JPH07263381A - Adhesive film for dicing semiconductor wafer, and dicing method using the same - Google Patents

Abstract

PURPOSE:To provide an adhesive film for dicing a semiconductor wafer, which holds a semiconductor wafer firmly at the time of dicing and can easily be peel when picking up a semiconductor chip after dicing, and its dicing method. CONSTITUTION:The sticking and dicing are performed at the fusing point (the heat absorption peak temperature measured with DSC - graduation scanning calorimeter-) or over of the pressure sensitive adhesive of an adhesive for dicing of a semiconductor wafer, and the semiconductor chip after dicing is peeled at a fusing point or under. The adhesive strength varies three times or more, depending upon whether it is over or under the fusing point, and 50wt.% or more of the material monomers constituting the adhesive are constituted of acrylic acid ester, methacrylic acid ester, or the like, which has ester of 12 or over in the number of carbons.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive film for dicing a semiconductor wafer and a dicing method using the same. In particular, when the semiconductor wafer is diced, the semiconductor wafer and the adhesive film for semiconductor wafer dicing are firmly attached to each other, and when the semiconductor chip is peeled from the adhesive film for semiconductor wafer after dicing, the adhesive film for semiconductor wafer dicing and the adhesive film for dicing are used. It is related to the dicing method used.

[0002]

2. Description of the Related Art A general dicing method for a semiconductor wafer is performed as follows. Stick the adhesive film for dicing on the back surface of the semiconductor wafer on which the electronic circuit is formed and fix it, and cut the semiconductor wafer for each semiconductor chip while water-cooling the rotary round blade and the semiconductor wafer with a dicer equipped with the rotary round blade ( Dicing). Finally, each semiconductor chip is separated and picked up from the dicing adhesive film and mounted on a lead frame or the like. The characteristics required of the pressure-sensitive adhesive film for dicing from such steps are the contradictory adhesive characteristics that the semiconductor wafer can be strongly fixed during dicing and the semiconductor chip can be easily peeled off during pickup. That is, at the time of dicing, the rotary round blade is cooled to about 1 k at all times to remove the semiconductor wafer shavings generated by cutting.
Water pressure of gf / cm ² or more is applied to the semiconductor wafer.
At this time, the pressure-sensitive adhesive film for dicing needs a strong adhesive force so that the semiconductor wafer is not peeled off by the water pressure and the rotating circular blade. On the other hand, at the time of picking up, one semiconductor chip is lifted from the side of the adhesive film for dicing with a needle and at the same time, the semiconductor chip is picked up with a suction jig. At this time, if the adhesive force of the adhesive film for dicing is too strong, the semiconductor chip cannot be picked up. In recent years, this problem has become important due to the increase in size of chips accompanying the high integration of electronic circuits.

[0003]

As a means for solving this problem, the following method has been proposed. JP-A-5
1-90565, JP-A-51-114864, JP-A-61-23336 and the like, when picking up a semiconductor chip, the pressure-sensitive adhesive film for dicing and the semiconductor chip are kept at 0 ° C to -50 ° C. A method is disclosed in which the adhesive strength is reduced by cooling and peeling is performed. In this method, the semiconductor chip after dicing is heated to 0 ° C.
The disadvantage is that the temperature must be extremely low at -50 ° C, and a large-scale cooling device and a large amount of energy are required. JP-A-60-196956, JP-A-60-
No. 223139 discloses that an adhesive of a pressure-sensitive adhesive film for dicing is provided with light and electron beam curability, strongly supports a semiconductor wafer uncured during dicing, and irradiates ultraviolet rays before picking up the adhesive. A method of lightly peeling by three-dimensionally network hardening is shown. This method requires that the adhesive is expensive, requires light and electron beam irradiation equipment, and the adhesive film for dicing is
The disadvantage is that it requires careful storage and process management, such as blocking light until the end of dicing.

[0004]

Means for Solving the Problems The present inventors have found that during dicing, the semiconductor chip is firmly bonded to the semiconductor wafer, and after dicing, the semiconductor chip can be easily and inexpensively and lightly peeled off without using a special device. As a result of intensive studies on the pressure-sensitive adhesive film, the present invention has been accomplished. That is, the present invention is
Consists of adhesive and plastic film substrate, melting point of adhesive (DSC (differential scanning calorimeter, heating rate 10 ° C / min)
Adhesive strength at temperatures above the endothermic peak temperature measured in
The present invention relates to a pressure-sensitive adhesive film for semiconductor wafer dicing, which is used for fixing when dicing a semiconductor wafer having a bonding strength of 3 times or more at a melting point (endothermic peak temperature measured by DSC) or less, and a dicing method using the same.

The plastic film substrate used in the present invention includes polyethylene, polypropylene, polyester, polyvinyl chloride, ethylene-vinyl acetate copolymer and the like, and may be a single layer or a laminate of two or more layers. There is no particular limitation on the type and structure of the film. Its thickness is 6-1
00 μm is preferable. The plastic film substrate is preferably subjected to either or both physical and chemical treatments for the purpose of enhancing the adhesion with the adhesive to be applied later. Examples of the physical treatment include sandblasting and polishing treatment, and examples of the chemical treatment include corona treatment, plasma treatment, primer treatment, coupling agent treatment and the like, but are not limited thereto. Corona treatment is more preferable in terms of the balance between treatment and effect.

The pressure-sensitive adhesive is a comb polymer having a side chain of 8 or more carbon atoms. The comb polymer is one in which one chain has a large number of branches, and a monomer constituting the polymer has a side chain having 4 or more carbon atoms. In the present invention, a side chain having 8 or more carbon atoms is used. Examples thereof include poly (α-olefin), poly (alkyl acrylate), poly (alkyl methacrylate), poly (vinyl alkyl ether), poly (vinyl alkyl ester), poly (alkyl styrene) and the like. Among these, polymers of acrylic acid derivatives or methacrylic acid derivatives are preferable, and 50% by weight or more of the monomers constituting these polymers have 8 carbon atoms.
More preferably, it is an alkyl ester having 12 or more carbon atoms. More preferably, these amounts are 60% by weight or more. This is because when the carbon number of the ester is 8 or more, the side chain crystallinity is exhibited and the first-order transition point (melting point) is observed. Examples of these monomers include dodecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, octadecyl acrylate, docosane acrylate, dodecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, docosane methacrylate, etc. Is mentioned. The alkyl ester may be linear or branched. When the amount of these long-chain ester monomers is less than 50% by weight of all the monomers, the change in the adhesive force around the melting point of the polymer (endothermic peak temperature measured by DSC) becomes slow, which is not preferable. The reason why the adhesive strength before and after the melting point is 3 times or more is that the firm fixing and peeling property of the semiconductor wafer are taken into consideration.
Adhesion at temperatures 10 ° C apart is used. Around melting point 10 ℃
This is because the adhesive force is stabilized even when the adhesive force changes slowly depending on the adhesive composition. The type of long-chain ester monomer is selected according to the desired melting point (endothermic peak temperature measured by DSC). The melting point is preferably 0 ° C. or higher, more preferably 10 ° C. or higher. If the temperature is 0 ° C. or lower, it is necessary to set the temperature to 0 ° C. or lower when picking up the semiconductor chip from the adhesive film for semiconductor wafer dicing, which requires a special device and a large amount of energy for cooling, which is not preferable.

Further, a general-purpose acrylic acid or methacrylic acid derivative may be used to impart desired properties such as introduction of a functional group and control of adhesive strength. Examples of these monomers include acrylic acid, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, acrylic acid amide, glycidyl acrylate, 2-hydroxypropyl acrylate, 2-cyanoethyl acrylate, acrylonitrile, and acrylic. Methyl acid, ethyl acrylate, -n-butyl acrylate, isobutyl acrylate and the like can be mentioned. The same applies to the methacrylic acid derivative. Two or more kinds of homopolymers may be blended or copolymerized within a range that does not impair the object of the present invention. Rather, it is preferable to modify so as to satisfy the desired properties.

The acrylic acid or methacrylic acid derivative polymer used for the pressure-sensitive adhesive is polymerized by a conventional method, and the polymerization method, solvent, polymerization initiator and the like are not limited, but the weight average molecular weight thereof is 300,000 in terms of polystyrene. The range is preferably from 1.5 to 1.5 million, more preferably from 500,000 to 1.5 million. When the molecular weight is 300,000 or less, the cohesive force of the pressure-sensitive adhesive is poor and cohesive failure easily occurs, which is not preferable. Further, even if it exceeds 1.5 million, the adhesive strength to the adherend becomes too weak and it becomes difficult to dissolve in a general-purpose solvent, which is not preferable. Additives such as tackifiers and colorants can also be added to the adhesive.

An adhesive film for semiconductor wafer dicing is obtained by uniformly applying an adhesive to the above-mentioned plastic film substrate and drying it. There is no particular limitation on the coating, conveying and drying methods. The coating thickness should be determined in consideration of the adhesive force with the semiconductor wafer, and is preferably 1 to 15 μm.
m, and more preferably 3 to 10 μm.

The thus obtained adhesive film for semiconductor wafer dicing is attached to the semiconductor wafer. The sticking temperature is preferably not lower than the melting point of the adhesive and is 1 higher than the melting point.
It is more preferable if it is higher than 0 ° C. There is no limitation on the sticking pressure and the sticking method. The semiconductor wafer fixed with this adhesive film for semiconductor wafer dicing is diced using a dicer. The dicing temperature is preferably equal to or higher than the melting point of the pressure-sensitive adhesive as in the case of sticking, and more preferably higher than the melting point by 10 ° C. or more. Other dicing methods are not particularly limited. Next, the diced semiconductor chip is peeled off and picked up from the adhesive film for a semiconductor wafer. The method of picking up is not limited, but the temperature is important. That is, it is necessary to set the temperature below the melting point of the pressure-sensitive adhesive, and it is more preferable to be 10 ° C. or more below the melting point. If this temperature is high, peeling cannot be easily performed, which is not preferable.

[0011]

According to the present invention, the adhesive film for semiconductor wafer dicing has a high adhesive strength at a temperature above the melting point (endothermic peak temperature measured by DSC) and a low adhesive strength below the melting point. It is a thing. Therefore, when sticking an adhesive film on a semiconductor wafer that requires high adhesive strength and when dicing, operate at a temperature above the melting point, and conversely pick up dicing semiconductor chips that require low adhesive strength. When melting, operate at a temperature below the melting point. From the viewpoint of operability, the melting point is preferably 10 ° C. to 50 ° C. For that purpose, the pressure-sensitive adhesive may have a comb polymer structure and the side chain of the polymer may have 8 or more carbon atoms. The monomer constituting the pressure-sensitive adhesive having a comb-shaped polymer structure may be any one of which acrylic acid ester or methacrylic acid ester having 50 or more% by weight of an ester having 12 or more carbon atoms or a mixture thereof.

[0012]

EXAMPLES The present invention will be described below based on examples. The present invention is not limited to the embodiments.

(Synthesis Examples 1 to 5) Azobisisobutyro with hexadecyl acrylate (hereinafter abbreviated as C ₁₆ A), ethyl acrylate (hereinafter abbreviated as EA), and acrylic acid (hereinafter abbreviated as AA) as a polymerization initiator. Nitrile (hereinafter abbreviated as AIBN) in a nitrogen stream with ethyl acetate as a solvent at 70 ° C
Polymerization was carried out for 4 hours to obtain an acrylic elastomer. For the purpose of removing residual monomers and low molecular weight substances, the acrylic elastomer solution was sufficiently stirred in about 10 times the volume of ethyl alcohol of this acrylic elastomer solution, and the precipitate was isolated. The isolated acrylic elastomer was dried in a vacuum dryer at 80 ° C. for 12 hours to obtain a dry elastomer. Solid content of this dry elastomer is 20% by weight
To obtain an acrylic pressure-sensitive adhesive. Table 1 shows the charged amount of each material, the average molecular weight and the melting point (endothermic peak temperature of DSC) of the obtained acrylic elastomer. Moreover, the measurement result by DSC (heat flow rate differential scanning calorimeter TA-50, (trade name of Shimadzu Corporation)) in the case of Synthesis Example 2 is shown in FIG. A sharp endothermic peak is seen at 26.2 ° C. (Synthesis Examples 6 to 10) Synthetic Examples 1 to 10 except that octadecyl acrylate (hereinafter abbreviated as C ₁₈ A) is used instead of C ₁₆ A.
An acrylic pressure-sensitive adhesive was obtained in the same manner as in 5. Table 1 shows the charged amount of each material, the average molecular weight and the melting point (endothermic peak temperature of DSC) of the obtained acrylic elastomer.

(Examples 1 to 8) The acrylic pressure-sensitive adhesives obtained in Synthetic Examples 1 to 4 were uniformly applied to a 25 μm biaxially stretched polypropylene film substrate using an applicator.
The solvent was removed by heating at 0 ° C for 20 minutes. This adhesive film and a polyvinyl chloride film having a thickness of 80 μm were treated at 50 ° C. and a density of 0.
Roll-lamination was performed at 5 m / min and 5 kgf / cm, and the pressure-sensitive adhesive was transferred to polyvinyl chloride to obtain a polyvinyl chloride-based pressure-sensitive adhesive film. The obtained adhesive film was attached to a silicon wafer and, as shown in Table 2, the melting point (DSC
0.5m / at higher temperature than the endothermic peak temperature measured in
Min and 6 kgf / cm for roll lamination. The silicon wafer with the adhesive film was diced using a dicer. No semiconductor chip was peeled from the adhesive film by dicing. Then, the adhesive film with the semiconductor chip was cooled to a temperature equal to or lower than the melting point of the adhesive, and each chip was peeled off. Table 2 shows the sticking temperature of the adhesive film and the silicon wafer, the adhesive force with the silicon wafer above the melting point of the adhesive (endothermic peak temperature measured by DSC), and the adhesive force with the silicon wafer below the melting point of the adhesive. .

(Comparative Examples 1-2) Adhesive films were obtained by using the acrylic pressure-sensitive adhesives synthesized in Synthesis Examples 5 and 10 in the same manner as in Examples 1-8. Table 2 shows the adhesive strength to the silicon wafer above and below the melting point.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, if a semiconductor wafer is diced using an adhesive film for dicing the semiconductor wafer, the semiconductor wafer can be firmly fixed during dicing, and a special device and a great amount of energy are required during peeling. It is possible to pick up a semiconductor chip easily and inexpensively.

[Brief description of drawings]

FIG. 1 is a DSC (differential scanning calorimeter) curve showing an example of an acrylic pressure-sensitive adhesive used in the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location C09J 7/02 JLE (72) Inventor Matsuo 2-1-1, Nishishinjuku, Shinjuku-ku, Tokyo Hitachi Kasei Industry Co., Ltd.

Claims (6)

[Claims] 1. A semiconductor wafer comprising a pressure-sensitive adhesive and a plastic film substrate, wherein the pressure-sensitive adhesive has an adhesive force at the melting point or higher of three times or more the adhesive force at the melting point or lower. Adhesive film for semiconductor wafer dicing used for fixing when dicing. 2. The melting point of the pressure-sensitive adhesive is 10 ° C. or higher.
An adhesive film for semiconductor wafer dicing as described above. 3. The pressure-sensitive adhesive film for semiconductor wafer dicing according to claim 1, wherein the pressure-sensitive adhesive is a comb polymer, and the side chain of the polymer has 8 or more carbon atoms. 4. The pressure-sensitive adhesive film for semiconductor wafer dicing according to claim 3, wherein 50% by weight or more of the monomer constituting the pressure-sensitive adhesive is composed of an acrylic acid ester or a methacrylic acid ester having an ester having 12 or more carbon atoms. 5. A semiconductor wafer and an adhesive film for semiconductor wafer dicing are attached and diced at a temperature equal to or higher than the melting point of the adhesive, and a semiconductor chip obtained by dicing below the melting point of the adhesive is used as an adhesive film for semiconductor wafer dicing. A dicing method for peeling and picking up. 6. A semiconductor wafer and a pressure-sensitive adhesive film for semiconductor wafer dicing are attached at a temperature 10 ° C. or higher higher than the melting point of the pressure-sensitive adhesive, and dicing is performed at a temperature higher than the melting point of the pressure-sensitive adhesive to be 10 ° C. or higher than the melting point. A dicing method for separating and picking up a semiconductor chip obtained by dicing at a low temperature from an adhesive film for semiconductor wafer dicing.