JP4367769B2 - Adhesive sheet for holding and protecting semiconductor wafer and method for grinding back surface of semiconductor wafer - Google Patents

Description

  The pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer according to the present invention relates to a pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer used when processing a semiconductor wafer such as silicon or gallium arsenide. More specifically, in the back grinding process of polishing and grinding the back surface of the circuit pattern forming surface (hereinafter sometimes referred to simply as “pattern surface”) of the semiconductor wafer, the pattern surface is protected by being attached to the pattern surface. It is used as an adhesive sheet for grinding a semiconductor wafer back surface for holding a semiconductor wafer thinned by polishing grinding. The adhesive wafer for holding and protecting a semiconductor wafer according to the present invention is used as an adhesive sheet for dicing used for holding and protecting a wafer in a dicing process in which the wafer is cut into individual patterns and divided as semiconductor elements. The adhesive sheet for protecting and holding a semiconductor wafer of the present invention is particularly useful as an adhesive sheet for grinding a semiconductor wafer back surface.

  In the back grinding process in which the surface opposite to the circuit pattern forming surface of the semiconductor wafer is ground and ground, and in the dicing process in which the wafer is cut into individual chips, the pattern surface is damaged or contaminated by grinding scraps or grinding water. Therefore, it is necessary to protect the pattern surface. In addition, the semiconductor wafer itself is thin and fragile, and the pattern surface of the semiconductor wafer is uneven, so that there is a problem that it is easily damaged by a slight external force.

  In order to protect the pattern surface during semiconductor wafer processing and prevent damage to the semiconductor wafer, in the back grinding process, a method of attaching an adhesive sheet such as a back grind tape to the pattern surface of the semiconductor wafer is known. Yes. A dicing tape is used in the dicing process. As said adhesive sheet, the silicon wafer processing film which provided the adhesive layer on the surface of the base material sheet whose Shore D type hardness is 40 or less is proposed, for example (refer patent document 1). Further, an auxiliary film having a Shore D hardness of greater than 40 was laminated on one surface of the base film having a Shore D hardness of 40 or less, and an adhesive layer was disposed on the other surface of the base film. A wafer processing film has been proposed (see Patent Document 2).

  However, in recent years, the difference in the unevenness of the pattern surface of the semiconductor wafer has increased. For example, in a wafer with a polyimide film, the unevenness difference is about 1 to 20 μm. Further, a defect mark (bad mark) for recognizing a defective semiconductor chip has irregularities with a height difference of about 10 to 70 μm. Furthermore, the height of the bump formed on the patterned electrode is about 20 to 200 μm. Therefore, in the method using a conventionally known pressure-sensitive adhesive sheet, the sheet cannot follow these irregularities, and the adhesion between the pressure-sensitive adhesive and the wafer surface becomes insufficient. As a result, at the time of wafer processing, peeling of the sheet, intrusion of grinding water or foreign matter into the pattern surface, processing errors, occurrence of dimples, chip jumping, etc. may occur, and the wafer may be damaged.

  In addition, back-grind tapes and dicing tapes used when processing semiconductor wafers often use radiation-curing type holding and protecting adhesive sheets in order to facilitate peeling after processing. However, particularly in the case of the UV effect type that is easy to handle, if the irregularities on the pattern surface are not filled and a gap remains, curing failure due to oxygen may occur and adhesive may remain.

In order to cope with the above problem, an adhesive sheet for holding and protecting a semiconductor wafer is proposed in which an intermediate layer having an elastic modulus of 30 to 1000 kPa and a gel content of 20% or less is provided between a base material layer and an adhesive layer. (Patent Document 3). The pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer described in Patent Document 3 has good followability even if the unevenness of the wafer surface is large to a certain extent, and can infiltrate the grinding water and foreign matter into the pattern surface. Can be prevented. However, in the semiconductor wafer holding / protecting adhesive sheet described in Patent Document 3, the intermediate layer may protrude from the side surface of the wafer due to the pressure of the grinding machine, which may cause wafer contamination. Further, it is not preferable because the wafer contamination tends to cause cracking or grinding failure during grinding.
Japanese Patent Application Laid-Open No. 61-10242 Japanese Patent Laid-Open No. 61-260629 JP 2001-203255 A

  An object of the present invention is to provide a pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer that can follow the unevenness even when the unevenness of the wafer surface is large and can prevent wafer contamination and wafer cracking.

  Furthermore, this invention aims at providing the back surface grinding method of a semiconductor wafer using the said adhesive sheet for semiconductor wafer holding | maintenance protection.

  As a result of intensive studies to achieve the above object, the present inventors have found the following adhesive sheet for holding and protecting a semiconductor wafer and completed the present invention. That is, the present invention is as follows.

1. At the time of semiconductor wafer processing, an adhesive sheet for holding and protecting the semiconductor wafer by sticking to the surface of the semiconductor wafer,
An intermediate layer (1) having an elastic modulus at 25 ° C. of 10 to 1000 kPa and a gel content of 26 to 45% is provided on one surface of the base material layer (3), and an adhesive is provided on the surface of the intermediate layer (1). A pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer, wherein a layer (2) is formed.

2. The thickness t ₁ of the intermediate layer (1) is 20 to 500 μm, the thickness t _{2 of the} pressure-sensitive adhesive layer (2) is 1 to 100 μm, and the ratio is t ₂ / t ₁ = 0.01 to 2. The pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer according to 1 above, which is 0.5.

  3. 3. The adhesive sheet for holding and protecting a semiconductor wafer according to 1 or 2 above, wherein the intermediate layer (1) contains an acrylic polymer as a constituent material.

  4). 4. The adhesive sheet for holding and protecting a semiconductor wafer as described in 3 above, wherein the intermediate layer (1) further contains a radiation curable oligomer.

  5). The adhesive sheet for holding and protecting a semiconductor wafer according to any one of the above 1 to 4, wherein the adhesive layer (2) contains an acrylic polymer as a constituent material.

  6). 6. The semiconductor wafer holding protection according to 5 above, wherein the pressure-sensitive adhesive layer (2) is a radiation-curable pressure-sensitive adhesive layer containing a radiation-curable acrylic polymer having a carbon-carbon double bond in the molecule. Adhesive sheet.

  7. 7. The semiconductor wafer holding protection according to 6 above, wherein the radiation curable pressure-sensitive adhesive layer (2) has an elastic modulus at 25 ° C. of 10 to 500 kPa and a gel content of 18 to 30% before radiation curing. Adhesive sheet.

  In the state which bonded the adhesive layer (2) of the adhesive sheet for semiconductor wafer holding | maintenance protection in any one of said 1-7 to the surface of the semiconductor wafer by which the circuit pattern was integrated, the back surface of a semiconductor wafer was attached. A method for grinding a back surface of a semiconductor wafer, comprising grinding.

  The sheet for holding and protecting a semiconductor wafer of the present invention has an intermediate layer (1) having a specific high elastic modulus and a predetermined gel content between the base material layer (3) and the pressure-sensitive adhesive layer (2). Therefore, when the pressure-sensitive adhesive sheet is attached to the wafer surface, the intermediate layer (1) and the pressure-sensitive adhesive layer (2) are appropriately deformed to cause unevenness on the surface of the semiconductor wafer. It can follow well. Therefore, the wafer and the holding protective sheet are well bonded, and grinding water and foreign matter intrusion into the wafer pattern surface, processing errors, occurrence of dimples, wafer cracking, and the like can be greatly reduced during grinding of the back surface of the wafer. In particular, it is effective in terms of the thickness accuracy of the ground wafer when the pattern surface of the semiconductor wafer has large unevenness, and is suitable when the unevenness height difference is 10 μm or more, further 15 μm or more. This is particularly effective when the thickness is 25 to 250 μm.

  Further, since the intermediate layer (1) has a specific high elastic modulus, it can be suppressed that the intermediate layer (1) protrudes to the side surface of the wafer due to the pressure of the grinding machine and the wafer is contaminated. It is also possible to more effectively suppress the occurrence of cracks and poor grinding.

  In addition, the semiconductor wafer holding / protecting sheet of the present invention is excellent in releasability from the wafer surface by forming the pressure-sensitive adhesive layer (2) with a radiation-curing pressure-sensitive adhesive, and also has high retention and reinforcement to the wafer. Can be provided.

  Such an adhesive sheet for holding and protecting a semiconductor wafer according to the present invention, like the adhesive sheet described in Patent Document 3, has the above-mentioned effect, that is, the surface of the wafer, as compared with the intermediate layer whose elastic modulus is lower than that of the present invention. Excellent effect on unevenness, wafer contamination, wafer cracking, etc.

  It is also suitable for making the wafer thinner. This is effective when the back surface is ground to a wafer thickness of 300 μm or less, preferably about 250 to 30 μm.

  Examples of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these examples. FIG. 1 is a cross-sectional view schematically showing an adhesive sheet for protecting and holding a semiconductor according to the present invention.

  In FIG. 1, 1 shows an intermediate | middle layer and the elasticity modulus of an intermediate | middle layer (1) is 10-1000 kPa, Preferably it is 10-700 kPa. When the elastic modulus of the intermediate layer (1) is less than 10 kPa, the intermediate layer becomes soft, so that the sheet or tape shape stability is lowered. For example, when the sheet is subjected to long-term storage or a load, the sheet is highly likely to be deformed. Further, the intermediate layer protrudes due to the pressure applied to the sheet, and there is a problem of contaminating the semiconductor wafer. In addition, when the elastic modulus of the intermediate layer (1) exceeds 1000 kPa, the followability to the irregularities on the surface of the semiconductor wafer required by the present invention is inferior. Etc. are likely to occur.

  The “elastic modulus” means that the intermediate layer was measured with a dynamic viscoelasticity measuring device “Rheometrics ARES” (manufactured by Rheometric Co., Ltd.) (frequency: 1 Hz, plate diameter: 7.9 mmφ, strain: 1% (25 ° C), the sample thickness 3 mm), and the elastic modulus G ′ at 25 ° C.

  Moreover, the gel content of the intermediate layer (1) is 26 to 45%. Preferably it is 30 to 45%. When the gel content of the intermediate layer (1) exceeds 45%, the movement of the polymer at the time of application becomes poor and the followability to the uneven surface is inferior, so that cracks and dimples are likely to occur during wafer grinding. . In this case, even if the elastic modulus is within the above range, if the gel content is high, the followability is inferior, which is not preferable. On the other hand, if the gel content is lower than 26%, the intermediate layer protrudes from the side surface of the wafer due to the pressure of the grinding machine that acts on the upper surface during back surface grinding, which is not preferable because it tends to cause cracks and poor grinding during grinding.

  The “gel content” means that an intermediate layer having a weight of about 0.8 g (W1) was immersed in 100 g of a mixed solvent of toluene and ethyl acetate (1: 1) at 25 ° C. for 7 days and then dried. Weight after: W2 (g) is obtained, and is a value obtained by {(W1-W2) / W1} × 100 (%).

  The thickness of the intermediate layer (1) can be appropriately selected within a range that does not impair the height of the irregularities on the wafer surface, the retainability and protection of the wafer, but is preferably about 20 to 500 μm, more preferably about 30 to 200 μm. . When the thickness of the intermediate layer (1) is less than 20 μm, it is difficult to follow the unevenness of the wafer pattern surface, and cracks and dimples are likely to occur during grinding of the wafer. On the other hand, if the thickness of the intermediate layer (1) exceeds 500 μm, it takes time for the intermediate layer to stick out and affix the sheet, so that there is a problem that the working efficiency is lowered and the apparatus does not enter the grinding machine. Further, when the sheet is peeled from the wafer, the thin wafer after grinding may be damaged by the bending stress of the sheet.

  The material for the intermediate layer (1) is not particularly limited as long as it has the characteristics in the above range, but has good adhesiveness (anchoring property) with the pressure-sensitive adhesive layer (2), and can adjust the elastic modulus. Acrylic polymers are preferred from the standpoint of ease. Specific examples of the main monomer constituting the acrylic polymer include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, isooctyl (meth) acrylate, and (meth) acrylic acid. (Meth) acrylic acid alkyl ester having 4 to 12 carbon atoms in the alkyl group such as lauryl. In addition, (meth) acrylic acid ester means acrylic acid ester and / or methacrylic acid ester, and (meth) of the present invention has the same meaning. Among these (meth) acrylic acid esters, one or more are used.

  In addition to the main monomer, other monomers that can be copolymerized may be used in combination with the acrylic polymer in order to adjust the elastic modulus and gel content and according to other required properties. The amount of other monomers can be appropriately selected according to the type of each monomer within a range of less than 30% by weight of the total monomers.

  Other monomers include (meth) acrylic acid alkyl esters having 1 to 3 carbon atoms in the alkyl group, such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate; (meth) acrylic (Meth) acrylic acid alkyl ester having 13 to 18 carbon atoms such as tridecyl acid and stearyl (meth) acrylate; acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid Other functionalities such as carboxy group-containing monomers such as hydroxyalkyl (meth) acrylate, glycerin dimethacrylate, glycidyl (meth) acrylate, methyl glycidyl methacrylate, aminoethyl (meth) acrylate, 2methacryloyloxyethyl isocyanate Monomer; Triethylene glycol Polyfunctional monomers such as vinyl diacrylate, ethylene glycol dimethacrylate, trimethylolpropane tri (meth) acrylate; vinyl acetate, styrene, (meth) acrylonitrile, N-vinylpyrrolidone, (meth) acryloylmorpholine, cyclohexylmaleimide, isopropylmaleimide , (Meth) acrylamide and the like.

  The acrylic polymer can be obtained by copolymerizing the monomer or a mixture thereof by a method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, or a suspension polymerization method.

  The number average molecular weight of the polymer used for the intermediate layer (1) is not limited as long as the characteristics within the above range are maintained, but preferably in the range of 10,000 to 2,000,000. If it is less than 10,000, it will flow easily at high temperatures, and it will be difficult to maintain the sheet shape, and if it exceeds 2 million, it may be inferior in unevenness followability at the time of pasting.

  The polymer used for the intermediate layer (1) can contain a gel component within the above-mentioned range. For this purpose, as a crosslinking agent, an epoxy crosslinking agent, an isocyanate crosslinking agent, a melamine crosslinking agent, or the like is known. Can be added. When using a cross-linking agent, it is preferable that the amount used is about 0.005 to 4 parts by weight per 100 parts by weight of the base polymer to be cross-linked.

  The intermediate layer (1) may contain other components (additives) as long as the above characteristics are not impaired. Examples of such components include tackifiers, plasticizers, softeners, fillers, antioxidants, and the like. The intermediate layer (1) can contain a radiation curable oligomer (such as an ultraviolet curable oligomer). When a radiation curable oligomer is added, the intermediate layer (1) can be slightly cured when irradiated with radiation during peeling. The radiation curable oligomer is preferably blended in an amount of 35 parts by weight or less, preferably about 0.5 to 35 parts by weight with respect to 100 parts by weight of the base polymer.

  Although the said intermediate | middle layer (1) may be comprised by one layer, it may have the multilayered structure which consists of several layers of the same kind or a different kind.

  Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer (2) include conventional pressure-sensitive adhesives such as acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, and rubber-based pressure-sensitive adhesives. An acrylic pressure-sensitive adhesive is preferred from the viewpoint of ease of design. An adhesive can also be used individually by 1 type or in mixture of 2 or more types.

  Examples of the acrylic polymer that is the base polymer of the acrylic adhesive include, for example, methyl group, ethyl group, purpyl group, isopropyl group, n-butyl group, t-butyl group, isobutyl group, amyl group, isoamyl group, and hexyl group. 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, Examples thereof include polymers containing as a component one or more of (meth) acrylic acid alkyl esters having a linear or branched alkyl group having 30 or less carbon atoms, particularly 4 to 18 carbon atoms such as dodecyl group.

  In the preparation of the acrylic polymer, other monomers copolymerizable with the (meth) acrylic acid alkyl ester are added to improve adhesion by introducing functional groups or polar groups, or the glass transition temperature of the copolymer. May be controlled to improve or modify the cohesive strength and heat resistance. Examples of other copolymerizable monomers used for this purpose include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, carboxyl group-containing monomers such as itaconic acid, maleic acid, fumaric acid and crotonic acid; maleic anhydride Acid anhydride monomers such as acid and itaconic anhydride; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and 6-hydroxy (meth) acrylate Hydroxyl group-containing monomers such as hexyl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; Sulfonic acid groups such as lensulfonic acid, allylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acrylamidepropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid Containing monomer: Phosphoric acid group-containing monomer such as 2-hydroxyethylacryloyl phosphate.

  The main component (meth) acrylic acid alkyl ester and other monomers copolymerizable therewith are the former 70 to 100% by weight, preferably 85 to 95% by weight, and the latter 30 to 0% by weight, preferably It is preferable that the amount is 15 to 5% by weight. By using the amount within this range, it is possible to achieve a good balance of adhesiveness and cohesive force.

  In addition, a polyfunctional monomer or the like may be used 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. As the polyfunctional monomer, one type or two or more types can be used, and the use amount thereof is preferably 30% by weight or less of the total monomers from the viewpoint of adhesive properties and the like.

  Such an acrylic polymer is prepared by applying an appropriate method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method or a suspension polymerization method to a mixture of one or two or more component monomers, for example. Can do.

  In the present invention, the acrylic polymer has a number average molecular weight of, for example, about 200,000 to 3,000,000, preferably about 250,000 to 1,500,000.

  The polymer constituting the pressure-sensitive adhesive may have a crosslinked structure. Such a pressure-sensitive adhesive is obtained by blending a crosslinking agent with a polymer obtained from a monomer mixture containing a monomer having a functional group such as a carboxyl group, a hydroxyl group, an epoxy group, or an amino group (for example, an acrylic monomer). It is done. In the sheet provided with the pressure-sensitive adhesive layer (2) containing a polymer having a crosslinked structure, the self-holding property is improved, so that the deformation of the sheet can be prevented and the flat state of the sheet can be maintained. Therefore, it can be simply and accurately attached to a semiconductor wafer using an automatic attaching apparatus or the like.

  As the radiation curable pressure-sensitive adhesive, a known and commonly used crosslinking agent, for example, an epoxy crosslinking agent, an aziridine crosslinking agent, an isocyanate crosslinking agent such as polyisocyanate, and the like can be used. When using a crosslinking agent, it is preferable to use about 0.005 to 4 parts by weight of the crosslinking agent based on 100 parts by weight of the base polymer to be crosslinked.

  Moreover, in this invention, it is preferable to use a radiation-curing-type adhesive as an adhesive layer (2). When the pressure-sensitive adhesive layer (2) is composed of a radiation curable pressure-sensitive adhesive, the plastic fluidity is imparted to the pressure-sensitive adhesive by the oligomer component when the sheet is attached, so that the attachment becomes easy, and at the time of sheet peeling, Since a low-adhesion substance is generated by irradiation with radiation, it can be easily peeled from the wafer.

  The radiation-curable pressure-sensitive adhesive can be obtained, for example, by blending an adhesive substance with an oligomer component that is cured by radiation irradiation to form a low-adhesion substance. In the case of using a radiation curable pressure-sensitive adhesive to which a radiation-curable oligomer has been added to form the pressure-sensitive adhesive layer (2), the movement of the oligomer occurs due to the storage of the pressure-sensitive adhesive tape. Changes are likely to appear. Examples of the radiation curable pressure-sensitive adhesive include acrylic polymers having a carbon-carbon double bond in the molecule. Such a radiation curable pressure-sensitive adhesive is preferable because it does not change due to migration of the oligomer. These two types of radiation curable adhesives can be used in combination.

  In the present invention, the radiation is not particularly limited as long as it can be polymer-cured, and examples thereof include X-rays, electron beams, and ultraviolet rays. Ultraviolet rays are preferable because of easy handling.

  The acrylic polymer having a carbon-carbon double bond in the molecule will be described. There are various known methods for introducing a carbon-carbon double bond into the inner molecular chain of an acrylic polymer. For ease of molecular design, after copolymerizing a monomer having a functional group in advance, A method is preferred in which a monomer having another functional group capable of addition reaction with this functional group and a carbon-carbon double bond is condensed or added while maintaining the carbon-carbon double bond.

  Examples of combinations of these functional groups include, for example, carboxylic acid groups and epoxy groups, carboxylic acid groups and aziridyl groups, hydroxyl groups and isocyanate groups, and any combination that produces the above polymer after the reaction. Any combination may be used, but a combination of a hydroxyl group and an isocyanate group is preferably used because of the ease of reaction tracking.

  For example, examples of the isocyanate compound having a carbon-carbon double bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl isocyanate and the like.

  Examples of hydroxyl group-containing compounds that react with such isocyanate compounds include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) Compounds having an ester bond in its molecule, such as 6-hydroxyhexyl acrylate, and compounds having an ether bond in its molecule, such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, etc. Preferably used. However, any compound can be used as long as it is a compound capable of generating the polymer structure after the reaction.

  Moreover, as a radiation curable oligomer mix | blended with a radiation curable adhesive, various oligomers, such as a urethane type, polyether type, polyester type, a polycarbonate type, a polybutadiene type, can be selected and combined. These radiation curable oligomers are preferably added to such a degree that does not deteriorate the properties. The radiation curable oligomer is usually in the range of 30 parts by weight or less, preferably in the range of 0 to 10 parts by weight with respect to 100 parts by weight of the polymer.

  The radiation curable pressure-sensitive adhesive usually contains a polymerization initiator. As the polymerization initiator, conventionally known products can be used as appropriate. For example, 4- (2-hydroxyethoxy) is an example of a photopolymerization initiator that may be blended when a curing method using ultraviolet rays is employed. Α-ketol compounds such as phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α′-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, 1-hydroxycyclohexyl phenyl ketone; methoxyacetophenone, Acetophenone compounds such as 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1; benzoin ethyl ether , Benzoin isopropyl ether, anisoin methyl ether Benzoin ether compounds such as ter; ketal compounds such as benzyl dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime Optically active oxime compounds such as benzophenone, benzoylbenzoic acid, benzophenone compounds such as 3,3′-dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4- Thioxanthone compounds such as dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone; camphorquinone; halogenated Ton; acyl phosphino sulfoxide; an acyl phosphonium diisocyanate and the like. The amount of these polymerization initiators used is, for example, about 1 to 10 parts by weight with respect to 100 parts by weight of the radiation curable polymer (or oligomer).

  Furthermore, you may make the adhesive layer (2) contain the component which foams or expands by heating. Thermally expandable or expandable components include, for example, thermally expandable microspheres in which a substance that is easily gasified by heating, such as isobutane and propane, is encapsulated in an elastic shell [for example, trade names: Microsphere, Matsumoto And the like. When such a thermally foamable or thermally expandable component is contained in the pressure-sensitive adhesive layer (2), the pressure-sensitive adhesive layer (2) expands by heat treatment after the wafer grinding process, and the pressure-sensitive adhesive layer (2) and the wafer Therefore, the sheet can be easily peeled from the wafer.

  Although the elasticity modulus of an adhesive layer (2) can be suitably set in the range which does not impair the adhesiveness and retention property with respect to a wafer, Preferably it is 10-500 kPa. If the pressure is less than 10 kPa, the pressure-sensitive adhesive becomes soft, so that the wafer retainability and protection may be lowered. If the pressure exceeds 500 kPa, the initial adhesive force may not be obtained.

  In the case of the radiation curable pressure-sensitive adhesive layer, before the radiation curing, the elastic modulus is 30 to 500 kPa and the gel content is 18 to 30%, the uneven absorbency, wafer dirt under pressure (excess), It is preferable from the point of peelability.

  Although the thickness of an adhesive layer (2) can be suitably set in the range which does not impair the retainability and protection of a wafer, Preferably it is about 1-100 micrometers, More preferably, it is about 2-60 micrometers. If the thickness of the pressure-sensitive adhesive layer (2) is less than 1 μm, the intermediate layer (1) may be deposited due to the destruction of the pressure-sensitive adhesive layer (2). If the thickness exceeds 100 μm, It becomes difficult to follow the unevenness on the surface, which is not preferable.

The ratio of the thickness t ₁ of the thickness t ₂ and an intermediate layer of the pressure-sensitive adhesive layer (2) (1), t ₂ / t ₁ = 0.01 to 0.5, preferably 0.02 to 0.3 Degree. If t ₂ / t ₁ is less than 0.01, the adhesive strength may not be sufficiently reduced after irradiation, and peeling may be difficult. If t ₂ / t ₁ exceeds 0.5, the effect of the intermediate layer is exhibited. Accordingly, it becomes difficult to follow the unevenness of the wafer pattern surface, and cracks and dimples are likely to occur during grinding of the wafer.

  The substrate layer (3) is not particularly limited. For example, polyester such as polyethylene terephthalate (PET); polyolefin resin such as polyethylene (PE) and polypropylene (PP); polyimide (PI); polyetheretherketone (PEEK) A polyvinyl chloride resin such as polyvinyl chloride (PVC); a polyvinylidene chloride resin; a polyamide resin; a polyurethane; a polystyrene resin; an acrylic resin; a fluororesin; a cellulose resin; and a thermoplastic resin such as a polycarbonate resin. In addition, thermosetting resin, metal foil, paper, etc. can be illustrated. In addition, the base material layer (3) may have a multilayer structure with a plurality of layers made of the same or different materials.

  The semiconductor wafer holding and protecting sheet of the present invention is a sheet-like product in which the intermediate layer (1), the pressure-sensitive adhesive layer (2), and the base material layer (3) are laminated as shown in FIG. The intermediate layer (1) is provided on one side of the material layer (3), and the adhesive layer (2) is formed on the surface of the intermediate layer (1).

  The semiconductor wafer holding and protecting sheet of the present invention may be wound into a tape shape as shown in FIG. In this case, in order to protect the pressure-sensitive adhesive layer (2), a release film layer (4) may be laminated thereon. Examples of the release film layer (4) include conventionally known silicone-treated and fluorine-treated plastic films (polyethylene terephthalate, polypropylene, etc.), paper, and nonpolar materials (polyethylene, polypropylene, etc.).

  In addition, when the semiconductor wafer holding protection sheet of the present invention is wound in a tape shape, as shown in FIG. 3, the release film layer (4) is not used, and the opposite surface of the substrate (that is, the pressure sensitive adhesive when wound). By providing the release treatment layer (5) on the surface in contact with the layer (2), rewinding can be facilitated.

  The release treatment layer (5) may be treated using a conventionally known release agent, and examples thereof include silicone treatment, fluorine treatment, and long-chain alkyl group-containing polymer treatment.

  The method for producing the semiconductor wafer holding / protecting sheet of the present invention is not particularly limited, and the intermediate wafer (1) and the pressure-sensitive adhesive layer (2) are formed on the base material layer (3) to hold the semiconductor wafer of the present invention. A protective sheet can be obtained. In order to apply the intermediate layer composition and the pressure-sensitive adhesive composition, a coating method such as roll coating, screen coating, and gravure coating may be used, and these may be directly formed on the substrate. And after forming on the release paper etc. which performed the peeling process on the surface, you may transfer to a base material.

  The sheet for protecting and holding a semiconductor according to the present invention can be applied to a semiconductor wafer surface (circuit pattern forming surface) so that the surface of the pressure-sensitive adhesive layer (2) is on the wafer side and pressed.

  More specifically, for example, (i) a wafer is placed on a table, and the pressure-sensitive adhesive sheet of the present invention is stacked thereon so that the pressure-sensitive adhesive layer (2) is on the wafer side. Paste while pressing. (Ii) In a pressurizable container (for example, an autoclave), the wafer and the sheet can be stacked as described above, and the inside of the container can be pressed to be attached to the wafer. At this time, it may be attached while being pressed by the pressing means. Further, (iii) it can be applied in the same manner as described above in a vacuum chamber. Moreover, when pasting by these methods, you may heat about 30-150 degreeC. The attaching method is not limited to these.

  The affixed sheet is peeled off manually or by machine after the semiconductor wafer is ground. At this time, when a radiation curable pressure sensitive adhesive is used as the pressure sensitive adhesive, it is preferable to irradiate with appropriate radiation before peeling, because the adhesive strength of the pressure sensitive adhesive layer is lowered and the film can be easily peeled off.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples. In the following description, “parts” means parts by weight.

  The pressure-sensitive adhesive sheet produced under the following conditions was affixed to a semiconductor wafer, ground, peeled off the pressure-sensitive adhesive sheet, and evaluated for “water intrusion”, “wafer crack after grinding”, and “wafer contamination”. The results are shown in Table 1.

(Lamination)
An adhesive sheet was prepared under the following conditions, and the adhesive sheet was applied to 25 6-inch wafers having a thickness of 625 μm (not including bumps) on which bumps having a height of 80 μm, 150 μm, and 250 μm were formed, and DR-8500II manufactured by Nitto Seiki Co., Ltd. Were bonded together. This is because the method of (i) above (a wafer is placed on a table, the sheet of the present invention is stacked thereon so that the adhesive layer (2) is on the wafer side, and pressing means such as a pressure roll, Equivalent to sticking while pressing).

(grinding)
The wafer to which the adhesive sheet was bonded by the above method was ground to a thickness of 280 μm using a silicon wafer grinding machine manufactured by DISCO Corporation.

(Peeling)
The adhesive sheet was peeled off from the wafer ground by the above method using DR-8500II manufactured by Nitto Seiki Co., Ltd. When a pressure sensitive adhesive was used as the pressure sensitive adhesive, a peeling tape was attached to the back of the pressure sensitive adhesive sheet after grinding, and the pressure sensitive adhesive sheet was peeled off together with the tape. Further, when UV adhesive is used as the adhesive, after grinding the wafer, the adhesive sheet is irradiated with ultraviolet rays of 400 mJ / cm ² to cure the adhesive layer, and a release tape is applied in the same manner. The adhesive sheet was peeled off with the tape.

[Evaluation item]
(Water intrusion)
This refers to a phenomenon in which grinding water penetrates between the wafer and the adhesive sheet during grinding, thereby contaminating the wafer. After peeling the adhesive sheet, the wafer in which water was confirmed on at least one of the 25 wafers by optical microscope observation (200 times) was assumed to have water intrusion.

(Wafer cracking)
Unevenness of bumps is not absorbed by the adhesive sheet during grinding. A wafer in which even one out of 25 wafers was cracked during grinding was considered to be cracked.

(Wafer contamination: protruding)
After grinding, the pressure-sensitive adhesive sheet was peeled off, and the outer periphery of the wafer was observed with an optical microscope (200 times). If a pressure-sensitive adhesive component having a size of 20 μm or more was found even at one location, the wafer was contaminated.

  As pressure-sensitive adhesives, the following pressure-sensitive pressure-sensitive adhesives and UV (ultraviolet) curable pressure-sensitive adhesives were prepared.

[Pressure sensitive adhesive]
A blended mixture consisting of 82 parts of 2-ethylhexyl acrylate, 3 parts of acrylic acid and 15 parts of acrylamide was solution polymerized in 100 parts of ethyl acetate to obtain an acrylic copolymer having a number average molecular weight of 700,000. Subsequently, 20 parts of an ester plasticizer (manufactured by Dainippon Ink & Chemicals, Inc., dioctyl phthalate) and melamine crosslinking agent (manufactured by Dainippon Ink & Chemicals, J-820-60N) 0 are added to 100 parts of the obtained polymer. The pressure-sensitive adhesive layer was prepared by adding 1 part and 3 parts of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HL) on the film which had been subjected to a release treatment.

[UV curable adhesive]
A blended mixture comprising 70 parts of ethyl acrylate, 70 parts of butyl acrylate and 40 parts of 2-hydroxyethyl acrylate was copolymerized in a toluene solution to obtain an acrylic copolymer having a number average molecular weight of 300,000. Subsequently, 43 parts of 2-methacryloyloxyethyl isocyanate was subjected to an addition reaction to the copolymer, and a carbon-carbon double bond was introduced into the polymer molecule inner chain. To 100 parts of this polymer, 0.1 part of an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) and 0.3 part of an acetophenone-based photopolymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., Irgacure 651) The pressure-sensitive adhesive layer was prepared by mixing and coating on the release-treated film. The elastic modulus after forming the pressure-sensitive adhesive layer (before irradiation) was 20 kPa, and the gel content was 25%.

  The following polymers A to F were prepared as materials (compositions) for forming the intermediate layer.

[Polymer A]
50 parts of butyl acrylate, 7 parts of acrylic acid and 50 parts of ethyl acrylate were copolymerized in toluene by a solution polymerization method to obtain a polymer. With respect to 100 parts of this polymer, 0.05 part of an isocyanate-based cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L), 15 parts of an ultraviolet curable oligomer (manufactured by Nippon Synthetic Chemical Co., Ltd., UV-1700B) and an acetophenone-based photopolymerization initiator 2 parts (Irgacure 651, manufactured by Ciba Specialty Chemicals) were added to obtain Polymer A. In addition, the elastic modulus of the polymer A after forming the intermediate layer was 10 kPa, and the gel content was 30%.

[Polymer B]
50 parts of 2-ethylhexyl acrylate, 10 parts of methacrylic acid and 30 parts of ethyl acrylate were copolymerized in toluene by a solution polymerization method to obtain a polymer. To 100 parts of this polymer, 0.5 part of an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Tetrad C), 8 parts of an ultraviolet curable oligomer (manufactured by Toagosei Co., Ltd., Aronix M270) and an acetophenone-based photopolymerization initiator (Ciba -Specialty Chemicals company make, Irgacure 651) 1.5 parts was added, and it was set as the polymer B. In addition, the elastic modulus of the polymer B after forming the intermediate layer was 700 kPa, and the gel content was 30%.

[Polymer C]
30 parts of butyl acrylate, 2 parts of acrylic acid and 30 parts of ethyl acrylate were copolymerized in toluene by a solution polymerization method to obtain a polymer. 2.4 parts of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Tetrad C) was added to 100 parts of this polymer to obtain polymer C. In addition, the elasticity modulus of the polymer C after intermediate | middle layer formation was 1000 kPa, and the gel part was 45%.

[Polymer D]
95 parts of butyl acrylate and 5 parts of acrylic acid were copolymerized in toluene by a solution polymerization method to obtain a polymer. To 100 parts of this polymer, 5 parts of a melamine-based cross-linking agent (manufactured by Dainippon Ink and Chemicals, SJ-820-60N) was added to obtain polymer D. The elastic modulus of the polymer D after forming the intermediate layer was 2000 kPa, and the gel content was 65%.

[Polymer E]
80 parts of butyl acrylate, 20 parts of ethyl acrylate and 5 parts of acrylic acid were copolymerized in toluene by a solution polymerization method to obtain a polymer. 0.02 part of an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., Tetrad C) was added to 100 parts of this polymer to obtain polymer E. In addition, the elastic modulus of the polymer E after forming the intermediate layer was 5 kPa, and the gel content was 25%.

[Polymer F]
75 parts of 2-ethylhexyl acrylate, 20 parts of acrylamide and 5 parts of acrylic acid were copolymerized in toluene by a solution polymerization method to obtain a polymer. To 100 parts of this polymer, 0.05 part of an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Tetrad C) was added to obtain polymer F. The elastic modulus of the polymer F after forming the intermediate layer was 500 kPa, and the gel content was 1%.

Example 1
An ethylene-vinyl acetate copolymer (EVA) film having a thickness of 140 μm was used as the base material layer (3), and polymer A was provided thereon with a thickness of 100 μm to form an intermediate layer (1). Further, a UV curable pressure-sensitive adhesive was provided on the intermediate layer so as to have a thickness of 5 μm, thereby forming a pressure-sensitive adhesive layer (2). This sheet was affixed to a wafer with bumps having a height of 80 μm, ground, and peeled. As a result, it was possible to work without “water intrusion”, “wafer cracking” and “wafer contamination”.

Example 2
A 200 μm-thick polyethylene (PE) film was used as the base material layer (3), and the polymer B was provided thereon with a thickness of 140 μm to form the intermediate layer (1). Further, a UV curable adhesive was provided on the intermediate layer (1) so as to have a thickness of 20 μm to form an adhesive layer (2). This sheet was affixed to a 150 μm-high wafer with bumps, ground, and peeled. As a result, it was possible to work without “water intrusion”, “wafer cracking” and “wafer contamination”.

Example 3
A polyethylene terephthalate (PET) film having a thickness of 50 μm was used as the base material layer (3), and the polymer C was provided thereon with a thickness of 200 μm to form the intermediate layer (1). Further, a UV curable pressure-sensitive adhesive was provided on the intermediate layer so as to have a thickness of 40 μm, thereby forming a pressure-sensitive adhesive layer (2). This sheet was attached to a bumped wafer having a height of 250 μm, and was ground and peeled off. As a result, it was possible to work without “water intrusion”, “wafer cracking” and “wafer contamination”.

Comparative Example 1
A polyethylene terephthalate (PET) film having a thickness of 50 μm was used as the base material layer (3), and the polymer D was provided thereon with a thickness of 100 μm to form the intermediate layer (1). Further, a pressure-sensitive adhesive was provided on the intermediate layer so as to have a thickness of 20 μm, thereby forming an adhesive layer (2). This sheet was affixed to a wafer with bumps having a height of 80 μm, ground, and peeled. As a result, since the elastic modulus of the intermediate layer was too high and hard, the bumps could not be filled and “water intrusion” occurred. “Wafer cracking” also occurred. “Wafer contamination” did not occur.

Comparative Example 2
A polyethylene terephthalate (PET) film having a thickness of 50 μm was used as the base material layer (3), and the polymer E was provided thereon with a thickness of 200 μm to form the intermediate layer (1). Further, a UV curable adhesive was provided on the intermediate layer (1) so as to have a thickness of 40 μm to form an adhesive layer (2). This sheet was affixed to a 150 μm-high wafer with bumps, ground, and peeled. As a result, the gel fraction of the intermediate layer was low and the wafer retention during grinding was poor, so that “wafer cracking” occurred during grinding. Further, peeling became difficult, resulting in “wafer contamination”.

Comparative Example 3
A polyethylene terephthalate (PET) film having a thickness of 50 μm was used as the base material layer (3), and the polymer F was provided thereon with a thickness of 200 μm to form the intermediate layer (1). Further, a UV curable adhesive was provided on the intermediate layer (1) so as to have a thickness of 40 μm to form an adhesive layer (2). This sheet was affixed to a 150 μm-high wafer with bumps, ground, and peeled. As a result, it was possible to work without “water intrusion”, “wafer cracking” and “wafer contamination”. As a result, “water intrusion” and “wafer cracking” did not occur, but due to the pressure during grinding, adhesive residue remained and “wafer contamination” occurred.

It is an example of sectional drawing of the adhesive sheet for semiconductor wafer holding | maintenance protection of this invention. It is an example of sectional drawing at the time of winding the pressure sensitive adhesive sheet for semiconductor wafer maintenance protection of the present invention in the shape of a tape. It is another example of sectional drawing at the time of winding the adhesive sheet for semiconductor wafer holding | maintenance protection of this invention in tape shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intermediate | middle layer 2 Adhesive layer 3 Base material layer 4 Peeling film layer 5 Peeling process layer

Claims (8)

At the time of semiconductor wafer processing, an adhesive sheet for holding and protecting the semiconductor wafer by sticking to the surface of the semiconductor wafer,
An intermediate layer (1) having an elastic modulus at 25 ° C. of 10 to 1000 kPa and a gel content of 26 to 45% is provided on one surface of the base material layer (3), and an adhesive is provided on the surface of the intermediate layer (1). A pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer, wherein a layer (2) is formed. The thickness t ₁ of the intermediate layer (1) is 20 to 500 μm, the thickness t _{2 of the} pressure-sensitive adhesive layer (2) is 1 to 100 μm, and the ratio is t ₂ / t ₁ = 0.01 to The pressure-sensitive adhesive sheet for holding and protecting a semiconductor wafer according to claim 1, wherein the pressure-sensitive adhesive sheet is 0.5.   The adhesive sheet for holding and protecting a semiconductor wafer according to claim 1 or 2, wherein the intermediate layer (1) contains an acrylic polymer as a constituent material.   4. The adhesive sheet for holding and protecting a semiconductor wafer according to claim 3, wherein the intermediate layer (1) further contains a radiation curable oligomer.   The adhesive sheet for holding and protecting a semiconductor wafer according to any one of claims 1 to 4, wherein the adhesive layer (2) contains an acrylic polymer as a constituent material.   6. The semiconductor wafer holding according to claim 5, wherein the pressure-sensitive adhesive layer (2) is a radiation-curable pressure-sensitive adhesive layer containing a radiation-curable acrylic polymer having a carbon-carbon double bond in the molecule. Protective adhesive sheet.   The semiconductor wafer holding according to claim 6, wherein the radiation curable pressure-sensitive adhesive layer (2) has an elastic modulus at 25 ° C of 10 to 500 kPa and a gel content of 18 to 30% before radiation curing. Protective adhesive sheet. A back surface of a semiconductor wafer in a state where the adhesive layer (2) of the adhesive sheet for holding and protecting a semiconductor wafer according to any one of claims 1 to 7 is bonded to the surface of the semiconductor wafer on the side where the circuit pattern is incorporated. A method for grinding a back surface of a semiconductor wafer, characterized in that:

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