TWI490303B - Wafer adhesive tape and wafer processing methods - Google Patents

Description

Wafer bonding adhesive sheet and wafer processing method

The present invention relates to an adhesive sheet for wafer bonding and a method of processing a wafer. More specifically, the present invention relates to a method for processing a wafer-attaching adhesive sheet and a wafer capable of reducing chips or cracks (hereinafter referred to as chips) generated when a semiconductor wafer is cut into small pieces.

In the manufacturing process of a semiconductor device such as an IC or an LSI, after the semiconductor wafer such as germanium or gallium arsenide is cut (separated) into small pieces, the process proceeds to a pick-up step. The cutting step and the picking step of a general semiconductor wafer will be described with reference to the cross-sectional views shown in FIGS. 2 to 5.

First, the adhesive wafer 12 is fixed on the holder 11 at both ends and coated with an adhesive on the base film, and the semiconductor wafer 13 is adhered (refer to FIG. 2), and the wafer is divided into small pieces by cutting. ) 14 (refer to Figure 3). Then, in order to pick up the wafer 14, the dilator 16 is topped in the direction of the solid arrow 15 and then expanded in the direction of the dotted arrow 17 to enlarge the interval between the wafers 14 (refer to FIG. 4), and the entire wafer 14 or a portion of the wafer 14 is picked up. (Refer to Figure 5). 2 to 5, the same reference numerals denote the same elements, and the related description of the partial drawings is omitted here.

Previously, in the process from the cutting step to the pick-up step of the semiconductor wafer, an adhesive sheet coated with an adhesive on the substrate film was used. In the case of such an adhesive sheet, a substrate composed of a softer resin is used in consideration of expandability. For example, a polyvinyl chloride film or a polyethylene film is sometimes used.

When cutting, fragments and cracks of the wafer called chips are generated. It is not uncommon for the size to be 100 μm or more. If the debris reaches the circuit surface, it sometimes affects the performance of the circuit itself. Moreover, at the time of the picking step, fragments of the wafer which are sometimes generated by the debris may adhere to the surface of the other wafer and break the circuit.

The chips are generated in such a manner that a rotating blade called a blade during cutting causes vibration of the wafer during cutting, and the wafer is brought into contact with the blade to generate the above-mentioned debris. Therefore, there is also a method of using a wax instead of an adhesive sheet to completely fix the wafer to avoid vibration. However, in the case where the reverse cutting is performed as in the manufacturing step, it is not practical to use the fixing and removal of the wax, which is troublesome. Moreover, since the wax remains in the case where the wax cannot be completely removed, the wafer is contaminated, and thus it is difficult to apply it in an electronic device that is extremely resistant to pollutants.

An object of the present invention is to provide an adhesive sheet for wafer bonding which can be manufactured at low cost and which can reduce debris generated during dicing. Further, an object of the present invention is to provide a method of processing a wafer which can reduce the generation of debris generated during cutting.

As a result of intensive research on the above-mentioned problems, the present inventors have found that the above problem can be solved by making the adhesive sheet for wafer adhesion have a specific loss coefficient. The present invention has been completed based on this finding.

That is, the following method is provided in accordance with the present invention:

(1) An adhesive sheet for wafer bonding, comprising a base film and an adhesive layer formed on the base film, wherein the adhesive sheet is processed into a test piece having a width of 7 mm by using The loss coefficient (23 ° C, frequency 1 to 100 Hz) measured by the dynamic viscoelasticity measuring device in the film form is 0.15 or more;

(2) The adhesive sheet for wafer bonding according to the above item (1), wherein at least one of the layers constituting the base film contains styrene-hydrogenated isoprene-styrene block copolymer, styrene- Isoprene-styrene copolymer, styrene-hydrogenated butadiene-styrene copolymer or styrene-hydrogenated isoprene/butadiene-styrene copolymer;

(3) The adhesive sheet for wafer bonding according to the above item (2), wherein at least one of the layers constituting the base film is made of styrene-hydrogenated isoprene-styrene block copolymer, styrene a mixture of isoprene-styrene copolymer, styrene-hydrogenated butadiene-styrene copolymer, or a mixture of styrene-hydrogenated isoprene/butadiene-styrene copolymer and polypropylene;

(4) The adhesive sheet for wafer bonding according to the above item (2) or (3), wherein the styrene-hydrogenated isoprene-styrene block copolymer, styrene-different in the base film The content of the pentadiene-styrene copolymer, the styrene-hydrogenated butadiene-styrene copolymer, or the styrene-hydrogenated isoprene/butadiene-styrene copolymer is 10 to 75% by mass;

(5) The adhesive sheet for wafer bonding according to any one of (1) to (4), wherein the adhesive layer forming the adhesive layer is an acrylic adhesive;

(6) A method of processing a wafer, comprising the step of bonding a wafer to the adhesive sheet for wafer bonding according to any one of (1) to (5) above, and the wafer The cutting step, and the slit in the cutting step does not reach the substrate film of the adhesive sheet for wafer bonding.

Further, the above "styrene-hydrogenated isoprene/butadiene-styrene copolymer" means "styrene-hydrogenated isoprene-hydrogenated butadiene-styrene copolymer".

The above and other features and advantages of the present invention will become more apparent from the appended claims.

Fig. 1 is a schematic cross-sectional view showing a preferred embodiment of the adhesive sheet for wafer bonding of the present invention, comprising a base film 1 and an adhesive layer 2 formed on the base film 1. In the present invention, the adhesive sheet contains an adhesive tape (for example, a dicing tape). In the adhesive sheet for wafer bonding of the present invention, a test piece processed to a width of 7 mm is used, and a loss factor (23 ° C, frequency: 1 to 100 Hz) measured by a dynamic viscoelasticity measuring device is 0.15 or more.

In the present specification, the loss factor (tan δ) is a ratio (G'/G") between the shear elastic modulus (G') and the loss shear modulus (G"). The loss factor is measured in the following manner according to the central support fixed vibration method (central vibration method) described in JIS G 0602 "Testing method for vibration damping characteristics of vibration-damping steel sheets". Using a dynamic viscoelasticity measuring device (ARES manufactured by Rheometric Co., Ltd.), and using a film measuring tool, the adhesive sheet was processed into a width of 7 mm to prepare a test piece, which was then fixed to a supporting jig at a measuring temperature of 23 ° C and a measuring frequency of The loss factor is calculated according to the attenuation method or the half-band width method described in JIS G 0602 "Testing method for vibration damping characteristics of vibration-damping steel sheets" under the condition of 1 to 100 Hz. The length of the test piece can be 60 mm or more.

The debris is caused by the rotating blade called the blade when cutting. As a result of intensive studies, the inventors of the present invention have found that the chips are generated in such a manner that the wafer is in contact with the blades by the rotation of the wafer during the cutting, thereby generating the above-mentioned debris. However, since the adhesive sheet for wafer bonding of the present invention has vibration damping property, the vibration of the wafer generated at the time of cutting can be attenuated, thereby preventing chipping. The loss factor of the adhesive sheet for wafer bonding is 0.15 or more, preferably 0.20 or more. If the loss factor is less than 0.15, the vibration generated by the cutting blade cannot be reduced, resulting in an increase in the generation of debris.

The loss coefficient (tan δ) of the adhesive sheet for wafer bonding is preferably 0.15 or more and 0.40 or less, more preferably 0.20 or more and 0.40 or less, and particularly preferably 0.20 or more and 0.30 or less. Here, if the loss coefficient (tan δ) of the adhesive sheet for wafer adhesion is too large, the recovery property after the tape is expanded may be lowered, and if it is 0.30 or less, more recovery property can be obtained, which is preferable.

The base film 1 is not particularly limited, and is preferably a styrene-hydrogenated isoprene-styrene block copolymer (styrene-ethylene-propylene-styrene block copolymer, hereinafter referred to as "SEPS"). , styrene-isoprene-styrene copolymer (hereinafter referred to as "SIS"), styrene-hydrogenated butadiene-styrene copolymer (hereinafter referred to as "SEBS") or styrene-hydrogenated isoprene One of the olefin/butadiene-styrene copolymer (hereinafter referred to as "SEEPS") or a mixture of any of these and other resins.

The base film 1 is excellent in water resistance and heat resistance, and is particularly suitable for a synthetic resin film. If a film that can be stretched is inserted, it becomes easy to expand. The resin, in particular, in addition to the above-mentioned SEPS, SIS, SEBS, SEEPS, may also be exemplified by polypropylene, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-propylene copolymerization. , propylene copolymer, ethylene-propylene-diene copolymer sulfide, polybutene, polybutadiene, polymethylpentene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, Ethylene-methyl (meth) acrylate copolymer, ethylene-ethyl (meth) acrylate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl chloride-vinyl acetate copolymer, polyamine Carbamate, polyamide, ionic polymer, nitrile rubber, butyl rubber, styrene isoprene rubber, styrene butadiene rubber, natural rubber and its hydride or modified substance.

The stretchable film composed of these resins may be used in combination of two or more kinds or a combination of layers. When the substrate film is composed of a plurality of layers, it is preferred that at least one layer contains SEPS, SIS, SEBS or SEEPS, and more preferably at least one of the above layers is composed of a mixture of SEPS, SIS, SEBS or SEEPS and polypropylene. .

The blending amount of SEPS, SIS, SEBS or SEEPS in the present invention can be appropriately selected according to the degree of vibration damping required, and can be appropriately determined in consideration of the balance between the film strength and the vibration damping property, for example, every 100 parts by mass. The base polymer constituting the base film can be selected from 10 to 75 parts by mass, and more preferably from 15 to 60 parts by mass. If the content of SEPS, SIS, SEBS or SEEPS in the present invention is too small, sufficient vibration damping properties may not be obtained, and the chip suppressing effect may be small. Moreover, if the content of SEPS, SIS, SEBS or SEEPS is too large, the film itself may become too soft, resulting in deterioration of the treatment.

Further, the resin used in combination with SEPS, SIS, SEBS or SEEPS in the layer constituting the base film is not limited thereto, but is preferably polypropylene. When the base polymer constituting the base film is formed by blending SEPS, SIS, SEBS or SEEPS with polypropylene, the content of the polypropylene may be set to 90 to 25 parts by mass, preferably 85 to 40 parts by mass.

In order to improve the adhesion to the surface of the base film 1 which is in contact with the adhesive layer 2, another layer such as a corona treatment or a primer may be applied. The thickness of the base film 1 is not particularly limited, but is preferably 30 to 200 μm, and particularly preferably 50 to 100 μm.

Further, when the base film 1 is composed of a plurality of layers, the thickness of the layer containing the SEPS, SIS, SEBS or SEEPS is preferably 5 to 100 μm.

The adhesive layer 2 can be formed from various adhesives previously known. The adhesive is not limited, and for example, an adhesive such as a rubber-based, acrylic-based, anthrone-based or polyvinyl ether-based polymer can be used.

In order to apply cohesive force to the base polymers, a crosslinking agent can be formulated.

The crosslinking agent may, for example, be an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, an aziridine crosslinking agent, or an amine resin, depending on the base polymer. Further, various additives may be contained in the adhesive as needed.

Further, a radiation hardening type or a heat foaming type adhesive can also be used. As the radiation-curing type adhesive, an adhesive which is hardened by ultraviolet rays, an electron beam or the like to be easily peeled off during peeling can be used. As the heat-expandable adhesive, an adhesive which is easily peeled off by a foaming agent or a bulking agent by heating can be used. Moreover, the adhesive can also be an adhesive for cutting and bonding. For example, the radiation-hardening type adhesive is preferably used, for example, in Japanese Patent Publication No. Hei 1-56612, Japanese Patent Application Laid-Open No. Hei No. Hei No. Hei. In the present invention, it is preferred to use an ultraviolet curable adhesive. In this case, as long as it is cured by irradiation, it has a property of three-dimensional network, and for example, at least 2 of the blending molecules of a general rubber-based or acrylic-based pressure-sensitive base resin (polymer) can be used. A low molecular weight compound (hereinafter referred to as a photopolymerizable compound) and a photopolymerization initiator which are photopolymerizable carbon-carbon double bonds.

As the rubber-based or acrylic-based base resin, a rubber-based polymer such as natural rubber or various synthetic rubbers, or a polyalkyl (meth)acrylate, an alkyl (meth)acrylate, or (meth)acrylic acid can be used. An acrylic polymer such as a copolymer obtained from an alkyl ester and another unsaturated monomer copolymerizable therewith.

Further, in the above-mentioned adhesive, by mixing an isocyanate-based curing agent, the initial adhesion can be set to an arbitrary value. As the hardener, specifically, a polyisocyanate compound such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-benzenedimethyl diisocyanate, or 1,4-benzenedimethyldi can be used. Isocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, dihexyl diisocyanate, isophor Keto diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, isocyanuric acid isocyanate, and the like.

In the case of the ultraviolet curable adhesive, the polymerization hardening time and the ultraviolet irradiation amount of the ultraviolet irradiation can be reduced by mixing the photopolymerization initiator into the adhesive.

The photopolymerization initiator may, for example, be benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, Diphenylene oxime, diacetyl cellulose, β-chloropurine, and the like.

The thickness of the adhesive layer 2 is not particularly limited, but is preferably 4 to 30 μm, and particularly preferably 5 to 25 μm.

The wafer is bonded to the adhesive sheet for wafer bonding of the present invention, and the wafers shown in FIGS. 2 to 5 can be cut and picked up in accordance with a general method. In the method of processing a wafer using the adhesive sheet for wafer bonding of the present invention, the slit does not reach the substrate film, whereby the cutting resistance of the cutting blade can be reduced, and wafer cutting can be smoothly performed, thereby reducing chipping. Therefore, it is better. In order to prevent the slit from reaching the base film, for example, the setting of the slit depth of the cutting device to be used can be appropriately changed manually.

The bare wafer used in the present invention is not particularly limited, and may be appropriately selected from any of the bare wafers previously used.

According to the method for processing a wafer adhesive for a wafer and a wafer, the chip can be greatly reduced in processing of the wafer.

[Examples]

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

Further, the adhesives and base material constituting resins used in the examples and the comparative examples are as follows.

(adhesive)

Acrylic base polymer (copolymer composed of 2-ethylhexyl acrylate, methyl acrylate, 2-hydroxyethyl acrylate, weight average molecular weight 200,000, glass transition point = -35 ° C) 100 parts by mass 3 parts by mass of a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., trade name: CORONATE L), 10 parts by mass of tetramethylol methane tetraacrylate as a compound containing a photopolymerizable carbon-carbon double bond, and a photopolymerization initiator 1 part by mass of α-hydroxycyclohexyl phenyl ketone was obtained by mixing.

[Examples 1 to 3, Comparative Example 1]

Styrene-hydrogenated isoprene-styrene block copolymer (SEPS) ("SEPTON KF-2104", manufactured by Kuraray Co., Ltd.) and homopropylene (PP) were used in the blending ratio shown in Table 1. (J-105G, manufactured by Ube Industries, Ltd.) was mixed and processed by film extrusion at about 200 ° C using a biaxial kneader to produce a substrate film having a thickness of 100 μm.

On the surface of one of the obtained base films, the adhesive was applied to a thickness of 10 μm to form an adhesive layer, and the adhesive sheets for wafer bonding of Examples 1 to 3 and Comparative Example 1 were produced.

[Examples 4 to 6]

In place of the above styrene-hydrogenated isoprene-styrene block copolymer (SEPS), the following copolymers were each mixed in the blending ratio shown in Table 1, except that the same procedure as in Example 1 was carried out. Adhesive sheets for wafer bonding.

Styrene-isoprene-styrene copolymer (SIS)

(Kuraray company, trade name: HYBRAR5127)

Styrene-hydrogenated butadiene-styrene copolymer (SEBS)

(Kuraray company, trade name: SEPTON8104)

Styrene-hydrogenated isoprene/butadiene-styrene copolymer (SEEPS)

(Kuraray company, trade name: SEPTON4033)

A wafer having a diameter of 6 inches and a thickness of 350 μm was deposited on the surface of the wafer for bonding the wafers of Examples 1 to 6 and Comparative Example 1, and a cutting device (DAD-340, manufactured by DISCO Corporation) was used. The wafer was cut to a size of 5 mm square. The cutting conditions were: rotating circular knife rotation speed: 40000 rpm, cutting speed: 100 mm/s, and cutting water flow rate of 20 mL. Further, when cutting, the rotary cutter was cut into the adhesive sheet to have a slit depth of 30 μm.

A number of characteristics were evaluated as follows, and the results are shown in Table 1.

(loss factor)

The sheets of the examples and the comparative examples were processed into test pieces having a width of 7 mm and a length of 60 mm by a dynamic viscoelasticity measuring device (ARES, manufactured by Rheometric Co., Ltd.), and fixed on a supporting jig (clamp). . The measurement was carried out under the conditions of a measurement temperature of 23 ° C and a measurement frequency of 1 to 100 Hz, and the loss coefficient was calculated based on the central vibration method of JIS G 0602 "Test method for vibration damping characteristics of vibration-damping steel sheets".

Further, the above measurement was carried out by generating a tensile load and a displacement by converting the rotational force into a tensile force under the conditions of an initial load of 200 g and a strain of 1%.

(debris)

After the dicing, UV irradiation (500 mJ/m ² ) was carried out, 50 wafers were randomly taken out from one wafer, and the maximum debris value on each side of the back surface (adhesive surface) of the wafer was measured with a microscope (100 to 200 times). And calculate the average of all values.

As shown in Table 1, the sheets of Examples 1 to 6 were able to significantly reduce the chip value to 1/3 or less as compared with the sheet of Comparative Example 1, and showed good performance.

[Industrial availability]

The adhesive sheet for wafer bonding of the present invention can be manufactured at low cost and has less debris generated during cutting. Therefore, the adhesive sheet for wafer bonding of the present invention can be suitably applied to the manufacture of a semiconductor device or the like.

The present invention has been described above with respect to the embodiments thereof, and the present invention is not limited to the details of the present invention, and is not intended to limit the scope of the present application. The scope and scope of the invention should be interpreted to the fullest extent.

The present invention is based on the priority of the Japanese Patent Application No. 2008-306587, the entire disclosure of which is hereby incorporated by reference.

1‧‧‧Base film

2‧‧‧Adhesive layer

11‧‧‧ Keeper

12‧‧‧Adhesive tablets

13‧‧‧Semiconductor wafer

14‧‧‧Small

15‧‧‧solid arrow direction

16‧‧‧Expander

17‧‧‧dotted arrow

Fig. 1 is a cross-sectional view showing an embodiment of an adhesive sheet of the present invention.

2 is a cross-sectional view showing a cutting step and a picking step of a semiconductor wafer.

3 is a cross-sectional view showing a cutting step and a picking step of a semiconductor wafer.

4 is a cross-sectional view showing a cutting step and a picking step of a semiconductor wafer.

Figure 5 is a cross-sectional view showing a cutting step and a picking step of a semiconductor wafer.

1. . . Substrate film

2. . . Adhesive layer

Claims (5)

The adhesive sheet for wafer adhesion is composed of a base film and an adhesive layer formed on the base film, and is characterized in that the adhesive sheet is processed into a test piece having a width of 7 mm by dynamic adhesion. The loss measuring coefficient (23 ° C, frequency 1 to 100 Hz) measured by the elastic measuring device in the film form is 0.15 or more and 0.40 or less, and the layer constituting the base film is one layer, and the layer is composed of styrene-hydrogenated isoprene. Alkene-styrene block copolymer, styrene-isoprene-styrene copolymer, styrene-hydrogenated butadiene-styrene copolymer or styrene-hydrogenated isoprene/butadiene-styrene The copolymer is composed of a mixture of 40 to 65 parts by mass of a resin, wherein the resin is polypropylene or low density polyethylene per 100 parts by mass of the base polymer constituting the substrate film. LDPE), linear low density polyethylene (LLDPE), ethylene-propylene copolymer, propylene copolymer, ethylene-propylene-diene copolymer sulfide, polybutene, polybutadiene, polymethylpentene, ethylene -vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-methyl (meth)acrylate Polymer, ethylene-ethyl (meth) acrylate copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl chloride-vinyl acetate copolymer, styrene, polyurethane, poly Indoleamine, ionic polymer, nitrile rubber, butyl rubber, styrene isoprene rubber, styrene butadiene rubber, natural rubber and its hydride or modified substance. The adhesive sheet for wafer bonding according to claim 1, wherein the resin is polypropylene. For example, the adhesive sheet for wafer bonding according to item 1 of the patent application, wherein The adhesive forming the adhesive layer is an acrylic adhesive. The adhesive sheet for wafer bonding according to the second aspect of the invention, wherein the adhesive forming the adhesive layer is an acrylic adhesive. A wafer processing method in which a wafer is bonded to a wafer adhesive sheet according to any one of claims 1 to 4, and the wafer is cut, and the slit does not reach the substrate film.