JP2009130233A - Film for chip protection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for chip protection, which is superior in operability and productivity when a protective film is cured, and which achieves compatibility between an increase in hardness and an increase in adhesive property to a chip. <P>SOLUTION: The film chip protection has a low-hardness layer 1a to be stuck on a chip and a high-hardness layer 1b provided on the low-hardness layer 1a directly or with other layers interposed, wherein the high-hardness layer 1b is an energy-beam curable resin layer containing a binder polymer component, an energy-beam curable component, and a photopolymerization initiator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chip protection film, and more particularly to a chip protection film for protecting the back surface of a semiconductor chip mounted in a face-down manner.

In recent years, as a mounting technology for semiconductor elements such as integrated circuits, WL-CSP (Wafer Level Chip Size Package), which is packaged in a wafer state before dicing and is cut into chips at the final stage, has been put into practical use. Progressing. WL-CSP has the characteristics of being small, thin, and high speed because it is almost the same size as a bare chip and has a short wiring length, and is adopted as a CSP for mobile phones, for example.

In such WL-CSP, a tape substrate with bumps is used as a semiconductor package substrate (also referred to as rewiring or Interposer), and bumps formed on the tape substrate and bumps formed on the circuit formation surface of the semiconductor wafer. And are connected directly. At this time, the semiconductor wafer is mounted on the tape substrate by a so-called face-down method in which the circuit formation surface faces the tape substrate.
The tape substrate on which the semiconductor wafer is mounted is cut (diced) in units of chips by a dicing saw, whereby a CSP having the same size as the semiconductor chip can be obtained.

  In the CSP as described above, the back surface of the chip is not sealed with resin and is exposed to the outside. Therefore, various chip protection films have been proposed to protect and reinforce the back surface of the chip. The film for chip protection also has a function of suppressing chipping during dicing by being attached to the back surface of the wafer before dicing.

  For example, Patent Document 1 discloses a protective film for a chip having a release sheet, a protective film forming layer formed of a thermosetting component or energy ray curable component formed on the release surface of the release sheet, and a binder polymer. A forming sheet is disclosed. In Patent Document 1, the protective film forming layer of the chip protective film forming sheet is attached to the back surface of the semiconductor wafer, the release sheet is peeled off from the protective film forming layer, and then the protective film forming layer is cured by heating or irradiation with energy rays. Then, a protective film is formed on the entire surface of the wafer. Thereby, since the strength is improved as compared with the case of the wafer alone, damage to the wafer during handling is reduced.

Patent Document 2 discloses a protective film-forming sheet for chips having a curable protective film composed of a thermosetting component and / or an energy ray-curable component, as in Patent Document 1, and further includes protection. Add fillers, pigments, dyes, etc. to the protective film forming layer for the purpose of improving the strength and hardness of the film, improving mark recognition when performing laser marking such as product number on the protective film, and improving the appearance. Is disclosed.
JP 2004-260190 A JP 2004-214288 A

  As described in Patent Documents 1 and 2, the method of curing the protective film includes a method of heating and curing the protective film forming layer containing a thermosetting component, and a protection containing an energy ray curable component. There is a method of curing the film forming layer by irradiation with energy rays.

  In general, heat curing requires heat treatment at 100 to 200 ° C. for about 1 to 3 hours. In the case of such thermosetting, since the protective film cures slowly while flowing, a protective film having excellent adhesion to the chip and high hardness can be obtained. However, thermosetting has a problem that processing time is long and workability and productivity are poor.

  On the other hand, in energy ray curing, for example, ultraviolet rays can be instantly cured in about 10 to 300 seconds, and the processing time is much shorter than heat curing, and the workability and productivity are excellent. It is also advantageous in that the curing equipment is compact. However, since the protective film is instantaneously cured, there is a problem that the cured protective film has low adhesion to the chip and is easily peeled off. In particular, when a filler such as silica is added to the protective film forming layer for the purpose of improving the strength and hardness of the protective film, the protective film is more easily peeled off as the filler is added. That is, improvement in the hardness of the protective film and improvement in adhesion to the chip are in a trade-off relationship, and development of a chip protective film that satisfies both of these is desired.

  Accordingly, an object of the present invention is to provide a chip protection film that is excellent in workability and productivity at the time of curing a protective film, and has both improved hardness and improved adhesion to the chip.

  The first aspect of the present invention includes a low hardness layer bonded to a chip, and a high hardness layer provided directly or via another layer on the low hardness layer, A film for protecting a chip, which is an energy ray curable resin layer containing a binder polymer component, an energy ray curable component, and a photopolymerization initiator.

  According to a second aspect of the present invention, in the film for chip protection according to the first aspect, the low hardness layer contains a binder polymer component, an energy ray curable component and / or a thermosetting component. It is characterized by.

  According to a third aspect of the present invention, in the film for protecting a chip according to the first or second aspect, the energy ray curable component is selected from the group consisting of epoxy acrylate, urethane acrylate, and oligoester acrylate. It is at least one kind.

  According to a fourth aspect of the present invention, in the film for protecting a chip according to the second or third aspect, the energy ray curable component of the low hardness layer is a bisphenol A type epoxy acrylate.

  According to a fifth aspect of the present invention, in the film for chip protection according to any one of the second to fourth aspects, the energy ray curable component of the low hardness layer is an epoxy acrylate having a weight average molecular weight of 1000 or more. It is characterized by that.

  According to a sixth aspect of the present invention, in the chip protection film according to any one of the second to fifth aspects, the low hardness layer further contains a photopolymerization initiator.

  According to a seventh aspect of the present invention, in the chip protection film according to any one of the first to sixth aspects, the energy ray curable component of the high hardness layer is a novolac epoxy acrylate. To do.

  According to an eighth aspect of the present invention, in the film for protecting a chip according to any one of the first to seventh aspects, the energy ray curable component of the high hardness layer is an epoxy acrylate having a weight average molecular weight of less than 1000. It is characterized by that.

  According to a ninth aspect of the present invention, in the film for protecting a chip according to any one of the first to eighth aspects, the high hardness layer has a pencil hardness of 3H or more, and the low hardness layer has a high hardness. It has a pencil hardness of 4H or less, provided that it is relatively lower than the pencil hardness of the hardness layer.

  According to a tenth aspect of the present invention, in the film for protecting a chip according to any one of the first to ninth aspects, the photopolymerization initiator absorbs light in a long wavelength region of 350 nm or more. It is characterized by being.

  According to an eleventh aspect of the present invention, in the film for protecting a chip according to the tenth aspect, the photopolymerization initiator is acylphosphine oxide.

According to a twelfth aspect of the present invention, in the film for protecting a chip according to the eleventh aspect, the film is 2,4,6-trimethylbenzoyldiphenylphosphine oxide represented by the following structural formula (1). To do.
Structural formula (1)

  According to a thirteenth aspect of the present invention, in the film for protecting a chip according to any one of the first to twelfth aspects, the high hardness layer further contains a filler.

  According to a fourteenth aspect of the present invention, in the chip protecting film according to any one of the first to thirteenth aspects, the high hardness layer further contains a dye and / or a pigment.

  According to a fifteenth aspect of the present invention, in the film for protecting a chip according to any one of the first to fourteenth aspects, the lower surface of the low hardness layer and the upper surface of the high hardness layer can be peeled off. It has the characteristic peeling sheet.

  The film for protecting a chip of the present invention has a laminated structure including a low hardness layer bonded to the chip and a high hardness layer that is an energy ray curable resin layer, and the low hardness layer has adhesion to the chip. And the hardness of the protective film is secured by the high hardness layer which is the outermost layer. Thereby, the improvement of the hardness of a protective film and the adhesiveness with respect to a chip | tip which were conventionally difficult to achieve can be implement | achieved using the energy ray hardening method excellent in workability | operativity and productivity.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a film for protecting a chip of the present invention. As shown in FIG. 1, the film for chip protection of the present invention is a protective film forming layer having a laminated structure including a low hardness layer 1a bonded to the chip and a high hardness layer 1b provided on the low hardness layer 1a. 1 If necessary, the first release sheet 2 may be temporarily attached on the low hardness layer 1a, and the second release sheet 3 may be temporarily attached on the high hardness layer 1b. Further, the protective film forming layer 1 may have another layer such as an adhesive layer interposed between the low-hardness layer 1a and the high-hardness layer 1b as long as the gist of the present invention is not impaired. Below, each layer is demonstrated in detail.

<Protective film forming layer>
The protective film forming layer 1 has a laminated structure including a low hardness layer 1a and a high hardness layer 1b. The low hardness layer 1a is a layer whose hardness after curing is relatively lower than that of the high hardness layer 1b. For example, the pencil hardness based on JIS K 5600-5-4 is lower than that of the high hardness layer 1b. . The pencil hardness of the high hardness layer 1b after curing is preferably 3H or more, and particularly preferably 5H or more. On the other hand, the pencil hardness of the low-hardness layer 1a after curing is preferably 4H or less, provided that it is relatively lower than the pencil hardness of the high-hardness layer. By using a film for protecting a chip including such a low hardness layer 1a and a high hardness layer 1b, both improvement in adhesion to the chip and improvement in hardness can be achieved.

(High hardness layer)
The high hardness layer 1b is an energy ray curable resin layer containing a binder polymer component, an energy ray curable component, and a photopolymerization initiator. Here, the energy rays refer to light rays such as ultraviolet rays or ionizing radiations such as electron beams. Moreover, the high hardness layer 1b may contain dye and / or a pigment, a filler, and another component other than the said component as needed. These components will be described below.

-Polymer component-
In the present invention, a polymer component is used in order to improve flexibility and operability as a film. As the polymer component, for example, an acrylic copolymer, a polyester resin, a urethane resin, a silicone resin, a rubber polymer, or the like is used. Among these, an acrylic copolymer is particularly preferable.

  Among acrylic copolymers, it is preferable to use an epoxy group-containing acrylic copolymer. This epoxy group-containing acrylic copolymer contains 0.5 to 6% by mass of glycidyl acrylate or glycidyl methacrylate having an epoxy group. In order to obtain a high adhesive force with the wafer, the content is preferably 0.5% by mass or more, and gelation can be suppressed if it is 6% by mass or less. The Tg of the epoxy group-containing acrylic copolymer is preferably −10 ° C. or higher and 30 ° C. or lower.

  The amount of glycidyl acrylate or glycidyl methacrylate used as the functional group monomer is a copolymer ratio of 0.5 to 6% by mass, but the remainder is an alkyl having 1 to 8 carbon atoms such as methyl acrylate and methyl methacrylate. Mixtures of acrylates, alkyl methacrylates, and styrene and acrylonitrile can be used. Among these, ethyl (meth) acrylate and / or butyl (meth) acrylate are particularly preferable. The mixing ratio is preferably adjusted in consideration of the Tg of the copolymer. There is no restriction | limiting in particular in a polymerization method, For example, pearl polymerization, solution polymerization, etc. are mentioned, A copolymer is obtained by these methods. Examples of such an epoxy group-containing acrylic copolymer include HTR-860P-3 (trade name, manufactured by Nagase ChemteX Corporation).

  The weight average molecular weight of the acrylic copolymer is preferably 50,000 or more, particularly preferably in the range of 200,000 to 1,000,000. If the molecular weight is too low, sheet formation will be insufficient, and if it is too high, compatibility with other components will deteriorate, resulting in hindering film formation.

-Energy ray curable component-
The energy ray curable component is composed of a compound that is polymerized and cured when irradiated with energy rays such as ultraviolet rays and electron beams. As such a compound, one having at least one polymerizable double bond in the molecule and having a weight average molecular weight in the range of 100 to 30,000, more preferably in the range of 300 to 10,000 is used. Moreover, as an energy-beam curable component of the high hardness layer 1b, in order to make hardness high, that whose weight average molecular weight (Mw) is less than 1000 is especially preferable. In order to increase the hardness, it is effective to increase the crosslinking density after curing, and the crosslinking density after curing can be increased by using a low molecular weight energy ray-curable component of 1000 Mw or less.

  Examples of the energy ray-curable component include trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, or 1,4-butylene glycol diacrylate, Examples include 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, oligoester acrylate, polyester-type or polyether-type urethane acrylate oligomer, polyester acrylate, polyether acrylate, epoxy acrylate, and the like.

  Among these, an ultraviolet curable resin is particularly preferable. Specifically, epoxy acrylate, urethane acrylate oligomer, oligoester acrylate, and the like are preferable, and epoxy acrylate is particularly preferable in terms of hardness, heat resistance, adhesiveness, and the like.

  The epoxy acrylate used for the high hardness layer 1b is particularly preferably a polyfunctional epoxy acrylate such as a novolac type epoxy acrylate. By using a polyfunctional epoxy acrylate having high reactivity in this way, a high hardness layer having excellent hardness after curing can be obtained.

-Dyes and pigments-
The high hardness layer 1b may be colored. The high hardness layer 1b is colored by blending pigments, dyes and the like. By coloring the high hardness layer 1b, it is possible to improve the mark recognizability and the appearance when the high hardness layer 1b is subjected to laser marking such as a product number. Examples of such pigments include carbon black and various inorganic pigments. Also, various organic pigments such as azo, indanthrene, indophenol, phthalocyanine, indigoid, nitroso, xanthene, oxyketone and the like can be mentioned.

  The amount of these additives varies depending on the type, but is 0.1 to 10 parts by mass, preferably about 0.5 to 3 parts by mass with respect to 100 parts by mass in total of the energy ray-curable component, polymer and filler. Is appropriate. Moreover, in order to adjust the cohesive force before hardening, crosslinking agents, such as an organic polyvalent isocyanate compound, an organic polyvalent imine compound, and an organometallic chelate compound, can also be added.

-Filler-
Examples of the filler include silica such as crystalline silica and synthetic silica, and inorganic filler such as alumina and glass balloon. By adding an inorganic filler to the high hardness layer 1b, the hardness of the high hardness layer 1b can be improved. In addition, the thermal expansion coefficient of the cured layer can be brought close to the thermal expansion coefficient of the wafer, thereby reducing the warpage of the wafer during processing. Synthetic silica is preferable as the filler, and in particular, synthetic silica of the type in which the α-ray source that causes malfunction of the semiconductor device is removed as much as possible is optimal. As the shape of the filler, any of a spherical shape, a needle shape, and an amorphous type can be used, but a spherical filler capable of closest packing is particularly preferable.

  Moreover, as a filler added to the high hardness layer 1b, the following functional fillers may be mix | blended other than the inorganic filler mentioned above. For example, for the purpose of imparting conductivity after die bonding, a conductive filler such as gold, silver, copper, nickel, aluminum, stainless steel, carbon, or ceramic, or nickel, aluminum, etc. coated with silver is added. In addition, for the purpose of imparting thermal conductivity, a metal material such as gold, silver, copper, nickel, aluminum, stainless steel, silicon, germanium, or a thermal conductive material such as an alloy thereof may be added.

  The amount of filler added to the high hardness layer 1b varies depending on the type of filler, but is 30 to 90 parts by mass, preferably 7 with respect to 100 parts by mass in total of the energy ray curable component, polymer and filler. About 85 parts by mass is appropriate. The pencil hardness after curing can be adjusted by adding the filler in the high hardness layer 1b at such a blending ratio and irradiating it with energy rays. Further, the thermal expansion coefficient of the protective film after curing can be brought close to the thermal expansion coefficient of the wafer.

-Photopolymerization initiator-
By mixing a photopolymerization initiator into the high hardness layer 1b, the polymerization curing time and the amount of light irradiation can be reduced.
The usage-amount of the photoinitiator used by the high hardness layer 1b is 0.1-20 mass parts with respect to a total of 100 mass parts of an energy-beam curable component, Preferably it is about 1-10 mass parts. Is good.

  Photopolymerization initiators include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, methyl benzoin benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone , Α-hydroxycyclohexyl phenyl ketone, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, acylphosphine oxide and the like.

Among these, an acylphosphine oxide that absorbs light in a long wavelength region of 350 nm or more and is curable even in a system to which a dye and a pigment are added is particularly preferable. As the acylphosphine oxide, it is particularly preferable to use 2,4,6-trimethylbenzoyldiphenylphosphine oxide represented by the following structural formula (1).
Structural formula (1)

-Other ingredients-
In addition to the above components, the high hardness layer 1b contains a butadiene rubber, a silicone rubber, or the like as a crosslinking agent, a coupling agent, an antistatic agent, an antioxidant, a flame retardant, or a stress relaxation agent, if necessary. be able to. Moreover, you may contain the epoxy resin and the phenol resin for the thermosetting, and a latent hardener.

  A crosslinking agent is for adjusting the cohesive force before hardening, and an organic polyvalent isocyanate compound, an organic polyvalent imine compound, an organometallic chelate compound, etc. are mentioned.

  The coupling agent improves adhesion and adhesion without impairing the heat resistance of the cured film, and also improves water resistance (moisture heat resistance). The coupling agent is preferably a silane (silane coupling agent) from the viewpoint of versatility and cost.

  The thickness of the high hardness layer 1b is preferably 5 to 20 μm and more preferably 10 to 50 μm in order to ensure a certain hardness.

(Low hardness layer)
The low hardness layer 1a is a curable resin layer whose hardness after curing is relatively lower than that of the high hardness layer 1b.
The low hardness layer 1a is preferably a curable resin layer containing a binder polymer component, an energy ray curable component and / or a thermosetting component, and a photopolymerization initiator. And / or pigments, silica, and other components. These components will be described below.

-Polymer component-
As the polymer component of the low hardness layer 1a, the same polymer component as that of the high hardness layer 1b can be used.

-Energy ray curable component-
The energy ray curable component is composed of a compound that is polymerized and cured when irradiated with energy rays such as ultraviolet rays and electron beams. As such a compound, one having at least one polymerizable double bond in the molecule and having a weight average molecular weight in the range of 100 to 30,000, more preferably in the range of 300 to 10,000 is used. In addition, as the energy ray curable component of the low hardness layer 1a, a component having a weight average molecular weight of 1000 or more is particularly preferable in order to improve the toughness after curing and ensure adhesion to the wafer.

  As the energy ray curable component, the same material as the high hardness layer 1b can be used. Specifically, epoxy acrylate, urethane acrylate oligomer, oligoester acrylate, and the like are preferable, and epoxy acrylate is particularly preferable in terms of hardness, heat resistance, adhesiveness, and the like.

  As the epoxy acrylate used for the low hardness layer 1a, bisphenol A type epoxy acrylate is particularly preferable. The bisphenol A type epoxy acrylate is inferior in reactivity to the polyfunctional type novolac type epoxy acrylate preferably used in the high hardness layer 1b and has low hardness after curing, but has high flexibility and adhesion to a semiconductor chip. Excellent. Therefore, for example, by using a novolac epoxy acrylate for the high hardness layer 1b and a bisphenol A epoxy acrylate for the low hardness layer 1a, the hardness on the surface layer side of the protective film forming layer 1 is improved and the semiconductor chip is contacted. The adhesion on the lower layer side can be improved.

-Thermosetting component-
As long as the low hardness layer 1a has a lower hardness than the high hardness layer 1b, the low hardness layer 1a may contain a thermosetting component in addition to the energy beam curable component or instead of the energy beam curable component.

  Examples of the thermosetting component include epoxy resins, phenol resins, melamine resins, urea resins, polyester resins, urethane resins, acrylic resins, polyimide resins, benzoxazine resins, and mixtures thereof. Especially in this invention, an epoxy resin, a phenol resin, and these mixtures are used preferably.

  The epoxy resin used in the present invention is not particularly limited as long as it is cured and exhibits an adhesive action, but is an epoxy resin having a bifunctional group or more, preferably a weight average molecular weight of less than 5000, more preferably less than 3000. Can be used. Further, an epoxy resin having a weight average molecular weight of preferably 500 or more, more preferably 800 or more can be used.

  Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, alicyclic epoxy resins, aliphatic chain epoxy resins, phenol novolac type epoxy resins, and cresol novolac types. Epoxy resin, bisphenol A novolak type epoxy resin, diglycidyl etherified product of biphenol, diglycidyl etherified product of naphthalenediol, diglycidyl etherified product of phenol, diglycidyl etherified product of alcohol, and alkyl substitution products thereof , Bifunctional epoxy resins such as halides and hydrogenated products, and novolac type epoxy resins. Moreover, what is generally known, such as a polyfunctional epoxy resin and a heterocyclic ring-containing epoxy resin, can also be applied. These can be used alone or in combination of two or more. Furthermore, components other than the epoxy resin may be included as impurities within a range that does not impair the characteristics.

  More specifically, for example, commercially available products include Epicoat 807, Epicoat 815, Epicoat 825, Epicoat 827, Epicoat 828, Epicoat 834, Epicoat 1001, Epicoat 1002, Epicoat 1003, Epicoat 1055, Epicoat 1004, Epicoat 1004AF, and Epicoat 1007. , Epicoat 1009, Epicoat 1003F, Epicoat 1004F (trade name, manufactured by Japan Epoxy Resin Co., Ltd.), DER-330, DER-301, DER-361, DER-661, DER-662, DER-663U, DER-664 , DER-664U, DER-667, DER-642U, DER-672U, DER-673MF, DER-668, DER-669 (above, manufactured by Dow Chemical Co., Ltd. Name), YD8125, YDF8170 (above, manufactured by Toto Kasei Co., Ltd., trade name), etc .; bisphenol A type epoxy resin such as YDF-2004 (made by Toto Kasei Co., Ltd., trade name); Epicoat 152, Phenol novolac epoxy resins such as Epicoat 154 (trade name, manufactured by Japan Epoxy Resin Co., Ltd.), EPPN-201 (trade name, manufactured by Nippon Kayaku Co., Ltd.), DEN-438 (trade name, manufactured by Dow Chemical Company) Epicoat 180S65 (trade name, manufactured by Japan Epoxy Resin Co., Ltd.), Araldite ECN1273, Araldite ECN1280, Araldite ECN1299 (above, product name, manufactured by Ciba Specialty Chemicals), YDCN-701, YDCN-702, YDCN-703, Y CN-704 (above, manufactured by Toto Kasei Co., Ltd., trade name), EOCN-102S, EOCN-103S, EOCN-104S, EOCN-1012, EOCN-1020, EOCN-1025, EOCN-1027 (above, Nippon Kayaku Co., Ltd.) Cresol novolac type epoxy resin such as ECN 1031S, Epicote 1032H60, Epicote 157S70 (above, and more), ESCN-195X, ESCN-200L, ESCN-220 (above, trade name, manufactured by Sumitomo Chemical Co., Ltd.); Japan Epoxy Resin Co., Ltd., trade name), Araldite 0163 (Ciba Specialty Chemicals, trade name), Denacol EX-611, Denacol EX-614, Denacol EX-622B, Denacol EX-622, Denacol EX-51 2, Denacol EX-521, Denacol EX-421, Denacol EX-411, Denacol EX-321 (above, Nagase Kasei Co., Ltd., trade name), EPPN501H, EPPN502H (above, Nippon Kayaku Co., Ltd., trade name) Multifunctional epoxy resins such as Epicoat 604 (trade name, manufactured by Japan Epoxy Resin Co., Ltd.), YH-434 (trade name, manufactured by Toto Kasei Co., Ltd.), TETRAD-X, TETRAD-C (above, Mitsubishi Gas Chemical Co., Ltd.) Amine type epoxy resins such as ELM-120 (manufactured by Sumitomo Chemical Co., Ltd., trade name); hetero ring-containing epoxy resins such as Araldite PT810 (trade name, manufactured by Ciba Specialty Chemicals); ERL4234, ERL4299 , ERL4221, ERL4206 (above, manufactured by UCC, product ) Etc. can be used cycloaliphatic epoxy resins such as these can be used alone or in combinations of two or more.

  As the phenolic resin, it is preferable to use a novolak type or resol type resin because of its excellent resistance to electric corrosion during moisture absorption. The hydroxyl equivalent is preferably 150 to 400 g / eq, more preferably 180 to 300 g / eq, and still more preferably 180 to 250 g / eq. When the hydroxyl group equivalent is less than 150 g / eq, the water absorption rate tends to increase and the reflow resistance tends to deteriorate, and when it exceeds 400 g / eq, the glass transition point (Tg) tends to decrease and the heat resistance tends to deteriorate. There is.

Specific examples of such a phenol resin include a phenol resin represented by the following structural formula (2).
Structural formula (2)

(In the formula, each R ¹ may be the same or different and each is a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, a cyclic alkyl group having 3 to 10 carbon atoms, or a 7 to 10 carbon atoms. An aralkyl group, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a hydroxyl group, or a halogen atom is represented, n represents an integer of 1 to 3, and m represents an integer of 0 to 50. )

  Examples of the linear or branched alkyl group having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl and the like. Examples of the cyclic alkyl group having 3 to 10 carbon atoms include cyclohexyl, cyclopentyl and the like. Examples of the aralkyl group having 7 to 10 carbon atoms include 2-phenylethyl and 3-phenylpropyl.

  Examples of the alkenyl group having 2 to 10 carbon atoms include vinyl and allyl. Examples of the aryl group having 6 to 10 carbon atoms include phenyl and p-tolyl. Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom.

  The phenol resin represented by the structural formula (2) can be obtained, for example, by reacting a phenol compound and a xylylene compound which is a divalent linking group in the presence of no catalyst or an acid catalyst. Moreover, as a commercial item, the Millex XLC-series, the XL series (above, Mitsui Chemicals make, brand name) etc. can be mentioned, for example.

  When an epoxy resin is used as the thermosetting component, a curing accelerator or the like can be used as an auxiliary agent. There is no restriction | limiting in particular as a hardening accelerator which can be used for this invention, For example, a tertiary amine, imidazoles, a quaternary ammonium salt etc. can be used. Examples of imidazoles preferably used in the present invention include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, and the like. These may be used alone or in combination of two or more. Imidazoles are commercially available from Shikoku Kasei Kogyo Co., Ltd. under the trade names 2E4MZ, 2PZ-CN, 2PZ-CNS, for example.

  Moreover, since the phenolic hydroxyl group contained in the phenol resin easily undergoes an addition reaction with the epoxy group of the epoxy resin by heating, the phenol resin may be used as a curing agent for the epoxy resin.

-Dyes and pigments-
Similar to the high hardness layer 1b, the low hardness 1a may be colored by adding pigments and / or dyes. Examples of the pigment and dye are the same as those of the high hardness layer 1b.

  These addition amounts vary depending on the type, but 0 to 5 parts by mass, preferably 0.5 to 100 parts by mass of the energy ray curable component and / or thermosetting component, polymer and filler. About 2 parts by mass is appropriate.

-Filler-
A filler may also be added to the low hardness layer 1a on the condition that the hardness is lower than that of the high hardness layer 1b. Thereby, the thermal expansion coefficient of the layer after curing can be brought close to the thermal expansion coefficient of the wafer, and the warpage of the wafer caused by the difference in the thermal expansion coefficient during processing can be reduced. Examples of the filler added to the low hardness layer 1a include the same filler as the above-described high hardness layer 1b.

  The amount of filler added to the low-hardness layer 1a varies depending on the type of filler, but is 0 to 0 parts by mass with respect to a total of 100 parts by mass of the energy ray curable component and / or thermosetting component, polymer, and filler. 70 parts by mass, preferably about 30 to 60 parts by mass is appropriate. By adding the filler in the low hardness layer 1b at such a blending ratio and irradiating with energy rays, the pencil hardness after curing can be adjusted, and the thermal expansion coefficient of the protective film after curing is determined by the thermal expansion coefficient of the wafer. It can be close to the coefficient.

-Photopolymerization initiator-
A photopolymerization initiator may also be mixed into the low hardness layer 1a. As a photoinitiator, the thing similar to the high hardness layer 1b mentioned above can be mentioned. The usage-amount of the photoinitiator used by the low-hardness layer 1a is 0.1-20 mass parts with respect to a total of 100 mass parts of an energy-beam curable component and / or a thermosetting component, Preferably it is 1-1. It is good to set it as about 10 mass parts.

-Other ingredients-
In addition to the above-described components, the low hardness layer 1a can contain butadiene rubber, silicone rubber, or the like as a crosslinking agent, coupling agent, antioxidant, flame retardant, or stress relaxation agent, as necessary. Moreover, you may contain the epoxy resin and the phenol resin for the thermosetting, and a latent hardener.

  The thickness of the low hardness layer 1a is preferably 1 to 50 [mu] m, and more preferably 3 to 20 [mu] m, in order to exhibit adhesion to the semiconductor chip.

<Peeling sheet>
In the chip protective film of the present invention, the release sheets 2 and 3 are temporarily attached to one or both sides of the protective film forming layer 1 in order to protect the protective film forming layer 1 before using the chip protective film. May be.
Examples of release sheets include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polypinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, and polyurethane. Film, ethylene / vinyl acetate copolymer film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluorine A resin film or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  In particular, when the release sheet is peeled after the low-hardness layer 1a and the high-hardness layer 1b are cured, a polymethylpentene film, a polyethylene terephthalate film, or a polyimide film excellent in heat resistance can be suitably used.

  The surface tension of the release sheet is preferably 40 mN / m or less, and more preferably 35 mN / m or less. Such a release sheet having a low surface tension can be obtained by appropriately selecting the material, and can also be obtained by applying a silicone resin or the like to the surface of the sheet and performing a release treatment.

  The thickness of the release sheet is usually about 5 to 300 μm, preferably about 10 to 200 μm, and particularly preferably about 20 to 150 μm.

<Manufacturing method>
Next, an example of the manufacturing method of the chip protection film of the present invention will be described.
First, on the release surface of the release sheet 2, the composition containing each component constituting the low hardness layer is directly or transferred in accordance with generally known methods such as a roll knife coater, gravure coater, die coater, reverse coater and the like. The low hardness layer 1a is formed on the release sheet 2 by coating and drying. Separately, on the release surface of the release sheet 3, the composition containing each component constituting the high hardness layer is similarly applied and dried to form the high hardness layer 1 b on the release sheet 3. If necessary, the composition of each layer may be dissolved or dispersed in a solvent and applied. Next, the film for chip protection shown in FIG. 1 can be obtained by bonding the low hardness layer 1a and the high hardness layer 1b while heating.

<How to use>
Although it will not specifically limit if it is a chip protection use as a use application of the film for chip protection of this invention, For example, it can use for the chip back surface protection use for WL-CSP.
The usage method of the film in the case of applying the chip protection film of the present invention to the chip back surface protection for WL-CSP will be described with reference to FIGS. First, the release sheet 2 on the low-hardness layer 1a side is peeled off, and the low-hardness layer 1a is applied to the back surface of the wafer W in a state where the chip protection film is heated and pressurized at 40 ° C. or higher and 0.05 to 0.5 MPa. Bonding and cutting the film to wafer size. Next, as shown in FIG. 2, the film bonded to the wafer W is irradiated with 100 to 2000 mJ / cm ² of ultraviolet rays from the release sheet 3 side using the UV lamp 5, and the low hardness layer 1 a and the high hardness Layer 1b is cured. Thereby, a protective film having a two-layer structure can be formed on the back surface of the wafer.
Thereafter, the release sheet 3 on the high hardness layer 1b side is peeled off, and as shown in FIG. 3, a dicing tape 6 made of an adhesive formed on the substrate 8 and the substrate 8 is bonded to the high hardness layer 1b. The wafer W is diced. Thereby, the chip | tip protected with the film for protection can be obtained.

  EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited to a following example.

(Examples 1-4 and Comparative Examples 1-6)
Coating solutions for the low hardness layer and the high hardness layer were prepared by blending the components shown in Table 1 (Examples 1 to 4) and Table 2 (Comparative Examples 1 to 6).
In addition, as for the unit of the numerical value in Table 1 and Table 2, all are a mass part. Moreover, the code | symbol of each component in Table 1 and Table 2 is as follows.

A: Polymer component 1 (acrylic copolymer having a weight average molecular weight of 800,000 and a glass transition temperature of −10 ° C.)
B1: Energy ray curable component 1 (polyether type urethane acrylate resin, weight average molecular weight 7000)
B2: Energy ray curable component 2 (novolak type epoxy acrylate resin, weight average molecular weight 700)
B3: Energy ray curable component 3 (bisphenol A type epoxy acrylate resin, weight average molecular weight 2000)
B4: Thermosetting component (cresol novolac type epoxy resin)
C: Dye and pigment [Black pigment (azo)]
D: Silica [spherical synthetic silica (average particle size 3 μm)]
E1: Photopolymerization initiator 1 (2,4,6-trimethylbenzophenone, absorption wavelength 250 (334 nm))
E2: Photopolymerization initiator 2 (2,4,6-trimethylbenzoyldiphenylphosphine oxide, absorption wavelength 380 to 410 nm)
F1: Epoxy resin curing agent 1 [phenol resin (triphenylmethane novolak)]
F2: Epoxy resin curing agent 2 [imidazole compound (2-phenyl 4,5-dihydroxymethylimidazole)]

  Next, each coating solution of the above comparative example was applied and dried at 130 ° C./3 minutes on a release sheet made of a polyethylene terephthalate (PET) film having a thickness of 50 μm so that the dry film thickness was 40 μm. Thereafter, another release sheet same as the above was laminated thereon to prepare a three-layer energy ray-curable chip protection film comprising a release sheet / protective film forming layer (one layer) / release sheet.

  On the other hand, for each of the above examples, each coating solution for the high hardness layer was formed on a release sheet made of a polyethylene terephthalate (PET) film having a thickness of 50 μm so as to have a dry film thickness as shown in Table 1. The coating was dried. Separately, each coating solution for the low hardness layer was applied and dried on a release sheet made of a polyethylene terephthalate (PET) film having a thickness of 25 μm so as to have a dry film thickness as shown in Table 1. Next, the obtained high hardness layer and low hardness layer are bonded together while heating at 70 ° C., and release sheet / energy ray curable protective film forming layer (high hardness layer) / protective film forming layer (low hardness layer) / A film for chip protection having a four-layer structure composed of a release sheet was produced.

  About each chip | tip protective film, the pencil hardness of the protective film formation layer was measured with the following method. Further, laser mark recognizability, mounting reliability, and adhesion to the wafer were examined by the following methods. These results are shown in Tables 3 and 4.

<Pencil hardness>
The protective film forming layer was bonded to a silicon wafer at 80 ° C., and ultraviolet rays were irradiated at 1,000 mJ / cm ² using an ultraviolet irradiator (illuminance of 40 mW / cm ² for 25 seconds). Thereafter, the pencil hardness at room temperature (25 ° C.) was measured based on JIS standard: K5600-5-4.

<Laser mark recognition>
The release sheet on the low-hardness layer side of the protective film forming layer is peeled off, the low-hardness layer is bonded to the wafer, and ultraviolet rays are irradiated from the high-hardness layer side using an ultraviolet irradiator at 1,000 mJ / cm ² (illuminance 40 mW / cm ² for 25 seconds). Thereafter, the release sheet on the high hardness layer side was peeled off, and laser marking was performed (manufactured by Keyence: ML-G9320 used, character height 0.75 mm, character width 0.5 mm). Thereafter, the recognizability of laser marking printing was observed with a microscope.
Recognition evaluation was performed using a CCD camera mounted on a microscope. The case where the contrast value by the CCD camera exceeds 85% is marked as ◎, the case where it is 85% or less 70% or more, ◯, the case where it is less than 70%, 30% or more, Δ, and the case where it is less than 30%.

<Mounting reliability>
The release sheet on the low-hardness layer side of the protective film forming layer is peeled off, the low-hardness layer is bonded to the wafer, and ultraviolet rays are irradiated from the high-hardness layer side using an ultraviolet irradiator at 1,000 mJ / cm ² (illuminance 40 mW / cm ² for 25 seconds). Thereafter, the release sheet on the high hardness layer side was peeled off, and a dicing tape was bonded to the high hardness layer and diced to 10 mm × 10 mm. Each divided silicon chip was treated in a constant temperature and humidity chamber of 85 ° C./85% RH for 168 hours, and then heated in an IR reflow furnace at 250 ° C./120 seconds. Thereafter, the presence or absence of peeling between the obtained silicon chip and the protective film layer was observed with SAT (ultrasonic imaging device: manufactured by Hitachi Construction Machinery Finetech Co., Ltd.). Of the 20 samples, those in which peeling occurred were counted.

<Adhesion test>
The low-hardness layer of the protective film forming layer was bonded to a silicon wafer, and irradiated with ultraviolet rays at 1,000 mJ / cm ² (illuminance 40 mW / cm ² for 25 seconds) using an ultraviolet irradiator. After a 1 mm × 1 mm square cut was made on the film surface (half cut using a dicer), the obtained sample was treated in a constant temperature and humidity chamber of 85 ° C./85% RH for 168 hours. Cellophane tape (registered trademark) was tightly adhered to the place where the grid was formed, and the end of the tape was rapidly peeled off at an angle of 45 ° to confirm the state of the grid. When the film of 1 mm × 1 mm was peeled off by 70% or more, ×, 5 to 70% were Δ, and 5% or less were ○.

In Comparative Example 1, there is no problem in hardness and adhesion after curing, but since the pigment is not included, the laser mark recognizability is insufficient. In Comparative Example 2, both hardness and adhesion are insufficient. In Comparative Examples 3-5, although hardness is high, it is inferior to adhesiveness. In Comparative Example 6, since the energy ray curable component and the photopolymerization initiator are not included, the ultraviolet ray is not cured and the hardness for the chip protection film is insufficient.
On the other hand, in Examples 1-4, there was no problem in any of the hardness of the high hardness layer which is a film surface layer, laser mark recognizability, mounting reliability, and adhesiveness.

It is sectional drawing which shows an example of the film for chip | tip protection of this invention. It is sectional drawing for demonstrating the hardening method of the film for chip protection of this invention. Sectional drawing for demonstrating the dicing method of the wafer with a film for chip protection of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Protective film formation layer 1a Low hardness layer 1b High hardness layer 2,3 Release sheet 5 UV lamp 6 Dicing tape 7 Adhesive 8 Base material

Claims (15)

A low-hardness layer bonded to the chip, and a high-hardness layer provided on the low-hardness layer directly or via another layer,
The film for chip protection, wherein the high hardness layer is an energy ray curable resin layer containing a binder polymer component, an energy ray curable component, and a photopolymerization initiator.   The film for chip protection according to claim 1, wherein the low hardness layer contains a binder polymer component, an energy ray curable component and / or a thermosetting component.   3. The chip protection film according to claim 1, wherein the energy curable component is at least one selected from the group consisting of epoxy acrylate, urethane acrylate, and oligoester acrylate. 4.   The film for chip protection according to claim 2 or 3, wherein the energy ray curable component of the low hardness layer is bisphenol A type epoxy acrylate.   5. The chip protection film according to claim 2, wherein the energy ray curable component of the low hardness layer is an epoxy acrylate having a weight average molecular weight of 1000 or more.   The chip protection film according to claim 2, wherein the low hardness layer further contains a photopolymerization initiator.   7. The chip protecting film according to claim 1, wherein the energy ray curable component of the high hardness layer is a novolac type epoxy acrylate. 8.   The film for chip protection according to any one of claims 1 to 7, wherein the energy ray curable component of the high hardness layer is an epoxy acrylate having a weight average molecular weight of less than 1000.   The high hardness layer has a pencil hardness of 3H or more, and the low hardness layer has a pencil hardness of 4H or less, provided that the hardness is relatively lower than the pencil hardness of the high hardness layer. The film for chip protection according to any one of claims 1 to 8.   The film for chip protection according to any one of claims 1 to 9, wherein the photopolymerization initiator is a photopolymerization initiator that absorbs light in a long wavelength region of 350 nm or more.   The film for chip protection according to claim 10, wherein the photopolymerization initiator is acylphosphine oxide. The film for chip protection according to claim 11, wherein the photopolymerization initiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide represented by the following structural formula (1).

Structural formula (1)

  The film for chip protection according to any one of claims 1 to 12, wherein the high hardness layer further contains a filler.   The chip protection film according to claim 1, wherein the high hardness layer further contains a dye and / or a pigment. The chip protection device according to any one of claims 1 to 14, wherein a peelable release sheet is provided on one or both of the lower surface of the low hardness layer and the upper surface of the high hardness layer. the film.