JP2008218930A - Energy ray hardening type chip protecting film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an energy ray hardening type chip protecting film which provides laser mark recognition function, high hardness, and mounting reliability even when cured with an energy ray in a system containing dye and pigment. <P>SOLUTION: A release sheet 1 is overlaid with an energy ray hardening type protective film forming layer 2 containing (A) polymer component consisting of acrylic copolymer which has polymerizable double bond and weight-average molecular weight of 50,000 or more, (B) an energy ray hardening component, (C) dye and/or pigment, and (D) silica. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a film for chip protection 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 in particular, is mounted by a so-called face-down method. The present invention relates to a film for protecting a chip used for manufacturing a semiconductor chip.

  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.
(A) 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.
(B) The back surface of the semiconductor wafer is ground to a predetermined thickness.
(C) The back surface of the semiconductor wafer is fixed to a dicing sheet stretched on a ring frame, and a semiconductor chip is obtained by cutting and separating each circuit with a dicing saw.
(D) A semiconductor chip is picked up and mounted on a predetermined base by a face-down method, 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. Furthermore, since it is difficult for the above resin coating to uniformly apply an appropriate amount of resin, quality may vary.
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 grinding in the step (b), minute streak is formed on the back surface of the chip by mechanical grinding. This minute scratch may cause cracks after the (c) dicing step or packaging. For this reason, conventionally, chemical etching for removing minute scratches may be necessary after mechanical grinding. However, chemical etching necessitates equipment and operation costs as well as the cost increase.
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 process that can easily form a protective film with high uniformity on the back surface of the chip, and even if minute scratches are formed on the back surface of the chip by mechanical grinding, Moreover, the film for chip protection used for this process is proposed (patent documents 1-3).
JP 2004-214288 A JP 2004-260190 A JP 2004-331728 A

Conventionally, when a protective film having a high hardness is formed on the back surface of a chip, thermosetting using a thermosetting component is generally used. Therefore, a heat treatment process at 100 to 200 ° C. for about 1 to 3 hours. Was necessary. In order to simplify this heat treatment step, by using an energy ray curable chip protecting film, it can be instantaneously cured in about 10 to 300 seconds by, for example, ultraviolet rays.
Patent Document 2 also exemplifies an energy ray (ultraviolet ray) curable chip protection film instead of a thermosetting type. In this case, when dyes and pigments are added for the purpose of improving laser mark recognition, improving appearance, etc. The transmittance of the film was low, and it was difficult to sufficiently cure the entire film as compared with the thermosetting type.

For this reason, the energy ray (ultraviolet ray) curable chip protection film has problems such as failure to obtain sufficient performance to satisfy all aspects of laser mark recognition, mounting reliability, and hardness. It was.
In view of such conventional circumstances, the present invention provides an energy ray curable chip protection film capable of realizing laser mark recognizability, high hardness, and mounting reliability even when cured with an energy ray in a system containing a dye and a pigment. The issue is to provide.

  As a result of intensive studies on the above problems, the inventors of the present invention have found that a specific polymer component, an energy ray curable component, a dye and / or pigment, and an energy ray curable protection comprising silica as essential components. As a configuration having a film forming layer, it was found that an energy ray curable chip protection film capable of realizing laser mark recognizability, high hardness and mounting reliability even after being cured by energy rays was obtained, and the present invention was completed. did.

That is, this invention provides the energy ray hardening-type chip | tip protective film of following (1)-(6).
(1) (A) a polymer component comprising an acrylic copolymer having a polymerizable double bond and a weight average molecular weight of 50,000 or more, (B) an energy ray curable component, (C) a dye and / or pigment, and (D ) An energy ray curable chip protecting film comprising an energy ray curable protective film forming layer containing silica.
(2) The energy ray-curable chip protecting film according to (1), wherein the energy ray-curable component (B) is an epoxy-modified acrylate.
(3) The energy ray curable protective film forming layer is 1 to 50 parts by mass of (C) a dye and / or a pigment with respect to 100 parts by mass of the total of (A) the polymer component and (B) the energy ray curable component. (D) The energy ray-curable chip protecting film according to (1) or (2), comprising 100 to 700 parts by mass of silica.
(4) The energy ray curable protective film-forming layer contains (E) a photopolymerization initiator in addition to the components (A) to (D), and any one of (1) to (3) The energy ray-curable chip protecting film as described in 1.
(5) The film for protecting an energy ray-curable chip according to (4), wherein the photopolymerization initiator (E) is an acylphosphine oxide.
(6) The energy ray curable chip protecting film according to any one of (1) to (5), wherein the release sheet is temporarily attached to one or both sides of the energy ray curable protective film forming layer.

  According to the energy ray curable chip protecting film of the present invention, a protective film excellent in laser mark recognizability, hardness, and mounting reliability can be formed on the chip by energy rays, so that the conventional heating process can be simplified. it can.

Next, the energy ray curable chip protecting film as a preferred embodiment of the present invention will be described in more detail with reference to the drawings.
1 and 2 are two examples of the energy ray curable protective film-forming layer of the present invention having an energy ray curable protective film-forming layer on a release sheet, and FIG. 1 is an energy ray curable protective film-forming layer. FIG. 2 shows a configuration in which the release sheet is temporarily attached to one side of the energy ray curable protective film forming layer.
Below, it demonstrates in order regarding the structure of this peeling sheet and an energy-beam curable protective film formation layer. Moreover, the manufacturing method and usage method of such an energy ray hardening-type chip | tip protective film are also demonstrated below.

<Peeling sheet>
The release sheet is used for the purpose of protecting the energy ray curable protective film forming layer.
The surface tension of the release sheet is preferably 40 mN / m or less, and particularly 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.

  Examples of release sheet materials include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyphenyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene terephthalate film. , 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 A fluororesin film or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

<Energy ray curable protective film forming layer>
The energy ray curable protective film forming layer is the most characteristic layer of the present invention, and (A) a polymer component composed of an acrylic copolymer having a polymerizable double bond and a weight average molecular weight of 50,000 or more, (B It contains an energy ray curable component, (C) a dye and / or pigment, and (D) silica. In addition to the above components (A) to (D), this layer preferably contains (E) a photopolymerization initiator. Further, if necessary, (F) other components may be included. These components will be sequentially described below.

(A) Polymer component In the present invention, in order to improve the flexibility and operability as a film, a polymer component is used, and an acrylic copolymer having a polymerizable double bond is used as this polymer component. To do. By using such an acrylic copolymer, the hardness and heat resistance after energy beam curing can be improved.
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.

(B) Energy beam curable component The energy beam curable component is composed of a compound that polymerizes and cures when irradiated with energy rays such as ultraviolet rays and electron beams. Such a compound has at least one polymerizable double bond in the molecule and usually has a weight average molecular weight in the range of 100 to 30,000, particularly preferably in the range of 300 to 10,000. It is done.

Examples of such energy ray-curable components include trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, or 1,4-butylene glycol. Examples include diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, oligoester acrylate, polyester-type or polyether-type urethane acrylate oligomer, polyester acrylate, polyether acrylate, and epoxy-modified acrylate.
Among these, ultraviolet curable resins are particularly preferable. Specifically, epoxy-modified acrylates, oligoester acrylates, urethane acrylate oligomers and the like are preferable, and epoxy-modified acrylates are most preferable in terms of hardness, heat resistance, adhesiveness, and the like.

(C) Dye and Pigment The pigment and the dye are added mainly for improving the recognizability of the laser marking formed on the cured film (protective film). 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.
These addition amounts vary depending on the type, but generally, (C) the dye and / or pigment is 1 to 1 parts per 100 parts by mass of the total of (A) the polymer component and (B) the energy ray curable component. 50 parts by weight, preferably 3 to 25 parts by weight are suitable.

(D) Silica Silica has a function of bringing the thermal expansion coefficient of the cured layer closer to the thermal expansion coefficient of the wafer, thereby reducing the warpage of the wafer during processing.
Such silica is not particularly limited, but spherical synthetic silica having an average particle diameter of 0.1 to 10 μm is preferable, and in particular, the α-ray source that causes malfunction of the semiconductor device is removed as much as possible. The type of synthetic silica is optimal.
In general, the addition amount of silica is preferably 100 to 700 parts by mass, more preferably 200 to 600, with respect to (D) silica, with respect to 100 parts by mass in total of (A) the polymer component and (B) the energy ray curable component. Part by mass is appropriate. Thus, hardness and heat resistance can be improved by adding 50 mass% or more of the total amount of silica.

(E) Photopolymerization initiator The energy ray curable protective film-forming layer can reduce the polymerization and curing time and the amount of light irradiation by mixing a photopolymerization initiator therein.
The usage-amount of the photoinitiator used for such a purpose is 1.5-4.5 mass parts normally with respect to 100 mass parts of (B) energy-beam curable components, Most preferably, it is 2.4- The ratio is preferably about 3.8 parts by mass.

Such photopolymerization initiators include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethyl Examples include thioxanthone, α-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethyl thiuram 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 and can be cured even in a system to which a dye and a pigment are added is particularly preferable.

(F) Other components In addition to the above components, the energy ray curable protective film forming layer, if necessary, butadiene rubber or silicone rubber as a crosslinking agent, coupling agent, antioxidant, flame retardant, or stress relaxation agent Etc. can be contained. 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.

<Manufacturing method>
The energy ray curable chip protecting film of the present invention is a roll knife coater, a gravure coater, a die coater, and a composition containing each component that constitutes the energy ray curable protective film forming layer on the release surface of the release sheet. According to a generally known method such as a reverse coater, it can be applied directly or by transfer and dried. The above composition may be applied after being dissolved or dispersed in a solvent, if necessary.
The thickness of the energy ray curable protective film forming layer is preferably 3 to 300 μm, more preferably 10 to 60 μm. If this layer is too thin, it is difficult to obtain a protective and reinforcing effect, and problems such as uneven color are likely to occur. Moreover, when this layer is too thick, it will become difficult to harden the whole film only by energy ray irradiation.

<How to use>
The use application of the energy ray curable chip protection film of the present invention is not particularly limited as long as it is a chip protection application. For example, it can be used for a chip back surface protection application for a wafer level package.
In this case, first, the chip protection film is heated to 40 ° C. or higher on the back surface of the wafer and laminated by applying a pressure of 0.05 to 0.5 MPa, and the film is cut into a wafer size. The film laminated on the wafer is irradiated with ultraviolet rays of 100 to 2000 mJ / cm ² to cure the film and protect the entire surface of the wafer. The obtained wafer with a film can be separated into pieces by dicing and used as a chip protected with a protective film.

The pencil hardness of the film after being cured with energy rays is preferably H or more and the peak value of probe tack at 230 ° C. is 150 mN / mm ² or less.
When the pencil hardness of the film is less than H, the protective film is likely to be damaged during wafer conveyance, chip adsorption, pressure bonding, and the like.
When the peak value of the probe tack at 230 ° C. of the above film exceeds 150 mN / mm ² , the film is peeled off in a reflow process heated to 200 ° C. or more, the film leaks along with the softening of the film surface, other members, etc. Problems such as transfer to the ink occur.

  The peak value of the probe tack is generally a cylinder (probe with a diameter of 3 to 5 mm) made of metal or the like, pressed against the adhesive surface with a constant pressure, time, temperature, etc., and peeled off at a constant speed. In the present invention, a cylindrical probe having a diameter of 3 mm is used, the contact speed is 30 mm / min, the contact load is 100 gf, the contact time is 3 seconds, the peeling speed is 600 mm / min, It shall mean the value measured under heating at 230 ° C.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

Examples 1-6 and Comparative Examples 1-4
A coating solution for a curable protective film-forming layer was prepared by blending each component shown in Table 1 (Examples 1 to 6) and Table 2 (Comparative Examples 1 to 4).
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.

A1: Polymer component 1 (Acrylic copolymer having a weight average molecular weight of 800,000 and a glass transition temperature of −33 ° C., no polymerizable double bond)
A2: Polymer component 2 (acrylic copolymer having a weight average molecular weight of 800,000 and a glass transition temperature of −65 ° C., with a polymerizable double bond)
B1: Energy ray curable component 1 (trimethylol propantotriacrylate)
B2: Energy ray curable component 2 (epoxy acrylate resin)
C: Dye and pigment [Black pigment (azo)]
D: Silica [spherical synthetic silica (average particle size 3 μm)]
E1: Photopolymerization initiator 1 (α-hydroxycyclohexyl phenyl ketone)
E2: Photopolymerization initiator 2 (acylphosphine oxide)
F: Crosslinking agent (organic polyvalent isocyanate crosslinking agent)

Next, after coating and drying each of the above coating solutions on a release sheet made of a polyethylene terephthalate (PET) film having a thickness of 38 μm at 130 ° C./3 minutes so that the dry film thickness becomes 30 μm, Another release sheet similar to the above was laminated thereon to produce a three-layer energy ray curable chip protecting film comprising release sheet / energy ray curable protective film forming layer / release sheet.
With respect to this energy ray curable chip protecting film, the pencil hardness and tack force (probe tack peak value) of the energy ray curable protective film forming layer are measured by the following method, and the laser mark is measured by the following method. The results of examining the recognition and mounting reliability were as shown in Table 3.

<Pencil hardness>
The energy ray curable 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.

<Peak tack peak value>
The peak value (tack force) of the probe tack after the ultraviolet irradiation (1,000 mJ / cm ² ) of the energy ray curable protective film forming layer on the adherend side is measured by a tacking tester manufactured by Resuka Co., Ltd., TAC- Measurement was performed using a mold. The measurement conditions are as follows. The result was an average value of n = 5.
Probe: 3 mmφ cylindrical probe Contact speed of probe: 30 mm / min Contact load: 100 gf
Contact time: 3 seconds Peeling speed: 600 mm / min Measurement temperature: 230 ° C.

<Laser mark recognition>
The energy ray curable 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, laser marking was performed (manufactured by Keyence: using ML-G9320, character height 0.75 mm, character width 0.5 mm), and 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 less than 30% is ×

<Mounting reliability>
The energy ray curable 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). A dicing tape was bonded to the protective film layer side and diced to 5 mm × 5 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.

Examples 1 to 6 of the present invention include pigments and silica in the energy ray-curable protective film forming layer, satisfy the requirements of the present invention with their pencil hardness and tack force, and have laser mark recognition and mounting reliability. There was no problem with either.
On the other hand, Comparative Example 1 is sufficiently cured and has no problem with pencil hardness and tack force, but does not contain a pigment, so that the laser mark recognizability is insufficient. Since Comparative Example 2 contains a pigment, the curing is insufficient, the tack force after ultraviolet curing is high, and there is no heat resistance, so there is a problem in terms of mounting reliability. Also in Comparative Example 3, since the curing is insufficient, the pencil hardness is low, and the wafer is easily damaged when transporting the wafer, and there is a problem in terms of mounting reliability.

It is sectional drawing which shows an example of the energy ray hardening-type chip | tip protective film of this invention. It is sectional drawing which shows the other example of the energy ray hardening-type chip | tip protective film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Release sheet 2 Energy-beam curable protective film formation layer

Claims (6)

  (A) a polymer component comprising an acrylic copolymer having a polymerizable double bond and a weight average molecular weight of 50,000 or more, (B) an energy ray-curable component, (C) a dye and / or pigment, and (D) silica. An energy beam-curable chip protecting film comprising an energy beam-curable protective film-forming layer.   The energy ray-curable chip protecting film according to claim 1, wherein the energy ray-curable component (B) is an epoxy-modified acrylate.   The energy ray-curable protective film-forming layer is composed of 1 to 50 parts by mass of (C) a dye and / or pigment with respect to 100 parts by mass of the total of (A) the polymer component and (B) the energy ray-curable component, (D) The energy ray-curable chip protecting film according to claim 1, comprising 100 to 700 parts by mass of silica.   The energy ray-curable protective film forming layer contains (E) a photopolymerization initiator in addition to the components (A) to (D). Curing type chip protection film.   (E) The photopolymerization initiator is acylphosphine oxide, The energy ray-curable chip protecting film according to claim 4. 6. The energy ray curable chip protecting film according to claim 1, wherein the release sheet is temporarily attached to one side or both sides of the energy ray curable protective film forming layer.

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