JPS62153377A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

PURPOSE:To carry out detection accurately, by a photosensor and to prevent malfunction during picking up a semiconductor wafer chip from a pressure- sensitive adhesive sheet, by adding a compd. capable of being colored by irradiation with a radiation to the pressure-sensitive adhesive layer of a pressure- sensitive adhesive sheet. CONSTITUTION:This pressure-sensitive adhesive sheet is obtd. by adding a compd. which is colored by irradiation with a radiation to the pressure-sensitive adhesive layer of a pressrue-sensitive adhesive sheet composed of a pressure- sensitive adhesive layer containing a pressure-sensitive adhesive and a radiation- polymerizable compd. provided on a substrate. Examples of the compd. which is colored by irradiation with a readiation are leuco pigments, among which 4,4',4''-trisdimethylaminotriphenyl methane is preferred. When a urethane acrylate oligomer having an MW of pref. 3,000-10,000 is used as said radiation- polymerizable compd., the adhesive is prevented from adhering to the surface of a wafer chip in picking it up, even when the surface of semiconductor wafer is rough.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive sheet that is particularly preferably used when 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 (diced) into small element pieces, 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.

The adhesive sheet used in such a semiconductor wafer dicing process has conventionally been one in which an acrylic or other adhesive layer is provided on a base material such as vinyl chloride or polypropylene. However, with such adhesive sheets having an acrylic adhesive layer, there was a problem in that when each chip of a diced semiconductor wafer was picked up, the adhesive remained on the chip surface and the chips were 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 chips and the adhesive sheet is reduced, so the dicing process cleaning followed by
A new problem arises in that the wafer chip detaches from the adhesive sheet during the drying and expanding steps.

Adhesive sheets used in processes ranging from the dicing process to the pick-up process of semiconductor wafers include:
It is desired that the adhesive has sufficient adhesive strength to the wafer chips from the dicing process to the expanding process, and has enough adhesive strength to prevent the adhesive from adhering to the wafer chips in the pickup process.

As such an adhesive sheet, JP-A-60-196.
No. 956 and JP-A No. 60-223゜139@, a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule that can be formed into a three-dimensional network by irradiation with light is disclosed A pressure-sensitive adhesive sheet coated with a pressure-sensitive adhesive has been proposed. According to the publication, low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in the molecule include trimethylolpropane acrylate, tetramethylolmethanetetraacrylate, pentaeryswattol triacrylate, and pentaerythritoltetraacrylate. Examples include acrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, and commercially available oligoester acrylate. There is.

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 pasted 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 above-mentioned adhesive sheet, the detection light for the chip position may be reflected by the adhesive sheet, making it impossible to accurately detect the chip position, which may lead to malfunctions during pickup. The inventors found that there are points. In addition, the inventors have discovered that with the above-mentioned adhesive sheet, when irradiated with ultraviolet rays, the adhesive strength temporarily decreases, but the adhesive strength does not decrease until it reaches the optimal value, and the larger the chip, the less it is picked up. discovered by.

The inventors of the present invention have conducted intensive studies to solve the problems associated with the conventional technology, and have found that it is sufficient to add a compound that can be colored by radiation irradiation to the adhesive layer, thereby completing the present invention. reached.

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 aims to solve all of the problems associated with the prior art as described above, and is to perform detection with an optical sensor with high precision when picking up wafer chips from an adhesive sheet. Therefore, malfunctions do not occur during the wafer chip positioning process, and in addition, it has sufficient adhesive strength before irradiation with radiation 9A radiation, and the adhesive strength decreases sufficiently after radiation irradiation, so that the wafer chip Semiconductor wafers that do not have adhesive attached to the back surface, and in addition, workers managing the dicing process can easily check whether or not the adhesive sheet has been irradiated with radiation, preventing process problems. It is an object of the present invention to provide a pressure-sensitive adhesive sheet that is particularly preferably used when subjecting a material to a dicing process.

Summary of the Invention The pressure-sensitive adhesive sheet according to the present invention is a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive and a radiation-polymerizable compound is coated on a base material surface, and a compound that is colored by radiation irradiation is added to the pressure-sensitive adhesive layer. It is characterized by the addition of

In the pressure-sensitive adhesive sheet according to the present invention, in addition to the pressure-sensitive adhesive and the radiation-polymerizable compound, a compound that is colored by radiation irradiation is added to the pressure-sensitive adhesive layer. The sheet is colored, so that the optical sensor can detect the wafer chips with high detection accuracy, and no malfunction will occur when picking up the wafer chips. Also, whether or not the adhesive sheet has been irradiated with radiation can be immediately determined by visual inspection. When a urethane acrylate oligomer is used as a radiation-polymerizable compound in a PSA sheet, a PSA sheet with extremely excellent performance can be obtained.

Detailed description of the invention The adhesive sheet according to the present invention will be specifically explained below.

As the cross-sectional view of the adhesive sheet 1 according to the present invention is shown in FIG. In order to protect the layer 3, it is preferable to temporarily attach a releasable sheet 4 to the upper surface of the adhesive 3 as shown in FIG.

The shape of the pressure-sensitive adhesive sheet according to the present invention can be any shape such as a tape shape or a label shape. As the base material 2, a material with low electrical conductivity and excellent water resistance and heat resistance is suitable.
In particular, synthetic resin films are suitable. In the pressure-sensitive adhesive sheet of the present invention, as described later, E, B, U,
Since radiation irradiation such as V is being carried out, E, B,
In the case of irradiation, the substrate 2 need not be transparent, but
.

(2) When used with irradiation, the material must be transparent.

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 film. Acid film etc. are used.

If it is necessary to perform an expanding process after dicing a semiconductor wafer, it is preferable to use a synthetic resin film that is stretchable in the length and width directions, such as polyvinyl chloride or polypropylene, as the base material, as in the past. However, when the adhesive sheet according to the present invention is used for semiconductor processing that does not require such an expanding treatment or for masking of automobiles, etc., any base material without extensibility can also be used.

In the present invention, the adhesive layer 3 provided on the base material 2 as described above is formed including an adhesive, a radiation polymerizable compound, and a compound that is colored by radiation irradiation.

Conventionally known adhesives are widely used, but
Acrylic adhesives are preferred, and specifically, acrylic polymers selected from homopolymers and copolymers containing acrylic esters as the main constituent monomer unit and copolymers with other functional monomers. and mixtures of these polymers. For example, as a monomer acrylic ester,
Ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, etc., and those in which the above methacrylic acid is replaced with acrylic acid are also preferred. Can be used.

Furthermore, in order to increase the compatibility with the oligomers described later, (
Monomers such as meth>acrylic acid, acrylonitrile, and vinyl acetate may be copolymerized.

The molecular weight of the acrylic polymer obtained by polymerizing these monomers is 2.0X105 to 10.0X10'', preferably 4.0X105 to 8.0X10''.

In addition, examples of radiation polymerizable compounds include, for example, JP-A-60
-196.956M publication and JP-A-60-223,1
Low molecular weight compounds having at least two or more photopolymerizable carbon-carbon double bonds in the molecule that can be formed into a three-dimensional network by light irradiation, as disclosed in Japanese Patent Application No. 39, are widely used. Methylolpropane acrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4-butylene glycol diacrylate, 1,6-hexane Diol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, etc. are used.

In addition to the above-mentioned acrylate compounds, urethane acrylate oligomers can also be used as radiation polymerizable compounds. 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-tolylene diine cyanate, 2,6-tolylene diine cyanate, 1,3-xylylene dicyanate, etc. A (meth)acrylate having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, is added to a terminal isocyanate urethane prepolymer obtained by reacting isocyanate, 1°4-xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, etc. ) acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol (meth)acrylate, etc. are reacted. This urethane acrylate oligomer is a radiation polymerizable compound having at least one carbon-carbon double bond.

As such urethane acrylate oligomer,
In particular, the molecular weight is 3,000 to 10,000, preferably 4,000.
It is preferable to use one having a molecular weight of 8,000 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. Furthermore, when using a urethane acrylate oligomer as a radiation polymerizable compound, JP-A-60-196,956
Compared to the case of using a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in the molecule as disclosed in the above publication, an extremely superior pressure-sensitive adhesive sheet can be obtained. That is, the adhesive strength of the adhesive sheet before radiation irradiation is sufficiently large, and the adhesive strength decreases sufficiently after radiation irradiation, so that no adhesive remains on the chip surface when the wafer chip is picked up.

The blending ratio of the acrylic adhesive and the urethane acrylate oligomer in the adhesive in the present invention is such that the urethane acrylate oligomer is used in an amount of 90 to 10 parts by weight per 10 to 90 parts by weight of the acrylic adhesive. It is preferable. In this case, the adhesive sheet prepared by 1q has a high initial adhesive strength, but the adhesive strength decreases significantly after radiation irradiation, and the wafer chip can be easily picked up from the adhesive sheet.

In the present invention, the adhesive layer 3 contains, in addition to the above-described adhesive and radiation polymerizable compound, a compound that is colored by radiation irradiation.

A compound that is colored by radiation irradiation is a compound that is colorless or pale colored before radiation irradiation, but becomes colored by radiation irradiation, and a preferred specific example of this compound is a leuco dye. As the leuco dye, conventional triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specifically, 3-[N-(P-tolylamiso)]-7-anilitufluorane, 3-[N-(P-
tolyl)-N-methylamino]-7-anirithufluorane, 3-[N-(P-tolyl>-N-ethylamino]-
7-anirite fluorane, 3-diethylamino-6-
Examples include methyl-7-anilinofluorane, crystal violet lactone, 4,4',4°-trisdimethylaminotriphenylmethanol, and 4.4°,4''-trisdimethylaminotriphenylmethane.

Color developers that are preferably used with these leuco dyes include electron acceptors such as conventionally used initial polymers of phenol-formalin resin, aromatic carboxylic acid derivatives, and activated clay. In this case, various known coloring agents may be used in combination.

Such a compound that is colored by radiation irradiation may be dissolved in an organic solvent or the like and then included in the adhesive layer, or may be made into a fine powder and included in the adhesive layer. This compound is desirably used in the adhesive layer in an amount of 0.01 to 10% by weight, preferably 0.5 to 5% by weight. If the compound exceeds 10% by weight, this compound will absorb too much of the radiation irradiated to the adhesive sheet, resulting in insufficient curing of the adhesive layer, which is undesirable. If it is used in an amount less than .01% by weight, the adhesive sheet may not be sufficiently colored during radiation irradiation, and malfunctions may easily occur when picking up wafer chips, which is not preferable.

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. Examples of such curing agents include polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,
1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4''-diisocyanate, diphenylmethane-2,4-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate Isocyanate, inphorone diisocyanate, dicycloxylmethane-4,4°-diisocyanate, dicyclohexylmethane-2,4°-
Diisocyanate, lysine isocyanate, etc. are used.

In the case of U, V, and irradiation in the above-mentioned adhesive,
By incorporating U, V, initiator, U, V, polymerization curing time by irradiation and U, V.

Irradiation can be reduced.

Specific examples of such U, V, and initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, Examples include diacetyl, β-chloroanthraquinone, and the like.

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

When a releasable sheet 4 is provided on the top surface of the adhesive sheet 1 according to the present invention, the sheet 4 is removed, and then the adhesive sheet 1 is placed with the adhesive layer 3 facing upward, and this adhesive Semiconductor wafer A to be diced on the top surface of layer 3
Paste. In this adhered state, wafer A is subjected to various steps of dicing, cleaning, drying, and expanding.

At this time, since the wafer chips are sufficiently adhered and held to the adhesive sheet by the adhesive layer 3, the wafer chips will not fall off during each of the above steps.

Next, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined base. At this time, prior to or during pickup, ultraviolet rays (tJ, V,) or electron beams (E, B,) are used. The adhesive layer 3 of the adhesive sheet 1 is irradiated with ionizing radiation B such as the above, and 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.

Radiation irradiation to the adhesive sheet 1
It is preferable to do this from the side that is not provided with. Therefore, as mentioned above, when using U and V as radiation, the base material 2 needs to be transparent, but when using E and B as radiation, the base material 2 is not necessarily transparent. It doesn't have to be transparent.

In this way, the wafer chip △1. After irradiating the adhesive @3 in the area where A2... is provided to reduce the adhesive force of the adhesive layer 3, this adhesive sheet 1 is taken to a pick-up station ("shown in the figure"). Here, according to a conventional method, the chip A1 to be picked up is pushed up from the bottom surface of the base material 2 with the push-up needle rod 5.
This chip A1... is picked up by air tweezers 6, for example, and mounted on a predetermined base. In this way, wafer chip A1. A2
When the wafer chips are picked up, no adhesive adheres to the surface of the wafer chips, and the chips can be easily picked up, resulting in chips of good quality and no contamination.

Note that radiation irradiation can also be performed at a pickup station.

It is not necessarily necessary to irradiate the entire surface of the wafer A to which it is attached at once, and it is also possible to irradiate the entire surface of the wafer A several times. Each wafer chip A is irradiated with a radiation irradiation tube that irradiates only the corresponding back surface to reduce the adhesive force of only the adhesive on that part, and then the wafer chip A is , A2...
You can also pick up items in sequence by pushing them up. FIG. 6 shows a modification of the above-mentioned radiation irradiation method. In this case, the push-up needle rod 5 is made hollow, and a radiation source 7 is provided in the hollow part to perform radiation irradiation and pickup. It is possible to do both at the same time, and in this way the device can be simplified and at the same time the pick-up operation time can be shortened.

Note that in the processing of the semiconductor wafer described above, the expanding process is not performed, and the wafer chips A1. A2... pick-up processing can also be performed.

The adhesive sheet 1 according to the present invention is 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. . For example, as shown in FIG. 7, the adhesive sheet 1 according to the present invention is applied onto the non-painted surface 9 of an object 8 to be painted, such as the body of an automobile, and then a coating film 10 is applied onto the object 8 in this state. After forming the adhesive sheet 1, radiation is irradiated onto the adhesive sheet 1 to reduce the adhesive strength of the sheet 1, and then the sheet 1 is peeled off from the object to be coated. In this way, an excellent effect can be obtained in that no adhesive remains on the surface of the object 8 to be coated.

In the pressure-sensitive adhesive sheet according to the present invention, in addition to the pressure-sensitive adhesive and the radiation-polymerizable compound, a compound that is colored by radiation irradiation is added to the pressure-sensitive adhesive layer. After the wafer chips are picked up, the sheet is colored, so that the detection accuracy is increased when the optical sensor detects the wafer chips, and malfunctions do not occur when the wafer chips are picked up. Also, whether or not the adhesive sheet has been irradiated with radiation can be immediately determined by visual inspection. When a urethane acrylate oligomer is used as a radiation-polymerizable compound in a PSA sheet, a PSA sheet with extremely excellent performance can be obtained.

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

Example 1 100 parts of an acrylic adhesive (a copolymer of n-butyl acrylate and acrylic acid), 100 parts of a urethane acrylate oligomer (trade name Seirybeam EX808, manufactured by Dainichiseika Chemical Industry Co., Ltd.), and a curing agent ( 25 parts of diisocyanate type) and 1 part of UV curing initiator (ben/phenone type)
0 parts and further added 5 parts of 4,4',4°°-trisdimethylaminotriphenylmethane, which is necessary for leuco dyes as a compound that can be colored by ultraviolet irradiation, to form an adhesive layer on one side of the film. Adhesive layer thickness 10μm
The adhesive sheet was formed by coating the adhesive sheet and heating it at 100°C for 1 minute.

The adhesive layer of the resulting adhesive sheet was irradiated with ultraviolet rays (UV) for 2 seconds using an air-cooled high-pressure mercury lamp (80 W/cm, irradiation distance 10 cm).

The transparent adhesive sheet was colored bluish-purple by UV irradiation. Color difference △F ((L a b
) was measured using a 3M color computer (manufactured by Suga Test Instruments Co., Ltd.), and the color difference was 2z, 8.

In addition, a silicon wafer was pasted onto this adhesive sheet, and after dicing it was irradiated with ultraviolet rays under the conditions described above.
When detection was performed using an optical sensor (SX-25R, manufactured by Sunkus Co., Ltd.), the wafer chips could be easily detected. Furthermore, when a wafer chip was pick-amplified using an optical sensor, no malfunctions occurred at all.

Comparative Example 1 A pressure-sensitive adhesive sheet was formed in the same manner as in Example 1 except that no compound that colored by ultraviolet irradiation was used, and the color difference caused by ultraviolet irradiation was examined.

Color difference ΔE (via
* b * > is 2. O or less, and 1 due to ultraviolet irradiation
No color was recognized.

Furthermore, when a silicon wafer was pasted onto this adhesive sheet, diced, irradiated with ultraviolet rays, and detected with an optical sensor, some detection failures occurred. When wafer chips were roughly picked up using an optical sensor, some malfunctions occurred.

Example 2 In Example 1, instead of the urethane acrylate oligomer as the radiation polymerizable compound, a polymer with a molecular weight of about 58
A pressure-sensitive adhesive sheet was formed in the same manner as in Example 1 except that about 0% pentaerythritol triacrylate was used, and the color difference due to ultraviolet irradiation was examined.

Color difference △E(L) of the obtained adhesive sheet before and after UV irradiation
a b ) was 25.0.

In addition, a silicon wafer was pasted on this adhesive sheet, and after dicing, UV irradiation was performed under the above conditions.
When detection was performed using an optical sensor, the wafer chip could be detected without any detection failure. When we roughly picked up wafer chips using an optical sensor, no 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. , and FIG. 7 are explanatory views when the adhesive sheet according to the present invention is used for masking an object to be painted. DESCRIPTION OF SYMBOLS 1... Adhesive sheet, 2... Base material, 3... Adhesive layer, 4... Peeling sheet, A... Wafer, B... Radiation.

Claims (4)

[Claims] (1) A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive and a radiation-polymerizable compound coated on a base material surface, characterized in that a compound that is colored by radiation irradiation is added to the pressure-sensitive adhesive layer. sheet. (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 1, wherein the radiation polymerizable compound is a urethane acrylate oligomer.