JPH1161065A - Pressure-sensitive adhesive sheet for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure-sensitive adhesive sheet which exhibits an excellent pressure-sensitive adhesive power to a semiconductor wafer and is excellent in resistance to chipping by forming a pressure-sensitive adhesive layer polymerizable and curable with ultraviolet rays and/or an electron beam and having a specific compsn. on a substrate and by specifying the cohesive power of the layer and the strength of adhesion of the layer to a semiconductor wafer. SOLUTION: This pressure-sensitive adhesive sheet is prepd. by forming a pressure-sensitive adhesive layer contg. a base polymer, a radiation-curable compd. and a radiation polymn. initiator on a substrate transparent to ultraviolet rays and/or an electron beam. The strength of adhesion of this pressure-sensitive adhesive layer to a semiconductor wafer is 50-500 g/25 mm before the irradiation with ultraviolet rays and/or an electron beam and is 5-40 g/25 mm after the irradiation. The cohesive power of the adhesive layer before the irradiation is such that the distance of slippage after 3, 600 sec is 5 mm or less in the test of holding power according to JIS Z 0237. The adhesive layer comprises 100 pts.wt. base polymer, 50-200 pts.wt. radiation-polymerizable compd. and 0.03-22.5 pts.wt. radiation polymn. initiator.

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 sheet for processing semiconductor wafers, comprising a substrate and a pressure-sensitive adhesive layer.

[0002]

2. Description of the Related Art Heretofore, a semiconductor wafer processing sheet used for attaching a semiconductor wafer, performing dicing, expanding, and the like, picking up the semiconductor wafer and mounting the semiconductor wafer at the same time has been used.
Alternatively, ultraviolet rays and / or
Or, using a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that undergoes a polymerization-curing reaction by an electron beam, irradiates the pressure-sensitive adhesive layer with ultraviolet rays and / or an electron beam after dicing, and causes the pressure-sensitive adhesive layer to undergo a polymerization-curing reaction to reduce the adhesive force. Semiconductor wafer (chip)
A method of picking up is known. For example, Japanese Patent Application Laid-Open Nos. 60-199696 and 60-22313
No. 9 discloses, as a photopolymerizable initiator constituting a pressure-sensitive adhesive layer, ultraviolet and / or electron beam polymerization in a molecule such as trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, or oligoester acrylate. It has been proposed to use an acrylic resin-based compound having at least two or more carbon-carbon double bonds.

However, in the pressure-sensitive adhesive layer using the above compound, the viscosity of the entire compound is reduced due to the low viscosity of the compound, the cohesive force becomes insufficient, and the chip is likely to be misaligned or lifted during dicing. There is a drawback that chipping (chip chipping) and chip fly are likely to occur. Here, the cohesive force is a force of molecules in the pressure-sensitive adhesive layer to gather together, and is a resistance to plastic deformation due to external stress. It is usually evaluated by JISZ0237 holding power.

Japanese Patent Application Laid-Open No. Sho 62-153376 proposes to use a polyfunctional urethane acrylate oligomer having a molecular weight of about 3,000 to 10,000, but a polyfunctional urethane acrylate oligomer having a molecular weight in such a range. In the pressure-sensitive adhesive layer using oligomers, the pressure-sensitive adhesive on the dicing line peels off and contaminates the chip, and the cohesive force of the pressure-sensitive adhesive layer is insufficient, causing problems such as chipping and chip scattering during dicing. There is a disadvantage that it is easy.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure sensitive adhesive sheet for processing semiconductor wafers which exhibits excellent adhesive strength to a semiconductor wafer and has excellent chipping resistance.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to ultraviolet and / or ultraviolet radiation.
Or a pressure-sensitive adhesive sheet for processing a semiconductor wafer in which a pressure-sensitive adhesive layer containing a base polymer, a radiation-polymerizable compound and a radiation-polymerizable polymerization initiator is formed on a substrate surface having transparency to an electron beam; Force 50-500g / 25m before UV and / or electron beam irradiation
m, after irradiation, 5 to 40 g / 25 mm, and the adhesive force for holding the pressure-sensitive adhesive layer before irradiation is 5 mm or less after 3600 seconds in JISZ0237. It is a sheet.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, the pressure-sensitive adhesive layer provided on the substrate may be caused to undergo a polymerization and curing reaction by ultraviolet rays and / or electron beams,
The pressure-sensitive adhesive layer contains a radiation-polymerizable compound, a radiation-polymerizable polymerization initiator, and the like.
In Z0237, the displacement distance after 3600 seconds in holding force is 5 mm or less (preferably 3 mm or less, more preferably 1 mm or less).
mm or less), the chip is less likely to be misaligned or lifted during dicing, resulting in less chipping (chip chipping) and chip flying, and undergoes a polymerization and curing reaction by irradiating ultraviolet rays and / or an electron beam. Since the fluidity is reduced, the adhesive strength is reduced, and the chip can be easily picked up. Furthermore, since it has a certain degree of breaking elongation even after curing, it is possible to prevent the pressure-sensitive adhesive layer from cracking at the time of expanding, and to maintain uniform alignment of chip intervals.

In the present invention, the adhesive strength to a semiconductor wafer is 50 to 500 g before irradiation with ultraviolet rays and / or electron beams.
/ 25mm, preferably 100-500g / 25mm,
After irradiation, 5 to 40 g / 25 mm, preferably 10 to 4 g
0 g / 25 mm. Adhesion before irradiation is 50g / 25
If it is less than mm, chip fly tends to occur during dicing, and if it exceeds 500 g / 25 mm, the adhesive strength after irradiation is not sufficiently reduced. Adhesion after irradiation is 5g / 25
If it is less than mm, the chip is likely to peel off during expanding, and if it exceeds 40 g / 25 mm, it becomes difficult to pick up the chip.

The substrate used in the present invention includes:
There is no particular limitation as long as it has transparency to ultraviolet rays and / or electron beams. For example, vinyl chloride, polyethylene terephthalate, polyethylene, polypropylene,
Polyurethane, ethylene-vinyl acetate copolymer, ethylene-hexene copolymer, ethylene-butene copolymer, ethylene-propylene-butene copolymer and the like are used.

The base polymer used in the present invention is not particularly limited. For example, a polymer comprising acrylic acid, methacrylic acid and their esters, and a copolymer copolymerizable with acrylic acid, methacrylic acid and their esters Unsaturated monomers such as vinyl acetate,
A copolymer with styrene, acrylonitrile, or the like is used. In addition, the pressure-sensitive adhesive of the present invention includes a rosin resin, a terpene resin, a coumarone resin, a phenol resin, a styrene resin, an aliphatic petroleum resin, an aromatic petroleum resin, and an aliphatic aromatic A tackifier such as a resin may be added.

The radiation-polymerizable compound mixture used in the present invention has a sufficient adhesive strength to a semiconductor wafer before a curing reaction by ultraviolet rays and / or an electron beam, and after the curing reaction, the adhesive force is reduced, and The wafer (chip) can be easily picked up and 5000 or more, preferably 8000 or more in order to maintain high cohesion.
More preferably, it is necessary to mix a polyfunctional urethane acrylate having a molecular weight of 10,000 or more with a polyfunctional acrylate monomer having a molecular weight of 1,000 or less or two or more acrylate monomers.

[0012] By using a polyfunctional urethane acrylate having a molecular weight of 5000 or more, a sufficient cohesive force can be imparted to the pressure-sensitive adhesive layer before the curing reaction. There is no danger of peeling and falling off. Moreover, the adhesive strength can be stabilized even when exposed for a long time under a fluorescent lamp, and the adhesive layer after the curing reaction can be given a sufficient cohesive force,
Chipping and chip scattering during dicing can be suppressed. If the molecular weight is less than 5000, the viscosity becomes low, the cohesive strength of the pressure-sensitive adhesive layer becomes insufficient, and if the number of functional groups is 1, the cross-linking density of the pressure-sensitive adhesive layer after curing is not sufficiently increased, and the pressure-sensitive adhesive strength is not reduced. Will be enough.

On the other hand, if only a polyfunctional urethane acrylate having a molecular weight of 5,000 or more is used, it is difficult to handle because it has a high viscosity, and the adhesive strength after curing is not sufficiently reduced, making it difficult to pick up a chip. When a polyfunctional acrylate monomer having a molecular weight of 1,000 or less is used in combination to adjust this, the balance of adhesive properties becomes suitable. The use of a polyfunctional acrylate monomer is to increase the crosslink density of the pressure-sensitive adhesive layer after curing and to sufficiently reduce the adhesive force. This makes it difficult to pick up the data.

The polyfunctional urethane acrylate in the radiation-polymerizable compound used in the present invention is a compound synthesized from diisocyanate, polyol and hydroxy (meth) acrylate, and is preferably a urethane acrylate having two acryloyl groups. is there.
Examples of the isocyanate include toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, phenylene diisocyanate, dicyclohexyl methane diisocyanate, xylene diisocyanate, tetramethyl xylene diisocyanate, and naphthalene diisocyanate. Examples of the polyol include ethylene glycol, propylene glycol, butanediol,
Hexanediol and the like can be mentioned. Examples of the hydroxy (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and the like.

The polyfunctional acrylate monomer in the radiation polymerizable compound includes, for example, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,
Examples thereof include dipentaerythritol monohydroxypentaacrylate and dipentaerythritol hexaacrylate. The weight ratio between the polyfunctional urethane acrylate of the radiation polymerizable compound and the polyfunctional acrylate monomer is in the range of 10:90 to 90:10, preferably in the range of 30:70 to 70:30. If the weight ratio of the polyfunctional urethane acrylate is less than 10, the cohesive strength of the pressure-sensitive adhesive layer becomes insufficient, and if it exceeds 90, the adhesive strength after curing is not sufficiently reduced, and it becomes difficult to pick up chips.

The mixing ratio of the radiation-polymerizable compound and the radiation-polymerizable polymerization initiator is such that the radiation-polymerizable compound is 50 to 200 parts by weight, and the radiation-polymerizable polymerization initiator is 0.03 to 22 parts by weight based on 100 parts by weight of the base polymer. The mixing ratio is 0.5 parts by weight. When the proportion of the radiation-polymerizable compound is less than 50 parts by weight, the adhesive strength after curing is not sufficiently reduced, making it difficult to pick up a chip. When the proportion exceeds 200 parts by weight, the cohesive strength of the adhesive layer is insufficient, which is not preferable. . When the proportion of the radiation-polymerizable polymerization initiator is less than 0.03 parts by weight, ultraviolet rays and / or
Alternatively, the curing reaction of the radiation-polymerizable compound upon electron beam irradiation becomes poor, and the decrease in adhesive strength becomes insufficient. Thus, if it exceeds 22.5 parts by weight, the stability under heat or fluorescent light becomes poor, which is not preferable.

In the present invention, the thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably about 5 to 35 μm. In the present invention, to form an adhesive layer on a substrate, to produce an adhesive sheet for processing a semiconductor wafer,
The components constituting the pressure-sensitive adhesive layer are used directly or as a solution with an appropriate organic solvent, coated on a substrate by coating or spraying, and dried by heat treatment at 80 to 100 ° C. for about 30 seconds to 10 minutes, for example. Can be obtained.
Alternatively, it can also be obtained by coating and drying a peelable film and then laminating the substrate to an adhesive layer.

A known method can be used to use the pressure-sensitive adhesive sheet for processing a semiconductor wafer of the present invention. For example, after the pressure-sensitive adhesive sheet for processing a semiconductor wafer is attached to a semiconductor wafer and fixed, the semiconductor wafer is rotated with a rotary round blade. Is cut into element pieces (hereinafter referred to as chips). Thereafter, ultraviolet rays and / or an electron beam are irradiated from the substrate side of the pressure-sensitive adhesive sheet for processing,
Then, using a dedicated jig, the wafer processing adhesive sheet is radially expanded and the interval between the chips is expanded at a constant interval.Then, the chips are pushed up with a needle or the like, and are picked up by a method such as suction using a vacuum collet, air tweezers or the like. Just mount it.

[0019]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. Example 1 50 parts by weight of 2-ethylhexyl acrylate and 10 parts by weight of butyl acrylate as base polymers,
Weight average molecular weight 5 obtained by copolymerizing 37 parts by weight of vinyl acetate and 3 parts by weight of 2-hydroxyethyl methacrylate
With respect to 100 parts by weight of the 00000 copolymer, 35 parts by weight and 65 parts by weight of a bifunctional urethane acrylate having a molecular weight of 11,000 and a pentafunctional acrylate monomer having a molecular weight of 500 as a radiation polymerizable compound were respectively 35 parts by weight, and 2 parts by weight as a photopolymerization initiator. 8.3 parts by weight of 2-dimethoxy-2-phenylacetophenone per 100 parts by weight of the radioactive polymer compound, and an acrylic copolymer 1 containing a polyisocyanate-based crosslinking agent
A resin solution for forming the pressure-sensitive adhesive layer, in which 6 parts by weight was blended with respect to 00 parts by weight, was applied to a release-treated polyester film having a thickness of 38 μm so that the thickness after drying became 10 μm. Dried for minutes. Then, as a substrate, a thickness of 8
A 0 μm polyvinyl chloride (PVC) film was laminated to produce an adhesive sheet for semiconductor processing. After the obtained pressure-sensitive adhesive sheet for semiconductor processing is matured at room temperature for 7 days or more, JIS
Samples for measuring adhesive strength and cohesive strength were prepared according to Z0237, and each item was evaluated. Table 1 shows the results.

Example 2 A sample was prepared in the same manner as in Example 1 except that the molecular weight of the urethane acrylate used in Example 1 was 6,000, and the same items as in Example 1 were tested. Table 1 shows the results. Example 3 A sample was prepared in the same manner as in Example 1 except that urethane acrylate was 20 parts by weight and acrylate monomer was 80 parts by weight based on 100 parts by weight of the acrylic copolymer. Similar items were tested. Table 1 shows the results. Example 4 A sample was prepared in the same manner as in Example 1 except that the urethane acrylate was 63 parts by weight and the acrylate monomer was 117 parts by weight based on 100 parts by weight of the acrylic copolymer. Similar items were tested. Table 1 shows the results.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that the molecular weight of the urethane acrylate used in Example 1 was 3000, and the same items as in Example 1 were tested. Table 2 shows the results. Comparative Example 2 A sample was prepared in the same manner as in Example 1 except that urethane acrylate was 5 parts by weight and acrylate monomer was 95 parts by weight based on 100 parts by weight of the acrylic copolymer. Similar items were tested. Table 2 shows the results. << Comparative Example 3 >> A sample was prepared in the same manner as in Example 1 except that the urethane acrylate was 105 parts by weight and the acrylate monomer was 195 parts by weight based on 100 parts by weight of the acrylic copolymer. Similar items were tested. Table 2 shows the results. Comparative Example 4 A sample was prepared in the same manner as in Example 1 except that urethane acrylate was 7 parts by weight and acrylate monomer was 13 parts by weight based on 100 parts by weight of the acrylic copolymer. Similar items were tested. Table 2 shows the results.

[0022]

[Table 1]

[0023]

[Table 2]

The following evaluation methods were used to evaluate the examples and comparative examples. -Initial adhesive strength (before UV irradiation) A 25 mm x 250 mm measuring sheet is prepared from the adhesive sheet for semiconductor processing, and a 2 kg rubber roll is reciprocated on the silicon wafer by one reciprocation under an environment of 23 ° C and 50% humidity. After standing for 20 minutes or more, peeling was performed at 180 ° at a tensile speed of 300 mm / min, and the adhesive strength was measured. -Adhesion after UV irradiation The sample prepared by the above method was irradiated with ultraviolet rays from a distance of 10 cm from the substrate surface using a high-pressure mercury lamp of 80 W / cm for 15 seconds to cure the pressure-sensitive adhesive layer. The adhesive strength was measured in the same manner.・ Holding force A 25 mm × 75 mm measuring sheet is prepared from the adhesive sheet for semiconductor processing, and the sheet is bonded to a stainless steel plate in an environment of 23 ° C. and 50% humidity so that the bonding area becomes 25 mm × 25 mm.
The rubber roll of kg is reciprocated once and pressed. After standing for 20 minutes or more, the sample was placed in a constant temperature bath at 40 ° C., and after a further 20 minutes, a load of 1 kg was applied in the shearing direction, and the displacement after 1 hour was measured. -Chipping characteristics A semiconductor wafer is held and fixed on an adhesive sheet, and the number of spindle rotations is 3 using a dicing saw (DISCO DAD-2H6M).
000rpm, cutting speed 120mm /
After cutting to a chip size in min, the chip was peeled off from the adhesive sheet, and the chipped state on the back surface was evaluated by observing with a stereoscopic microscope.

[0025]

The sheet for processing a semiconductor wafer according to the present invention comprises:
It has sufficient adhesion and cohesion before irradiation with ultraviolet rays and / or electron beams, is excellent in preventing chipping and chip scattering at the time of dicing, and lowers adhesion to the optimal value for picking up after irradiation. This enables stable pickup.

Claims (2)

[Claims] 1. A semiconductor wafer processing method comprising forming a pressure-sensitive adhesive layer containing a base polymer, a radiation-polymerizable compound and a radiation-polymerizable polymerization initiator on a surface of a substrate having transparency to ultraviolet rays and / or electron beams. In the adhesive sheet, the adhesive strength to the semiconductor wafer is 50 to 500 g / 25 mm before irradiation with ultraviolet rays and / or electron beams, and 5 to 40 g / 25 after irradiation.
A pressure-sensitive adhesive sheet for processing a semiconductor wafer, wherein the pressure-sensitive adhesive sheet has a thickness of 25 mm and a distance of displacement after 3600 seconds in JISZ0237 of 5 mm or less according to JISZ0237. 2. The radiation-polymerizable compound is used in an amount of 50 to 200 parts by weight based on 100 parts by weight of the base polymer.
The pressure-sensitive adhesive sheet for processing a semiconductor wafer according to claim 1, comprising 0.03 to 22.5 parts by weight of a radiation-polymerizable polymerization initiator.