JPH0224872B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an adhesive sheet for adhering wafers, and more particularly to an adhesive sheet for adhering wafers 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 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.

The adhesive sheet used in such a semiconductor wafer dicing process has conventionally been one in which an acrylic adhesive layer is provided on a base material such as vinyl chloride or polypropylene.

By the way, in order to cut and separate semiconductor wafers using the above-mentioned adhesive sheet with a cutting blade, a half-cut method in which about half the thickness of the semiconductor wafer is cut has been mainly adopted.
However, this half-cut method has a problem in that it is necessary to further divide the wafer that has been cut by the cutting blade.

In order to solve these problems, a full cut method is being adopted in which the wafer is completely cut by a cutting blade. According to this full-cut method, the wafer is completely cut, so there is no need to divide the wafer, but when cutting the wafer, the cutting blade also digs into the adhesive layer, so the adhesive adheres to the cutting blade and causes clogging. A new problem arises in that the wafer cannot be cut by the cutting blade. Cutting blades with adhesives adhered to them are brought into contact with a so-called dresser board in order to remove the adhesive and restore sharpness. The lifespan is about 1/10 that of the half-cut method.

Shortening the life of the cutting blade means that
In addition to the problem that a new expensive cutting blade is required, there is also the problem that it takes time and effort to replace the cutting blade. This is because precision is required when replacing the cutting blade.

As mentioned above, there is a need to cut wafers using the full-cut method using a cutting blade, but at present there is a major problem in that when the full-cut method is adopted, the life of the cutting blade is significantly shortened. There is.

OBJECT OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above, and is to separate a semiconductor wafer by cutting and separating it with a cutting blade in a state in which it is attached to an adhesive sheet using a full-cut method. The present invention also provides an adhesive sheet for pasting wafers that does not cause clogging due to a large amount of adhesive adhering to the cutting blade, and does not shorten the life of the cutting blade due to the polishing effect of abrasive grains. It is intended to.

Summary of the Invention The first adhesive sheet for wafer adhesion according to the present invention is an adhesive sheet for wafer adhesion formed by coating an adhesive layer on a base material surface.
It is characterized by dispersing abrasive grains with a diameter of 0.5 to 100 μm and a Mohs hardness of 6 to 10.

Further, the second adhesive sheet for wafer adhesion according to the present invention is an adhesive sheet for wafer adhesion formed by coating an adhesive layer on the surface of a base material, in which the particle size is 0.5 between the base material and the adhesive layer. ~100μm and Mohs hardness is 6
It is characterized by providing an abrasive grain layer containing abrasive grains of ~10.

The adhesive sheet for wafer adhesion according to the present invention is an adhesive sheet for wafer adhesion formed by coating an adhesive layer on a base material surface, and in which abrasive grains having a specific particle size and hardness are dispersed in the adhesive layer. Alternatively, since an abrasive layer containing abrasive grains as described above is provided between the base material and the adhesive layer, the semiconductor wafer attached to the adhesive sheet can be cut and separated using a full cut method using a cutting blade. However, due to the abrasive effect of the abrasive grains, a large amount of adhesive will not adhere to the cutting blade and cause clogging, and therefore the life of the cutting blade will not be shortened.

DETAILED DESCRIPTION OF THE INVENTION The adhesive sheet for attaching wafers according to the present invention will be specifically described below.

As shown in FIG. 1, the first adhesive sheet for attaching wafers according to the present invention consists of a base material 2 and an adhesive layer 3 provided on the surface of the base material 2. In this case, abrasive grains 4 are dispersed.

Further, as shown in FIG. 2, the second adhesive sheet 1 for pasting wafers according to the present invention consists of a base material 2 and an adhesive layer 3 provided on the surface of the base material 2. An abrasive grain layer 5 containing abrasive grains 4 is provided between the layer 3 and the abrasive grain layer 5.
is provided.

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 described later, in the pressure-sensitive adhesive sheet of the present invention, when irradiation with radiation such as EB or UV is performed during its use, 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. It is also possible to use a polymer film containing a compound having a carboxyl group as a polymer constituent unit, or a laminate of this and a general-purpose polymer film.

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. .

As the adhesive, conventionally known adhesives such as rubber-based or acrylic-based adhesives can be widely used, but acrylic-based adhesives are preferred, and specifically,
These are copolymers of acrylic polymers selected from homopolymers and copolymers having acrylic ester as a main constituent monomer unit, copolymers with other functional 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.
In order to prevent the adhesive from adhering to the back surface of the wafer, it is preferable to use a low-tack adhesive.

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 5.0×10 ⁴ to 10.0×10 ⁵ , preferably 2.0×10 ⁵ to 8.0×10 ⁵ .

By including a radiation-polymerizable compound in the adhesive layer as described above, the adhesive force can be reduced by irradiating the adhesive layer with radiation after cutting and separating the wafer. Examples of such radiation-polymerizable compounds include, for example,
Low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in the molecule that can be formed into a three-dimensional network by light irradiation as disclosed in JP-A No. 196956 and JP-A No. 60-223139 are widely used, specifically trimethylolpropane acrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,
Dipentaerythritol monohydroxypentaacrylate, 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 one having a molecular weight of 4,000 to 8,000, since even if the semiconductor wafer surface 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 radiation irradiation is sufficiently high, and the adhesive strength is sufficiently reduced 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 radiation polymerizable compound such as urethane acrylate oligomer in the adhesive in the present invention is 10% of the acrylic adhesive.
~90 parts by weight, radiation polymerizable compound is 90~10 parts by weight
Preferably, amounts in the range of parts by weight are used.
In this case, the adhesive sheet obtained has a high initial adhesive strength, but the adhesive strength decreases significantly after radiation irradiation, and the wafer tip can be easily picked up from the adhesive sheet.

First wafer adhesion adhesive sheet 1 according to the present invention
In this case, abrasive grains 4 are dispersed in the adhesive layer 3.
The abrasive grains 4 have a particle size of 0.5 to 100 μm, preferably 1
~50 μm and a Mohs hardness of 6 to 10, preferably 7 to 10. Specifically, green carborundum, artificial corundum, optical emery, white alundum, boron carbide, flom oxide (), cerium oxide, diamond howder, etc. are used. It is preferable that such abrasive grains 4 are colorless or white. Such abrasive grains 4 are preferably contained in an amount of 0.5 to 60% by weight in the adhesive layer.
Present in an amount of ~30% by weight.

Further, in the second wafer adhesion adhesive sheet 1 according to the present invention, an abrasive layer 5 containing the abrasive grains 4 as described above and the adhesive as described above is provided. The thickness of this abrasive grain layer 5 is 1 to 150 μm, preferably 5 to 80 μm.
That's about it. Further, in this abrasive grain layer 5, the abrasive grains 4 are present in an amount of 10 to 100% by weight, preferably 30 to 80% by weight.

The second wafer adhesion adhesive sheet 1 according to the present invention is particularly preferably used when the cutting blade is used at a depth that cuts not only into the wafer but also into the base material 2.

By including the abrasive grains 4 as described above in the adhesive layer 3 or by providing an abrasive grain layer 5 containing the abrasive grains 4, the cutting blade can cut into the adhesive layer 3 and the cutting blade can be cut into the adhesive layer 3. Even if the adhesive adheres, the abrasive grains' abrasive effect can easily clear the blockage.

Further, in the present invention, a compound that is colored by radiation irradiation can also be included in the adhesive layer. Such compounds that are colored by radiation irradiation are colorless or light-colored before radiation irradiation, but become colored by radiation irradiation, and preferred specific examples of these compounds include leuco dyes. 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 Lactone, 4,4′,4″−
trisdimethylaminotriphenylmethanol,
Examples include 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 some cases, 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 this compound is used in an amount exceeding 10% by weight, the radiation irradiated to the adhesive sheet will be absorbed too much by this compound, resulting in insufficient curing of the adhesive layer, which is undesirable. If it is used in an amount less than % by weight, the pressure-sensitive adhesive sheet may not be sufficiently colored during radiation irradiation, and malfunctions may easily occur when picking up a wafer tip, 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. Specifically, such curing agents include polyvalent isocyanate compounds,
For example, 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, isophorone diisocyanate, dicycloxylmethane-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 curing time and UV irradiation amount due to 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. A semiconductor wafer A to be diced is attached to the upper surface of the wafer A. A dicing process is applied to wafer A in this adhered state.

At this time, the cutting blade completely cuts the wafer A and reaches the adhesive layer 3. However, in the adhesive sheet 1 according to the present invention, the adhesive layer 3 contains the abrasive grains 4, or the abrasive grain layer 5 containing the abrasive grains 4
Because the abrasive grains 4 work, the adhesive is less likely to adhere to the cutting blade, and even if adhesive adheres, the blade can be sharpened by the abrasive action of the abrasive grains. Therefore, the life of the cutting blade is not significantly shortened.

After the dicing process, cleaning, drying, and expanding processes are applied to the wafer. At this time, since the wafer tip is sufficiently adhered and held to the adhesive sheet by the adhesive layer 3, the wafer tip does 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. However, if the adhesive layer 3 contains a radiation-polymerized compound, the UV rays are Adhesive sheet 1
The radiation is applied to the adhesive layer 3 to polymerize and harden the radiation-polymerizable compound contained in the adhesive layer 3. 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 3 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 . (not shown), and here the chips to be picked up from the bottom surface of the base material 2 with a push-up needle 6 according to a conventional method are transferred.
_{A 1} . By picking up the wafer chips A ₁ , A ₂ , etc. in this way, the wafer chips can be easily picked up without any adhesive sticking to the surface of the wafer chips.
Good quality chips without contamination can be obtained. Note that radiation irradiation can also be performed at a pick-up station.

It is not necessarily necessary to irradiate the entire surface of the wafer A at once, and it is also possible to irradiate the entire surface of the wafer A in several parts. ₁ ,
After irradiating each piece of A ₂ ... with a radiation tube that irradiates only the corresponding back surface to reduce the adhesive strength of the adhesive in that area, the wafer chips A ₁ , A are attached using a push-up 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 6 is hollow, and a radiation source 8 is provided in the hollow part to perform radiation irradiation and pick-up at the same time. In this way, the apparatus can be simplified and at the same time the pick-up operation time can be shortened.

In the above semiconductor wafer processing, the wafer chips A ₁ , A _{2 .} . . may be picked up immediately after dicing, cleaning, and drying without performing the expanding step.

Effects of the Invention The adhesive sheet for wafer adhesion according to the present invention is an adhesive sheet for wafer adhesion formed by coating an adhesive layer on a base material surface, and includes abrasive grains having a specific particle size and hardness in the adhesive layer. By dispersing or by providing an abrasive layer containing the above-mentioned abrasive grains between the base material and the adhesive layer, the semiconductor wafer can be fully cut using a cutting blade while attached to the adhesive sheet. Even when cutting and separating, a large amount of adhesive adheres to the cutting blade and clogging is unlikely to occur, so the life of the cutting blade is not significantly shortened.

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 by weight of an acrylic adhesive with an average molecular weight of approximately 350,000 (polystyrene equivalent) (solid content 40% by weight)
and 70 parts by weight of bifunctional urethane acrylate oligomer with an average molecular weight of approximately 6000 (solid content 60% by weight)
, 5 parts by weight of an isocyanate curing agent, and 4 parts by weight of benzophenone.
An adhesive composition was prepared in which 10 parts by weight of 5 μm carborundum was uniformly dispersed.

This composition was transfer coated onto a 100 μm thick low density polyethylene film and the adhesive layer was 20 μm thick.
An adhesive sheet for wafer attachment was created.

A silicon wafer with a thickness of 300 μm and a diameter of 5 inches was attached to this adhesive sheet, and the number of blade rotations was 30,000.
Silicon chips with a size of 0.35 mm x 0.35 mm were half-cut using a dicing saw set to a cutting depth of 250 μm. When wafers were processed continuously using this half-cut method, the blade became worn out after about 40,000 lines and had to be replaced.

In addition, ultraviolet rays (UV) are irradiated from the base material surface of the diced wafer-fixing adhesive sheet for 2 seconds using an air-cooled high-pressure mercury lamp (80 W/cm, irradiation distance 10 cm), and then, after breaking, die bonding is performed. As a result, we were able to pick up both chips with good accuracy.

Example 2 In Example 1, a silicon chip with a size of 0.35 mm x 0.35 mm was fully cut using a dicing saw in which the cutting depth of the blade was set to 320 μm. In other words, when wafers were processed continuously using this full-cut method that cuts down to the adhesive layer, approximately
On the 32,000 line, there was so much adhesive that it became difficult to cut, so I replaced the blade.

Next, die bonding was performed by UV irradiation under the same conditions as in Example 1, and it was able to be picked up without any problem.

Visual inspection revealed that no adhesive was attached to the back surface of the peeled wafer chip.

Comparative Example 1 A pressure-sensitive adhesive sheet was formed in the same manner as in Example 1 except that no carborundum was added to the pressure-sensitive adhesive composition, and the cutting depth of a 5-inch diameter silicon wafer with a thickness of 300 μm was set to 320 μm. The size is 0.35mm× with the dicing saw
Full cut of 0.35mm chip.

As a result, many cracks occurred in the chip around the 10,000 line, and it was confirmed that adhesive debris mixed with diamond particles from the blade had adhered to the chip surface, and the cause was that the adhesive that had become clogged during cutting had become diamond It was easy to infer that this was due to the fact that the particles were stripped off.

Example 3 100 parts by weight of an acrylic adhesive (copolymer of n-butyl acrylate, vinyl acetate, and acrylic acid) (solid content 37% by weight) and ethyleneimine curing agent 3
parts by weight and artificial corundum with an average particle size of 10 μm.
A pressure-sensitive adhesive composition was prepared by uniformly dispersing 20 parts by weight.

This composition was transfer-coated onto a vinyl chloride film having a thickness of 80 μm to prepare a pressure-sensitive adhesive sheet for attaching wafers having a pressure-sensitive adhesive layer having a thickness of 30 μm. Using the same wafer and dicing saw conditions as in Example 2, the wafer was fully cut to a cutting depth of 320 μm.

When wafers were continuously diced, approx.
I was able to process up to 34,000 lines without any trouble.

Comparative Example 2 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 3 except that no artificial corundum was added to the pressure-sensitive adhesive composition, and the same wafer was attached.
A full cut was made with a cutting depth of 320μm.

At about 8,000 lines, adhesive particles mixed with diamond particles from the blade began to adhere to the tip surface, and the sharpness of the blade suddenly decreased.

Example 4 An abrasive layer forming composition prepared by uniformly dispersing 100 parts by weight of chromium oxide (2) having a particle size of 40 μm in 100 parts by weight of a polyester binder resin was
Sheet 1 was prepared by coating on a 40 μm polyethylene terephthalate film and having an abrasive grain layer of 50 μm.

Next, acrylic adhesive (copolymer of n-butyl acrylate, vinyl acetate, and acrylic acid) 100
An adhesive composition consisting of parts by weight (solid content 37% by weight) and 3 parts by weight of an ethyleneimine curing agent was applied to the abrasive layer surface of sheet 1 to a thickness of 10 μm, and the total thickness was
An adhesive sheet for wafer attachment with a thickness of 100 μm was created.

Example 2 of the wafer and dicing saw conditions used
The wafer was fully cut with a cutting depth of 330 μm.

When wafers were successively diced, approximately 30,000 lines could be processed with the same blade without any trouble.

[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... Abrasive grain, 5... Abrasive grain layer, A... Wafer,
B...Radiation.

Claims (1)

[Scope of Claims] 1. In an adhesive sheet for wafer adhesion, which is formed by coating an adhesive layer on a base material surface, the adhesive layer has a particle size of
An adhesive sheet for attaching wafers, characterized in that abrasive grains having a diameter of 0.5 to 100 μm and a Mohs hardness of 6 to 10 are dispersed therein. 2. In an adhesive sheet for wafer adhesion, which is formed by coating an adhesive layer on the base material surface, a particle size of 0.5 to 100 μm and a Mohs hardness of 6 to 6 is provided between the base material and the adhesive layer.
An adhesive sheet for attaching wafers, characterized in that an abrasive grain layer containing abrasive grains having a particle size of 10 is provided.