JPH04192542A - Adhesive sheet for bonding wafer - Google Patents

Abstract

PURPOSE:To make it possible to inhibit the deterioration in adhesion properties and restore said properties by proper heating by comprising a soft vinyl chloride layer as one layer which constitutes a base material and demodified nylon, urethane photosensitive rubber or resin, ethylene vinyl alcohol copolymer or polyvinylidene chloride as other layers which constitute said base material. CONSTITUTION:A base material 2 comprises at least two component layers. One layer which constitutes the base material is soft vinyl chloride while the other layer which constitutes the base material is faced with an adhesive layer. Moreover, the other layer which constitutes the base material comprises demodified nylon, photosensitive rubber or resin, ethylene vinyl alcohol copolymer or polyvinylidene chloride. Provision of such a specific middle layer makes it possible to inhibit effectively a soft vinyl chloride layer from transferring to an adhesive layer or plasticizer or a stabilizer and restore by proper heating and prevent the generation of elongation of deflection.

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet for pasting wafers, and more particularly, it easily stretches during the expansion process, and substances that degrade the physical properties of the pressure-sensitive adhesive migrate into the pressure-sensitive adhesive layer. The present invention relates to a pressure-sensitive adhesive sheet for pasting wafers which can suppress the above-mentioned problems and can be restored by proper heating after being stretched.

Technical Background of the Invention Semiconductor wafers of silicon, gallium arsenide, and the like are manufactured in a large diameter state, and after the wafer is diced into small element pieces, it is transferred to the next process, a mounting process. At this time, the semiconductor wafer is previously attached to an adhesive sheet and subjected to the following steps: dicing, cleaning, drying, expanding, picking up, and mounting.

The adhesive sheet used in such a semiconductor wafer dicing process has conventionally been one in which an acrylic adhesive layer is provided on a base material surface made of polyvinyl chloride film. However, with such an adhesive sheet having an acrylic adhesive layer, there is a problem that when each chip of a diced semiconductor wafer is picked up, the adhesive remains on the chip surface and the chips are contaminated. Ta.

In order to solve the second problem, conventional methods have been proposed in which the amount of adhesive is reduced by partially applying the adhesive to the substrate surface instead of applying it to the entire surface. According to this method, the amount of adhesive relative to the total number of chips is reduced and contamination by adhesive on the chip surface can be reduced to some extent, and the adhesive force between the wafer chips and the adhesive sheet is reduced, so the dicing process cleaning followed by
A new problem arises in that the wafer chip detaches from the adhesive sheet during the drying and expanding steps.

Adhesive sheets used in processes ranging from the dicing process to the pick-up process of semiconductor wafers include:
It is desired that the adhesive has sufficient adhesive strength to the wafer chip during the dicing process to the expanding process, and has enough adhesive strength to prevent adhesive from adhering to the wafer chip during pickup.

A pressure-sensitive adhesive sheet such as No. 2 is published in Japanese Patent Application Laid-open No. 60-196.
No. 956 and Japanese Unexamined Patent Publication No. 60-223゜139 disclose a low molecular weight material having at least two photopolymerizable carbon-carbon double bonds in the molecule, which can be formed into a three-dimensional network by light irradiation on the substrate surface. An adhesive sheet coated with an adhesive made of a compound has been proposed. According to the publication, low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in the molecule include trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. , dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, or 1,4-butylene glycol diacrylate, 1,6-hexaneshiol diacrylate, polyethylene glycol diacrylate, and commercially available oligoester acrylates. .

An adhesive layer made of a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule is coated on a base material made of polyvinyl chloride (PVC) film as exemplified above. The present inventors have discovered that the pressure-sensitive adhesive sheet has the following problems.

That is, when a pressure-sensitive adhesive sheet for wafer attachment is used after being stored for a long period of time, the plasticizer or pressure-sensitive adhesive may have already migrated from the polyvinyl chloride base material into the pressure-sensitive adhesive, and the pressure-sensitive adhesive may have softened. Therefore, when such an adhesive sheet is used, there is a problem in that even if an attempt is made to pick up chips from the adhesive sheet after a dicing process, a UV irradiation process, etc., the chips cannot be picked up reliably.

In addition, as the adhesive softens as described above, the adhesive sheet appears to be in a softened state, and the adhesive sheet slips and loosens from the holding part of the flat frame, and the adhesive sheet gradually comes off from the flat frame and is used in the next process. There is a problem that die bonding cannot be done.

In order to prevent the plasticizer or adhesive from migrating from the polyvinyl chloride base material, for example, Japanese Patent Publication No. 1-56
Publication No. 111 discloses a pressure-sensitive adhesive sheet in which a resin layer selected from polyethylene, polypropylene, polyalkylene terephthalate, and modified alkyd resin is provided as an intermediate layer between a polyvinyl chloride base material and an adhesive layer. There is.

By providing a resin layer selected from polyethylene, polypropylene, polyalkylene terephthalate, and modified alkyd resin as an intermediate layer as described above, migration of plasticizer from the polyvinyl chloride base material into the adhesive can be effectively suppressed. . However, it is not always possible to sufficiently suppress the migration of various anti-aging agents. Furthermore, the present inventors have discovered that the above-mentioned intermediate layer has poor elongation properties during the expansion process and poor restorability after that, resulting in sagging of the base material.

The inventors of the present invention have made extensive studies to solve the problems associated with the conventional technology, and have found that the above problems can be solved by using a laminated film having a specific configuration as the base sheet of the adhesive sheet. The present invention was completed by discovering that the problems could be solved at once.

Purpose of the Invention The present invention is intended to solve the problems associated with the prior art as described above. The purpose of the present invention is to provide a pressure-sensitive adhesive sheet for attaching wafers that can suppress the transition to wafers and can be restored by appropriate heating after stretching.

Summary of the Invention The adhesive sheet for wafer adhesion according to the present invention has at least two
In a pressure-sensitive adhesive sheet for wafer adhesion, in which a pressure-sensitive adhesive layer is coated on a base material having more than one constituent layer, one layer constituting the base material is made of soft vinyl chloride, and the other layer constituting the base material is made of soft vinyl chloride. The adhesive layer or other layers in contact with the adhesive layer and constituting the base material are characterized by being made of modified nylon, urethanized photosensitive rubber or resin, ethylene/vinyl alcohol copolymer, or polyvinylidene chloride. .

Detailed Description of the Invention The adhesive sheet 1 according to the present invention, as shown in its cross-sectional view or FIG. In order to protect the adhesive layer 3 before use, it is preferable to temporarily attach a releasable sheet 4 to the upper surface of the adhesive 3 as shown in FIG. 2.

The pressure-sensitive adhesive sheet according to the present invention can take any shape such as a tape shape or a label shape.

In the present invention, the base material 2 has at least two constituent layers,
Either one layer constituting the base material is made of soft vinyl chloride, and another layer constituting the base material, or another layer constituting the base material that is in contact with the adhesive layer is modified nylon, urethane photosensitive It consists of rubber or resin, ethylene/vinyl alcohol copolymer, or polyvinylidene chloride.

The soft vinyl chloride used in the present invention includes phthalate esters such as dibutyl phthalate, dioctyl phthalate, dinonyl phthalate, and diisodecyl phthalate, other polyester plasticizers, epoxy plasticizers, and trimellitic plasticizers. Vinyl chloride copolymers such as urethane-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, vinyl acetate-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, etc. Mixtures or mixtures with other resins and elastomers are also used. Of course, the above-mentioned copolymers include graft copolymers, and it goes without saying that the above-mentioned mixtures also include so-called alloys. moreover,
The above-mentioned epoxy plasticizer may be an epoxidized vegetable oil such as epoxidized soybean oil or epoxidized linseed oil as a secondary plasticizer and stabilizer. Other known stabilizers, lubricants, and processing aids can be used with the soft vinyl chloride.

At least one of the layers constituting the base material of the adhesive sheet for wafer adhesion according to the present invention is made of soft vinyl chloride as described above.

The thickness of such a layer made of soft vinyl chloride is not particularly limited, and is usually 30 μm to 300 μm, preferably 50 μm to 150 μm.

In the adhesive sheet for attaching wafers according to the present invention, a certain intermediate layer is provided between the layer made of soft vinyl chloride as described above and the adhesive layer described below, and the layer made of soft vinyl chloride and the adhesive layer are provided. It is not in direct contact with the agent layer.

In the present invention, a layer made of modified nylon, a layer made of urethanized photosensitive rubber or resin, a layer made of ethylene/vinyl alcohol copolymer, or a layer made of polyvinylidene chloride is used as the intermediate layer in the present invention. By providing such a special intermediate layer, it is possible to effectively suppress the migration of plasticizers and the above-mentioned stabilizers from the layer made of soft vinyl chloride to the adhesive layer, and it is also possible to prevent It can also be restored with appropriate heating, preventing the sheet from elongating or bending.

The above modified nylon, urethanized photosensitive rubber or resin,
Various ethylene/vinyl alcohol copolymers or polyvinylidene chloride have been known in the past. A resin that does not dissolve or swell in the agent, etc., and that can be easily restored by appropriate heating even after elongation is used.

When these resins are laminated onto soft vinyl chloride, commonly known methods such as coextrusion, extrusion lamination, thermal lamination, dry lamination, solution casting, etc. are used.

The above-mentioned modified nylon includes -NHCO in the nylon molecule.
The hydrogen of >NH in the - bond may be replaced with an N-methylol group or N-alkoxymethyl group to reduce the hydrogen bond strength.

Further, as the urethane photosensitive rubber or resin, a polymer is used in which the end of the rubber main chain is converted into urethane and a radically polymerizable photosensitive group such as an acrylic group, a methacryl group, or a vinyl group is added. Specifically, the number of functional groups is 2 or more, the elongation rate of the film is 50% or more, and the breaking strength is 3.
00 kg/cf [r or less is good and the molecular weight is 300
It may be arbitrarily selected within the range of 0 to 20,000.

The above-mentioned ethylene/vinyl alcohol copolymer is a film having an ethylene copolymerization ratio of 25 to 55 mol%, and in consideration of practicality, a non-stretched type is used.

The above modified nylon, urethanized photosensitive rubber or resin,
The thickness of the layer made of ethylene/vinyl alcohol copolymer or polyvinylidene chloride is not particularly limited, but
Usually 3 μm to 50 μm, preferably 5 μm to 30 μm
It is μm.

and the thickness of the base material having at least a layer made of the above-mentioned modified nylon, urethanized photosensitive rubber or resin, ethylene/vinyl alcohol copolymer, or polyvinylidene chloride, and a layer made of the above-mentioned soft vinyl chloride as a constituent layer. is not particularly limited, and is usually 30 μm to 30 μm.
0 μm, preferably 50 μm to 150 μm.

By providing an adhesive layer on the base material 2 having the above-mentioned structure, an intermediate layer made of the resin as described above is formed between the layer made of soft vinyl chloride containing a plasticizer etc. and the adhesive layer. A pressure-sensitive adhesive sheet for wafer adhesion is obtained. The adhesive sheet for attaching wafers having such a structure can prevent the plasticizer contained in the soft vinyl chloride from migrating to the adhesive layer, do not soften the adhesive layer, and can maintain the adhesive properties. The adhesive sheet does not bend due to sheet elongation, exhibits sufficient extensibility during expansion, and can reliably pick up wafer chips, and can be heated appropriately even after expansion. It is easier to restore.

In addition, in the present invention, another layer may be provided between the layer made of soft vinyl chloride constituting the base material 2 and the intermediate layer made of the resin. Other layers that may be provided between the layer made of soft vinyl chloride and the intermediate layer include, for example, an adhesive layer for dry lamination that adheres the layer made of soft vinyl chloride and the intermediate layer,
Examples include adhesive resins such as adhesive polyethylene, adhesive polypropylene, adhesive ethylene vinyl acetate copolymer, ethylene-acrylic acid (ester) copolymer, and ionomer.

An adhesive layer 3 is provided on the base material 2 as described above. As the adhesive constituting the adhesive layer 3, conventionally known adhesives or widely used ones can be used, but acrylic polymers are preferable, and specifically, homopolymers containing acrylic acid ester as the main constituent monomer unit are preferred. Copolymers selected from acrylic polymers and copolymers with other functional monomers and mixtures of these polymers are used. For example, acrylic acid esters include ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, and the above methacrylic acids can be used as acrylic acid. It can also be preferably used in place of it.

Furthermore, in order to improve compatibility with oligomers described later, monomers such as acrylic acid, methacrylic acid, acrylonitrile, and vinyl acetate may be copolymerized. The molecular weight of the acrylic polymer obtained by polymerizing these monomers is from 2.0x105 to 10.0xIO5, preferably from 4.0xIO5 to 8.0xIO5.

By including a radiation-polymerizable compound in the adhesive layer as described above, the adhesive force can be reduced by irradiating the adhesive layer with radiation after cutting and separating the wafer. Such radiation-polymerizable compounds include compounds that can be formed into a three-dimensional network by light irradiation, such as those disclosed in JP-A-60-196,956 and JP-A-60-223,139. Low molecular weight compounds having at least two or more photopolymerizable carbon-carbon double bonds are widely used, and specifically, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, Dipentaerythritol monohydroxy pentaacrylate, dipentaerythritol hexaacrylate or 1.4-butylene gelicol diacrylate, 1.6-
Hexanediol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, etc. are used.

Further, as the radiation polymerizable compound, in addition to the above-mentioned acrylate compounds, urethane acrylate oligomers can also be used. The urethane acrylate oligomer is composed of a polyol compound such as a polyester type or polyether type, and a polyvalent isocyanate compound such as 2,4-tolylene diisocyanate, 2,6-
Tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, etc., are added to the terminal isocyanate urethane prepolymer obtained by reacting acrylate or methacrylate that grows hydroxyl groups, such as 2 - It is obtained by reacting hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, etc. This urethane acrylate oligomer is a radiation polymerizable compound having at least one carbon-carbon double bond.

As a urethane acrylate oligomer like 2,
In particular, the molecular weight is 3000 to 30000, preferably 3000
~10,000, more preferably 4,000 to 8,000, even when the semiconductor wafer surface is rough,
This is preferable because the adhesive does not adhere to the chip surface when the wafer chip is picked up. In addition, when a urethane acrylate oligomer is used as a radiation polymerizable compound, it has at least two photopolymerizable carbon-carbon double bonds in the molecule as disclosed in JP-A-60-196,956. Compared to the case where a low molecular weight compound is used, an extremely superior pressure-sensitive adhesive sheet can be obtained. That is, the adhesive strength of the adhesive sheet before irradiation with radiation is sufficiently large, and the adhesive strength decreases sufficiently after irradiation with radiation, so that no adhesive remains on the chip surface when the wafer chip is picked up.

The blending ratio of the acrylic adhesive and the urethane acrylate oligomer in the adhesive in the present invention is such that the urethane acrylate oligomer is used in an amount of 50 to 900 parts by weight per 100 parts by weight of the acrylic adhesive. preferable. In this case, the resulting pressure-sensitive adhesive sheet has a high initial adhesive strength, and the adhesive strength significantly decreases after radiation irradiation, making it possible to easily pick up wafer chips from the pressure-sensitive adhesive sheet.

Further, if necessary, the adhesive layer 3 may contain, in addition to the above-mentioned adhesive and radiation polymerizable compound, a compound that is colored by radiation irradiation. By including a compound in the adhesive 3 that will be colored by such radiation irradiation, the adhesive sheet will be colored after being irradiated with radiation, so that it can be detected by the optical sensor when detecting the honeycomb. Accuracy is increased, and malfunctions do not occur when picking up wafer chips. In addition, it is possible to immediately determine by visual inspection whether or not the adhesive sheet has been irradiated with radiation.

A compound that is colored by radiation irradiation is a compound that is colorless or light-colored before radiation irradiation, or a compound that becomes colored by radiation irradiation, and a preferred specific example of this compound is a leuco dye. As the leuco dye, commonly used triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based ones are preferably used. Specifically, 3-[N-(p-)lylamino')]-7-anirithufluorane, 3-[N-(p-
-)lyl) -N-methylamino]-7-anilitofluorane, 3-[N-(p-tolyl)-N-ethylamino 1-7-anilinofluorane, 3-diethylamino-6
-Methyl-7-anilinofluorane, crystal violet lactone, 4,4', 4"-trisdimethylaminotriphenylmethanol, 4,4°.

Examples include 4-trisdimethylaminotriphenylmethane.

Color developers preferably used with these leuco dyes include electron acceptors such as conventionally used initial polymers of phenol-formalin resin, aromatic carboxylic acid derivatives, and activated clay. In some cases, various known coloring agents may be used in combination.

Such a compound that is colored by radiation irradiation may be dissolved in an organic solvent or the like and then incorporated into the adhesive layer, or may be made into a fine powder and included in the adhesive layer. This compound is desirably used in the adhesive layer in an amount of 0.01 to 10% by weight, preferably 0.5 to 5% by weight. If the compound is used in an amount exceeding 10% by weight, the radiation irradiated to the pressure-sensitive adhesive sheet will be absorbed too much by the compound, resulting in insufficient curing of the pressure-sensitive adhesive layer. Or 0. If the amount of O1 is less than 96% by weight, the pressure-sensitive adhesive sheet may not be sufficiently colored during radiation irradiation, and malfunctions may easily occur when picking up the Ueno chip.

In some cases, the adhesive layer 3 may contain a light-scattering inorganic compound powder in addition to the above-mentioned adhesive and radiation polymerizable compound.

By including such a light-scattering inorganic compound powder in the adhesive layer 3, even if the surface of an adherend such as a semiconductor wafer turns gray or black for some reason, radiation such as ultraviolet rays can be prevented from being transmitted to the adhesive sheet. When irradiated, the adhesive strength of gray or blackened areas is sufficiently reduced, so that the adhesive does not stick to the wafer chip surface when the wafer chip is picked up, and the adhesive strength is sufficiently reduced before irradiation. The effect is that it has strong adhesive strength.

This light-scattering inorganic compound is a compound that can diffusely reflect radiation such as ultraviolet (UV) or electron beam (EB) when irradiated with it, and
Specific examples include silica powder, alumina powder, silica alumina powder, and mica powder. The light-scattering inorganic compound is preferably one that almost completely reflects the radiation as described above, but it is of course possible to use one that absorbs the radiation to some extent.

It is preferable that the light-scattering inorganic compound is in the form of a powder, and the particle size thereof is preferably about 1 to 100 μm, preferably about 1 to 20 μm. This light-scattering inorganic compound is desirably used in the adhesive layer in an amount of 0.1-10% by weight, preferably 1-4% by weight. If the compound is used in an amount exceeding 10% by weight in the adhesive layer, the adhesive strength of the adhesive layer may be reduced, while if it is less than 0.1% by weight, the surface of the semiconductor wafer may become gray. If the wafer becomes black or black, even if the area is irradiated with radiation, the adhesive force may not be sufficiently reduced and some adhesive may remain on the wafer surface when it is picked up.

The adhesive sheet obtained by adding a light-scattering inorganic compound powder to the adhesive layer can be used even when the surface of a semiconductor wafer has become gray or black for some reason. It is thought that the reason why the adhesion strength of this part is sufficiently reduced when the part is irradiated with radiation is considered to be as follows. That is, the adhesive sheet 1 according to the present invention has an adhesive layer 3, or when this adhesive layer 3 is irradiated with radiation,
The radiation-polymerizable compound contained in the adhesive layer 3 will harden and its adhesive strength will decrease.

However, for some reason, gray or black areas may appear on the surface of a semiconductor wafer. In such a case, if the adhesive layer 3 is irradiated with radiation, the radiation will pass through the adhesive layer 3 and reach the wafer surface, but if there is a gray or blackened area on the wafer surface, the radiation will not reach this area. It is absorbed and no longer reflects. For this reason, the radiation that should originally be used to harden the adhesive layer 3 is absorbed by the gray or blackened areas, resulting in insufficient curing of the adhesive layer 3 and the adhesive strength not decreasing sufficiently. become. Therefore, it is thought that some adhesive may adhere to the chip surface when the wafer chip is picked up.

However, when a light-scattering inorganic compound powder is added to the adhesive layer 3, the irradiated radiation collides with the compound and changes its direction before reaching the wafer surface. For this reason, even if there is a gray or black area on the wafer chip surface, the diffusely reflected radiation will penetrate into the area above this area, and the gray or black area will also be fully absorbed. harden. Therefore, by adding light-scattering inorganic compound powder to the adhesive layer, even if there is a gray or black area on the semiconductor wafer surface for some reason, the adhesive layer will not harden in this area. I wonder if it will be enough (and hopefully, there will be no adhesive attached to the chip surface when picking up the wafer chip.

Further, in the present invention, a thermally expandable compound may be added to the adhesive layer 3 in addition to the above-mentioned adhesive and radiation polymerizable compound.

Furthermore, according to the present invention, abrasive grains may be dispersed in the base material. The abrasive grains have a particle size of 0.5 to 100 μm, preferably 1 to 50 μm, and a Mohs hardness of 6 to 10, preferably 7 to 1O. Specifically, green carborundum, artificial corundum, optical emery, white alundum, boron carbide, chromium oxide (■), cerium oxide, diamond powder, etc. are used. Preferably, such abrasive grains are colorless or white.

Such abrasive grains are present in the substrate 2 in an amount of 0.5 to 70% by weight, preferably 5 to 50% by weight. Such abrasive grains are particularly preferably used when the cutting blade is used to a depth that cuts not only into the wafer but also into the base material 2.

By incorporating the above abrasive grains into the base material, even if the cutting blade cuts into the base material and adhesive adheres to the cutting blade, the abrasive grain's abrasive effect will easily remove the clogging. I can do it.

Furthermore, in the present invention, an expanding agent may be added to the adhesive layer 3 in addition to the adhesive.

Specifically, the following compounds are used as such an expanding agent.

(a) higher fatty acids or their derivative stearic acid,
Lauric acid, ricinoleic acid, naphthenic acid, 2-ethylhexoic acid, oleic acid, linoleic acid, myristic acid,
Esters of the above acids such as palmitic acid, isostearic acid, hydroxystearic acid, behenic acid.

Metal salts of the above acids such as Li, Mg, Ca, Sr,
Ba, Cd, Zn, Pb, Sn, Na salt, or a composite metal salt containing two or more of the above metals.

(b) A compound having a Si or siloxane structure.

silicone oil etc.

(c) Compounds containing fluorine.

(d) Epoxy compound.

Methyl epoxy stearate, butyl epoxy stearate, epoxidized linseed oil, butyl fatty acid, epoxidized tetrahydronaphthalate, bisphenol A diglycidyl ether, epoxidized butadiene.

(e) Polyol compounds or derivatives thereof such as glycerin, diglycerin, sorbitol, mannitol, xylitol, pentaerythritol, dipentaerythritol, trimethylolpropane, polyethylene glycol, polyvinyl alcohol, etc.

Nitrogen-containing or sulfur-containing or metal complexes of the above compounds.

(f) β-diketo compounds or derivatives thereof acetoacetate, dehydroacetic acid, acetylacetone, benzoylacetone, trifluoroacetylacetone, stearoylbenzoylmethane, dibenzylmethane.

Metal complexes of the above compounds.

(g) Phosphites Triphenylphosphine, diphenylphosphine, phenyl acid, hydrogenated bisphenol A phosphite polymer, ＼ R (wherein R is C 2° + 1) such expanding agents are used as adhesives. When incorporated into the agent layer 3, sufficient spacing can be provided between the chips provided on the base sheet, so that adjacent chips do not come into contact or misalignment of chips occurs. No malfunctions occur when picking up chips. In particular, when a radiation-polymerizable compound is present in the adhesive layer, a remarkable effect is observed.

The above-mentioned expanding agent is desirably used in the adhesive layer 3 in an amount of 0.1-10% by weight, preferably 0.5-6% by weight.

Further, by mixing an isocyanate curing agent into the above-mentioned pressure-sensitive adhesive, the initial adhesive strength can be set to an arbitrary value. Examples of such curing agents include polyvalent isocyanate compounds, such as 2,4-)lylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and diphenylmethane. -4,4“
-diisocyanate, diphenylmethane-2,4-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4-
Diisocyanate, dicyclohexylmethane-2,4'
- Diisocyanate, lysine isocyanate, etc. are used.

Furthermore, in the above adhesive, in the case of UV irradiation, UV
By incorporating an initiator, the polymerization curing time due to UV irradiation and the amount of UV irradiation can be reduced.

Specifically, such UV initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, abhis isobutyronitrile, dibenzyl, diacetyl, β- One example is chlor-anthraquinone.

The method of using the adhesive sheet according to the present invention will be explained below.

When a releasable sheet 4 is provided on the top surface of the adhesive sheet l according to the present invention, the sheet 4 is removed, and then the adhesive sheet l is placed with the adhesive layer 3 facing upward, and a third As shown in the figure, a semiconductor wafer A to be diced is adhered to the upper surface of this adhesive layer 3. In this adhered state, wafer A is subjected to various processes such as dicing, cleaning, drying, and expanding. At this time, since the wafer chips are sufficiently adhered and held to the adhesive sheet by the adhesive layer 3, the wafer chips will not fall off during the above steps.

Next, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined base, or at this time, as shown in FIG. (EB
) The pressure-sensitive adhesive layer 3 of the pressure-sensitive adhesive sheet 1 is irradiated with ionizing radiation B such as ionizing radiation B to polymerize and harden the radiation-polymerizable compound contained in the pressure-sensitive adhesive layer 3. When the radiation-polymerizable compound is polymerized and cured by irradiating the adhesive layer 3 with radiation in this manner, the adhesive strength of the adhesive is greatly reduced, and only a small amount of adhesive strength remains.

The adhesive sheet 1 is preferably irradiated with radiation from the side of the base material 2 on which the adhesive layer 3 is not provided. Therefore, as mentioned above, when using UV radiation as the radiation, the base material 2 must be light-transmissive, but when using E B as the radiation, the base material 2 is not necessarily light-transmissive. There's no need.

In this way, wafer chips A + , A t...
・Irradiate the adhesive layer 3 in the area provided with radiation,
After reducing the adhesive force of the adhesive layer 3, the adhesive sheet 1 is transferred to a pickup station (not shown),
As shown in FIG. 5, a chip A to be picked up from the bottom surface of the base material 2 by the needle rod 5 according to a conventional method.
Push up 1... and this chip A1...
For example, pick up with air tweezers 6,
This is mounted on a predetermined base. When wafer chips A+, A2, etc. are picked up in this way, they can be easily picked up without any adhesive attached to the wafer chip surface, and the wafer chips can be picked up in a good manner without contamination. You will get quality chips. Note that radiation irradiation can also be performed at a pickup station.

It is not necessarily necessary to irradiate the entire surface of the wafer A to which the wafer A is attached at once, and the irradiation may be performed in parts several times. For example, the wafer chips Al1A2, etc. After irradiating each wafer chip with a radiation irradiation tube that irradiates only the corresponding back surface to reduce the adhesive force of only the adhesive on that part, the wafer chips A+, A are removed using the push-up needle rod 5. *...
You can also pick up items in sequence by pushing them up. FIG. 6 shows a modification of the above-mentioned radiation irradiation method. In this case, the push-up needle rod 5 is made hollow, and a radiation source 7 is provided in the hollow part to perform radiation irradiation and pickup. It is possible to do both at the same time, and in this way the device can be simplified and at the same time the pick-up operation time can be shortened.

As described above in detail, the base material of the adhesive sheet for wafer attachment according to the present invention includes a layer made of soft vinyl chloride, modified nylon, urethanized photosensitive rubber or resin, ethylene, etc.
Since it is laminated with a layer made of vinyl alcohol copolymer or polyvinylidene chloride, it can be easily stretched during the expansion process, and it is possible to prevent substances that would deteriorate adhesive properties from migrating into the adhesive layer. It becomes possible to provide a pressure-sensitive adhesive sheet for wafer attachment that can be restored by moderate heating after stretching.

[Examples] The present invention will be explained below using Examples, but the present invention is not limited to these Examples.

Example 1 100 parts by weight of an acrylic adhesive (a copolymer of rope tyl acrylate and acrylic acid), 100 parts by weight of a urethane acrylate oligomer with a molecular weight of 8000, 10 parts by weight of a curing agent (diisocyanate), and a UV curing reaction. 10 parts by weight of an initiator (benzophenone type) were mixed to form an adhesive composition.

This adhesive composition was applied to a 60 μm thick soft vinyl chloride (
DOP 30%, Cd-Ba thermal stabilizer, lubricant included) and a modified nylon thermal laminate with a thickness of 30 μm were coated on one side of the base material at a coating amount of 15 g/rd, and heated at 100°C.
The pressure-sensitive adhesive sheet of the present invention was prepared by heating for 1 minute.

A 5-inch silicon wafer was pasted on the obtained adhesive sheet, adhered to a flat frame, and diced into 5 mm squares with a 50 μm thick diamond blade as a full cut. The adhesive sheet was irradiated with ultraviolet light (illuminance: 200 mW/ad) for 3 seconds, and then expanded by 30% using an expanding jig. After 48 hours, the adhesive sheet did not come off from the flat frame and did not sag.

Furthermore, Table 1 shows the measurement results of the adhesive strength before and after irradiation with ultraviolet rays.

Note that the adhesive strength was measured as follows. That is, a test piece with a width of 25 mm was pressure-bonded to SUS 304, and after 20 minutes, the 180° peel adhesive strength was measured using a universal tensile tester (peel speed: 300 mm/min).

In addition, the evaluation results of restorability measured as described below were good.

Resilience evaluation: After elongating the test piece by 20%, it was opened for 10 seconds and 8
Heat at 0°C for 10 seconds. Before stretching and after 40 seconds of heating and cooling,
Measure the length of the specimen and calculate the recovery rate from the ratio. 85
% or more was judged as having good restorability.

Example 2 The dicing tape of Example 1 was heated to 70°C, relative humidity 60
% environment for 3 days, the wafer was diced, UV irradiated, and expanded by 30% in the same manner as in Example 1. There was no separation from the flat frame or sag, and the next step was die bonding. did it.

Furthermore, Table 1 shows the measurement results of the adhesive strength before and after irradiation with ultraviolet rays.

Restorability evaluation results were good.

Example 3 As a base material, soft vinyl chloride with a thickness of 60 μm (Example 1
A pressure-sensitive adhesive sheet for wafer attachment was prepared in the same manner as in Example 1, except that a base material made of a 20 μm thick urethanized photosensitive rubber coated on the same film as in Example 1 was used.

A 5-inch silicon wafer was pasted on the obtained adhesive sheet and adhered to a flat frame, and after cutting and dicing into 5 mm square pieces with a 50 μm thick diamond blade, only the wafer part was cut from the base material surface. The adhesive sheet was irradiated with ultraviolet light for 2 seconds (illuminance 200 mW/at>L, and then expanded by 30% using an expanding jig. After 48 hours, the adhesive sheet did not detach from the flat frame and did not sag. There wasn't.

Restorability evaluation results were good.

Furthermore, Table 1 shows the measurement results of the adhesive strength before and after irradiation with ultraviolet rays.

Example 4 The dicing tape of Example 3 was heated to 70°C, relative humidity 60°C.
After leaving the wafer in an environment of did it.

Furthermore, there was no significant change in adhesive strength before and after UV irradiation.

The measurement results are shown in Table 1.

Restorability evaluation results were good.

Example 5 ″ Soft vinyl chloride with a thickness of 60 μm (Example 1
(same film) and 15 μm thick ethylene-vinyl alcohol copolymer (vinyl alcohol content 58 mol%)
) A pressure-sensitive adhesive sheet for wafer adhesion was prepared in the same manner as in Example 1 except that a base material formed by dry laminating was used.

A 5-inch silicon wafer was pasted on the obtained adhesive sheet and adhered to a flat frame, and it was fully cut and diced into 5 mm square pieces using a 50 μm thick diamond blade. The adhesive sheet was irradiated with ultraviolet light for seconds (illuminance: 200 mW/al), and then expanded by 30% using an expanding jig. After 48 hours, the adhesive sheet did not separate from the flat frame and did not sag.

Restorability evaluation results were good.

Furthermore, Table 1 shows the measurement results of the adhesive strength before and after irradiation with ultraviolet rays.

Example 6 The dicing tape of Example 5 was heated to 70°C, relative humidity 60
% environment for 3 days, wafer dicing, UV irradiation, and 30% expansion were performed in the same manner as in Example 1. There was no separation from the flat frame or sag, and the die bonding was performed in the next process. did it.

Restorability evaluation results were good.

Furthermore, there was almost no change in adhesive strength before and after UV irradiation. The measurement results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed except that only soft vinyl chloride was used as the base material.

Restorability evaluation results were good.

Furthermore, Table 1 shows the measurement results of the adhesive strength before and after irradiation with ultraviolet rays.

Comparative Example 2 The dicing tape of Comparative Example 1 was heated to 70°C, relative humidity 60°C.
% environment for 3 days, wafer dicing, UV irradiation, and 30% expansion were performed in the same manner as in Example 1.

Restorability evaluation results were good.

Furthermore, the adhesive strength before UV irradiation was significantly reduced. The cause may be that the plasticizer or stabilizer in the soft vinyl chloride migrated to the adhesive layer. The measurement results are shown in Table 1.

Comparative Example 3 As a base material, soft hinyl chloride (DOP3
0%, including Cd-Ba stabilizers, lubricants, etc.) and thickness 2
An adhesive sheet for wafer attachment was prepared in the same manner as in Example 1, except that a base material formed by dry lamination with 0 μm L-LDPE was used.

A 5-inch silicon wafer was pasted on the obtained adhesive sheet and adhered to a flat frame, and after being fully cut and diced into 5 mm square pieces with a 50 μm thick diamond blade, the wafer part was cut from the base material side for 2 seconds. The adhesive sheet was irradiated with ultraviolet light (illuminance 200 mW/cnf) L, and then expanded by 30% using an expanding jig.

The restorability evaluation result was poor, with some sagging occurring.

Furthermore, Table 1 shows the measurement results of the adhesive strength before and after irradiation with ultraviolet rays.

Comparative Example 4 The dicing tape of Comparative Example 3 was heated to 70°C1 relative humidity 60°C.
% environment for 3 days, wafer dicing, UV irradiation, and 30% expansion were performed in the same manner as in Example 1, but there was no separation from the flat frame or sagging, and there was a problem with die bonding in the next process. I was able to implement it.

Restorability evaluation results were poor.

Furthermore, the adhesive strength before UV irradiation was reduced. It is clear that migration of plasticizers and stabilizers in soft vinyl chloride cannot be sufficiently prevented. The measurement results are shown in Table 1.

Table 1

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the adhesive sheet according to the present invention, and FIGS. 3 to 6 are explanatory views when the adhesive sheet is used from the dicing process to the pick-up process of semiconductor wafers. . DESCRIPTION OF SYMBOLS 1... Adhesive sheet, 2... Base material, 3... Adhesive layer, 4... Peeling sheet, A... Wafer, B... Radiation. Patent applicant Lintech Co., Ltd. Representative Patent attorney Shun Suzuki Part 1 Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) On a base material having at least two or more constituent layers,
In a pressure-sensitive adhesive sheet for pasting wafers coated with a pressure-sensitive adhesive layer, one layer constituting the base material is made of soft vinyl chloride, and another layer constituting the base material is in contact with the pressure-sensitive adhesive layer and is in contact with the base material. A pressure-sensitive adhesive sheet for wafer attachment, characterized in that the other layer constituting the material is made of modified nylon, urethanized photosensitive rubber or resin, ethylene/vinyl alcohol copolymer, or polyvinylidene chloride.