JPH09310050A - Adhesive for treating wafer and adhesive sheet by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive for treating a wafer having a suitable adhesion ad useful for treatment such as polishing and dicing of the semiconductor wafer, etc., by making a crosslinking structure of an acrylic copolymer composed of a specified monomer composition to have a specific gel-content. SOLUTION: This adhesive for treating a wafer consists essentially of a copolymer obtained by polymerizing a monomer mixture comprises (i) 50-80wt.% acrylic monomer of formula I (R<1> is H or methyl; R<2> is a 2-4C alkyl), (ii) 30-10wt.% N-substituted (meth)acrylamide of formula II (R<3> is H or methyl; R<4> and R<5> are each H, an alkyl or an organic group composing a heterocyclic ring by bonding each other with N atom), (iii) 10-1wt.% monomer containing a carboxyl group or its anhydride and (iv) 20-0wt.% monomer copolymerizable with the components (i) to (iii) and has >=80% gel fraction. Moreover, the adhesive is preferably crosslinked by a polyfunctional epoxy compound or a polyfunctional isocyanate compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive for wafer processing and an adhesive sheet used for processing a semiconductor wafer or the like. Here, the processing includes polishing the surface (back surface) opposite to the pattern surface of the semiconductor wafer, dicing the semiconductor wafer into a predetermined size, and the like.
In the former, the pattern is made by attaching adhesive sheets to the pattern surface.
The surface is protected and the latter is affixed to the back surface for fixing during dicing.

[0002]

2. Description of the Related Art Semiconductor wafers have become larger and larger in recent years,
It is thin. The reason for this is to increase the number of chips taken from one wafer for increasing the size, and to reduce the size of electronic equipment that incorporates the sealing chip for reducing the thickness of the wafer. Is 100μ
It is about m to 500 μm.

If the semiconductor wafer is thinly polished as described above, the wafer is likely to be broken when the processing adhesive sheet is peeled from the wafer. The size of the chip after dicing the semiconductor wafer is 0.2 to 30 mm □, but if this size becomes large, it will be difficult to peel off from the adhesive sheet for processing, and the chip will not come off well at the time of pick-up. Defects such as scratches may occur.

In order to solve such a problem at the time of peeling, conventionally, the adhesive force of the processing adhesive sheet is set to be low, or a radiation curing type adhesive is used, and the adhesive force is irradiated by irradiation before the peeling. We have devised such that the adhesive sheet can be easily peeled off after processing such as polishing and dicing of the semiconductor wafer by reducing the above.

[0005]

However, in the above conventional device, since the adhesive force is different depending on various materials (silicon, polyimide, aluminum, etc.) and the shape of the surface of the semiconductor wafer, the peelability is changed. However, there is a problem that some types of semiconductor wafers are likely to be peeled off, but other types of semiconductor wafers are difficult to be peeled off. Therefore, it is necessary to use different wafer processing sheets. In addition, there is a problem in that the adhesive strength increases after the sticking, and the sticking is strong when peeled off, which makes the peeling difficult.

On the other hand, when the adhesive strength is set low as in the conventional case, the adhesive sheet is peeled off when the back surface is polished,
The pattern surface may be contaminated by polishing debris from the wafer, resulting in a defective wafer. In severe cases, the wafer may be broken, and the chips may be scattered by the impact of dicing during dicing. In addition, with a radiation-curable adhesive, the adhesive strength is high before irradiating the radiation, so if there is a mistake in the adhesion of the adhesive sheet, it cannot be replaced, or even if it is, it is cured. No adhesive remains on the wafer,
There was a problem that it was difficult to reproduce it as it was.

In view of such circumstances, the present invention has a suitable adhesive force capable of being replaced during wafer processing to firmly hold the wafer, and is not affected by the material and shape of the wafer surface after processing. Another object of the present invention is to provide an adhesive for wafer processing and an adhesive sheet thereof that can be easily peeled off without observing an increase in adhesive strength over time.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have used an acrylic copolymer having a specific monomer structure and have made it a specific gel. When a cross-linked structure is formed to a ratio, the wafer can be firmly held with an appropriate adhesive force that can be replaced during wafer processing, and is not affected by the material and shape of the wafer surface after processing. An adhesive agent for wafer processing and an adhesive sheet thereof that can be easily peeled off without observing an increase in the adhesive force over time, and can be stably released at a practical peeling rate of about 1 to 20 m / min. Knowing this, the present invention was completed.

That is, the present invention includes the following components a to c or components d thereof; a) General formula (1): CH ₂ ═C (R ¹ ) COOR ² (wherein R ¹ is hydrogen or a methyl group). , R ² has 2 to 14 carbon atoms
Which is an alkyl group of 50)
~ 89% by weight (In the formula, R ³ is hydrogen or a methyl group, R ⁴ and R ⁵ are hydrogen or an alkyl group, or both are bonded to each other and an organic group forming a heterocycle with the N atom). N-substituted (meth) acrylamide 30 to 10% by weight c) Carboxyl group-containing monomer or its anhydride 10
1% by weight d) The main component is a copolymer of a monomer mixture consisting of 20 to 0% by weight of a monomer copolymerizable with the above ac components, and the gel fraction is 80% or more. The present invention relates to a characteristic wafer processing pressure-sensitive adhesive and a pressure-sensitive adhesive sheet characterized by having a layer comprising the wafer processing pressure-sensitive adhesive on one surface of a substrate.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylic monomer as the component a in the present invention has, for example, R ² in the general formula (1) of butyl group, isobutyl group, isoamyl group, hexyl group,
Heptyl group, 2-ethylhexyl group, isooctyl group,
Examples thereof include esters of acrylic acid or methacrylic acid having an alkyl group such as an isononyl group and an isodecyl group. If the carbon number of R ² is less than 2, the wettability of the pressure-sensitive adhesive is lowered, the initial pressure-sensitive adhesive force immediately after attachment is insufficient, and the pressure-sensitive adhesive sheet is peeled off during polishing or dicing.
Further, when the carbon number of R ² exceeds 14, the adhesive strength tends to be poor.

The acrylic monomer as the component a is
50 to 89% by weight of the total amount of the monomers, preferably 60 to 8
One or two or more thereof are used within the range of 0% by weight. If it is less than 50% by weight, the performance as an acrylic pressure-sensitive adhesive cannot be exhibited, and if it exceeds 89% by weight, the absolute amounts of the components b and c described later are insufficient, and the desired processing such as polishing and dicing. It is not possible to obtain an adhesive sheet for wafer processing which is excellent in both the wafer holding property at the time and the peeling property after processing.

The N-substituted (meth) acrylamide as the component b in the present invention includes R ⁴ in the general formula (2),
An acyclic (meth) acrylamide in which R ⁵ is hydrogen or an alkyl group (provided that at least one of R ⁴ and R ⁵ is an alkyl group) and R ⁴ and R ⁵ are bound to each other to form a heterocycle. And cyclic (meth) acrylamide constituting the above are included, and either one or both of them are used depending on the purpose of use.

Acyclic (meth) acrylamides include
There are N, N-diethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide and the like. Also, circular (meta)
As acrylamide, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone, N-
(Meth) acryloyl piperidine, N- (meth) acryloyl pyrrolidine, N- (meth) acryloyl-4-piperidone and the like.

The N-substituted (meth) acrylamide as the component b is used in the range of 30 to 10% by weight, preferably 25 to 13% by weight, based on the total amount of the monomers, and one or more types thereof are used. . If it exceeds 30% by weight, the wettability of the pressure-sensitive adhesive is lowered, and the initial pressure-sensitive adhesive strength tends to be insufficient.
If it is less than wt%, it is difficult to obtain sufficient peelability at a practical peeling speed.

The carboxyl group-containing monomer or its anhydride as the component c in the present invention is, for example,
Acrylic acid, itaconic acid, maleic acid, crotonic acid and the like, fumaric anhydride and the like, depending on the intended use,
One kind or two or more kinds thereof are appropriately selected and used. The amount used is 10 to 1% by weight of the total amount of the monomers, preferably 8 to 2
It is good to be in the range of weight%. If it exceeds 10% by weight,
The initial adhesive strength is poor, and when it is less than 1% by weight, the cohesive strength tends to be insufficient.

The monomer as the component d in the present invention is
As long as it is copolymerizable with the monomers a to c,
For example, vinyl acetate, styrene, methyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
Examples thereof include 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, and N-vinylpyrrolidone. If necessary, this d component is 2
One or two or more thereof are used in the range of 0% by weight or less, preferably 15% by weight or less. If it exceeds 20% by weight, the adhesive property as an acrylic pressure-sensitive adhesive is unlikely to be exhibited.

The acrylic copolymer of the present invention has the above-mentioned a
~ C three components or a monomer mixture consisting of this and the d component, by a conventional method, by copolymerization by a method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method,
Obtainable.

The adhesive for wafer processing of the present invention contains the above acrylic copolymer as a main component and has a gel fraction of 80% or more, preferably 85% or more (ideally up to 100%).
It is a crosslinked structure until it becomes. Gel fraction 80
If it is less than%, the adhesive strength becomes too high, resulting in difficulty in peelability after processing, and there is a problem that adhesive residue on the adherend after peeling is fatal as an adhesive sheet for wafer processing.

The gel fraction means that about 500 mg of an adhesive agent is prepared as a sample, and this is extracted in acetone at 50 ° C. for 4 hours using a Soxhlet extractor or in toluene at room temperature. After soaking for 2 days at 130 ° C. for 1 hour, the initial weight (G ₀ ) and insoluble matter weight (G _t ) of the adhesive were calculated as [G _t / G ₀ ] × 100 (%). Is the value to be set.

The cross-linking structure of the pressure-sensitive adhesive is obtained by using a polyfunctional (meth) acrylate as an internal cross-linking agent when an acrylic polymer is obtained.
It is possible to add a polyfunctional epoxy compound or an isocyanate compound as an external cross-linking agent after the acrylic polymer is obtained. In addition, crosslinking treatment by irradiation with radiation may be performed. Preferably, a polyfunctional epoxy compound or a polyfunctional isocyanate compound is used. The polyfunctionality referred to here is bifunctional or higher.

The polyfunctional epoxy compound has two or more epoxy groups in the molecule, and is sorbitol tetraglycidyl ether, trimethylolpropane glycidyl ether, tetraglycidyl-1,3-bis. Aminomethylcyclohexane, tetraglycidyl metaxylene diamine, triglycidyl-p-aminophenol and the like are available. Polyfunctional isocyanate compounds have two or more isocyanate groups in the molecule, and include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate. is there.

These cross-linking agents may be used alone or in combination of two or more, depending on the composition and the molecular weight of the acrylic copolymer, in such a proportion that the gel fraction of the pressure-sensitive adhesive falls within the above range. At that time, in order to accelerate the reaction, a crosslinking catalyst such as dibutyltin laurate usually used for pressure-sensitive adhesives may be added.

The adhesive sheet for wafer processing of the present invention comprises a layer of such an adhesive provided on one side of the substrate to form a sheet or tape. It is desirable that a release film is laminated on the agent for protection of the agent. The thickness of the adhesive layer is 5 to 100 μm, preferably 1
It is about 0 to 40 μm.

As the substrate, a plastic film such as polyolefin resin, polyester resin, vinyl chloride resin, vinyl acetate resin, polyimide resin, or the like,
Metal foil or the like is used. These base materials may be used alone or in combination of two or more kinds, and may be those having one surface or both surfaces subjected to surface treatment such as corona treatment. The thickness of this base material is 50 to 300 μ.
m, preferably about 70 to 200 μm.

[0025]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”.

Example 1 In a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer and a stirring device, 77 parts of 2-ethylhexyl acrylate, N-
20 parts of acryloylmorpholine, 3 parts of acrylic acid, 0.15 parts of 2,2′-azobisisobutyronitrile as a polymerization initiator, 100 parts of ethyl acetate were added, and the mixture was added at 12 ° C. at 12 ° C.
Polymerization was carried out for a period of time to obtain a polymer solution. To this polymer solution, 3 parts of tetraglycidyl-1,3-bisaminomethylcyclohexane was added to 100 parts of the solid content of the polymer, and after mixing, an ethylene-vinyl acetate copolymer film having a thickness of 140 μm was prepared. It was coated on the above and dried to prepare an adhesive tape for wafer processing having an adhesive layer thickness of 15 μm. Further, the sample was coated on a release film and dried to prepare a sample for measuring the gel fraction, and this was used to measure the gel fraction of the pressure-sensitive adhesive by the method described in detail in the text.

Example 2 The monomer composition was changed to 73 parts of 2-ethylhexyl acrylate,
A polymer solution was obtained in the same manner as in Example 1 except that 10 parts of n-butyl acrylate, 15 parts of N, N-dimethylacrylamide and 5 parts of acrylic acid were used. To this polymer solution, 2 parts of tetraglycidyl-1,3-bisaminomethylcyclohexane was added to 100 parts of the polymer solid content and mixed, and then the same ethylene-vinyl acetate copolymer as in Example 1 was prepared. Adhesive tape for wafer processing with 15 μm thickness of adhesive layer after coating on film and drying.
Was prepared. Further, a sample for measuring the gel fraction was prepared in the same manner as in Example 1, and the gel fraction of the pressure-sensitive adhesive was measured using this sample.

Example 3 A polymer solution was obtained in the same manner as in Example 1 except that the monomer composition was changed to 75 parts of n-butyl acrylate, 23 parts of N-isopropylacrylamide and 2 parts of acrylic acid. It was To this polymer solution, 3 parts of tetraglycidyl-1,3-bisaminomethylcyclohexane was added to 100 parts of the polymer solid content, mixed, and then coated on a polyester film having a thickness of 100 μm and dried. The adhesive tape for wafer processing with an adhesive layer thickness of 35 μm.
Was prepared. Further, a sample for measuring the gel fraction was prepared in the same manner as in Example 1, and the gel fraction of the pressure-sensitive adhesive was measured using this sample.

Example 4 The monomer composition was changed to 67 parts of 2-ethylhexyl acrylate,
A polymer solution was obtained in the same manner as in Example 1 except that 10 parts of n-butyl acrylate, 18 parts of N-acryloylmorpholine, 5 parts of acrylic acid and 0.3 part of 2-hydroxyethyl acrylate were used. . In this polymer solution,
Tetraglycidyl-based on 100 parts of solid content of polymer
0.5 parts of 1,3-bisaminomethylcyclohexane and 5 parts of tolylene diisocyanate were added and mixed, and then coated on a polyethylene film having a thickness of 130 μm and dried to obtain the thickness of the pressure-sensitive adhesive layer. An adhesive tape for wafer processing having a thickness of 20 μm was produced. Further, a sample for measuring the gel fraction was prepared in the same manner as in Example 1, and the gel fraction of the pressure-sensitive adhesive was measured using this sample.

Comparative Example 1 A monomer composition was prepared by adding 87 parts of 2-ethylhexyl acrylate,
A polymer solution was obtained in the same manner as in Example 1, except that 8 parts of N-acryloylmorpholine and 5 parts of acrylic acid were used. Add 100 parts of polymer solids to this polymer solution.
1 part of tetraglycidyl-1,3-bisaminomethylcyclohexane was added to and mixed with each other, and then coated on the same ethylene-vinyl acetate copolymer film as in Example 1 and dried to give a pressure-sensitive adhesive. An adhesive tape for wafer processing having a layer thickness of 15 μm was produced. Further, a sample for measuring the gel fraction was prepared in the same manner as in Example 1, and the gel fraction of the pressure-sensitive adhesive was measured using this sample.

Comparative Example 2 A polymer solution was obtained in the same manner as in Example 1 except that the monomer composition was changed to 69 parts of n-butyl acrylate, 30 parts of N-isopropylacrylamide and 1 part of acrylic acid. It was To this polymer solution, 0.5 parts of tetraglycidyl-1,3-bisaminomethylcyclohexane and 3 parts of tolylene diisocyanate were added to 100 parts of the solid content of the polymer, and the mixture was mixed. A polyester film similar to that of No. 3 was coated and dried to prepare an adhesive tape for wafer processing having an adhesive layer thickness of 35 μm. Further, a sample for measuring the gel fraction was prepared in the same manner as in Example 1, and the gel fraction of the pressure-sensitive adhesive was measured using this sample.

The adhesive tapes for wafer processing prepared in the above Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to a holding force test, a peeling test and a mechanical peeling test in the following manner. The results and the gel fraction of the adhesive measured in each example are shown in Table 1.

<Holding power test> The adhesive tape was cut to 20
A test piece having a size of mm × 100 mm was prepared, and the test piece was attached to an adherend (silicon wafer) by pressure bonding by a method of reciprocating a 2 kg roller once. 30 minutes after application, 2
The peeling force was measured at a low pulling speed (0.1 m / min) in an atmosphere of 3 ° C. and 65% RH, and this was taken as the wafer holding force. The larger this value is, the higher the wafer retention (adhesion) is.

<Peelability Test> A test piece prepared in the same manner as the holding power test was attached to an adherend (silicon wafer, polyimide coat wafer) by pressure bonding a roller of 2 kg once. After 30 minutes of application (initial) and after storage at 40 ° C for 7 days (after storage), the practical peel force was measured at a high speed (10 m / min) pulling speed in an atmosphere of 23 ° C and 65% RH, and this was measured. It was used as an index of wafer releasability. The smaller this value is, the easier the wafer can be peeled off. In the table, "A" indicates that the adherend is a silicon wafer,
"B" is the case where the adherend is a polyimide coat wafer.

<Mechanical Peelability Test> An adhesive tape was attached to the entire surface of the silicon wafer and stored at 40 ° C. for 7 days.
A sheet peeling machine was used to machine 100 silicon wafers to which the adhesive sheet was stuck, and the number of successful peelings was counted to determine the success rate (%).

[0036]

From the results shown in Table 1, the wafer processing adhesive sheets of Examples 1 to 4 of the present invention have an appropriate adhesive force capable of being reattached in the holding force test and have a satisfactory wafer holding property. Moreover, in the peelability test, the peeling at the practical peeling speed is light, the change in the peeling force due to the type of the wafer is small, and the increase in the peeling force with time is small.
It shows excellent peelability, and it can be seen that peeling can be performed without failure even in the mechanical peelability test. On the other hand, in the adhesive sheets for wafer processing of Comparative Examples 1 and 2, it is difficult to satisfy both the holding force test and the peeling property test. Particularly, in Comparative Example 1, the peeling force changes greatly depending on the type of wafer, In Comparative Example 2, the peeling force was large, and the peeling was heavy and the failure in the mechanical peelability test was high.

[0038]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, for processing applications such as polishing and dicing of semiconductor wafers, the wafer can be firmly held with an appropriate adhesive force that can be replaced during processing. After that, without being affected by the material and shape of the wafer surface, and without increasing the adhesive force over time,
It is possible to provide a pressure-sensitive adhesive for wafer processing and a pressure-sensitive adhesive sheet thereof which can be peeled off very easily.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08F 220: 56 220: 04)

Claims (3)

[Claims] 1. The following components a to c or components thereof and d; a) General formula (1): CH ₂ ═C (R ¹ ) COOR ² (wherein R ¹ is hydrogen or a methyl group, and R ² is Carbon number 2-14
Which is an alkyl group of 50)
~ 89% by weight (In the formula, R ³ is hydrogen or a methyl group, R ⁴ and R ⁵ are hydrogen or an alkyl group, or both are bonded to each other and an organic group forming a heterocycle with the N atom). N-substituted (meth) acrylamide 30 to 10% by weight c) Carboxyl group-containing monomer or its anhydride 10
1% by weight d) The main component is a copolymer of a monomer mixture consisting of 20 to 0% by weight of a monomer copolymerizable with the above ac components, and the gel fraction is 80% or more. Characteristic adhesive for wafer processing. 2. The adhesive for wafer processing according to claim 1, which is crosslinked with a polyfunctional epoxy compound or a polyfunctional isocyanate compound. 3. A pressure-sensitive adhesive sheet, comprising a substrate and a layer comprising the pressure-sensitive adhesive for wafer processing according to claim 1 or 2 on one surface of the substrate.