JP2009242776A - Adhesive tape for surface protection for semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive tape for the surface protection for a semiconductor wafer, which is excellently peeled even in thickness, diameter and surface film state (polyimide, benzocyclobutene etc.) of wafer conventionally having difficulty in peeling in a process in which an adhesive tape for the surface protection for a semiconductor wafer is pasted to a semiconductor wafer, the back of the semiconductor wafer is ground and the tape is peeled. <P>SOLUTION: The adhesive tape for the surface protection for a semiconductor wafer has an adhesive layer on a substrate film in which the contact angle of methylene iodide on the surface of the adhesive layer at 23°C is ≥40 degrees and ≤70 degrees and the adhesive force of the adhesive tape to SUS280 polished surface is ≤1 N/25 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesive tape for protecting a semiconductor wafer surface.

The process of processing a semiconductor wafer includes a step of attaching a semiconductor wafer surface protection adhesive tape to the pattern surface of the semiconductor wafer, a step of grinding the back surface of the semiconductor wafer, a step of mounting the wafer on a dicing tape, and a surface protection adhesive from the semiconductor wafer. After the process of peeling the tape, the process of dividing the wafer by dicing, the die bonding process of joining the divided semiconductor chip to the lead frame, and the molding process of sealing the semiconductor chip with resin for external protection Has been.
As the conventional surface protection tape for semiconductor wafer processing, the adhesive tape with the adhesive layer coated on one surface of the base film is the mainstream, but with the progress of high-density mounting technology in recent years, wafer thinning technology is progressing. As the wafer becomes thinner, there is an increasing demand for the thickness accuracy of the adhesive tape.

  Conventionally, the thickness of the wafer has been reduced to about 200 to 400 μm by backside grinding. With the wafer thickness, there was no problem with peeling from the wafer even with a surface protection tape using a pressure-sensitive adhesive. In recent years, as semiconductor chips are miniaturized, the thickness of wafers has been reduced, and depending on the type of chip, the thickness has been reduced to about 50 μm. Also, with respect to the size, the conventional one having a maximum diameter of 8 inches tends to be increased to 12 inches or more.

  In addition, a heat-resistant resin film for protecting the semiconductor element itself may be formed on the semiconductor element on the wafer surface, but polyimide, polyamide, polyamideimide, polybenzoxazole, polybenzimidazole, benzocyclobutene, or these In the case of a film containing at least one compound selected from copolymers, it is generally known that the adhesion to the surface protection tape increases and peeling becomes difficult (see Patent Document 1). Furthermore, when the surface of the heat-resistant resin film is surface-modified by performing plasma treatment or the like, the adhesive force to the surface protective tape further increases (see Patent Document 2).

In wafers with such thin, large-diameter, heat-resistant resin films, surface protection tapes using conventional pressure-sensitive adhesives have high adhesive strength when they are peeled off and cannot be easily peeled off. There was a problem that the wafer was damaged. With respect to this problem, a technique is known that facilitates peeling by reducing the adhesive strength of the surface protective tape by irradiating ultraviolet rays or the like with the surface protective tape being applied to the wafer. However, even in such UV curable surface protection tape, when the wafer surface is modified, the adhesive strength is not sufficiently reduced, the wafer is damaged due to heavy peeling, and the tape cannot be peeled off. There was a problem that it would break.
JP-A-5-156215 JP 2007-59440 A

  The present invention provides a semiconductor wafer surface protective adhesive tape attached to a semiconductor wafer, and after grinding the back surface of the semiconductor wafer, in the step of peeling the tape, the wafer thickness, diameter, and surface, which were conventionally difficult to remove. An object of the present invention is to provide an adhesive tape for protecting the surface of a semiconductor wafer that can be satisfactorily peeled even in the film state (polyimide, benzocyclobutene, etc.).

The present invention
(1) A semiconductor wafer surface protecting pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on a base film, wherein the pressure-sensitive adhesive layer has a contact angle with methylene iodide at 23 ° C. of 40 ° C. or higher and 70 ° or lower. An adhesive tape for protecting the surface of a semiconductor wafer, wherein the adhesive strength of the tape to the polished surface of SUS280 is 1 N / 25 mm or less,
(2) The semiconductor wafer surface according to (1), wherein the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive having a carbon-carbon double bond in a polymer side chain, main chain or main chain terminal as a base polymer. Protective adhesive tape,
(3) The pressure-sensitive adhesive comprises, as a base polymer, a (meth) acrylic polymer having a side chain of an alkyl group having 4 to 12 carbon atoms, a photopolymerization initiator, and a curing agent. (2) Item (3) Item, wherein the pressure-sensitive adhesive tape for protecting a semiconductor wafer surface and (4) the (meth) acrylic polymer contains 30 mol% or more of a structural unit derived from 2-ethylhexyl acrylate monomer. (5) The content of the photopolymerization initiator in the adhesive is 0.01 to 5 parts by mass with respect to 100 parts by mass of the polymer (3) ) Adhesive tape for protecting the surface of a semiconductor wafer,
(6) The adhesive for semiconductor wafer surface protection according to (5), wherein the content of the curing agent in the adhesive is 0.01 to 10 parts by mass with respect to 100 parts by mass of the polymer. Tape.
In the present invention, the “SUS280 polished surface” means the surface of a SUS304 steel plate specified in JIS G 4305 finished with No. 280 water-resistant abrasive paper specified in JIS R 6253.

  The semiconductor wafer surface protective adhesive tape of the present invention is a condition in which, in the step of peeling the tape after grinding the back surface of the semiconductor wafer, it is conventionally difficult to peel depending on the thickness, diameter and surface state of the wafer. Also, it could be easily peeled off.

In the semiconductor wafer surface protective adhesive tape, at least one type of adhesive is applied to at least one surface of the base film to form an adhesive layer.
The pressure-sensitive adhesive layer of the present invention may be composed of one type of adhesive, or two or more different types of pressure-sensitive adhesives may be laminated, but the contact angle with respect to methylene iodide on the surface of the pressure-sensitive adhesive layer on the adherend side It is 40 degrees or more and 70 degrees or less, and the adhesive force with respect to the SUS280 grinding | polishing surface of an adhesive tape will be 1 N / 25mm or less. The pressure-sensitive adhesive on the adherend side is a radiation curable type in which the pressure-sensitive adhesive is cured by radiation such as ultraviolet rays and the adhesive strength is reduced. When two or more different types of pressure-sensitive adhesives are laminated, the pressure-sensitive adhesive other than the adherend may be either a pressure-sensitive pressure-sensitive adhesive or a radiation curable pressure-sensitive adhesive.

In this invention, the contact angle with respect to the methylene iodide of the adhesive layer surface means the contact angle immediately after the contact of the adhesive layer surface and methylene iodide. This contact angle is a value measured at a temperature of 23 ° C. and a humidity of 50%. The measurement can be performed using a commercially available contact angle measuring device.
In the present invention, the contact angle of methylene iodide on the surface of the pressure-sensitive adhesive layer is from 40 degrees to 70 degrees, preferably from 55 degrees to 70 degrees, and more preferably from 60 degrees to 70 degrees. This value is a value after the radiation curable adhesive is cured by radiation such as ultraviolet rays.
When the contact angle is too large, the hydrophilicity of the pressure-sensitive adhesive is increased, the adhesiveness with a highly hygroscopic polyimide is increased, and the peelability is remarkably deteriorated. On the other hand, if the contact angle is too small, the cohesive force of the pressure-sensitive adhesive is reduced, and adhesive residue tends to occur on the wafer surface.

  Moreover, the adhesive force with respect to the SUS280 polished surface of the adhesive tape for protecting a semiconductor wafer surface of the present invention is 1 N / 25 mm or less, preferably 0.7 N / 25 mm or less, more preferably 0.5 N / 25 mm or less. This value is a value after the radiation curable adhesive is cured by radiation such as ultraviolet rays.

The method for measuring the adhesive strength against the polished surface of SUS280 in the present invention will be described with reference to the explanatory diagram of FIG.
That is, three specimens (1) having a width of 25 mm and a length of 300 mm were collected from the adhesive tape, and the thickness specified in JIS G 4305 was finished with No. 280 water-resistant abrasive paper specified in JIS R 6253. Tensile test conforming to JIS B 7721 where the measured value falls within the range of 15 to 85% of its capacity after 3 hours reciprocation of 2 kg rubber roller on 5 mm to 2.0 mm SUS304 steel plate (2) The adhesive strength is measured using a machine (3). The measurement is based on the 90-degree peeling method, and the tensile speed at this time is 50 mm / min.
The measurement temperature is 23 ° C. and the measurement humidity is 50%.

  The type of the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer of the present invention is not particularly limited as long as it has the above contact angle and adhesive strength, but as a base polymer, a carbon-carbon double bond is polymerized. It is preferably a radiation curable pressure-sensitive adhesive comprising a polymer in the side chain or main chain or at the main chain terminal, a photopolymerization initiator, and a curing agent (crosslinking agent).

  The base polymer having a carbon-carbon double bond in the polymer side chain or in the main chain or at the end of the main chain has an alkyl group having 4 to 12 carbon atoms, more preferably 8 carbon atoms as the side chain ( A (meth) acrylic polymer obtained by homopolymerizing or copolymerizing one or more monomers such as a (meth) acrylic acid ester or a copolymerizable modifying monomer by an arbitrary method is preferable. Such a pressure-sensitive adhesive containing a (meth) acrylic polymer having an alkyl group having 4 to 12 carbon atoms as a side chain as a main polymer has low hydrophilicity and low adhesion to polyimide having high hygroscopicity. .

  In the present invention, a particularly suitable polymer is an acrylic polymer containing 40 mol% or more, more preferably 60 mol% or more of a structural unit derived from 2-ethylhexyl acrylate which is an acrylate monomer having an alkyl group side chain having 8 carbon atoms. It is a polymer.

  As the photopolymerization initiator, a photopolymerization initiator described in JP2007-146104A or JP2004-186429A can be used. For example, as a photopolymerization initiator, isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, benzylmethyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenylpropane, 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 radiation referred to here means light rays such as ultraviolet rays or ionizing radiations such as electron beams. It is preferable that content of a photoinitiator is 0.01-5 mass parts with respect to 100 mass parts of polymers, More preferably, it is 0.1-1 mass part.

  As the curing agent, a curing agent described in JP-A-2007-146104 can be used. 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 content of a hardening | curing agent according to desired adhesive force, 0.01-10 mass parts is preferable with respect to 100 mass parts of polymers, More preferably, it is 0.1-5 mass parts. is there.

  The pressure-sensitive adhesive layer in the present invention can contain other components in addition to the above components as long as the object of the present invention is not impaired.

  Examples of the material for the base film used in the present invention include those described in JP-A No. 2004-186429. As the substrate film, known materials can be used, such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ionomer, etc. And α-olefin homopolymers or copolymers, engineering plastics such as polyethylene terephthalate, polycarbonate, and polymethyl methacrylate, and thermoplastic elastomers such as polyurethane, styrene-ethylene-butene, and pentene copolymers. Alternatively, a mixture of two or more selected from these groups or a multilayered structure may be used. As for the thickness of a base film, 50-200 micrometers is preferable.

  In order to form the above-mentioned pressure-sensitive adhesive layer on the base film, at least one type of pressure-sensitive adhesive may be applied by any method to at least one side of the base film. As for the thickness of an adhesive layer, 10-300 micrometers is preferable. Moreover, you may provide intermediate | middle layers, such as a primer layer, as needed between a base film and an adhesive layer.

  Moreover, you may stick the synthetic resin film normally used as a separator on the adhesive layer side in order to protect an adhesive layer until it uses for practical use as needed.

  If an adhesive tape for protecting the surface of a semiconductor wafer is used, for example, a heat-resistant resin film formed on a semiconductor element on the wafer surface may be polyimide, polyamide, polyamideimide, polybenzoxazole, polybenzimidazole, benzocyclobutene, or these A film containing one or more compounds selected from the above copolymers, and the film is surface-modified by plasma or the like, and can be peeled without breakage even in the processing step of a wafer having a thickness of 100 μm and a diameter of 12 inches Is possible.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
Tables 1 and 2 show the results obtained by measuring the post-UV adhesive strength of SUS # 280 and the contact angle of methylene iodide on the surface of the pressure-sensitive adhesive layer with respect to the pressure-sensitive adhesive tapes of Examples and Comparative Examples.

(1) SUS # 280 post-UV adhesive strength Three test pieces of width 25 mm × length 300 mm were collected from the adhesive tapes of the examples and comparative examples, and a distance was measured using one 80 W / cm metal halide high-pressure mercury lamp. Irradiation was performed so that the irradiation amount was 500 mJ / cm ^{2 at a} distance of about 100 mm. In the same manner as in the method shown in FIG. 1, 2 kg of the sample is placed on a SUS steel plate having a thickness of 1.5 mm to 2.0 mm specified in JIS G 4305 finished with 280th water-resistant abrasive paper specified in JIS R 6253. The rubber roller of No. 3 was pressure-bonded three times, and after standing for 1 hour, the adhesion was measured using a tensile tester conforming to JIS B 7721 whose measured value was in the range of 15 to 85% of its capacity.
The measurement was performed by a 90-degree peeling method, and the tensile speed at this time was 50 mm / min. The measurement temperature is 23 ° C. and the measurement humidity is 50%.

(2) Methylene iodide contact angle on the pressure-sensitive adhesive layer surface The methylene iodide contact angle on the pressure-sensitive adhesive layer surface was measured by the method shown in the explanatory diagram of FIG.
First, the separator 13 is bonded to the surface of the pressure-sensitive adhesive layer of Examples and Comparative Examples in which the pressure-sensitive adhesive layer 12 is formed on the base film 11 (FIG. 2A). Next, since it is necessary to perform measurement on a flat surface, the surface of the base film 11 on which the adhesive layer 12 is not provided is fixed to a wafer 15 having a flat surface using a double-sided tape 14. (FIG. 2 (b)). Next, UV irradiation was performed from the separator 13 side so as to be 500 mJ / cm ² (FIG. 2C). Then, after leaving for 1 hour, the separator 13 was peeled off, methylene iodide 16 was dropped, and the contact angle θ was measured using a FACE contact angle meter CA-S150 manufactured by Kyowa Chemical Co., Ltd. (FIG. 2 (d )). The measurement temperature is 23 ° C. and the measurement humidity is 50%.

Example 1
Photopolymerization initiator for 100 parts by mass of base polymer A having a carbon-carbon double bond in the polymer side chain, containing 69 mol% of 2-ethylhexyl acrylate on a 200 μm thick base film made of low density polyethylene (LDPE) An adhesive containing 0.5 part by mass and 8 parts by mass of a curing agent was applied to form an adhesive layer having a dry thickness of 50 μm, and an adhesive tape was produced.
The adhesive layer of this adhesive tape had a post-UV adhesive strength of SUS # 280 of 0.2 N / 25 mm, and the methylene iodide contact angle on the adhesive surface was 62 °.

Example 2
SUS # of a pressure-sensitive adhesive tape using a base film made of low-density polyethylene (LDPE) having a thickness of 100 μm, the weight part of the curing agent of the pressure-sensitive adhesive used being 1 part by weight, and the dry thickness of the pressure-sensitive adhesive layer being 40 μm An adhesive tape was prepared in the same manner as in Example 1 except that the post-UV adhesive strength of 280 was 0.3 N / 25 mm and the contact angle of methylene iodide on the adhesive surface was 67 °.

Example 3
The pressure-sensitive adhesive strength of the pressure-sensitive adhesive tape SUS # 280 was 0.2 N / 25 mm and the pressure-sensitive adhesive surface had a dry thickness of 30 μm. An adhesive tape was produced in the same manner as in Example 2 except that the contact angle of methylene iodide was 62 °.

Example 4
A base polymer B having a carbon-carbon double bond containing 57 mol% of 2-ethylhexyl acrylate and 15 mol% of methyl methacrylate in a polymer side chain, using a base film having a thickness of 100 μm made of low density polyethylene (LDPE) It contains 2.5 parts by mass of a photopolymerization initiator and 4 parts by mass of a curing agent with respect to 100 parts by mass, the adhesive strength after UV of SUS # 280 is 0.6 N / 25 mm, and the contact angle of methylene iodide on the surface of the adhesive is An adhesive tape was prepared in the same manner as in Example 1 except that the angle was 58 °.

Example 5
The pressure-sensitive adhesive surface after UV of SUS # 280 of the pressure-sensitive adhesive tape in which the weight part of the photopolymerization initiator of the pressure-sensitive adhesive used was 5 parts by weight and the dry thickness of the pressure-sensitive adhesive layer was 30 μm was 0.5 N / 25 mm. An adhesive tape was prepared in the same manner as in Example 4 except that the contact angle of methylene iodide was 47 °.

Comparative Example 1
SUS # 280 adhesive strength after UV of 2.0 N / 25 mm and methylene iodide contact angle on the pressure-sensitive adhesive surface was set to 65 °. Except for the above, an adhesive tape was prepared in the same manner as in Example 5.

Comparative Example 2
5 parts by mass of a photopolymerization initiator and 4 parts by mass of a curing agent with respect to 100 parts by mass of a base polymer C having a carbon-carbon double bond containing 24 mol% of 2-ethylhexyl acrylate and 61.5 mol% of methyl methacrylate in the polymer side chain. The adhesive tape was made in the same manner as in Example 5 except that an adhesive with a post-UV adhesive strength of SUS # 280 of 2.5 N / 25 mm and a methylene iodide contact angle of 85 ° on the adhesive surface was used. A tape was prepared.

Comparative Example 3
A pressure-sensitive adhesive tape comprising 150 parts by mass of a radiation curable oligomer, 10 parts by mass of a photopolymerization initiator, and 4 parts by mass of a curing agent with respect to 100 parts by mass of a base polymer D containing 33 mol% of 2-ethylhexyl acrylate and 60 mol% of methyl acrylate. A pressure-sensitive adhesive tape was prepared in the same manner as in Example 5 except that a pressure-sensitive adhesive having a post-UV adhesive strength of SUS # 280 of 1.2 N / 25 mm and a methylene iodide contact angle of 89 ° was used.

Comparative Example 4
Comparative Example 3 except that the adhesive strength after UV of SUS # 280 of the pressure-sensitive adhesive tape with 100 parts by mass of the pressure-sensitive adhesive oligomer used was 0.2 N / 25 mm and the contact angle of methylene iodide on the pressure-sensitive adhesive surface was 85 °. An adhesive tape was prepared in the same manner.

Comparative Example 5
Comparative Example 3 except that the pressure-sensitive adhesive tape after UV of SUS # 280 was 0.3 N / 25 mm and the contact angle of methylene iodide on the pressure-sensitive adhesive surface was 87 ° with 75 parts by mass of the pressure-sensitive adhesive oligomer used. An adhesive tape was prepared in the same manner.

Test Example (1) UV post-adhesive strength to special polyimide (PI) surface or special benzocyclobutene (BCB) surface About the adhesive tapes prepared in Examples and Comparative Examples, in the above (1) adhesive strength measurement method, SUS steel plate Instead, a 5 μm-thick polyimide film is formed on a silicon wafer, and a special PI surface whose surface is modified by ashing or a 5 μm-thick benzocyclobutene film is formed on a silicon wafer, and the surface is modified by plasma treatment. Measurement was performed using a special BCB surface. The results are shown in Tables 1-2. In the table, the adhesive strength to the special PI surface is shown as (PI), and the adhesive strength to the special BCB surface is shown as (BCB). The unit of the numerical value is N / 25 mm.
(2) Peelability About the adhesive tape produced by the Example and the comparative example, a sticking machine sticks using DR8500II by Nitto Seiki Co., Ltd., and a grinder is grind | polished to thickness 200 micrometers by DFG8540 made from DISCO Corporation. did. Furthermore, the surface protection tape for semiconductors of this invention was affixed on the special polyimide surface or special benzocyclobutene surface of an 8-inch wafer. Then, 25 sheets were peeled off using UV irradiation and HR8500II manufactured by Nitto Seiki Co., Ltd. The tape was peeled off from the wafer without any problems. “Good”. No damage to the wafer during peeling. Only one of the 25 wafers was slightly displaced from the chuck table. In the case of 24 sheets, what was peeled off was regarded as "substantially good", and when peeling, only the peeling tape of the surface protection tape peeled off, the wafer detached from the chuck table, or the wafer was damaged. Was “NG”. The results are shown in Tables 1-2.

  As shown in Tables 1 and 2, the pressure-sensitive adhesive tapes of Comparative Examples 1 to 5 have poor peelability, and any of the above problems occur during peeling. On the other hand, it was found that all of the pressure-sensitive adhesive tapes of Examples 1 to 5 had good or almost good peelability and could be used without any problem as a surface protective tape.

It is explanatory drawing of the adhesive force measuring method with respect to the SUS280 grinding | polishing surface in this invention. It is explanatory drawing of the measuring method of the methylene iodide contact angle of the adhesive layer surface in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adhesive tape test piece 2 SUS steel plate 3 Tensile tester 11 Base film 12 Adhesive layer 13 Separator 14 Double-sided tape 15 Surface flat wafer 16 Methylene iodide

Claims (6)

  A pressure-sensitive adhesive tape for protecting a semiconductor wafer surface having a pressure-sensitive adhesive layer on a base film, wherein the pressure-sensitive adhesive layer has a contact angle with methylene iodide at 23 ° C. of 40 ° C. or more and 70 ° or less. An adhesive tape for protecting the surface of a semiconductor wafer, wherein the adhesive strength to the polished surface of SUS280 is 1 N / 25 mm or less.   2. The pressure-sensitive adhesive tape for protecting a semiconductor wafer surface according to claim 1, wherein the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive having a carbon-carbon double bond in a polymer side chain, main chain or main chain terminal as a base polymer. .   3. The pressure-sensitive adhesive comprises a (meth) acrylic polymer having a side chain of an alkyl group having 4 to 12 carbon atoms, a photopolymerization initiator, and a curing agent as a base polymer. The adhesive tape for semiconductor wafer surface protection of description.   The pressure-sensitive adhesive tape for protecting a semiconductor wafer according to claim 3, wherein the (meth) acrylic polymer contains 40 mol% or more of a structural unit derived from 2-ethylhexyl acrylate.   The pressure-sensitive adhesive tape for semiconductor wafer surface protection according to claim 3, wherein the content of the photopolymerization initiator in the pressure-sensitive adhesive is 0.01 to 5 parts by mass with respect to 100 parts by mass of the polymer.   6. The adhesive tape for protecting a semiconductor wafer surface according to claim 5, wherein the content of the curing agent in the pressure-sensitive adhesive is 0.01 to 10 parts by mass with respect to 100 parts by mass of the polymer.

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