JPH0214384B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an adhesive sheet, and more specifically,
The present invention relates to an adhesive sheet used for cutting and separating semiconductor wafers into small pieces.

Technical background of the invention and its problems Semiconductor wafers of silicon, gallium arsenide, etc. are manufactured in a large diameter state, and after this wafer is cut and separated into small element pieces (dicing), it is transferred to the next process, a mounting process. ing. At this time, the semiconductor wafer is previously attached to an adhesive sheet and subjected to the following steps: dicing, cleaning, drying, expanding, picking up, and mounting.

Adhesive sheets used in the dicing process of semiconductor wafers have traditionally been made of a base material made of a general-purpose polymer film such as polyvinyl chloride or polypropylene, with an acrylic or other adhesive layer provided on the surface of the base material. things have been used. However, such an adhesive sheet having an acrylic adhesive layer has a problem in that when each chip of a diced semiconductor wafer is picked up, the adhesive remains on the chip surface and the chips are contaminated. .

In order to solve these problems, conventional methods have been proposed in which the amount of adhesive is reduced by partially applying the adhesive to the base material surface instead of applying it to the entire surface. According to this method, the amount of adhesive relative to the total number of chips is reduced and the contamination of the chip surface by the adhesive can be reduced to some extent, but the adhesive force between the wafer chip and the adhesive sheet is reduced, so it is difficult to use in the dicing process. subsequent cleaning;
A new problem arises in that the wafer tip comes off from the adhesive sheet during the drying and expanding steps.

The adhesive sheet used in the process from the dicing process to the pick-up process for semiconductor wafers has sufficient adhesion to the wafer chip from the dicing process to the expanding process, and has sufficient adhesion to the wafer chip during the pick-up process. It is desired that the adhesive has enough adhesive strength to prevent the agent from adhering.

As such an adhesive sheet, there is a
In Publication No. 196956 and Japanese Unexamined Patent Publication No. 60-223139,
A pressure-sensitive adhesive sheet has been proposed in which a pressure-sensitive adhesive consisting of a low molecular weight compound having at least two or more photopolymerizable carbon-carbon double bonds in the molecule that can be formed into a three-dimensional network by irradiation with light is coated on the base material surface. . According to the publication, low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in the molecule include trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. , dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, and commercially available oligoester acrylates.

Adhesive sheets coated with an adhesive layer made of a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule as exemplified above may have the following problems. Discovered by the present inventors. A semiconductor wafer is dotted onto an adhesive sheet, the wafer is subjected to a dicing process, and the cut and separated wafer chips are then picked up. At this time, the position of the chip is detected by an optical sensor or the like. However, with the adhesive sheet described above, the detection light for the chip position may be reflected by the adhesive sheet, making it impossible to accurately detect the chip position, and malfunctions often occur during pick-up. The present inventors have discovered that there is a problem. In addition, the present inventors have discovered that when the above-mentioned adhesive sheet is irradiated with ultraviolet rays, the adhesive strength temporarily decreases, but the adhesive strength does not decrease to the optimum value, and the larger the chip becomes, the more difficult it is to pick up the adhesive. was discovered by.

The inventors of the present invention made extensive studies to solve the problems associated with such conventional techniques, and found that it is possible to apply a compound that is colored by radiation irradiation to the base material surface, or to
Alternatively, the present invention was completed by discovering that it is sufficient to add a compound that can be colored by radiation irradiation to the base material. We have also discovered that if a urethane acrylate oligomer is used as a photopolymerizable compound, a pressure-sensitive adhesive sheet with extremely excellent properties can be obtained.

Purpose of the Invention The present invention is an attempt to solve the above-mentioned problems associated with the prior art at once. Therefore, there is no malfunction during the positioning process of the wafer chip, and it has sufficient adhesive strength before radiation irradiation, and the adhesive strength decreases sufficiently after radiation irradiation, so that it does not stick to the back surface of the wafer chip. Semiconductor wafers that do not have adhesive attached to them, and that allow workers managing the dicing process to easily determine whether or not the adhesive sheet has been irradiated with radiation, thereby preventing problems in the process. Summary of the Invention The purpose of the invention is to provide a pressure-sensitive adhesive sheet that is particularly preferably used when subjecting to a dicing process. A pressure-sensitive adhesive sheet coated with a pressure-sensitive adhesive layer consisting of the following is characterized in that a compound that is colored by radiation irradiation is coated on at least one of the base material surfaces.

Moreover, the adhesive sheet of the second aspect according to the present invention is
In a pressure-sensitive adhesive sheet formed by coating a pressure-sensitive adhesive layer consisting of a pressure-sensitive adhesive and a radiation-polymerizable compound on a base material surface,
It is characterized by the addition of a compound that can be colored by radiation irradiation into the base material.

In the pressure-sensitive adhesive sheet according to the present invention, a compound that is colored by radiation irradiation is coated on at least one surface of the base material or is added to the base material, so that after the pressure-sensitive adhesive sheet is irradiated with radiation, are colored, so that the detection accuracy is increased when the optical sensor detects the wafer chip, and malfunctions do not occur when picking up the wafer chip. Further, whether or not the adhesive sheet has been irradiated with radiation can be immediately determined by visual inspection. Furthermore, when a urethane acrylate oligomer is used as a radiation-polymerizable compound in the adhesive sheet, a pressure-sensitive adhesive sheet with extremely excellent performance can be obtained.

DETAILED DESCRIPTION OF THE INVENTION The adhesive sheet 1 according to the present invention generally consists of a base material 2 and an adhesive layer 3 coated on the surface of the base material 2, as shown in FIG. In the adhesive sheet 1 of the first aspect according to the invention, the base material 2
A radiation irradiation colored layer 4 containing a compound that is colored by radiation irradiation is coated on at least one of the front and back surfaces of the substrate. Moreover, in the adhesive sheet 1 of the second aspect of the present invention, a compound that is colored by radiation irradiation is added to the base material 2.

The radiation irradiation colored layer 4 containing a compound that is colored by radiation irradiation is applied to the base material 2 as shown in FIG.
The adhesive layer 3 may be formed on the surface on which the adhesive layer 3 is not provided, or it may be formed between the base material 2 and the adhesive layer 3 as shown in FIG. In order to protect the adhesive layer 3 before use, it is preferable to temporarily attach a releasable sheet (not shown) to the upper surface of the adhesive 3.

The shape of the adhesive sheet according to the present invention is tape-like,
It can take any shape, including a label. As the base material 2, a material having excellent water resistance and heat resistance is suitable, and a synthetic resin film is particularly suitable. As will be described later, the adhesive sheet of the present invention is irradiated with radiation such as EB or UV when it is used, so in the case of EB irradiation, the base material 2 does not need to be transparent. When using with UV irradiation,
Must be a transparent material.

Specific examples of such a base material 2 include polyethylene film, polypropylene film, polyvinyl chloride film, polyethylene terephthalate film, polybutylene terephthalate film, polybutene film, polybutadiene film, polyurethane film, polymethylpentene film, and ethylene vinyl acetate film. etc. are used. Furthermore, when crosslinked polyolefin is used as the base material 2, it is possible to prevent the base material 2 from elongating or bending during the wafer dicing process described later.

As the adhesive, a wide variety of conventionally known adhesives can be used, but acrylic adhesives are preferred, and specifically, those selected from homopolymers and copolymers containing acrylic acid ester as the main monomer unit. These are copolymers with acrylic polymers and other tubular monomers, and mixtures of these polymers. For example, monomer acrylic esters include ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, and the above-mentioned methacrylic acids. Those in place of acrylic acid can also be preferably used.

Furthermore, in order to increase the compatibility with the oligomers described below, (meth)acrylic acid, acrylonitrile,
Monomers such as vinyl acetate may be copolymerized. The molecular weight of the acrylic polymer obtained by polymerization from these monomers is 2.0×10 ⁵ to 10.0×10 ⁵ , preferably 4.0×10 ⁵ to 8.0×10 ⁵ .

In addition, radiation polymerizable compounds include photopolymerizable carbon in molecules that can be formed into a three-dimensional network by light irradiation, such as those disclosed in JP-A-60-196956 and JP-A-60-223139. -Low molecular weight compounds having at least two or more carbon double bonds are widely used, specifically, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monoacrylate. Hydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, etc. are used.

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

Such urethane acrylate oligomers preferably have a molecular weight of 3,000 to 10,000.
It is preferable to use a material having a molecular weight of 4,000 to 8,000 because even if the surface of the semiconductor wafer is rough, the adhesive will not adhere to the chip surface when the wafer chip is picked up. In addition, when using a urethane acrylate oligomer as a radiation polymerizable compound, a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule as disclosed in JP-A-60-196956 is used. Compared to the case where a compound is used, an extremely superior pressure-sensitive adhesive sheet can be obtained. That is, the adhesive strength of the adhesive sheet before irradiation with radiation is sufficiently large, and the adhesive strength decreases sufficiently after irradiation with radiation, so that no adhesive remains on the chip surface when the wafer chip is picked up.

The blending ratio of the acrylic adhesive and urethane acrylate oligomer in the adhesive in the present invention is as follows:
The urethane acrylate oligomer is preferably used in an amount ranging from 50 to 900 parts by weight based on 100 parts by weight of the acrylic pressure-sensitive adhesive. In this case, the resulting adhesive sheet has a high initial adhesive strength, but after radiation irradiation, the adhesive strength decreases significantly.
The wafer tip can be easily picked up from the adhesive sheet.

The compound used in the present invention that is colored by radiation irradiation is a compound that is colorless or light-colored before radiation irradiation, but becomes colored by radiation irradiation, and a preferable specific example of this compound is a leuco dye. It will be done. As the leuco dye, commonly used triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specifically, 3-[N
-(p-tolylamino)]-7-anilinofluorane, 3-[N-(p-tolyl)-N-methylamino]
-7-anilinofluorane, 3-[N-(p-tolyl)-N-ethylamino]-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, crystal violet Examples include lactone, 4,4',4''-trisdimethylaminotriphenylmethanol, and 4,4',4''-trisdimethylaminotriphenylmethane.

Color developers preferably used with these leuco dyes include conventionally used initial polymers of phenol-formalin resin, aromatic carboxylic acid transparent conductors, and electrophotoreceptors such as activated clay. When changing, various known color formers can be used in combination.

Once the compound that is colored by radiation irradiation is dissolved in an organic solvent or the like, the resulting solution is applied to either or both of the front and back surfaces of the base material 2. A radiation irradiation colored layer 4 containing a compound that is colored by radiation irradiation can be formed on at least one surface of the substrate.

Further, a compound that is colored by radiation irradiation is included in the undercoat composition, and the undercoat composition is applied to at least one of the front and back surfaces of the base material 2 to form the radiation irradiation colored layer 4. You may. Such undercoating compositions include those containing vinyl acetate-vinyl chloride copolymer as a main component;
Polyurethane resin, polyester resin, polyamide resin, epoxy resin, etc. are used. These undercoat compositions are appropriately selected and used depending on the type of the base material 2.

On the other hand, a solution obtained by dissolving the above-mentioned compound that is colored by radiation in an organic solvent, etc.
Used when forming the base material 2 into a sheet shape, the base material 2
A compound that is colored by radiation irradiation may be added therein. In some cases, a compound that is colored by radiation irradiation may be added to the base material 2 in the form of a fine powder.

In this way, the adhesive sheet 1 according to the present invention is exposed to radiation by applying a compound that is colored by radiation irradiation onto at least one of the front and back surfaces of the base material 2, or by including it in the base material 2. When the wafer chip is irradiated, the wafer chip is sufficiently colored, and the detection accuracy when detecting the wafer chip by the optical sensor is increased, thereby preventing malfunctions when picking up the wafer chip. Moreover, in the present invention, since the adhesive layer does not contain a compound that is colored by radiation irradiation, there is also the effect that there is no possibility that the adhesive force of the adhesive layer 3 will be adversely affected by the decrease in the adhesive force due to radiation irradiation. .

Further, by mixing an isocyanate curing agent into the above-mentioned pressure-sensitive adhesive, the initial adhesive strength can be set to an arbitrary value. Specifically, such curing agents include polyvalent isocyanate compounds,
For example, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3 -methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate,
Lysine isocyanate and the like are used.

Furthermore, in the case of UV irradiation, a UV initiator may be mixed into the above-mentioned adhesive to reduce the polymerization and curing time due to UV irradiation as well as the amount of UV irradiation.

Specifically, such UV initiators include:
Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β
- Examples include chloranthraquinone.

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

When a releasable sheet is provided on the top surface of the adhesive sheet 1 according to the present invention, the sheet is removed, and then the adhesive sheet 1 is placed with the adhesive layer 3 facing upward, as shown in FIG. In this manner, the semiconductor wafer A to be diced is adhered to the upper surface of the adhesive layer 3. In this adhered state, wafer A is subjected to various steps of dicing, cleaning, drying, and expanding. At this time, since the wafer chip is sufficiently adhered and held to the adhesive sheet by the adhesive layer 3, the wafer chip does not fall off during each of the above steps.

Next, each wafer chip is picked up from the adhesive sheet and mounted on the base in a predetermined position. At this time, prior to or during the picking up, ultraviolet rays (UV) or electron beams are applied as shown in FIG. Ionizing radiation B such as (EB) is irradiated onto the adhesive layer 3 of the adhesive sheet 1,
The radiation polymerizable compound contained in the adhesive layer 3 is polymerized and cured.

When the radiation-polymerizable compound is polymerized and cured by irradiating the adhesive layer 3 with radiation in this manner, the adhesive strength of the adhesive is greatly reduced, and only a small amount of adhesive strength remains.

The adhesive sheet 1 is preferably irradiated with radiation from the side of the base material 2 on which the adhesive layer is not provided. Therefore, as mentioned above, as radiation
When using UV, the base material 2 needs to be light-transmissive, but when using EB as radiation, the base material 2 does not necessarily have to be light-transparent.

After irradiating the adhesive layer 3 in the areas where the wafer tips A ₁ , A ₂ , . As shown in FIG. 5, the chip A ₁ ... to be picked up is pushed up from the lower surface of the base material 2 with the push-up needle ₅ in accordance with the conventional method. ... is picked up using air tweezers 6, for example, and mounted on a predetermined base. In this way, the wafer tip
When picking up A ₁ , A _{2 .} . . , the chips can be easily picked up without any adhesive adhering to the surface of the wafer chips, and chips of good quality without contamination can be obtained. Note that radiation irradiation can also be performed at a pick-up station.

The radiation irradiation does not necessarily need to be applied to the entire surface of the wafer A to be adhered at once, and some parts may be irradiated several times.
For example, the wafer tip A ₁ to be picked up,
A ₂ .... After irradiating each piece with a radiation tube that irradiates only the corresponding back side to reduce the adhesive strength of only the adhesive in that part, the wafers are attached using the raising needle ₅ . ₂ You can also pick up one by one by pushing up. 6th
The figure shows a modification of the above-mentioned radiation irradiation method. In this case, the push-up needle 5 is hollow, and a radiation source 7 is provided in the hollow part to perform radiation irradiation and pick-up at the same time. In this way, the device can be simplified and at the same time the pick-up operation time can be shortened.

In the above semiconductor wafer processing, it is also possible to perform a pick-up process on the wafer chips A ₁ , A _{2 .} . . immediately after dicing, cleaning, and drying without performing the expanding process.

The adhesive sheet 1 according to the present invention is sometimes preferably used when subjecting semiconductor wafers to a dicing process to a pick-up process as described above, but this adhesive sheet 1 can also be used when masking an object to be coated.

Effects of the invention In the pressure-sensitive adhesive sheet according to the present invention, the pressure-sensitive adhesive layer includes:
In addition to the adhesive and the radiation-polymerizable compound, a compound that colors when irradiated with radiation is provided on at least one of the front and back surfaces of the base material, or is added to the base material, so that the adhesive sheet can be colored after being irradiated with radiation. In this case, the sheet is colored, so that the detection accuracy is increased when the optical sensor detects the wafer chip, and malfunctions do not occur when the wafer chip is picked up. Further, whether or not the adhesive sheet has been irradiated with radiation can be immediately determined by visual inspection. Furthermore, when a urethane acrylate oligomer is used as a radiation-polymerizable compound in the adhesive sheet, a pressure-sensitive adhesive sheet with extremely excellent performance can be obtained.

The present invention will be explained below with reference to examples, but the present invention is not limited to these examples.

Example 1 4,4', 4,4',
After adding 5 parts by weight of 4″-trisdimethylaminotriphenylmethane, it was added to a base material with a thickness of 50 μm.
Coat and dry on one side of a polyethylene terephthalate film with a dry thickness of 1 to 2 μm.
An undercoat layer was formed.

On the undercoat layer, 100 parts by weight of an acrylic adhesive (a copolymer of n-butyl acrylate and acrylic acid), 100 parts by weight of a urethane acrylate oligomer with a molecular weight of 3,000 to 10,000, and 25 parts by weight of a curing agent (diisocyanate). parts by weight and 10 parts by weight of a UV curing reaction initiator (benzophenone type), and applied as an adhesive layer to a dry thickness of 10 μm.
The pressure-sensitive adhesive sheet of the present invention having a three-layer structure was obtained by heating at ℃ for 1 minute.

The adhesive layer of the resulting adhesive sheet was irradiated with ultraviolet (UV) light for 2 seconds using an air-cooled high-pressure mercury lamp (80 W/cm, irradiation distance 10 cm). The transparent adhesive sheet was colored blue-purple by UV irradiation.
When the color difference ΔE (L ^* a ^* b ^* ) during UV irradiation was measured using an SM color computer (manufactured by Suga Test Instruments), the color difference was 21.6.

In addition, after attaching a silicon wafer to this adhesive sheet and dicing it, we irradiated it with ultraviolet rays under the conditions described above and detected it with an optical sensor (SX-23R, manufactured by Sunkus Co., Ltd.). We were able to detect the wafer tip. Furthermore, when the wafer chip was picked up using an optical sensor, no malfunctions occurred at all.

Comparative Example 1 Example 1 except that the undercoat layer colored by ultraviolet irradiation was not formed in Example 1 above.
A pressure-sensitive adhesive sheet was formed in the same manner as above, and the color difference due to ultraviolet rays was examined. The color difference ΔE (L ^* a ^* b ^* ) of the resulting pressure-sensitive adhesive sheet before and after UV irradiation was 2.0 or less, and no coloration due to UV irradiation was observed.

Furthermore, when a silicon wafer was pasted onto this adhesive sheet and, after dicing, ultraviolet rays were irradiated and detection was performed using an optical sensor, there were cases where sufficient detection was not possible.

Furthermore, when a wafer chip was picked up using an optical sensor, malfunctions occurred.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of the adhesive sheet according to the present invention, and FIGS. 3 to 6 are explanatory views when the adhesive sheet is used from the dicing process to the pick-up process of semiconductor wafers. . DESCRIPTION OF SYMBOLS 1... Adhesive sheet, 2... Base material, 3... Adhesive layer, 4... Radiation irradiation colored layer, A... Wafer, B
……radiation.

Claims (1)

[Scope of Claims] 1. A pressure-sensitive adhesive sheet formed by coating a pressure-sensitive adhesive layer consisting of a pressure-sensitive adhesive and a radiation-polymerizable compound on a base material surface, wherein a compound that is colored by radiation irradiation is coated on at least one surface of the base material surface. An adhesive sheet characterized by: 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the compound that is colored by radiation irradiation is a leuco dye. 3. The adhesive sheet according to claim 2, wherein the leuco dye is 4,4',4''-trisdimethylaminotriphenylmethane. 4. The adhesive sheet according to claim 2, wherein the radiation polymerizable compound is a urethane acrylate oligomer. Adhesive sheet according to item 1. 5. In the adhesive sheet in which an adhesive layer consisting of an adhesive and a radiation-polymerizable compound is applied to the base material surface, a compound that is colored by radiation irradiation is added to the base material. 6. The adhesive sheet according to claim 5, wherein the compound that is colored by radiation irradiation is a leuco dye. 7. The leuco dye is 4,4′,4″-trisdimethylaminotriphenylmethane. An adhesive sheet according to claim 5. 8. The adhesive sheet according to claim 5, wherein the radiation polymerizable compound is a urethane acrylate oligomer.