JP2000234079A - Sheet for processing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet for processing semiconductor wafer with high initial adhesion and excellent in stripping workability after use and having an adhesive layer which does not stain the surface of the semiconductor after stripping. SOLUTION: A sheet for processing semiconductor wafer has an adhesive layer on one side of the substrate film. The adhesive layer comprises a pressure- sensitive adhesive and an adhesive composition containing 1-30 wt.% of a side chain crystallizable polymer, wherein the polymer contains an acrylate and/or a methacrylate having a linear alkyl group with 16 or more carbon atoms as a side chain and the composition has an adhesive strength on stainless steel at 23 deg.C of 200 g/25 mm or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer processing sheet temporarily used for transporting, processing, preventing contamination and protecting semiconductor wafers.

[0002]

2. Description of the Related Art In general, a semiconductor integrated circuit (semiconductor IC) chip is formed by slicing a single crystal of silicon or the like into a semiconductor wafer, incorporating an integrated circuit on one surface thereof, forming a semiconductor IC, and then backing the semiconductor IC. Is manufactured by polishing, thinning, dicing into chips, and washing, drying, expanding, and pickup. In the above polishing step, it is general to reduce the thickness to about 100 to 600 μm using a polishing machine.

In these steps, a protective material (semiconductor wafer processing sheet) is previously provided on the circuit pattern forming surface in order to prevent the semiconductor wafer from being damaged and the circuit pattern forming surface from being contaminated and damaged by polishing debris. After being bonded and subjected to necessary processing such as backside polishing, it is peeled off and sent to a wafer cleaning step or the like.

Conventionally, as a surface protective material, an adhesive film in which an adhesive layer mainly composed of natural rubber, synthetic rubber, acrylic resin or the like is provided on the surface of a base film such as a plastic film has been used. Although this adhesive film is widely used because of the simplicity of lamination, the workability when peeling the adhesive film from the surface of the semiconductor wafer is poor because the adhesive force of the adhesive layer increases with time. There is a problem that the adhesive is easily transferred onto the semiconductor wafer.

[0005] In order to solve these problems, various adhesive films have been conventionally proposed. For example, JP-A-5-156215 discloses an adhesive film in which an adhesive layer containing an acrylic resin emulsion-type adhesive and polypropylene glycol is provided on one side of a base film, and JP-A-5-198542. Japanese Patent Application Laid-Open Publication No. H11-163,009 discloses a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer containing an acrylic resin, a surfactant, and a crosslinking agent is provided on one surface of a substrate film. In these publications, the peelability after use is improved by suppressing the adhesiveness of the pressure-sensitive adhesive layer from increasing over time, and the pressure-sensitive adhesive on the semiconductor wafer surface is increased by increasing the cohesive force of the pressure-sensitive adhesive layer. The transfer is reduced.

[0006] However, although the method of suppressing the increase in adhesiveness over time has a certain effect, it has not been basically solved under working at room temperature or high temperature.
It is also difficult to balance with the adhesive strength at the beginning of use.

Japanese Patent Application Laid-Open No. 7-81118 discloses a pressure-sensitive adhesive film in which an acrylic pressure-sensitive adhesive layer whose adhesiveness can be reduced by irradiating ultraviolet rays is provided on one side of a substrate film. The adhesiveness is reduced by irradiating ultraviolet rays when peeling off. However, this method requires a device for irradiating ultraviolet rays, and thus has a disadvantage of increasing costs, and there is a possibility that an ultraviolet curing accelerator or the like contained in the pressure-sensitive adhesive layer may contaminate the surface of the semiconductor wafer.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to provide a large initial adhesive force, excellent workability after use, and a reduction in the amount of polishing dust. An object of the present invention is to provide a semiconductor wafer processing sheet having an adhesive layer that prevents intrusion and does not contaminate the surface of a semiconductor wafer after peeling.

Another object of the present invention is to provide a sheet for processing a semiconductor wafer, which has excellent adhesiveness and peeling operability after use at low cost.

[0010]

SUMMARY OF THE INVENTION A semiconductor wafer processing sheet according to the present invention is a sheet that is used by being adhered to a semiconductor wafer when processing a semiconductor wafer. A pressure-sensitive adhesive layer provided on one side of the adhesive layer, wherein the pressure-sensitive adhesive layer is formed from an adhesive composition containing a pressure-sensitive adhesive and 1 to 30% by weight of a side-chain crystallizable polymer; The chain crystallization-possible polymer is an acrylate having a linear alkyl group having 16 or more carbon atoms as a side chain and / or
Alternatively, a methacrylic acid ester is a main component, and an adhesive strength to a stainless steel plate at 23 ° C. is 50 g / 25 mm or more, thereby achieving the above object.

In one embodiment, the adhesive composition has sufficient adhesiveness to a semiconductor wafer at room temperature or higher and 45 ° C. or lower, and has a property of easily peeling off from the semiconductor wafer at 50 ° C. or higher.

[0012] In one embodiment, the side chain crystallizable polymer has a melting point that occurs over a temperature range of less than 15 ° C.

In one embodiment, the adhesive strength of the adhesive composition to a stainless steel plate when heated to 50 ° C. or higher is 10% or less of the adhesive strength to a stainless steel plate at 23 ° C.

In one embodiment, the polymer has a weight average molecular weight of 3,000 to 25,000.

In one embodiment, the processed sheet for a semiconductor wafer is a sheet for a back grinding step or a sheet for a dicing step.

The operation of the present invention is as follows.

The adhesive composition for forming the semiconductor wafer processing sheet of the present invention contains a pressure-sensitive adhesive and 1 to 30% by weight of the polymer capable of crystallizing side chains based on the adhesive composition. The side chain crystallizable polymer is mainly composed of an acrylate and / or methacrylate having a linear alkyl group having 16 or more carbon atoms as a side chain, so that the temperature can be set from an arbitrarily set temperature. If you change it slightly,
The reversibility of the polymer between crystalline and non-crystalline changes the adhesion to the semiconductor wafer significantly.

Therefore, the temperature is not less than a predetermined temperature (for example, 50 ° C.
When heated to 100 ° C.), the adhesive force of the pressure-sensitive adhesive layer rapidly decreases, so that the sheet is peeled after the circuit surface of the semiconductor wafer is protected by the sheet, or the sheet is attached to the semiconductor wafer. When the sheet is peeled off after dicing in the above, the sheet can be easily peeled from the semiconductor wafer by heating the sheet to greatly reduce the adhesiveness to the semiconductor wafer.

In particular, the use of an acrylic pressure-sensitive adhesive has an interaction with a polymer, so that at a predetermined temperature, the polymer is well dispersed in a holding agent to exhibit tackiness, By the above heating, the polymer exerts good releasability.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The substrate film used in the semiconductor wafer processing sheet of the present invention can be used to alleviate the impact when processing a semiconductor wafer, or to peel off the semiconductor wafer processing sheet by being immersed in washing water or the like. This is to prevent difficulties. Therefore, a film having good water resistance is preferably used as the base film. Examples thereof include a single layer of a synthetic resin film such as polypropylene, polyester, polyamide, polycarbonate, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene polypropylene copolymer, polyvinyl chloride, or a multilayer thereof. Body thickness is 5-500μm
Sheet and the like. The surface of the base film may be subjected to a corona discharge treatment, a blast treatment, a chemical etching treatment, a primer treatment or the like in order to increase the adhesiveness to the adhesive layer.

A pressure-sensitive adhesive layer composed of an adhesive composition described below is laminated on one surface of the substrate film.

[0022] The adhesive composition may include a side-chain crystallizable polymer having a melting point that occurs over a temperature range of less than about 15 ° C, and a pressure-sensitive adhesive. This adhesive composition exhibits adhesiveness to a semiconductor wafer and other adherends at a temperature T1 (generally a temperature of 40 ° C. to 50 ° C.), and reaches a temperature T2 higher than the temperature T1 by about 15 ° C. or more. When heated, the adhesiveness to the semiconductor wafer and other adherends is greatly reduced.

(Pressure-Sensitive Adhesive) Examples of the pressure-sensitive adhesive contained in the above-mentioned adhesive composition include the following.

Natural rubber adhesive; styrene / butadiene latex-based adhesive; thermoplastic rubber of ABA block copolymer type (A indicates thermoplastic polystyrene end block, B indicates polyisoprene, polybutadiene or poly (ethylene / butylene) Rubber intermediate block);
Butyl rubber; polyisobutylene; polyacrylate; and acrylic adhesives such as vinyl acetate / acrylic ester copolymers; copolymers of vinyl ethers such as polyvinyl methyl ether, polyvinyl ethyl ether, and polyvinyl isobutyl ether.

In particular, an acrylic pressure-sensitive adhesive made of ethylhexyl acrylate, hydroxyethyl acrylate or the like is preferred. For example, a copolymer of 80 to 95 parts by weight of 2-ethylhexyl acrylate and 5 to 20 parts by weight of 2-hydroxyethyl acrylate is exemplified.

(Side Chain Crystallizable Polymer) The side chain crystallizable polymer contained in the adhesive composition has a melting point (also referred to as a first melting transition) occurring over a temperature range narrower than about 15 ° C. An adhesive composition preferably used and containing such a polymer is disclosed in Japanese Patent Application Publication No. 6-510548.

The crystallizable polymer used in the adhesive composition can include both side chain crystallizable and main chain crystallizable polymers. The difference is that the former class of compounds contains a crystallizable side chain moiety, while the latter class is crystallizable by its skeletal structure.

As used herein, the term "melting point" refers to the temperature at which certain equilibrium processes cause a particular portion of a polymer, initially in an ordered arrangement, to become disordered. In one embodiment, preferably, the melting point of the polymer ranges from about 40 ° C to 100 ° C, more preferably, from about 40 ° C to 60 ° C. Suitably, the melting occurs rapidly, ie in a relatively narrow temperature range of less than about 10 ° C, preferably less than about 5 ° C. It is preferred that the polymer crystallizes rapidly.
In this regard, a seeding agent or crystallization catalyst may be incorporated into the polymer.

After use, it can be easily peeled off from the semiconductor wafer surface by simply heating it to a temperature slightly higher than the use temperature. The heating temperature is usually 40C to 100C, preferably 40C to 70C, and more preferably 50C.
C. to 70C.

Thus, the present invention provides a discovery that the mixing of a crystallizable polymer having certain physical and chemical properties with a pressure sensitive adhesive results in an adhesive composition having a temperature controlled variability in adhesion. Is assumed.

The most preferred side chain crystallizable polymer for the present invention contains a repeating unit having the structure of the following formula:

[0032]

Embedded image

Here, W and X are the first and second monomer units, respectively, and the monomer unit is a molecular portion which can be connected to an adjacent molecular portion (ie, can be polymerized);
And Z are independent backbone monomer units which may be any molecular part or atom, each S is an independent linking group or spacer unit and is present as necessary, and Cyt and Cy are each independently A crystallizable moiety linked directly or via a spacer unit to the backbone, wherein a, b, c and d are equal to or greater than twice the sum of the molecular weights of W, X, Y and Z Is an independent integer ranging from 0 to 1,000 in the presence of sufficient Cyt and Cy to provide a molecular weight, and the polymer has a heat of fusion (ΔHt) of at least about 20 Joules / gram. The variables a,
When b, c, and d are greater than 1, the monomer unit W;
X, Y and X are repeat units or a mixture of different monomer units. For example, if a is 100, W is
It may be styrene, acrylic acid, methylstyrene and hexadecyl acrylate in a ratio of 5: 5: 2: 5: 83. Therefore, any monomer unit of W, X, Y and X can be a mixture of polymerizable monomers.

The adhesive composition of the present invention is optionally crosslinked. Crosslinking can be performed using a known technique, for example, a crosslinking agent, heating, irradiation or the like.

The backbone of the polymer (indicated by W, X, Y and X) can be any organic structure (aliphatic or aromatic hydrocarbon, ester, ether, amide, etc.)
Or inorganic structure (sulfate, phosphazine, silicon, etc.)
It may be. The spacer linkage can be any suitable organic or inorganic unit, such as an ester, amide hydrocarbon, phenyl, ether, or inorganic salt (eg, a carboxyalkylammonium, or sulfonium or phosphonium ion pair or other known ion salt pair).
It is possible. The side chains (indicated by Cyt and Cy and optionally present S) are aliphatic or aromatic or aliphatic side chains of at least 10 carbon atoms, fluorinated aliphatic side chains of at least 6 carbon atoms, and alkyl From 8
It may be a combination of p-alkylstyrene side chains having 24 carbon atoms.

The length of each side chain portion is generally longer than 5 times the distance between side chains in the case of acrylate, methacrylate, vinyl ester, acrylamide, methacrylamide, vinyl ether and alforeffin. In the extreme case of fluoroacrylate alternating copolymerization with butanediene, the length of the side chains between branches is about twice as long. In any case, the side chain units will make up more than 50% by volume of the polymer, preferably more than 65% by volume. The comonomer added to the side chain polymer usually adversely affects the crystallinity. Small amounts of various comonomers, usually from 10 to 25% by volume, are acceptable. Small amounts of comonomers, for example,
It may be preferable to add crosslinking site monomers such as acrylic acid, glycidal methacrylate, maleic anhydride, amino functional monomers and the like.

Examples of side chain crystallizable monomers within the above ranges are described in Journal of Polymer Chemistry 10: 3347 (1972); Journal of Polymer Chemistry 10: 1657 (1972); Journal of Polymer Chemistry 9: 3367 ( 1971); Journal of Polymer Chemistry 9: 3349 (197
1); Journal of Polymer Chemistry 9: 1835 (1971); A.
C. S. 76: 6280 (1954); Journal of Polymer Chemistry 7:30
53 (1969); Acrylate, fluoroacrylate, methacrylate and vinyl ester polymers, corresponding acrylamide, substituted acrylamide and maleimide polymers described in Journal of Polymer Chemistry 17: 991 (1985) (Journal of Polymer Chemistry, Polymer Physics Academic version 18: 2197 (198
0)); Journal of Polymer Chemistry: Macromolecule Review 8:11
7-252 (1974), and macromolecules 13:12 (1980) as poly (alpha-olein) macromolecules, macromolecules 13:15 (1980) as polyalkyl vinyl ethers , Polyalkylethylene oxide, Polymer Science USSR 21: 241 (1979), macromolecule 18: 2141 (198
Alkyl phosphazene polymers, polyamino acids, macromolecules as described in 5), polyisocyanates as described in 12:94 (1979), amine-containing or alcohol-containing monomers and long-chain alkyls Polyurethanes prepared by reacting isocyanates, polyesters and polyethers, macromolecules 19: 611 (19
Polysiloxanes and polysilanes as described in J. 86); A. C. S. 75: 3326 (1953), and p-alkylstyrene polymers, and triglycerides such as tristearin or pentaerythritol tetrastearate.

Particularly preferred side-chain crystallization polymers for use herein are linear aliphatic C14-C50 (14 to 14 carbon atoms).
50) polyacrylate, linear aliphatic C14
-C50 polymethacrylate, linear aliphatic C14-C
50 polyacrylamides and linear aliphatic C14-
C50 polymethacrylamide. Most preferred in this group are linear aliphatic C16-C22 polyacrylates, linear aliphatic C16-C22 polymethacrylates, linear aliphatic C16-C22 polyacrylamides, and linear aliphatic C16-C22. C22 polymethacrylamide.

As noted above, the melting point of the crystallizable polymer selected provides a temperature range of normal use in which the composition is tacky. The amount of crystallizable polymer included in the adhesive composition surprisingly has little effect on the position or breadth of this range.

The following shows specific transition temperatures for selected side chain crystallizable polymers.

Polymer transition temperature (° C.) C16 acrylate 36 C16 methacrylate 26 C18 acrylate 49 C18 methacrylate 39 C20 acrylate 60 C20 methacrylate 50 C22 acrylate 71 C22 methacrylate 62
F. See Jordan et al., "Side Chain Crystallinity II," Journal of Polymer Science, Part A-1, 9: 33551 (1971).
Specific methods of making crystallizable polymers are also described in detail in the examples therein.

The particular molecular weight of the crystallizable polymer used is an important factor in determining how the adhesive composition of the present invention exhibits temperature-varying tack and / or adhesive bond strength. That is, a low molecular weight crystallizable polymer loses its bond strength upon heating. For example, at room temperature (2
The rate of decrease in adhesive strength when heated to 60 ° C. relative to the adhesive strength (peel strength) at 3 ° C.) is 90% or more (detailed test conditions for adhesive strength will be described later). If this property is desired, the weight average molecular weight of the polymer is 3,000.
It is preferably from 0 to 25,000, more preferably from 4,0.
00 to 15,000. When the weight average molecular weight of the polymer exceeds 15,000, the decrease in tackiness by heating is small. When the weight average molecular weight of the polymer is 3,0
If it is less than 00, the change in the adhesive force with time is large, which is not preferable.

The adhesive compositions useful herein include, in addition to one or more of the above-mentioned polymers, tackifiers (rosin, tree, polyester, etc.), antioxidants, fibrous or non-fibrous fillers, colorings It may contain conventional additives such as ingredients. An adhesive can also be included if the overall temperature sensitive properties are not significantly affected. Suitably, the amount of crystallizable polymer in the adhesive composition ranges from about 1% to about 30% by weight. More preferably, it is from 5% by weight to 20% by weight. Particularly, 5 to 15% by weight is preferable. When the content of the polymer is less than 1% by weight or more than 30% by weight in the adhesive composition, the above-mentioned effect by the polymer is not obtained.

The adhesive composition of the present invention is prepared by mixing the pressure-sensitive adhesive and the crystallizable polymer in a compatible solvent and adding optional components such as a plasticizer, tackifier, filler and the like. . Adjust the solids content to the desired viscosity and blend the mixture until homogeneous. After blending, remove air bubbles from the mixture.

The polymer preferably contains 1 to 10% by weight (particularly 2 to 6% by weight) of acrylic acid as a component for improving strength.

Preferred examples of the polymer contained in the adhesive composition are as follows.

(1) Stearyl acrylate 80-98
Copolymer with 2 to 20 parts by weight of acrylic acid, 2 to 10 parts by weight of dodecyl mercaptan (2) 5 to 90 parts by weight of docosyl acrylate, 5 to 90 parts by weight of stearyl acrylate, 1 to 10 parts by weight of acrylic acid (3) copolymer of 80 to 98 parts by weight of docosyl acrylate, 2 to 20 parts by weight of acrylic acid, and 2 to 10 parts by weight of dodecyl mercaptan The above adhesive composition ( The temperature-activated polymer composition) can be provided on the substrate film by a number of methods such as spray deposition, painting, dipping, gravure printing, and rolling. The adhesive composition can also be applied by transfer from a release sheet in the same manner as in transfer printing. The composition can be used as such or with a suitable solvent.
Or it can be applied as an emulsion or latex. The appropriate monomers and additives can be applied directly to the substrate and cured in situ by heat, radiation, or other suitable methods known to those skilled in the art.

From the viewpoint of preventing contamination during storage and distribution, the pressure-sensitive adhesive layer is used until the pressure-sensitive adhesive layer adheres to the semiconductor wafer.
It is preferable to protect the adhesive with a release film such as a polypropylene film.

The thickness of the pressure-sensitive adhesive layer is preferably 30 μm or more, particularly preferably 50 to 80 μm. If the thickness of the pressure-sensitive adhesive layer is 30 μm or more, even if the unevenness of the wafer surface is large, it can follow the surface and adhere well.

When the semiconductor wafer processing sheet of the present invention is used, for example, after the release film is peeled off from the surface of the pressure-sensitive adhesive layer, it is applied to the surface of the semiconductor wafer, that is, the surface on which the integrated circuit is incorporated. A semiconductor wafer processing sheet is attached and trimmed. Next, the back surface of the semiconductor wafer is polished. At this time, the sheet prevents polishing debris from adhering to the surface of the semiconductor wafer and prevents the semiconductor wafer from being damaged. After the polishing is completed, the debris and the like attached to the polished surface are washed away using pure water, and then the sheet is peeled off from the surface of the semiconductor wafer. Then, the surface of the semiconductor wafer is washed using pure water, and then dried. .

Further, the semiconductor wafer whose back surface is polished is
It is subjected to a dicing process so as to be divided into chips.
In the dicing step, the sheet of the present invention is attached to the surface of the semiconductor wafer, and then subjected to a pickup step, in which the sheet is separated from the surface of the semiconductor wafer.
Here, since the adhesiveness to the semiconductor wafer can be adjusted only by changing the temperature of the sheet, the adhesive force is increased at the time of dicing, and at the time of pickup, it can be easily peeled off only by heating, and Since there is no contamination on the back surface of the wafer, the cleaning step can be omitted.

As a method of heating the sheet, there is a method of heating the sheet or the holding member of the sheet by, for example, the following method.

Apply a hot iron, apply hot water, cover with a sheet heater, blow hot air (for example, a hot air blower, a dryer), blow steam, heat with high frequency, and use a lamp (infrared ray, far infrared ray). There is hit.

Specifically, it is preferable that the tape is attached to the surface of the semiconductor wafer at a temperature lower than the melting point of the polymer to be used, and after use, the tape is peeled at a temperature higher than the melting point of the polymer.

The strength on the SUS plate at the operating temperature is 50 g /
The adhesive composition is preferably prepared so as to have a thickness of 25 mm (180 degree peel strength) or more. In particular, 200 to 300 g /
25 mm. In addition, it is preferable that the peel strength is 10% or less at the melting point of the side chain crystalline polymer or higher.
That is, the adhesive strength to the stainless steel plate when the adhesive composition is heated to 50 ° C. or higher is preferably 10% or less of the adhesive strength on the stainless steel plate at 23 ° C.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. In the following, “parts” means parts by weight. A. Preparation of Polymer (Synthesis Example 1) 95 parts of stearyl acrylate, 5 parts of acrylic acid, 5 parts of dodecyl mercaptan, and 1 part of Kayaester HP-70 (manufactured by Kayaku Akzo) were mixed and stirred at 80 ° C. for 5 hours. These monomers were polymerized. The weight average molecular weight of the obtained polymer is 8,000, and the melting point is 50.
° C. (Synthesis Example 2) 92 parts of 2-ethylhexyl acrylate,
After mixing 8 parts of 2-hydroxyethyl acrylate and 0.3 parts of Trigonox 23-C70 (manufactured by Kayaku Akzo) in 150 parts of ethyl acetate / heptane (70/30), and stirring at 55 ° C. for 3 hours, The temperature was raised to 80 ° C, 700.5 parts of Kayaester HP-70 was added, and the mixture was stirred for 2 hours to polymerize these monomers. The weight average molecular weight of the obtained polymer was 600,000.

B. Production of Semiconductor Wafer Processing Sheet (Example 1) The polymers obtained in Synthesis Examples 1 and 2 were mixed at a ratio of 5 parts to 100 parts. Coronate L45 (manufactured by Nippon Polyurethane Co., Ltd.) was added as a crosslinking agent to this polymer solution in an amount of 0.5 to 100 parts of the polymer of Synthesis Example 3.
Part of a 100 μm ethylene-vinyl acetate copolymer (hereinafter referred to as EVA) film on a corona-treated surface, applied by a roll coater, and provided with a release sheet having an acrylic pressure-sensitive adhesive layer (thickness: 50 μm). A sheet for processing was obtained.

The following evaluation was performed using the obtained semiconductor wafer processing sheet. (1) Peel strength The 180-degree peel strength of the sheet is measured in accordance with JIS C2107 with respect to SU
S was measured. The measurement was performed at 23 ° C. and 60 ° C., respectively.

(2) Degree of Water Penetration from Edge of Wafer (mm) A sheet was attached to the surface of a 6-inch wafer having a pump having a height of about 90 μm on the surface so as to protrude from the edge of the wafer by about 1 mm. Then, using a grinder (manufactured by Disco Co., Ltd., back grinder DFG-82IF / 8), the sheet was cut while cooling at 23 ° C. with water at 23 ° C., and the degree of penetration of water from the edge of the wafer. Was observed.

A 6-inch wafer having no pump on the surface was tested in the same manner as described above. (3) Adhesive residue and sludge intrusion on the wafer surface The wafer is adhered to a semiconductor wafer processing sheet, the wafer is polished, and then the wafer is peeled off from the sheet surface.
The wafer surface was evaluated by visual observation and observation with a microscope (× 800).

Table 1 shows the results.

(Example 2) Coronate L45 was added as a crosslinking agent to the polymer solution obtained in Example 1 in an amount of 0.8 part relative to 100 parts of the polymer of Synthesis Example 2, except that
A semiconductor wafer processing sheet was obtained in the same manner as in Example 1. The adhesive force and contamination of the obtained semiconductor wafer processing sheet were evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 3 The same procedure as in Example 1 was repeated except that 3.0 parts of Coronate L45 was added as a crosslinking agent to 100 parts of the polymer of Synthesis Example 2 to the polymer solution obtained in Example 1.
A semiconductor wafer processing sheet was obtained in the same manner as in Example 1. The adhesive force and contamination of the obtained semiconductor wafer processing sheet were evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 To 100 parts of the polymer obtained in Synthesis Example 2 above, 0.8 part of Coronate L45 (manufactured by Nippon Polyurethane) was added as a cross-linking agent.
It was applied to the corona-treated surface of a μm EVA film by a roll coater to obtain a semiconductor wafer processing sheet with a release sheet having an acrylic pressure-sensitive adhesive layer (thickness: 50 μm).

The obtained semiconductor wafer processing sheet was evaluated for adhesion and contamination in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 To 100 parts of the polymer obtained in Synthesis Example 2, 6.0 parts of Coronate L45 (manufactured by Nippon Polyurethane Co., Ltd.) was added as a crosslinking agent.
It was applied to the corona-treated surface of a μm EVA film by a roll coater to obtain a semiconductor wafer processing sheet with a release sheet having an acrylic pressure-sensitive adhesive layer (thickness: 50 μm).

The obtained semiconductor wafer processing sheet was evaluated for adhesion and contamination in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 Using a commercially available ELEP holder (manufactured by Nitto Denko Corporation), the adhesive force and contamination of the semiconductor wafer processing sheet were evaluated in the same manner as in Example 1.
Table 1 shows the results.

[0069]

[Table 1]

In Comparative Examples 1 and 3, the peelability of the semiconductor wafer processing sheet from the semiconductor wafer surface was poor, and in Comparative Example 3, contamination of the semiconductor wafer surface was observed. On the other hand, in Examples 1 and 2, both the peeling property and the contamination after heating (60 ° C.) were excellent while increasing the initial adhesive strength (23 ° C.).

In Comparative Examples 1 and 3, the penetration of water was large because the adhesive strength was low. Comparative example 2 with high adhesive strength
Although water could be prevented from entering, adhesive residue was generated at the time of peeling. Microscopic observation showed that sludge had adhered to the portion where water had entered.

Example 4 Next, the relationship between the molecular weight of the side-chain crystalline polymer contained in the pressure-sensitive adhesive layer and the rate of decrease in the peel strength during heating of the semiconductor wafer processing sheet having the pressure-sensitive adhesive layer was described. The following experiment was performed, and is shown below.

A monomer mixture obtained by mixing 95 parts of stearyl acrylate and 5 parts of acrylic acid and changing the number of parts of dodecyl mercaptan (polymerization inhibitor) was added.
The mixture was stirred at 80 ° C. for 5 hours to be polymerized, and the weight average molecular weight was
2,000, 4,000, 8,000, 15,000,
19000 polymers were obtained (shown in Table 2 as polymers 1-5 respectively). The melting point of these polymers is 5
It was 0 ° C.

15 parts of the polymer obtained above and 85 parts of the polymer obtained in Synthesis Example 2 were mixed at a ratio of 15 parts. To this polymer solution, 0.3 part of Coronate L45 (manufactured by Nippon Polyurethane Co.) was added as a cross-linking agent based on 100 parts of the polymer of Synthesis Example 2, and this polymer solution was placed on a 50 μm surface matted polyester film (50 μm thickness). Was applied by a roll coater to obtain a sheet for processing a semiconductor wafer with a release sheet having an acrylic pressure-sensitive adhesive layer (dry thickness: 20 μm).

The obtained semiconductor wafer processing sheet is 25
The test piece was cut out into a strip having a width of mm.

Next, the pressure-sensitive adhesive layer of the test piece was pressure-bonded on a SUS plate having a polished surface of # 280 at 23 ° C. by reciprocating four times with a rubber roller (45 m width, load 2 kg). . After the application, the test piece (S) was allowed to stand for 20 minutes, and the end of the test piece (S) was peeled in the direction of 180 ° at a speed of 300 m / min, and the resistance value at that time was measured as the peel strength at 23 ° C.

Further, the test piece (S) prepared in the same manner as above was placed on a hot plate preheated to 60 ° C., and allowed to stand still for 20 minutes, and the end of the test piece (S) was removed. Peeling was performed at a speed of 300 m / min in the 180 ° direction, and the resistance value at that time was measured as a peeling strength at 60 ° C.

Table 2 shows the results.

[0079]

[Table 2]

Table 2 shows that when the molecular weight of the side chain crystalline polymer is too large, the peel strength upon heating does not decrease and the rate of decrease is low.

Example 5 Next, an experiment showing the relationship between the molecular weight of the side chain crystalline polymer contained in the pressure-sensitive adhesive layer and the change over time in the peel strength of the semiconductor wafer processing sheet having the pressure-sensitive adhesive layer. The results are shown below.

A semiconductor wafer processing sheet obtained in the same manner as in Example 4 was cut into a strip having a width of 25 mm to obtain a test piece.

The peel strength of this test piece at 23 ° C. was measured in the same manner as in Example 4.

Next, the test piece produced in the same manner as above was left in a thermostat at 60 ° C. for 2 months, and the peel strength at 23 ° C. of the test piece taken out of the thermostat was set in the same manner as in Example 4. Measured.

Table 3 shows the results. Table 3
In the above, the rate of change after 2 months of aging indicates a rate with 100 immediately after trial production.

[0086]

[Table 3]

Table 3 shows that when the molecular weight of the side-chain crystalline polymer is small, the adhesive strength is slightly reduced when the sheet is stored.

[0088]

According to the present invention, the adhesiveness to the semiconductor wafer can be adjusted only by changing the temperature of the semiconductor wafer processing sheet. In some cases, the sheet can be easily peeled off only by heating, and the cleaning step can be omitted because there is no contamination on the wafer surface. In addition, since the adhesiveness can be reduced by a change in temperature, it can be carried out at a low cost without using an expensive ultraviolet irradiating device as in the related art.

Further, during dicing, the adhesive strength is increased, and at the time of pickup, the adhesive can be easily peeled off only by heating (heating).

Particularly, when the weight average molecular weight is 3,000 to 2,
When a polymer having 5,000 side-chain crystallization is used, a sheet for processing a semiconductor wafer can be obtained which has a large decrease in tackiness upon heating and a small change in tackiness over time.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyotaka Nagai 172 Ikezawa-cho, Yamatokoriyama-shi, Nara Pref.F-term in Nara Plant (reference) DF052 DF102 DM011 EA012 JA09 JB09 LA06 LA08 MA04 MB03 MB09 NA20

Claims (7)

[Claims] Claims: 1. A sheet used by sticking to a semiconductor wafer when processing the semiconductor wafer, comprising: a base film; and an adhesive layer provided on one surface of the base film. The pressure-sensitive adhesive layer is formed from an adhesive composition containing a pressure-sensitive adhesive and 1 to 30% by weight of a side-chain crystallizable polymer;
The polymer capable of crystallizing a side chain is mainly composed of an acrylate ester and / or a methacrylate ester having a side chain of a linear alkyl group having 16 or more carbon atoms, and has an adhesive strength to a stainless steel plate at 23 ° C. of 50 g / A sheet for processing a semiconductor wafer, wherein the sheet has a thickness of 25 mm or more. 2. The adhesive composition has sufficient adhesiveness to a semiconductor wafer at room temperature to 45 ° C.
2. The semiconductor wafer processing sheet according to claim 1, wherein the sheet has a property of easily peeling off from a semiconductor wafer at a temperature of not less than ° C. 3. The method according to claim 1, wherein the side chain crystallizable polymer is at 15 ° C.
3. The semiconductor wafer processing sheet according to claim 1, having a melting point occurring over a narrower temperature range. 4. The adhesive composition according to claim 1, wherein the adhesive strength of the adhesive composition to a stainless steel sheet when heated to 50 ° C. or more is 10% or less of the adhesive strength to a stainless steel sheet at 23 ° C. A semiconductor wafer processing sheet according to any one of the above. 5. A polymer having a weight average molecular weight of 3,0.
The semiconductor wafer processing sheet according to any one of claims 1 to 4, wherein the number is from 00 to 25,000. 6. The semiconductor wafer processing sheet according to claim 1, wherein the semiconductor wafer processing sheet is a sheet for a back grinding process. 7. The semiconductor wafer processing sheet according to claim 1, wherein the semiconductor wafer processing sheet is a sheet for a dicing process.