JPH0242393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of using an adhesive sheet for semiconductor wafers, which is used to adhere to semiconductor wafers such as silicon wafers and gallium arsenide wafers.

(Prior art) Conventionally, for example, when performing dicing processing on semiconductor wafers, adhesive sheets such as acrylic adhesive are applied to the surface of a base material such as vinyl chloride or polypropylene. In this case, for example, when performing a series of processes such as dicing, cleaning, drying, expanding, picking up, and mounting a semiconductor wafer, a pressure-sensitive adhesive sheet is used in which a coating layer is formed. After an adhesive sheet is attached and the wafer is subjected to dicing, washing and drying, and expanding processes in the attached state, each chip of the wafer is picked up from the adhesive sheet for mounting processing. However, the picked wafer chips often have adhesive contamination. In order to prevent this contamination, it has been proposed to apply the adhesive partially to the adhesive sheet, rather than the entire surface, in order to reduce the amount of adhesive applied to the adhesive sheet. Although the contamination of the wafer chip surface by the adhesive is reduced to some extent, the adhesive fixation of the entire wafer chip tends to be uncertain. Additionally, in general, if the adhesive force of the adhesive is reduced to prevent the adhesive from adhering to the wafer chip during pick-up,
An adhesive with such a low adhesive strength tends to lack adhesive holding power from dicing to expanding the wafer, resulting in the problem of wafer chips falling off during these processing steps.

Therefore, it is desirable for the adhesive of the adhesive sheet to be able to sufficiently hold the wafer with a relatively large adhesive force when it is attached to the wafer, but on the other hand, it is desirable that the adhesive not remain attached to the wafer chip when it is picked up. It is desirable that the adhesive strength be strong.

Therefore, as disclosed in Japanese Patent Publication No. 58-50164, an adhesive film made by coating a transparent plastic film base material with a photo-curing adhesive is attached to an adherend, and after use, A surface protection method has been proposed in which the surface of a film base material is irradiated with ultraviolet rays to crosslink and cure the adhesive and peel it off.

To explain the case where such a surface protection method is used for semiconductor wafers, first, FIGS.
As shown in the figure, a semiconductor wafer is adhered to the coating layer b of the adhesive sheet c, which has a coating layer of the radiation-curable adhesive b formed on the substrate a side, and the semiconductor wafer is diced. Radiation e is irradiated over the entire surface of the base material a of the adhesive sheet c to which each wafer chip d of the wafer is attached to harden the radiation-curable adhesive b of the adhesive sheet c and reduce its adhesive strength. After that, push up the wafer chip d to be picked up from the bottom surface of the base material a of the adhesive sheet c using the push-up needle f using a conventional method.
In this state, the wafer chip d is picked up using air tweezers g, for example.

However, in the method described above, when picking up the wafer chip d, the base material a of the adhesive sheet c is irradiated with the radiation e over the entire surface, so that wafer chips d other than the wafer chip d to be picked up may be stuck. Since the adhesive strength of the radiation-curable adhesive b of the adhesive sheet c has also decreased, the wafer chip d, which should not be picked up, is adhered to the adhesive sheet c in an extremely unstable state. There is a problem that the wafer chip d may shift on the adhesive sheet c or fall off more easily than the adhesive sheet c.

(Problems to be Solved by the Invention) The present invention solves the problems encountered when using the conventional adhesive sheet, and ensures that only the wafer chips of semiconductor wafers in desired positions are removed without residual contamination of the adhesive on the back surface of the semiconductor wafer. The present invention provides a method for using an adhesive sheet for semiconductor wafers, which can be picked up from the adhesive sheet.

(Means for Solving the Problems) The method of using the adhesive sheet for semiconductor wafers of the present invention is to attach the adhesive sheet, which is formed by forming a coating layer of a radiation-curable adhesive on the base material surface, to the back side of a semiconductor wafer. After dicing the semiconductor wafer, the base material surface of the adhesive sheet to which the wafer chips of the semiconductor wafer are attached is irradiated with radiation from a push-up needle rod that also serves as a radiation irradiation tube to determine the radiation irradiation position. The present invention is characterized in that the adhesive strength of only the adhesive of the adhesive sheet is reduced, and the wafer chips are subjected to a pick-up process.

(Example) First, the pressure-sensitive adhesive sheet used in the method of the present invention will be explained. The shape of the adhesive sheet is tape-like,
No matter the shape, such as a label. The base material is preferably one that has low electrical conductivity, water resistance, and heat resistance, and a synthetic resin film is particularly suitable. In addition, as described later, when using the adhesive sheet, it is necessary to use an electron beam (EB)
In the case of EB irradiation, the substrate does not need to be transparent; however, in the case of UV irradiation, it needs to be a transparent material.

In addition, if it is necessary to perform an expanding process after dicing a semiconductor wafer, a synthetic resin film that is stretchable in the length and width directions, such as vinyl chloride or polypropylene, can be used as the base material, as in the past. For semiconductor processing that does not require such an expanding process, any non-stretchable substrate can also be used.

The radiation curable adhesive (hereinafter simply referred to as "curable adhesive" for convenience) applied to the substrate surface is preferably an adhesive made of an acrylic adhesive mixed with a urethane acrylate oligomer.
The coating method on the base material surface may be either full-surface coating or partial dot-like coating depending on the type and formation of the semiconductor wafer.

Specifically, the acrylic adhesive constituting the curable adhesive is an acrylic polymer selected from homopolymers and copolymers containing acrylic acid ester as a main monomer unit, and other functional materials. copolymers with monomers and mixtures of these polymers. For example, monomer acrylic esters include ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, etc. Examples include things that have been replaced with .

In addition, as a urethane acrylate oligomer, a (meth)acrylate having a hydroxyl group is reacted with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound such as a polyester type or polyether type with a polyvalent isocyanate compound. It has one or more carbon-carbon double bonds. For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, N-methylolacrylamide, polyethylene glycol acrylate, etc. and polyvalent isocyanate compounds, such as 2,4-tri Urethane group-containing compound synthesized from diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane 4,4'-diisocyanate, etc. The following compounds are mentioned.

Therefore, the mixing ratio of acrylic adhesive and urethane acrylate oligomer provides a high initial adhesive strength, and at the same time, the adhesive strength decreases significantly after radiation irradiation, almost disappearing, and furthermore, the radiation irradiation time is shortened. If possible, it is preferable that the urethane acrylate oligomer be in the range of 51 to 300 parts by weight per 100 parts by weight of the acrylic pressure-sensitive adhesive.

Incidentally, when an isocyanate curing agent is mixed into the above-mentioned compounded composition, the initial adhesive strength can be increased. As the curing agent, polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,
1,3-xylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane 4,
4′-diisocyanate, diphenylmethane 2,
4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicycloxylmethane 4,4'-diisocyanate, dicyclohexylmethane 2,4'-diisocyanate isocyanate, lysine isocyanate, etc.

Furthermore, in the case of UV irradiation to the above formulation,
By incorporating a UV initiator, it is possible to reduce the polymerization and curing time due to UV irradiation as well as the amount of UV irradiation, thereby reducing the desired adhesive strength. The UV
Examples of the initiator include benzoin, benzoin methyl ether, benzoin ethyl ether,
These include benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, and the like. The adhesive sheet thus obtained is generally protected by polymerizing a releasable sheet treated with an appropriate silicone-based release agent or the like on the top surface of the curable adhesive coating layer in accordance with a conventional method. .

Specific examples of pressure-sensitive adhesive sheets used in the method of the present invention are listed, and the difference between the initial adhesive strength and the adhesive strength after irradiation was investigated for each of them when irradiated with radiation.

Example 1 Acrylic adhesive (copolymer of 2-ethylhexyl acrylate and n-butyl acrylate)
100 parts and urethane acrylate oligomer (trade name Seikabeam EX-810, manufactured by Dainichiseika Industries)
100 parts of the mixture was coated on a 38 μm thick polypropylene film and dried by heating to form a 10 μm thick coating layer of radiation curable adhesive, and a release paper was pasted on the top surface to prepare a product. After removing the release paper, a silicon wafer with a diameter of 10 cm was pasted on the top surface of the curable adhesive layer, and the adhesive strength was measured based on JIS-Z-0237, which was 1350 g/25 mm. Effective absorbed dose of EB to the coating layer of the agent
After irradiating with 2 Mrad for 1 second (voltage 150 KeV, current 5 mA), the adhesive strength was measured and was found to have significantly decreased to 38 g/25 mm.

Next, the silicon wafer was peeled off, but no adhesive was observed at all. For comparison, the wafer was immediately peeled off without the EB irradiation described above, but a large amount of adhesive was observed on the back surface.

Example 2 A mixture of 100 parts of the same acrylic adhesive as above, 53.8 parts of the same urethane acrylate oligomer as above, and 10 parts of isocyanate curing agent (trade name: BHS-8515 manufactured by Toyo Ink Mfg. Co., Ltd.) was applied to a 60 μm thick polypropylene film. Apply to, heat dry, and thicken
A 15 μm coating layer of radiation-curable adhesive was formed, a silicon wafer was attached to the top surface, and the adhesive strength was measured to be 1550 g/25 mm. Next, this was irradiated with EB under the same conditions as in Example 1, and the adhesive strength was measured after that, and it was found to be 45g/25
mm, which had decreased significantly.

Example 3 100 parts of the same acrylic adhesive as above and 100 parts of the same urethane acrylate oligomer as above.
A mixture with 5 parts of UV initiator (benzoin) was applied to a transparent vinyl chloride film with a thickness of 50 μm, and a silicon wafer was attached to the top of the coated layer formed by heating and drying, and the adhesive strength was measured. 1380
g/25mm. This was irradiated with UV light for 6 seconds (high-pressure mercury lamp, 80 W/cm). The adhesive strength at that time is 52
g/25mm, which was a significant decrease.

Example 4 Acrylic adhesive (N-butyl acrylate and 2-hydroxyethyl methacrylate copolymer)
100 parts and urethane acrylate oligomer (product name Nitsuso Kiyure UM-1, manufactured by Shin Nisso Kako Co., Ltd.)
53.8 parts, isocyanate curing agent (BHS-8515)
10 parts and UV initiator (trade name Irgakiure 651,
A silicon wafer was attached to the upper surface of the coated layer formed by applying 5 parts of the mixture (manufactured by Ciba Geigy) to a transparent polyethylene terephthalate film with a thickness of 38 μm and drying by heating.

The adhesive force at that time was measured to be 1420g/25mm, and it was irradiated with UV light for 2 seconds (high pressure mercury lamp,
80W/cm), the adhesive strength was 12g/25
mm.

Example 5 100 parts of acrylic adhesive (copolymer of n-butyl acrylate and acrylic acid) and urethane acrylate oligomer (trade name Seikabeam 14-)
1. Apply a mixture of 150 parts (manufactured by Dainichiseika Kogyo Co., Ltd.) and 10 parts of an isocyanate curing agent (trade name: BHS-8515, manufactured by Toyo Ink Mfg. Co., Ltd.) to a polyethylene film with a thickness of 80 μm, heat and dry it, and then A 10 μm coating layer of radiation-curable adhesive was formed, a silicon wafer was attached to the top of the coating layer, and the adhesive strength was measured, and it was found to be 900 g/25 mm.
When irradiated with UV light for 1 second (high-pressure mercury lamp, 80 W/cm), the adhesive strength decreased to 16 g/25 mm.

Next, one example of how to use the adhesive sheet for semiconductor wafers of the present invention will be explained with reference to the drawings.

Figure 1 shows one of the adhesive sheets used in the method of the present invention.
Example FIGS. 2 and 3 show an example of how the adhesive sheet shown in FIG. 1 is used for a semiconductor wafer.

In the figure, 1 is a base material made of a transparent synthetic resin sheet having extensibility, 2 is a curable adhesive coating layer applied to the upper surface thereof, and 3 is a pressure-sensitive adhesive sheet A of the present invention consisting of these layers 1 and 2. The top surface of the temporary polymerized releasable sheet is shown. The base material 1 and the curable adhesive coating layer 2 were the same as those in Example 5 of the adhesive sheet.

Reference numeral 4 denotes a push-up needle rod consisting of a hollow needle rod, and the inside of the push-up needle rod 4 is formed to serve as a radiation irradiation tube 6 as a conduit path 5a for radiation 5 connecting to a radiation source, thereby simplifying the apparatus. .

First, the releasable sheet 3 is removed from the adhesive sheet A shown in the first diagram, and the curable adhesive coating layer 2 is placed facing upward as shown in the second diagram, and the upper surface of the coating layer 2 is subjected to dicing. Attach semiconductor wafer B. In this adhered state, dicing, cleaning, drying, and expanding are generally performed next, but the adhesive contained in the curable adhesive 2 sufficiently coats the semiconductor wafer B onto the adhesive sheet A.
Because it is held glued to the predetermined dicing,
Washing, drying, and expanding can be performed without each chip falling off.

Next, when picking up these wafer chips B', B', etc. one by one and mounting them on a predetermined base, before picking up the wafer chips B', B', etc., as shown in FIG. The push-up needle rod 4 irradiates radiation 5 such as UV or EB to the two curable adhesive layers on the lower surface of the wafer chip B' to be picked up, thereby curing the urethane acrylate oligomer contained therein. In such a case, the adhesive strength of only the coated layer portion of the curable adhesive 2 irradiated with radiation will be significantly reduced, resulting in a cured coated layer 2' in which only a very small amount of adhesive strength remains. Next, after reducing the adhesive force of only the curable adhesive 2 in that part by irradiation with radiation, the wafer chip B' to be picked up is pushed up by the push-up needle 4 from the lower surface in a conventional manner, and in this state, for example, It is picked up using air tweezers 7 and mounted on a predetermined base. In this pick-up process, the wafer chip B' to be picked up is
Since almost no adhesive is attached to the cured coating layer 2', wafer chips of good quality can be obtained by picking up easily and without any adhesive contamination, and wafer chips other than those to be picked up can be easily picked up. is adhered to the uncured curable adhesive 2 with high adhesive strength, and does not fall off from the adhesive sheet A. In such a case, the adhesive force of a portion of the curable adhesive 2 is almost completely eliminated, and at the same time, the push-up needle 4, which also serves as the radiation irradiation tube 6, is used to push up the adhesive, thereby making it possible to shorten the pick-up operation.

In addition, in the processing of the semiconductor wafer mentioned above, expanding is not performed, but dicing, cleaning,
The wafer chips can also be picked up immediately after drying. At this time, when the adhesive strength of the adhesive coating layer is reduced by irradiation according to the present invention, a predetermined pick-up can be performed satisfactorily.

(Effects of the Invention) As described above, according to the present invention, after performing the dicing process, when necessary, a push-up needle rod that also serves as a radiation irradiation tube is applied to the base material surface of the adhesive sheet to which the wafer chips of the semiconductor wafer are adhered. By irradiating radiation, it is possible to significantly reduce the adhesive strength of only the radiation-curable adhesive on the adhesive sheet at the radiation irradiation position, and when pick-up processing is performed on wafer chips, the adhesive strength of the radiation-curable adhesive on the adhesive sheet can be significantly reduced. No adhesive remains on the adhesive surface of the wafer chips that have been picked up, and the adhesive strength of the adhesive in areas other than those irradiated with radiation does not decrease, so wafer chips other than those that should be picked up may shift on the adhesive sheet or Wafer chips can be picked up smoothly without falling off the adhesive sheet.
In addition, since a push-up needle rod that also serves as a radiation irradiation tube is used during radiation irradiation, the push-up needle lever can be pushed up from the bottom surface of the adhesive sheet of the wafer chip to be picked up at the same time as radiation irradiation. This method has the advantage that pick-up processing can be performed more quickly than conventional methods.

[Brief explanation of the drawing]

Figure 1 shows one of the adhesive sheets used in the method of the present invention.
The cross-sectional views of examples, Figures 2 and 3 are one example of how the adhesive sheet is used for semiconductor wafers.
The cross-sectional side views of the examples, FIGS. 4 and 5, are cross-sectional side views showing how to use a conventional pressure-sensitive adhesive sheet. 1... Base material, 2... Radiation curable adhesive, 2'
... Cured layer, 3... Peelable sheet, A... Adhesive sheet,
B...Semiconductor wafer, B'...Wafer chip, 4
...Pushing needle rod, 5...Radiation, 6...Radiation irradiation tube, 7...Air tweezers.

Claims (1)

[Claims] 1 An adhesive sheet formed by forming a coating layer of a radiation-curable adhesive on the base material surface is attached to the back side of a semiconductor wafer, and after dicing the semiconductor wafer, wafer chips of the semiconductor wafer are attached. The base material surface of the adhesive sheet is irradiated with radiation from a push-up needle that also serves as a radiation irradiation tube to reduce the adhesive strength of only the adhesive on the adhesive sheet at the radiation irradiation position, and the wafer chips are subjected to pick-up treatment. A method of using an adhesive sheet for semiconductor wafers, which is characterized by: