JP2007262213A - Removable adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removable adhesive sheet having little contamination due to transfer to the semiconductor wafer which is an adherend when releasing the sheet after attaching the sheet once and useful as a protective sheet in polishing step of the semiconductor wafer and an adhesive sheet for wafer retention in dicing step. <P>SOLUTION: The removable adhesive sheet has an adhesive layer (layer B) on at least one side of a substrate film (layer A) and the layer A and the layer B each comprise (meth)acrylic acid alkyl ester copolymer as a main component or the removable adhesive sheet has an adhesive layer (layer B) on at least one side of a substrate film (layer A) and has a mold release film (layer C) which is a surface layer of the layer B on the side opposite to the layer A, and the layer B and the layer C each comprise a (meth)acrylate copolymer as a main component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a re-peeling useful as a protective sheet in a polishing process of a semiconductor wafer or a pressure-sensitive adhesive sheet for holding a wafer in a dicing process, which is less contaminated by transfer to a semiconductor wafer as an adherend when it is peeled off after being attached once. The present invention relates to a pressure-sensitive adhesive sheet.

  Conventionally, various pressure-sensitive adhesive sheets are used in semiconductor manufacturing processes. In particular, the surface protective sheet used in the backside polishing (back grinding) process of semiconductor wafers, the holding sheet used in the cutting and separating (dicing) process into element pieces, etc. are peeled off after the predetermined process is completed after being attached. A “removable” pressure-sensitive adhesive sheet is used.

  The re-peelable pressure-sensitive adhesive sheet exhibits sufficient adhesion in the processing step, but in the peeling step, it can be easily peeled off, and an organic substance such as a pressure-sensitive adhesive is transferred to the semiconductor wafer as the adherend ( A characteristic that does not cause transfer contamination is required. In particular, transfer contaminants cause wire bonding defects and package cracks, and in particular, with the recent miniaturization of wiring and miniaturization of packages, the demand for reduction of transfer contaminants has become more severe. ing.

  As a method for reducing contamination due to transfer, there is a method for reducing the transfer of adhesive (referred to as adhesive residue) at the time of peeling by controlling the adhesive strength of the adhesive layer made of alkyl acrylate ester within a certain range. (For example, see Patent Document 1 and Patent Document 2).

  However, as described above, the contamination due to the transfer is not caused only by the adhesive residue due to the adhesive force of the adhesive itself at the time of peeling. Another cause of transfer contamination is the precipitation of low molecular weight components contained in the acrylic resin and unreacted crosslinking agent on the surface. The acrylic resin used as the binder for the pressure-sensitive adhesive contains a certain amount of a low molecular weight component (referred to as a component having a weight average molecular weight of 100,000 or less). In addition, a crosslinking agent is usually added to the pressure-sensitive adhesive composition in order to adjust the adhesive strength and to suppress the above adhesive residue. However, these crosslinking agents do not react completely in the crosslinking reaction, and a certain amount of the crosslinking agent component remains unreacted in the pressure-sensitive adhesive layer. These low molecular weight components and unreacted crosslinking agent components diffuse in the pressure-sensitive adhesive layer and precipitate or bleed at the interface between the pressure-sensitive adhesive and the wafer. This is transferred to the wafer side surface when the adhesive sheet is peeled off, which causes transfer contamination.

  For these, the adhesive residue, which is the transfer of the adhesive itself, has different generation factors. Therefore, the technique for suppressing the adhesive residue cannot be solved at all. Because of the agent, contamination can be exacerbated. Moreover, in order to refine | purify the low molecular weight component in an acrylic resin, the problem of a production efficiency fall or a cost increase arises. That is, there are still many problems regarding transfer contamination.

  On the other hand, a pressure-sensitive adhesive sheet using a base film made of a multilayer resin particle made of a thermoplastic resin and an acrylic resin is known (for example, see Patent Document 3). However, in this, there is no mention of transfer contamination, and no effective improvement means is shown.

JP 11-315259 A Japanese Patent Laid-Open No. 2002-80804 JP 2004-79916 A

  An object of the present invention is to provide an excellent adhesive sheet for re-peeling in which transfer of a low molecular weight component or an unreacted crosslinker component to a semiconductor wafer is suppressed and trouble caused by contamination does not occur.

  As a result of intensive studies to achieve the above object, the present inventors have found that the use of the same type of resin as the adhesive as the base material reduces the amount of the crosslinking agent component deposited on the surface of the semiconductor wafer. Was completed.

  That is, the present invention is an adhesive sheet having an adhesive layer (B layer) on at least one side of a base film (A layer), and both the A layer and the B layer are co-polymerized with (meth) acrylic acid alkyl ester. A re-peeling pressure-sensitive adhesive sheet characterized by comprising a coalescence as a main component.

  Furthermore, this invention provides said adhesive sheet for re-peeling wound up in roll shape so that the surface of the exposed A layer and B layer may contact | connect.

  Moreover, this invention has an adhesive layer (B layer) on at least one side of a base film (A layer), and is a surface layer of B layer, Comprising: A mold release film (C layer) is provided on the opposite side to A layer. Provided is a pressure-sensitive adhesive sheet for re-peeling, wherein both the B layer and the C layer are mainly composed of a (meth) acrylic acid alkyl ester copolymer.

  Furthermore, this invention has an adhesive layer (B layer) on at least one side of a base film (A layer), and is a surface layer of B layer, Comprising: A release film (C layer) on the opposite side to A layer The pressure-sensitive adhesive sheet has a re-peeling pressure-sensitive adhesive sheet in which all of the A layer, the B layer, and the C layer are mainly composed of a (meth) acrylic acid alkyl ester copolymer.

  Furthermore, the present invention provides a re-peeling pressure-sensitive adhesive sheet in which the amount of organic contamination transferred to a silicon wafer after being applied to and peeled from a silicon wafer is less than 10% in terms of carbon in terms of surface element ratio.

  Furthermore, this invention provides the processing method of a semiconductor wafer using said adhesive sheet for re-peeling.

  The pressure-sensitive adhesive sheet for re-peeling of the present invention can reduce process trouble and improve productivity because there are few low molecular weight components and unreacted cross-linking agent components transferred to the surface of a semiconductor wafer as an adherend after re-peeling. This is industrially beneficial.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are schematic cross-sectional views each showing an example of the re-peeling pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive sheet 1 for re-peeling shown in FIG. 1 (in the case of a two-layer structure without a release film) is provided with a pressure-sensitive adhesive layer 3 (B layer) on one side of a base film 2 (A layer). Yes. The re-peeling pressure-sensitive adhesive sheet 4 shown in FIG. 2 (in the case of a three-layer structure provided with a release film) has a pressure-sensitive adhesive layer 3 (B layer) and a release layer on one side of the base film 2 (A layer). A mold film 5 (C layer) is provided. The re-peeling pressure-sensitive adhesive sheet wound up in the form of a roll shown in FIG. 3 is obtained by winding the re-peeling pressure-sensitive adhesive sheet 1 shown in FIG. is there.

  In order to exert the effect of the present invention, the pressure-sensitive adhesive sheet for re-peeling of the present invention has at least one surface of a pressure-sensitive adhesive layer (referred to as B layer) mainly composed of a (meth) acrylic acid alkyl ester copolymer. It is necessary to have the film layer which has a (meth) acrylic-acid alkylester copolymer as a main component. The film layer containing a (meth) acrylic acid alkyl ester copolymer as a main component may be a base film (referred to as A layer) or a release film (referred to as C layer). That is, the re-peeling pressure-sensitive adhesive sheet of the present invention must have at least one of the following two forms.

  First, one embodiment of the present invention is a case where the A layer is mainly composed of a (meth) acrylic acid alkyl ester copolymer. In this case, the peelable pressure-sensitive adhesive sheet of the present invention may have a two-layer configuration of A layer / B layer having a B layer on at least one side of the A layer, or A layer / B layer / C layer provided with a release film. It may be a three-layer structure. When the A layer contains a (meth) acrylic acid alkyl ester copolymer as a main component, the polymer of the C layer is not particularly limited.

  Another embodiment of the present invention is a case where the C layer is mainly composed of a (meth) acrylic acid alkyl ester copolymer. In this case, the pressure-sensitive adhesive sheet for re-peeling of the present invention must have a three-layer structure of A layer / B layer / C layer having a C layer on the surface layer opposite to the A layer of the B layer. When the C layer is mainly composed of a (meth) acrylic acid alkyl ester copolymer, the polymer of the A layer is not particularly limited.

  Among the above, from the viewpoint of suppressing transfer contamination, the most preferable form is that the A layer / B layer / C are all composed of a (meth) acrylic acid alkyl ester copolymer as the main component. This is a case of a three-layer structure.

  As used herein, “main component” means that the content in the layer is 80% by weight or more, preferably 90% by weight or more, and most preferably 95% by weight or more. The (meth) acrylic acid alkyl ester is a general term for an acrylic acid alkyl ester and a methacrylic acid alkyl ester.

  In the present invention, an effect is exhibited when a film layer made of a (meth) acrylic acid alkyl ester copolymer is in contact with at least one side of the B layer. This effect is considered to be manifested by the low molecular weight component remaining in the B layer and the unreacted cross-linking agent (hereinafter referred to as low molecular weight component etc.) easily penetrating into the (meth) acrylic acid alkyl ester copolymer.

  In the B layer, a base polymer is usually cross-linked using a cross-linking agent in order to adjust adhesive strength and suppress adhesive residue. At this time, the unreacted crosslinking agent remains as a low molecular weight body or oligomer. The acrylic resin as the base polymer originally contains a low molecular weight component having a low degree of polymerization at a certain rate. These move relatively freely in the B layer. At that time, a certain amount precipitates or bleeds at the interface with the semiconductor wafer, peels off the adhesive film, adheres and remains on the wafer side, and becomes transfer contaminants. That is, in order to reduce transfer contaminants, it is important to reduce low molecular weight components and the like in the B layer. However, due to the reactivity of the polymerization reaction and cross-linking reaction, it is impossible to reduce the generation of low-polymerization degree components and unreacted components to zero. Is not economical. That is, in order to prevent transfer contamination, it is best to remove these low molecular weight components and the like from the B layer in the final sheet state.

  Here, for example, when the A layer (or C layer) is the same resin as the B layer, the low molecular weight component and the like can be diffused relatively freely to the A layer side. In addition, since there is no cross-linking agent component in the A layer, the low molecular weight component and the like in the B layer are greatly reduced by diffusing to the A layer side. For example, assuming that the crosslinking agent component diffuses freely in both the A layer and the B layer, and the volume ratio of the A layer and the B layer is 9: 1, the amount of the crosslinking agent component remaining in the B layer is the case of the B layer alone Compared to the above, it is reduced by 90%. In addition, when the A layer is a resin of a different type from the B layer, for example, a resin such as polyester, polyvinyl chloride, or polyethylene, low molecular weight components are difficult to diffuse into the A layer. The effect of reducing low molecular weight components and the like is significantly reduced.

  When the A layer of the present invention is an acrylic resin film containing a (meth) acrylic acid alkyl ester copolymer as a main component, the (meth) acrylic acid alkyl ester copolymer used for the A layer is an acrylic acid alkyl ester and It is a copolymer containing at least one monomer component selected from alkyl methacrylate. The monomer component of the copolymer may consist solely of a monomer component selected from the above-mentioned alkyl acrylates and alkyl methacrylates, or a copolymer other than alkyl acrylate or alkyl methacrylate. Ingredients may be included.

Examples of the (meth) acrylic acid alkyl ester used in the A layer of the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl ( (Meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) Examples include esters of (meth) acrylic acid such as acrylate, dodecyl (meth) acrylate, and octadecyl (meth) acrylate with C _{1 to} C ₂₂ saturated aliphatic alcohols.

  Examples of the copolymer component other than the above used in the A layer of the present invention include monofunctional and polyfunctional monomer components. Examples of the monofunctional monomer component include esters with alicyclic alcohols such as cyclohexyl (meth) acrylate, esters with phenols such as phenyl (meth) acrylate, and aromatics such as benzyl (meth) acrylate. Esters with alcohol, styrene, α-methylstyrene, 1-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4- ( Phenylbutyl) aromatic vinyl monomers such as styrene and halogenated styrene, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, butadiene, isoprene, 2,3-dimethylbutadiene, 2-methyl-3- Ethyl butadiene, 1,3-pentadiene, 3-methyl- Conjugated diene monomers such as 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 3-methyl-1,3-heptadiene, 1,3-octadiene, cyclopentadiene, chloroprene, and myrcene. . Examples of the polyfunctional monomer include acrylic acid such as allyl (meth) acrylate, methallyl (meth) acrylate, allyl cinnamate, and methallyl cinnamate, unsaturated monocarboxylic acid and allyl alcohol, and methallyl alcohol. Esters, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate, diesters of unsaturated monocarboxylic acids and glycols such as hexanediol di (meth) acrylate, diallyl phthalate, diallyl terephthalate, diallyl isophthalate And esters of dicarboxylic acids such as diallyl maleate and unsaturated alcohols, and divinylbenzene.

  The layer A of the present invention is preferable, for example, when the multilayer structure polymer particles disclosed in Japanese Patent Application Laid-Open No. 2004-79916 are included, because the expandability is particularly good. However, in this case as well, the multilayer structure polymer particles must be composed mainly of the (meth) acrylic acid alkyl ester copolymer shown above, and other base polymers of the multilayer structure particles. However, the effect of the present invention cannot be obtained unless the main component is a (meth) acrylic acid alkyl ester copolymer.

  When the release film made of an acrylic resin film containing a (meth) acrylic acid alkyl ester copolymer as a main component is provided on the re-peeling pressure-sensitive adhesive sheet of the present invention, the A layer of the present invention is shown above. It may not be the acrylic resin film which has a (meth) acrylic-acid alkylester copolymer as a main component. The film used for the A layer in that case is not particularly limited, and examples thereof include general-purpose plastic films such as polyester films such as polyethylene terephthalate and polyolefin films such as polyethylene and polypropylene. However, as described above, the polyvinyl chloride film contains a plasticizer and is not preferable because it causes transfer contamination. In addition, when using films other than a (meth) acrylic-acid alkylester copolymer for A layer, it may halve compared with the case where the effect obtained is used.

  The thickness of the A layer of the present invention varies depending on the purpose of use and is not particularly limited, but is preferably 10 to 500 μm, more preferably 25 to 300 μm, and still more preferably 38 to 250 μm. When the thickness is smaller than 10 μm, the handleability may be reduced, or the diffusion volume of the unreacted component in the A layer may be reduced, and the transfer contamination reduction effect may be insufficient. Further, when the thickness is larger than 300 μm, it is not preferable in terms of transportability and cost.

  B layer of this invention consists of additive components, such as a (meth) acrylic-acid alkylester copolymer which is a base polymer, and a crosslinking agent. The (meth) acrylic acid alkyl ester copolymer used for the B layer may be the same acrylic resin as the A layer, but generally, the B layer has a functional group for crosslinking. In many cases, it is different from the acrylic resin of the A layer.

  The (meth) acrylic acid alkyl ester copolymer used for the B layer of the present invention comprises an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester as a main monomer component. Examples of the constituent monomer include methyl group, ethyl group, purpyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, heptyl group, cyclohexyl group, 2-ethylhexyl. Group, octyl group, isooctyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group, dodecyl group, 30 or less, especially 4 Examples thereof include polymers having as a component one or more esters of acrylic acid or methacrylic acid having 18 to 18 linear or branched alkyl groups. In addition, other examples include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid, or maleic anhydride and itaconic anhydride. Acid anhydride monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, (meth) acrylic acid Hydroxyl group-containing monomers such as 8-hydroxyoctyl, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) -methyl acrylate, styrene sulfonic acid, allyl sulfo Sulfonic acid group-containing monomers such as acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamidepropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid, 2-hydroxy A phosphate group-containing monomer such as ethylacryloyl phosphate may be partially copolymerized. In addition, a polyfunctional monomer or the like may be copolymerized as a monomer component for copolymerization, if necessary, for the purpose of crosslinking the acrylic polymer. Examples of such monomers include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di ( Examples include meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate. One or more polyfunctional monomers can be used, and the amount used is preferably 30% by weight or less of the total monomers from the viewpoint of adhesive properties and the like.

  The B layer of the present invention contains a cross-linking agent in order to adjust the adhesive force or increase the cohesive force and suppress the adhesive residue. A crosslinking agent reacts with the functional group of the (meth) acrylic acid alkyl ester copolymer which is a base polymer, and produces | generates a crosslinked structure. Examples of such a crosslinking agent include polyvalent isocyanate compounds, polyvalent epoxy compounds, polyvalent imine compounds, chelate compounds and the like.

  Examples of the polyvalent isocyanate compound used as the crosslinking agent of the present invention include aromatic polyvalent isocyanate compounds, aliphatic polyvalent isocyanate compounds, and alicyclic polyvalent isocyanate compounds. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′- Examples include diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, dicyclohexylmethane-2,4′-diisocyanate, and lysine isocyanate.

  Specific examples of the polyvalent epoxy compound used as the crosslinking agent of the present invention include 1,3-bis (N, N-) diglycidylaminomethyl) benzene and 1,3-bis (N, N-diglycidylaminomethyl). ) Toluene, N, N, N ′, N′-tetraglycidyl-4,4-diaminodiphenylmethane and the like.

  Specific examples of the polyvalent imine compound used as the crosslinking agent of the present invention include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide) trimethylolpropane-tri-β-aziridinylpro Examples include pionate, tetramethylolmethane-tri-β-aziridinylpropionate, N, N′-toluene-2,4-bis (1-aziridinecarboxamide) triethylenemelamine.

  Although content of the crosslinking agent used for B layer of this invention is not specifically limited, From a viewpoint of control of adhesiveness or the hardness of B layer, with respect to 100 weight part of (meth) acrylic-acid alkylester copolymers. 0.05 to 20 parts by weight, preferably 0.1 to 15 parts by weight, more preferably 1 to 10 parts by weight.

  Although the thickness of B layer of this invention changes also with uses, it is 1-300 micrometers, Preferably it is 3-200 micrometers, More preferably, it is about 5-100 micrometers. When the thickness exceeds 300 μm, the amount of unreacted cross-linking component generated increases, and the reduction effect by providing the A layer may not be sufficient. In addition, when the thickness is less than 1 μm, the manufacturing cost may increase.

  As described above, the pressure-sensitive adhesive sheet of the present invention may be provided with a release film layer (C layer) on the surface layer of the B layer. In that case, the side which provides a release film is a side opposite to A layer. That is, the layer configuration is A layer / B layer / C layer. The pressure-sensitive adhesive sheet of the present invention is often wound and stored in a roll until it is used, but the release film layer is handled by sticking the back surface of the pressure-sensitive adhesive layer and the base film at that time. It is a layer provided in order to prevent property deterioration and contamination of the adhesive layer surface. In general, a release film having a film surface coated with a release agent such as organic silicon is used. In addition, when bonding a release film with an adhesive sheet, the surface (release process layer) which apply | coated the said mold release agent is bonded together with the adhesion layer side.

  When a release film is provided on the pressure-sensitive adhesive sheet of the present invention, the C layer is preferably composed mainly of a (meth) acrylic acid alkyl ester copolymer. By making the C layer a (meth) acrylic acid alkyl ester copolymer similar to the B layer, low molecular weight components in the B layer can be diffused not only to the A layer but also to the release film side. Therefore, the low molecular weight component in the B layer can be further reduced, which is preferable. Furthermore, since the C layer is peeled off immediately before the pressure-sensitive adhesive sheet of the present invention is applied to the wafer, the low molecular weight components and the like that have penetrated into the C layer are discarded outside the system, and return to the B layer again. There is no possibility. As a (meth) acrylic-acid alkylester copolymer used for C layer, the thing similar to A layer can be used.

  When the A layer of the present invention is mainly composed of a (meth) acrylic acid alkyl ester copolymer, the C layer is not necessarily composed of a (meth) acrylic acid alkyl ester copolymer as a main component. In this case, the C layer may be a polyester film or a polyolefin film that is generally used as a release film, but in that case, the further effect of reducing the transfer contamination cannot be obtained.

  The pressure-sensitive adhesive sheet of the present invention is preferably stored in the form of being rolled up from the viewpoint of convenience and prevention of surface contamination during storage. As described above, when the release film is not provided, the surface on the side of the B layer on which the A layer is not provided comes into contact with the back surface of the A layer by storing in a roll shape. ) The same effects as those obtained when the A layer and the C layer made of an acrylic acid alkyl ester copolymer are provided, and the penetration effect of the low molecular weight component in the B layer is increased, which is preferable. However, the effect of making it into a roll is a so-called kinetic effect in which the diffusion proceeds faster due to the increased contact area, and the effect is remarkable when the storage time is relatively short. However, when storing for a long time, the effect of preventing transfer contamination is higher in the three-layer structure in which the A layer and the C layer are provided. This is because the effect of making a roll has only a kinetic effect, whereas in the case of three layers, in addition to the kinetic effect, the volume per se where low molecular weight components can diffuse increases. This is because a so-called equilibrium effect is also obtained. In addition, when winding the adhesive sheet of 2 layer structure which does not provide C layer in roll shape, it is preferable to give mold release processing to the surface on the opposite side to B layer of A layer from a viewpoint of blocking prevention. . Even when the layer B is in contact with the layer B through the mold release treatment, the above effect can be sufficiently exhibited.

  The pressure-sensitive adhesive sheet of the present invention can be processed into any shape depending on the application. For example, in a back grind application, it is preferable to cut and use the same shape as the wafer in advance.

  The application of the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it is for processing semiconductor wafers, and particularly preferably, it includes a surface protective sheet in a back grinding process and a wafer holding sheet in a dicing process.

  Processing the semiconductor wafer using the pressure-sensitive adhesive sheet of the present invention is preferable because contamination of the semiconductor wafer can be significantly reduced. The processing method of the semiconductor wafer includes, for example, back grinding processing in which the pressure-sensitive adhesive sheet of the present invention is applied to the surface of the semiconductor wafer and the back surface is polished, or dicing in which the pressure-sensitive adhesive sheet of the present invention is applied to the back surface of the semiconductor wafer and the wafer is cut into small pieces. Examples include processing.

  When the adhesive sheet of the present invention is applied to a silicon wafer and then peeled off, the amount of organic contamination transferred to the silicon wafer (referred to as transfer contamination amount) is preferably less than 10% (atomic%) in terms of carbon in the surface element ratio, More preferably it is less than 5%, most preferably less than 2%. The transfer contamination amount is a value obtained by subtracting the organic contamination amount before sticking the adhesive sheet from the organic contamination amount after sticking / peeling the adhesive sheet. When the transfer contamination amount exceeds 10%, in the semiconductor manufacturing process after the process using the pressure-sensitive adhesive sheet, process troubles such as defective wire bonding and package cracks may occur and productivity may be reduced.

  Although the example of the manufacturing method of the adhesive sheet of this invention is demonstrated below, a manufacturing method is not limited to this.

[Adhesive (B layer) composition]
The pressure-sensitive adhesive composition ((meth) acrylic acid alkyl ester copolymer) forming the B layer of the present invention can be produced according to a known polymerization method such as a solution polymerization method, a bulk polymerization method, and an emulsion polymerization method. From the viewpoint of ease of application to the film, for example, solution polymerization can be used. Dissolve the main monomer component and copolymerization monomer component in a predetermined amount in a solvent such as toluene, and depending on the type of monomer, copolymerize at 50 to 70 ° C. for 5 to 12 hours, and add a crosslinking agent as necessary. Thus, a solution of the pressure-sensitive adhesive composition is obtained.

[Base film (A layer)]
The base film used for the A layer of the present invention is a resin prepared by an existing method (for example, Japanese Patent Application Laid-Open No. 2004-79916), and the existing film such as a melt extrusion method, a solution casting method, and a calendar method is used. It can be produced using a film forming method. In particular, as described in JP-A-2004-79916, an acrylic film composed of 0-50% by weight of a thermoplastic resin and 100-50% by weight of the multilayer structure polymer particles is from the viewpoint of flexibility and stretchability. Is preferred. Further, a method by radiation polymerization may be used. In the radiation polymerization, a solution in which one or two or more (meth) acrylic acid alkyl ester monomers and a photopolymerization initiator are mixed with a (meth) acrylic oligomer for viscosity adjustment as necessary is subjected to a release treatment. In this method, a layer is formed between the light-transmitting sheets and then cured by photoreaction to form a film, for example, a method described in JP-A-9-253964. When using the above-mentioned radiation polymerization method or the method of JP-A-2004-79916, the effect of reducing the low molecular weight is greatly preferred.

[Preparation of adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is obtained by applying the pressure-sensitive adhesive to at least one surface of the base film obtained above. The application can be performed by an existing method. For example, a die coating method, a gravure coating method, a flexographic printing method, or the like can be used. Of these, the die coating method is preferably used. Further, using an oven, drying is performed at 70 to 170 ° C. for 1 to 15 minutes to remove the solvent. The obtained pressure-sensitive adhesive sheet is subjected to a release treatment on the surface of the A layer opposite to the B layer, if necessary, and is wound up in a roll shape. In addition, when a release film is provided, the said release process is not performed, but after winding a release film together on the B layer surface, it rolls up in roll shape.

[Methods for measuring physical properties and methods for evaluating effects]

(1) Molecular weight The measurement solution was filtered through a 0.45 μm membrane filter, and then the filtrate was air-dried to obtain a polymer solid. About the said polymer solid content, it measured on condition of the following and computed as "TSK standard polystyrene" conversion value. From the area ratio of the obtained differential molecular weight curve, the content of 100,000 or less components was determined.
GPC device: HLC-8120GPC manufactured by TOSOH
Column: TSKgel GMH-H (S) × 2 Column size: 7.8 mmI. D. × 300mm
Eluent: THF
Flow rate: 0.5ml / min
Concentration: 0.1 wt%
Injection volume: 100 μl
Column temperature: 40 ° C

(2) Transfer contamination amount Measurement was performed using a cleanly controlled silicon mirror wafer (manufactured by Shin-Etsu Semiconductor Co., Ltd., size: 4 inches, product number: CZ-N). In addition, clean management means that the amount of surface contamination before sticking the adhesive sheet is 10% or less in terms of the carbon ratio of the surface. An adhesive sheet was affixed to the silicon wafer mirror surface (applied using a 2 kg roller), held at 25 ° C. for 6 hours, and then peeled from the wafer at a rate of 300 mm / min. Next, using an X-ray photoelectron spectroscopic analysis (XPS) apparatus, the surface on which the pressure-sensitive adhesive sheet was attached was measured under the following conditions, and each element ratio of carbon, nitrogen, oxygen, and silicon (total amount: 100%) ) Was calculated. The amount of carbon increase before and after sticking the adhesive sheet (the value obtained by subtracting the measured value before sticking the adhesive sheet from the measured value) was taken as the transfer contamination amount.
XPS device: Quantum 2000, made by ULVAC-PHI
Xray setting: 200 μm diameter [30 W (15 kV)] point analysis X-ray source: Monochrome AlKα
Photoelectron extraction angle: 45 degrees Vacuum degree: 5 × 10 ^-9 torr
Neutralizing condition: combined use of neutralizing gun and ion gun (neutralization mode) (Note that the peak due to the C—C bond of C1s was corrected to 285.0 eV for the narrow scan spectrum)

(3) Thickness of base film, adhesive layer thickness Using a dial gauge with a minimum scale of 1 μm, measurement was performed according to JIS Z 0237.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
(Preparation of adhesive composition)
A blended composition of 100 parts by weight of butyl acrylate, 7 parts by weight of 2-hydroxyethyl acrylate, and 0.2 parts by weight of benzoyl peroxide in a 50% by weight solution of toluene (the concentration of the blended composition in toluene is 50% by weight), 60 ° C. For 6 hours to obtain a polymer solution. The weight average molecular weight of this polymer was 620,000, and the content of components having a molecular weight of 100,000 or less was 15 wt%.
Next, 2.2 parts by weight of polyisocyanate-based cross-linking agent (“Coronate L” manufactured by Nippon Polyurethane Co., Ltd.) is added to the above polymer solution (compared to 100 parts by weight of the solid content of the polymer solution), and the pressure-sensitive adhesive composition A product solution 1 was obtained.
(Preparation of base film)
An acrylic resin (“Parapet SA” manufactured by Kuraray Co., Ltd.) was formed at a temperature of 240 ° C. by a calendar film forming method to obtain a base film 1 having a thickness of 200 μm.
(Adjustment of release film)
As a release agent, 50 parts by weight of condensation reaction type silicone (“KS-723A” manufactured by Shin-Etsu Chemical Co., Ltd.), 50 parts by weight of condensation reaction type silicone (“KS-723B” manufactured by Shin-Etsu Chemical Co., Ltd.), alkyd 42 parts by weight of a modified resin silicone (“KS-883” manufactured by Shin-Etsu Chemical Co., Ltd.), 4 parts by weight of a curing catalyst (“CAT-PS-3” manufactured by Shin-Etsu Chemical Co., Ltd.), a curing catalyst (Shin-Etsu Chemical ( "CAT-PS-80" (made by Co., Ltd.) 2 parts by weight of the composition as a 1.5 wt% toluene solution (concentration of the blended composition in toluene 1.5 wt%), a polyethylene terephthalate film (thickness 50 µm) Tolu Co., Ltd. “Lumirror” was applied to one side with a smoothing bar so that the coating amount after drying was 0.2 g / m ² , dried in an oven at 100 ° C. for 2 minutes, and release film 1 Formed .
(Adjustment of adhesive sheet)
The pressure-sensitive adhesive composition solution 1 is applied on the base film 1 and dried at 120 ° C. for 3 minutes so that the thickness after drying is 20 μm, and then the release film 1 is further formed on the surface of the pressure-sensitive adhesive layer. The adhesive sheet was obtained by bonding.
As shown in Table 1, the obtained adhesive sheet was an excellent adhesive sheet with little transfer contamination to the silicon wafer.

Example 2
The base film was changed to a polyethylene terephthalate film having a thickness of 50 μm (“Lumirror” manufactured by Toray Industries, Inc .: base film 2), and the adhesive composition solution 1 was applied onto the base film 2 in the same manner as in Example 1. After coating and forming a 20 μm-thick adhesive layer, the 200 μm-thick acrylic film (base is the same film as the base film 1) that has been subjected to the same release treatment as in Example 1 (release film 2) By sticking together, an adhesive sheet was obtained.
As shown in Table 1, the obtained adhesive sheet was an excellent adhesive sheet with little transfer contamination to the silicon wafer.

Example 3
In exactly the same manner as in Example 1, an adhesive composition solution 1 and a base film 1 were produced. One surface of the base film 1 was subjected to the same mold release treatment as in Example 1, and an adhesive layer was provided on the opposite surface in the same manner as in Example 1 to obtain an adhesive sheet. Further, the obtained pressure-sensitive adhesive sheet 50m was wound up in a cylinder (made of hard vinyl chloride, outer diameter 76 mm) so that the pressure-sensitive adhesive surface and the release treatment surface were in contact with each other to obtain a roll-shaped pressure-sensitive adhesive sheet.
As shown in Table 1, the obtained roll-shaped pressure-sensitive adhesive sheet was an excellent pressure-sensitive adhesive sheet with little transfer contamination to the silicon wafer.

Example 4
In the same manner as in Example 1, a pressure-sensitive adhesive composition solution 1 and a base film 1 were produced. Furthermore, using the base film, the same mold release treatment was performed on one surface thereof to obtain a mold release film 2 made of an acrylic resin having a thickness of 200 μm. After providing a 20-micrometer-thick adhesive layer on the base film 1, the adhesive film was obtained by bonding the release film 2 together.
As shown in Table 1, the obtained pressure-sensitive adhesive sheet was an excellent pressure-sensitive adhesive sheet.

Example 5
A polymer composition comprising 100 parts by weight of 2-ethylhexyl acrylate, 4.8 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide was copolymerized in a 40% by weight toluene solution at 60 ° C. for 7 hours to obtain a polymer solution. Obtained. The weight average molecular weight of this polymer was 380,000, and the content of components having a molecular weight of 100,000 or less was 22 wt%. To this polymer solution, 0.1 part by weight of an epoxy-based crosslinking agent (“Tetrad C” manufactured by Mitsubishi Gas Chemical Co., Inc.) is added (compared to 100 parts by weight of the solid content of the polymer solution) to obtain a pressure-sensitive adhesive composition solution 2. It was.
The pressure-sensitive adhesive composition 2 was applied to the base film 1 in the same manner as in Example 1, and the release film 1 was further bonded to obtain a pressure-sensitive adhesive sheet.
As shown in Table 1, the obtained adhesive sheet was an excellent adhesive sheet with little transfer contamination to the silicon wafer.

Comparative Example 1
The base film was a polyethylene terephthalate film (“Lumirror”: base film 2 manufactured by Toray Industries, Inc.), and the release film 1 was bonded to obtain an adhesive sheet in the same manner as in Example 1.
As shown in Table 1, the obtained pressure-sensitive adhesive sheet was a pressure-sensitive adhesive sheet inferior in transfer contamination suppression to a silicon wafer.

Comparative Example 2
The base film is a low-density polyethylene film having a thickness of 60 μm (“NSO film” manufactured by Okura Kogyo Co., Ltd .: base film 3), the release film 1 is bonded, and the pressure-sensitive adhesive sheet is obtained in the same manner as in Example 1. Got. However, the drying conditions were 90 ° C. × 5 minutes.
As shown in Table 1, the obtained pressure-sensitive adhesive sheet was a pressure-sensitive adhesive sheet inferior in transfer contamination suppression to a silicon wafer.

Comparative Example 3
Using the base film 2, the release film 1 was bonded together to obtain an adhesive sheet in the same manner as in Example 5.
As shown in Table 1, the obtained pressure-sensitive adhesive sheet was a pressure-sensitive adhesive sheet inferior in transfer contamination suppression to a silicon wafer.

  From the results of Examples and Comparative Examples, it was found that transfer contamination correlates with the low molecular content in the pressure-sensitive adhesive layer. In addition, when a base film other than the present invention and a release film are used (comparative example), the transfer contamination amount is hardly changed by the base film, but the base film or the release film of the present invention is used. (Example), it was found that the amount of transfer contamination was significantly reduced. That is, it was found that all the different material films have almost no permeability of low molecular weight components, and only the film of the present invention has permeability and exhibits an effect of reducing transfer contamination.

It is a schematic sectional drawing which shows an example of the adhesive sheet for re-peeling (in the case of 2 layer structure which does not provide a release film) of this invention. It is a schematic sectional drawing which shows an example of the adhesive sheet for re-peeling (in the case of the 3 layer structure which provided the release film) of this invention. It is a schematic sectional drawing which shows an example of the adhesive sheet for re-peeling of this invention wound up by roll shape.

Explanation of symbols

1 Re-peeling adhesive sheet (two-layer construction)
2 Base film (A layer)
3 Adhesive layer (B layer)
4 Re-peeling adhesive sheet (3-layer construction)
5 Release film (C layer)
6 Release processing layer

Claims (6)

  A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (B layer) on at least one side of a base film (A layer), wherein both the A layer and the B layer are mainly composed of a (meth) acrylic acid alkyl ester copolymer. A pressure-sensitive adhesive sheet for re-peeling.   The pressure-sensitive adhesive sheet for re-peeling according to claim 1, which is wound up in a roll shape so that the surfaces of the exposed A layer and B layer are in contact with each other.   A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (B layer) on at least one side of a base film (A layer), a surface layer of the B layer, and having a release film (C layer) on the opposite side of the A layer, Both the B layer and the C layer are mainly composed of a (meth) acrylic acid alkyl ester copolymer.   The pressure-sensitive adhesive sheet for re-peeling according to claim 3, wherein the A layer contains a (meth) acrylic acid alkyl ester copolymer as a main component.   The pressure-sensitive adhesive sheet for re-peeling according to any one of claims 1 to 4, wherein the amount of organic contamination transferred to the silicon wafer after being attached to and peeled from the silicon wafer is less than 10% in terms of carbon in terms of surface element ratio.   The processing method of the semiconductor wafer using the adhesive sheet for re-peeling in any one of Claims 1-5.

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