WO2015146856A1

WO2015146856A1 - Adhesive tape for semiconductor wafer processing and method for processing semiconductor wafer

Info

Publication number: WO2015146856A1
Application number: PCT/JP2015/058601
Authority: WO
Inventors: 祥文岡; 具朗内山
Original assignee: 古河電気工業株式会社
Priority date: 2014-03-24
Filing date: 2015-03-20
Publication date: 2015-10-01
Also published as: JP5697061B1; JP2015185692A; TW201539630A; KR101766174B1; CN106104767A; TWI590361B; KR20160125524A; CN106104767B

Abstract

Provided is an adhesive tape (10) for semiconductor wafer processing stuck to the front surface of a semiconductor wafer having convexities and concavities equal to or higher than 80 µm, and used in a step of grinding the rear surface of the semiconductor wafer, wherein the adhesive tape is configured to have an adhesive layer (3) on a base material film (1), the adhesive layer (3) having a thickness of 25 % to 90 % of the height of the front surface convexities and concavities of the semiconductor wafer and having a thickness equal to or smaller than 25 % of the total thickness of the adhesive tape (10) for semiconductor wafer processing. Also provided is a method for processing the 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 used for processing a semiconductor wafer when manufacturing a semiconductor device such as a silicon wafer, and protects the surface of the semiconductor wafer or fixes the semiconductor wafer or the like. The present invention relates to a semiconductor wafer processing adhesive tape used for back grinding and a semiconductor wafer processing method.
More specifically, there is no adhesive residue from the surface of the semiconductor wafer to the electrode, no dropping of the electrode, etc., from the process of tape bonding to the surface of the semiconductor wafer having a protrusion such as an electrode of 10 μm or more on the surface, and the semiconductor wafer. The present invention relates to a semiconductor wafer processing pressure-sensitive adhesive tape and a method for processing a semiconductor wafer.

The process of processing a semiconductor wafer or the like into a semiconductor chip and mounting it on an electronic device is, for example, a process of attaching a semiconductor wafer surface protective tape to the pattern surface of the semiconductor wafer, grinding the back surface of the semiconductor wafer, and reducing the thickness. A step of mounting a semiconductor wafer that has been ground and thinned to a dicing tape in the above step, a step of peeling the adhesive tape for processing the semiconductor wafer from the semiconductor wafer, a step of dividing the semiconductor wafer by dicing, After a die bonding step for bonding the semiconductor chip to the lead frame, a molding step for sealing the semiconductor chip with a resin for external protection is performed.

There are roughly two types of adhesive tapes for processing semiconductor wafers. There are a radiation curable type in which the adhesive strength is remarkably lowered after irradiation and the peeling is easy, and a pressure sensitive type in which the adhesive strength does not change during the wafer back surface grinding and at the time of peeling, that is, the adhesive strength does not change by radiation.
These adhesive tapes for processing semiconductor wafers have been proposed in which an adhesive layer mainly composed of (meth) acrylic polymer is provided on a polyolefin base film such as ethylene-vinyl acetate copolymer. (For example, refer to Patent Document 1).
In addition, when an electrode having a height of 50 μm or more exists on the surface of the semiconductor wafer, the step of bonding the processing adhesive tape to the conductor wafer may be performed while heating at about 40 ° C. to 70 ° C. Similarly, during peeling, peeling may be performed while heating to lighten the peeling.

The semiconductor wafer surface pattern has various electronic circuits and electrodes, a protective film such as polyimide that protects them, and a scribe line that is a groove into which the blade cuts during the dicing process of dividing the semiconductor wafer into chips. The surface of the semiconductor wafer is not smooth and has steps and irregularities of several μm to several tens of μm. Here, the method of grinding the back surface of the semiconductor wafer, dicing the wafer having a reduced thickness, and then picking it up and bonding it via the chip surface electrode is called flip chip bonding. In this joining method, the unevenness of the electrode portion is very large and has a height of about 10 μm to 300 μm.

Such steps vary depending on the type of semiconductor wafer and device, but it is expected that the step will be in close contact with the step on the surface of the semiconductor wafer by bonding an adhesive tape for processing the semiconductor wafer. However, when the level difference of the semiconductor wafer is large, particularly when the electrode height is very high, or when the adhesive elastic modulus is high, the followability to the semiconductor wafer surface is insufficient. As a result, a phenomenon called seapage occurs in which grinding water enters the gap between the semiconductor wafer and the adhesive tape for processing the semiconductor wafer during the back grinding process. Also, especially in semiconductor wafers intended for flip chip bonding with electrodes, if the electrodes cannot be completely filled with tape, cracks may occur starting from the locations where bubbles remained during back grinding, During processing, bubbles gather at the center of the semiconductor wafer, and the thickness of the silicon at the corresponding portion is reduced, causing a phenomenon called a navel. In addition, unevenness called dimples may occur due to locally different semiconductor wafer thicknesses at the respective electrode portions.

As described above, the generation of seapage causes the semiconductor wafer processing adhesive tape to peel off from the semiconductor wafer, causing cracks in the semiconductor wafer starting from that location, leading to breakage, or infiltration of the surface of the semiconductor wafer by intrusion water. Contamination and adhesion of glue occur, causing the yield to deteriorate significantly.

For the generation of seapage, a method for improving the adhesion to the semiconductor wafer surface by increasing the thickness of the pressure-sensitive adhesive layer or lowering the elastic modulus of the pressure-sensitive adhesive layer (for example, see Patent Document 2) is known. ing. Further, the same effect can be expected by increasing the adhesive strength.

However, in the above method, when the height of the electrode on the surface of the semiconductor wafer pattern is as large as 10 μm or more, it does not adhere completely, and the above sea page problem cannot be solved. In addition, when there is a gap between the pressure-sensitive adhesive and the semiconductor wafer pattern surface electrode, oxygen intervenes in the gap to cause curing inhibition by oxygen during ultraviolet irradiation, and a part of the pressure-sensitive adhesive is formed on the surface of the semiconductor wafer. There is a problem that a phenomenon called adhesive residue that remains is likely to occur. In the case where adhesive residue is generated, it may cause a problem in wire bonding or electrical connection in a later process.

By the way, in recent years when semiconductor wafers have become thinner, thin film grinding is generally used to reduce the thickness of the semiconductor wafer to 100 μm or less, particularly in semiconductor memory applications. A device wafer is thinned to a predetermined thickness by backside grinding, and then formed into chips in a dicing process. A plurality of chips are stacked, and after wire connection between the substrate and the chip, it is sealed with a resin to become a product. .
On the other hand, pasty resin has been conventionally applied to the backside of semiconductor wafers as an adhesive. However, in order to reduce the thickness of chips, reduce the size of chips, and simplify processes, adhesives and adhesives ( A process in which a dicing die bond sheet on which a bonding sheet for die bonding) is laminated is bonded to the back surface (grind surface) of a semiconductor wafer and cut together with the semiconductor wafer in a dicing process has become common (for example, Patent Documents). 3). In this method, since the adhesive with a uniform thickness is cut to the same size as the chip, a process such as application of an adhesive is unnecessary, and an apparatus similar to a conventional dicing tape can be used. It is good.

Especially in the case of a semiconductor wafer having an electrode with a height of 10 μm or more for the purpose of electrical connection, the polyimide coating layer applied as an insulating layer is very thick, and the residual stress after heat curing of the polyimide resin layer is also large. After the semiconductor wafer is thinned, the warp is large and the warping stress is strong.

Here, at the time of dicing die bond sheet bonding, the semiconductor wafer processing adhesive tape is stuck to the chuck table while being bonded to the semiconductor wafer surface, and the dicing die bond sheet is bonded to the semiconductor wafer processing adhesive. The tape is peeled off. In order to make this dicing die-bonding sheet adhere to the semiconductor wafer, heating is required at the time of bonding, but in recent years, heating at a higher temperature (˜80 ° C.) may be required. For this reason, when the softening point and melting | fusing point of the base film layer of the back surface of the adhesive tape for semiconductor wafer processing are low, there exists a risk of melt-fixing with a chuck table.

Japanese Patent Laid-Open No. 2000-8010 JP 2002-53819 A JP 2007-53325 A

The present invention solves the above-described problems, and after processing a semiconductor wafer, more specifically, a back surface grinding process and a tape peeling process for a silicon wafer or the like, dimples and surface contamination (mainly due to seapage) generated on the back surface of the semiconductor wafer. It is an object of the present invention to provide an adhesive tape for processing a semiconductor wafer, which is excellent in adhesion to a semiconductor wafer having a high unevenness on the surface of the semiconductor wafer and capable of grinding a wafer thin film.

As a result of earnestly examining the above problems, the present inventor has found that the pressure-sensitive adhesive tape provided with the pressure-sensitive adhesive layer on the base film has a relationship between the uneven height of the surface of the semiconductor wafer and the thickness of the pressure-sensitive adhesive layer, and the relaxation property to the external stress of the tape. It has been found that it is important, and further examination has made it possible to significantly reduce the generation of seapage at the time of semiconductor wafer back grinding, particularly the generation of dimples at the back grinding and cracking of the semiconductor wafer in the case of thin film grinding. The present invention has been made based on this finding.

That is, the said subject was achieved by the following means.
(1) An adhesive tape for processing a semiconductor wafer used in a step of bonding to a semiconductor wafer having an unevenness with a height of 80 μm or more on the surface and grinding the back surface of the semiconductor wafer,
Having a pressure-sensitive adhesive layer on the base film, the thickness of the pressure-sensitive adhesive layer being 25% to 90% of the uneven height on the surface of the semiconductor wafer; and
The pressure-sensitive adhesive layer has a thickness of 25% or less of the entire thickness of the pressure-sensitive adhesive tape for semiconductor wafer processing.
(2) The stress reduction rate when compressive stress is applied in the thickness direction of the pressure-sensitive adhesive tape for semiconductor wafer processing measures the amount of displacement when a compressive stress of 50 N is applied, and the compressive stress with respect to the stress value when the compressive stress reaches 50 N The pressure-sensitive adhesive tape for processing a semiconductor wafer according to (1), wherein the pressure-sensitive adhesive tape is 40% or more calculated from a ratio of stress values 180 seconds after reaching 50N.
(3) The semiconductor wafer surface unevenness is an electrode, and the total value of the semiconductor wafer processing adhesive tape and the semiconductor wafer thickness excluding the surface electrode before the semiconductor wafer bonding is A, and the semiconductor wafer processing after the semiconductor wafer bonding (1) or (2) adhesive tape for semiconductor wafer processing, wherein A / B is 0.95 or more when the total thickness of the adhesive tape and semiconductor wafer laminate is B .
(4) The adhesive tape for processing a semiconductor wafer according to any one of (1) to (3), wherein the base film is made of an ultraviolet curable resin.
(5) A method for processing a semiconductor wafer using an adhesive tape for processing a semiconductor wafer that is bonded to a semiconductor wafer having irregularities with a height of 80 μm or more on the surface,
The semiconductor wafer processing pressure-sensitive adhesive tape has a pressure-sensitive adhesive layer on a base film, and the thickness of the pressure-sensitive adhesive layer is 25% or less of the total thickness of the semiconductor wafer processing pressure-sensitive adhesive tape,
The pressure-sensitive adhesive layer has a thickness of 25% to 90% of the uneven height of the semiconductor wafer surface,
A method for processing a semiconductor wafer, comprising a step of bonding the semiconductor wafer processing adhesive tape to the semiconductor wafer.

The adhesive tape for processing a semiconductor wafer according to the present invention is used for processing a thin semiconductor wafer, more specifically, a silicon wafer having an electrode having a height of 10 μm or more, particularly exceeding 80 μm for the purpose of electrical connection on the surface, etc. Back grinding (BG) tape lamination in semiconductor back grinding, and semiconductor wafer back grinding, while ensuring adhesion to the surface of the semiconductor wafer, it also has excellent relaxation properties against external stress and performs thin film grinding without dimples or cracks It is possible to provide a semiconductor wafer processing pressure-sensitive adhesive tape and a semiconductor wafer processing method that can be removed without any problems in the subsequent semiconductor wafer processing pressure-sensitive adhesive tape peeling step.

The above and other features and advantages of the present invention will become more apparent from the following description with reference to the accompanying drawings as appropriate.

It is sectional drawing which shows typically the state by which the adhesive tape for semiconductor wafer processing of this invention was bonded by the semiconductor wafer pattern surface about preferable one Embodiment of this invention.

Hereinafter, the present invention will be described in detail.
The pressure-sensitive adhesive tape 10 for processing a semiconductor wafer of the present invention has a pressure-sensitive adhesive layer 3 on the base film 1, and preferably has an anchor layer 2 between the base film 1 and the pressure-sensitive adhesive layer 3.
In addition, in FIG. 1, the state which bonded the adhesive tape for semiconductor wafer processing to the pattern layer (wiring, electrode, etc.) 4 side of the semiconductor wafer on the silicon (Si) layer 5 of the semiconductor wafer is shown.

<Base film>
In the present invention, the base film is preferably a film made of a polyolefin resin or a film obtained by curing an ultraviolet curable resin.
As the polyolefin resin, ethylene / vinyl acetate copolymer (EVA), high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), and (meth) acrylic resin are preferable. (Meth) acrylic resins are preferred.
Examples of the ultraviolet curable resin include an ethylenically unsaturated group [(meth) acryloyl group, vinyl group, etc.] as a functional group that is cured by ultraviolet irradiation. Specifically, for example, a urethane acrylate oligomer is used. An example is a photopolymerizable double bond in the molecule.
In the present invention, a resin obtained by adding an ultraviolet curable resin (curing agent) urethane acrylate to a (meth) acrylic resin and curing it with ultraviolet rays is preferable.

The basic skeleton of the curing agent for the ultraviolet curable resin includes, for example, an epoxy acrylate in addition to a urethane acrylate oligomer composed of a polyol compound, an isocyanate compound, and acrylate or methacrylate. Among these, urethane acrylate is preferable.
The urethane acrylate oligomer is preferably a compound represented by the following general formula (I).

In general formula (I), R represents a hydrogen atom or a methyl group, Q represents a partial structure of a polyvalent isocyanate, and P represents a divalent group obtained from a polyol.

Here, the partial structure of the polyvalent isocyanate is a structure obtained by a reaction between a compound having two or more isocyanate groups and 2-hydroxyethyl (meth) acrylate.

In the present invention, those having 2 to 10 (meth) acryloyloxyethyloxy groups in the molecule are preferred, 2 to 6 are more preferred, and 3 to 5 are more preferred.

Urethane acrylate oligomers used for these ultraviolet curable resins are commercially available, for example, as a purple light series from Nippon Synthetic Chemical.

The (meth) acrylic resin is preferably a resin used in an adhesive described later.
The blending amount of the urethane acrylate of the ultraviolet curable resin (curing agent) is preferably 10 to 150 parts by weight, more preferably 30 to 120 parts by weight, and more preferably 50 to 100 parts by weight with respect to 100 parts by weight of the (meth) acrylic resin. Part is more preferred.

The base film can protect the semiconductor wafer from warping and also prevent warping of the semiconductor wafer while performing back surface grinding and back surface grinding of the semiconductor wafer. In particular, the base film has water resistance against water washing at the time of back surface grinding or back surface polishing of the semiconductor wafer, and also to the warping stress of the semiconductor wafer due to residual stress in an insulating film such as polyimide on the semiconductor wafer. On the other hand, it has correction power.

The thickness of the base film is not particularly limited, but is preferably 100 to 350 μm, more preferably 250 to 300 μm.
The manufacturing method of a base film is not specifically limited. In the case of a polyolefin-based resin, conventional methods such as injection, extrusion, inflation, and biaxial stretching can be used. In the case where an ultraviolet curable resin is used as a film, a method of forming a coating film with a T-die or the like as a raw material, and then crosslinking or filming with an in-line ultraviolet (UV) irradiation facility can be used.

<Adhesive layer>
In the present invention, at least one pressure-sensitive adhesive layer is provided on the base film, but in the case where sufficient adhesion between the pressure-sensitive adhesive layer and the base film cannot be ensured, a pressure-sensitive adhesive is used as the anchor layer. It can also apply | coat on top and can provide an anchor layer between a base film and an adhesive layer.

The thickness of the pressure-sensitive adhesive layer may be set as appropriate, but is 25% to 90%, preferably 30% to 90%, and 50 μm to 400 μm with respect to the height of the irregularities on the surface of the semiconductor wafer. More preferably, it is particularly preferably 250 μm to 400 μm.

In addition to this, in the present invention, the thickness of the pressure-sensitive adhesive layer is 25% or less, preferably 20% or less, of the total thickness of the pressure-sensitive adhesive tape for semiconductor wafer processing. In addition, although the minimum of the thickness of an adhesive layer is not restrict | limited in particular, 5% or more is preferable.

In addition, the stress reduction rate when compressive stress is applied in the thickness direction of the adhesive tape for processing a semiconductor wafer in the present invention is preferably 40% or more. The stress reduction rate will be described in detail later.

The pressure-sensitive adhesive and substrate film of the present invention are preferably UV curable, and more preferably UV curable.
Such a pressure-sensitive adhesive is not particularly limited as long as it is a radiation curable type, and a conventional one can be used, but is preferably a (meth) acrylic resin (hereinafter also referred to as an acrylic resin). .

(Adhesive or adhesive layer)
As the resin of the pressure-sensitive adhesive layer made of pressure-sensitive adhesive or pressure-sensitive adhesive, a (meth) acrylic resin is preferable as described above, and such an acrylic resin is a homopolymer having (meth) acrylic acid ester as a constituent component, A copolymer having (meth) acrylic acid ester as a constituent component can be exemplified. Examples of the monomer component constituting the polymer containing an acrylate ester as a constituent component include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, Linear or branched having 30 or less carbon atoms, preferably 4 to 18 carbon atoms, such as cyclohexyl, 2-ethylhexyl, octyl, isooctyl, nonyl, isononyl, decyl, isodecyl, undecyl, lauryl, tridecyl, tetradecyl, stearyl, octadecyl and dodecyl And alkyl acrylate or alkyl methacrylate having the following alkyl group. These alkyl (meth) acrylates may be used alone or in combination of two or more.

As a copolymerization component with (meth) acrylic acid ester, the following monomer components can be included. For example, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid, acids such as maleic anhydride and itaconic anhydride Anhydride monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, (meth) acrylic acid 8 Hydroxyl group-containing monomers such as hydroxyoctyl, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, styrene sulfonic acid, Sulfonic acid group-containing monomers such as sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalene sulfonic acid, Phosphoric acid group-containing monomers such as hydroxyethyl acryloyl phosphate, (meth) acrylamide, (meth) acrylic acid N-hydroxymethylamide, (meth) acrylic acid alkylaminoalkyl esters (eg, dimethylaminoethyl methacrylate, t-butylaminoethyl) Methacrylate), N-vinylpyrrolidone, acryloylmorpholine, vinyl acetate, styrene, acrylonitrile and the like. These monomer components may be used alone or in combination of two or more.

Further, the (meth) acrylic resin can contain the following polyfunctional monomer as a constituent component. For example, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, tri Methylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, dipentaerythritol hexa (meth) ) Acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, urethane (meth) acrylate, and the like. These polyfunctional monomers may be used alone or in combination of two or more.

Among the (meth) acrylic acid esters, preferably, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, and the like, and copolymers thereof are mentioned. it can. Moreover, what uses acrylic polymer and hardening | curing agents, such as what replaced said acrylic ester with methacrylic ester, for example, can be used.

(Photopolymerization initiator)
By including a photopolymerizable compound and a photopolymerization initiator in the pressure-sensitive adhesive layer, it can be cured by irradiation with radiation such as ultraviolet rays, and the pressure-sensitive adhesive force of the pressure-sensitive adhesive can be reduced.

As the photopolymerization initiator, a photopolymerization initiator described in JP2007-146104A or JP2004-186429A can be used. Isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, benzyl methyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenyl propane and the like can be used in combination.

The content of the photopolymerizable compound is preferably 50 to 150 parts by mass with respect to 100 parts by mass of the resin component, and the content of the photopolymerization initiator is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the resin component.

(Curing agent)
As a curing agent (also referred to as a crosslinking agent), a curing agent described in JP 2007-146104 A can be used. For example, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1,3-bis (N, N-diglycidylaminomethyl) toluene, 1,3-bis (N, N-diglycidylaminomethyl) ) Epoxy compounds having two or more epoxy groups in the molecule such as benzene, N, N, N, N′-tetraglycidyl-m-xylenediamine, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate , 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4′-diisocyanate, etc., an isocyanate compound having two or more isocyanate groups in the molecule, tetramethylol-tri-β-aziridini Lupropionate, trimethylol-tri-β-aziridinylpropionate, tri Chi trimethylolpropane - tri-.beta.-aziridinyl propionate, trimethylolpropane - aziridine compound having two or more aziridinyl group in the molecule, such as tri-.beta.-(2-methyl aziridine) propionate, and the like. The content of the curing agent may be adjusted according to the desired adhesive strength, and is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin component as described above. 5 parts by mass.

(Photopolymerizable compound)
Examples of the photopolymerizable compound include a photopolymerizable carbon-carbon dimer in a molecule that can be formed into a three-dimensional network by light irradiation as disclosed in, for example, JP-A-60-196956 and JP-A-60-223139. Low molecular weight compounds having at least two double bonds (ethylenic double bonds) are widely used.
Specifically, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol Diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, and the like are used.

(Polymer having a polymerizable group)
In the present invention, a resin composition comprising a polymer having a photopolymerizable carbon-carbon double bond (ethylenic double bond) in the polymer, a photopolymerization initiator, and a curing agent is used as the pressure-sensitive adhesive for the pressure-sensitive adhesive layer. The photopolymerizable adhesive used can be used. Examples of the polymer having a carbon-carbon double bond in the polymer include those having a (meth) acryloyl group, a vinyl group, or an allyl group in the side chain, and preferably the number of carbon atoms in the side chain. A monomer such as a (meth) acrylic acid ester having 4 to 12, more preferably an alkyl group having 8 carbon atoms, or a copolymerizable modifying monomer is used alone or in combination of two or more by any method. A polymerized or copolymerized (meth) acrylic polymer is preferred.
The radiation curable pressure-sensitive adhesive layer formed in this way can easily peel the pressure-sensitive adhesive tape from the adherend by irradiating radiation, preferably ultraviolet rays, to greatly reduce the adhesive strength from the initial value. Can do.

In the present invention, the thickness of the radiation curable pressure-sensitive adhesive layer is preferably 30% to 90%, more preferably 40% to 80%, with respect to a semiconductor wafer having an electrode height of 80 μm or more. .

(Anchor layer)
In order to form the pressure-sensitive adhesive layer on the base film, at least one type of pressure-sensitive adhesive may be applied or transferred to at least one surface of the base film by an arbitrary method. An intermediate layer such as an anchor layer (also referred to as a primer layer) may be provided between the pressure-sensitive adhesive layers. In the present invention, it is preferable to provide an anchor layer.
Examples of the resin forming the anchor layer include an isocyanate curable pressure sensitive adhesive and an epoxy curable pressure sensitive adhesive. Among these, an isocyanate curable pressure sensitive adhesive is preferable.

The thickness of the anchor layer is preferably 0.5 to 10 μm, more preferably 3 to 5 μm.

Further, if necessary, a synthetic resin film usually used as a separator for protecting the radiation curable pressure-sensitive adhesive layer may be attached to the pressure-sensitive adhesive layer side until it is put to practical use.
As the separator, 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.

<Deformation during compression of adhesive tape for semiconductor wafer processing>
In the pressure-sensitive adhesive tape for processing a semiconductor wafer of the present invention, the stress reduction rate after 3 minutes after applying stress at 25 ° C. and 50 N is preferably 30% or more, more preferably 35% or more, and further preferably 40% or more. The upper limit of the stress reduction rate is not particularly limited, but 80% or less is realistic.

In order to adjust the stress reduction to the preferable range as described above, specifically, adjustment is performed by adjusting the elastic modulus G ′ of the adhesive layer, adjusting the thickness of the adhesive layer, and the thickness of the base film. it can.

The stress reduction rate during compression in the thickness direction of the semiconductor wafer processing adhesive tape can be measured as follows.
Cut five pieces of adhesive tape for semiconductor wafer processing into a size of about 200mm x 200mm, laminate between base film and adhesive layer, cut the laminated one into 25mm x 55mm, and test this A piece. With the pressure-sensitive adhesive layer of the test piece facing up, the test piece was placed on a parallel plate jig for compression test provided in a tensile tester, and was bent at 25 ° C. and a speed of 1.0 mm / min from an indenter in a bending test (JIS K7171). Apply compressive stress at The stress reduction rate at the time of applying the compressive stress can be obtained by the ratio of the stress value after reaching the compressive stress 50N to the stress value when the compressive stress 50N is reached 180 seconds.

<Relationship between adhesive tape for semiconductor wafer processing and semiconductor wafer thickness>
In the present invention, the total value of the semiconductor wafer processing adhesive tape before semiconductor wafer bonding and the thickness of the semiconductor wafer excluding the surface electrode is A, and the semiconductor wafer processing adhesive tape and semiconductor wafer laminate after semiconductor wafer bonding When the total thickness of B is B, the value of A / B is preferably 0.95 or more, and particularly preferably 0.99. As for this value, the floating of the tape after pasting can be evaluated, and the value of A / B becomes small when the floating occurs frequently.
Even if it is evaluated, as this value approaches 1, the occurrence of floating does not occur.

<Application of adhesive tape for semiconductor wafer processing>
The adhesive tape for processing a semiconductor wafer of the present invention can effectively exhibit the effects of the present invention when used on a semiconductor wafer having a semiconductor wafer surface having protrusions of 80 μm or more. The height of the irregularities on the surface of the semiconductor wafer is preferably 100 μm or more, and preferably 120 μm. In addition, the upper limit which can apply the height of the unevenness | corrugation on the surface of a semiconductor wafer is 300 micrometers or less practically.

The pressure-sensitive adhesive tape for processing a semiconductor wafer of the present invention can be used for the purpose of protecting a pattern surface when backgrinding a semiconductor wafer, and has excellent adhesion even on a wafer surface with an electrode for electrical bonding. Since dust intrusion, cracking, and generation of dimples during grinding can be suppressed, it is suitable for use in grinding.

<Semiconductor wafer processing method>
The processing method of the semiconductor wafer of this invention has the process of bonding the adhesive tape for semiconductor wafer processing of this invention with respect to the semiconductor wafer which has the unevenness | corrugation of 80 micrometers or more in the surface.
The thickness of the pressure-sensitive adhesive layer included in the semiconductor wafer processing pressure-sensitive adhesive tape is 30% to 90% of the height of the irregularities on the surface of the semiconductor wafer.
As the adhesive tape for processing a semiconductor wafer of the present invention used in the method for processing a semiconductor wafer, those in the preferred range of the adhesive tape for processing a semiconductor wafer described above are applied.
preferable

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

<Example 1>
An acrylic copolymer composed of 2-ethylhexyl acrylate (78 mol%), 2-hydroxylethyl acrylate (21 mol%), and methacrylic acid (1 mol%) was prepared, and then obtained from 2-hydroxyethyl acrylate as the polymer side chain. Acrylic copolymer having a hydroxy group in the repeating unit reacted with 2- (methacryloyloxy) ethyl isocyanate and a methacryloyl group acting as a radiation-curable carbon-carbon double bond introduced into the polymer side chain Coalescence was obtained. To the obtained acrylic copolymer, trifunctional UV-curable urethane acrylate oligomer (manufactured by Nippon Synthetic Chemical Co., Ltd., (trade name) UV of UV series) with respect to 100 parts by mass of the solid content of the copolymer. -7550B 75 mass parts, 5.0 mass parts of photoinitiators ((brand name), BASF Japan make, Irgacure 184) were mix | blended, and the adhesion composition was obtained.
The following pressure-sensitive adhesive a containing a (meth) acrylic acid copolymer as a main component was applied onto a 25 μm polyethylene terephthalate (PET) separator, and dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 40 μm. A pressure-sensitive adhesive tape for processing a semiconductor wafer was produced by bonding a base film having a thickness of 270 μm obtained by curing the pressure-sensitive adhesive composition with ultraviolet rays on the surface of the adhesive layer.

The pressure-sensitive adhesive a was prepared by adjusting a (meth) acrylic copolymer having a weight average molecular weight of 800,000 consisting of butyl acrylate (70 mol%), 2-hydroxyethyl acrylate (29 mol%), and methacrylic acid (1 mol%). Then, the hydroxy group in the repeating unit obtained from 2-hydroxyethyl acrylate which is a polymer side chain is reacted with 2- (methacryloyloxy) ethyl isocyanate, and the polymer side chain is irradiated with a radiation-curable carbon-carbon dioxygen. An acrylic copolymer having a methacryloyl group acting as a double bond was obtained. For 100 parts by mass of the obtained acrylic copolymer, 2.0 parts by mass of Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), 5.0 by Nippon Ciba Geigy Co., Ltd .: Irgacure 184 (manufactured by BASF Japan Ltd.) It was obtained by blending parts by mass.

<Example 2>
The pressure-sensitive adhesive a is applied onto a 25 μm polyethylene terephthalate separator, dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 60 μm, and then adhered to the base film made of urethane acrylate having a thickness of 270 μm on the surface of the pressure-sensitive adhesive layer. By combining them, an adhesive tape for processing a semiconductor wafer was produced.

<Example 3>
The pressure-sensitive adhesive a is applied on a 25 μm polyethylene terephthalate separator, dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 60 μm, and then adhered on the surface of the pressure-sensitive adhesive layer on the base film made of urethane acrylate having a thickness of 100 μm. By combining them, an adhesive tape for processing a semiconductor wafer was produced.
<Example 4>
The pressure-sensitive adhesive a is applied onto a 25 μm polyethylene terephthalate separator, dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 60 μm, and bonded to the base film made of urethane acrylate having a thickness of 200 μm on the surface of the pressure-sensitive adhesive layer. Thus, an adhesive tape for processing a semiconductor wafer was produced.
<Example 5>
The pressure-sensitive adhesive a is applied onto a 25 μm polyethylene terephthalate separator, dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 60 μm, and then adhered to the base film made of urethane acrylate having a thickness of 350 μm on the surface of the pressure-sensitive adhesive layer. By combining them, an adhesive tape for processing a semiconductor wafer was produced.

<Comparative Example 1>
After preparing an acrylic copolymer comprising 69 parts by mass of 2-ethylhexyl acrylate, 29 parts by mass of 2-hydroxyethyl acrylate and 2 parts by mass of methacrylic acid, a repeating unit obtained from 2-hydroxyethyl acrylate as a polymer side chain An acrylic copolymer in which a hydroxy group in the polymer is reacted with 2- (methacryloyloxy) ethyl isocyanate and a methacryloyl group acting as a radiation-curable carbon-carbon double bond is introduced into the polymer side chain. Obtained. Into the obtained acrylic copolymer, 2.5 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) is blended with respect to 100 parts by mass of the solid content of the copolymer. In order to adjust the viscosity to be easy to apply, the viscosity was adjusted with ethyl acetate to obtain a pressure-sensitive adhesive composition.
The pressure-sensitive adhesive composition was coated on a 25 μm polyethylene terephthalate separator, dried, and laminated on a 165 μm thick ethylene-vinyl acetate copolymer (EVA) film. A pressure-sensitive adhesive layer having a thickness of 40 μm was provided to produce a pressure-sensitive adhesive tape for semiconductor wafer processing.

<Comparative example 2>
The pressure-sensitive adhesive a is applied onto a 25 μm polyethylene terephthalate separator and dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 60 μm. An ethylene-vinyl acetate copolymer having a thickness of 165 μm and a vinyl acetate content of 10% by mass (EVA) An adhesive tape for processing a semiconductor wafer was produced by laminating on the film.

<Comparative Example 3>
After preparing an acrylic copolymer consisting of 69 parts by mass of 2-ethylhexyl acrylate, 29 parts by mass of 2-hydroxyethyl acrylate and 2 parts by mass of methacrylic acid, a repeating unit obtained from 2-hydroxyethyl acrylate as a polymer side chain Acrylic copolymer in which a methacryloyl group acting as a radiation curable carbon-carbon double bond is introduced into the polymer side chain by reacting with a hydroxy group therein and 2- (methacryloyloxy) ethyl isocyanate is obtained. It was. Into the obtained acrylic copolymer, 2.5 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) is blended with respect to 100 parts by mass of the solid content of the copolymer. In order to adjust the viscosity to be easy to apply, the viscosity was adjusted with ethyl acetate to obtain a pressure-sensitive adhesive composition.
The pressure-sensitive adhesive composition was applied onto a 25 μm polyethylene terephthalate separator, dried, and a polyethylene terephthalate (PET) film having a Young's modulus of 8.0 × 10 ⁹ Pa (25 ° C.) and a thickness of 100 μm (Toyobo Co., Ltd. ( (Product name) Cosmo Shine A4100) was laminated together, and a pressure-sensitive adhesive layer having a thickness of 40 μm was provided on this laminated base film to produce a pressure-sensitive adhesive tape for semiconductor wafer processing.

[Characteristic evaluation test]
A characteristic evaluation test was performed on the adhesive tapes for processing semiconductor wafers of Examples 1 to 5 and Comparative Examples 1 to 3 as follows.

(I) Measurement of compressive deformation stress Five adhesive tapes for processing semiconductor wafers of Examples and Comparative Examples were cut into a size of about 200 mm × 200 mm and laminated between a base film and an adhesive layer. The laminated one was cut into 25 mm × 55 mm and used as a test piece. With the pressure-sensitive adhesive layer of the test piece facing up, the test piece was placed on a parallel plate jig for compression test provided in a tensile tester, and was bent at 25 ° C. and a speed of 1.0 mm / min from an indenter in a bending test (JIS K7171). A compressive stress was applied. The portion where the indenter contacted the sample before applying the stress was taken as the zero point, and the amount of displacement when a 50 N compressive stress was applied was taken as the measured value.
The stress reduction rate (referred to as stress reduction rate in the table) when compressive stress was applied was calculated from the ratio of the stress value 180 seconds after reaching the compressive stress 50N to the stress value when the compressive stress 50N was reached.

(Adhesive tape for semiconductor wafer processing)
The bonding property of the produced adhesive tape for semiconductor wafer processing was determined by using an automatic laminator (DR-8500III manufactured by Nitto Denko Corporation), setting the pressure at both ends of the bonding roller to 0.25 MPa, and an 8-inch bare silicon wafer and Bonding and cutting were performed on a silicon wafer with a 120 μm ball bump (bump pitch 250 μm).

(Ii) Adhesion test of semiconductor wafer with electrodes For those bonded to a silicon wafer with an electrode of 120 μm in height, the tape of the adhesive tape for processing semiconductor wafers was lifted after being left at 25 ° C. for 24 hours immediately after bonding. Whether it occurred or not was evaluated and evaluated according to the following criteria.
Here, the occurrence of tape floating is defined as B, where the total thickness of the semiconductor wafer processing adhesive tape and semiconductor wafer laminate after bonding the semiconductor wafer is B, and the semiconductor wafer processing adhesive tape and surface electrode before semiconductor wafer bonding The value of A / B where A is the total value with the semiconductor wafer thickness excluding, was also evaluated.

Evaluation criteria A: No floating occurred on the surface of the semiconductor wafer (A / B = 0.99 or more)
○: Less than 30% of the surface of the semiconductor wafer floated (A / B = 0.95 or more and less than 0.99)
Δ: 30% or more and less than 50% of the surface of the semiconductor wafer floated (A / B = 0.80 or more and less than 0.95)
X: 50% or more of the surface of the semiconductor wafer was lifted (A / B = 0.80)

Before bonding, measure the thickness of the adhesive tape for semiconductor wafer processing and the thickness of the semiconductor wafer (excluding bumps), measure the total thickness after bonding, and calculate the ratio of the thickness of the adhesive layer. did.

(Iii) In-apparatus transfer test In-apparatus transfer after semiconductor wafer backside grinding uses a disco-made full-auto grinder DGP8760 + wafer mounter DFM2700 to check whether an adsorption error occurs or automatic transfer to the mounter is possible. did. The case where no adsorption error occurred was evaluated as ◯, and the case where an adsorption error occurred during transportation was evaluated as x.

(Iv) Thin film grindability A silicon wafer with a 120 μm height electrode was ground to a thickness of 150 μm, and cracks were evaluated according to the following evaluation criteria.

Evaluation criteria ◎: No cracks were found on the ground semiconductor wafer ○: One crack was confirmed at the wafer edge △: Two to three cracks were confirmed at the wafer edge ×: Four or more cracks were observed at the wafer edge It was confirmed

Also, dimples (small concave portions) were evaluated according to the following criteria.

Evaluation criteria ○: No dimple on the backside of the wafer after grinding ×: Dimple is confirmed on the backside of the wafer after grinding

(V) Evaluation of dust intrusion (seapage) A laminator (trade name) is formed on the groove-formed surface of an 8-inch diameter silicon wafer in which grooves having a width of 50 μm and a depth of 30 μm are formed over the entire surface at intervals of 5 mm. : DR-8500II, manufactured by Nitto Seiki Co., Ltd.), an adhesive tape for semiconductor wafer processing was bonded. The semiconductor wafer to which the adhesive tape is bonded is back-ground to a thickness of 50 μm with a grinder (trade name: DGP8760, manufactured by DISCO Corporation), and the cutting water from the outer periphery of the adhesive wafer for semiconductor wafer processing after grinding to the grooves The invasion of was investigated.
This result was evaluated according to the following criteria.

Evaluation criteria ○: The above investigation was repeated 5 times, and no intrusion of cutting water was observed at all 5 times. Δ: The above investigation was repeated 5 times and the intrusion of cutting water was observed at least once. ×: The above investigation was repeated 5 times and cutting water intrusion was observed 5 times.

These results are summarized in Tables 1 and 2 below.

As shown in Tables 1 and 2, in Comparative Examples 1 to 3, the thickness of the pressure-sensitive adhesive layer exceeded 25% of the whole tape, and in the semiconductor wafer grinding process having an electrode of 80 μm or more, the cracks were conspicuous. .
On the other hand, in Examples 1 to 5, since the thickness of the pressure-sensitive adhesive layer was 25% or less of the entire tape, good adhesion and grindability were exhibited.

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. 2014-061011 filed in Japan on March 24, 2014, which is incorporated herein by reference. Capture as part.

DESCRIPTION OF SYMBOLS 10 Adhesive tape for semiconductor wafer processing 1 Base film 2 Anchor layer 3 Adhesive layer 4 Pattern layer (wiring, electrode, etc.) of semiconductor wafer
5 Silicon layer of semiconductor wafer

Claims

It is an adhesive tape for processing a semiconductor wafer used in a step of bonding to a semiconductor wafer having an unevenness of 80 μm or higher on the surface and grinding the back surface of the semiconductor wafer,
Having a pressure-sensitive adhesive layer on the base film, the thickness of the pressure-sensitive adhesive layer being 25% to 90% of the uneven height on the surface of the semiconductor wafer; and
The pressure-sensitive adhesive layer has a thickness of 25% or less of the entire thickness of the pressure-sensitive adhesive tape for semiconductor wafer processing.
When the compressive stress is applied in the thickness direction of the adhesive tape for processing a semiconductor wafer, the amount of displacement when a compressive stress of 50 N is applied is measured, and from the arrival of the compressive stress 50 N to the stress value when the compressive stress 50 N is reached The pressure-sensitive adhesive tape for processing a semiconductor wafer according to claim 1, wherein the pressure-sensitive adhesive tape is 40% or more calculated from a ratio of stress values after 180 seconds.
The unevenness on the surface of the semiconductor wafer is an electrode, and A is the total value of the semiconductor wafer processing adhesive tape before the semiconductor wafer bonding and the semiconductor wafer thickness excluding the surface electrode, and the semiconductor wafer processing adhesive tape after the semiconductor wafer bonding. 3. The adhesive tape for processing a semiconductor wafer according to claim 1, wherein A / B is 0.95 or more when the total thickness of the laminate of the semiconductor wafers is B. 4.
The adhesive tape for processing a semiconductor wafer according to any one of claims 1 to 3, wherein the base film is made of an ultraviolet curable resin.
A method for processing a semiconductor wafer using an adhesive tape for processing a semiconductor wafer that is bonded to a semiconductor wafer having irregularities with a height of 80 μm or more on the surface,
The semiconductor wafer processing pressure-sensitive adhesive tape has a pressure-sensitive adhesive layer on a base film, and the thickness of the pressure-sensitive adhesive layer is 25% or less of the total thickness of the semiconductor wafer processing pressure-sensitive adhesive tape,
The pressure-sensitive adhesive layer has a thickness of 25% to 90% of the uneven height of the semiconductor wafer surface,
A method for processing a semiconductor wafer, comprising a step of bonding the semiconductor wafer processing adhesive tape to the semiconductor wafer.