JP2009141024A - Adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tape for functioning as a mask material utilizable for an automatic machine for handling the tape in the plasma dicing of a semiconductor wafer. <P>SOLUTION: The adhesive tape with an adhesive agent layer formed on a base film has a heat resistance at temperatures when a plasma dicing process for semiconductor wafer processing is conducted, and is the mask in the plasma dicing processing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an adhesive tape used in a dicing process of semiconductor wafer processing.

  As chip packaging technology advances due to higher density of semiconductor packages, wafer thinning is progressing at an accelerated rate year by year. Conventionally, these semiconductor chips are obtained by grinding the back side without a circuit pattern until a predetermined thickness is obtained in a back grinding process in a state where the surface protection tape is bonded to the circuit pattern surface of the semiconductor wafer. And then cut and separated by a dicing apparatus or the like in a dicing process in a state where it is supported and fixed to a dicing tape. After that, the chip-formed semiconductor chip is die-bonded to a continuously flowing lead frame by a pick-up die bonder or the like, and is finally molded and molded with a mold resin. However, in the processing (dicing) of wafers that have become thinner, such as a thickness of 50 μm or less, blade dicing, which is an existing technology, is becoming a region that cannot be handled due to device destruction due to increased chipping.

  Against this background, various dicing techniques have been devised, such as laser dicing, stealth dicing, and DBG processes. One method of dicing devised along with such thinning is plasma dicing (see Patent Document 1). Plasma dicing has been developed by applying the plasma technology conventionally used for metallizing and the plasma etching process used for stress relief processing for removing the fractured layer after grinding of the wafer back surface. In this new process, it is necessary to first open a portion corresponding to the scribe line before the plasma dicing process, and after the opening is formed, the plasma processing is performed. However, the portion other than the scribe must be protected from the plasma atmosphere.

Conventionally, a resist is used as a mask in plasma processing. In this case, equipment that is used in the photolithography process, such as a resist coating apparatus and an exposure apparatus, is necessary, and the customer actually used is a lower process in the semiconductor process. It is likely to be an obstacle to introduction.
JP 2007-019385 A

  An object of the present invention is to provide a tape that functions as a mask material that can use an automatic machine for handling a tape during plasma dicing of a semiconductor wafer.

The above object of the present invention is achieved by the following means.
That is, the present invention
(1) An adhesive tape having an adhesive layer formed on a base film, having heat resistance at a temperature at which a plasma dicing process of semiconductor wafer processing is performed, and serving as a mask in the plasma dicing process Adhesive tape,
(2) The pressure-sensitive adhesive tape according to (1), wherein the pressure-sensitive adhesive layer comprises a radiation curable pressure-sensitive adhesive.
(3) The pressure-sensitive adhesive tape according to (1), wherein the substrate film has a thickness of 5 to 200 μm,
(4) The adhesive tape according to (1), wherein the base film is made of a heat resistant resin selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyimide, and polyetherimide,
(5) The pressure-sensitive adhesive tape according to (1), wherein the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is provided is subjected to corona treatment or easy adhesion treatment of primer coating treatment. ,and,
(6) A pressure-sensitive adhesive tape having an adhesive force of 5 to 15 N / 25 mm, which is used in a pickup step of a process in which the adhesive tape described in (1) is used, is provided.

The pressure-sensitive adhesive tape of the present invention has high heat resistance and can be applied as a mask material for plasma dicing. Further, by combining with the pickup tape of the present invention, it has become possible to handle thin film wafers from the plasma dicing process to the pickup.
The pressure-sensitive adhesive tape of the present invention can be used in a plasma dicing process by using an automatic machine that handles the tape, such as a tape bonding apparatus and a peeling apparatus used in normal wafer processing.

Hereinafter, preferred embodiments of the pressure-sensitive adhesive tape according to the present invention will be described.
As shown in FIG. 1, the pressure-sensitive adhesive tape 1 of the present invention is a pressure-sensitive adhesive tape 3 in which a pressure-sensitive adhesive layer 3 is formed on the surface of a base film 2. The adhesive tape 1 is used as a surface protection tape in semiconductor wafer processing, withstands the high temperature of the plasma dicing process, and has a plasma dicing mask function.

The thickness of the base film is preferably 5 to 200 μm, and more preferably 10 to 50 μm.
If this thickness is too thick, there may be a case where sufficient cutting properties cannot be obtained in laser cutting or blade cutting during the patterning before plasma dicing.

  It is preferable that the base film is made of a heat resistant resin selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyimide, and polyetherimide. By using such a heat-resistant resin, it is possible to prevent anyone from occurring during dicing.

  There is no particular limitation on the radiation-curable pressure-sensitive adhesive layer applied to the above-mentioned back surface protective tape or surface protective tape, and generally, the main component is a normal acrylic pressure-sensitive adhesive and a radiation polymerizable compound. It will become. Also, the pressure-sensitive adhesive layer is not particularly limited, and a normal acrylic pressure-sensitive adhesive or the like can be applied. In the case of a radiation curable type, the acrylic pressure-sensitive adhesive and the radiation polymerizable compound are the same as described above. And a composition having as a main component. Specific examples of these acrylic pressure-sensitive adhesives and radiation-polymerizable compounds are as follows.

  The acrylic pressure-sensitive adhesive contains a (meth) acrylic copolymer and a curing agent as components. The (meth) acrylic copolymer is, for example, a polymer having a (meth) acrylic acid ester as a polymer constituent unit, and a (meth) acrylic polymer of a (meth) acrylic acid ester copolymer, or functionality. Examples include copolymers with monomers, and mixtures of these polymers. As the molecular weight of these polymers, those having a weight average molecular weight of about 500,000 to 1,000,000 are generally applied. Moreover, a hardening | curing agent is used in order to make it react with the functional group which a (meth) acrylic-type copolymer has, and to adjust adhesive force and cohesion force. For example, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1,3-bis (N, N-diglycidylaminomethyl) toluene, 1,3-bis (N, N-diglycidylaminomethyl) ) Epoxy compounds having two or more epoxy groups in the molecule such as benzene, N, N, N, N'-tetraglycidyl-m-xylenediamine, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate , 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4′-diisocyanate and the like, an isocyanate compound having two or more isocyanate groups in the molecule, tetramethylol-tri-β-aziridini Lupropionate, trimethylol-tri-β-aziridinylpropionate, Examples include aziridin compounds having two or more aziridinyl groups in the molecule, such as limethylolpropane-tri-β-aziridinylpropionate and trimethylolpropane-tri-β- (2-methylaziridine) propionate. . What is necessary is just to adjust the addition amount of a hardening | curing agent according to the adhesive force of a bookstore, and 0.1-5.0 mass parts is suitable with respect to 100 mass parts of (meth) acrylic-type copolymers.

  The radiation curable pressure-sensitive adhesive generally comprises the above acrylic pressure-sensitive adhesive and a radiation polymerizable compound as main components. As the radiation-polymerizable compound, for example, a low molecular weight compound having at least two photopolymerizable carbon-carbon double bonds in a molecule that can be three-dimensionally reticulated by irradiation with ultraviolet rays is widely used. Specifically, trimethylol is used. Propane triacrylate, tetramethylol methane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6 hexanediol diacrylate Polyethylene glycol diacrylate, oligoester acrylate, and the like are widely applicable.

  In addition to the above acrylate compounds, urethane acrylate oligomers can also be used. The urethane acrylate oligomer includes a polyol compound such as a polyester type or a polyether type, and a polyvalent isocyanate compound (for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diene). A terminal isocyanate urethane prepolymer obtained by reacting isocyanate, 1,4-xylylene diisocyanate, diphenylmethane 4,4-diisocyanate, etc.) with an acrylate or methacrylate having a hydroxyl group (for example, 2-hydroxyethyl) Acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, etc.) It is obtained by reacting.

  As a compounding ratio of the acrylic pressure-sensitive adhesive and the radiation-polymerizable compound in the radiation-curable pressure-sensitive adhesive, the radiation-polymerizable compound is 50 to 200 parts by weight, preferably 50 to 150 parts by weight with respect to 100 parts by weight of the acrylic pressure-sensitive adhesive. It is desirable to blend in the range of parts. In the case of this blending ratio range, the adhesive strength of the pressure-sensitive adhesive layer is greatly reduced after radiation irradiation.

  Furthermore, the radiation-curable pressure-sensitive adhesive can be made into a radiation-polymerizable acrylic ester copolymer instead of blending the radiation-polymerizable compound with the acrylic pressure-sensitive adhesive as described above. is there.

  When the pressure-sensitive adhesive layer is polymerized by radiation, a photopolymerization initiator such as isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, benzyl methyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxy Methylphenylpropane or the like can be used in combination. By adding at least one of these to the pressure-sensitive adhesive layer, the polymerization reaction can proceed efficiently.

  The pressure-sensitive adhesive tape of the present invention has a heat resistance at which a film is not sunk by dicing at a temperature (normally 80 ° C. or higher) at which a plasma dicing process for semiconductor wafer processing is performed. As for Tg of an adhesive tape, 50-200 degreeC is preferable. The pressure-sensitive adhesive tape of the present invention is used as a mask material instead of a conventional resist mask in plasma dicing.

  The transmittance of the ultraviolet wavelength region (200 to 400 nm) of the pressure-sensitive adhesive tape (mask tape) of the present invention is preferably 70% or more.

  Another embodiment of the present invention is a pressure-sensitive adhesive tape used in a pick-up step in a process in which the above-mentioned adhesive tape (mask tape) is used.

The above pressure-sensitive adhesive tape (hereinafter also referred to as a pickup tape), for example, transfers an adhesive layer obtained by applying and drying a solution containing the base resin on a release film onto a base film. Can be manufactured.
The pressure-sensitive pressure-sensitive adhesive tape is preferably a pressure-sensitive tape for semiconductor processing in which a pressure-sensitive adhesive layer is provided on at least one surface of a base film, and the weight average molecular weight of the base resin constituting the pressure-sensitive adhesive layer is 10 The molecular weight distribution of 10,000 or less is preferably 20% by mass or less, more preferably 10% by mass or less in the base resin.
In the present invention, the dispersion index of the base resin is preferably 6.0 or less, and the glass transition temperature thereof is preferably −55 ° C. or more, the dispersion index of the base resin is 5.0 or less, and The glass transition temperature is more preferably −50 to 0 ° C.
In the present invention, the base resin preferably has a weight average molecular weight (Mw) of 800,000 or more, and more preferably has a Mw of 1,000,000 to 1,800,000.

The weight average molecular weight and dispersion index can be measured by GPC (gel permeation chromatograph) under the following measurement conditions.
Further, the ratio (%) of the molecular weight distribution of 100,000 or less to the whole base resin molecular weight distribution can be measured in the same manner under the following measurement conditions.
GPC device: HLC-8120GPC manufactured by Tosoh Corporation, column: TSKgel SuperHM-H / H4000 / H3000 / H2000, flow rate: 0.6 ml / min, concentration: 0.3 mass%, injection amount: 20 μl, column temperature: 40 ° C. Eluent: tetrahydrofuran.

In the present invention, the base resin is preferably an acrylic pressure-sensitive adhesive composed of a (meth) acrylic copolymer and a curing agent.
The (meth) acrylic copolymer is obtained by copolymerization of a monomer (1) such as an alkyl acrylate ester and a monomer (2) having a functional group capable of reacting with a curing agent described later.

  Examples of the monomer (1) include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate. These may be used singly or in combination of two or more.

  Examples of the monomer (2) include acrylic acid, methacrylic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, maleic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, and methacrylamide. Is mentioned. These may be used singly or in combination of two or more.

  The (meth) acrylic copolymer can be obtained by copolymerizing the monomers (1) and (2) by a solution polymerization method according to a conventional method. From the viewpoint of not generating a component having a molecular weight of 100,000 or less, a copolymer polymerized by a suspension polymerization method is preferable.

  A hardening | curing agent is used in order to make it react with the functional group which a (meth) acrylic-type copolymer has, and to adjust adhesive force and cohesion force. For example, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1,3-bis (N, N-diglycidylaminomethyl) toluene, 1,3-bis (N, N-diglycidylaminomethyl) ) Epoxy compounds having two or more epoxy groups in the molecule such as benzene, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 2,4-tolylene diisocyanate, 2,6-triene Diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4′-diisocyanate and other isocyanate compounds having two or more isocyanate groups in the molecule, tetramethylol-tri-β- Aziridinyl propionate, trimethylol-tri-β-aziridinyl propionate , Aziridine compounds having two or more aziridinyl groups in the molecule such as trimethylolpropane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β- (2-methylaziridine) propionate, etc. It is done.

What is necessary is just to adjust content of a hardening | curing agent according to desired adhesive force, and 5.0-15.0 mass parts is preferable with respect to 100 mass parts of (meth) acrylic-type copolymers, and it is detected on the wafer surface. It is more preferably 6.0 to 12.0 parts by mass from the viewpoint of recognizing the effect of remarkably reducing the organic matter adhesion amount.
When there is too little content of a hardening | curing agent, the reduction effect of the organic substance adhesion amount detected on the wafer surface is not recognized.

  In addition, the pressure-sensitive adhesive tape may be improved in adhesive force by introducing a tackifier (tackifier) into a commonly used base resin. The tackifier used is not particularly limited, and any tackifier can be used.

  In the present invention, the pressure-sensitive adhesive tape adhesive strength is a value measured in accordance with JIS Z 0237 (1991) (180 ° peeling method, peeling speed 300 mm / min, test plate: silicon wafer), and 5 to 30 N. / 25 mm is preferable, and 10 to 15 N / 25 mm is preferable.

Examples of the solvent used for the acrylic adhesive coating solution include ethyl acetate, toluene, xylene, acetone, methyl ethyl ketone, n-hexane, and cyclohexane.
In the present invention, the thickness of the pressure-sensitive adhesive layer is preferably 10 to 100 μm.

The material of the base film is a homopolymer of α-olefin such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ionomer, or the like. Examples thereof include engineering plastics such as copolymers, polyethylene terephthalate, polycarbonate, and polymethyl methacrylate, and thermoplastic elastomers such as polyurethane, styrene-ethylene-butene, and pentene copolymers. Or 2 or more types chosen from these groups may be mixed, and it can select arbitrarily by adhesiveness with an adhesive layer.
As for the thickness of a base film, 30-300 micrometers is preferable.

An example of a semiconductor wafer processing step by plasma dicing using the adhesive tape of the present invention will be described.
First, a surface protective tape is bonded to the surface of the semiconductor wafer on the side of the Si substrate where the wiring pattern and the TEG are formed, and then a groove is formed in the street where the TEG is formed by a laser or a blade. Next, a peeling tape is bonded to the surface of the singulated surface protective tape, and the peeling tape is peeled off so that the surface protective tape is combined and peeled off.
Next, as shown in FIG. 2, the BG tape 17 is bonded to the wiring pattern 12 side, and the wafer is thinned by grinding (back grinding) from the back side of the Si substrate 11 using the grindstone 18. At this time, a pulverized layer (damaged layer) 19 is generated on the ground surface (FIG. 2A). Next, in order to perform stress relief, plasma processing is performed by wet etching or dry polishing, a CMP method, or further under a sulfur hexafluoride atmosphere, and the damage layer 19 is removed, and the BG residual stress is removed.

  Next, the pressure-sensitive adhesive tape 1 of the present invention is bonded to the back surface of the Si substrate 11 via a die-bonding adhesive film (hereinafter referred to as DAF) 20. The DAF 20 is not always necessary, and may be omitted depending on the design of the semiconductor processing process, and the adhesive film 1 may be directly bonded to the Si substrate 11. (FIG. 2B) Next, the adhesive film 1 and DAF 11 in the street portion are cut with a laser 15 (FIG. 2C). In addition, in FIG.2 (c), although cut with the laser 15, you may cut using a braid | blade instead of a laser.

  Next, as shown in FIG. 2D, plasma dicing is performed from the pressure-sensitive adhesive tape 1 side in a sulfur hexafluoride atmosphere, and the exposed Si substrate 11 is etched. At this time, the portion covered with the adhesive tape 1 is not etched with the adhesive tape 1 functioning as a mask material (FIG. 2E).

  Next, the pickup tape 21 is bonded to the surface of the adhesive tape 1 (FIG. 2 (f)). Next, as shown in FIG. 2G, the BG tape 17 on the pattern surface 12 side is peeled off. Next, ultraviolet light is irradiated from the pickup tape 21 side through the glass to weaken the adhesive force at the interface between the adhesive tape 1 and the DAF 20. At this time, since the pressure-sensitive adhesive of the pickup tape 21 is a non-radiation-curable pressure-sensitive adhesive, the adhesive force at the interface between the pressure-sensitive adhesive tape 1 and the pickup tape 21 is not reduced. Furthermore, it is preferable that the back surface of the pressure-sensitive adhesive tape 1 is subjected to corrugation treatment such as corona treatment or primer coating because the adhesive force at the interface between the pressure-sensitive adhesive tape 1 and the pickup tape 21 is increased. Next, as shown in FIG. 2 (k), when the chip is pushed up and adsorbed by the collet 22, the chip is easily separated from the interface between the adhesive tape 1 and the DAF 12, and the chip to which the DAF 12 is attached is picked up and transferred to the die bonding process.

  FIG. 3 is an explanatory view showing another example of a semiconductor wafer processing step by plasma dicing using the adhesive tape of the present invention. The plasma stress relief process is the same process as described above. Thereafter, in this embodiment, after the BG tape is peeled off from the wiring pattern 12 side of the Si substrate 11, the adhesive tape 1 of the present invention is bonded, and the back surface is bonded with the DC tape 23 via the DAF 19 (FIG. 3 ( a)). Next, the adhesive film 1 and the wiring pattern 12 in the street portion where the TEG 13 is formed are cut with a laser or a blade 15 (FIG. 3B). Next, plasma dicing is performed from the adhesive film 1 side, and the exposed Si substrate 11 is etched. At this time, the portion covered with the adhesive tape 1 is not etched because the adhesive tape 1 functions as a mask material (FIG. 3C). Further, the DAF 20 is etched as shown in FIG. 3D to obtain the state shown in FIG. Next, the peeling tape 24 is bonded to the surface of the pressure-sensitive adhesive tape 1 (FIG. 3 (f)), and the separated pressure-sensitive adhesive tape 1 is peeled off by peeling this (FIG. 3 (g)). Next, the separated chips are picked up and transferred to a die bonding step (FIG. 3 (h)). In FIG. 3, the symbols other than those specifically described have the same meaning as shown in FIG.

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

Example 1
Example 1 A layer made of the following UV-based adhesive A was formed on one surface of a PET film having a thickness of 12.5 μm so that the thickness upon drying was 8 μm, and the other surface was corona-treated. An adhesive tape was prepared.

Example 2
After the surface of a PET film having a thickness of 25 μm was corona-treated, the following UV-based adhesive A was formed on the surface so as to have a thickness of 15 μm when dried, and an adhesive tape of Example 2 was produced.

Example 3
After corona-treating the surface of a PET film having a thickness of 12.5 μm, the following UV-based adhesive B was formed on the surface so that the thickness when dried was 8 μm, and an adhesive tape of Example 1 was produced. .

Example 4
After corona-treating the surface of a PET film having a thickness of 25 μm, the following UV-based adhesive B was formed on the surface so that the thickness when dried was 15 μm, and an adhesive tape of Example 2 was produced.

  The composition of the A adhesive and the adhesive B used is as follows.

The composition of the used ultraviolet curable adhesive A, ultraviolet curable adhesive B, and acrylic adhesive a is as follows.
(Adhesive A)
Acrylate ester copolymer 100 parts by weight Curing agent ("Coronate L" (trade name, manufactured by Nippon Polyurethane Co., Ltd.) 2 parts by weight Urethane acrylate oligomer 150 parts by weight Photopolymerization initiator ("Irgacure 184" (trade name) ), Made by Nippon Ciba-Geigy
2 parts by mass (adhesive B)
Acrylic ester copolymer 100 parts by weight Curing agent ("Coronate L" (trade name, manufactured by Nippon Polyurethane Co., Ltd.) 2 parts by weight Urethane acrylate oligomer 100 parts by weight Photopolymerization initiator ("Irgacure 184" (trade name) ), Made by Nippon Ciba-Geigy
2 parts by mass

Test Example Plasma of the process shown in FIG. 2 using the adhesive tape of Examples 1 to 4 as the surface protection tape and the mask material, and the non-UV type pressure sensitive adhesive tape of 12 N / 25 mm as the pickup tape. Semiconductor wafer processing by dicing process was performed.
As a result, the pressure-sensitive adhesive tape of the present invention was improved in laser cutability by reducing the film thickness, reduced in outgassing by reducing the additive (such as oligomer) in the pressure-sensitive adhesive composition, and had no problem even when used in vacuum. In addition, thin film grinding, plasma dicing, and pick-up could be performed without problems.

It is sectional drawing of one example of the adhesive tape of this invention. It is explanatory drawing of an example of the processing process of the semiconductor wafer by the plasma dicing using the adhesive tape of this invention. It is explanatory drawing of another example of the processing process of the semiconductor wafer by the plasma dicing using the adhesive tape of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adhesive tape 2 Base film 3 Adhesive layer 11 Si substrate 12 Wiring pattern 13 TEG
15 Laser or blade 17 BG tape 18 Whetstone 19 Damaged layer 20 DAF
21 Pickup tape 22 Collet 23 DC tape 24 Stripping tape

Claims (6)

  An adhesive tape having an adhesive layer formed on a base film, having heat resistance at a temperature at which a plasma dicing process of semiconductor wafer processing is performed, and serving as a mask in the plasma dicing process tape.   The pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive layer is made of a radiation curable pressure-sensitive adhesive.   The pressure-sensitive adhesive tape according to claim 1, wherein the base film has a thickness of 5 to 200 μm.   The pressure-sensitive adhesive tape according to claim 1, wherein the base film is made of a heat resistant resin selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyimide, and polyetherimide.   The pressure-sensitive adhesive tape according to claim 1, wherein the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is provided is subjected to corona treatment or primer coating treatment for easy adhesion.   A pressure-sensitive adhesive tape having an adhesive force of 5 to 15 N / 25 mm used in a pick-up step of a process in which the adhesive tape according to claim 1 is used.

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