WO2018092446A1 - Adhesive sheet for semiconductor processing - Google Patents

Abstract

The invention provides an adhesive sheet for semiconductor processing including a substrate, an intermediate layer, and an adhesive layer, in this order, wherein the intermediate layer is a layer formed from an intermediate layer forming composition comprising a non-energy ray curable acrylic polymer (A) and an energy ray curable acrylic polymer (B) having a weight average molecular weight of 50000 to 250000, the adhesive layer is energy ray curable, and the elastic modulus difference at 23°C between the intermediate layer and the adhesive layer after energy ray cure is 20 MPa or less.

Description

Adhesive sheet for semiconductor processing

The present invention relates to an adhesive sheet for semiconductor processing, and more particularly to an adhesive sheet for protecting a semiconductor wafer surface used for protecting the surface of a semiconductor wafer with bumps.

As information terminal devices are rapidly becoming thinner, smaller, and multifunctional, semiconductor devices mounted on them are also required to be thinner and denser, and semiconductor wafers are also required to be thinner. ing. Conventionally, in order to meet the demand, the back surface of a semiconductor wafer is ground and thinned. In recent years, bumps made of solder or the like having a height of about several tens to several hundreds of micrometers are sometimes formed on the surface of a semiconductor wafer. When such a semiconductor wafer with bumps is subjected to back grinding, a surface protective sheet is attached to the wafer surface on which the bumps are formed in order to protect the bump portions.

Conventionally, as disclosed in Patent Documents 1 and 2, for example, a pressure-sensitive adhesive sheet in which an intermediate layer and a pressure-sensitive adhesive layer are provided in this order on a base material is used as the surface protective sheet. In Patent Documents 1 and 2, in the intermediate layer, the elastic modulus and gel content are adjusted in order to suppress wafer contamination and to improve the followability to the unevenness of the wafer surface, which is an adherend.
Further, in Patent Documents 1 and 2, the pressure-sensitive adhesive layer is blended with an energy ray-curable oligomer, or even if a carbon-carbon double bond is introduced into the polymer constituting the pressure-sensitive adhesive, It is disclosed that it is good. The surface protective sheet is easily peeled off from the semiconductor wafer after use because the adhesive strength of the pressure-sensitive adhesive layer is reduced by irradiation with energy rays because the energy ray-curable pressure-sensitive adhesive is used.

Japanese Patent No. 4367769 Japanese Patent No. 4,369,584

However, the adhesive layer cured with energy rays may have insufficient adhesion strength with the intermediate layer. As a result, delamination may occur between the intermediate layer and the pressure-sensitive adhesive layer when the surface protective sheet is peeled off from the semiconductor wafer after energy ray curing. When delamination occurs, for example, when the surface protective sheet is peeled off, the adhesive may remain on the semiconductor wafer, which may cause wafer contamination.
The present invention has been made in view of the above circumstances, and prevents the delamination that occurs between the intermediate layer and the pressure-sensitive adhesive layer when the semiconductor processing pressure-sensitive adhesive sheet is cured and peeled from the workpiece. Let it be an issue.

As a result of intensive studies, the present inventors have determined that both the intermediate layer and the pressure-sensitive adhesive layer have a predetermined composition having energy beam curability and that the difference in elastic modulus after curing these energy beams is a certain value or less. The inventors have found that the above problems can be solved, and have completed the following present invention. The present invention provides the following (1) to (8).
(1) A pressure-sensitive adhesive sheet for semiconductor processing comprising a substrate, an intermediate layer, and a pressure-sensitive adhesive layer in this order,
The intermediate layer contains a non-energy ray curable acrylic polymer (A) and an energy ray curable acrylic polymer (B) having a weight average molecular weight of 50,000 to 250,000. A layer formed from the composition, and the pressure-sensitive adhesive layer is energy ray curable,
A pressure-sensitive adhesive sheet for semiconductor processing, wherein the difference in elastic modulus at 23 ° C. between the intermediate layer and the pressure-sensitive adhesive layer after energy ray curing is 20 MPa or less.
(2) The semiconductor processing according to (1), wherein in the composition for forming an intermediate layer, the acrylic polymer (B) is less than 25 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). Adhesive sheet.
(3) The pressure-sensitive adhesive sheet for semiconductor processing according to the above (1) or (2), wherein the acrylic polymer (A) has a weight average molecular weight of 300,000 to 1,500,000.
(4) The semiconductor processing according to any one of (1) to (3), wherein the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing an energy ray-curable acrylic polymer (C). Adhesive sheet.
(5) The acrylic polymer (C) comprises a structural unit derived from an alkyl (meth) acrylate (c1) having an alkyl group having 1 to 18 carbon atoms and a structural unit derived from a functional group-containing monomer (c2). The semiconductor according to (4), which is an acrylic copolymer (C1), which is a reaction product obtained by reacting an acrylic copolymer (C0) having a polymerizable compound (Xc) having an energy ray polymerizable group. Processing adhesive sheet.
(6) The pressure-sensitive adhesive sheet for semiconductor processing according to (4) or (5), wherein the acrylic polymer (C) has a weight average molecular weight of 100,000 to 1,500,000.
(7) The intermediate layer forming composition contains 0.3 to 15 parts by mass of a photopolymerization initiator with respect to 100 parts by mass of the acrylic polymer (A), and the pressure-sensitive adhesive composition comprises: The pressure-sensitive adhesive sheet for semiconductor processing according to any one of the above (4) to (6), comprising 0.5 to 15 parts by mass of a photopolymerization initiator with respect to 100 parts by mass of the acrylic polymer (C). .
(8) The acrylic polymer (B) comprises a structural unit derived from an alkyl (meth) acrylate (b1) having an alkyl group having 1 to 18 carbon atoms and a structural unit derived from a functional group-containing monomer (b2). The above-mentioned (1) to (7), which are acrylic copolymers (B1), which are reaction products obtained by reacting an acrylic copolymer (B0) having a polymerizable compound (Xb) having an energy ray polymerizable group. The adhesive sheet for semiconductor processing according to any one of the above.

In the present invention, it is possible to prevent delamination that occurs between the intermediate layer and the pressure-sensitive adhesive layer when the pressure-sensitive adhesive sheet for semiconductor processing is cured with energy rays and peeled from the workpiece.

In the following description, “weight average molecular weight (Mw)” is a value in terms of polystyrene measured by gel permeation chromatography (GPC), and specifically measured based on the method described in the examples. Value.
In the description of the present specification, for example, “(meth) acrylate” is used as a word indicating both “acrylate” and “methacrylate”, and the same applies to other similar terms.

Hereinafter, the present invention will be described in more detail using embodiments.
The pressure-sensitive adhesive sheet for semiconductor processing of the present invention (hereinafter also simply referred to as “pressure-sensitive adhesive sheet”) includes a base material, an intermediate layer provided on one surface of the base material, and an adhesive layer further provided on the intermediate layer And have. Further, the pressure-sensitive adhesive sheet may be further provided with a release material on the pressure-sensitive adhesive layer. The release material protects the pressure-sensitive adhesive layer and is removed from the pressure-sensitive adhesive layer when the pressure-sensitive adhesive sheet is attached to the workpiece.
The pressure-sensitive adhesive sheet may have layers other than those described above. For example, in order to improve the adhesion between the intermediate layer and the base material, an easy adhesion layer formed of various curable resins or the like may be provided on one surface of the base material. In order to prevent charging of the pressure-sensitive adhesive sheet, an antistatic layer containing a known antistatic agent may be provided on one surface of the substrate.

The intermediate layer is a composition for forming an intermediate layer containing a non-energy ray curable acrylic polymer (A) and an energy ray curable acrylic polymer (B) having a weight average molecular weight of 50,000 to 250,000. It is a layer formed from an object. The pressure-sensitive adhesive layer is a layer formed of an energy ray-curable pressure-sensitive adhesive composition. And the elastic modulus difference in 23 degreeC of the intermediate | middle layer after energy-beam hardening and the adhesive layer after energy-beam hardening will be 20 Mpa or less. The elastic modulus at 23 ° C. is the value of the storage elastic modulus at 23 ° C. when the storage elastic modulus at −30 to 200 ° C. is measured with a viscoelasticity measuring device at a rate of temperature increase of 3 ° C./min (frequency: 1 Hz). Specifically, it is a value measured based on the method described in the examples.
In the present invention, both the intermediate layer and the pressure-sensitive adhesive layer are energy ray curable. Therefore, when the pressure-sensitive adhesive sheet attached to the adherend is irradiated with energy rays, the intermediate layer and the pressure-sensitive adhesive layer are cured to reduce the adhesive force to the adherend, and are easily peeled off from the adherend. It becomes like this. Moreover, since the difference in elastic modulus between the intermediate layer and the pressure-sensitive adhesive layer after energy beam curing is small, it is possible to prevent delamination between the intermediate layer and the pressure-sensitive adhesive layer when the pressure-sensitive adhesive sheet is peeled off.

On the other hand, when the elastic modulus difference exceeds 20 MPa, the interlayer strength between the intermediate layer and the pressure-sensitive adhesive layer becomes low when cured by energy rays. Therefore, when the pressure-sensitive adhesive sheet is peeled from the adherend after curing with energy rays, delamination is likely to occur between the intermediate layer and the pressure-sensitive adhesive layer. From the viewpoint of improving the interlayer strength between the intermediate layer and the pressure-sensitive adhesive layer and more effectively suppressing delamination, the difference in elastic modulus is preferably 15 MPa or less, and more preferably 8 MPa or less.
Further, from the viewpoint of suppressing delamination, the above elastic modulus difference should be low. However, in order to provide each of the intermediate layer and the adhesive layer with a desired function, the elastic modulus difference should be 0.1 MPa or more. Preferably, it is 0.5 MPa or more.

Hereinafter, each layer which comprises an adhesive sheet is demonstrated in detail.
<Intermediate layer>
In the pressure-sensitive adhesive sheet, the intermediate layer is a layer provided between the pressure-sensitive adhesive layer and the substrate. The intermediate layer may be formed directly on the base material. However, as described above, when other layers such as an easy adhesion layer and an antistatic layer are provided on the base material, Formed on top.
As described above, the intermediate layer contains the non-energy ray curable acrylic polymer (A) and the energy ray curable acrylic polymer (B) having a weight average molecular weight of 50,000 to 250,000. It is a layer formed from the composition for forming an intermediate layer. Hereinafter, the acrylic polymer (A) may be simply referred to as “component (A)”. The same applies to the other components.
The intermediate layer exhibits cohesive force by the component (A) and expresses stress relaxation properties by the component (B) having a low molecular weight. The pressure-sensitive adhesive sheet having such an intermediate layer has high holding performance with respect to the adherend, such as good followability with respect to the adherend having unevenness. Therefore, when grinding a wafer or the like to which an adhesive sheet has been attached, it becomes possible to prevent the wafer from being damaged or grinding waste or grinding water from entering the wafer surface.

The elastic modulus at 23 ° C. after energy beam curing of the intermediate layer is preferably 0.5 to 40 MPa, more preferably 1.0 to 30 MPa, and further preferably 1.5 to 20 MPa. Since the intermediate layer has such an elastic modulus, the above-described difference in elastic modulus can be easily reduced while sufficiently exhibiting the function as the intermediate layer before irradiation with energy rays. Moreover, it becomes easy to make interlayer intensity | strength higher by making an elasticity modulus into these ranges.

The elastic modulus at 23 ° C. of the intermediate layer after energy beam curing may be lower than or higher than the elastic modulus at 23 ° C. of the pressure-sensitive adhesive layer after energy beam curing.
In addition, the elastic modulus at 23 ° C. after the energy ray curing of the intermediate layer is, for example, the blending amount of the acrylic polymer (B) or the amount of the energy ray polymerizable group introduced into the acrylic polymer (B) ( The value can be adjusted according to the value of α described later. For example, when the blending amount of the acrylic polymer (B) and the amount of the energy beam polymerizable group are increased, the elastic modulus tends to increase. Moreover, it can adjust suitably also with the kind and quantity of the monomer which comprises an acrylic polymer (A), also the quantity of the crosslinking agent mix | blended with an intermediate | middle layer, the quantity of a photoinitiator, etc.

[Acrylic polymer (A)]
The acrylic polymer (A) is a non-energy ray curable polymer having a structural unit derived from (meth) acrylate. The acrylic polymer (A) preferably includes an acrylic copolymer (A1) having a structural unit derived from the alkyl (meth) acrylate (a1) and a structural unit derived from the functional group-containing monomer (a2). More preferably, the acrylic copolymer (A1) is used.
The form of copolymerization of the acrylic copolymer (A1) is not particularly limited, and may be a block copolymer or a random copolymer. The content of the acrylic copolymer (A1) is preferably 70 to 100% by mass, more preferably based on the total amount (100% by mass) of the component (A) contained in the intermediate layer forming composition. Is 80 to 100% by mass, more preferably 90 to 100% by mass, and still more preferably 100% by mass.

As the alkyl (meth) acrylate (a1), an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms is used. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) ) Acrylate and the like. Alkyl (meth) acrylate (a1) may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the structural unit derived from the alkyl (meth) acrylate (a1) in the acrylic copolymer (A1) is preferably based on the total structural unit (100% by mass) of the acrylic copolymer (A1). It is 50 to 99.5% by mass, more preferably 60 to 99% by mass, still more preferably 70 to 97% by mass, and still more preferably 80 to 95% by mass.
When the content is 50% by mass or more, the holding performance of the pressure-sensitive adhesive sheet is improved, and the followability to an adherend having a large unevenness is easily improved. Moreover, if it is 99.5 mass% or less, the structural unit derived from (a2) component can be ensured more than a fixed amount.

Among the above, the alkyl (meth) acrylate (a1) is preferably an alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms in order to obtain an appropriate value for the elastic modulus of the intermediate layer. More preferably, the group contains an alkyl (meth) acrylate having 4 to 8 carbon atoms (hereinafter sometimes referred to as a monomer (Y)). As the monomer (Y), specifically, 2-ethylhexyl (meth) acrylate and n-butyl (meth) acrylate are preferable, and n-butyl (meth) acrylate is particularly preferable.
Here, all of the alkyl (meth) acrylate (a1) constituting the acrylic copolymer (A1) may be the monomer (Y) or a part thereof may be the monomer (Y). Specifically, the monomer (Y) is preferably 75 to 100% by mass, more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass based on the total amount of the alkyl (meth) acrylate (a1).

The functional group-containing monomer (a2) is a monomer having a functional group such as a hydroxy group, a carboxy group, an epoxy group, an amino group, a cyano group, a nitrogen atom-containing cyclic group, or an alkoxysilyl group. Among the above-described functional group-containing monomers (a2), one or more selected from hydroxy group-containing monomers, carboxy group-containing monomers, and epoxy group-containing monomers are preferable.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl ( Examples thereof include hydroxyalkyl (meth) acrylates such as meth) acrylate and 4-hydroxybutyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol.
Examples of the carboxy group-containing monomer include (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid.

Examples of the epoxy-containing monomer include an epoxy group-containing (meth) acrylic acid ester and a non-acrylic epoxy group-containing monomer. Examples of the epoxy group-containing (meth) acrylic acid ester include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, (3,4-epoxycyclohexyl) methyl (meth) acrylate, and 3-epoxycyclo-2- Hydroxypropyl (meth) acrylate etc. are mentioned. Examples of the non-acrylic epoxy group-containing monomer include glycidyl crotonate and allyl glycidyl ether.
A functional group containing monomer (a2) may be used individually by 1 type, and may be used in combination of 2 or more type.
Among the functional group-containing monomers (a2), carboxy group-containing monomers are more preferable, among which (meth) acrylic acid is more preferable, and acrylic acid is most preferable. When a carboxy group-containing monomer is used as the functional group-containing monomer (a2), the cohesive force of the intermediate layer is increased, and the retention performance and the like of the intermediate layer are easily improved.

The content of the structural unit derived from the functional group-containing monomer (a2) in the acrylic copolymer (A1) is preferably 0 with respect to all the structural units (100% by mass) of the acrylic copolymer (A1). 5 to 40% by mass, more preferably 1 to 30% by mass, still more preferably 3 to 20% by mass, and still more preferably 5 to 15% by mass.
When the content of the structural unit derived from the component (a2) is 0.5% by mass or more, the cohesive force of the intermediate layer is increased, and the compatibility with the component (B) is easily improved. On the other hand, if content is 40 mass% or less, the structural unit derived from (a1) component can be ensured more than a fixed amount.

The acrylic copolymer (A1) may be a copolymer of an alkyl (meth) acrylate (a1) and a functional group-containing monomer (a2), but the (a1) component, the (a2) component, and these It may be a copolymer with another monomer (a3) other than the components (a1) and (a2).
Examples of the other monomer (a3) include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentenyloxy. Examples thereof include (meth) acrylate having a cyclic structure such as ethyl (meth) acrylate, vinyl acetate, and styrene. Another monomer (a3) may be used individually by 1 type, and may be used in combination of 2 or more type.
The content of the structural unit derived from the other monomer (a3) in the acrylic copolymer (A1) is preferably from 0 to the total structural unit (100% by mass) of the acrylic copolymer (A1). It is 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 10% by mass, and still more preferably 0 to 5% by mass.

The weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 300,000 to 1,500,000, more preferably 400,000 to 1,200,000, still more preferably 400,000 to 1,100,000, still more preferably 450,000 to 90. It is ten thousand. By making Mw below these upper limit values, the acrylic polymer (A) has good compatibility with the acrylic polymer (B). Moreover, it becomes easy to improve the holding | maintenance performance of an adhesive sheet by making Mw into the said range.
The content of the acrylic polymer (A) in the intermediate layer forming composition is preferably 60 to 99% by weight, more preferably 70 to 70% by weight based on the total amount (100% by weight) of the intermediate layer forming composition. It is 97% by mass, more preferably 75 to 92% by mass or more.
When the intermediate layer forming composition is diluted with a diluent such as an organic solvent as will be described later, the total amount of the intermediate layer forming composition means the total solid content excluding the diluted solution. . The same applies to the pressure-sensitive adhesive composition described later.

[Acrylic polymer (B)]
The acrylic polymer (B) is an acrylic polymer having energy ray curability by introducing an energy ray polymerizable group. The acrylic polymer (B) has a weight average molecular weight (Mw) of 50,000 to 250,000. In the present invention, by using the component (B) in the intermediate layer, it is considered that when the energy beam is irradiated, the component (B) and the energy beam curing component in the pressure-sensitive adhesive layer react and bond. Therefore, combined with the small elastic modulus difference, the interlayer strength between the intermediate layer and the pressure-sensitive adhesive layer after energy ray curing is improved.

If the Mw of the acrylic polymer (B) is less than 50,000, when the pressure-sensitive adhesive sheet is stored for a long time, a part of the component (B) moves into the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive force of the pressure-sensitive adhesive sheet is unstable. In addition, the pressure-sensitive adhesive layer may be excessively cured after energy beam irradiation. As a result, the pressure-sensitive adhesive sheet has an interlayer strength between the intermediate layer and the pressure-sensitive adhesive layer after irradiation with energy rays, for example, when used after long-term storage or when left for a long time in a state of being stuck to an adherend. It may be insufficient. Moreover, also when Mw of (B) component exceeds 250,000, the interlayer intensity | strength of the intermediate | middle layer and adhesive layer after energy ray irradiation becomes easy to fall.
From the above viewpoints, the weight average molecular weight (Mw) of the acrylic polymer (B) is preferably 60,000 to 220,000, more preferably 70,000 to 200,000, still more preferably 80,000 to 180,000, and even more preferably. Is 850,000 to 150,000.

The acrylic polymer (B) is an acrylic polymer having a structural unit derived from (meth) acrylate and having an energy ray polymerizable group introduced therein. The energy ray polymerizable group of the acrylic polymer (B) is preferably introduced into the side chain of the acrylic polymer. The energy ray polymerizable group may be any group containing an energy ray polymerizable carbon-carbon double bond, and examples thereof include a (meth) acryloyl group and a vinyl group. Among them, a (meth) acryloyl group is preferable. .

The acrylic polymer (B) is energy beam polymerized into an acrylic copolymer (B0) having a structural unit derived from the alkyl (meth) acrylate (b1) and a structural unit derived from the functional group-containing monomer (b2). The acrylic copolymer (B1), which is a reaction product obtained by reacting the polymerizable compound (Xb) having a functional group, is preferably included, and the acrylic copolymer (B1) is more preferable.
The form of copolymerization of the acrylic copolymer (B0) is not particularly limited, and may be any of a block copolymer, a random copolymer, and the like. The content of the acrylic copolymer (B1) is preferably 70 to 100% by mass, more preferably 80% with respect to the total amount (100% by mass) of the component (B) contained in the intermediate layer forming composition. To 100% by mass, more preferably 90 to 100% by mass, and still more preferably 100% by mass.

As the alkyl (meth) acrylate (b1), an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms is used, and specific examples thereof include those exemplified as the component (a1). They may be used alone or in combination of two or more.
The content of the structural unit derived from the alkyl (meth) acrylate (b1) in the acrylic copolymer (B0) is preferably based on the total structural unit (100% by mass) of the acrylic copolymer (B0). It is 50 to 95% by mass, more preferably 55 to 90% by mass, still more preferably 60 to 85% by mass, and still more preferably 65 to 80% by mass. When the content is 50% by mass or more, the shape of the formed intermediate layer can be sufficiently maintained. Moreover, if it is 95 mass% or less, the fixed quantity of the structural unit derived from the (b2) component used as the reaction point with polymeric compound (Xb) is securable.

Further, like the component (a1), the alkyl (meth) acrylate (b1) is preferably an alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, and further, the monomer (Y) (ie, More preferably, the alkyl group contains an alkyl (meth) acrylate having 4 to 8 carbon atoms. A suitable compound as the monomer (Y) is the same as the above (a1), and n-butyl (meth) acrylate is particularly preferable.
Here, all of the alkyl (meth) acrylate (b1) contained in the acrylic copolymer (B0) may be the monomer (Y), but it is preferable that a part thereof is the monomer (Y). . The monomer (Y) is preferably 65 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 80 to 95% by mass with respect to the total amount of the alkyl (meth) acrylate (b1).

Examples of the functional group-containing monomer (b2) include monomers having the functional groups exemplified in the above-described functional group-containing monomer (a2), and one selected from a hydroxy group-containing monomer, a carboxy group-containing monomer, and an epoxy group-containing monomer. More than species are preferred. As these specific compounds, the same compounds as those exemplified as the component (a2) can be exemplified.
The functional group-containing monomer (b2) is preferably a hydroxy group-containing monomer, and more preferably various hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate. By using hydroxyalkyl (meth) acrylate, it becomes possible to react the polymerizable compound (Xb) with the acrylic copolymer (B0) relatively easily.

The functional group-containing monomer (a2) used for the acrylic polymer (A) and the functional group-containing monomer (b2) used for the acrylic polymer (B) are the same as each other. Or different, but preferably different. That is, for example, if the functional group-containing monomer (a2) is a carboxy group-containing monomer, the functional group-containing monomer (b2) is preferably a hydroxyl group-containing monomer. Thus, when the functional groups are different from each other, for example, the acrylic polymer (B) can be preferentially cross-linked by a cross-linking agent described later, and the holding performance of the above-described pressure-sensitive adhesive sheet can be improved. It becomes easier to make better.

The content of the structural unit derived from the functional group-containing monomer (b2) in the acrylic copolymer (B0) is preferably 5 with respect to the total structural unit (100% by mass) of the acrylic copolymer (B0). -50% by mass, more preferably 10-45% by mass, still more preferably 15-40% by mass, and still more preferably 20-35% by mass. If it is 5 mass% or more, a relatively large number of reaction points with the polymerizable compound (Xb) can be secured, and the energy polymerizable property can be easily introduced into the side chain. Moreover, if it is 50 mass% or less, the shape of the intermediate | middle layer formed can be fully maintained.

The acrylic copolymer (B0) may be a copolymer of an alkyl (meth) acrylate (b1) and a functional group-containing monomer (b2), but the (b1) component, the (b2) component, and these It may be a copolymer with another monomer (b3) other than the components (b1) and (b2).
Examples of the other monomer (b3) include those exemplified as the monomer (a3) described above.
The content of the structural unit derived from the other monomer (b3) in the acrylic copolymer (B0) is preferably from 0 to the total structural unit (100% by mass) of the acrylic copolymer (B0). It is 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 10% by mass, and still more preferably 0 to 5% by mass.

The polymerizable compound (Xb) includes an energy ray polymerizable group and a substituent that can react with a functional group in the structural unit derived from the component (b2) of the acrylic copolymer (B0) (hereinafter simply referred to as “reactive substitution”). And a group also referred to as “group”.
Examples of the energy beam polymerizable group include a (meth) acryloyl group and a vinyl group as described above, and a (meth) acryloyl group is preferable. The polymerizable compound (Xb) is preferably a compound having 1 to 5 energy beam polymerizable groups per molecule.
The reactive substituent in the polymerizable compound (Xb) may be appropriately changed according to the functional group of the functional group-containing monomer (b2), and examples thereof include an isocyanate group, a carboxyl group, and an epoxy group. From the viewpoint of reactivity and the like, an isocyanate group is preferable. When the polymerizable compound (Xb) has an isocyanate group, for example, when the functional group of the functional group-containing monomer (b2) is a hydroxy group, it can easily react with the acrylic copolymer (B0). become.

Specific examples of the polymerizable compound (Xb) include (meth) acryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth) acryloyl isocyanate, allyl isocyanate, glycidyl (meth) acrylate, Examples include (meth) acrylic acid. These polymerizable compounds (Xb) may be used alone or in combination of two or more.
Among these, (meth) acryloyloxyethyl is a compound having an isocyanate group suitable as the reactive substituent and having an appropriate distance between the main chain and the energy beam polymerizable group. Isocyanates are preferred.
The polymerizable compound (Xb) is preferably 40 to 98 equivalents, more preferably 50 to 95 equivalents, out of the total amount (100 equivalents) of the functional group derived from the functional group-containing monomer (b2) in the acrylic copolymer (B1). More preferably, 60 to 90 equivalents, still more preferably 70 to 85 equivalents are reacted with the functional group.

The value of α calculated from the following formula (1) serves as an index representing the number of energy beam polymerizable groups of the acrylic copolymer (B1). In the acrylic polymer (B1), the value of α is preferably 5 to 40, more preferably 10 to 35, and still more preferably 15 to 30.
By using the acrylic copolymer (B1) having such a value of α in a blending amount described later, the elastic modulus of the intermediate layer can be easily adjusted to a desired range.
Formula (1): α = [P _b ] × [Q _b ] × [R _b ] / 100
(In the formula (1), [P _b] indicates the content of the constitutional unit derived from functional group-containing monomer (b2) to all the structural units 100 parts by weight of the acrylic copolymer (B0). [Q _b] Represents the equivalent of the polymerizable compound (Xb) to 100 equivalents of the functional group derived from the functional group-containing monomer (b2) of the acrylic copolymer (B0), wherein [R _b ] represents the polymerizable compound (Xb). Indicates the number of energy ray polymerizable groups possessed by.

In the composition for forming an intermediate layer, the content of the acrylic polymer (B) is preferably less than 25 parts by mass with respect to 100 parts by mass of the acrylic polymer (A), and is 1 to 24 parts by mass. More preferably, it is more preferably 8 to 23 parts by mass. By relatively reducing the content of the component (B) as described above, the stress relaxation property of the intermediate layer is improved, and the intermediate layer having high unevenness followability is obtained.
In addition, if the content of the acrylic polymer (B) is reduced, the elastic modulus of the intermediate layer after energy ray curing does not increase so much, so the above difference in elastic modulus can be reduced and delamination is prevented. It becomes easy to be done.

[Crosslinking agent]
The intermediate layer forming composition preferably further contains a crosslinking agent. Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a metal chelate crosslinking agent. Among these, an isocyanate crosslinking agent is preferable. When an isocyanate-based crosslinking agent is used, for example, when the component (B) has a hydroxy group, the crosslinking agent preferentially crosslinks the acrylic polymer (B).
The composition for forming an intermediate layer is crosslinked by a crosslinking agent, for example, by being heated after coating. The intermediate layer is cross-linked with an acrylic polymer, particularly a low molecular weight acrylic polymer (B), so that a coating film is appropriately formed, and the intermediate layer can easily function as an intermediate layer.
The content of the crosslinking agent is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and further preferably 1 to 5 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). It is.

Examples of the isocyanate-based crosslinking agent include polyisocyanate compounds. Specific examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Etc. Further, biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with a low molecular active hydrogen-containing compound such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, and the like are also included.
These may be used individually by 1 type and may be used in combination of 2 or more type. Of the above, polyhydric alcohols of aromatic polyisocyanates such as tolylene diisocyanate (for example, trimethylolpropane) adducts are preferred.

Examples of the epoxy crosslinking agent include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, and ethylene glycol. Examples include diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidyl amine. These may be used individually by 1 type and may be used in combination of 2 or more type.
Examples of the metal chelate crosslinking agent include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, zirconium, acetylacetone, ethyl acetoacetate, tris (2, 4 -Pentandionate) and the like are exemplified. These may be used individually by 1 type and may be used in combination of 2 or more type.
Examples of the aziridine-based crosslinking agent include diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethanetri-β-aziridinyl. Propionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tris-1- (2-methylaziridine) phosphine, And trimethylolpropane tri-β- (2-methylaziridine) propionate, hexa [1- (2-methyl) -aziridinyl] triphosphatriazine, and the like.

[Photopolymerization initiator]
The intermediate layer forming composition preferably further contains a photopolymerization initiator. When the composition for forming an intermediate layer contains a photopolymerization initiator, energy ray curing by ultraviolet rays or the like of the composition for forming an intermediate layer is facilitated.
Examples of the photopolymerization initiator include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin Isobutyl ether, benzyldiphenisulphide, tetramethylthiuram monosulfide, benzyldimethyl ketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2-diphenylethane 1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1,2-benzene Dil-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, diethylthioxanthone, isopropylthioxanthone, 2,4,6- Low molecular weight polymerization initiators such as trimethylbenzoyldiphenyl-phosphine oxide, oligomerized polymerization initiators such as oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone}, etc. Is mentioned. These may be used alone or in combination of two or more. Of these, 1-hydroxycyclohexyl phenyl ketone is preferred.
The content of the photopolymerization initiator is usually 0.3 to 15 parts by mass with respect to 100 parts by mass of the acrylic polymer (A), but even a small content of the acrylic polymer (B) is sufficient. In order to facilitate the increase of the elastic modulus of the intermediate layer after curing as the curing proceeds, the content should be relatively increased, preferably 1 to 10 parts by mass, more preferably 3 to 8 parts by mass.

The composition for forming an intermediate layer may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, tackifiers, and the like. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.01 to 2 parts per 100 parts by mass of the acrylic polymer (A). Part by mass.
The thickness of the intermediate layer may be appropriately selected according to, for example, the height of bumps formed on the semiconductor wafer as the adherend, but is preferably 10 to 800 μm, more preferably 15 to 600 μm. More preferably, the thickness is 20 to 500 μm.

<Adhesive layer>
In the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer is a layer formed on the intermediate layer, and the pressure-sensitive adhesive sheet is attached to the adherend by the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is usually formed directly on the intermediate layer. The adhesive layer is an energy ray curable layer as described above. The pressure-sensitive adhesive sheet has a high adhesive strength that can sufficiently hold the workpiece before irradiation with energy rays, but after irradiation with energy rays, the pressure-sensitive adhesive layer is cured and the adhesive strength is reduced, and is an adherend. It can be easily peeled off from a wafer or the like.

The elastic modulus at 23 ° C. after the energy ray curing of the pressure-sensitive adhesive layer is preferably 1 to 60 MPa, more preferably 1.5 to 30 MPa, and further preferably 1.8 to 12 MPa. An adhesive layer makes it easy to make an above-mentioned elastic modulus difference small by making the elasticity modulus after energy ray hardening into such a range. Moreover, it becomes easy to express suitable adhesiveness as an adhesive layer before energy ray irradiation. Furthermore, it becomes easy to make interlayer intensity | strength higher by making an elastic modulus into these ranges.

The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer includes, for example, an acrylic polymer, polyurethane, rubber-based polymer, polyolefin, silicone, and the like as a pressure-sensitive adhesive component (pressure-sensitive resin) that can exhibit pressure-sensitive adhesive properties. contains. In these, an acrylic polymer is preferable.
The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer may have energy ray-curing properties by blending an energy ray-curable compound separately from the pressure-sensitive resin, but the above-mentioned pressure-sensitive adhesive resin itself is an energy ray. It preferably has curability. When the adhesive resin itself has energy ray curability, the energy ray polymerizable group is introduced into the adhesive resin, but the energy ray polymerizable group is preferably introduced into the main chain or side chain of the adhesive resin. .

When an energy ray curable compound is blended separately from the adhesive resin, a monomer or oligomer having an energy ray polymerizable group is used as the energy ray curable compound. The oligomer is an oligomer having a weight average molecular weight (Mw) of less than 10,000, and examples thereof include urethane (meth) acrylate. In addition, even if it is a case where adhesive resin itself has energy-beam sclerosis | hardenability, an energy-beam curable compound may be mix | blended with an adhesive composition other than adhesive resin.

Hereinafter, the case where the energy ray-curable adhesive resin contained in the adhesive composition is an acrylic polymer (hereinafter, also referred to as “acrylic polymer (C)”) will be described in more detail.
[Acrylic polymer (C)]
The acrylic polymer (C) is an acrylic polymer having a structural unit derived from (meth) acrylate and having an energy ray polymerizable group introduced therein. The energy beam polymerizable group is preferably introduced into the side chain of the acrylic polymer.
The acrylic polymer (C) is energy beam polymerized into an acrylic copolymer (C0) having a structural unit derived from the alkyl (meth) acrylate (c1) and a structural unit derived from the functional group-containing monomer (c2). It preferably contains an acrylic copolymer (C1), which is a reaction product obtained by reacting a polymerizable compound (Xc) having a functional group, and more preferably comprises this acrylic copolymer (C1).
The form of copolymerization of the acrylic copolymer (C0) is not particularly limited, and may be any of a block copolymer and a random copolymer. The content of the acrylic copolymer (C1) is preferably 70 to 100% by mass, more preferably 80 to 100%, based on the total amount (100% by mass) of the component (C) contained in the pressure-sensitive adhesive composition. % By mass, more preferably 90 to 100% by mass, and still more preferably 100% by mass.

As the alkyl (meth) acrylate (c1), an alkyl (meth) acrylate having an alkyl group having 1 to 18 carbon atoms is used, and specific examples thereof include those exemplified as the component (a1). May be used individually by 1 type, and may be used in combination of 2 or more type.
The content of the structural unit derived from the alkyl (meth) acrylate (c1) in the acrylic copolymer (C0) is from the viewpoint of improving the adhesive strength of the pressure-sensitive adhesive layer to be formed, and the acrylic copolymer (C0). Is preferably 50 to 99% by mass, more preferably 60 to 98% by mass, still more preferably 70 to 97% by mass, and still more preferably 80 to 96% by mass, with respect to all the structural units (100% by mass). .

In addition, the alkyl (meth) acrylate (c1) is preferably an alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, as in the components (a1) and (b1). It is more preferable to contain an alkyl (meth) acrylate having 4 to 8 carbon atoms (that is, monomer (Y)). A suitable compound used as the monomer (Y) is the same as the above (a1) and (b1), and n-butyl (meth) acrylate is particularly preferable.
Here, all of the alkyl (meth) acrylate (c1) may be the monomer (Y), but in order to suitably adjust the adhesive performance and elastic modulus of the adhesive layer, a part of the monomer (Y) It is preferable that Specifically, the monomer (Y) is preferably 65 to 98% by mass, more preferably 70 to 95% by mass, and further preferably 75 to 90% by mass with respect to the total amount of the alkyl (meth) acrylate (c1).

For example, the alkyl (meth) acrylate (c1) may contain ethyl (meth) acrylate in addition to the monomer (Y) described above. When ethyl (meth) acrylate is used, it becomes easy to lower the elastic modulus of the pressure-sensitive adhesive layer even after energy ray curing, and it becomes easy to reduce the difference in elastic modulus from the intermediate layer. Moreover, it becomes easy to adjust the adhesive performance of the adhesive layer to a desired one.
Further, the alkyl (meth) acrylate (c1) may contain methyl (meth) acrylate in addition to the monomer (Y) or the monomer (Y) and ethyl (meth) acrylate. By containing methyl (meth) acrylate, it becomes easy to adjust the adhesive performance of the adhesive layer to a desired one.

The total amount of ethyl (meth) acrylate and methyl (meth) acrylate is preferably 2 to 35% by mass, more preferably 5 to 30% by mass, based on the total amount of alkyl (meth) acrylate (c1). More preferred is ˜25% by mass.
The ethyl (meth) acrylate is preferably 2 to 30% by mass, more preferably 5 to 25% by mass, and still more preferably 10 to 20% by mass with respect to the total amount of the alkyl (meth) acrylate (c1).

Examples of the functional group-containing monomer (c2) include monomers having the functional groups exemplified as the functional group-containing monomer (a2). Specifically, the functional group-containing monomer (c2) includes a hydroxy group-containing monomer, a carboxy group-containing monomer, and an epoxy group-containing monomer. One or more selected from monomers are preferred. As these specific compounds, the same compounds as those exemplified as the component (a2) can be exemplified.

Among the above-mentioned functional group-containing monomers (c2), hydroxy group-containing monomers are more preferable, among which hydroxyalkyl (meth) acrylates are more preferable, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) Acrylates are more preferred, and 4-hydroxybutyl (meth) acrylate is particularly preferred.
By using hydroxyalkyl (meth) acrylate as the component (c2), the polymerizable compound (Xc) can be reacted with the acrylic copolymer (C0) relatively easily. Further, when 4-hydroxybutyl (meth) acrylate is used, the tensile strength of the intermediate layer is increased, and it is easy to prevent adhesive residue.

The content of the structural unit derived from the functional group-containing monomer (c2) in the acrylic copolymer (C0) is preferably 1 with respect to the total structural units (100% by mass) of the acrylic copolymer (C0). It is -40% by mass, more preferably 2-30% by mass, still more preferably 3-25% by mass, and still more preferably 4-15% by mass.
If content is 1 mass% or more, a fixed quantity of functional groups used as the reaction point with polymeric compound (Xc) can be ensured. Therefore, since the pressure-sensitive adhesive layer can be appropriately cured by irradiation with energy rays, it becomes possible to reduce the adhesive strength after irradiation with energy rays. Furthermore, it becomes easy to improve the interlayer strength after energy beam irradiation between the pressure-sensitive adhesive layer and the intermediate layer. Moreover, if content is 40 mass% or less, when apply | coating the solution of an adhesive composition and forming an adhesive layer, sufficient pot life can be ensured.

The acrylic copolymer (C0) may be a copolymer of an alkyl (meth) acrylate (c1) and a functional group-containing monomer (c2), but the (c1) component, the (c2) component, and these It may be a copolymer with another monomer (c3) other than the components (c1) and (c2).
Examples of the other monomer (c3) include those exemplified as the monomer (a3) described above.
The content of the structural unit derived from the other monomer (c3) in the acrylic copolymer (C0) is preferably from 0 to the total structural unit (100% by mass) of the acrylic copolymer (C0). It is 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 10% by mass, and still more preferably 0 to 5% by mass.

The polymerizable compound (Xc) reacts with the functional group in the structural unit derived from the component (c2) of the acrylic copolymer (C0) in the same manner as the polymerizable compound (Xb) described above. And a compound having 1 to 5 energy beam polymerizable groups per molecule.
Specific examples of the reactive substituent and the energy ray polymerizable group are the same as those of the polymerizable compound (Xb). Therefore, the reactive substituent is preferably an isocyanate group, and the energy ray polymerizable group is a (meth) acryloyl group. preferable.
Specific examples of the polymerizable compound (Xc) include those exemplified as the above-described polymerizable compound (Xb), and (meth) acryloyloxyethyl isocyanate is preferable. In addition, you may use polymeric compound (Xc) individually or in combination of 2 or more types.
The polymerizable compound (Xc) is preferably 30 to 98 equivalents, more preferably 40 to 95 equivalents, out of the total amount (100 equivalents) of the functional group derived from the functional group-containing monomer (c2) in the acrylic copolymer (C0). More preferably, 50 to 92 equivalents, still more preferably 80 to 92 equivalents are reacted with the functional group.

The weight average molecular weight (Mw) of the acrylic polymer (C) is preferably 100,000 to 1,500,000, more preferably 250,000 to 1,000,000, still more preferably 300,000 to 900,000, still more preferably 350,000 to 80 It is ten thousand. By having such Mw, it becomes possible to give suitable adhesiveness to an adhesive layer.
The content of the acrylic polymer (C) in the pressure-sensitive adhesive composition is preferably 70 to 99% by mass, more preferably 75 to 98% by mass, with respect to the total amount (100% by mass) of the pressure-sensitive adhesive composition. More preferably, it is 80 to 96% by mass or more.

The value of β calculated from the following formula (2) serves as an index representing the number of energy ray polymerizable groups of the acrylic copolymer (C1). In the acrylic copolymer (C1), the value of β calculated from the following formula (2) is preferably 0.5-30, more preferably 1.0-20, still more preferably 1.2-15, More preferably, it is 2-12.
By including the acrylic copolymer (C1) having such a value of β, the pressure-sensitive adhesive layer can easily adjust the elastic modulus of the pressure-sensitive adhesive layer to a desired range.
Formula (2): β = [P _c ] × [Q _c ] × [R _c ] / 100
(In Formula (2), [ _Pc ] shows content of the structural unit derived from a functional group containing monomer (c2) with respect to 100 mass parts of all the structural units of an acryl-type copolymer (C0). [ _Qc ]. Represents the equivalent of the polymerizable compound (Xc) to 100 equivalents of the functional group derived from the functional group-containing monomer (c2) of the acrylic copolymer (C0), where [R _c ] is the polymerizable compound (Xc). Indicates the number of energy ray polymerizable groups possessed by.

[Crosslinking agent]
The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. The pressure-sensitive adhesive composition is crosslinked by a crosslinking agent, for example, by being heated after application. As for the pressure-sensitive adhesive layer, the acrylic polymer (C) is cross-linked by the cross-linking agent, so that a coating film is appropriately formed, and the function as the pressure-sensitive adhesive layer is easily exhibited.
Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a chelating crosslinking agent, and among these, an isocyanate crosslinking agent is preferable. You may use a crosslinking agent individually or in combination of 2 or more types. Specific examples of the isocyanate-based crosslinking agent include those exemplified as the crosslinking agent that can be used in the intermediate layer forming composition, and preferred compounds thereof are also the same.
The content of the crosslinking agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, and further preferably 0.3 to 4 parts by mass with respect to 100 parts by mass of the acrylic polymer (C). Part by mass.

[Photopolymerization initiator]
The pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator. As a photoinitiator, what was illustrated as a photoinitiator used for the above-mentioned composition for intermediate | middle layer formation is mentioned. In addition, you may use a photoinitiator individually or in combination of 2 or more types. Of the above, 2,2-dimethoxy-1,2-diphenylethane-1-one and 1-hydroxycyclohexyl phenyl ketone are preferred.
The content of the photopolymerization initiator is usually 0.5 to 15 parts by mass with respect to 100 parts by mass of the acrylic polymer (C), more preferably 1 to 12 parts by mass, and still more preferably 4. 5 to 10 parts by mass. Thus, when content of a photoinitiator is comparatively high, it will become easy to make the elasticity modulus of the adhesive layer after hardening high.

The pressure-sensitive adhesive composition may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and the like. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.01 to 2 parts per 100 parts by mass of the acrylic polymer (C). Part by mass.
The thickness of the pressure-sensitive adhesive layer is preferably 1 to 100 μm, more preferably 1 to 75 μm, and still more preferably 3 to 50 μm.

In addition, the said elastic modulus of an adhesive layer is, when using an acrylic polymer (C), for example, the kind and quantity of the monomer which comprise an acrylic polymer (C), an acrylic polymer (C) It can be adjusted by the amount (β value) of the energy beam polymerizable group introduced into. For example, when the amount of energy ray polymerizable group (value of β) is increased, the elastic modulus tends to increase. Furthermore, it can be appropriately adjusted by the amount of the crosslinking agent blended in the pressure-sensitive adhesive layer, the amount of the photopolymerization initiator, and the like.

The intermediate layer-forming composition and the pressure-sensitive adhesive composition are each diluted with an organic solvent from the viewpoint of improving coatability when forming the intermediate layer and the pressure-sensitive adhesive layer on the surface of the substrate, release material, etc. The intermediate layer forming composition or the pressure-sensitive adhesive composition may be in the form of a solution.
Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol and the like. As the organic solvent to be used, the organic solvent used in the synthesis of the components (A) to (C) may be used as it is, or one or more organic solvents other than the organic solvent used in the synthesis may be added. Good.
In the case of the above-described solution form, the solid content concentration of the solution is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and further preferably 15 to 50% by mass.

<Base material>
The base material used for the pressure-sensitive adhesive sheet is preferably a resin film from the viewpoint that the holding performance with respect to the workpiece can be improved. Examples of the resin film include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, ethylene-vinyl acetate copolymer (EVA) film, polyethylene terephthalate. Film, polyethylene naphthalate film, polybutylene terephthalate film, ethylene- (meth) acrylic acid copolymer film, ethylene- (meth) acrylic acid ester copolymer film, polycarbonate film, polystyrene film, polyphenylene sulfide film, Cycloolefin polymer film, polyurethane film, ionomer resin film, polyimide film, fluororesin film Beam, and the like.

The substrate may be a resin film having only one kind of the above-described resin, or may be two or more kinds. For example, a single layer film made of one resin film or a multilayer film in which a plurality of resin films are laminated may be used. Moreover, these crosslinked films may be sufficient as a resin film.
Among the resin films, a polyethylene film, a polypropylene film, an ethylene-vinyl acetate copolymer (EVA) film, and a polyethylene terephthalate film are preferable in order to further increase the work holding performance.
The resin film may contain a known filler, colorant, antistatic agent, antioxidant, organic lubricant, catalyst, and the like. The resin film may be transparent or may be colored as desired.
The thickness of the substrate is preferably 10 to 500 μm, more preferably 15 to 300 μm, and still more preferably 20 to 200 μm.

<Release material>
The pressure-sensitive adhesive sheet for wafer protection of the present invention may further have a release material on the pressure-sensitive adhesive layer.
Examples of the release material include a release sheet subjected to double-sided release treatment, a release sheet subjected to single-sided release treatment, and the like. These release sheets include those obtained by applying a release agent on a release material substrate.
Examples of the substrate for the release material include the resin film used as the above-mentioned substrate, and polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene are preferable. .
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long chain alkyl resins, alkyd resins, and fluorine resins.
The thickness of the release material is not particularly limited, but is preferably 10 to 200 μm, more preferably 20 to 150 μm.

[Method for producing adhesive sheet]
There is no restriction | limiting in particular as a manufacturing method of the adhesive sheet for wafer protection of this invention, It can manufacture by a well-known method.
For example, it can be manufactured by preparing a base material with an intermediate layer provided with an intermediate layer on one surface of the base material, and further laminating an adhesive layer on the intermediate layer of the base material with the intermediate layer. .
The base material with an intermediate layer can be produced, for example, by applying the intermediate layer forming composition or a solution thereof to one surface of the base material, and then heating and drying to form the intermediate layer. Alternatively, an intermediate layer forming composition or a solution thereof is applied to the release treatment surface of the release material, then heated and dried to form an intermediate layer on the release material, and this intermediate layer is bonded to the substrate. A substrate with an intermediate layer may be obtained. In addition, what is necessary is just to peel a peeling material before laminating | stacking an adhesive layer on an intermediate | middle layer.

The pressure-sensitive adhesive layer forms a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition or a solution thereof on a release treatment surface of a release material different from the release material used when preparing the intermediate layer, and drying by heating. The pressure-sensitive adhesive layer with the release material may be bonded onto the intermediate layer. The release material may be peeled off from the pressure-sensitive adhesive layer, or may be used as a release material provided on the pressure-sensitive adhesive layer as it is.
Moreover, you may form an adhesive layer by apply | coating an adhesive composition directly on the intermediate | middle layer of a base material with an intermediate | middle layer, and heating and drying after that. In this case, a release material may be further bonded onto the pressure-sensitive adhesive layer.

Examples of the method for applying the intermediate layer forming composition, the adhesive composition, or a solution thereof onto the substrate or the release material include spin coating, spray coating, bar coating, knife coating, and roll. Examples thereof include a coating method, a blade coating method, a die coating method, and a gravure coating method.
Further, when forming a relatively thick intermediate layer, two or more intermediate layers are formed by applying and drying a solution of the intermediate layer forming composition on the release treatment surface of the release material. The intermediate layers may be formed by laminating each other or sequentially laminating a plurality of intermediate layers on the substrate. The same applies to the pressure-sensitive adhesive layer.

[Usage of adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is used when affixing to various workpieces such as a semiconductor wafer and processing the workpiece, and is preferably used by being affixed to a workpiece surface having irregularities and protrusions.
Moreover, it is more preferable to affix on the semiconductor wafer surface, especially the wafer surface in which the bump was formed, and to use as a semiconductor wafer surface protection adhesive sheet. The adhesive sheet is more preferably used as a bag grind tape that is attached to the surface of a semiconductor wafer and protects a circuit formed on the wafer surface during subsequent grinding of the wafer back surface. In the case where the pressure-sensitive adhesive sheet of the present invention has an intermediate layer, the embedding property is good even if there is a height difference due to bumps or the like on the wafer surface, so that the protection performance of the wafer surface is good.

In the present invention, the pressure-sensitive adhesive layer and the intermediate layer are energy ray curable. Therefore, the pressure-sensitive adhesive sheet attached to the work surface such as a semiconductor wafer is peeled from the work surface after being irradiated with energy rays and cured with energy rays. Thereby, since an adhesive sheet peels after adhesive force declines, peelability becomes favorable. In addition, when the cured pressure-sensitive adhesive sheet is peeled off, delamination that occurs between the pressure-sensitive adhesive layer and the intermediate layer is prevented as described above, and adhesive residue hardly occurs on the wafer surface.
In addition, the use of an adhesive sheet is not limited to a back grind sheet, It can also be used for other uses. For example, the pressure-sensitive adhesive sheet may be used as a dicing sheet that holds the wafer when the wafer is diced on the back side of the wafer. In this case, the wafer may be a wafer in which protrusions such as bumps or irregularities are formed on the back surface of the wafer, such as a wafer in which through electrodes are formed.

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

The measurement method and evaluation method in the present invention are as follows.
[Weight average molecular weight (Mw)]
Using a gel permeation chromatograph (product name “HLC-8220”, manufactured by Tosoh Corporation), measurement was performed under the following conditions, and values measured in terms of standard polystyrene were used.
(Measurement condition)
Column: “TSK guard column HXL-H” “TSK gel GMHXL (× 2)” “TSK gel G2000HXL” (both manufactured by Tosoh Corporation)
Column temperature: 40 ° C. Developing solvent: Tetrahydrofuran Flow rate: 1.0 mL / min

[Elastic modulus measurement]
Polyethylene terephthalate (PET) -based release film (product name “SP-PET381031” manufactured by Lintec Corporation, thickness) on both sides using the intermediate layer forming composition and the adhesive composition used in each Example and Comparative Example : An intermediate layer having a thickness of 200 μm and a pressure-sensitive adhesive layer were prepared. The intermediate layer having a thickness of 200 μm was obtained by preparing a plurality of intermediate layers having a thickness of 50 μm formed on the release film and sequentially laminating them by the same method as in Examples and Comparative Examples. The same applies to the pressure-sensitive adhesive layer.
Thereafter, the intermediate layer and the pressure-sensitive adhesive layer were irradiated with ultraviolet rays at an illuminance of 230 mW / cm ² and an integrated light amount of 500 mJ / cm ² using an ultraviolet irradiation device (product name “RAD-2000m / 12” manufactured by Lintec Corporation). Next, the intermediate | middle layer and adhesive layer hardened | cured with the ultraviolet-ray were cut into the magnitude | size of 4 mm x 50 mm, and it was set as the sample for measuring viscoelasticity. Using the sample, the storage elastic modulus (frequency: 1 Hz) was measured at −30 to 200 ° C. at a temperature increase rate of 3 ° C./min with a viscoelasticity measuring device (product name “Leo Vibron” manufactured by Orientec Co., Ltd.). The value of the storage elastic modulus at 23 ° C. was defined as the elastic modulus of each layer after curing with energy rays.

[Interlayer strength measurement]
A double-sided tape (Lintech Co., Ltd., trade name “Tack Liner”) is affixed to the SUS plate, and a substrate surface of a dicing tape (Lintech Co., Ltd., product name “ADWILL D-510T”) is affixed to it and dicing The pressure-sensitive adhesive sheet (length: 200 mm, width: 25 mm) prepared in Examples and Comparative Examples and peeled off from the pressure-sensitive adhesive surface of the tape is the pressure-sensitive adhesive surface of the dicing tape. It was affixed so that it might adhere to. Thereafter, the prepared sample was subjected to UV irradiation (illuminance: 230 mW / cm ² , light amount: 500 mJ / cm ² ) using RAD-2000m / 12 manufactured by Lintec Corporation, and “Autograph AG-IS 1kN manufactured by Shimadzu Corporation”. The film was peeled at a peeling speed of 600 mm / min and a peeling angle of 180 ° in an environment of 23 ° C. and 50% RH, and the interlayer strength between the intermediate layer and the adhesive layer was measured.

[Example 1]
(Preparation of substrate A with intermediate layer)
An acrylic copolymer (weight average molecular weight: 600,000) obtained by copolymerizing 91 parts by mass of n-butyl acrylate (BA) and 9 parts by mass of acrylic acid (AA) is used as the acrylic polymer (A). Prepared. Further, methacryloyloxyethyl isocyanate is obtained by copolymerizing an acrylic copolymer obtained by copolymerizing 62 parts by mass of n-butyl acrylate (BA), 10 parts by mass of methyl methacrylate (MMA) and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA). (A product name “Karenz MOI” manufactured by Showa Denko KK) was added to an acrylic copolymer (weight average molecular weight: 80 equivalents with respect to a hydroxyl group (100 equivalents) of 2HEA. 100,000) was prepared as an acrylic polymer (B).
1. 100 parts by mass of the acrylic polymer (A), 13 parts by mass of the acrylic polymer (B), and trimethylolpropane adduct tolylene diisocyanate (product name “Coronate L”, manufactured by Tosoh Corporation) as a crosslinking agent 2 parts by mass and 3.71 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF, product name “Irgacure 184”) as a photopolymerization initiator were added, and the solid content concentration was adjusted to 37% by mass using toluene. Then, stirring was performed for 30 minutes to obtain a solution of the intermediate layer forming composition.

Next, the intermediate layer forming composition solution was applied to a PET-based release film (product name “SP-PET 381031”, thickness 38 μm, manufactured by Lintec Corporation), dried by heating at 100 ° C. for 2 minutes, and then released. An intermediate layer with a film was formed. The thickness of the intermediate layer was 50 μm. Two intermediate layers with a release film were prepared. Next, the intermediate layer side of one intermediate layer with a release film is bonded to an ethylene-vinyl acetate film (Gunze Co., Ltd., product name “Fanclair LEB”, thickness 120 μm) as a base material, The release film was peeled off. Thereafter, the other intermediate layer with a release film is further bonded onto the intermediate layer laminated on the base material, and the intermediate layer has a thickness of 100 μm and is provided with an intermediate layer composed of a release material / intermediate layer / base material. A substrate A was obtained.

(Preparation of adhesive sheet)
An acrylic system obtained by copolymerizing 70 parts by mass of n-butyl acrylate (BA), 15 parts by mass of ethyl acrylate (EA), 5 parts by mass of methyl methacrylate (MMA), and 10 parts by mass of 4-hydroxybutyl acrylate (4HBA). Acrylic obtained by adding methacryloyloxyethyl isocyanate (product name “Karenz MOI”, manufactured by Showa Denko KK) to the copolymer so that the addition rate is 90 equivalents with respect to the hydroxyl group (100 equivalents) of 4HBA. A copolymer (weight average molecular weight: 600,000) was prepared as an acrylic polymer (C).
To 100 parts by mass of the acrylic polymer (C), 1.5 parts by mass of trimethylolpropane adduct tolylene diisocyanate (manufactured by Tosoh Corporation, product name “Coronate L”) as a crosslinking agent, 2 as a photopolymerization initiator , 2-Dimethoxy-1,2-diphenylethane-1-one (Irgacure 651, manufactured by BASF) was added in an amount of 7.3 parts by mass, the solid content was adjusted to 20% by mass using toluene, and the mixture was stirred for 30 minutes. And a solution of the pressure-sensitive adhesive composition was obtained.
Next, the adhesive composition solution was applied to a PET-based release film (product name “SP-PET 381031” thickness: 38 μm, manufactured by Lintec Corporation), dried by heating at 90 ° C. for 1 minute, and having a thickness of 10 μm. A preparation layer was prepared. The release film on the substrate A with the intermediate layer prepared above is removed, and the exposed intermediate layer is bonded onto the adhesive layer, and the adhesive sheet is made of a release material / adhesive layer / intermediate layer / substrate. Was made.

[Example 2]
(Preparation of base material B with intermediate layer)
Except changing the addition amount of an acrylic polymer (B) to 23 mass parts, it implemented similarly to Example 1 and produced the base material B with the intermediate | middle layer.
(Preparation of adhesive sheet)
An acrylic copolymer obtained by copolymerizing 74 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 6 parts by mass of 2-hydroxyethyl acrylate (2HEA) was added to methacryloyloxyethyl isocyanate (Showa). Acrylic copolymer (weight average molecular weight: 600, manufactured by Denko Co., Ltd., product name “Karenz MOI”) added to a hydroxyl group of 2HEA (100 equivalents) so that the addition rate is 50 equivalents. 000) was prepared as an acrylic polymer (C).
To 100 parts by mass of the acrylic polymer (C), 0.5 parts by mass of trimethylolpropane adduct tolylene diisocyanate (product name “Coronate L”, manufactured by Tosoh Corporation) as a crosslinking agent, and 1- 6.0 parts by mass of hydroxycyclohexyl phenyl ketone (Irgacure 184, manufactured by BASF) was added, the solid content concentration was adjusted to 20% by mass using toluene, and the mixture was stirred for 30 minutes to obtain a solution of the pressure-sensitive adhesive composition. .
Next, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the solution of the pressure-sensitive adhesive composition was used and the base material B with an intermediate layer was used instead of the base material A with an intermediate layer.

[Comparative Example 1]
(Preparation of adhesive sheet)
An acrylic copolymer obtained by copolymerizing 52 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA) was added to methacryloyloxyethyl isocyanate (Showa Acrylic copolymer (weight average molecular weight: 600, manufactured by Denko Co., Ltd., product name “Karenz MOI”) was added so that the addition rate was 90 equivalents with respect to 2HEA hydroxyl group (100 equivalents). 000) was prepared as an acrylic polymer (C).
100 parts by mass of the acrylic polymer (C), 0.5 parts by mass of trimethylolpropane adduct tolylene diisocyanate (product name “Coronate L”, manufactured by Tosoh Corporation) as a crosslinking agent, 1 as a photopolymerization initiator -Hydroxycyclohexyl phenyl ketone ("Irgacure 184" manufactured by BASF) was added in an amount of 1.4 parts by mass, the solid content was adjusted to 20% by mass using toluene, and the mixture was stirred for 30 minutes to obtain an adhesive composition. A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the obtained pressure-sensitive adhesive composition.

[Comparative Example 2]
A substrate C with an intermediate layer was obtained in the same manner as the substrate A with an intermediate layer (Example) except that the amount of the acrylic polymer (B) added was changed to 67 parts by mass. A surface protective sheet was produced in the same manner as in Example 2 except that the substrate C with an intermediate layer was used.

[Comparative Example 3]
Except changing the addition amount of an acrylic polymer (B) to 107 mass parts, the base material D with the intermediate | middle layer was obtained by the method similar to the base material A with an intermediate | middle layer (Example 1). A surface protective sheet was produced in the same manner as in Example 2 except that the base material D with the intermediate layer was used.

　

　

As is clear from Examples 1 and 2 above, since the interlayer strength is increased by reducing the difference in elastic modulus to 20 MPa or less, when the adhesive sheet for semiconductor processing is cured and peeled from the workpiece, the intermediate layer It is possible to prevent delamination that occurs between the adhesive layer and the pressure-sensitive adhesive layer.
On the other hand, in Comparative Examples 1 to 3, since the difference in elastic modulus increased and the interlayer strength decreased, when the adhesive sheet for semiconductor processing was cured and peeled from the workpiece, the intermediate layer and the adhesive layer Delamination that occurs between them cannot be sufficiently prevented.

Claims (8)

A semiconductor processing pressure-sensitive adhesive sheet comprising a base material, an intermediate layer, and a pressure-sensitive adhesive layer in this order,
The intermediate layer contains a non-energy ray curable acrylic polymer (A) and an energy ray curable acrylic polymer (B) having a weight average molecular weight of 50,000 to 250,000. A layer formed from the composition, and the pressure-sensitive adhesive layer is energy ray curable,
A pressure-sensitive adhesive sheet for semiconductor processing, wherein the difference in elastic modulus at 23 ° C. between the intermediate layer and the pressure-sensitive adhesive layer after energy ray curing is 20 MPa or less. The pressure-sensitive adhesive sheet for semiconductor processing according to claim 1, wherein in the intermediate layer forming composition, the acrylic polymer (B) is less than 25 parts by mass with respect to 100 parts by mass of the acrylic polymer (A). The pressure-sensitive adhesive sheet for semiconductor processing according to claim 1 or 2, wherein the acrylic polymer (A) has a weight average molecular weight of 300,000 to 1,500,000. The pressure-sensitive adhesive sheet for semiconductor processing according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing an energy ray-curable acrylic polymer (C). The acrylic polymer (C) is an acrylic polymer having a structural unit derived from an alkyl (meth) acrylate (c1) having an alkyl group having 1 to 18 carbon atoms and a structural unit derived from a functional group-containing monomer (c2) The pressure-sensitive adhesive sheet for semiconductor processing according to claim 4, which is an acrylic copolymer (C1), which is a reaction product obtained by reacting the copolymer (C0) with a polymerizable compound (Xc) having an energy beam polymerizable group. . The pressure-sensitive adhesive sheet for semiconductor processing according to claim 4 or 5, wherein the acrylic polymer (C) has a weight average molecular weight of 100,000 to 1,500,000. The intermediate layer forming composition contains 0.3 to 15 parts by mass of a photopolymerization initiator with respect to 100 parts by mass of the acrylic polymer (A).
The semiconductor according to any one of claims 4 to 6, wherein the pressure-sensitive adhesive composition contains 0.5 to 15 parts by mass of a photopolymerization initiator with respect to 100 parts by mass of the acrylic polymer (C). Processing adhesive sheet. The acrylic polymer (B) is an acrylic polymer having a structural unit derived from an alkyl (meth) acrylate (b1) having an alkyl group having 1 to 18 carbon atoms and a structural unit derived from a functional group-containing monomer (b2). The acrylic copolymer (B1), which is a reaction product obtained by reacting the copolymer (B0) with a polymerizable compound (Xb) having an energy ray polymerizable group, according to any one of claims 1 to 7. The adhesive sheet for semiconductor processing as described.