JPH07230972A - Semiconductor wafer fixing adhesive tape - Google Patents

Abstract

PURPOSE:To provide a semiconductor wafer fixing adhesive tape which is kept high in rubbery elasticity even to a heavy stress, capable of expanding enough a space between chips as kept free from necking, and furthermore prevents adhesive agent from adhering to pins when a pick-up operation takes place. CONSTITUTION:An adhesive agent layer 2 is formed on a base film 3 for the formation of a semiconductor wafer fixing adhesive tape 1. The base film 3 is made of terpolymer composed of ethylene, methacrylic acid, and (metha) acrylic acid alkyl ester, wherein an ethylene content of a ternary copolymer is more than 60% by weight, and a number of carbons of an alkyl part of (metha) acrylic acid alkyl ester component is larger than 3 but smaller than 8.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a pressure-sensitive adhesive sheet for semiconductors, which is used when dicing a semiconductor wafer into chips.
The so-called dicing tape.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
When a semiconductor wafer having a circuit pattern formed thereon is cut and separated into chips, that is, so-called dicing processing, a pickup method using a radiation curable adhesive tape for fixing the wafer has been proposed. Before the semiconductor chip is moved to the mounting step, the semiconductor wafer is attached to the adhesive sheet and fixed in a fixed state and diced into chips, and after cleaning, the steps of expanding and picking up are performed. In this method, in order to prevent the chips from scattering during the dicing process, the adhesive has a strong adhesiveness as a wafer fixing adhesive force, and then is irradiated with radiation or the like to cure the radiation-curable compound and thus the adhesive. This is a method of sufficiently lowering the adhesive strength of the layer for fixing the wafer to facilitate pickup. In this case, a full-cut method that does not leave uncut wafers is generally used. In addition, there is also widely known a method of directly transferring to a pickup step without irradiating radiation after dicing, and in this method, the pressure-sensitive adhesive does not need to have a radiation curable property.
In this case, chips are prevented from scattering by using a semi-full cut method or a half cut method in which a wafer is left uncut during dicing. Further, after dicing, braking is performed from the back surface, and the chips are completely separated and transferred to the pickup process.

As shown in a longitudinal sectional view in FIG. 1, an adhesive tape 1 for fixing a semiconductor wafer comprises an adhesive layer 2 on one side of a base film 3, and as shown in FIG. The wafer 5 is attached and fixed on the adhesive layer 2 and used in the subsequent steps. In the expanding step, as shown in the vertical sectional view of FIG. 3, the end of the adhesive tape 1 to which the wafer 5 after dicing is adhered is fixed by the metal-like frame 6, and the table as shown in the vertical sectional view of FIG. In this step, the adhesive tape 1 is stretched by pushing it up with a strip-shaped pressing tool 7 to widen the intervals between the chips 5 '. Since the stress when pushed up is large, if the base film is made of a material having high crystallinity, the contact portion 8 between the adhesive tape 1 and the end portion of the pressing tool 7 has before the expanding step. It loses its rubbery elasticity. As a result, only the contact portion 8 locally expands and the thickness of the base film becomes remarkably thinner than the non-contact portion, that is, a necking phenomenon occurs, and the stress for widening the chip interval is not transmitted to the wafer (chip) portion. Will end up. The pick-up process is as shown in FIG.
This is performed by expanding the sheet-shaped pressure-sensitive adhesive tape 1 to which the diced wafer chips 5'are attached and piercing the pickup pins 9 in a state where the chip interval is widened. At this time, it is desirable that the chip intervals be uniform and wide so that the pickup can be performed accurately.

Conventionally, as a polymer used for a base film of a pressure-sensitive adhesive sheet for a semiconductor, a compound having a carboxyl group as a polymer constitutional unit as proposed in Japanese Patent Publication No. 58306/1990, or a polyethylene type 2 Original copolymers and the like are widely known, and examples thereof include ethylene-methacrylic acid, ethylene-methyl methacrylate, and ethylene-ethyl methacrylate copolymers. These have a functional group in which the carbon number of the alkyl part of the alkyl ester group is 1 or 2 such as a carboxyl group or a methyl ester group or an ethyl ester group. The base film using these polymers is stretched. However, when a wider chip interval is required, increasing the expansion stroke causes necking at the contact portion with the pressing tool shown by reference numeral 8 in FIG. 4, and the stress for expanding the chip interval is applied to the wafer part. It cannot be fully communicated, resulting in insufficient results. Also, if the stress at the time of expansion by expansion is small, the chip cannot be moved with the expansion of the tape even if necking does not occur, and only the part other than the wafer part expands, and the chip interval is sufficient. There is a problem that it does not spread. In order to solve such a problem, a substrate film including a layer employing an ionomer resin has been proposed, but the metal present in the crosslinked portion is not preferable because it promotes metal contamination of the chip. Further, in the pickup step, as shown in FIG. 5, the dicing wafer chip 5 ′ is fixed by the pick-up pin 9 and the piercing chip 5 ′ is pushed up from the back surface of the adhesive tape 1 attached. However, in the conventional adhesive tape having the adhesive layer having the constitution of the adhesive and the radiation-polymerizable compound on the base film, the adhesive adheres to the surface of the pin when pierced, and the number of times of pushing up is increased. Adhesive is often deposited on the pins. In this process, chip recognition is performed as image recognition of the chip area. Therefore, when the amount of adhesive deposited on the pin is large, when the chip that is pushed up is viewed from above, the deposit may overflow from the chip area, and a good chip may be mistakenly recognized as a defective product during image recognition. Yes, it caused a malfunction. An object of the present invention is to fix a semiconductor wafer that prevents the necking phenomenon of the adhesive tape during the expansion as described above, has the effect of sufficiently widening the chip interval, and further prevents the adhesion of the adhesive to the pickup pin at the time of pickup. Is to provide an adhesive tape for use.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a predetermined amount of ethylene, methacrylic acid, and an alkyl moiety has 3 or more carbon atoms.
A semiconductor fixing pressure-sensitive adhesive tape using a base film having a layer containing a terpolymer having the following three components of a (meth) acrylic acid alkyl ester as a polymer constitutional unit is used even for high stress. It was found that the rubber-like elasticity is maintained, the chip interval is sufficiently widened without causing necking, and further, the effect of preventing the adhesion of the adhesive to the pickup pin at the time of pickup is exerted, and based on this finding, the present invention was completed. I arrived. That is, in the present invention, in a pressure-sensitive adhesive tape for fixing a semiconductor wafer, which comprises a pressure-sensitive adhesive layer on a base film, the base film comprises ethylene, methacrylic acid and (meth) acrylic acid alkyl ester as a structural unit of a polymer. And a layer containing a terpolymer in which the content of ethylene in the polymer is 60% by weight or more and the number of carbon atoms in the alkyl part of the (meth) acrylic acid alkyl ester component is 3 or more and 8 or less. An adhesive tape for fixing a semiconductor wafer is provided. In addition, in this specification, (meth) acrylic acid alkyl ester means either acrylic acid alkyl ester or methacrylic acid alkyl ester. Radiation means light rays such as ultraviolet rays or ionizing radiation such as electron beams.

The substrate film in the pressure-sensitive adhesive tape for fixing a semiconductor wafer according to the present invention is a ternary polymer containing ethylene, methacrylic acid and a (meth) acrylic acid alkyl ester having 3 to 8 carbon atoms in the alkyl portion as a polymer constitutional unit. It is considered that the terpolymer has a layer containing a copolymer, and that this ternary copolymer has the effect of being able to sufficiently widen the chip interval during expansion. This is presumed to be as follows. That is, since the polymer constitutional unit is a ternary compound composed of three compounds, it is much more flexible than the conventional binary compound and rich in expandability which requires extensibility. Furthermore, since the ternary compound contains a (meth) acrylic acid alkyl ester having 3 to 8 carbon atoms in the alkyl portion as one of the constituent units, the number of carbon atoms in the conventional carboxyl group or alkyl portion is increased. Has a longer functional group portion than the methyl ester group or the ethyl ester group having 1 or 2. It is considered that this long functional group sterically hinders the arrangement of polyethylene chains, reduces the crystallinity, and strengthens the rubber-like elasticity, so that the effect of preventing necking can be more sufficiently obtained. When the carbon number is 9 or more, it is not preferable because it may be too soft and the base film may be broken during expansion.

Also, due to this strong rubber-like elasticity, the restoring force of the film is increased, so that a hole having a diameter larger than the pin is not formed after the pick-up pin is pierced. Therefore, at the time of picking up, all the adhesive that adheres to the pin surface is not scraped off by the base film and is not deposited on the pin, and it is possible to avoid misidentifying a good product as a defective product in image recognition.
Specific examples of the (meth) acrylic acid alkyl ester of the terpolymer include propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate,
Octyl (meth) acrylate, (meth) acrylic acid 2-
Methylpropyl, 2-ethylpropyl (meth) acrylate, 2-methylbutyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, 2-methylhexyl (meth) acrylate, 3-methylhexyl (meth) acrylate , 2-ethylhexyl (meth) acrylate, (meth)
Examples include 1,2-dimethylbutyl acrylate and the like. In the present invention, the ethylene-methacrylic acid- (meth) acrylic acid alkyl ester contained in the base film has a carbon number of the alkyl part of 3 to 8 and the terpolymer of the (meth) acrylic acid alkyl ester is an ethylene component. Is 60% by weight or more. Preferably, when the content of the ethylene component is 60 to 98% by weight, the content of the methacrylic acid component is 1 to 20% by weight, and the content of the (meth) acrylic acid alkyl ester component is 1 to 20% by weight. The effect of is most prominent. That is, when the contents of the methacrylic acid component and the (meth) acrylic acid alkyl ester component are within these ranges, the most remarkable rubber-like elasticity is exhibited. If the content of the above-mentioned two components falls below these ranges, the rubber-like elasticity gradually weakens, and conversely, if it exceeds these ranges, the rubber-like elasticity increases, but the strength decreases and the chip interval is sufficiently widened. As a result, the stress gradually decreases.

The base film of the pressure-sensitive adhesive tape in the present invention is not limited to a single layer made of the above terpolymer, but also has a multi-layer structure of a layer containing the terpolymer and a layer of a general-purpose polymer. You may In the case of a multi-layered structure, it is possible to arbitrarily select which part of the layer containing the terpolymer is used according to the required characteristics, but when strength is important, it is most preferable to use it for the central layer. desirable. The layer composed of this terpolymer is usually one layer, but it may be two or more layers. For layers other than the layer containing the terpolymer, it is possible to use a layer of a polymer such as a polyolefin or an elastomer, and specific examples of such a polymer include polyethylene and ethylene- Ethylene copolymers such as vinyl acetate copolymer, polypropylene, polybutylene,
General-purpose polymers such as ionomers, polybutadiene, polyethylene terephthalate, polybutylene terephthalate, polymethylpentene, and polyurethane can be used, and the type and layer ratio of the resin can be arbitrarily selected according to the required properties and cost. . The layer ratio is preferred because a large effect can be obtained when the ratio of the ethylene-methacrylic acid- (meth) acrylic acid alkyl ester copolymer layer is 50 to 90% of the total thickness of the base film layer. Also,
In order to prevent breakage of the base film due to the difference in strength, it is desirable to heat-bond each layer into a multilayer. Furthermore, in the step of cutting off an excessive portion of the tape protruding from the frame by, for example, a push cut after attaching the adhesive tape to the frame, in addition to the properties such as rubber elasticity, the tape is required to be easily cut. There are cases. However, if the base film has a large rubber-like elasticity, it absorbs stress and is difficult to cut. In such a case, the ethylene-methacrylic acid- (meth) acrylic acid alkyl ester terpolymer is added to a metal ion (for example,
By using a layer containing a resin ionized with an alkaline earth metal or an alkali metal), it is possible to improve the easiness of cutting without losing the rubber-like elasticity. It is considered that this is because the ionomer resin has a structure in which a carboxyl group is electrically oriented to a metal ion, and thus the orientation is easily broken. Also, this 3
When the ionomer resin of the original copolymer contains a metal ion which is relatively easy to migrate in the cross-linked portion, metal contamination of the chip due to migration may be a problem. In this case, the transfer of metal to the chip can be prevented by forming the substrate film into a multilayer structure in which a layer of a general-purpose polymer is provided between a layer containing an ionomer resin and a pressure-sensitive adhesive layer. Furthermore, the above problem can be solved by using a blend of a terpolymer and a general-purpose polymer having a relatively crystalline property. At this time, the ratio of the terpolymer is 7 in the entire layer.
If it is 5% by weight or more, the rubber-like elasticity during expansion will not be lost. As the general-purpose polymer in this case, an ethylene-based copolymer such as polyethylene or an ethylene-vinyl acetate copolymer is used.

A radiation-curable compound is used for the pressure-sensitive adhesive layer in the present invention in the case of a system in which the pressure-sensitive adhesive force is lowered by irradiation with radiation to perform pickup. This radiation-curable compound is not particularly limited, and a usual pressure-sensitive adhesive can be used. For example, 10 to 200 parts by weight of at least one compound selected from the group consisting of a cyanurate compound having a carbon-carbon double bond and an isocyanurate compound, and 100 parts by weight of a carbon-carbon double bond, relative to 100 parts by weight of an acrylic adhesive. When a pressure-sensitive adhesive containing 5 to 100 parts by weight of a linear polyester or polyol-based urethane acrylate compound having two is used, since the rubber-like elasticity of the pressure-sensitive adhesive layer after irradiation with radiation can be maintained, The effect of maintaining the rubber-like elasticity (flexibility) of the adhesive tape after irradiation is great. Furthermore, a photopolymerization initiator, for example, isopropyl benzoin ether, isobutyl benzin ether,
Benzophenone, Michler's ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, benzyldimethylketal, α-hydroxycyclohexylphenylketone, 2
When hydroxymethylphenyl propane or the like is added to the pressure-sensitive adhesive layer, the curing reaction can proceed efficiently and the fixing adhesive strength of the chip can be reduced even if the curing reaction time or the irradiation dose is small. In addition, if necessary, a radiation-curable silicone acrylate or silicone methacrylate in order to favorably reduce the fixing adhesive strength after irradiation with radiation,
Alternatively, in order to reduce the fixing adhesive strength also to the specially treated surface where the surface of the adherend wafer is coated with a metallic substance, an ion sequestering agent, tackifier, adhesion control agent, surface active agent, etc. Agents and the like or other modifiers and conventional components can be blended.

In the case of the method of transferring to the pickup step without irradiating with radiation, conventionally known adhesive layers can be widely used, for example, acrylic adhesive. Specifically, a polymer having an acrylic ester as a polymer constituent unit and an acrylic polymer such as an acrylic ester copolymer, or a copolymer with a functional monomer, and a mixture of these polymers. Is mentioned. The polymer preferably has a high molecular weight of about 500,000 to 1,000,000. The thickness of this adhesive layer is usually 5 to 2
0 μm. The present invention is not limited to the examples shown below, but can be modified in various ways.

[0011]

Embodiments will be described in detail below with reference to embodiments. Examples 1 to 4 and Comparative Examples 1 to 6 A substrate film having the following composition and layer structure was obtained by extrusion molding, one side of the film was subjected to corona treatment, and the corona treated surface was subjected to the following adhesion using a comma coater. Agent A or B
Was coated to obtain an adhesive tape. At that time, the thickness of the substrate film was 100 μm in all, the thickness of the adhesive was 10 μm, and the total thickness of the adhesive tape was 110 μm. The trade names of the resins used for the base film are collectively shown as (Note) later. A large-diameter silicon wafer is attached to the adhesive layer side of the adhesive tape, and the silicon wafer is diced into 5 × 5 mm ² chips with a dicing saw. 2 right above with a circular pressing tool
It was pushed up to a stroke of 0 mm and expanded. Necking was judged by using an adhesive tape after expansion in which the sheet thickness of the contact portion with the end portion of the pressing tool was 10% or more thinner than that of the non-contact portion, and × when it was 10% or less. . Furthermore, the average value of the chip intervals expanded by the expansion was determined. In addition, the uniformity of the chips was evaluated by determining the ratio of the vertical and horizontal intervals of the chips.
To evaluate the adhesion of the adhesive to the pin, the pickup pin was pierced into the adhesive tape 50,000 times at a constant speed, and then the pin surface was observed with a microscope (× 200). When no adhered matter was observed, it was evaluated as ◯, and when adhered matter was observed or accumulated, it was evaluated as x. To evaluate the easiness of cutting, after attaching the adhesive tape to the frame using the tape mounter,
It was cut off with a cutter attached to the tape mounter. When it was completely cut, it was marked with O, and when uncut material was observed, it was marked with X. (Adhesive) Adhesive A: Acrylic adhesive 100 parts by weight Isocyanurate compound 80 parts by weight Urethane acrylate compound 20 parts by weight Photopolymerization initiator 1 part by weight Adhesive B: Acrylic adhesive

(Base Film) Example 1 Base Film (Single Layer Structure) Ethylene-methacrylic acid- (2-methyl-propyl acrylate) terpolymer ¹⁾ Adhesive Adhesive A

Example 2 Substrate film (three-layer structure) Central layer: ethylene-methacrylic acid- (2-methyl-propyl acrylate) terpolymer ¹⁾ Both layers: low-density polyethylene ²⁾ Central layer thickness The thickness ratio was 70% of the entire layer. Adhesive Adhesive B Example 3 Substrate film (single layer structure) Blend of ethylene-methacrylic acid- (2-methyl-propyl acrylate) terpolymer ¹⁾ 80 wt% and low density polyethylene ²⁾ 20 wt% Resin Adhesive Adhesive A Example 4 Substrate film (three-layer structure) Central layer: ethylene-methacrylic acid- (2-methyl-propyl acrylate) ternary co-polymer-Zn ⁺⁺ ionomer resin ³⁾ Both layers: Low-density polyethylene ²⁾ The thickness ratio of the central layer was set to 80% of the whole layer. Adhesive Adhesive A

Comparative Example 1 Substrate film Ethylene-ethyl acrylate copolymer ⁴⁾ Adhesive Adhesive A Comparative Example 2 Substrate film Ethylene-ethyl acrylate copolymer ⁴⁾ Adhesive Adhesive B Comparative Example 3 Substrate Film Ethylene-methyl acrylate ⁵⁾ Adhesive Adhesive A Comparative Example 4 Base film Central layer: ethylene-methacrylic acid-Zn ⁺⁺ ionomer resin ⁶⁾ Both layers: Ethylene-vinyl acetate copolymer ⁷⁾ Thickness of central layer The thickness ratio was 80% of the whole layer. Adhesive Adhesive A

Comparative Example 5 Base Film Ethylene-Methacrylic Acid Copolymer ⁸⁾ Adhesive Adhesive A Comparative Example 6 Base Film Ethylene-Methyl Methacrylate Copolymer ⁹⁾ Adhesive Adhesive A (Note) 1) Mitsui DuPont Polychemical Nucler AN
42171C 2) Lexron F3 manufactured by Nippon Petrochemical Co., Ltd.
12 3) Himilan AM manufactured by Mitsui DuPont Polychemical Co., Ltd.
7316 4) Nippon Petrochemical Co., Ltd. Lexron A3
050 5) Nippon Petrochemical Co., Ltd. Lex Pearl R
B3200 6) Mimi DuPont Polychemical Co., Ltd., Himilan 17
05 7) Toruso Ultrasen U
E515F 8) Mitsui DuPont Polychemical Co., Ltd. Nucrel 09
03HC 9) Sumitomo Chemical Co., Ltd. Akulift WD
203-1

[0016]

[Table 1]

[0017]

EFFECT OF THE INVENTION By using the adhesive tape for fixing a semiconductor wafer of the present invention, the rubber-like elasticity is maintained even under high stress, the chip interval is sufficiently widened without necking at the time of expansion, and further, at the time of pickup. It is possible to prevent the adhesive from adhering to the pins.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an adhesive tape for fixing a semiconductor wafer.

FIG. 2 is a vertical cross-sectional view showing a state in which a wafer is attached to an adhesive tape for fixing a semiconductor wafer.

FIG. 3 is a vertical cross-sectional view showing a state in which the adhesive tape is fixed by a frame in the expanding step.

FIG. 4 is a vertical cross-sectional view showing a state in which the adhesive tape is stretched in the expanding step.

FIG. 5 is a partial vertical sectional view showing a pickup process.

[Explanation of symbols]

 1 Adhesive Tape 2 Adhesive Layer 3 Base Film 5 Wafer 5'Wafer Chip 6 Frame 7 Pressing Tool 8 Contact Area between Adhesive Tape and End of Pressing Tool 9 Pickup Pin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication location C09J 7/02 JLE (72) Inventor Hiroshi Nakayama 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Industry Co., Ltd.

Claims (3)

[Claims] 1. A pressure-sensitive adhesive tape for fixing a semiconductor wafer, comprising a pressure-sensitive adhesive layer on a base film, wherein the base film comprises ethylene, methacrylic acid and (meth) acrylic acid alkyl ester as a structural unit of a polymer. And a layer containing a terpolymer in which the content of ethylene in the polymer is 60% by weight or more and the number of carbon atoms in the alkyl part of the (meth) acrylic acid alkyl ester component is 3 or more and 8 or less. An adhesive tape for fixing a semiconductor wafer, which is characterized in that 2. The adhesive tape for fixing a semiconductor wafer according to claim 1, wherein the base film has a layer containing an ionomer resin obtained by crosslinking the terpolymer with metal ions. 3. The adhesive tape for fixing a semiconductor wafer according to claim 1, wherein the base film has a multi-layer structure having a layer containing an ionomer resin obtained by crosslinking the terpolymer with metal ions.