polishing rate.

  In the first stirring step, the cell-dispersed isocyanate composition is a non-reactive MDI compound, a TDI prepolymer, and a surfactant having a hydroxyl group from the viewpoint of suppressing the generation of scratches and improving the polishing rate. Mechanical stirring is performed in the presence of gas, and the non-reactive gas is dispersed as fine bubbles to obtain a cell-dispersed isocyanate composition.

  The non-reactive gas is preferably a non-flammable gas, specifically, nitrogen, oxygen, carbon dioxide gas, rare gases such as helium and argon, and mixed gases thereof are exemplified, and air that has been dried to remove moisture Is most preferable in terms of cost.

  The blending amount of the surfactant having a hydroxyl group is preferably 1 to 8% by weight and more preferably 1.5 to 4% by weight in the foam-dispersed urethane composition from the viewpoint of foamability. preferable.

  The ratio of the blending amount of the MDI compound to the blending amount of the surfactant having a hydroxyl group (the blending amount of the MDI compound / the blending amount of the surfactant having a hydroxyl group) is a viewpoint of suppressing generation of scratches, and From the viewpoint of improving the polishing rate, 0.8 to 5 is preferable, and 1.0 to 3.0 is more preferable.

  The blending amount of the TDI prepolymer is preferably 10 to 100 parts by weight and more preferably 20 to 50 parts by weight with respect to 1 part by weight of the MDI compound from the viewpoint of suppressing the occurrence of scratches and improving the polishing rate. preferable.

  If necessary, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added.

  The order of addition of the MDI compound, the TDI prepolymer, the surfactant having a hydroxyl group, and the like is not limited.

  The stirring time in the first stirring step is preferably 1 to 30 minutes and more preferably 2 to 10 minutes from the viewpoint of reacting the MDI compound and the surfactant having a hydroxyl group in the cell-dispersed urethane composition. .

[Second stirring step]
In the second stirring step, the active hydrogen-containing compound is added to the cell-dispersed isocyanate composition obtained in the first stirring step, mechanically stirred in the presence of a non-reactive gas, and the non-reactive gas is converted into fine bubbles. To obtain the cell-dispersed urethane composition.

[Active hydrogen-containing compounds]
Examples of the active hydrogen-containing compound include those usually used in the technical field of polyurethane, such as a high molecular weight polyol, a low molecular weight polyol, a low molecular weight polyamine, an alcohol amine, and a chain extender. However, the surfactant having a hydroxyl group is not included in the active hydrogen-containing compound.

  Examples of the high molecular weight polyol which is the active hydrogen-containing compound include the same high molecular weight polyols used as a raw material for the TDI prepolymer.

  Examples of the low molecular weight polyol that is the active hydrogen-containing compound include those similar to the low molecular weight polyol used as a raw material for the TDI prepolymer.

  Examples of the low molecular weight polyamine that is the active hydrogen-containing compound include the same as the low molecular weight polyamine used as a raw material for the TDI prepolymer.

  Examples of the alcohol amine that is the active hydrogen-containing compound include the same alcohol amine used as a raw material of the TDI 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 Polyamines exemplified by diamine, N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, and p-xylylenediamine, or the low molecular weight polyols and low molecular weight polyamines described above. Can be mentioned. These may be used alone or in combination of two or more.

  The ratio of the MDI compound and the isocyanate compound such as the TDI prepolymer and the active hydrogen-containing compound in the cell-dispersed urethane composition can be variously changed according to the molecular weight of each and the desired physical properties of the polishing pad produced therefrom. In order to obtain a polishing pad having desired polishing characteristics, an isocyanate compound in the cell-dispersed urethane composition with respect to the total number of functional groups of the active hydrogen group of the active hydrogen-containing compound and the active hydrogen group of the surfactant having a hydroxyl group The number of isocyanate groups is preferably in the range of 0.95 to 1.15, more preferably 0.99 to 1.10.

  If necessary, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added. Moreover, you may add the catalyst which accelerates | stimulates well-known polyurethane reactions, such as a tertiary amine type | system | group. The order of adding the active hydrogen-containing compound is not limited.

  The stirring time in the second stirring step is not particularly limited, but is generally preferably 30 to 90 seconds.

  As the stirring device for dispersing the non-reactive gas in the form of fine bubbles in the mechanical foaming step, a known stirring device can be used without any particular limitation. Specifically, a homogenizer, a dissolver, a two-axis planetary mixer (Planetary mixer) and the like are exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but the use of a whipper type stirring blade is preferable because fine bubbles can be obtained.

  In addition, it is also a preferable aspect that the stirring in the first stirring step and the stirring in the second stirring step use different stirring devices. In particular, the agitation in the second agitation step may not be agitation that forms bubbles, and it is preferable to use an agitation 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 for the stirring device of the first stirring step and the second stirring step, and the stirring conditions are adjusted as necessary to adjust the stirring speed. It is also suitable to do.

<Curing process>
In the curing step, a polyurethane foam is produced by curing the cell-dispersed urethane composition.

  It is extremely preferable to heat and post-cure the polyurethane foam reacted until the cell-dispersed urethane composition is poured into the mold and no longer flows, because the physical properties of the foam are improved. The post-cure temperature needs to be higher than the activation temperature of the temperature-sensitive catalyst to be used, and is usually about 80 to 120 ° C.

<Polishing layer forming step>
The polishing layer may be manufactured by pouring the foam-dispersed urethane composition into a mold having a predetermined size in the curing step to produce a polyurethane foam block, and slicing the block using a slicer, or The polishing layer may be manufactured by processing into a thin sheet at the stage of pouring into the mold. As an example, a polishing layer forming step for producing a polyurethane foam sheet (polishing layer) from a polyurethane foam will be described below.

  The said polishing layer formation process is a process of producing a polyurethane foam sheet (polishing layer) from the polyurethane foam obtained at the said hardening process. A method for producing a polyurethane foam sheet from a polyurethane foam is not particularly limited, but examples include a method for producing a polyurethane foam sheet by cutting a polyurethane foam into a predetermined thickness using a band saw type or canna type slicer. it can.

  The thickness variation of the polyurethane foam sheet is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large waviness, and there are portions where the contact state with the material to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with a dresser in which diamond abrasive grains are electrodeposited and fused in the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.

  Examples of the method for suppressing the variation in the thickness of the polyurethane foam sheet include a method of buffing the sheet surface sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

  Although the thickness of the said polyurethane foam sheet is not specifically limited, Usually, it is about 0.8-4 mm, and it is preferable that it is 1.0-2.5 mm.

  It is preferable that the average cell diameter of the said polyurethane foam sheet is 20-70 micrometers, More preferably, it is 30-60 micrometers.

  The specific gravity of the polyurethane foam is preferably 0.7 to 0.85, more preferably 0.73 to 0.80. When the specific gravity is less than 0.7, the durability of the polishing layer tends to decrease. On the other hand, when it is larger than 0.85, the abrasive retention of bubbles is deteriorated and the polishing rate tends to decrease.

  The Asker D hardness of the polyurethane foam is preferably 30 to 48 degrees, and more preferably 35 to 45 degrees. When the Asker D hardness is less than 30 degrees, the polishing rate tends to decrease or the surface smoothness of the polished material after polishing tends to deteriorate. On the other hand, when it is larger than 48 degrees, scratches are likely to occur on the surface of the material to be polished.

  The polishing surface of the polyurethane foam sheet (polishing layer) that comes into contact with the material to be polished preferably 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. 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, or pressing a resin with a press plate having a predetermined surface shape. Examples thereof include a method, a manufacturing method using photolithography, and a manufacturing method using laser light using a carbon dioxide gas laser.

  The polishing pad of this embodiment may be a laminate of the polishing layer and the cushion layer.

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

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

  As a means for bonding the polishing layer and the cushion layer, for example, a method in which the polishing layer and the cushion layer are sandwiched and pressed with a double-sided tape can be mentioned.

  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 slurry from penetrating into the cushion layer, 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 layer may be different, the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force of each layer can be optimized.

  The polishing pad of this embodiment 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.

<Measurement and evaluation method>
[Measurement of specific gravity]
This was performed according to JIS Z8807-1976. The produced polyurethane foam sheet was cut into a 4 cm x 8.5 cm strip (thickness: arbitrary) and used as a specific gravity measurement sample. I put it. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

[D hardness measurement]
This was performed in accordance with JIS K6253-1997. The produced polyurethane foam sheet 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).

[Polishing rate and scratch]
[Polishing conditions]
The polishing pad was attached to a polishing apparatus (manufactured by MAT, model number: ARW-8C1A), and the oxide film wafer was polished. The polishing conditions are as follows.
Polishing pressure: 4.5 psi
Retainer pressure: 5.0 psi
Polishing head rotation speed: 90 rpm
Platen rotation speed: 93rpm
Slurry: SS25 (manufactured by Cabot) was diluted twice with ultrapure water, the slurry flow rate was 120 ml / min, and the polishing time was 1 min.
Dressing condition: The dresser used was DK45 manufactured by Saesol, and was polished while applying an in-situ dressing process at a load of 4.8 lbf and a rotation speed of 63 rpm.
As a polishing operation, after attaching the polishing pad to the apparatus surface plate, the pad surface was dressed for 30 minutes under the above-mentioned dresser conditions while flowing ultrapure water. Then, after eight dummy wafers were flowed, one polishing rate monitor wafer and one scratch monitor wafer were polished.

[Evaluation of polishing rate]
The polishing rate was calculated from the polishing amount at this time by polishing a wafer obtained by forming a 10,000-mm tungsten film on an 8-inch silicon wafer for 60 seconds. An optical interference film thickness measuring device (manufactured by Nanometrics, device name: Nanospec) was used for measuring the thickness of the oxide film.

[Scratch evaluation]
The scratch was evaluated by measuring the number of streaks of 0.19 μm or more on the polished wafer using a defect evaluation apparatus (Surfscan SP1) manufactured by KLA Tencor.

<Example 1>
In a container, toluene diisocyanate (Mitsui Chemicals product name: Cosmonate T80) 27.2 parts by weight, isophorone diisocyanate (Evonik Japan product name: VEST ANAT IPDI) 6.1 parts by weight, polytetramethylene ether glycol having an average molecular weight of 1000 (Mitsubishi Chemical product name: (PTMG1000) 64.4 parts by weight and 1,4 butanediol (manufactured by Nacalai Tesque) 2.3 parts by weight were added and reacted at 70 ° C. for 4 hours to obtain a TDI prepolymer. The NCO% was 7.9%.

  100 parts by weight of the prepolymer heated at 60 ° C., 5 parts of MDI-modified isocyanate (Tosoh product name: Millionate MTL NCO: 29%) and silicone foam stabilizer (Evonik Japan product name: Tegostarb B8465 terminal OH-containing product OHV: 110 mgKOH / g) 3 parts by weight was blended in the polymerization vessel. Then, it stirred violently for 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. Thereafter, 28.3 parts by weight of MOCA (Ihara Chemical Co., Ltd., Cuamine MT) whose temperature was adjusted to 120 ° C. was added and stirred for 1 minute. Then, it was poured into an open mold (casting container). When the fluidity of this mixed solution disappeared, it was put 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 (manufactured by Amitech Co., Ltd.), it is sequentially cut with # 120, # 240 and # 400 sand peppers, and the surface of the sheet is buffed until the thickness becomes 2 mm. And it was set as the sheet | seat which prepared the thickness precision. The buffed sheet is punched out with a diameter of 508 mm, and a concentric circle having a groove width of 0.40 mm, a groove pitch of 3.1 mm, and a groove depth of 0.8 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to produce a polishing layer. A double tack tape (Sekisui Chemical Co., Ltd. product name: 5882W) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Further, the surface of the cushion layer (Toray Industries, polyethylene foam, Torepefu, thickness 1.27 mm) subjected to corona treatment was buffed and bonded to the double tack tape using a laminator. Further, a surface plate tape (442M made by 3M) was bonded to the other side of the cushion layer using a laminator to prepare a polishing pad. The density of the polishing layer was 0.75, and the D hardness was 43 (60 sec value).

<Example 2>
In Example 1, a polishing pad was prepared in the same manner as in Example 1 except that 7 parts by weight of MDI-modified isocyanate was mixed with 100 parts by weight of the TDI-based prepolymer and 30.2 parts by weight of MOCA was mixed. The polishing layer had a density of 0.74 and a D hardness of 45 (60 sec value).

<Example 3>
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that 3 parts by weight of MDI-modified isocyanate was mixed with 100 parts by weight of the TDI-based prepolymer and 26.5 parts by weight of MOCA was mixed. The density of the polishing layer was 0.76, and the D hardness was 42 (60 sec value).

<Example 4>
A polishing pad was produced in the same manner as in Example 1, except that the MDI to be added was changed to monomeric MDI (Tosoh product name: Millionate MT NCO: 32%). The density of the polishing layer was 0.73, and the D hardness was 44 (60 sec value).

<Comparative Example 1>
In Example 1, a polishing pad was prepared in the same manner as in Example 1 except that 23.8 parts by weight of MOCA was added without adding MDI-modified isocyanate. The density of the polishing layer was 0.69, and the D hardness was 29.

  The evaluation results of Examples 1 to 4 and Comparative Example 1 are shown in Table 1 below.

In Examples 1 to 3 to which MDI-modified isocyanate was added and Example 4 to which monomeric MDI was added, the polishing rate was high and the number of defects was small. On the other hand, in the comparative example in which no MDI-based isocyanate was added, the polishing rate was low and the number of defects was increased.

Claims (7)

A method for producing a polishing pad comprising a mechanical foaming step of preparing a cell-dispersed urethane composition by a mechanical foaming method, and a curing step of producing a polyurethane foam by curing the cell-dispersed urethane composition,
The mechanical foaming step is at least one selected from the group consisting of diphenylmethane diisocyanate and modified diphenylmethane diisocyanate, a diphenylmethane diisocyanate compound, a toluene diisocyanate isocyanate prepolymer containing toluene diisocyanate as a raw material, and a surfactant having a hydroxyl group Of a polishing pad having a first stirring step of preparing a cell-dispersed isocyanate composition containing, and a second stirring step of preparing the cell-dispersed isocyanate composition and the cell-dispersed urethane composition containing an active hydrogen-containing compound Production method.   The reaction rate between the isocyanate group of the diphenylmethane diisocyanate compound and the active hydrogen group of the active hydrogen-containing compound is the reaction rate of the isocyanate group of the toluene diisocyanate-based isocyanate-terminated prepolymer and the active hydrogen group of the active hydrogen-containing compound. The method for producing a polishing pad according to claim 1, wherein the method is higher than the speed.   The method for producing a polishing pad according to claim 1, wherein the surfactant is not included in the active hydrogen-containing compound.   The method for producing a polishing pad according to any one of claims 1 to 3, wherein the diphenylmethane diisocyanate compound has an NCO wt% of 15 to 40 wt% and a hydroxyl value of the surfactant of 30 to 300 mgKOH / g. .   The method for producing a polishing pad according to any one of claims 1 to 4, wherein a compounding amount of the toluene diisocyanate-based isocyanate-terminated prepolymer is 10 to 100 parts by weight with respect to 1 part by weight of the diphenylmethane diisocyanate-based compound.   The method for producing a polishing pad according to any one of claims 1 to 5, wherein the toluene diisocyanate-based isocyanate-terminated prepolymer has an NCO wt% of 4.5 to 8.5 wt%. The method for producing a polishing pad according to any one of claims 1 to 6, wherein the stirring time in the first stirring step is 1 to 30 minutes.

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