JPH07105367B2 - Adhesive sheet for semiconductor wafer dicing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet for wafer dicing, which is used when dicing a semiconductor wafer such as silicon or gallium arsenide into chips, and does not generate chlorine ions during dicing and is expanded during expansion. The present invention relates to a pressure-sensitive adhesive sheet for semiconductor wafer dicing, which exhibits uniform elongation.

[0002]

2. Description of the Related Art In order to separate a semiconductor wafer such as silicon or gallium arsenide into wafer chips, the semiconductor wafer is previously stuck and fixed on an adhesive sheet, and then dicing, washing, drying, expanding, picking up and mounting are performed. However, during these steps, the wafer chips may be detached and scattered from the adhesive sheet. Further, although it is easy to increase the adhesive strength in order to suppress detachment and scattering of the wafer chips, the wafer chips are less likely to be peeled off from the adhesive sheet at the time of pickup, and in recent years, as the degree of integration increases and the area of the wafer chips increases, Picking up is getting difficult. In order to solve these points, cross-linking and curing by a surface base material that can transmit ultraviolet rays and ultraviolet irradiation applied on the surface base material,
By using a UV-curable adhesive sheet for fixing semiconductor wafers that has a pressure-sensitive adhesive layer that has the ability to reduce adhesive strength, strong adhesive strength is maintained during the dicing, washing, and drying processes, and then ultraviolet rays are irradiated from the support side. The UV-curable pressure-sensitive adhesive layer is cross-linked and cured to reduce the adhesive force and facilitate the pick-up of wafer chips.

As the surface substrate of these UV-curable pressure-sensitive adhesive sheets, films of polyvinyl chloride and its copolymers and polyolefin films of polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymers, etc. are used. Among them, the films of polyvinyl chloride and its copolymers cause various problems because they contain chlorine and a plasticizer is added.

First of all, chlorine is a so-called full cut system in which the wafer is completely cut and the adhesive layer of the adhesive sheet and a part of the film layer of the surface base material are cut. At this point, the polyvinyl chloride film and its copolymer film are decomposed and chlorine ions are generated, and these chlorine ions adhere to the wafer chips, causing troubles such as disconnection of the wiring of semiconductor parts.

Next, since the plasticizer is compounded, the expandability of the wafer chip is good, but when it is irradiated with ultraviolet rays, it migrates into the adhesive layer, and
As it is compatible with the UV-curable compound contained in the adhesive, it does not undergo cross-linking and curing smoothly, and the adhesive strength of the adhesive sheet does not decrease even when it is irradiated with ultraviolet light, and the adhesive transfers and adheres to the wafer chip. It becomes difficult to pick up. Further, when the pressure-sensitive adhesive sheet is stored, the plasticizer gradually migrates into the pressure-sensitive adhesive layer, and depending on storage conditions, the adhesive strength before ultraviolet irradiation may be reduced by half after 4 to 6 months. Therefore, the wafer chips are detached and scattered during the wafer chip manufacturing process, especially during the dicing and cleaning processes, which causes a low yield. To this end, apply acrylic, urethane, or vinyl chloride-based paint as a barrier layer to prevent migration of plasticizer at the interface between polyvinyl chloride and its copolymer film and UV-curable adhesive. However, it is not possible to completely block the migration of the plasticizer, and even if it is possible to suppress the migration of the plasticizer to a certain extent by methyl methacrylate, melamine and epoxy, they are generally lacking in flexibility and hard, Proper expansion is not possible during expansion, and the adhesive layer surface is cracked, whitened, and broken. In addition, even if it extends, it becomes non-uniform and the intervals between the wafer chips become uneven, which makes pickup difficult.

Next, when a polyolefin film is used, since no plasticizer is added, there is no adverse effect on the pressure-sensitive adhesive layer, there is no problem that the wafer chip is contaminated with the plasticizer, and the pressure-sensitive adhesive sheet ages. Although there is little change and the quality is stable and storage is easy, there is a drawback that it is difficult to uniformly spread in the expanding process. Further, when a polyolefin film such as low-density polyethylene or ethylene-vinyl acetate copolymer which is relatively easy to stretch is used, it stretches well during expansion, but the portion in contact with the circular ring in the peripheral portion is particularly likely to stretch and cracks or breakage easily occur. On the other hand, in the case of a polyolefin film such as polybutene or high-density polyethylene which is relatively difficult to stretch, the peripheral portion is stretched on the flat ring, and the flat ring is lifted by the contracting force.

[0007]

The present invention focuses on the above-mentioned problems of the prior art, does not generate chlorine ions during dicing, does not cause detachment and scattering of element chips of a wafer chip, and irradiates ultraviolet rays for adhesion. After the adhesive layer is cross-linked and hardened to reduce the adhesive strength, it shows a uniform expansion of the expansion rate in the expanding process.
The pressure-sensitive adhesive layer and the surface base film layer are not cracked, whitened, cracked, broken, etc. and are excellent in pick-up suitability. Furthermore, if necessary, a surface treatment layer is applied to bond the surface base film and the pressure-sensitive adhesive layer. Since the adhesive strength is strong, it prevents the adhesive from transferring and adhering to the chips of the silicon wafer in the semiconductor manufacturing process or adhering to the surface of the rotary blade during dicing, and since there is no influence of the plasticizer, the adhesive strength after UV irradiation is also appropriate. It is an object of the present invention to provide a pressure-sensitive adhesive sheet for semiconductor wafer dicing, which reduces the number of products and reduces the change over time of the product.

[0008]

Means for Solving the Problems The present inventor has diligently studied the development of a dicing film which has the strength required for dicing in the manufacture of semiconductor chips and which does not have the above-mentioned drawbacks. The inventors have found that a substrate is suitable and completed the present invention. That is, the present invention uses, as a surface substrate, a laminate comprising at least two layers of an internally plasticized polyvinyl chloride film capable of transmitting ultraviolet rays and a polyolefin film, and an ultraviolet curable pressure-sensitive adhesive layer on the surface of the polyolefin film side. Is a pressure-sensitive adhesive sheet for semiconductor wafer dicing, which is obtained by stacking

Up to now, there have been many mentions that polyvinyl chloride and its copolymer film and polyolefin film are used, but it is also used in the laminate as in the present invention,
There is no concrete description of a pressure-sensitive adhesive sheet that prevents chlorine ions, suppresses migration of a plasticizer, and has good expandability of a polyvinyl chloride film.

The term "internally plasticized polyvinyl chloride film" as used herein means a polycondensed polyvinyl chloride film obtained by copolymerizing polyvinyl chloride and another monomer without blending polyvinyl chloride with a plasticizer such as DBP or DOP. It means a film obtained from vinyl chloride, and as the internal plasticized polyvinyl chloride, any internal plasticized polyvinyl chloride known per se can be used. Copolymers obtained by copolymerizing monomers that can be polymerized, particularly vinyl chloride-vinyl acetate, vinyl chloride-higher alkyl vinyl ether, vinyl chloride-ethylene vinyl acetate, vinyl chloride-acrylate, vinyl chloride-ethylene, vinyl chloride. -Copolymers such as propylene.

The polyolefin as the raw material for the polyolefin film is a homopolymer of olefin,
Alternatively, a copolymer containing an olefin as a main component and a monomer copolymerizable therewith is used, and preferable polyolefins include, for example, low density polyethylene, high density polyethylene, polypropylene, propylene-ethylene copolymer, ethylene-vinyl acetate copolymer. Coalesce, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer,
Examples thereof include ethylene-ethyl acrylate copolymer, ionomer resin, polybutylene, polybutene and the like.

The above-mentioned laminate constituting the surface base material of the present invention is basically based on a layer structure in which the upper layer is a layer of an internally plasticized polyvinyl chloride film and the lower layer is a polyolefin film. As the intermediate layer, a layer of a film made of another transparent resin may be interposed as long as the ultraviolet transmittance is not impaired.

For the laminate, a method of laminating preformed films with an adhesive, a method of thermocompressing the films with each other, a method of coextruding each molten resin and laminating, etc. are appropriately adopted. You can

The following description is for a laminate comprising two layers of an internally plasticized polyvinyl chloride film and a polyolefin film. The thickness of the laminate of the internally plasticized polyvinyl chloride film and the polyolefin film is 30 to 160 μm, preferably 60.
To 130 microns. Where the thickness of the internally plasticized polyvinyl chloride film is 20 to 100 microns,
It is preferably 40 to 70 microns. If it is less than 20 microns, the performance of the polyolefin film is biased, so it does not stretch uniformly when expanded, and only the peripheral portion or the central portion does not stretch significantly. Also, the flat ring is pulled by the force to restore the base film. Good expandability cannot be obtained due to peeling from the chip or narrowing of the chip interval. On the other hand, when the thickness is 100 microns or more, the polyolefin film becomes thin, the rotary blade reaches not only the polyolefin film but also the internal plasticized polyvinyl chloride film layer during dicing, and chlorine ions are generated by the friction heat.

The thickness of the polyolefin film is 10 to 50 μm, preferably 20 to 4
0 micron is good. If it is 10 microns or less, the rotary blade cuts through the polyolefin film during dicing and cuts even the internal plasticized polyvinyl chloride film. Conversely, if it is 50 microns or more, the performance of the polyolefin film is biased, so that it is uniform during expansion. Stretching or peeling from flat ring after expansion occurs.

Next, an ultraviolet-curable pressure-sensitive adhesive layer is provided on the surface of the laminating film on the polyolefin film side, either directly or via a surface treatment layer. The purpose of using the surface treatment agent here is to improve the adhesiveness between the polyolefin film and the UV-curable adhesive, and dicing, washing, drying,
It prevents the adhesive from transferring and adhering to the element pieces of the wafer during the UV irradiation, expanding and picking up steps. Further, it also suppresses adhesion of the adhesive to the surface of the rotary blade during dicing.

As the paint used as the surface treatment agent, when the polymer having affinity for the polyolefin film and the polymer having affinity for the ultraviolet curable adhesive are the same, they are single, and when they are different. It is preferable to mix and use. That is, an ethylene-vinyl acetate copolymer, an isocyanate compound , a mixture of a graft polymer of rubber and acrylic acid and an isocyanate compound , chlorinated polyethylene, chlorinated polypropylene and the like are used.
Also, it is often used to increase the adhesion between the adhesive and the film by subjecting it to corona discharge treatment.

Next, the UV-curable pressure-sensitive adhesive layer,
Well-known UV-curable pressure-sensitive adhesives are widely used here, and in particular, UV-curable pressure-sensitive adhesives prepared by blending an acrylic pressure-sensitive adhesive with a UV-polymerizable prepolymer and / or a UV-polymerizable monomer in an amount of 1 to 150% are used. To be That is, a pressure-sensitive adhesive obtained by mixing an acrylic pressure-sensitive adhesive with an ultraviolet polymerizable compound is used. Examples of the acrylic pressure-sensitive adhesive include those having as a main component an acrylic acid ester polymer having 2 to 8 carbon atoms and a copolymer with a vinyl monomer such as vinyl acetate, vinylidene chloride, or methacrylic acid ester. .

On the other hand, examples of the UV-polymerizable prepolymer include polyester monoacrylate, polyester diacrylate, polyester triacrylate, epoxy acrylate, polyurethane acrylate, polyether acrylate, melamine acrylate, alkyd acrylate, and silicon acrylate. Is isodecyl acrylate, stearyl acrylate, lauryl acrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, polyethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, etc. Can be mentioned.

The UV-polymerizable monomers include monofunctional monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and tetrahydrofurfuryl acrylate, and the difunctional monomers include dicyclohexyl acrylate. Examples include pentanyl diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, and polyethylene glycol diacrylate.
Examples of trifunctional or higher functional monomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

Next, a crosslinking agent is added to the UV-curable pressure-sensitive adhesive, and it is effective to add a sensitizer to improve the UV-curing reaction. Examples of the cross-linking agent include peroxides, polyisocyanates, metal phosphates and the like. Also, benzoin as a sensitizer,
Benzoin ethyl ether, benzoin isopropyl ether, diphenyl sulfide, anthracene, benzophenone, α-chloroanthraquinone, diphenyl disulfide, diacetyl, hexachlorobutadiene,
Pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene and the like can be mentioned, and 0.1 to 5% is compounded and usually 3% or less is sufficient to exert the effect sufficiently.

The UV-curable pressure-sensitive adhesive composition is prepared as a pressure-sensitive adhesive using a solvent such as toluene, ethyl acetate or methyl ethyl ketone, and is applied to the surface of the above-mentioned two-layer structure on the polyolefin film side by a conventional method. Then, an adhesive layer is provided to obtain an adhesive sheet for semiconductor wafer dicing. The pressure-sensitive adhesive layer of this pressure-sensitive adhesive sheet is optionally combined with a release sheet for protection.

To manufacture a semiconductor chip using the thus obtained adhesive sheet for wafer dicing, first, the semiconductor wafer is adhesively fixed on the adhesive layer of the adhesive sheet for wafer dicing. In this case, the ultraviolet curable adhesive of the present invention has an adhesive force of 120 to 1000 g / 25 mm.
The semiconductor wafer can be fixed with.

Next, a dicing saw is used to completely cut the elements formed on the surface of the semiconductor wafer in a grid pattern vertically and horizontally. Then, the surface of the pressure-sensitive adhesive sheet for wafer dicing is irradiated with ultraviolet rays from an ultraviolet source to cross-link the UV-curable pressure-sensitive adhesive, and after expanding, peeled from the pressure-sensitive adhesive sheet for wafer dicing with a vacuum chuck. A semiconductor chip can be obtained by separating.

The ultraviolet rays used in the present invention are 200 to 4
In the wavelength range of 00 nm, a mercury arc / low pressure / medium pressure / high pressure mercury lamp, a carbonic acid arc or the like can be used as an ultraviolet ray source, and an ultraviolet ray irradiation time of 0.1 to 10 seconds is sufficient. The UV-curable pressure-sensitive adhesive of the present invention has an adhesive force reduced to 10 to 100 g / 25 mm by UV irradiation, and can be easily peeled from a wafer dicing sheet by a vacuum chuck.

[0026]

The pressure-sensitive adhesive sheet for wafer dicing according to the present invention comprises, as a base material, at least two layers of an internally plasticized polyvinyl chloride film and a polyolefin film, and the surface of the polyolefin film side is coated with an ultraviolet-curable pressure-sensitive adhesive. A layer is formed, and during dicing, the rotary blade cuts the wafer, then cuts the ultraviolet-curable adhesive layer, and further cuts a part of the film of the surface base material. During this dicing, the rotary blade reaches only the middle of the layer of the polyolefin film, and does not reach the layer of the internally plasticized polyvinyl chloride film. Therefore, chlorine ions are not generated even if frictional heat is generated between the rotary blade and the wafer during dicing.

Further, since the pressure-sensitive adhesive sheet according to the present invention has no plasticizer added to the base material, the pressure-sensitive adhesive sheet as compared with a pressure-sensitive adhesive sheet using polyvinyl chloride to which a plasticizer is added and a copolymer film thereof is a product. There is no change with time in the adhesive force of, and an appropriate reduction of the adhesive force after ultraviolet irradiation can be obtained.

Furthermore, when the semiconductor wafer is diced and irradiated with ultraviolet rays to reduce the adhesive force and then expanded in the expanding step, uniform expansion is achieved and a sufficient interval is obtained between the chips to ensure the pick-up of the wafer chips. Is what you can do.

[0029]

Example 1 Acrylic two-component adhesive (SW-2B) Soken Scientific 100 parts by weight UV curable compound (polyester oligomer) Dainichi Seika 90 parts by weight Crosslinking agent (Coronate L) 15 parts by weight Sensitizer (benzophenone ) 3 parts by weight An ultraviolet-curable adhesive having the above composition was prepared, and an applicator was applied onto a 50-micron-thick polyester film coated with a silicone resin so that the thickness after drying would be 10 microns. Apply using 100
Dry for 2 minutes at ° C. The above-mentioned adhesive is applied to the surface of the ethylene-vinyl acetate copolymer side of the film obtained by laminating the internally plasticized polyvinyl chloride film (thickness 60 microns) and the ethylene-vinyl acetate copolymer film (thickness 40 microns) after drying. Stick together so that

Using the pressure-sensitive adhesive sheet for wafer dicing thus obtained, a dicing test was conducted to test the adhesive strength, the amount of chloride ions, and the expandability, and the results are shown in the test result table.

[0031]

Comparative Example 1 Using the UV-curable adhesive used in Example 1, a polyvinyl chloride film (thickness: 80 μm; including 35 parts by weight of a plasticizer) was applied and laminated, and various kinds of adhesives were prepared in the same manner as in Example 1. The test was conducted and the results are shown in the test result table.

[0032]

[Comparative Example 2] The UV-curable adhesive used in Example 1 was used to adhere to a polybutene film (thickness: 100 µm), various tests were conducted in the same manner as in Example 1, and the results are shown in the test result table. It was

[0033]

【Test results】 【table】

* 1 ... Stainless steel plate (SUS- # 304 1200
Adhesiveness to mesh finish). * 2 ... After dicing the adhesive sheet to a depth of 20 microns, place the adhesive sheet in pure water for 10
It was heated and extracted at 0 ° C. for 2 hours, and analyzed and quantified by an ion chromatograph (Dionex QIC). * 3: A silicon wafer is 2 x 2 m with a dicing saw.
Results obtained by fully cutting to m, UV curing, and stretching with a wafer expansion device (appearance, chip spacing). From the above test results, in Example 1, there is no problem in any of the items, but in Comparative Example 1, the adhesive strength is 40 ° C., the value before / after UV irradiation after 3 months, and In Comparative Example 2, it can be seen that the expandability is abnormal.

Claims (2)

[Claims] 1. A pressure-sensitive adhesive sheet for semiconductor wafer dicing, wherein the surface substrate for transmitting ultraviolet light is a polyolefin film side of a laminated film comprising at least two layers including an internal plasticized polyvinyl chloride film and a polyolefin film as a layer constituent material. A pressure-sensitive adhesive sheet for semiconductor wafer dicing, characterized in that a UV-curable pressure-sensitive adhesive layer whose adhesive strength is reduced by irradiation of ultraviolet rays is formed on the surface. 2. The pressure-sensitive adhesive sheet for semiconductor wafer dicing according to claim 1, wherein the pressure-sensitive adhesive layer is formed on a polyolefin film layer with a surface treatment agent layer interposed therebetween.