JP2002371262A - Self-adhesive for wafer-processing self-adhesive sheet and wafer-processing self-adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-adhesive for a wafer-processing self-adhesive sheet hardly generating a transferred contaminant and to provide a wafer-processing self-adhesive sheet provided with a self-adhesive layer formed of the self-adhesive. SOLUTION: The self-adhesive for a wafer-processing self-adhesive sheet comprises as a main component a base polymer having a weight-average molecular weight of at least 100,000 and a molecular weight distribution (weight- average molecular weight/number-average molecular weight) of 1-2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive for a wafer processing pressure-sensitive adhesive sheet and a wafer processing pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive. Adhesive sheet for wafer processing is a surface protection adhesive sheet used to protect the surface of the wafer in the grinding process of grinding the back surface of the semiconductor wafer in various semiconductor manufacturing processes, and the semiconductor wafer is cut and divided into element pieces. It is useful as an adhesive sheet for fixed support to be attached to the back surface of a wafer in a dicing step of automatically collecting the element pieces by a pickup method.

[0002]

2. Description of the Related Art Various adhesive sheets have been proposed as adhesive sheets for processing semiconductor wafers. In addition, semiconductor wafers are becoming larger and IC wafers are becoming thinner. The radiation-curable pressure-sensitive adhesive sheet is increasingly used as the protective sheet used for processing the wafer because it is lightly peeled. Is coming.

[0003] From such an adhesive sheet for processing a wafer, some transfer contaminants (adhesive residue) are usually generated on a semiconductor element. Such transfer contaminants, for example, cause a wire bonding failure in a subsequent step in a surface protection adhesive sheet, and cause a problem of a package crack in a resin sealing step (packaging step) in a fixed support adhesive sheet. It is clear that Therefore, in recent years, there has been a demand for a high-quality pressure-sensitive adhesive sheet for processing a wafer which is free from transfer contaminants.

In general, it is known that transfer contaminants are low molecular weight components having a molecular weight of less than 100,000 contained in an adhesive. The low molecular weight component is originally contained in a polymer compound called a base polymer, which is a main component of the pressure-sensitive adhesive, and can be removed by purification. In order to reduce low molecular weight components, for example, there is a method in which a polymer having a high degree of dispersion is produced by general-purpose radical polymerization or the like, and the polymer is purified by a reprecipitation method or the like. However, in this method, a low molecular weight component having a molecular weight of less than 100,000
It is difficult to completely remove by a single operation, and the operation is complicated.

In general, a radiation-curable pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer of a radiation-curable pressure-sensitive adhesive sheet comprises a polymer compound called a base polymer and a radiation-polymerizable compound having a carbon-carbon double bond in the molecule ( It is prepared by appropriately adding various additives such as a radiation-reactive oligomer, a radiation-polymerizable initiator, and a crosslinking agent. Usually, so-called polyfunctional compounds having two or more carbon-carbon double bonds in one molecule are often used as the radiation-polymerizable compound in order to impart the property that the adhesive strength is greatly reduced after irradiation. ing. When radiation is applied to such a radiation-curable pressure-sensitive adhesive, the radiation-polymerizable compound reacts to quickly form a three-dimensional network structure, and the entire pressure-sensitive adhesive rapidly reacts and cures, and the adhesive strength decreases. Have been. However, such polyfunctional compounds are often low molecular weight components of oligomers or monomers having a molecular weight of less than 100,000, and the problem of transfer contaminants cannot be solved for the above-mentioned reasons.

[0006]

SUMMARY OF THE INVENTION The present invention provides a pressure-sensitive adhesive for a wafer processing pressure-sensitive adhesive sheet with less transfer contaminants, and further includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive. An object of the present invention is to provide an adhesive sheet for processing a wafer. Another object of the present invention is to provide a method for manufacturing a semiconductor wafer using the wafer processing sheet, and a semiconductor element manufactured by the manufacturing method.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the following pressure-sensitive adhesive for wafer processing adhesive sheet and pressure-sensitive adhesive sheet for processing have been developed.
The inventors have found that the above object can be achieved, and have completed the present invention.

That is, according to the present invention, the weight average molecular weight is 10
And the degree of dispersion of the molecular weight (weight average molecular weight /
A pressure-sensitive adhesive for a wafer processing pressure-sensitive adhesive sheet, comprising a base polymer having a number average molecular weight of 1 to 2 as a main component.

In the pressure-sensitive adhesive of the present invention, a low-molecular-weight component in the base polymer is reduced by using a base polymer having a weight-average molecular weight not less than the above-mentioned predetermined amount and a monodisperse degree of dispersion. This reduces the generation of transfer contaminants. The weight average molecular weight is preferably 100,000 or more, more preferably 300,000 to 1,500,000. The degree of dispersion is preferably from 1 to 2, and more preferably from 1.05 to 1.70.

The measurement of the weight average molecular weight and the degree of dispersion are as follows.
It was measured by GPC (Gel-Permeation Chromatograph) and defined as "TSK standard polystyrene" converted value. GPC device: Tosoh HLC-8120GPC Column: TSKgel SuperHM-H / H400
0 / H3000 / H2000 Flow rate: 0.6 ml / min Concentration: 0.3 wt% Injection volume: 20 μl Column temperature: 40 ° C. Eluent: tetrahydrofuran

In a preferred embodiment of the pressure-sensitive adhesive for a wafer processing pressure-sensitive adhesive sheet, the base polymer is a radiation-curable polymer.

By making the base polymer itself a radiation-curable polymer, the pressure-sensitive adhesive can be made radiation-curable without using a radiation-polymerizable compound such as a radiation-reactive oligomer.

[0013] The present invention also relates to a pressure-sensitive adhesive sheet for wafer processing, comprising a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive for a pressure-sensitive adhesive sheet for wafer processing. Further, the present invention relates to a method for manufacturing a semiconductor wafer using the wafer processing sheet. The present invention also relates to a semiconductor device manufactured by the manufacturing method.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As a base polymer which is a main component of the pressure-sensitive adhesive for a wafer processing pressure-sensitive adhesive sheet, a general pressure-sensitive pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive or the like is used. Anything can be used. Above all, an acrylic polymer, which is a base polymer of an acrylic adhesive, is preferable from the viewpoint of adhesiveness to a semiconductor wafer.
These base polymers may be used as a mixture of two or more kinds.

Examples of the acrylic polymer include (meth) acrylic acid alkyl esters (eg, methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, Pentyl ester, isopentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester, tridecyl ester,
Linear or branched alkyl esters having 1 to 30 carbon atoms, particularly 4 to 18 carbon atoms, such as alkyl groups such as tetradecyl ester, hexadecyl ester, octadecyl ester and eicosyl ester) and (meth) acrylic acid An acrylic polymer using one or more of cycloalkyl esters (for example, cyclopentyl ester, cyclohexyl ester, etc.) as a monomer component is exemplified. In addition, (meth) acrylic acid ester means acrylic acid ester and / or methacrylic acid ester, and (meth) in the present invention has the same meaning.

The above-mentioned acrylic polymer may be used, if necessary, for the purpose of modifying the cohesive strength, heat resistance, etc.
It may contain a unit corresponding to another monomer component copolymerizable with the alkyl acrylate or the cycloalkyl ester. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid; and maleic anhydride. , Acid anhydride monomers such as itaconic anhydride; (meth)
2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate,
10-hydroxydecyl (meth) acrylate, (meth)
Hydroxyl group-containing monomers such as 12-hydroxylauryl acrylate and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate; styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamide-
Sulfonic acid group-containing monomers such as 2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalenesulfonic acid; phosphoric acid groups such as 2-hydroxyethylacryloyl phosphate Monomer: acrylamide, acrylonitrile and the like. One or two or more of these copolymerizable monomer components can be used. The amount of these copolymerizable monomers to be used is preferably 50% by weight or less of all the monomer components.

Further, the acrylic polymer may contain a polyfunctional monomer or the like as a monomer component for copolymerization, if necessary, for crosslinking. Such polyfunctional monomers include, 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, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate
Acrylate, dipentaerythritol hexa (meth)
Examples include acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and urethane (meth) acrylate. One or more of these polyfunctional monomers can be used. The amount of the polyfunctional monomer to be used is preferably 30% by weight or less of the total monomer components from the viewpoint of adhesive properties and the like.

The weight average molecular weight of the base polymer of the present invention is 100,000 or more, and the degree of dispersion of the molecular weight is 1-2. Such base polymers, for example, can be used to oxidize metals.
A so-called living polymerization method, in which the polymerization reaction proceeds while the growth reaction is completely controlled, such as the initiation of living radical polymerization utilizing a reduction reaction or coordination polymerization using a samarium complex as an initiator, can be employed. According to such a polymerization method, the molecular weight can be easily set, and the degree of dispersion of the molecular weight can be set small, so that the production of a low-molecular-weight substance having a molecular weight of 100,000 or less can be suppressed when the polymerization reaction of the polymer is completed.

A radiation-curable polymer can be used as the base polymer of the present invention. Even when a radiation-curable polymer is used, the weight-average molecular weight is 100,000 or more and the degree of dispersion of the molecular weight is 1-2. The radiation-curable polymer has a carbon-carbon double bond in the polymer side chain or in the main chain or at the main chain terminal, and does not need to contain, or does not contain, many low molecular components such as oligomer components. Therefore, it is preferable because the pressure-sensitive adhesive layer having a stable layer structure can be formed without the oligomer component and the like moving in the pressure-sensitive adhesive over time.

As the radiation-curable polymer, those having a carbon-carbon double bond and having tackiness can be used without any particular limitation. As such a base polymer, a polymer having an acrylic polymer as a basic skeleton is preferable. Examples of the basic skeleton of the acrylic polymer include the acrylic polymers exemplified above.

The method of introducing a carbon-carbon double bond into the acrylic polymer is not particularly limited, and various methods can be adopted. However, the introduction of the carbon-carbon double bond into the polymer side chain requires a molecular design. Easy. For example, after previously copolymerizing a monomer having a functional group in an acrylic polymer,
There is a method in which a compound having a functional group capable of reacting with the functional group and a carbon-carbon double bond is subjected to a condensation or addition reaction while maintaining the radiation curability of the carbon-carbon double bond.

Examples of combinations of these functional groups include a carboxylic acid group and an epoxy group, a carboxylic acid group and an aziridyl group,
Examples include a hydroxyl group and an isocyanate group.
Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferable because of easy tracing of the reaction. In addition, as long as the combination of these functional groups produces an acrylic polymer having the carbon-carbon double bond, the functional group may be on either side of the acrylic polymer and the compound. In the above preferred combination, it is preferable that the acrylic polymer has a hydroxyl group and the compound has an isocyanate group. In this case, as the isocyanate compound having a carbon-carbon double bond, for example, methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, m-isopropenyl-α, α
-Dimethylbenzyl isocyanate.
Further, as the acrylic polymer, those obtained by copolymerizing the above-described hydroxy group-containing monomer, ether compounds of 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like are used.

The amount of carbon-carbon double bonds in the base polymer is determined according to JIS K-00 in consideration of the storage stability of the pressure-sensitive adhesive.
An iodine value of 30 or less, and an iodine value of 0.
It is preferably 5 to 20.

When a radiation-curable polymer is used as the base polymer, the pressure-sensitive adhesive layer is cured by radiation such as X-rays, ultraviolet rays, and electron beams. Initiator is included. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α′-dimethylacetophenone, and 2-methyl-2-hydroxypropion. Phenon,
Α such as 1-hydroxycyclohexyl phenyl ketone
-Ketol compounds; methoxyacetophenone, 2, 2
-Dimethoxy-2-phenylacetophenone, 2,2-
Diethoxyacetophenone, 2-methyl-1- [4-
Acetophenone compounds such as (methylthio) -phenyl] -2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether and anisoin methyl ether;
Ketal compounds such as benzyldimethyl ketal; 2
Aromatic sulfonyl chloride compounds such as -naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (o-ethoxycarbonyl) oxime; benzophenone, benzoylbenzoic acid, 3,3 Benzophenone compounds such as'-dimethyl-4-methoxybenzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxan Song,
Thioxanthone compounds such as 2,4-diethylthioxanthone and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphinoxides; acylphosphonates.

The amount of the photopolymerization initiator to be added is 0.1 in consideration of reactivity with respect to 100 parts by weight of the radiation-curable polymer.
It is preferably at least 1 part by weight, more preferably at least 0.5 part by weight. In addition, since the preservability of the pressure-sensitive adhesive tends to decrease as the content increases, the content is preferably 15 parts by weight or less, more preferably 5 parts by weight or less.

In the pressure-sensitive adhesive for a pressure-sensitive adhesive sheet for processing a wafer of the present invention, an external crosslinking agent can be appropriately employed in addition to the base polymer. As a specific means of the external cross-linking method, a method of adding a so-called cross-linking agent such as a polyisocyanate compound, an epoxy compound, an aziridine compound, a melamine-based cross-linking agent, and causing a reaction is used. When an external crosslinking agent is used, the amount of the external crosslinking agent is appropriately determined depending on the balance with the base polymer to be crosslinked, and further on the use of the pressure-sensitive adhesive. Generally, it is preferable to add about 0.1 to 5 parts by weight to 100 parts by weight of the base polymer. These cross-linking agents are materials that are generally low molecular components but can react with the base polymer,
After the reaction, it is incorporated as a part of the polymer chain and does not become a transfer contamination source.

Hereinafter, the pressure-sensitive adhesive sheet for processing a wafer according to the present invention will be described in detail with reference to FIG. As shown in FIG.
In the pressure-sensitive adhesive sheet for processing a wafer of the present invention, a pressure-sensitive adhesive layer 2 is provided on a base film 1. Further, a separator 3 is provided on the pressure-sensitive adhesive layer 2 as necessary. In FIG. 1, the adhesive film 2 is provided on one side of the base film 1, but these may be formed on both sides of the base film 1.
The pressure-sensitive adhesive sheet for processing a wafer can be formed into an appropriate shape such as a shape corresponding to the planar shape of the object to be cut such as a base or a wafer, a continuous sheet, or the like, or can be wound into a tape to form a tape.

The material of the base film 1 is not particularly limited, but it is preferable to use a material that transmits at least a part of a predetermined or more radiation. For example, for wafer grinding applications in general, low-density polyethylene, linear polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymerized polypropylene, block copolymerized polypropylene, homopolyprolene, polybutene, polymethylpentene , Ethylene-vinyl acetate copolymer, ionomer resin, ethylene- (meth) acrylic acid copolymer, ethylene- (meth)
Acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, ethylene-hexene copolymer,
Polyurethane, polyester such as polyethylene terephthalate, polyimide, polyetheretherketone,
Examples include polymers such as fluororesins, cellulosic resins, and crosslinked products thereof. For wafer cutting / separation applications, in addition to the various films described above, polyvinyl chloride and soft polyvinyl chloride using polyvinylidene chloride are often used.

The thickness of the base film 1 can be appropriately selected within a range that does not impair the operability and workability in the application, but is usually about 500 μm or less, preferably about 3 to 300 μm, more preferably about 5 to 250 μm. is there. The base film 1 can be formed by a conventionally known film forming method. For example, a wet casting method, an inflation extrusion method, a T-die extrusion method, or the like can be used. The base film 1 may be used in a non-stretched state, or may be subjected to a uniaxial or biaxial stretching treatment as necessary. If necessary, the surface of the base film 1 may be subjected to a chemical or physical treatment such as chromic acid treatment, ozone exposure, flame exposure, high-voltage impact exposure, ionizing radiation treatment, etc. ) May be applied.

Although the thickness of the pressure-sensitive adhesive layer 2 may be appropriately selected,
Generally, about 1 to 300 μm or less, preferably 3 to 20 μm.
0 μm, more preferably 5 to 100 μm. The adhesive strength of the pressure-sensitive adhesive layer may be appropriately determined according to the purpose of use and the like. However, in general, the adhesive strength before radiation irradiation (23 ° C.) , 180 ° peel value, peeling speed 300mm
/ Min) is preferably 1 N / 25 mm tape width or more, and the adhesive strength after radiation irradiation is 0.4 N / 25 mm tape width or less.

The production of the pressure-sensitive adhesive sheet for processing a wafer of the present invention can be carried out, for example, by a method of applying a pressure-sensitive adhesive to the base film 1 to form a pressure-sensitive adhesive layer 2. Alternatively, a method of separately forming the pressure-sensitive adhesive layer 2 on the separator 3 and bonding the same to the base film 1 can be employed.

The pressure-sensitive adhesive layer 2 of the pressure-sensitive adhesive sheet for wafer processing is covered and protected by the separator 3 until the pressure-sensitive adhesive layer 2 adheres to an object to be cut such as a semiconductor wafer in order to prevent contamination during storage and distribution. Is preferred. Examples of the constituent material of the separator 3 include paper, synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate. The surface of the separator 3 may be subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, a fluorine treatment, or the like, as necessary, in order to enhance the releasability.
The thickness of the separator 3 is usually about 10 to 200 μm, preferably about 25 to 100 μm.

[0033]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[0034] Example 1 (Preparation of samarium complex) 1 liter flask which was purged with argon, the SmI ₂ 3.9616g, placed 330ml of tetrahydrofuran (THF), with stirring, Bae pointer methylcyclopentadienyl pen Taj enyl potassium salt ((C ₅ (CH ₃ ) ₅ ) K)
45.858 g was added and reacted at room temperature. afterwards,
The THF was removed under reduced pressure, toluene was added to the solid, the supernatant was collected, and dried under reduced pressure, and then (C ₅ (CH ₃ ) ₅ ) ₂ Sm (THF) ₂ was recrystallized with THF and hexane. Was. This (C
_After 2.5 g of ₅ (CH ₃ ) ₅ ) ₂ Sm (THF) ₂ was dissolved in 60 ml of toluene, 2.2 ml of trimethylaluminum was added, and the mixture was stirred and reacted. After removing the precipitate, recrystallization was performed to obtain (C ₅ (CH ₃ ) ₅ ) ₂ Sm (CH ₃ ) (THF).

(Preparation of trimethylsilyloxyethyl acrylate) Dry THF 3 was placed in a 1-liter round bottom flask.
Weigh out 00 ml and add dry triethylamine 11
1.6 ml and dry 2-hydroxyethyl acrylate 8
3.7 ml was added. After stirring for about 10 minutes, the greed was cooled with ice water and dried trimethylsilyl chloride.
1 ml was added slowly. After stirring at room temperature for 24 hours, THF, excess triethylamine and trimethylsilyl chloride were distilled off under reduced pressure. There dry hexane 3
After stirring for about 2 hours, the salt was removed by filtration, hexane was distilled off under reduced pressure, and the residue was treated with molecular sieves for 2 nights, and distilled at 42 ° C./0.1 mmHg to obtain trimethylsilyloxyethyl. Acrylate was synthesized.

(Preparation of Acrylic Copolymer) The above-mentioned (C ₅ (CH ₃ )) was placed in a 1-liter flask purged with argon.
_{5) 2} Sm (CH ₃₎ (THF) as placed 100.4 mg, deaerated dehydrated by adding toluene 400 ml, was cooled to -78 ° C., degassed dehydrated butyl acrylate 80g and trimethylsilyloxy acrylate 20g
Is added dropwise over 1 hour to carry out a polymerization reaction.
The polymerization reaction was continued for 5 hours. Five hours later, a large amount of methanol was added to terminate the polymerization, and at the same time, a trimethylsilyl group as a protecting group was eliminated to OH-end the terminal. The molecular weight of the acrylic copolymer obtained after filtration and drying was measured by a GPC method, and as a result, the weight average molecular weight was 35.3.
10,000, the number average molecular weight was 3240, and the degree of dispersion (weight average molecular weight / number average molecular weight) was 1.09.

(Preparation of Wafer Processing Adhesive Sheet) The acrylic copolymer was dissolved in toluene, and 0.8 part by weight of an isocyanate-based crosslinking agent was further added to 100 parts by weight of this polymer (solid content). The pressure-sensitive adhesive sheet obtained by applying the pressure-sensitive adhesive obtained on the polyethylene film (base film) having a thickness of 100 μm so as to have a thickness of 30 μm after drying to form a pressure-sensitive adhesive layer. I got

Example 2 (Preparation of acrylic copolymer) In Example 1, the amount of (C ₅ (CH ₃ ) ₅ ) ₂ Sm (CH ₃ ) (THF) was changed to 100.4%.
Example 1 except that the dose was changed from 5 mg to 50.7 mg.
The same operation as described above was performed. The weight-average molecular weight of the obtained acrylic copolymer is 545,000, and the number-average molecular weight is 3
87,000 and the degree of dispersion was 1.41.

(Preparation of radiation-curable polymer) The above-mentioned acrylic copolymer solution was further added with an organotin catalyst and 2
By adding 5 g of methacryloyloxyethyl isocyanate and performing an addition reaction, the weight average molecular weight is 56.
A radiation-curable polymer solution having a molecular weight of 100,000, a number average molecular weight of 3,990,000 and a dispersity of 1.44 was obtained.

(Preparation of pressure-sensitive adhesive sheet for wafer processing) To 100 parts by weight of the radiation-curable polymer (solid content), 0.8 part by weight of an isocyanate-based crosslinking agent and 2 parts by weight of an acetophenone-based photopolymerization initiator were further added. The radiation-curable pressure-sensitive adhesive obtained as described above is applied on a 100-μm-thick polyethylene film so that the thickness after drying becomes 30 μm to form a pressure-sensitive adhesive layer, thereby forming a pressure-sensitive adhesive sheet for wafer processing. Obtained.

Comparative Example 1 In the same manner as in Example 1, except that the amount of (C ₅ (CH ₃ ) ₅ ) ₂ Sm (CH ₃ ) (THF) was changed from 100.4 mg to 300 mg. Was performed. The weight average molecular weight of the obtained acrylic copolymer was 950,000, the number average molecular weight was 82,000, and the dispersity was 1.15. Thereafter, an adhesive was prepared in the same manner as in Example 1 using the obtained acrylic copolymer to obtain an adhesive sheet for wafer processing.

Comparative Example 2 In a flask purged with nitrogen, butyl acrylate 100
g, 105 g of ethyl acetate, 45 g of toluene and 4,4
-Add 0.2 g of azobisisobutyronitrile,
For 12 hours, and the weight average molecular weight is 32.6.
An acrylic copolymer solution having a number average molecular weight of 720,000 and a dispersity of 4.53 was obtained. Thereafter, an adhesive was prepared in the same manner as in Example 1 using the obtained acrylic copolymer to obtain an adhesive sheet for wafer processing.

Comparative Example 3 To 100 parts by weight of the acrylic copolymer (solid content) obtained in Example 1, 50 parts by weight of pentaerythritol triacrylate having a molecular weight of less than 100,000 and an acetophenone-based photopolymerization initiator Of a radiation-curable pressure-sensitive adhesive obtained by adding 2 parts by weight of was added onto a 100 μm-thick polyethylene film so that the thickness after drying was 30 μm to form a pressure-sensitive adhesive layer. An adhesive sheet for wafer processing was obtained.

The following evaluations were made on the pressure-sensitive adhesive sheets for wafer processing obtained in Examples and Comparative Examples. Example 2,
In Comparative Example 3, ultraviolet rays were irradiated after the processing. Table 1 shows the evaluation results.

(Amount of Transfer Contaminant on Wafer Surface) A pressure-sensitive adhesive sheet for wafer processing was attached to the wafer surface, the back surface was ground to a predetermined thickness under the following conditions, and then peeled off. The amount of transferred contaminant on the peeled wafer surface was measured. The element ratio on the wafer surface after peeling the adhesive sheet is measured by XPS (X-ray photoelectron spectroscopy), and the increase in carbon originating from transfer contaminants from the adhesive sheet is calculated as the atomic% increase compared to the blank wafer. did. X-ray source: MgKα, X-ray extraction angle: 90 degrees,
Measurement area: 1.0 mm x 3.5 mm.

<Wafer grinding conditions> Grinding device: DFG-840 manufactured by DISCO Wafer: 6 inch diameter (backside grinding from 600 μm to 100 μm) Wafer bonding device: DR-8500II (manufactured by Nitto Seiki Co., Ltd.) ) Irradiation device: NEL UM-110 (manufactured by Nitto Seiki Co., Ltd.) UV irradiation integrated light amount: 500 mJ / cm ² .

(Test of Package Crack) An adhesive sheet for processing a wafer was attached to the back surface of the wafer, diced into chips of a predetermined size under the following conditions, and the cut chips were sealed in a semiconductor sealing resin MP7410TAH manufactured by Nitto Denko Corporation. The sample was stopped and subjected to a moisture absorption treatment under the condition of 85 ° C./85% RH for 300 hours, heated on a hot plate at 240 ° C. for 30 seconds, and examined for the occurrence of package cracks.

<Wafer dicing conditions> Dicing device: DFD2S / 8 manufactured by DISCO Dicing speed: 100 mm / sec Dicing blade: 2050 HEDD manufactured by DISCO Number of rotations of dicing blade: 40000 rpm Dicing tape cutting depth: 30 μm Wafer chip size: 10 mm × 10 mm Wafer diameter: 6 inches.

[0049]

[Table 1] From Example 1 and Comparative Example 1, it can be seen that, even when the degree of dispersion is in the range of 1-2, when the weight average molecular weight is less than 100,000, transfer contaminants are large during wafer grinding and cracks are generated. From Example 1 and Comparative Example 2, the weight average molecular weight was 1
If the degree of dispersion exceeds 2 even if it is not less than 100,000, the transfer contaminants are large and cracks occur as described above. Further, from Example 2 and Comparative Example 3, when preparing a radiation-curable pressure-sensitive adhesive, it can be understood that the problem of transfer contaminants and cracks cannot be eliminated with a configuration in which a radiation-polymerizable compound having a molecular weight of less than 100,000 is mixed. .

[Brief description of the drawings]

FIG. 1 is a sectional view of an adhesive sheet for dicing.

[Explanation of symbols]

 1: base film 2: adhesive layer 3: separator

Continued on the front page F term (reference) 3C058 AA07 AB04 CA01 DA17 4J004 AA10 AA14 AB06 CA02 CA03 CA04 CA05 CA06 CC02 DA02 DA04 DA05 DB02 EA01 FA05 4J040 DF031 EB132 EC002 EF101 EF102 EF282 GA01 HC22 JA09 JB01 MA01 PA23 PA30 PA32

Claims (5)

[Claims] 1. A wafer comprising a base polymer having a weight average molecular weight of 100,000 or more and a molecular weight dispersity (weight average molecular weight / number average molecular weight) of 1 to 2 as a main component. Adhesive for processing adhesive sheet. 2. The pressure-sensitive adhesive according to claim 1, wherein the base polymer is a radiation-curable polymer. 3. A pressure-sensitive adhesive sheet for wafer processing, comprising a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive according to claim 1 on a base film. 4. A method for manufacturing a semiconductor wafer using the wafer processing sheet according to claim 3. 5. A semiconductor device manufactured by the manufacturing method according to claim 4.