JP2008166451A - Chip protection film - Google Patents

Abstract

Provided is a chip protective film capable of performing laser marking with high recognizability and accuracy without curing a protective film forming layer when using a chip protective film.
A film 1 for protecting a chip of a semiconductor wafer having at least two chip protective film forming layers, the outermost layer 2 having a pencil hardness at 25 ° C. of B or higher and a probe tack at 250 ° C. The peak value is 150 mN / mm ² or less, the elastic modulus at 25 ° C. is 1.0 × 10 ^{8 to} 3.0 × 10 ¹⁰ Pa, and the elastic modulus at 250 ° C. is 1.0 × 10 ⁶ Pa or more. A film for chip protection.
[Selection] Figure 1

Description

  The present invention relates to a chip protection film that can efficiently form a protective film on the back surface of a semiconductor chip and that can improve the manufacturing efficiency of the chip, and more particularly to the manufacture of a semiconductor chip mounted by a so-called face down method. It is related with the film for chip protection used.

2. Description of the Related Art In recent years, semiconductor devices have been manufactured using a so-called “face down” mounting method. In the face-down method, a chip in which convex portions called bumps are formed on the circuit surface side of the chip is used, and the convex portions on the circuit surface side are connected to the base.
Such a semiconductor device is generally manufactured through the following steps.
(1) A circuit is formed on the surface of the semiconductor wafer by an etching method or the like, and bumps are formed at predetermined positions on the circuit surface.
(2) The back surface of the semiconductor wafer is ground to a predetermined thickness.
(3) The back surface of the semiconductor wafer is fixed to a dicing sheet stretched on the ring frame, and is cut and separated for each circuit by a dicing saw to obtain a semiconductor chip.
(4) A semiconductor chip is picked up and mounted on a predetermined base in a face-down manner, and if necessary, resin sealing or resin coating is applied to the back surface of the chip to obtain a semiconductor device.

The resin sealing is performed by a potting method in which an appropriate amount of resin is dropped and cured on a chip, a molding method using a mold, or the like. However, it is difficult to drop an appropriate amount of resin by the potting method. In the mold method, it is necessary to clean the mold, and the equipment cost and operation become expensive.
Moreover, since it is difficult to apply an appropriate amount of resin uniformly, the resin coating may vary in quality. Therefore, there is a demand for the development of a technique that can easily form a highly uniform protective film on the back surface of the chip.

  Further, in the back surface grinding in the above step (2), fine streak scratches are formed on the back surface of the chip by mechanical grinding. This minute scratch may cause cracking after the dicing step (3) or packaging. For this reason, conventionally, a chemical etching process for removing minute scratches may be necessary after mechanical grinding. However, the chemical etching process requires not only equipment costs and operation costs, but also increases costs.

Therefore, even if a minute scratch is formed on the back surface of the chip by mechanical grinding, there is a demand for the development of a technique that eliminates the adverse effects caused by the scratch.
In order to solve this problem, a highly uniform protective film can be easily formed on the back surface of the chip, and even if minute scratches are formed on the back surface of the chip by mechanical grinding, adverse effects caused by such scratches can be eliminated. A process and a film for protecting a chip used in the process have been proposed (see, for example, Patent Documents 1, 2, and 3).
Moreover, a method for marking such a protective film with a laser beam is known. (For example, refer to Patent Document 4).
JP 2004-214288 A JP 2004-260190 A JP 2004-331728 A JP 2006-140348 A

Until now, in a semiconductor device including a resin-sealed chip, a product number or the like may be printed on the surface of the sealing resin by a laser marking method or the like. The laser marking method is a technique in which a resin surface is scraped off by laser light to perform printing.
As a process of marking on the film for chip protection,
(1) Affixing a chip protection film to the backside of the wafer (2) Curing the protection film by heating or the like (cure)
(3) A process of applying laser marking to the protective film after curing is taken.
However, with this method, as described in Patent Document 4, there is a problem that wafer warpage occurs after curing, laser marking cannot be performed with high accuracy, and wafer conveyance becomes difficult. In order to solve this in the above-mentioned Patent Document 4, heat curing is performed in a state of being fixed to a ring frame. Even in this case, wrinkles are generated in the protective film during heat curing, and therefore laser marking is performed with high accuracy. In addition, there were problems such as being unable to dice with high precision, and this was not satisfactory. In order to avoid this, when laser marking is performed before the protective film is cured, there is a problem that the recognizability of the laser marking is lowered after heat curing or the laser marking cannot be performed with good recognizability.

  The present invention has been made in view of the prior art as described above, and performs laser marking with high recognizability and accuracy without curing the protective film forming layer when using a chip protection film for a semiconductor wafer. An object of the present invention is to provide a film for chip protection that can be used.

  As a result of intensive studies to solve the above-mentioned problems, a chip protection film having at least two layers, the outermost layer comprising a layer obtained by curing a curable component or a heat-resistant film, and having specific physical properties is used. Thus, it was found that laser marking can be performed with high visibility and accuracy even if the step of curing the protective film forming layer is omitted during use. The present invention has been made based on such findings.

That is, the present invention
(1) A chip protective film having at least two chip protective film forming layers, the outermost layer having a pencil hardness at 25 ° C. of B or higher and a peak value of probe tack at 250 ° C. of 150 mN / mm with ² or less, and wherein the at elastic modulus at ^{25 ℃ 1.0 × 10 8 ~3.0 ×} 10 10 Pa and the elastic modulus at 250 ° C. is 1.0 × ¹⁰ 6 Pa or more Chip protection film,
(2) The film for chip protection according to (1), wherein the outermost layer comprises a cured curable protective film forming layer or a heat resistant film,
(3) The chip protective film according to (1) or (2), wherein the outermost layer and the layer other than the outermost layer have different colors, and (4) a layer that adheres to the chip of the chip protective film. Is made of a thermosetting adhesive layer, and the storage elastic modulus (G ′) at 100 ° C. before curing of the curable adhesive layer is 1.0 × 10 ^{4 to} 5.0 × 10 ⁶ Pa. The film for protecting a chip according to any one of (1) to (3),
Is to provide.

  According to the present invention, a highly uniform protective film can be easily formed on the back surface of the chip, and laser marking can be performed with high visibility and accuracy without curing the protective film forming layer with an electron beam or ultraviolet rays. The step of curing the protective film forming layer can be omitted. In addition, this can solve problems such as conveyance associated with the warped wafer after curing.

The film for chip protection of the present invention has at least two protective film forming layers, and the outermost layer is formed of a layer obtained by curing the curable protective film forming layer or a heat resistant film. Here, the outermost layer refers to the outermost layer on the side that is not in contact with the chip of the chip protection film during use.
Hereinafter, the film for protecting a chip of the present invention will be described in more detail with reference to the drawings.
As shown in FIGS. 1 and 2, a chip protection film 1 according to the present invention has at least two protective film forming layers 2 and 3, and a release sheet 4 is temporarily attached to both sides or one side as required. May be. Therefore, the layers 3 other than the outermost layer 2 of the protective film forming layer constituting the chip protection film of the present invention may be composed of not only a single layer but also a plurality of layers.

(Peeling sheet)
The film for chip protection of the present invention may be temporarily attached with a release sheet on one side or both sides for the purpose of protecting the outermost layer and other layers before use.
Examples of release sheets include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polychlorinated pinyl film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, and polyurethane film. , Ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. . These crosslinked films are also used. Furthermore, these laminated films may be used.

Furthermore, the surface tension of the release sheet is 40 mN / m or less, 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.

(Protective film forming layer)
The protective film-forming layer of the film for chip protection used in the present invention is preferably a curable protective film-forming layer or a heat-resistant film in which the outermost layer is cured. Is not particularly limited. The layer in contact with the chip of the protective film forming layer has a function of adhering to the chip. The layer in contact with the chip is preferably a curable adhesive layer containing a thermosetting component and the like from the viewpoint of the manufacturing process and cost.

(Hardened curable protective film forming layer)
As the curable component used in the cured curable protective film forming layer that is the outermost layer of the protective film forming layer of the present invention, a thermosetting component, an energy ray curable component, or a mixture thereof may be used. However, it is particularly preferable to use a thermosetting component from the viewpoint of heat resistance.
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.

(Epoxy resin)
In the present invention, the epoxy resin used as the thermosetting component of the outermost layer is not particularly limited as long as it cures and exhibits an adhesive action, but is bifunctional or more, preferably a molecular weight of less than 5000, more preferably Can use less than 3000 epoxy resin. Further, an epoxy resin having a 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.

(Phenolic resin)
As the phenolic resin used as the thermosetting component of the outermost layer, condensates of phenols such as alkylphenols, polyhydric phenols and naphthols with aldehydes are used without particular limitation. Specific examples of the phenolic resin preferably used in the present invention include phenol novolak resin, o-cresol novolak resin, p-cresol novolak resin, t-butylphenol novolak resin, dicyclopentadiene cresol resin, polyparavinylphenol. Resin, bisphenol A type novolak resin, or modified products thereof are used.
The phenolic hydroxyl group contained in these phenolic resins can easily undergo an addition reaction with the epoxy group of the previous epoxy resin by heating to form a cured product having high impact resistance. For this reason, you may use together an epoxy resin and a phenol-type resin.

(Thermally activated latent epoxy resin curing agent)
When an epoxy resin is used, a thermally activated latent epoxy resin curing agent can be used in combination as an auxiliary agent.
Thermally activated latent epoxy resin curing agent is a type of curing agent that does not react with epoxy resin at room temperature but is activated by heating above a certain temperature and reacts with epoxy resin. Thermally activated latent epoxy resin curing agent The activation method is a method in which active species (anions and cations) are generated by a chemical reaction by heating; it is stably dispersed in the epoxy resin near room temperature, and is compatible with and dissolved in the epoxy resin at a high temperature. There is a method of starting a curing reaction by eluting at a high temperature with a molecular sieve encapsulated type curing agent; a method using a microcapsule, and the like.

  Specific examples of the thermally activated latent epoxy resin curing agent include various onium salts, high melting point active hydrogen compounds such as dibasic acid dihydrazide compounds, dicyandiamides, amine adduct curing agents, and imidazole compounds. 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, for example, from Shikoku Kasei Kogyo Co., Ltd. under the trade names 2E4MZ, 2PZ-CN, and 2PZ-CNS.

  With respect to the cured curable protective film forming layer used for the outermost layer, it is advantageous in terms of manufacturability to quickly cure, so the blending amount of the thermally activated latent epoxy resin curing agent as described above is It is preferable to set it as 1-15 mass% with respect to the total amount with an epoxy resin and a phenol resin, and it is more preferable to set it as 3-10 mass%. If the blending amount of the epoxy resin curing agent is less than 1% by mass, it takes time to cross-link, resulting in poor productivity. When it exceeds 15 mass%, bubbles tend to be generated due to the sublimation of the epoxy resin curing agent in the curing step, resulting in poor appearance.

(Energy ray curable component)
The energy ray-curable component used for forming the outermost layer of the present invention comprises a compound that is polymerized and cured when irradiated with energy rays such as ultraviolet rays and electron beams. This compound has at least one polymerizable double bond in the molecule, and usually has a molecular weight of about 100 to 30,000, preferably about 300 to 10,000,000. Specific examples of such energy beam polymerization type compounds include trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, and 1,4. -Use of butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, oligoester acrylate, polyester-type or polyether-type urethane acrylate oligomer, polyester acrylate, polyether acrylate, epoxy-modified acrylate, etc. Can do. Among these, in the present invention, an ultraviolet curable resin is preferably used, and specifically, an oligoester acrylate, a urethane acrylate oligomer, or the like is particularly preferably used.

(Photopolymerization initiator)
By mixing a photopolymerization initiator in the energy ray curable component, the polymerization curing time and the amount of light irradiation can be reduced. Specific examples of such a photopolymerization initiator 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, Examples include 2,4-diethylthioxanthone, α-hydroxycyclohexyl phenyl ketone, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, and the like. The photopolymerization initiator is desirably used in a proportion of about 1.5 to 4.5 parts by weight, preferably about 2.4 to 3.8 parts by weight, with respect to 100 parts by weight of the energy beam curable component in the previous period.

(Polymer component)
In the present invention, in order to further improve the flexibility and operability as a protective film, a polymer component other than the curable component can be used. The weight average molecular weight of this polymer is usually in the range of 30,000 to 2,000,000, preferably 100,000 to 1,500,000, particularly preferably 200,000 to 1,000,000. If the molecular weight is too low, film formation will be insufficient, and if it is too high, compatibility with other components will deteriorate, resulting in hindering film formation.
As such a polymer, for example, an acrylic copolymer, a polyester resin, a urethane resin, a silicone resin, a rubber-based polymer and the like are used, and an acrylic copolymer is particularly preferably used. In addition to the above-described energy curable component, energy ray curability can be imparted by using an acrylic copolymer having a carbon-carbon double bond.
In addition, a phenoxy resin can be used to improve flexibility and operability. The phenoxy resin is usually a thermoplastic resin having a molecular weight of 10,000 or more obtained from bisphenol such as bisphenol A and epichlorohydrin. This phenoxy resin is characterized by good compatibility and good adhesion because of its similar structure to the epoxy resin. Preferable phenoxy resins are those having a main skeleton of bisphenol A type, and other preferable examples include commercially available phenoxy resins such as bisphenol A / F mixed phenoxy resins and brominated phenoxy resins.

(Filler)
Furthermore, the filler may be mix | blended with the structure of the protective film formation layer of a film. 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 protective film forming layer, 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 from 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 a protective film formation layer, the following functional fillers other than the inorganic filler mentioned above may be mix | blended. For example, for the purpose of imparting conductivity, a conductive filler such as gold, silver, copper, nickel, aluminum, stainless steel, carbon, or ceramic, or nickel, aluminum, etc. coated with silver may be added. For the purpose of imparting thermal conductivity, a thermal conductive material such as a metal material such as gold, silver, copper, nickel, aluminum, stainless steel, silicon, germanium, or an alloy thereof may be added.
The amount of filler added to the protective film forming layer varies depending on the type of filler, but is generally 30 to 90% by mass, preferably 50 to 85% by mass, based on all components forming the protective film forming layer. Is appropriate. The thermal expansion coefficient of the protective film after curing can be brought close to the thermal expansion coefficient of the wafer, thereby reducing the warpage of the wafer caused by the difference in the thermal expansion coefficient during processing. If the wafer is warped, it is easily damaged and difficult to carry.

(Coupling agent)
Furthermore, a coupling agent can also be added to the protective film-forming layer for the purpose of improving the adhesion and adhesion between the outermost layer after curing and the other adhesive layer. The coupling agent can improve the adhesiveness and adhesion to the adhesive layer without impairing the heat resistance of the cured film, and also improve the water resistance (moisture heat resistance). The coupling agent is preferably a silane (silane coupling agent) because of its versatility and cost merit.

(Pigment / Dye)
In the present invention, it is preferable that the color of the outermost layer of the protective film forming layer is different from the color of the layer other than the outermost layer. A pigment and a dye can be added to the protective film forming layer in order to improve the recognizability of the formed laser marking. Examples of such pigments include carbon black and various inorganic pigments. Also, various organic dyes such as azo, indanthrene, indophenol, phthalocyanine, indigoid, nitroso, xanthene, and oxyketone are listed.
The amount of pigment and dye added varies depending on the type, but generally 0.3 to 20% by mass, preferably about 1 to 15% by mass of the total components forming the protective film forming layer 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.

  For example, the pigment is added to the outermost layer of the protective film forming layer, the pigment is not added to any layer other than the outermost layer that adheres to the chip, and the outermost layer and the layer that adheres to the chip are set to have different colors. Thus, only the outermost layer can be partly removed by laser irradiation, and the layer that adheres to the chips of different colors can be exposed, and the recognizability of printing can be improved. In addition, the pigment may not be added to the outermost layer, and the pigment may be added to the layer that adheres to the chip, or pigments of different colors may be added to the outermost layer and the layer that adheres to the chip.

  The outermost layer of the protective film forming layer used in the present invention and the protective film forming layer containing a curable adhesive that adheres to the chip are composed of a roll knife coater containing a composition comprising the above components on the release surface of the release sheet. A gravure coater, die coater, reverse coater or the like can be obtained by coating or drying by direct or transfer according to generally known methods. In addition, said composition can be apply | coated after making it melt | dissolve or disperse | distribute to a solvent as needed.

  When the outermost cured protective film forming layer is thermosetting, it can be obtained by adding a large amount of an epoxy resin curing agent and curing at 100 to 160 ° C. for 3 to 50 minutes simultaneously with drying. . With respect to the cured protective film forming layer, the cured component is preferably in a state of being completely cured rather than semi-cured. Complete curing means that the reaction of the curing component has been completed, and in a semi-cured state, it exhibits high fluidity when heated to about 100 ° C. or higher, but when fully cured, there is no fluidity. For this reason, the outermost layer excellent in heat resistance can be obtained. In addition, when the outermost cured protective film forming layer is energy ray curable, a cured protective film forming layer can be obtained by applying an energy ray after coating and producing a film once. .

(Heat resistant film)
As the outermost layer of the present invention, a heat resistant film can be used in addition to the cured protective film forming layer. Here, since the chip using the film for chip protection is heated at a high temperature such as a reflow process, the heat-resistant film used for the outermost layer is preferably a film having a high melting point. Specifically, those having a melting point of 200 ° C. or higher are preferable. If the melting point is less than 200 ° C., it may melt and retain its shape when heated at a high temperature such as in a reflow process, and may be fused with peripheral devices. Specifically, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polycarbonate film, a polyimide film, a fluororesin film, or the like is used.

This cured protective film forming layer or heat resistant film, which is the outermost layer of the present invention, has an elastic modulus at room temperature (25 ° C.) of 1.0 × 10 ^{8 to} 3 × 10 ¹⁰ Pa, preferably 1.0 ×. The elastic modulus at 10 ^{9 to} 2 × 10 ¹⁰ Pa and 250 ° C. is 1.0 × 10 ⁶ Pa or more, preferably 1.0 × 10 ⁷ to 1.0 × 10 ⁹ Pa. If the elastic modulus at room temperature (25 ° C.) is 1.0 × 10 ⁸ Pa or less, the resin is not completely cured, which causes a problem in heat resistance when heated. When it is 3 × 10 ¹⁰ Pa or more, flexibility as a film is insufficient, and it becomes difficult to obtain a roll shape. If the elastic modulus at 250 ° C. is too low, the strength in the reflow process is insufficient, which is disadvantageous in terms of mounting reliability.
The outermost layer of the present invention has a pencil hardness of B or higher at room temperature (25 ° C.). If the hardness is too low, scars on the robot arm and suction table during wafer transfer will remain.

Further, the peak value of the probe tack in the outermost layer is 250 ° C. of the present invention is 150 mN / mm ² or less, preferably 50 mN / mm ² or less. If this value is too high, the film surface is softened in the reflow process or the like and cannot be prevented from being transferred to other members. In general, the peak value of probe tack is the maximum strength when a cylinder (probe with a diameter of 3 to 5 mm) made of metal is pressed against the adhesive surface with a certain pressure, time, temperature, etc., and peeled off at a certain speed. The value measured as. In the present invention, the “peak value of the probe tack” uses a cylindrical probe having a diameter of 3 mm, a contact speed of 0.5 mm / s, a contact load of 694 mN / mm ² , a contact time of 10 seconds, and a peeling speed of 10 mm. / S measured at 250 ° C.

(Adhesive layer in contact with the chip)
Among the chip protective film forming layers of the present invention, the layer in contact with the chip is not particularly limited as long as it has a function of adhering to the chip, but curing including a thermosetting component from the viewpoint of the manufacturing process and cost. The adhesive layer is preferable. As the component, those similar to the hardened curable protective film forming layer of the outermost layer can be used. For this layer, since it is necessary to have adhesiveness in a semi-cured state, the blending amount of the thermally activated latent epoxy resin curing agent is 0.01 to the total amount of the epoxy resin and the phenol resin. The content is preferably 5% by weight, more preferably 0.05 to 3% by weight, and still more preferably 0.2 to 3% by weight. When the blending amount of the curing accelerator is less than 0.01% by weight, the epoxy resin is insufficiently cross-linked, and the heat resistance tends to decrease. When the amount exceeds 5% by weight, the storage stability decreases. There is a tendency for pot life to be insufficient.
In addition, regarding the adhesive layer in contact with the chip, G ′ (storage elastic modulus) at 100 ° C. is 1.0 × 10 ^{4 to} 5.0 × 10 ⁶ Pa, and further 5.0 to omit the curing step. It is preferable that it is * 10 < ⁴ > -1.0 * 10 < ⁶ > Pa. When G ′ is 1.0 × 10 ⁴ or less, the protective film is excessively softened in a heating step such as resin sealing or reflow treatment, and thus the protective film is peeled off. On the other hand, if it is 5.0 × 10 ⁶ or more, the sticking property to the chip at a low temperature (20 to 80 ° C.) is deteriorated, and the sticking at a high temperature (80 ° C. or more) is required.

The adhesive layer in contact with the chip can also be obtained by the same method as that for forming the outermost cured protective film. A film for chip protection can be obtained by bonding the adhesive layer in contact with the obtained chip to a cured protective film forming layer or a heat resistant film.
For example, by adding a pigment to the outermost layer and not adding a pigment to the layer that adheres to the chip, and by designing the outermost layer and the layer that adheres to the chip to have different colors, only the outermost layer is scraped off during laser marking. The layer that adheres to chips of different colors can be exposed, and the visibility of printing can be improved. In addition, the pigment may not be added to the outermost layer, the pigment may be added to the layer that adheres to the chip, the pigment of a different color may be added to the outermost layer and the layer that adheres to the chip, etc. A combination with different adhesive layers may be used.
The total thickness of the protective film forming layer is usually 3 to 200 μm, more preferably 10 to 60 μm.

As shown in FIG. 3, the chip protection film of the present invention is formed by forming a circuit (not shown) on the surface of the chip protection film 1 and forming bumps at predetermined positions on the circuit surface (FIG. The protective film forming layer 3 side other than the outermost layer of the chip protective film 1 is bonded to the back surface of the semiconductor wafer 6 whose back surface is ground to a predetermined thickness, and a release sheet 4 (see FIG. 1). ) Is removed. And it adheres to a semiconductor wafer, without the need to harden a protective film formation layer. The outermost layer is partially scraped off by a known laser irradiation such as a TEA laser or a YAG laser on the surface of the protective film forming layer that is in close contact, thereby forming a marked protective film forming layer.
Thereafter, the protective film surface is bonded to a dicing tape stretched on a ring frame, and a semiconductor chip is cut and separated for each circuit by a dicing saw to obtain a semiconductor chip. The obtained semiconductor chip is picked up and mounted on a predetermined base by a face-down method.
In order to protect the semiconductor chip, there is almost no need for resin sealing or resin coating on the back surface of the chip.

EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited to a following example.
A curable coating agent for a protective film-forming layer comprising the following components is prepared in a mixed amount shown in Table 1 to form “protective films 1 to 6” to be the protective film-forming layers. In addition, the numerical value in Table 1 shows a composition, and all the units are a mass part.
A: Epoxy resin (1)
Liquid bisphenol A epoxy resin (epoxy equivalent 180-200)
B: Epoxy resin (2)
o-Cresol novolac type epoxy resin (epoxy equivalent 210-230)
C: Phenol resin Phenol novolak resin (hydroxyl equivalent: 110-140)
D: Latent epoxy resin curing agent (1)
Dicyandiamide (average particle size 5μm)
E: Latent epoxy resin curing agent (2)
Imidazole compound (2-phenyl 4,5-dihydroxymethylimidazole)
F: Energy ray-curable component Dipentaerythritol hexaacrylate G: Photopolymerization initiator α-hydroxycyclohexyl phenyl ketone H: Polymer component Acrylate ester copolymer (epoxy group-containing, molecular weight 800,000, Tg 10 ° C.)
I: Filler Synthetic silica filler (average particle size 0.5 μm)
J: Pigment / dye Carbon black (average particle size 28 nm)

Next, the manufacturing method of the film for chip | tip protective films of each Example and a comparative example is shown.
[Example 1]
The coating agent described in Table 1 for forming the protective film 1 which is the outermost layer of the protective film forming layer is applied on a release sheet (PET film, thickness 38 μm) at 150 ° C. for 20 minutes so that the dry film thickness becomes 30 μm. Dry and heat cure. Subsequently, the coating agent for the protective film 3 on the wafer side of the protective film forming layer is applied and dried on another release sheet at 150 ° C. for 3 minutes so that the dry film thickness is 10 μm, and laminated with the protective film 1. A film for chip protection of release sheet / outermost protective film forming layer (protective film 1) / adhesive layer in contact with the chip (protective film 3) / release sheet (see FIG. 1) was obtained.
[Example 2]
The outermost protective film 1 of Example 1 was changed to a protective film 2 and applied and dried at 150 ° C. for 3 minutes so that the dry film thickness was 30 μm, and then irradiated with ultraviolet rays so as to have an integrated amount of 2000 mJ. Made a film. Then, it laminated | stacked with the protective film 3 like Example 1, and obtained the film for chip | tip protection.
[Example 3]
A chip protecting film was obtained in the same manner as in Example 1 except that the dry film thickness of the protective film 1 of the outermost layer of Example 1 was 15 μm and the dry film thickness of the protective film 3 in contact with the chip was 25 μm.
[Example 4]
A film for protecting the chip was obtained in the same manner as in Example 3 except that the protective film 3 in contact with the chip of Example 3 was changed to the protective film 4.
[Example 5]
A chip protecting film was obtained in the same manner as in Example 3 except that the protective film 3 in contact with the chip of Example 3 was changed to the protective film 5.
[Example 6]
A film for chip protection was obtained in the same manner as in Example 3 except that the protective film 3 in contact with the chip of Example 3 was changed to the protective film 6.
[Example 7]
The coating agent for forming the protective film 5 was applied and dried on a release sheet at 150 ° C. for 3 minutes so that the dry film thickness was 27.5 μm, and a polyimide film (“UPILEX-S” (trade name, manufactured by Ube Industries, 12.5 μm thick) to obtain a chip protection film of adhesive layer (protective film 5) / release sheet (see FIG. 2) in contact with the outermost heat-resistant film / chip.

[Comparative Example 1]
A chip protecting film was obtained in the same manner as in Example 1 except that the drying time of the outermost protective film 1 of Example 1 was 150 ° C. to 3 minutes.
[Comparative Example 2]
A chip protecting film was obtained in the same manner as in Example 1 except that the outermost protective film 1 of Example 1 was used as the protective film 6 and the protective film 3 in contact with the chip was used as the protective film 1.
[Comparative Example 3]
A film for protecting the chip was obtained in the same manner as in Example 4 except that the drying time of the protective film 1 of the outermost layer of Example 4 was set to 150 ° C. to 3 minutes.
[Comparative Example 4]
The coating agent for the protective film 3 is applied, dried and heat-cured at 150 ° C. for 20 minutes so that the dry film thickness is 40 μm on the release sheet, and then another release sheet is laminated on the surface of the obtained protective film forming layer. A film for protecting the chip of release sheet / single-layer protective film forming layer (protective film 3) / release sheet was obtained.

  Protective forming layers (protective films 1-6, heat-resistant films), protective film-forming layers in contact with the wafer (protective films 1-6), chip protective films, which are the outermost layers of the examples and comparative examples thus formed About the following, the evaluation test of each following characteristic was done. The obtained results are shown in Table 2 (Tables 2-1 and 2-2).

(1) Pencil hardness The pencil hardness at room temperature (25 ° C.) was measured according to JIS standard: K5600-5-4.
(2) Peak value of probe tack The peak value (tack force) of the probe tack before and after UV irradiation of the adhesive layer on the adherend side is determined by using a tacking tester, TAC-II type manufactured by Resuka Co., Ltd. And measured. The measurement conditions are as follows.
Probe: 3 mmφ cylindrical probe Contact speed of probe: 0.5 mm / s
Contact load: 694 mN / mm ²
Contact time: 10 seconds Peeling speed: 10 mm / s
Measurement temperature: 250 ° C
The results were measured five times and the average value was taken.

(3) Modulus of elasticity In the protective film forming layer in which the outermost layer is cured, the coating agent comprising the respective components forming the protective films 1 to 6 is dried on the release sheet in the same manner as in the preparation of the outermost layer of the chip protection film. The film was applied and dried so that the dry film thickness was 100 μm under the conditions. In the adhesive layer that adheres to the chip, the coating film composed of the components forming the protective films 1 to 6 is dried on the release sheet under the same drying conditions as those for preparing the layer that contacts the chip of the chip protection film. The film was applied and dried to form a film having a thickness of 100 μm. The elastic modulus of the obtained film was measured with a viscoelasticity measuring device (tensile mode, frequency 10 Hz, temperature rising rate 10 ° C./min). The storage elastic modulus at 100 ° C. was measured using a viscoelasticity meter (manufactured by Rheometric Science Co., Ltd., trade name: ARES), starting from 0 ° C., with a heating rate of 20 ° C./min and a frequency of 1 Hz. The elasticity was measured and taken as the storage elastic modulus (G ′) when the temperature reached 100 ° C.
(4) Laser mark recognition (before cure)
The film for chip protection was bonded to a silicon wafer, and laser marking was performed (manufactured by Keyence: ML-G9320 used, character height 0.75 mm, character width 0.5 mm). Then, after heat-processing a protective film formation layer at 180 degreeC-2h, the recognizability of the printing of a laser marking was observed with the microscope. Recognition evaluation was performed using a CCD camera mounted on a microscope. The case where the contrast value by the CCD camera is 85% or more is indicated by “◎”, the case of 85-70% is indicated by “◯”, the case of 70-30% is indicated by “Δ”, and the case of less than 30% is indicated by “X”.

(5) Bondability When bonding a film for chip protection to a silicon wafer, “○” indicates that the film can be bonded at 20 ° C. to 80 ° C., and “X” indicates that 80 ° C. or higher is required for bonding. did.
(6) Adhesion reliability (no cure)
The film for chip protection was bonded to a silicon wafer, a dicing tape was bonded to the film side, 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 265 ° C. for 30 seconds. Then, the presence or absence of peeling between the obtained silicon chip and the curable protective film forming 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.

(7) Adhesion reliability (with cure)
The film for chip protection was bonded to a silicon wafer and cured by heating at 180 ° C. for 2 hours. Dicing tape was bonded to the film side 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 265 ° C. for 30 seconds. Then, the presence or absence of peeling between the obtained silicon chip and the curable protective film forming 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.
(8) Heat resistance A film for chip protection was bonded to a silicon wafer, laser-marked, a dicing tape was bonded to the film side, and diced to 10 mm × 10 mm. When the protective film forming side of each divided silicon chip was placed on a hot plate at 300 ° C. for 30 seconds, it was confirmed that there was no transfer to the hot plate and no laser mark peeling. “○” indicates that no transfer or laser mark peeling occurred, and “X” indicates that transfer or laser mark peeling occurred.

  In Examples 1 to 3, since the softening of the layer bonded to the wafer was large, the adhesion reliability was slightly low without curing, but there was no problem in adhesion reliability with curing, and laser marking before curing was possible. Regarding Examples 4 to 7, there was no problem in adhesion reliability even without curing, and laser marking was possible even before curing. In addition, in the configuration in which the outermost layer of Examples 4, 5, and 7 and the layer in contact with the chip were two layers of different colors, the superiority in laser mark recognition was clearly confirmed.

In all of the comparative examples, the outermost layer is not completely cured, so that the pencil hardness is soft and the tack force is large.
In Comparative Example 1, since the heating time was insufficient and the protective film 1 of the outermost layer was not completely cured, even if laser marking was performed before curing, the laser marking disappeared by subsequent curing. There was also a problem with heat resistance.
In Comparative Example 2, the outermost protective film 6 was not cured completely because of its slow curing rate, and there was a problem in laser marking property and heat resistance before curing as in Comparative Example 1. Further, the protective film 1 that adheres to the chip has a problem in terms of pasting property and adhesion reliability because of the progress of curing.
In Comparative Example 3, since the outermost layer and the layer in contact with the chip are two layers having different colors, the laser marking property before curing was good, but since the outermost layer was not cured, there was a problem in terms of heat resistance. was there.
Since the comparative example 4 has a single-layer structure in which the curing has progressed to some extent, there is a problem in adhesion reliability and the like.

It is sectional drawing of the film for chip protection of this invention. It is sectional drawing of another example of the film for chip protection of this invention. It is sectional drawing which bonded the film for chip protection of this invention to the semiconductor wafer, and marked on the film surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film for chip protection 2 Protective film formation layer or heat-resistant sheet of outermost layer 3 Protective film formation layer adhered to chip 4 Release sheet 5 Portion of outermost layer removed by laser marking

Claims (4)

A film for protecting a chip of a semiconductor wafer having at least two chip protective film forming layers, and the outermost layer has a pencil hardness at 25 ° C. of B or more and a peak value of probe tack at 250 ° C. of 150 mN / mm with ² or less, and wherein the at elastic modulus at ^{25 ℃ 1.0 × 10 8 ~3.0 ×} 10 10 Pa and the elastic modulus at 250 ° C. is 1.0 × ¹⁰ 6 Pa or more Chip protection film.   2. The chip protection film according to claim 1, wherein the outermost layer is formed of a cured curable protective film forming layer or a heat resistant film.   The film for chip protection according to claim 1, wherein the outermost layer and a layer other than the outermost layer have different colors. The layer that adheres to the chip of the film for chip protection consists of a thermosetting adhesive layer, and the storage elastic modulus (G ′) at 100 ° C. before curing of the curable adhesive layer is 1.0 × 10 ⁴ to The film for chip protection according to claim 1, wherein the film is 5.0 × 10 ⁶ Pa.

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