JP2000281993A - Adhesive sheet for semiconductor wafer processing - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To exhibit excellent adhesion to semiconductor wafers,
To provide a pressure-sensitive adhesive sheet for processing a semiconductor wafer which has excellent chipping resistance and has little adhesive residue on a wafer after ultraviolet irradiation peeling. SOLUTION: The pressure-sensitive adhesive for processing a semiconductor wafer is obtained by applying a pressure-sensitive adhesive layer comprising a base polymer, a radiation-polymerizable compound and a radiation-polymerizable polymerization initiator on a substrate surface having transparency to ultraviolet rays and / or electron beams. In the sheet, the pressure-sensitive adhesive layer contains 5 to 50 parts by weight of a radiation polymerizable compound having 5 to 6 acryloyl groups based on 100 parts by weight of the base polymer, and has a holding power of 3 in JISZ0237.
The displacement distance after 600 seconds is 5 mm or less, and the gel fraction after ultraviolet irradiation and / or electron beam irradiation is 90 wt.
% Or more.

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 coated with 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 that a photopolymerizable compound constituting the pressure-sensitive adhesive layer contains, in a molecule such as trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate, or oligoester acrylate, an ultraviolet and / or electron beam polymerizable compound. 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] Further, at present, the ultraviolet conditions for polymerizing these photopolymerizable compounds are often performed at a low illuminance with an integrated light amount of 50 mJ or less, and the polymerization reaction after the ultraviolet irradiation becomes insufficient. There is a problem in that the pressure-sensitive adhesive layer is transferred to the wafer (adhesive residue).

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an adhesive for processing semiconductor wafers which exhibits excellent adhesive strength to a semiconductor wafer, has excellent chipping resistance, and has little adhesive residue on the wafer after peeling off by ultraviolet irradiation. To provide a seat.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to ultraviolet and / or ultraviolet radiation.
Or in a pressure-sensitive adhesive sheet for processing semiconductor wafers obtained by applying a pressure-sensitive adhesive layer comprising a base polymer, a radiation-polymerizable compound and a radiation-polymerizable polymerization initiator on a substrate surface having transparency to an electron beam, the pressure-sensitive adhesive layer is Based on 100 parts by weight of the base polymer, 5 to 50 parts by weight of a radiation-polymerizable compound having 5 to 6 acryloyl groups is contained, and the distance of deviation after 3600 seconds in JISZ0237 is 5 mm or less, In addition, the adhesive sheet for processing a semiconductor wafer has a gel fraction of 90 wt% or more after ultraviolet irradiation and / or electron beam irradiation. Here, the gel fraction is represented by the weight ratio of the pressure-sensitive adhesive layer before and after immersion in the solvent, and is a measure of the reaction rate of the ultraviolet polymerization reaction. Preferably, the pressure-sensitive adhesive sheet for processing a semiconductor wafer has a molar extinction coefficient of the radiation polymerization polymerization initiator in the range of 1,000 to 20,000 (1 / mol · cm) at a wavelength of 280 to 340 nm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a pressure-sensitive adhesive layer provided on a substrate may be subjected to a polymerization and curing reaction by ultraviolet rays and / or an electron beam. And the cohesive force of the pressure-sensitive adhesive layer is 3 in JISZ0237.
The displacement distance after 600 seconds is 5 mm or less (preferably 3 m
m or less, and preferably 1 mm or less), so that the chip is less likely to be displaced or lifted during dicing. As a result, chipping (chip chipping) and chip fly hardly occur.
Irradiation with ultraviolet rays and / or an electron beam causes a polymerization and curing reaction, and the plastic fluidity is reduced, so that the adhesive strength is reduced and the chip can be easily picked up. Furthermore,
Since it has a certain degree of elongation at break even after curing, it is possible to prevent cracking of the pressure-sensitive adhesive layer at the time of expanding, and to maintain uniform alignment of chip intervals. The gel fraction after UV irradiation and / or electron beam irradiation is 90 wt.
% Or more, and the adhesive residue on the wafer after ultraviolet irradiation peeling is small.

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,
Examples include polyurethane, ethylene-vinyl acetate copolymer, ethylene-hexene copolymer, ethylene-butene copolymer, and ethylene-propylene-butene copolymer.

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 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 has a reduced adhesive strength after the curing reaction, and It is necessary to easily pick up (chips) and to maintain a high cohesive force. For this purpose, it is preferably 5000 or more, more preferably 8000 or more, and most preferably 10 or more.
It is preferable to mix a polyfunctional urethane acrylate having a molecular weight of 000 or more and preferably a polyfunctional acrylate monomer having a molecular weight of 1000 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 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. 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, and hexanediol. Examples of the hydroxy (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and the like.

The polyfunctional acrylate monomer used in the present invention includes, for example, trimethylolpropane triacrylate, pentaerythritol triacrylate,
Pentaerythritol tetrahydroxyacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate and the like can be mentioned, but it is necessary to have 5 to 6 functional groups, and dipentaerythritol monohydroxypentaacrylate or dipentaerythritol monohydroxypentaacrylate Erythritol hexaacrylate is preferred. If it is less than 4 functional groups, the crosslink density after the reaction is insufficient, the gel fraction is low, and as a result, glue residue occurs, which is not preferable. It is difficult to synthesize more than 7 functions. It is necessary that the compounding amount of the polyfunctional acrylate monomer having 5 to 6 acryloyl groups is 5 to 50 parts by weight based on 100 parts by weight of the base polymer. If the amount is less than 5 parts by weight, the crosslinking density after ultraviolet irradiation is insufficient, and the gel fraction is low. As a result, adhesive residue is not preferable, and if it exceeds 50 parts by weight, there is no adhesive residue after ultraviolet irradiation. However, the cohesive force of the pressure-sensitive adhesive layer is low, and chipping often occurs, which is not preferable.

The weight ratio of the bifunctional urethane acrylate of the radiation polymerizable compound to the 5- to 6-functional acrylate monomer is preferably in the range of 10:90 to 90:10, more preferably in the range of 30:70 to 70:30. It is. 5-
If the weight ratio of the 6-functional urethane acrylate is less than 10, the cohesive strength of the pressure-sensitive adhesive layer is insufficient, and if it exceeds 90, there is a problem that the adhesive strength after curing is not sufficiently reduced and the chip becomes difficult to pick up. The mixing ratio of the radiation polymerizable compound is 50 to 2 with respect to 100 parts by weight of the base polymer.
00 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. .

The radiation polymerization polymerization initiator used in the present invention preferably has a molar extinction coefficient in the range of 1,000 to 20,000 (1 / mol · cm) at a wavelength of 280 to 340 nm. When it is less than 1000 (1 / mol · cm), the curing reaction of the radiation-polymerizable compound in ultraviolet irradiation and / or electron beam irradiation becomes poor and causes adhesive residue, and when it exceeds 20,000 (1 / mol · cm), heat or It is not preferable because the stability under a fluorescent lamp is deteriorated. The mixing ratio of the radiation-polymerizable polymerization initiator is preferably 0.03 to 22.5 parts by weight based on the radiation-polymerizable polymer compound.
If the amount is less than 0.03 parts by weight, the curing reaction of the radiation-polymerizable compound upon irradiation with ultraviolet rays and / or electron beams becomes poor, and the decrease in adhesive strength becomes insufficient. If it exceeds 22.5 parts by weight, the reaction is accelerated. This is not preferred because a large amount of short-chain components of the radiation-polymerizable polymer compound is generated during the reaction, causing adhesive residue.

In the present invention, the thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 to 35 μm. In the present invention, in order to form an adhesive layer on a base material and produce an adhesive paper for processing a semiconductor wafer, the components constituting the adhesive layer are used as they are or in a solution with an appropriate organic solvent, and then applied or sprayed. It can be obtained by applying the composition on a base material by, for example, drying at 80 to 100 ° C. for 30 seconds to 10 minutes.

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.

[0020]

EXAMPLES 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. Example 1 A copolymer having a weight average molecular weight of 500,000 obtained by copolymerizing 50 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of butyl acrylate, 37 parts by weight of vinyl acetate, and 3 parts by weight of 2-hydroxyethyl methacrylate. Bifunctional urethane acrylate 3 having a molecular weight of 11,000 was used as a radiation polymerizable compound with respect to 100 parts by weight of the acrylic copolymer.
5 parts by weight, and a pentafunctional acrylate monomer (dipentaerythritol monohydroxypentaacrylate) 3
5 parts by weight, 2-benzyl-2-dimethylamino-1- (4-morphonylphenyl) -butanone as a photopolymerization initiator [molar extinction coefficient (340 nm): 10000 (1 / mol ·
cm)] to 100 parts by weight of the radioactive polymerized compound.
3 parts by weight, a resin solution containing 6 parts by weight of a polyisocyanate-based cross-linking agent with respect to 100 parts by weight of the acrylic copolymer, and a 38 μm-thick polyester film having been subjected to a peeling treatment, having a thickness of 10 μm after drying. Coated as above, 80
C. and dried for 5 minutes. Thereafter, a polyvinyl chloride (PVC) film having a thickness of 80 μm was laminated as a base material to produce an adhesive sheet for semiconductor processing. The obtained pressure-sensitive adhesive sheet for semiconductor processing is matured at room temperature for 7 days or more, and then subjected to JIS Z-0.
Samples for measuring adhesive strength and cohesive strength were prepared according to 237, and each item was evaluated. Table 1 shows the results.
Shown in

Example 2 A sample was prepared in the same manner as in Example 1 except that the molecular weight of the bifunctional urethane acrylate used in Example 1 was 6,000, and the same items as in Example 1 were tested. did. Table 1 shows the results. Example 3 The photoinitiator used in Example 1 was 1 part by weight.
A sample was prepared in the same manner as in Example 1 except that it was part by weight, and the same items as in Example 1 were tested. Table 1 shows the results. Example 4 The photoinitiator used in Example 1 was 2-methyl-
1- (4-methylthiophenyl) -2-morpholinopropane [molar extinction coefficient (340 nm): 2000 (1 / mol ·
cm)], a sample was prepared in the same manner as in Example 1, and the same items as in Example 1 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 bifunctional urethane acrylate used in Example 1 was 3000, and the same items as in Example 1 were tested. did. Table 1 shows the results. Comparative Example 2 A sample was prepared in the same manner as in Example 1 except that bifunctional urethane acrylate was 5 parts by weight and pentafunctional acrylate monomer was 95 parts by weight based on 100 parts by weight of the acrylic copolymer. The same items as in Example 1 were tested. Table 1 shows the results. << Comparative Example 3 >> A sample was prepared in the same manner as in Example 1 except that the number of parts by weight of the photoinitiator used in Example 1 was 0.01 polymerization part. Tested. Table 1 shows the results. << Comparative Example 4 >> The photoinitiator used in Example 1 was 2,2-dimethoxy-2-phenylacetophenone [molar extinction coefficient (34
0 nm): 100 (1 / mol · cm)], except that the sample was prepared in the same manner as in Example 1, and the same items as in Example 1 were tested. Table 1 shows the results.

[0023]

[Table 1]

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 is irradiated with ultraviolet rays from a distance of 10 cm from the substrate surface using a high-pressure mercury lamp of 80 W / cm so that the integrated light quantity becomes 50 mJ, and the adhesive layer is cured. After that, the adhesive strength was measured in the same manner as described above.・ Holding force A 25 mm × 75 mm measuring sheet is prepared from the semiconductor processing adhesive sheet, and a 2 kg rubber roll is reciprocated once on a stainless steel plate in an environment of 23 ° C. and 50% humidity so that the adhesive area becomes 25 mm × 25 mm. And crimp. 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. -Gel fraction 10 cm x 10 cm of the pressure-sensitive adhesive layer cured as described above
And immersed in a toluene solution for 24 hours, and calculated from the change in weight before and after immersion. Gel fraction (%) = (weight after immersion) / (weight before immersion) × 1
00. Adhesive residue After adhering the adhesive sheet to the mirror surface of the silicon wafer, irradiating with ultraviolet light under the above conditions, the sheet is peeled off, and the surface is left with an optical microscope for adhesive residue (transfer of the adhesive layer to the silicon wafer). Was evaluated. ○: No adhesive residue ×: Adhesive residue

[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. In addition, there is little adhesive residue on the wafer.

Claims (2)

[Claims] 1. A semiconductor wafer processing method comprising applying a pressure-sensitive adhesive layer comprising a base polymer, a radiation-polymerizable compound and a radiation-polymerizable polymerization initiator on a substrate surface having transparency to ultraviolet rays and / or electron beams. In the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer contains 5 to 50 parts by weight of a radiation polymerizable compound having 5 to 6 acryloyl groups based on 100 parts by weight of the base polymer, and has a holding power of 3 in JISZ0237.
The displacement distance after 600 seconds is 5 mm or less, and the gel fraction after ultraviolet irradiation and / or electron beam irradiation is 90 wt.
% Of the adhesive sheet for processing a semiconductor wafer. 2. The radiation polymerization initiator having a molar extinction coefficient of 1,000 to 2,000 at a wavelength of 280 to 340 nm.
The pressure-sensitive adhesive sheet for processing a semiconductor wafer according to claim 1, wherein the pressure-sensitive adhesive sheet has a range of 0 (1 / mol · cm).