JPS62205179A - Adhesive sheet for applying wafer - Google Patents

Abstract

PURPOSE:The titled sheet, obtained by using a crosslinked film as a base material and applying an adhesive layer consisting of an adhesive and radiation polymerizable compound onto the surface of the above-mentioned base material and used for cutting and separating a semiconductor wafer into small pieces without causing deflection. CONSTITUTION:An adhesive sheet 1 obtained by using a crosslinked film, preferably crosslinked polyolefin film as a base material 2 and applying an adhesive layer 3 consisting of an adhesive, preferably acrylic adhesive and radiation polymerizable compound, optimally urethane acrylate based oligomer having 300-10,000 molecular weight onto the surface of the base material 2. 50-900pts. wt. urethane acrylate based oligomer is preferably blended with 100pts.wt. acrylic adhesive. A compound colorable by irradiation, etc., is preferably added also to the adhesive layer 3. EFFECT:The aimed sheet can be surely housed in a housing box without mutual contact between the sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an adhesive sheet 1-, and more particularly to an adhesive sheet for sticking a wafer used when cutting and separating a semiconductor wafer into small pieces.

Technical aspects of the technology and its problems Semiconductor wafers such as silicon and gallium arsenide are manufactured in a large diameter state, and these wafers are diced into small element pieces and then undergo the next process, the mounting process. It has been moved. 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 conventionally consisted of a base material made of a general-purpose composite film made of polyvinyl chloride, polypropylene, etc., and an acrylic adhesive layer provided on the surface of the base material. things have been used. However, in such an adhesive sheet with an acrylic adhesive layer, the diced semiconductor
There was a problem in that when each chip 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 adhesive is applied partially to the surface of the sealing material, rather than entirely, to reduce the amount of adhesive applied. . 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. A new problem has arisen in that the wafer chips come off from the adhesive sheet during the cleaning, drying, and egispanning steps that are performed subsequent to the dicing step.

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 Egis banding process, and that it has enough adhesive strength to prevent the adhesive from adhering to the 1-que chip during pick-up. .

As such an adhesive sheet, JP-A-60-196.
No. 956 and Japanese Unexamined Patent Publication No. 60-223゜139 disclose a low molecular weight compound having at least two photopolymerizable carbon-carbon two-handed bonds in the molecule that can be formed into a two-dimensional network by light irradiation on the plugging material surface. A pressure-sensitive adhesive sheet coated with a pressure-sensitive adhesive made of a compound has been proposed. According to the publication, low molecular weight compounds having at least two photopolymerizable carbon-carbon double bonds in the molecule include trimedylolpropane acrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. 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.

Consisting of a low molecular weight compound having at least two or more photopolymerizable carbon-carbon double bonds in the molecule on a base material made of a general-purpose polymer film such as polyvinyl chloride or polypropylene as exemplified above. The present inventors have discovered that the pressure-sensitive adhesive sheet coated with the pressure-sensitive adhesive layer has the following problems. In other words, tension is applied to the adhesive sheet when a wafer is pasted onto the adhesive sheet or when the pasted wafer is diced, so the base sheet stretches and becomes sticky after the wafer dicing process is completed. It was discovered that there was a problem in that the sheet was bent, and when the adhesive sheet was stored in a wafer box to be transferred to the next process, it could not be stored or the stored wafers would come into contact with each other. It was done. Furthermore, when wafers stuck on adhesive sheets are irradiated with radiation such as ultraviolet rays after the dicing process, new stretching or bending may occur in the adhesive sheet, or the wafers may be warped during the wafer dicing process as described above. Because the adhesive sheet may remain stretched or bent, it may not be possible to store the adhesive sheet in the wafer box used for transporting the adhesive sheet from the radiation irradiation process to the next pick-up process, or the wafers may It was found that there is a problem that the two come into contact with each other.

The present inventors conducted a thorough investigation to solve the problems associated with the conventional technology, and found that the above problems could be solved at once by using a specific polymer film as the base sheet of the adhesive sheet. The present invention has been completed based on the discovery that the problem can be solved.

The present invention is an attempt to solve the problems associated with the prior art as described above, and is intended to prevent stretching or deflection of the sealing material sheet during the wafer dicing process after adhering the wafer to the adhesive sheet. Furthermore, new elongation or deflection does not occur when the adhesive sheet to which the diced wafer is attached is irradiated with radiation. An object of the present invention is to provide a pressure-sensitive adhesive sheet that, even if a slight elongation or deflection occurs, the deflection disappears through a radiation irradiation process, and the pressure-sensitive adhesive sheet can be reliably stored in a storage box.

+R Requirements of the Invention The adhesive sheet 1- for pasting wafers according to the present invention is obtained by applying an adhesive layer consisting of an adhesive and a radiation-polymerizable compound on the base material surface.
This adhesive sheet for wafer attachment is characterized by using a crosslinked film as a base material.

Since the adhesive sheet for attaching wafers according to the present invention uses a crosslinked film as the base material, the adhesive sheet does not bend due to stretching when wafers are attached to the adhesive sheet and diced. No new bending occurs in the adhesive sheet when the adhesive sheet is irradiated with radiation, and even if the adhesive sheet slightly bends during the dicing process, the slight bending that occurs in the adhesive sheet due to the radiation irradiation process will not occur. disappears, and therefore, the adhesive sheets to which the wafers are attached can be reliably stored in the storage box, and the stored adhesive sheets do not come into contact with each other, which is a great effect. Moreover, when picking up diced wafer chips after irradiation with radiation, the base material sheet 1 is sufficiently extended during expansion, so it is possible to reliably pick up the wafer chips.

1 skin example 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 adhere 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. In the present invention, a crosslinked film is used as the group vj2.

The crosslinked film used in the present invention is obtained by irradiating a film having crosslinking points with radiation or by chemically crosslinking the film by adding an initiator for the crosslinking reaction to the raw material polymer of the film.

As such a crosslinked film, a crosslinked polyolefin film, a crosslinked polydiene film, a crosslinked ethylene vinyl acetate copolymer film, a crosslinked polyolefin polydiene copolymer film, etc. can be specifically used.

As will be described later, the adhesive sheet of the present invention is irradiated with radiation such as EB or U when it is used, so the crosslinked film used in the present invention is EB@12J
It does not need to be transparent when used with UV point irradiation, but it is a transparent material when used with UV point irradiation! ″′It is necessary.

The cross-linked film used as such a base material is subjected to an expanding process when picking up diced wafer chips, but it has sufficient stretchability during this expanding process to ensure that the wafer chips are picked up reliably. can be written.

An adhesive layer 3 is provided on the base material 2 as described above, and this adhesive layer 3 is formed including an adhesive and a radiation-polymerizable compound.

Conventionally known adhesives can be widely used, but
Acrylic pressure-sensitive adhesives are preferred, and specifically, acrylic polymers selected from homopolymers and copolymers containing acrylic acid esters as the main component unit and other functional single polymers. and mixtures of these polymers. For example, as an acrylic ester of Nanatsuma,
Ethyl methacrylate, butyl methacrylate, 11-2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, etc.
Furthermore, it is also possible to preferably use acrylic acid in place of the above-mentioned methacrylic acid.

Furthermore, in order to improve the compatibility with the oligomers described below, a hexamer such as methacrylic acid, acrylonitrile, and vinyl acetate may be copolymerized.

The molecular weight of the acrylic polymer obtained by polymerizing these seven polymers is 2.0×10 5 to 10.0 crosslinked O, preferably 4.0 crosslinked O” to 8.0 crosslinked O”.

In addition, examples of radiation polymerizable compounds include, for example, JP-A-60
-196.956 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 are widely used, as disclosed in the Japanese Patent No. 39, C. Methylolpropane acrylate, tetramethylolmethanetetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4-butylene glycol diacrylate, 1,6-hexanediol Diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, etc. are used.

Further, as the I'i secant 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 2,4-tolylene diisocyanate, 2,6
~Tolylene diisocyanate, 1,3-xylylene diisocyanate, 1゜4-xylylene diisocyanate 1~
, diphenylmethane 4,4-diisocyanate, etc., to the terminal isocyanate urethane prepolymer which is IJ, and a (meth)acrylate having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate. , polyethylene glycol (meth)acrylate, etc. 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 number of molecular groups 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 semiconductor wafer surface is rough, no adhesive will adhere to the chip surface when picking up the r-wafer chip. In addition, when using a urethane acrylate oligomer as an hM radiation polymerizable compound, JP-A No. 60-196,9
Photopolymerizable carbon in the molecule as disclosed in Publication No. 56
Compared to the case where a low molecular weight compound having at least two carbon double bonds 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 a 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 in the range of 50 to 900 parts of biosphere per 100W opening of the acrylic adhesive. is preferred. 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 depth can be easily picked up from the adhesive sheet.

Further, if necessary, the adhesive layer 3 may contain, in addition to the above-mentioned adhesive and radiation polymerizable compound, a compound that is colored by radiation irradiation. By including a compound in the adhesive 3 that is colored by such radiation irradiation, the adhesive sheet is colored after being irradiated with radiation, and therefore the detection accuracy when detecting wafer chips with an optical sensor is improved. Therefore, malfunctions do not occur when picking up wafer chips. Furthermore, it is possible to immediately determine by visual inspection whether or not the adhesive sheet has been irradiated with radiation.

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-(ρ-tolylamino)]-7-anirite fluorane, 3-(N-(Kanotolyl)-N-methylamino]-7-anirite fluorane, 3-[8-( Kanotolyl)-N-ethylamino]-7-
Examples include anirithufluorane, 3-diedylamino-6-methyl to 7-anilitunolurane, crystal violet rough 1-ton, 4.4',4'' trisdimethylaminetriphenylmethanolylmethane, and the like.

Color developers that are preferably used with these leuco dyes include electron acceptors such as conventionally used initial polymers of phenol-pormarine resins, aromatic carboxylic acid derivatives, and activated clay. In this case, a combination of various common λl coloring agents can be used.

Such a compound that can be colored by radiation irradiation may be dissolved in an organic solvent or the like and then included in the adhesive layer, or it 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 tons, 4%, preferably 0.5 to 5% by weight. If the compound is used in an amount exceeding 10% by weight, the lj'i rays irradiated onto the pressure-sensitive adhesive sheet will be absorbed by the compound, resulting in insufficient curing of the pressure-sensitive adhesive layer, which is undesirable. If the compound is used at a concentration of less than 0.01Φ, the adhesive may not be sufficiently colored, and malfunction may occur when picking the wafer depth. I don't like the tJ.

In some cases, the adhesive layer 3 may contain a light-scattering inorganic compound powder in addition to the adhesive and the radiation-polymerizable compound as shown in + and -.

By including such a light-scattering inorganic compound powder in the adhesive layer 3, even if the surface of the adherend such as a semiconductor wafer turns gray or black for some reason, the adhesive sheet will not be exposed to radiation such as ultraviolet rays. When irradiated, the adhesive strength is sufficiently reduced in the gray or blackened areas, and the adhesive (=j) does not adhere to the surface of the wafer when picking up the wafer chip. The effect is that sufficient adhesive strength is maintained before the irradiation.

When this light-scattering inorganic compound is irradiated with radiation such as ultraviolet rays (UV) or electron beams ([B),
Compounds that can diffusely reflect this radiation include silica powder, alumina powder, silica-alumina powder, mica powder, and the like. It is preferable that this light-scattering inorganic compound is one that almost completely repels the radiation as described above;
A material that absorbs radiation can also be used.

The light-scattering inorganic compound is preferably in powder form, and the particle size is preferably about 1 to 100 μm, preferably about 1 to 20 μm. This light-scattering inorganic compound is desirably used in the adhesive layer in an amount of 0.1 to 10% by weight, preferably 1 to 4% by weight. If the compound is used in an adhesive layer in an amount exceeding 10%, it is not preferable because the adhesive force of the adhesive layer may decrease.
.

If the amount is less than 1% by weight, if the semiconductor wafer surface becomes gray or black, fJ'i. Even if the wafer is irradiated with radiation, the adhesive strength will not be sufficiently reduced and the adhesive will remain on the wafer surface when it is picked up, which is not preferable.

The adhesive sheet obtained by adding a light-scattering inorganic compound powder to the adhesive layer can be used even when the surface of a semiconductor has turned gray or black for some reason. It is thought that the reason why the adhesion force is sufficiently reduced even in this part when the blackened part is irradiated with radiation is considered to be as follows.

The adhesive sheet 1 according to the present invention has an adhesive layer 3 on the right side, but when this adhesive layer 3 is irradiated with radiation, the radiation polymerizable compound contained in the adhesive layer 3 is cured. The adhesive force will be reduced. However, gray or black areas may appear on the semiconductor wafer surface for some reason. In such a case, if radiation is applied to the adhesive layer 3, the radiation will pass through the adhesive layer 3 and reach the wafer surface, but if there are gray or black areas on the wafer surface, this will occur. The radiation is absorbed and no longer reflected. For this reason, the radiation that should originally be used for curing the adhesive layer 3 is absorbed by the gray or blackened areas, causing the adhesive layer to harden.
curing will be insufficient, and the adhesive peak will not be sufficiently reduced. Therefore, it is thought that the adhesive adheres to the chip surface when the wafer depth is picked up.

However, when a light-scattering inorganic compound powder is added to the adhesive layer 3, the irradiated trl rays collide with the compound and change direction before reaching the wafer surface. Therefore, even if there is a gray or black area on the wafer depth surface, the diffusely reflected q4 radiation will penetrate sufficiently into the area above this area, and therefore this gray or black area will also be fully absorbed. harden. Therefore, by adding light-scattering inorganic compound powder to the adhesive layer, even if there is a gray or black area on the semiconductor wafer surface for some reason, the adhesive layer will not harden in this area. This prevents adhesive from adhering to the chip surface when the wafer chip is picked up.

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-xylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4-diisocyanate, diphenylmethane-2,4-diisocyanate, 3-methyldiphenylmethane diisocyanate,
Hexamethylene diisocyanate, inphorone diisocyanate, cyclogysicylmethane-4,4-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate, etc. are used.

In the case of Uv@mugi, Uv is added to Zaraani's above adhesive.
By incorporating an initiator, the polymerization curing time and UV irradiation due to UV illumination can be reduced.

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 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, as shown in FIG. A semiconductor wafer A to be diced is attached to the upper surface of the adhesive layer 3 as shown in FIG. 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 depth is picked up from the adhesive sheet and mounted on a predetermined base. At this time, as shown in FIG. EB
The adhesive layer 3 of the adhesive sheet 1 is irradiated with ionizing radiation B such as ), 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.

It is preferable that the adhesive sheet 1 is irradiated with radiation from the side of the base material 2 on which the adhesive layer 3 is not provided. Therefore, as mentioned above, when using Uv as the tJ3LQA line, the base material 2 needs to be light-transparent, but when using EB as the radiation, the base material 2 does not necessarily have to be light-transparent. There isn't.

In this way, wafer chip A1. After irradiating the adhesive layer 3 in the area where A2/old... is provided to reduce the adhesive strength of the adhesive layer 3, the adhesive sheet 1 is transferred to a pickup station (°not shown). Then, as shown in FIG. 5, the adhesive sheet 1 is lifted in accordance with the conventional method and pushed up from the bottom surface of the base material 2, and the chip A to be picked up is punched with the needle punch 5. , this depth △
1... is picked up using air tweezers 6, for example, and mounted on a predetermined base. In this way, the wafer depth A1. A2...
When the wafer is picked up, the wafer can be picked up into the tube without any adhesive being adhered to the surface of the wafer depth, and good quality chips 17 without contamination can be obtained.

Note that radiation irradiation can also be performed in a pick-up station.

It is not necessarily necessary to irradiate the entire surface of the wafer A to which the wafer A is attached at once, and it is also possible to irradiate the entire surface of the wafer A several times. A2...111M
For each wafer chip A1. A
It is also possible to pick up the items in sequence by pushing up 2.... FIG. 6 shows a modification of the above-mentioned radiation irradiation method. In this case, the interior of the push-up needle rod 5 is made hollow, and the GEI ray generation source 7 is provided in the hollow part. It is designed to be able to carry out the shooting and picking up at the same time, and in this way, the device can be installed in the cylinder, and at the same time, the picking up operation time can be shortened.

■ Clothing 4 Since the wafer adhesive sheet according to the present invention uses a crosslinked film as the base, the adhesive sheet does not bend due to elongation when a wafer is attached to the adhesive sheet and diced. Moreover, when the adhesive sheet is irradiated with radiation, no new bending occurs in the adhesive sheet, and even if the adhesive sheet is slightly bent during the dicing process, when the film is irradiated with radiation Q1 radiation, the sheet becomes sticky. The slight bending caused by the wafer is eliminated, so that the adhesive sheet to which the wafer is attached can be reliably stored in the storage box, and there is a great effect that the stored adhesive sheets do not come into contact with each other. Moreover, when picking up the wafer chips diced into the radiation-irradiated QAi*, since the wood sheet is sufficiently stretched during expansion, the wafer chips can be picked up reliably.

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

100 parts by weight of Niacrylic adhesive (copolymer of n-butyl acrylate and acrylic acid) and molecular weight 3000-10
000 urethane acrylate oligomer 100ff
A pressure-sensitive adhesive composition was prepared by mixing 1 part of lff, 25 parts of a curing agent (diisocyanate type), and 10 m part of a UV curing reaction initiator (benzophenone type).

This pressure-sensitive adhesive composition is applied to a base material to a thickness of 50 μm, and then applied to one side of cross-linked polyethylene cross-linked by an electron beam to a dry thickness of 1 μm.
The pressure-sensitive adhesive sheet of the present invention was prepared by coating the adhesive sheet to a thickness of 0 μ7n and heating it at 100° C. for 1 minute.

After attaching a silicon wafer to the resulting adhesive sheet and performing dicing, the state of the sheet was visually checked, and no bending or similar was observed. Also, everything went smoothly when it was stored in the storage box. Furthermore, the sheets did not come into contact with each other after being stored. Similarly, after irradiating with ultraviolet rays to reduce the adhesive strength,
Storage into the storage box was carried out smoothly without any bending, and no contact between the adhesive sheets was observed. Also, when picking up after this, the sensor was accurately positioned and the pickup was performed smoothly.

An adhesive sheet was formed in the same manner as in Example 1, except that uncrosslinked polyethylene, which had not been irradiated with radiation, was used as the sealing material in Example 1, and a silicon wafer was attached to it.
When the dicing process and ultraviolet irradiation were performed, M+A was bent after each process, and the adhesive sheets came into contact with each other when stored in a storage box, causing trouble. Additionally, a malfunction occurred during pickup, which appeared to be caused by deflection.

[Brief explanation of drawings]

FIGS. 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... Peeling sheet, A... Wafer, B... Radiation.

Claims (3)

[Claims] (1) A pressure-sensitive adhesive sheet for wafer bonding comprising a base material surface coated with a pressure-sensitive adhesive layer consisting of an adhesive and a radiation-polymerizable compound, characterized in that a crosslinked film is used as the base material. adhesive sheet. (2) The adhesive sheet according to claim 1, wherein the crosslinked film is a crosslinked polyolefin film. (3) The adhesive sheet according to claim 1, wherein the crosslinked film is a crosslinked polyethylene film.