WO2017159343A1

WO2017159343A1 - Adhesive tape for semiconductor wafer processing and method for processing semiconductor wafer

Info

Publication number: WO2017159343A1
Application number: PCT/JP2017/007709
Authority: WO
Inventors: 雅人大倉
Original assignee: 古河電気工業株式会社
Priority date: 2016-03-17
Filing date: 2017-02-28
Publication date: 2017-09-21
Also published as: TW201802207A; KR102089928B1; JP2017168739A; JP6034522B1; CN107960131B; TWI744290B; CN107960131A; KR20180020956A

Abstract

An adhesive tape for semiconductor wafer processing, which comprises an adhesive layer on at least one surface of a base film, and which is characterized in that the adhesive in the adhesive layer is a radiation curable adhesive and comprises at least a resin or oligomer selected from among a base resin having an ethylenically unsaturated group (that is a radiation polymerizable carbon-carbon double bond and an ethylenic double bond) in a side chain, an acrylic pressure sensitive base resin containing no monomer unit derived from an alicyclic (meth)acrylate, and a urethane acrylate oligomer having at least two ethylenically unsaturated groups (that are radiation polymerizable carbon-carbon double bonds and ethylenic double bonds) in each molecule, and that the adhesive contains 0.2-2.0 mmol/g of an ethylenically unsaturated group; a method for producing an adhesive tape for semiconductor wafer processing; and a method for processing a semiconductor wafer.

Description

Adhesive tape for semiconductor wafer processing and method for processing semiconductor wafer

The present invention relates to an adhesive tape for processing a semiconductor wafer and a method for processing a semiconductor wafer.

A semiconductor package is manufactured by slicing a high-purity silicon single crystal or the like into a semiconductor wafer, and then forming an integrated circuit on the surface of the semiconductor wafer by ion implantation, etching, or the like. The semiconductor wafer is processed to a desired thickness by grinding or polishing the back surface of the semiconductor wafer on which the integrated circuit is formed. At this time, in order to protect the integrated circuit formed on the surface of the semiconductor wafer, an adhesive tape for protecting the surface of the semiconductor wafer (hereinafter also simply referred to as “surface protective tape”) is used.
The back-ground semiconductor wafer is stored in a semiconductor wafer cassette after the back-side grinding is completed, transported to a dicing process, and processed into semiconductor chips.

Conventionally, it has been required that the thickness of a semiconductor wafer be about 200 to 400 μm by back grinding or the like. However, with the recent progress of high-density mounting technology, it is necessary to reduce the size of the semiconductor chip, and accordingly, the semiconductor wafer is becoming thinner. Depending on the type of semiconductor chip, it is necessary to make the semiconductor wafer as thin as about 100 μm. On the other hand, in order to increase the number of semiconductor chips that can be manufactured by a single process, the diameter of the original semiconductor wafer tends to be increased. In the past, semiconductor wafers having a diameter of 5 inches or 6 inches have been the mainstream, but in recent years, processing of semiconductor wafers having a diameter of 8 to 12 inches has become the mainstream.
The trend of increasing the diameter of a semiconductor wafer at the same time as making it thinner is particularly remarkable in the field of flash memory where NAND type and NOR type exist, and in the field of DRAM, which is a volatile memory. For example, it is not uncommon to grind a semiconductor wafer having a diameter of 12 inches to a thickness of 150 μm or less.

In addition to this, wafers used for flip-chip mounting using electrode-equipped semiconductor wafers that take impact resistance into account with the recent spread of smartphones, mobile phone performance improvements, music player miniaturization, and performance improvements, etc. There is also an increasing demand for thin films. In addition, with respect to the semiconductor wafer with bumps, it is necessary to perform thin film grinding of the semiconductor wafer portion to 100 μm or less. Bumps for flip chip connection have been densified in order to improve transfer speed, and bump height (projection height from the surface of the semiconductor wafer) has been reduced, and accordingly, the distance between bumps. Is getting shorter. In recent years, flip chip connection has also been implemented in DRAMs, so that the thinning of semiconductor wafers has been accelerated.

Flip chip mounting has been attracting attention as a method for mounting a semiconductor element in a minimum area in response to recent downsizing and higher density of electronic devices. Bumps are formed on the electrodes of the semiconductor element used for the flip chip mounting, and the bumps are electrically joined to the wiring on the circuit board. As the composition of these bumps, solder or gold is mainly used. The solder bump or gold bump is formed on an exposed aluminum terminal connected to the internal wiring of the chip by vapor deposition or plating.

However, bumped semiconductor wafers have large irregularities on the surface, making thin film processing difficult, and if the backside grinding is performed using ordinary adhesive tape, semiconductor wafer cracks may occur or the thickness of the semiconductor wafer It may cause deterioration of accuracy. For this reason, the bumped semiconductor wafer is ground using a specially designed surface protection tape (see, for example, Patent Document 1).

However, these surface protection tapes absorb the bumps sufficiently to ensure the grindability, so that it is very difficult to achieve both the releasability. The finished thickness of the chip that has been flip-chip mounted so far has a certain thickness of 200 μm or more, and has been able to be peeled off because of its rigidity. However, recently, the thickness of the finished semiconductor wafer has become even thinner and the bump density has increased, which has caused a problem that the surface protection tape cannot be easily peeled off. On the other hand, if the peelability is ensured, the adhesion becomes insufficient, causing intrusion of grinding water and residual glue during back grinding.

In addition to this, the bump height of the semiconductor wafer with bumps used in the wafer level package remains high, and bumps with a height of 250 μm or more are also mounted. Wafer level packages do not require chip stacking, so they are not ground as thin as 50 μm or less like memory semiconductor wafers, but they are very easy to break even with thick film grinding because they have high bumps and are 150 μm thick. The following grinding thickness easily causes the problem of semiconductor wafer cracking.

On the other hand, in recent years, various studies have been conducted using a radiation curable pressure-sensitive adhesive having an ethylenically unsaturated group in a polymer. For example, an acrylic copolymer having a functional group-containing monomer unit and a substitution that reacts with this functional group in order to peel it from the semiconductor wafer surface without destroying a fine pattern on the surface of the semiconductor wafer without leaving an adhesive. A radiation curable copolymer obtained by containing a compound containing an ethylenically unsaturated group having a group (see, for example, Patent Documents 1 and 2) is representative.
Further, a urethane acrylate oligomer in which a compound having an ethylenically unsaturated group to be reacted with an acrylic copolymer having a functional group-containing monomer unit is reacted with an aliphatic diisocyanate and an acrylate having one hydroxyl group (for example, Patent Document 3) See also).

JP 2001-203255 A JP-A-9-298173 JP 2008-021897 A

However, in the conventional surface protection tape as shown in Patent Documents 1 to 3, the height of the step and the protrusion becomes higher and the semiconductor wafer to be ground and the thickness of the semiconductor wafer after grinding become thinner and thinner. In the situation, not necessarily enough.

Therefore, the present invention is suitably used for a semiconductor wafer having a step or a protrusion, for securely holding a semiconductor wafer during processing of the semiconductor wafer, and capable of peeling without peeling or leaving a residue of the semiconductor wafer during peeling. It is an object to provide a method for processing an adhesive tape and a semiconductor wafer.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the molar amount per unit g of the ethylenically unsaturated group of the radiation curable pressure-sensitive adhesive is important.
That is, it has been conventionally desired that the radiation curable pressure-sensitive adhesive is sufficiently crosslinked so as to reduce the apparent adhesive force (adhesive force to a smooth adherend). However, as a result of detailed observation, when the surface unevenness is large, such as a semiconductor wafer with bumps, curing shrinkage occurs by crosslinking, and adhesive residue bites into the semiconductor wafer with bumps. It was found that an increase in peeling force occurred. The present invention has been completed based on such findings.

That is, the said subject of this invention was achieved by the following means.
<1> A semiconductor wafer processing pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on at least one surface of a base film, wherein the pressure-sensitive adhesive layer is a radiation-curable pressure-sensitive adhesive and has at least ethylene in the side chain. Base resin having a polymerizable unsaturated group (radiation polymerizable carbon-carbon double bond and ethylenic double bond), an acrylic pressure-sensitive base resin containing no monomer unit derived from alicyclic (meth) acrylate, and A resin or oligomer selected from urethane acrylate oligomers having at least two ethylenically unsaturated groups (radiation polymerizable carbon-carbon double bonds and ethylenic double bonds) in the molecule, and the pressure-sensitive adhesive comprises A pressure-sensitive adhesive tape for processing a semiconductor wafer, having an ethylenically unsaturated group of 0.2 to 2.0 mmol / g.
<2> An acrylic pressure-sensitive base resin that does not contain a monomer unit derived from the alicyclic (meth) acrylate is an alkyl ester that may have a functional group of (meth) acrylic acid, acrylic acid, and <1> The adhesive tape for processing a semiconductor wafer according to <1>, comprising only a monomer unit derived from methacrylic acid.
<3> The functional group of the alkyl ester which may have a functional group of (meth) acrylic acid is a carboxy group, a hydroxyl group, an amino group, a mercapto group, a cyclic acid anhydride group, an epoxy group, an isocyanate group ( The adhesive tape for processing semiconductor wafers according to <2>, wherein -N = C = O).
<4> The pressure-sensitive adhesive tape for processing a semiconductor wafer according to any one of <1> to <3>, wherein the mass average molecular weight of at least one kind of the oligomer is 1,100 to 20,000.
<5> The adhesive tape for processing a semiconductor wafer according to any one of <1> to <3>, wherein the mass average molecular weight of at least one of the oligomers is 1,400 to 20,000.
<6> The oligomer is a mixture of at least an oligomer having two ethylenically unsaturated groups in the molecule and an oligomer having three or more ethylenically unsaturated groups in the molecule <1> to The pressure-sensitive adhesive tape for processing a semiconductor wafer according to any one of <5>.
<7> The adhesive for semiconductor wafer processing according to any one of <1> to <6>, wherein the adhesive has the ethylenically unsaturated group of 0.72 to 2.0 mmol / g. tape.
<8> The adhesive tape for processing a semiconductor wafer according to any one of <1> to <7>, wherein the adhesive contains a polyvalent isocyanate compound.
<9> Any of <1> to <8>, wherein the adhesive strength after UV curing to the SUS plate is 0.3 to 3.0 N / 25 mm, and the curing shrinkage stress is 300 gf or less The adhesive tape for semiconductor wafer processing of Claim 1.
<10> The semiconductor wafer processing pressure-sensitive adhesive tape according to any one of <1> to <9> is bonded to a semiconductor wafer surface having a surface irregularity of 10 μm or more, and then irradiated with ultraviolet rays, to thereby form the semiconductor wafer A method for processing a semiconductor wafer, comprising a step of peeling the processing adhesive tape.
Here, in <1>, “at least derived from a base resin having an ethylenically unsaturated group (radiation polymerizable carbon-carbon double bond and ethylenic double bond) in the side chain, and an alicyclic (meth) acrylate. Selected from acrylic pressure-sensitive base resins that do not contain monomer units and urethane acrylate oligomers that have at least two ethylenically unsaturated groups (radiation polymerizable carbon-carbon double bonds and ethylenic double bonds) in the molecule The phrase “having a resin or oligomer” means having at least one selected from the group of the above-mentioned resin and the above-mentioned oligomer. Therefore, these resins or oligomers may be used alone or in combination, and may be further combined with other resins or other oligomers.

According to the present invention, it is possible to provide a semiconductor wafer processing pressure-sensitive adhesive tape and a semiconductor wafer processing method that can securely hold a semiconductor wafer during semiconductor wafer processing and can be peeled off without being damaged or left behind when the semiconductor wafer is peeled off. became.
In particular, in the present invention, when the semiconductor wafer having steps and protrusions, or the semiconductor wafer to be ground and the thickness of the semiconductor wafer after grinding are thin, the above-described effects of the present invention are effectively exhibited.

<< Semiconductor wafer processing adhesive tape >>
The pressure-sensitive adhesive tape for processing a semiconductor wafer according to the present invention has a radiation having an ethylenically unsaturated group (radiation polymerizable carbon-carbon double bond) of 0.2 to 2.0 mmol / g on at least one surface of a base film. It has an adhesive layer composed of a curable adhesive.
Hereinafter, it demonstrates in detail from a base film in order.

<Base film>
The base film is preferably made of a resin film, and known plastics, rubbers and the like can be used. For example, polyolefin resin (polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid Homopolymers or copolymers of α-olefins such as methyl copolymers, ethylene-acrylic acid copolymers, ionomers, or mixtures thereof), polyester resins (polyethylene terephthalate, polyethylene naphthalate), polycarbonate resins, polyurethane resins Engineering plastics (polymethyl methacrylate, etc.), synthetic rubbers (styrene-ethylene-butene or pentene copolymers), thermoplastic elastomers (polyamide-polyol copolymers, etc.), and mixtures thereof Thing, and the like. Moreover, you may use what made these two or more layers.
In the present invention, the base film is preferably a polyolefin resin, and more preferably an ethylene-vinyl acetate copolymer film.

The thickness of the base film is 50 to 300 μm if the base material has flexibility such as polyethylene, and has rigidity such as polyester, from the viewpoints of high elongation characteristics, peelability of the surface protection tape, and cutability in the bonding machine. In the case of a substrate, 10 to 100 μm is appropriate.
In the present invention, 50 to 300 μm is preferable.

<Adhesive layer (adhesive)>
In the present invention, the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer is a radiation curable pressure-sensitive adhesive.
Radiation curable pressure-sensitive adhesives only need to have the property of being cured by radiation to form a three-dimensional network, and can be broadly divided into 1) ethylenically unsaturated groups (radiation polymerizable carbon-carbon double bonds in ethylenic groups) At least two in the molecule relative to the pressure-sensitive adhesive comprising a base resin (polymer) having a double bond) and 2) a normal rubber-based or (meth) acrylic pressure-sensitive base resin (polymer) Are classified into pressure-sensitive adhesives containing a low molecular weight compound having an ethylenically unsaturated group (hereinafter referred to as radiation-polymerizable low molecular weight compound) and a photopolymerization initiator.
In the present invention, the above 2) is preferable.

1) Adhesive comprising a base resin having an ethylenically unsaturated group in the side chain The adhesive having an ethylenically unsaturated group in the side chain is preferably a (meth) acrylic adhesive, and the base resin is a (meth) acrylic Those containing a polymer or (meth) acrylic polymer as a main component are particularly preferred.
Here, a (meth) acrylic polymer as a main component means that the (meth) acrylic polymer component is at least 50% by mass or more, preferably 80% by mass or more (100% by mass or less).

The (meth) acrylic polymer has an ethylenically unsaturated group in at least a side chain, so that it can be cured by irradiation, and may further have a functional group such as an epoxy group or a carboxy group.

The (meth) acrylic polymer having an ethylenically unsaturated group in the side chain may be produced in any manner. For example, a (meth) acrylic polymer having a functional group (α) in the side chain and , A (meth) acryloyl group, an ethylenically unsaturated group such as a (meth) acryloyloxy group, and a function capable of reacting with the side chain functional group (α) of the (meth) acrylic polymer What was obtained by making it react with the compound which has group ((beta)) is preferable.
The group having an ethylenically unsaturated group may be any group as long as it has a non-aromatic ethylenic double bond, but a (meth) acryloyl group, a (meth) acryloyloxy group, a (meth) acryloyl group. An amino group, an allyl group, a 1-propenyl group, and a vinyl group (including styrene or substituted styrene) are preferable, and a (meth) acryloyl group and a (meth) acryloyloxy group are more preferable.
Examples of the functional groups (α) and (β) include a carboxy group, a hydroxyl group, an amino group, a mercapto group, a cyclic acid anhydride group, an epoxy group, and an isocyanate group (—N═C═O).
The cyclic acid anhydride group is a group having a cyclic acid anhydride structure.

Here, when one functional group of the functional group (α) and the functional group (β) is a carboxy group, a hydroxyl group, an amino group, a mercapto group, or a cyclic acid anhydride group, the other functional group Includes an epoxy group and an isocyanate group. When one functional group is a cyclic acid anhydride group, the other functional group includes a carboxy group, a hydroxyl group, an amino group, and a mercapto group. In addition, when one functional group is an epoxy group, the other functional group may be an epoxy group.

As the functional group (α), a carboxy group and a hydroxyl group are preferable, and a hydroxyl group is particularly preferable.
The (meth) acrylic polymer having a functional group (α) in the side chain is a (meth) acrylic monomer having a functional group (α), preferably a (meth) acrylic ester [(particularly, a functional group in the alcohol part). It can be obtained by using (having (α)) as a monomer component.
The (meth) acrylic polymer having a functional group (α) in the side chain is preferably a copolymer, and this copolymerization component is a (meth) acrylic acid alkyl ester, in particular, a functional group ( α) and (meth) acrylic acid alkyl esters in which the group having an ethylenically unsaturated group is not substituted are preferred.

Examples of (meth) acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2 -Ethylhexyl acrylate, dodecyl acrylate, decyl acrylate hexyl acrylate, and the corresponding methacrylates.
The (meth) acrylic acid ester may be one type or two or more types, but it is preferable to use one having an alcohol part having 5 or less carbon atoms and one having 6 to 12 carbon atoms.

In addition, since a glass transition point (Tg) becomes so low that a monomer with large carbon number of an alcohol part is used, the thing of a desired glass transition point can be obtained. In addition to the glass transition point, it is also preferable to blend a low molecular compound having a carbon-carbon double bond such as vinyl acetate, styrene or acrylonitrile for the purpose of improving compatibility and various performances. The content of is preferably in the range of 5% by mass or less.

Examples of (meth) acrylic monomers having a functional group (α) include acrylic acid, methacrylic acid, cinnamic acid, itaconic acid, fumaric acid, phthalic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylates, glycol Monoacrylates, glycol monomethacrylates, N-methylolacrylamide, N-methylolmethacrylamide, allyl alcohol, N-alkylaminoethyl acrylates, N-alkylaminoethyl methacrylates, acrylamides, methacrylamides, maleic anhydride, Some of the isocyanate groups of itaconic anhydride, fumaric anhydride, phthalic anhydride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, polyisocyanate compounds Such as those urethanization with monomers like having Bokishi groups and ethylenically unsaturated groups.

Among these, acrylic acid, methacrylic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylates, glycidyl acrylate, and glycidyl methacrylate are preferable. Acrylic acid, methacrylic acid, 2-hydroxyalkyl acrylates, 2-hydroxyalkyl methacrylate Are more preferable, and 2-hydroxyalkyl acrylates and 2-hydroxyalkyl methacrylates are more preferable.

The functional group (β) in the compound having an ethylenically unsaturated group and a functional group (β) is preferably an isocyanate group. For example, (meth) acrylic acid ester having an isocyanate (—N═C═O) group in the alcohol part can be mentioned, and in particular, (meth) acrylic acid alkyl ester substituted with an isocyanate (—N═C═O) group. Is preferred. Examples of such a monomer include 2-isocyanatoethyl methacrylate and 2-isocyanatoethyl acrylate.
Moreover, the compound illustrated with the (meth) acrylic-type monomer which has a functional group ((alpha)) as a preferable compound in case a functional group ((beta)) is other than an isocyanate group is mentioned.

In addition to the (meth) acrylic polymer having a functional group (α) in the side chain, the compound having an ethylenically unsaturated group and the functional group (β) is preferably a functional group (α) in the side chain of the polymer, preferably By reacting with a hydroxyl group, a polymerizable group can be incorporated into the copolymer, and the adhesive strength after irradiation can be reduced.

In the synthesis of the (meth) acrylic copolymer, as the organic solvent when the reaction is carried out by solution polymerization, ketone, ester, alcohol, and aromatic solvents can be used, among which toluene, Generally, it is a good solvent for a (meth) acrylic polymer such as ethyl acetate, isopropyl alcohol, benzene methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, and a solvent having a boiling point of 60 to 120 ° C. is preferable. As the polymerization initiator, radical generators such as azobis compounds such as α, α'-azobisisobutyronitrile and organic peroxide compounds such as benzoyl peroxide are usually used. At this time, if necessary, a catalyst and a polymerization inhibitor can be used in combination, and a (meth) acrylic copolymer having a desired molecular weight can be obtained by adjusting the polymerization temperature and the polymerization time. In terms of adjusting the molecular weight, it is preferable to use a solvent such as mercaptan or carbon tetrachloride. This reaction is not limited to solution polymerization, and other methods such as bulk polymerization and suspension polymerization may be used.

The mass average molecular weight of the base resin having an ethylenically unsaturated group in the side chain [preferably (meth) acrylic copolymer] is preferably about 200,000 to 1,000,000.
If the mass average molecular weight exceeds 1,000,000, when irradiated, the adhesive after irradiation is not flexible and is brittle, so that adhesive residue is left on the surface of the semiconductor chip during peeling. If the mass average molecular weight is less than 200,000, the cohesive force before radiation irradiation is small and the adhesive force is weak, so that the semiconductor chip cannot be held sufficiently during dicing, and there is a possibility of chip fly. In addition, curing is insufficient after irradiation, and adhesive residue is left on the surface of the semiconductor chip during peeling. In order to prevent these as much as possible, the mass average molecular weight is preferably 200,000 or more.
In the present invention, the mass average molecular weight is a polystyrene-reduced mass average molecular weight by a conventional method.

The glass transition point of the base resin having an ethylenically unsaturated group in the side chain is preferably −70 to −10 ° C., more preferably −50 to −10 ° C. If the glass transition point is lower than −70 ° C., the fluidity of the pressure-sensitive adhesive is high and causes residue of the adhesive. This causes grinding water to enter the wafer surface during grinding.

The acid value of the base resin having an ethylenically unsaturated group in the side chain [the number of mg of potassium hydroxide necessary to neutralize free fatty acid present in 1 g of the base resin] is preferably 0.5 to 30, 1 to 20 is more preferable.
The hydroxyl value of the base resin having an ethylenically unsaturated group in the side chain [when 1 g of the base resin is acetylated, the number of mg of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl group] is 5 To 100 is preferable, and 10 to 80 is more preferable.
By doing in this way, the adhesive residue prevention effect at the time of peeling of the adhesive tape for semiconductor wafer processing is further excellent.

In addition, the acid value and the hydroxyl value are prepared by adjusting the (meth) acrylic polymer having a functional group (α) in the side chain, the ethylenically unsaturated group, and the (meth) acrylic polymer. In the step of reacting a compound having a functional group (β) capable of reacting with the functional group (α) of the side chain, it can be prepared as desired by leaving an unreacted functional group.

When the base resin having an ethylenically unsaturated group in the side chain is cured by irradiation, a photopolymerization initiator can be used as necessary. Such photopolymerization initiators include, for example, isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, phenyldimethoxyacetylbenzene, Michler's ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ketone, Examples thereof include 2-hydroxymethylphenylpropane.
The blending amount of these photopolymerization initiators is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the base resin. If the blending amount is too small, the reaction is insufficient, and if the blending amount is too large, the low molecular components increase, thereby affecting the contamination.

The pressure-sensitive adhesive made of a base resin having an ethylenically unsaturated group in the side chain preferably contains a crosslinking agent.
Such a crosslinking agent may be any, but a crosslinking agent selected from the group of polyisocyanates, melamine / formaldehyde resins and epoxy resins is preferred.
Of these, polyisocyanates are preferred in the present invention.

The polyisocyanates are not particularly limited, and examples thereof include 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4′-diphenyl ether diisocyanate, 4,4 ′-[2,2-bis (4 -Phenoxyphenyl) propane] aromatic isocyanate such as diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate Lysine diisocyanate, lysine triisocyanate and the like. Specifically, Coronate L (made by Nippon Polyurethane Co., Ltd., trade name) or the like can be used.

Specific examples of the melamine / formaldehyde resin include Nicalac MX-45 (trade name, manufactured by Sanwa Chemical Co., Ltd.), Melan (trade name, manufactured by Hitachi Chemical Co., Ltd.), and the like.

As the epoxy resin, TETRAD-X (trade name, manufactured by Mitsubishi Chemical Corporation) or the like can be used.

The amount of the crosslinking agent is preferably 0.1 to 10 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the base resin.
After application of the pressure-sensitive adhesive, the base resin forms a cross-linked structure with the cross-linking agent, and the cohesive force of the pressure-sensitive adhesive can be improved.

If the blending amount of the crosslinking agent is less than 0.1 parts by mass, the cohesive force improving effect is not sufficient, and the fluidity of the pressure-sensitive adhesive is high, which causes the adhesive residue. If the amount of the crosslinking agent exceeds 10 parts by mass, the adhesive elastic modulus becomes too high, and the semiconductor wafer surface cannot be protected.

2) Adhesive containing a radiation-polymerizable low molecular weight compound The main component of the adhesive containing a radiation-polymerizable low molecular weight compound is not particularly limited, and is a known chlorinated polypropylene resin or acrylic used for the adhesive. Resin [(meth) acrylic resin], polyester resin, polyurethane resin, epoxy resin and the like can be used.

In the present invention, the base resin of the pressure-sensitive adhesive is preferably an acrylic resin ((meth) acrylic resin), and the side chain that is a raw material for synthesizing the base resin having an ethylenically unsaturated group in the side chain is functional. A (meth) acrylic polymer having a group (α) is particularly preferred.
In this case, the pressure-sensitive adhesive is preferably prepared by appropriately blending a photopolymerization initiator, a curing agent or a crosslinking agent in addition to the acrylic resin as the base resin and the radiation-polymerizable low molecular weight compound.

The mass average molecular weight of the adhesive base resin is preferably about 200,000 to 2,000,000.
In the present invention, it is preferable to contain at least one oligomer having a mass average molecular weight of 1,000 to 20,000 in addition to the base resin. The mass average molecular weight of the oligomer is more preferably 1,100 to 20,000, further preferably 2,000 to 20,000, and particularly preferably 2,000 to 10,000.

As the radiation polymerizable low molecular weight compound, a low molecular weight compound having at least two ethylenically unsaturated groups (radiation polymerizable carbon-carbon double bonds) in a molecule that can be three-dimensionally reticulated by irradiation is used.
In particular, in the present invention, it is preferable that the oligomer is a radiation polymerizable low molecular weight compound having an ethylenically unsaturated group.

Specific examples of radiation-polymerizable low molecular weight compounds include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoester (meth) acrylate, etc. Applicable.

In addition to the above (meth) acrylate compounds, urethane (meth) acrylate oligomers can also be used as radiation polymerizable low molecular weight compounds. Urethane (meth) acrylate oligomers include a polyester compound or a polyether compound such as a polyhydric isocyanate compound (for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3 (Xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4-diisocyanate, etc.) are reacted with a terminal isocyanate urethane prepolymer obtained by reacting (meth) acrylate having a hydroxyl group (for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, etc.) Obtained by.

The radiation polymerizable low molecular weight compound may be used alone or in combination of two or more.
In this invention, it is preferable to use together the oligomer which has two ethylenically unsaturated groups in a molecule | numerator, and the oligomer which has three or more ethylenically unsaturated groups in a molecule | numerator.

The radiation curable pressure-sensitive adhesive can contain a photopolymerization initiator as required. As long as it reacts with the radiation which permeate | transmits a base material as a photoinitiator, there will be no restriction | limiting in particular, A conventionally well-known thing can be used. For example, benzophenones such as benzophenone, 4,4′-dimethylaminobenzophenone, 4,4′-diethylaminobenzophenone, 4,4′-dichlorobenzophenone, acetophenones such as acetophenone, diethoxyacetophenone, phenyldimethoxyacetylbenzene, 2- Anthraquinones such as ethyl anthraquinone and t-butylanthraquinone, 2-chlorothioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzyl, 2,4,5-triarylimidazole dimer (rophine dimer), acridine compound , Acylphosphine oxides, and the like. These can be used alone or in combination of two or more.

The addition amount of the photopolymerization initiator is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 7.5 parts by mass, and further preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the base resin. . When the amount of photopolymerization initiator added is large, radiation curing occurs at multiple points and abruptly, resulting in increased radiation curing shrinkage. Therefore, photopolymerization is performed compared to conventional radiation curing type surface protection adhesive tapes. Reducing the amount of initiator is also useful from the viewpoint of suppressing radiation curing shrinkage.

The pressure-sensitive adhesive preferably contains a curing agent or a crosslinking agent.
Examples of the curing agent or crosslinking agent include polyvalent isocyanate compounds, polyvalent epoxy compounds, polyvalent aziridine compounds, chelate compounds and the like.

The polyvalent isocyanate compound is not particularly limited. For example, 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4′-diphenyl ether diisocyanate, 4,4 ′-[2,2-bis ( 4-phenoxyphenyl) propane] diisocyanate and other aromatic isocyanates, hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane Examples include diisocyanate, lysine diisocyanate, and lysine triisocyanate. Specifically, Coronate L [manufactured by Nippon Polyurethane Industry Co., Ltd., trade name] or the like can be used.

Examples of the polyvalent epoxy compound include epoxy resins, such as ethylene glycol diglycidyl ether, terephthalic acid diglycidyl ester acrylate, and anilines substituted with two glycidyl groups on the N atom.
An example of anilines is N, N′-tetraglycidyl-m-phenylenediamine.

Polyvalent aziridine compounds include tris-2,4,6- (1-aziridinyl) -1,3,5-triazine, tris [1- (2-methyl) -aziridinyl] phosphine oxide, hexa [1- (2- Methyl) -aziridinyl] triphosphatriazine and the like. Examples of the chelate compound include ethyl acetoacetate aluminum diisopropylate and aluminum tris (ethyl acetoacetate).

The blending amount of the curing agent or the crosslinking agent is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5.0 parts by mass, and 0.5 to 4.0 parts by mass with respect to 100 parts by mass of the base resin. Is more preferable.
The pressure-sensitive adhesive of the pressure-sensitive adhesive layer of the present invention comprises at least a base resin having an ethylenically unsaturated group (radiation-polymerizable carbon-carbon double bond and ethylenic double bond) in the side chain, an alicyclic (metal ) Acrylic pressure-sensitive base resin containing no monomer units derived from acrylate and having at least two ethylenically unsaturated groups (radiation polymerizable carbon-carbon double bonds and ethylenic double bonds) in the molecule It has a resin or oligomer selected from urethane acrylate oligomers.

(Adhesive layer thickness)
The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is selected according to the unevenness of the surface of the adherend. For example, when bonding to a bumped wafer, the thickness is about 10 to 50 μm thicker than the bump height. It is preferable. Specifically, it is preferably 10 to 500 μm, more preferably 30 to 400 μm, further preferably 50 to 300 μm, and particularly preferably 50 to 150 μm. The pressure-sensitive adhesive may be a multilayer, and in this case, it is desirable that at least the outermost-layer pressure-sensitive adhesive is a radiation curable pressure-sensitive adhesive that satisfies the configuration of the present invention. For example, when the substrate film that softens by heating is used to follow the surface of the adherend, the total thickness of the layers to be followed is preferably within the above range. It is possible to reduce the thickness to about 100 μm.

(Adhesive layer or adhesive properties)
[Content of ethylenically unsaturated group in radiation curable adhesive]
In the present invention, the content of the ethylenically unsaturated group (radiation polymerizable carbon-carbon double bond) in the radiation curable pressure-sensitive adhesive is 0.2 to 2.0 mmol / g.
The ethylenically unsaturated group in the radiation curable adhesive is a compound having an ethylenically unsaturated group contained in the radiation curable adhesive (a polymer such as a base resin having an ethylenically unsaturated group in the side chain). , Radiation polymerizable low molecular weight compound) is the total of all ethylenically unsaturated groups, and is the total number of moles of ethylenically unsaturated groups per unit g of the radiation curable pressure-sensitive adhesive.

The content of the ethylenically unsaturated group in the radiation curable pressure-sensitive adhesive is preferably 0.2 to 1.8 mmol / g, more preferably 0.2 to 1.5 mmol / g, and 0.5 to 1.5 mmol. / G is more preferable.
When the pressure-sensitive adhesive is a multilayer, it is preferable to satisfy the above range when all the pressure-sensitive adhesives are regarded as one layer, and it is more preferable that each layer satisfies the above range.

In the case of a base resin having an ethylenically unsaturated group in the side chain, the content of the ethylenically unsaturated group in the radiation curable pressure-sensitive adhesive is a (meth) acrylic polymer used when synthesizing the base resin. The amount of the functional group (β) capable of reacting with the side chain functional group (α) and the amount of the compound having an ethylenically unsaturated group and the number of ethylenically unsaturated groups can be adjusted. It can adjust with the number and compounding quantity of the ethylenically unsaturated group which has.

The content of the ethylenically unsaturated group in the radiation curable pressure-sensitive adhesive can be determined by the amount of the compound or synthetic raw material used as described above, but the iodine value of the radiation curable pressure-sensitive adhesive [100 g of base resin G number of iodine (I ₂ ) to be added] and the molecular weight of I ₂ is 253.8, and thus this value can be obtained by unit conversion to mmol / g.

[Adhesion after UV curing to SUS plate]
In the radiation curable pressure-sensitive adhesive (pressure-sensitive adhesive layer) of the present invention, the adhesive strength after UV curing with respect to the SUS plate is preferably 0.3 to 3.0 N / 25 mm, more preferably 0.5 to 3.0 N / 25 mm. 0.5 to 1.5 is more preferable.
The term “after ultraviolet curing” means that the entire pressure-sensitive adhesive layer has been cured by irradiation with ultraviolet rays so as to have an integrated irradiation amount of 500 mJ / cm ² .

Specifically, it can be determined as follows.
Three test pieces each having a width of 25 mm and a length of 150 mm were collected from an adhesive tape for semiconductor wafer processing before radiation irradiation, and the test pieces were finished with JIS G 4305 finished with No. 280 water-resistant abrasive paper defined in JIS R 6253. A 2 kg rubber roller is reciprocated three times on a SUS steel plate having a thickness of 1.5 mm to 2.0 mm, and left for 1 hour, and then cured by irradiating with 500 mJ / cm ² ultraviolet rays. After curing, using a tensile tester conforming to JIS B 7721 whose measured value is in the range of 15 to 85% of its capacity (for example, tensile tester manufactured by Instron: Twin Column Tabletop Model 5567) The adhesive strength is measured at a normal temperature (25 ° C.) and a humidity of 50% by a 90 ° peeling method at 50 mm / min, and an average value of three points is obtained.

The adhesive strength after UV curing on the SUS plate is the molecular weight of the pressure-sensitive adhesive composition, the type and amount of the radiation-polymerizable low molecular weight compound, the type and amount of the additive including the crosslinking agent, and the thickness of the radiation-curable pressure-sensitive adhesive layer. By adjusting the thickness and the like as appropriate, the scope of the present invention can be achieved.
If the apparent adhesive force to the SUS plate is too small, curing shrinkage also increases, so that the peel force from an adherend having a large surface irregularity such as a bump wafer is increased. If the apparent adhesive force to the SUS plate is too large, the radiation curing is insufficient and peeling failure or adhesive residue occurs.

[Curing shrinkage stress of adhesive]
The radiation curable pressure-sensitive adhesive (pressure-sensitive adhesive layer) of the present invention has a curing shrinkage stress of preferably 300 gf or less, more preferably 50 to 250 gf, and even more preferably 50 to 200 gf.

The curing shrinkage stress of the pressure-sensitive adhesive can be determined as follows.
The curing shrinkage stress of the pressure-sensitive adhesive (pressure-sensitive adhesive layer) is obtained by laminating a coated and dried pressure-sensitive adhesive on a release-treated separator, and punching it into a pellet with a thickness of about 2 mm and a diameter of Φ8 mm. Using a curing shrinkage measuring device (for example, resin curing shrinkage rate stress measuring device “CUSTRON” manufactured by Matsuo Sangyo Co., Ltd.), an ultraviolet ray of 500 mJ / cm ² is irradiated at an illuminance of 50 mW from an initial load of −60 gf. The curing shrinkage stress after 5 minutes is measured. Since the curing shrinkage stress is a force in the compression direction, the force is opposite to the initial load. Therefore, the initial load is expressed as minus. In the present invention, the curing shrinkage stress represents the shrinkage stress when the initial load of −60 gf is 0. For example, when the initial load is −60 gf and the stress value after ultraviolet irradiation is +150 gf, the cure shrinkage stress is 150 gf− ( −60 gf) = 210 gf.

The curing shrinkage stress decreases as the amount of ethylenically unsaturated groups or initiator decreases. Moreover, since the ethylenically unsaturated group is cross-linked to the base polymer or the molecular weight of the ethylenically unsaturated group is increased, the movement of the ethylenically unsaturated group during radiation cross-linking can be suppressed, so that the curing shrinkage stress can be suppressed. By reducing the curing shrinkage stress, biting and catching on the adherend surface during radiation curing shrinkage can be reduced, so that peeling failure and adhesive residue can be reduced.

<Other layers>
The pressure-sensitive adhesive tape for processing a semiconductor wafer of the present invention may be provided with other layers such as an adhesive layer.

(Adhesive layer)
The adhesive layer is provided on the pressure-sensitive adhesive layer.
In order to cure, the adhesive layer contains an epoxy resin having two or more epoxy groups in the molecule, and is bisphenol type, naphthalene type, phenol novolac type, cresol novolak type, phenol aralkyl type, biphenyl type. It is preferable to contain at least one epoxy resin selected from the group consisting of triphenylmethane type and dicyclopentadiene type.

Further, the adhesive layer includes a curing agent and a curing accelerator that are cured by reacting with the epoxy resin.
Examples of the curing agent and curing accelerator include phenolic curing agents, acid anhydrides, amine compounds, imidazoles, and phosphines.

The adhesive layer preferably contains a polymer compound, such as phenoxy resin, polyimide resin, polyamide resin, polycarbodiimide resin, cyanate ester resin, acrylic resin, polyester resin, polyethylene resin, polyethersulfone resin, poly Examples include ether imide resins, polyvinyl acetal resins, urethane resins, and acrylic rubbers.

The adhesive layer may contain an inorganic filler.
The inorganic filler only needs to have insulating properties and thermal conductivity. For example, nitrogen compounds (boron nitride, aluminum nitride, silicon nitride, carbon nitride, titanium nitride, etc.), carbon compounds (silicon carbide, fluorine carbide, Boron carbide, titanium carbide, tungsten carbide, diamond, etc.), metal oxides (silica, alumina, magnesium oxide, zinc oxide, beryllium oxide, etc.) and the like.

The thickness of the adhesive layer is not particularly limited, but can be appropriately selected depending on the height of the bump to be embedded. For example, it can be preferably used if it is as thin as 10 to 20 μm from the height of the bump.

The adhesive layer is provided by coating the adhesive composition on the release film and bonding it to the adhesive layer of the base film.

<Release liner>
When the adhesive tape for semiconductor wafer processing does not have an adhesive layer, it may have a release liner on the adhesive layer. As the release liner, a polyethylene terephthalate film subjected to silicone release treatment or the like is used. If necessary, a polypropylene film that is not subjected to silicone release treatment may be used.

<< Semiconductor wafer processing method >>
The semiconductor wafer processing method of the present invention is a semiconductor wafer processing method using the semiconductor wafer processing adhesive tape of the present invention.
The adhesive tape for semiconductor wafer processing of the present invention may be used in any process as long as it is a semiconductor wafer processing process. For example, a semiconductor wafer back surface grinding process, a dicing process, a dicing die bonding process, and the like are preferable.

The adhesive tape for processing a semiconductor wafer of the present invention is preferably used by being bonded to a semiconductor wafer surface having surface irregularities of 10 μm or more.
It is more preferable to apply to semiconductor wafers having surface irregularities (bump (electrode) height) of 20 to 400 μm, and more preferable to apply to 50 to 150 μm.

The arrangement density (high density) of bumps on the surface of the semiconductor wafer is not particularly limited, but a pitch more than twice the height of the bumps (from the apex in the height direction of the bumps to the next arranged bumps) Applicable to the distance to the apex in the height direction). It is also used for semiconductor wafers in which bumps are uniformly arranged on the entire surface.

The thickness of the semiconductor wafer is preferably 20 to 500 μm, more preferably 50 to 200 μm, and even more preferably 80 to 200 μm in terms of the thickness of the semiconductor wafer that has been back-ground by a processing method using a semiconductor wafer processing adhesive tape.
By using the adhesive tape for processing a semiconductor wafer of the present invention, a thin film semiconductor wafer can be obtained with a high yield. This semiconductor wafer processing method is suitable as a manufacturing method for thin-film grinding of a semiconductor wafer with an electrode of 50 μm or less.

The method for processing a semiconductor wafer of the present invention includes a step of peeling the pressure-sensitive adhesive tape for processing a semiconductor wafer by irradiating with radiation, particularly ultraviolet rays, after the pressure-sensitive adhesive tape for processing a semiconductor wafer of the present invention is bonded to the surface of the semiconductor wafer. It is preferable.

Specifically, first, the adhesive tape for semiconductor wafer processing of the present invention is bonded to the circuit pattern surface (front surface) of the semiconductor wafer so that the adhesive layer becomes the bonding surface. Next, the surface side of the semiconductor wafer having no circuit pattern is ground until the thickness of the semiconductor wafer reaches a predetermined thickness, for example, 10 to 200 μm. After that, place the adhesive tape for semiconductor wafer processing on the heating adsorption table with the adhesive tape facing down, and in that state, apply the dicing die bonding film to the ground surface without the circuit pattern of the semiconductor wafer. May be combined.
A dicing process is performed, and then a heat seal type (thermal fusion type) or adhesive type release tape is adhered to the back surface of the base film of the semiconductor wafer processing adhesive tape, and the semiconductor wafer processing adhesive tape is attached to the semiconductor wafer. Peel off.

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

(Preparation of adhesive composition)
Adhesive compositions 2A to 2G were prepared as follows.

1) Preparation of pressure-sensitive adhesive composition 2A For 100 parts by mass of a copolymer consisting of 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate and 5 parts by mass of methacrylic acid and having a molecular weight of 500,000, acrylate 5 Functional and mass average molecular weight 1,400 urethane acrylate oligomer 100 parts by mass and polyisocyanate coronate L [manufactured by Nippon Polyurethane Industry Co., Ltd.] 4.0 parts by mass, as a photopolymerization initiator SPEEDCURE BKL [manufactured by DKSH Japan Co., Ltd.] ] 5.0 parts by mass was added and mixed to obtain an adhesive composition 2A.

2) Preparation of pressure-sensitive adhesive composition 2B With respect to 100 parts by mass of a copolymer consisting of 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate, and 5 parts by mass of methacrylic acid, and having a mass average molecular weight of 500,000, 100 parts by mass of a urethane acrylate oligomer having a acrylate trifunctional weight average molecular weight of 2,000 and 4.0 parts by mass of polyisocyanate coronate L [manufactured by Nippon Polyurethane Industry Co., Ltd.], SPEEDCURE BKL [DKSH Japan Co., Ltd. as a photopolymerization initiator ) Made] 5.0 parts by mass was added and mixed to obtain an adhesive composition 2B.

3) Preparation of pressure-sensitive adhesive composition 2C For 100 parts by mass of a copolymer consisting of 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate, and 5 parts by mass of methacrylic acid, and having a mass average molecular weight of 500,000. 100 parts by mass of acrylate trifunctional urethane acrylate oligomer having a mass average molecular weight of 6,000 and 4.0 parts by mass of polyisocyanate coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), SPEEDCURE BKL [DKSH Japan, Inc. as a photopolymerization initiator ) Made] 5.0 parts by mass was added and mixed to obtain a pressure-sensitive adhesive composition 2C.

4) Preparation of pressure-sensitive adhesive composition 2D For 100 parts by mass of a copolymer having a molecular weight of 500,000 comprising 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate, and 5 parts by mass of methacrylic acid, acrylate 5 Functional and weight average molecular weight 1,400 urethane acrylate oligomer 80 parts by mass and bifunctional acrylate weight average molecular weight 3,000 urethane acrylate oligomer and polyisocyanate coronate L [manufactured by Nippon Polyurethane Industry Co., Ltd.] 4.0 5.0 parts by mass of SPEDCURE BKL [manufactured by DKSH Japan Co., Ltd.] as a photopolymerization initiator was added and mixed to obtain an adhesive composition 2D.

5) Preparation of pressure-sensitive adhesive composition 2E For 100 parts by mass of a copolymer consisting of 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate, and 5 parts by mass of methacrylic acid, and having a mass average molecular weight of 500,000, 100 parts by weight of urethane acrylate oligomer with a weight average molecular weight of 1,000 acrylate and 4.0 parts by weight of polyisocyanate coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), SPEEDCURE BKL [DKSH Japan Co., Ltd. as a photopolymerization initiator ) Made] 5.0 parts by mass was added and mixed to obtain an adhesive composition 2E.

5) Preparation of pressure-sensitive adhesive composition 2F With respect to 100 parts by mass of a copolymer having a mass average molecular weight of 500,000 consisting of 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate, and 5 parts by mass of methacrylic acid, 100 parts by mass of urethane acrylate oligomer having a weight average molecular weight of 800 and a polyisocyanate coronate L [manufactured by Nippon Polyurethane Industry Co., Ltd.] 4.0 parts by mass, SPEDCURE BKL [manufactured by DKSH Japan Co., Ltd.] as a photopolymerization initiator ] 5.0 parts by mass was added and mixed to obtain an adhesive composition 2F.

6) Preparation of pressure-sensitive adhesive composition 2G For 100 parts by mass of a copolymer consisting of 80 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl acrylate, and 5 parts by mass of methacrylic acid, and having a mass average molecular weight of 500,000. 20 parts by mass of acrylate trifunctional urethane acrylate oligomer having a weight average molecular weight of 3,000 and 2.0 parts by mass of polyisocyanate coronate L [manufactured by Nippon Polyurethane Industry Co., Ltd.], SPEEDCURE BKL [DKSH Japan, Inc. as a photopolymerization initiator ) Made] 5.0 parts by mass was added and mixed to obtain an adhesive composition 2G.

Example 1
An adhesive composition 2A was applied on a polyethylene terephthalate (PET) separator having a thickness of 38 μm so that the thickness after drying was 90 μm, dried, and then an ethylene-vinyl acetate copolymer having a thickness of 140 μm. An adhesive tape for processing a semiconductor wafer having a thickness of 230 μm was manufactured by laminating with a base film made of (EVA) film.

Example 2
In Example 1, the adhesive tape for semiconductor wafer processing was manufactured like Example 1 except having changed adhesive composition 2A into adhesive composition 2B.

Example 3
In Example 1, a pressure-sensitive adhesive tape for semiconductor wafer processing was produced in the same manner as Example 1 except that the pressure-sensitive adhesive composition 2A was changed to the pressure-sensitive adhesive composition 2C.

Example 4
In Example 1, the adhesive tape for semiconductor wafer processing was manufactured like Example 1 except having changed adhesive composition 2A into adhesive composition 2D.

Comparative Example 1
In Example 1, the adhesive tape for semiconductor wafer processing was manufactured like Example 1 except having changed adhesive composition 2A into adhesive composition 2E.

Comparative Example 2
In Example 1, the adhesive tape for semiconductor wafer processing was manufactured like Example 1 except having changed adhesive composition 2A into adhesive composition 2F.

Comparative Example 3
In Example 1, the adhesive tape for semiconductor wafer processing was manufactured like Example 1 except having changed adhesive composition 2A into adhesive composition 2G.

(Evaluation test)
In the adhesive tapes for semiconductor wafer surface processing of Examples 1 to 4 and Comparative Examples 1 to 3, the molar content of the ethylenically unsaturated group (carbon-carbon double bond) contained in the radiation curable adhesive is the raw material used. Calculated from
Moreover, the measurement of the peeling force after the radiation irradiation with respect to SUS, the measurement of the curing shrinkage stress, the evaluation of the peeling force, the evaluation of dust intrusion and the evaluation of the adhesive residue were performed.

[Measurement of peeling force after irradiation with SUS]
In each of the semiconductor wafer processing pressure-sensitive adhesive tapes produced above, three test pieces each having a width of 25 mm and a length of 150 mm were sampled from the semiconductor wafer processing pressure-sensitive adhesive tape before irradiation, and the test pieces are defined in JIS R 6253. A 2 kg rubber roller was pressed on a SUS steel plate with a thickness of 1.5 mm to 2.0 mm specified in JIS G 4305, finished with 280th water-resistant abrasive paper, and pressed for 3 hours. Using a tensile tester (Instron's tensile tester: Twin Column Tabletop Model 5567) conforming to JIS B 7721, which falls within the range of 15 to 85%, at room temperature by a peeling method of 90 ° at a tensile speed of 50 mm / min. The adhesive strength was measured at 25 ° C. and a humidity of 50%, and an average value of three points was obtained.
Thereafter, three test specimens similar to the above were collected from the remaining part of the adhesive tape for processing semiconductor wafers, bonded to a SUS steel plate in the same manner as described above, and allowed to stand for 1 hour, and then irradiated with 500 mJ / cm ² of ultraviolet rays. After curing, the adhesive strength of the semiconductor wafer processing adhesive tape after ultraviolet irradiation was measured in the same manner as described above, and the average value of three points was obtained.
Among these, the peel strength after ultraviolet curing is shown in Table 1 below.

[Measurement of curing shrinkage stress of adhesive]
A cured and shrinkage measuring device [Plastic made by Matsuo Sangyo Co., Ltd.] is used by laminating a coated and dried adhesive on a release-treated separator and punching it into a pellet with a thickness of about 2 mm and a diameter of Φ8 mm. Curing shrinkage stress measuring apparatus “CUSTRON” was used, and irradiation with 500 mJ / cm ² of ultraviolet light was performed at an illuminance of 50 mW from an initial load of −60 gf, and the curing shrinkage stress after 5 minutes was measured. Since the curing shrinkage stress is a force in the compression direction, the force is opposite to the initial load. Therefore, the initial load is expressed as minus. The curing shrinkage stress represents the shrinkage stress when the initial load −60 gf is 0. For example, when the initial load −60 gf and the stress value after ultraviolet irradiation is +150 gf, the curing shrinkage stress is 150 gf − (− 60 gf) = 210 gf.

(Semiconductor wafer processing and evaluation of peeling force)
Each of the semiconductor wafer processing pressure-sensitive adhesive tapes manufactured above was bonded to an 8-inch diameter semiconductor wafer having bumps with a height of 75 μm on the surface at a bonding temperature of 25 ° C. Then, the back surface of the bumped semiconductor wafer bonded by the above-mentioned adhesive tape for processing a semiconductor wafer was ground by two pieces to a thickness of 200 μm using DFG8760 (trade name) manufactured by DISCO Corporation. Irradiate 500 mJ / cm ² of ultraviolet light onto the ground semiconductor wafer with adhesive tape for processing semiconductor wafers, and peel off the adhesive tape for processing semiconductor wafers using an Instron tensile tester (Twin Column Tabletop Model 5567). In the peeling force when the width at the time of peeling became the maximum (200 mm), the following criteria were evaluated.
In Table 1, this is simply indicated as “peeling force”.

Evaluation criteria A: 20 N / 200 mm or less B: Over 20 N / 200 mm and 50 N / 200 mm or less C: Over 50 N / 200 mm

[Evaluation of dust penetration and adhesive residue]
The semiconductor wafer after peeling was observed with a microscope to examine dust intrusion and adhesive residue.
This result was evaluated according to the following criteria.

Evaluation standard of dust intrusion A: No dust intrusion was observed.
B: Dust intrusion was slightly observed.
C: Dust intrusion was clearly observed.

Evaluation criteria for adhesive residue A: No adhesive residue was observed.
B: Adhesive residue was faintly observed.
C: The glue residue was clearly observed.

¡In rank of peeling force, dust intrusion, and glue residue, C rank has not reached the target level.

The results obtained are summarized in Table 1 below.

From Table 1 above, the adhesive tape for semiconductor wafer processing of Examples 1 to 4 in which the content of ethylenically unsaturated groups in the adhesive satisfies the range of 0.2 to 2.0 mmol / g has a curing shrinkage stress. The peel force for the SUS plate can be sufficiently reduced to 3 N / 25 mm or less within a range that can be suppressed to 300 gf or less, so that the peel force for bump wafers with large surface irregularities can be suppressed to 50 N / 200 mm or less, which is excellent. I understand.
On the other hand, in the adhesive tapes for processing semiconductor wafers of Comparative Examples 1 and 2, the content of ethylenically unsaturated groups in the adhesive exceeds 2.0 mmol / g, and the curing shrinkage stress is as high as 330 gf and 380 gf. For this reason, the peel force is also higher than 50 N / 200 mm. Moreover, in the adhesive tape for processing a semiconductor wafer of Comparative Example 2, an adhesive residue was observed. Conversely, the pressure-sensitive adhesive tape for semiconductor wafer processing of Comparative Example 3 in which the content of ethylenically unsaturated groups in the pressure-sensitive adhesive is less than 0.2 mmol / g has a low curing shrinkage stress of 120 gf. Since the curing was insufficient, the peel strength against SUS was as high as 5.2 N / 25 mm, and dust intrusion and adhesive residue were observed, both of which were insufficient.
As described above, the pressure-sensitive adhesive tape for processing a semiconductor wafer of the present invention is excellent in evaluation of both dust intrusion and adhesive residue, and in particular, a semiconductor wafer having a surface irregularity of 75 μm and a bump height of 10 μm or more. It turns out that it is excellent as an adhesive tape for semiconductor wafer processing used by bonding to the surface.

While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified and are contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted widely.

This application claims priority based on Japanese Patent Application No. 2016-054269 filed in Japan on March 17, 2016, the contents of which are hereby incorporated herein by reference. Capture as part.

Claims

A pressure-sensitive adhesive tape for processing a semiconductor wafer having an adhesive layer on at least one surface of a base film, wherein the adhesive of the adhesive layer is a radiation-curable adhesive, and at least has an ethylenically unsaturated side chain A base resin having a group (radiation-polymerizable carbon-carbon double bond and ethylenic double bond), an acrylic pressure-sensitive base resin containing no monomer unit derived from an alicyclic (meth) acrylate, and a molecule A resin or oligomer selected from urethane acrylate oligomers having at least two ethylenically unsaturated groups (radiation polymerizable carbon-carbon double bonds and ethylenic double bonds), and the pressure-sensitive adhesive is ethylenically unsaturated. A pressure-sensitive adhesive tape for processing semiconductor wafers, having a saturated group of 0.2 to 2.0 mmol / g.
The acrylic pressure-sensitive base resin that does not contain a monomer unit derived from the alicyclic (meth) acrylate is an alkyl ester that may have a functional group of (meth) acrylic acid, acrylic acid, and methacrylic acid. The pressure-sensitive adhesive tape for semiconductor wafer processing according to claim 1, wherein the pressure-sensitive adhesive tape comprises only a monomer unit to be led.
The functional group of the alkyl ester which may have a functional group of (meth) acrylic acid is a carboxy group, a hydroxyl group, an amino group, a mercapto group, a cyclic acid anhydride group, an epoxy group, an isocyanate group (-N = The pressure-sensitive adhesive tape for processing a semiconductor wafer according to claim 2, wherein C = O).
The pressure-sensitive adhesive tape for semiconductor wafer processing according to any one of claims 1 to 3, wherein the mass average molecular weight of at least one of the oligomers is 1,100 to 20,000.
The pressure-sensitive adhesive tape for semiconductor wafer processing according to any one of claims 1 to 3, wherein the at least one oligomer has a mass average molecular weight of 1,400 to 20,000.
6. The oligomer according to claim 1, wherein the oligomer is a mixture of an oligomer having at least two ethylenically unsaturated groups in the molecule and an oligomer having three or more ethylenically unsaturated groups in the molecule. The adhesive tape for semiconductor wafer processing of Claim 1.
The pressure-sensitive adhesive tape for processing a semiconductor wafer according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive has 0.72 to 2.0 mmol / g of the ethylenically unsaturated group.
The adhesive tape for semiconductor wafer processing according to any one of claims 1 to 7, wherein the adhesive contains a polyvalent isocyanate compound.
9. The adhesive strength of the SUS plate after UV curing is 0.3 to 3.0 N / 25 mm, and the curing shrinkage stress is 300 gf or less. Adhesive tape for semiconductor wafer processing.
10. The semiconductor wafer processing pressure-sensitive adhesive tape according to claim 1 is bonded to a semiconductor wafer surface having a surface irregularity of 10 μm or more, and then irradiated with ultraviolet rays to peel off the semiconductor wafer processing pressure-sensitive adhesive tape. A method for processing a semiconductor wafer, comprising the step of: