JPH0224871B2 - - 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 digs into the adhesive layer or the base material.
A new problem arises in that the adhesive adheres to the cutting blade and causes clogging, making it impossible to cut the wafer with 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 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 to 100 μm in the base material.
It is characterized by dispersing abrasive grains with a Mohs hardness of 6 to 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 the surface of a base material, in which abrasive grains having a specific particle size and hardness are dispersed in the base material. Therefore, even if a semiconductor wafer is attached to an adhesive sheet and separated using a full-cut method using a cutting blade, a large amount of adhesive will not adhere to the cutting blade and cause clogging, and the polishing effect of the abrasive grains will not be affected. Therefore, the life of the cutting blade is less likely to be shortened.

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

The adhesive sheet for wafer adhesion according to the present invention has a first
As shown in the figure, it consists of a base material 2 and an adhesive layer 3 provided on the surface thereof, and abrasive grains 4 are dispersed in this base material 2.

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. .

In the wafer adhesion adhesive sheet 1 according to the present invention,
Abrasive grains 4 are dispersed in the base material 2. This abrasive grain 4
has a particle size of 0.5 to 100 μm, preferably 1 to 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, chromium oxide, cerium oxide, diamond powder, etc. are used. It is preferable that such abrasive grains 4 are colorless or white. Such abrasive grains 4 are
It is present in an amount of 0.5 to 70% by weight, preferably 5 to 50% by weight.

The adhesive sheet 1 for pasting wafers according to the present invention allows the cutting blade to be attached not only to the wafer but also to the base material 2.
It is particularly preferably used when the cutting depth is such that the cut can be made even deep.

By including the abrasive grains 4 as described above in the base material 2, even if the cutting blade cuts into the base material 2 and adhesive adheres to the cutting blade, the polishing effect of the abrasive grains will prevent The blockage can be easily removed.

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 polymerizing 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 polyether type, and a polyvalent isocyanate compound such as 2,
Obtained by reacting 4,-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 terminal isocyanate urethane prepolymer with a (meth)acrylate having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, or polyethylene glycol (meth)acrylate. 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.

Further, in the present invention, the adhesive layer 3 may contain a compound that is colored by radiation irradiation. 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. Leuco dyes include conventional triphenylmethane, fluoran, phenothiazine,
Auramine-based and spiropyran-based ones are preferably used. Specifically, 3-[N-(P-tolylamino)]-7-anilinofluorane, 3-[N-(P-tolylamino)]
-tolyl)-N-methylamino]-7-anilinofluorane, 3-[N-(P-tolyl)-N-ethylamino]-7-anilinofluorane, 3-diethylamino-6-methyl-7 -anilinofluorane, crystal violet lactone, 4,4',
Examples include 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 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 and the base material 2. However, since the base material 2 of the adhesive sheet 1 according to the present invention contains abrasive grains 4, the abrasive grains 4 reduce the adhesive from adhering to the cutting blade. Also, the sharpening of the blade can be achieved by the abrasive action of the abrasive grains, and therefore the life of the cutting blade will not be 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 5 according to a conventional method.
_{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 force of only the adhesive on that part, the wafers are held together with the push-up needle ₅ . ₂ You can also pick up one by one by pushing up. Fifth
The figure shows a modification of the above-mentioned radiation irradiation method. In this case, the push-up needle 5 is made 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, it is possible to simplify the apparatus and at the same time shorten the pick-up operation time.

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 applying an adhesive layer on the surface of a base material, in which abrasive grains having a specific particle size and hardness are dispersed in the base material. Therefore, even if a semiconductor wafer is attached to an adhesive sheet and is cut and separated using the cutting blade in a full-cut method, there is less chance that a large amount of adhesive will adhere to the cutting blade and cause clogging. Blade life 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 30 parts by weight of white alundum having an average particle size of 20 μm was added to 100 parts by weight of vinyl chloride resin with a degree of polymerization of 800 to produce a compound. Next, 30 parts by weight of dioctyl phthalate (DOP) was added to this compound, and a vinyl chloride film having a thickness of 100 μm was formed using a T-die extruder at a cylinder temperature of 160° C. and a die temperature of 200° C.

Also, the average molecular weight is approximately 350,000 (polyethylene equivalent)
100 parts by weight of acrylic adhesive (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 to prepare a pressure-sensitive adhesive composition.

This composition was transfer-coated onto the above abrasive grain-containing film to prepare a pressure-sensitive adhesive sheet for attaching wafers with a pressure-sensitive adhesive layer having a thickness of 10 μm.

A silicon wafer with a thickness of 350 μm and a diameter of 5 inches was attached to this adhesive sheet, and a 1 mm x 1 mm silicon chip was fully cut using a dicing saw set to a blade rotation speed of 30,000 and a cutting depth of 380 μm.

When processing wafers continuously, the blade became severely worn after about 30,000 lines and had to be replaced.

After irradiating the substrate surface of this diced wafer-fixing adhesive sheet with an electron beam generated from a linear filament at an acceleration voltage of 200 KeV and current of 20 mA for 2 Mrad, die bonding was performed.
I was able to pick up both chips with good accuracy.

Example 2 An acrylic adhesive (a copolymer of n-butyl acrylate, vinyl acetate, and acrylic acid) was applied on the abrasive-containing vinyl chloride film formed in Example 1.
Adhesive for wafer attachment, in which a pressure-sensitive adhesive composition prepared from part by weight (solid content 37%) and 3 parts by weight of an ethyleneimine curing agent is transfer-coated to give an adhesive layer thickness of 10 μm and a total thickness of 110 μm. I created a sheet. Example 1
Using the same silicon wafer and dicing saw conditions, a 1 mm x 1 mm silicon chip was fully cut.

When processing wafers continuously, the blade became less sharp after about 33,000 lines, so the blade was replaced.

Comparative Example 1 A film having a thickness of 100 μm was formed using the vinyl chloride compound of Example 1 to which no white alundum was added under the extrusion conditions of Example 1.
The acrylic pressure-sensitive adhesive composition of Example 2 was transfer-coated onto this film to prepare a pressure-sensitive adhesive sheet for wafer attachment having a pressure-sensitive adhesive layer having a thickness of 10 μm. Next, using the same silicon wafer and dicing saw conditions as in Example 1, a 1 mm x 1 mm silicon chip was fully cut.

When processing wafers continuously, around the 7,000th line, adhesive debris mixed with diamond particles from the blade began to adhere to the chip surface, and the sharpness of the blade rapidly deteriorated, so it was replaced.

Example 3 40 parts by weight of green carborundum with an average particle size of 10 μm was added to 100 parts by weight of vinyl chloride resin with a degree of polymerization of 800 to produce a compound.
A film with a thickness of 100 μm was formed under the following extrusion conditions.

The acrylic adhesive composition of Example 2 was transfer-coated onto this film, and the thickness of the adhesive layer was 10 μm.
An adhesive sheet for wafer attachment was created. Next, using the same silicon wafer and dicing saw conditions as in Example 1, a 1 mm x 1 mm silicon chip was fully cut.

When wafers were processed continuously, up to approximately 30,000 lines could be processed with the same blade without any trouble.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the adhesive sheet according to the present invention, and FIGS. 2 to 5 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, A... Wafer, B... Radiation.

Claims (1)

[Claims] 1. In an adhesive sheet for wafer adhesion, which is formed by coating an adhesive layer on the base material surface, particles with a particle size of 0.5
An adhesive sheet for attaching wafers characterized by dispersing abrasive grains having a diameter of ~100 μm and a Mohs hardness of 6 to 10.