JP6550271B2 - Back grind tape - Google Patents

Description

  The present invention relates to backgrind tape.

  Conventionally, when processing a semiconductor wafer, in a back grinding step of grinding the back surface of the semiconductor wafer to a desired thickness, adhesion is used to fix the semiconductor wafer and protect the surface opposite to the grinding surface. Tape (back grind tape) is used (for example, patent document 1). Usually, a backgrind tape is composed of a substrate and an adhesive layer. Such a back grind tape is used by sticking the adhesive layer side to the surface of the semiconductor wafer (the surface opposite to the grinding surface of the wafer), and is peeled off and discarded after grinding the back surface of the semiconductor wafer. .

  When the circuit surface of the semiconductor wafer is protected by the above-mentioned backgrind tape, after peeling off the tape, traces of the uneven circuit shape remain as replicas in the adhesive layer and the state is maintained for a long time or permanently . If the backgrind tape after use is discarded in such a state, there is a possibility that the circuit shape as secret information may leak.

JP, 2011-151163, A

  The present invention has been made to solve the above-described conventional problems, and the object of the present invention is to provide a pressure-sensitive adhesive layer with a concavo-convex shape when it is attached to a concavo-convex surface (for example, a circuit surface of a semiconductor wafer). It is about providing the back grinding tape which does not remain.

The back grind tape of the present invention comprises a substrate and an adhesive layer disposed on one side of the substrate, and the stress relaxation amount of the adhesive layer is 12 kPa or less.
In one embodiment, the storage elastic modulus at 23 ° C. of the pressure-sensitive adhesive layer is 0.1 MPa or less.
In one embodiment, the loss tangent (tan δ) at 23 ° C. of the pressure-sensitive adhesive layer is 0.15 or more.
In one embodiment, the gel fraction of the pressure-sensitive adhesive layer is 50% to 95%.

  According to the present invention, by setting the stress relaxation amount of the pressure-sensitive adhesive layer to a specific value, the uneven shape (replica shape) generated in the pressure-sensitive adhesive layer when attached to an uneven surface (for example, a circuit surface of a semiconductor wafer) Can provide a back grind tape which can be rapidly eliminated.

FIG. 1 is a schematic cross-sectional view of a backgrind tape according to one embodiment of the present invention.

A. Overall Structure of Backgrind Tape FIG. 1 is a schematic cross-sectional view of a back grind tape according to an embodiment of the present invention. The backgrind tape 100 includes a substrate 10 and an adhesive layer 20 disposed on one side of the substrate 10. Although not shown, the backgrind tape of the present invention may be provided with a release liner on the outside of the pressure-sensitive adhesive layer for the purpose of protecting the adhesive surface until it is used.

  The thickness of the backgrind tape is preferably 50 μm to 500 μm, more preferably 150 μm to 350 μm. With such a range, it is possible to obtain a back grind tape capable of improving the back surface grinding accuracy of the semiconductor wafer.

  The adhesive strength at 25 ° C. of the backgrind tape is preferably 0.1 N / 20 mm to 5 N / 20 mm, more preferably 0.2 N / 20 mm to 3 N / 20 mm. In this specification, adhesive force refers to a method according to JIS Z 0237 (2000) using a mirror wafer (made of silicon) as a test plate (bonding conditions: 2 kg roller, 1 reciprocation, aging: 1 hour under measurement temperature) , Peeling speed: 300 mm / min, Peeling angle: 90 °).

B. Pressure-sensitive adhesive layer The stress relaxation amount of the pressure-sensitive adhesive layer is 12 kPa or less, preferably 8 kPa, more preferably 2 kPa to 8 kPa, and still more preferably 3 kPa to 6 kPa. The “stress relaxation amount” means that the adhesive layer alone is a strip-like sample, and the length of the measurement portion of the sample is (initial length + 15 mm) in an environment of 23 ° C./50% RH. From the stress (S1) after stretching in the longitudinal direction and immediately after stretching, the stress (S2) after maintaining the state after stretching (initial length + 15 mm) for 1 minute, and the cross-sectional area (d) of the sample, | S1 It is calculated | required by the formula of -S2 | / d. The stress is measured using a tensile tester under conditions of a chuck distance of 30 mm and a tensile speed of 200 mm / min. A sample having a width of 10 mm and a length of 50 mm (the length of the measurement portion (initial length) 30 mm) may be used as the sample. The thickness of the sample is set to, for example, 2 mm.

  In the present invention, by setting the stress relaxation amount of the pressure-sensitive adhesive layer in the above range, the adhesive layer is attached to the uneven surface (for example, the circuit surface) of the semiconductor wafer and then transferred to the pressure-sensitive adhesive layer when peeled off. It is possible to obtain a back grind tape in which the uneven shape (replica shape) can disappear quickly. In the uneven surface of the semiconductor wafer, the height of the projections is, for example, 5 μm to 50 μm, and preferably 5 μm to 20 μm. In the backgrind tape of the present invention, the tape is peeled off from the uneven surface, for example, within 40 hours, preferably within 36 hours, more preferably within 24 hours, still more preferably within 12 hours, most preferably 4 hours Within the surface, the uneven shape (replica shape) generated in the pressure-sensitive adhesive layer disappears.

  The stress relaxation amount of the pressure-sensitive adhesive layer is, for example, the type, molecular weight and / or degree of crosslinking of the base polymer contained in the pressure-sensitive adhesive; the type and / or amount of crosslinking agent contained in the pressure-sensitive adhesive; It can be adjusted by the type and / or amount of

  The storage elastic modulus G ′ at 23 ° C. of the pressure-sensitive adhesive layer is preferably 0.1 MPa or less, more preferably 0.09 MPa or less, and still more preferably 0.03 MPa to 0.09 MPa, particularly preferably It is 0.05MPa-0.09MPa. A backgrind tape provided with a pressure-sensitive adhesive layer having such a storage elastic modulus can contribute to the achievement of excellent grinding accuracy in the backgrind process. According to the present invention, excellent grinding accuracy can be realized, and as described above, it is possible to obtain a back grind tape in which the replica shape rapidly disappears. The measuring method of storage elastic modulus G 'is mentioned later.

  The loss tangent (tan δ) at 23 ° C. of the pressure-sensitive adhesive layer is preferably 0.15 or more, more preferably 0.15 to 0.25, and still more preferably 0.15 to 0.22. Within such a range, it is possible to obtain a back grind tape that can contribute to the achievement of excellent grinding accuracy in the back grind process. The loss tangent (tan δ) refers to the ratio (G ′ ′ / G ′) of the loss modulus (G ′ ′) at 23 ° C. of the adhesive layer to the storage modulus (G ′) at 23 ° C. The method of measuring the loss tangent (tan δ) will be described later.

The gel fraction of the pressure-sensitive adhesive layer is preferably 50% to 95%, more preferably 55% to 85%. The gel fraction is measured as follows. About 0.1 g of the pressure-sensitive adhesive layer is wrapped in a Teflon (registered trademark) sheet (trade name "NTF1122" manufactured by Nitto Denko Corporation) having a 0.2 μm diameter hole, and then tied with a silk thread, The weight is measured, and the weight is taken as the weight before immersion. The weight before immersion is the total weight of the pressure-sensitive adhesive layer, the Teflon sheet, and the cocoon thread. Also, the weight of the teflon sheet and the cocoon thread to be used is also measured, and the weight is taken as the weight of the package. Next, the pressure-sensitive adhesive layer is wrapped with a teflon sheet, and the one bound with a cocoon thread is put in a 50 ml container filled with ethyl acetate and left at room temperature for 1 week. Thereafter, the Teflon sheet is removed from the container and dried in a drier at 130 ° C. for 2 hours to remove ethyl acetate, and then the sample weight is measured, and the weight is taken as the weight after immersion. Then, the gel fraction is calculated from the following equation. In addition, in the following formula, A is a weight after immersion, B is a package weight, and C is a weight before immersion.
Gel fraction (% by weight) = (A-B) / (C-B) × 100

  The thickness of the pressure-sensitive adhesive layer is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and still more preferably 30 μm to 100 μm. A backgrind tape provided with an adhesive layer of such a thickness can contribute to the achievement of excellent grinding accuracy in the backgrind process.

  The pressure-sensitive adhesive layer may be formed of any appropriate pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include curable pressure-sensitive adhesives such as thermosetting pressure-sensitive adhesives and active energy ray-curable pressure-sensitive adhesives; polyolefin-based pressure-sensitive adhesives; acrylic pressure-sensitive adhesives; and styrene-based pressure-sensitive adhesives. Preferably, a curable adhesive (more preferably, a thermosetting adhesive) containing a curable resin as a base polymer is used.

  As a base polymer contained in the said curable adhesive, acrylic resin which has a curable functional group in a side chain, in a principal chain, or at least one of the principal chain terminal, rubber-type resin, silicone resin, polyvinyl Ether resin etc. are mentioned. The curable pressure sensitive adhesive may also contain a curable monomer component and / or a curable oligomer component. A curable monomer component and / or a curable oligomer component may be added to the pressure-sensitive adhesive containing the base polymer having the curable functional group.

  Any appropriate acrylic resin can be used as the acrylic resin. For example, as said acrylic resin, resin which contains (meth) acrylic acid ester as a main monomer component is mentioned. Examples of the (meth) acrylic acid ester include methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, sec-butyl ester, t-butyl ester, pentyl ester, isopentyl ester, hexyl ester, Heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester, tridecyl ester, tetradecyl ester, hexadecyl ester, octadecyl ester, eicosyl ester (Meth) acrylic acid alkyl ester containing a linear or branched alkyl group having 1 to 30 carbon atoms, such as: cyclopentyl ester, cyclohexy (Meth) cycloalkyl esters of acrylic acid such as esters. One of these monomers may be used alone, or two or more thereof may be used in combination.

  The acrylic resin may contain, as a monomer component, another copolymerizable monomer copolymerizable with the (meth) acrylic acid ester, if necessary. As another copolymerizable monomer, for example, a carboxyl group- or acid anhydride group-containing monomer such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic anhydride; hydroxyl such as 2-hydroxyethyl (meth) acrylate Group-containing monomers; amino group-containing monomers such as morpholine (meth) acrylate; and amide group-containing monomers such as (meth) acrylamide. The content ratio of the structural unit derived from the above-mentioned copolymerizable monomer is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and still more preferably 2.5 parts by weight with respect to 100 parts by weight of the base polymer. 10 parts by weight.

  Moreover, the said acrylic resin may contain the hydroxyl group containing monomer which can be copolymerized with the said acrylic ester as a monomer component. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, Examples thereof include 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate. The above-mentioned hydroxyl group-containing monomer may be used alone or in combination of two or more.

  Moreover, the said adhesive may further contain the isocyanate type compound which has a curable functional group in a molecule | numerator. Examples of the isocyanate compound include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl isocyanate and the like.

  The acrylic resin can be obtained by polymerizing the monomer component by any appropriate polymerization method. Examples of the polymerization method include solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization and the like.

  Any appropriate compound can be used as the curable monomer component or oligomer component. For example, the above-mentioned isocyanate compound, urethane oligomer, urethane (meth) acrylate, trimethylol propane tri (meth) acrylate, tetramethylol methane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate And dipentaerythritol monohydroxy penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,4-butanediol di (meth) acrylate and the like.

  The weight average molecular weight of the base polymer constituting the pressure-sensitive adhesive is preferably 200,000 to 3,000,000, and more preferably 250,000 to 1,500,000. The weight average molecular weight can be measured by GPC (solvent: THF).

  The glass transition temperature of the base polymer constituting the pressure-sensitive adhesive is preferably -70 ° C to -20 ° C, more preferably -60 ° C to -40 ° C.

  The pressure-sensitive adhesive may further contain any appropriate additive. As said additive, a polymerization initiator, a crosslinking agent, a plasticizer, a tackifier, an antiaging agent, a filler, a coloring agent, an antistatic agent, surfactant, etc. are mentioned, for example. The above additives may be used alone or in combination of two or more. When two or more additives are used, they may be added one by one or two or more additives may be added simultaneously. The compounding amount of the additive may be set to any appropriate amount.

  Any appropriate crosslinking agent can be used as the above-mentioned crosslinking agent. For example, isocyanate type crosslinking agent, epoxy type crosslinking agent, melamine type crosslinking agent, peroxide type crosslinking agent, urea type crosslinking agent, metal alkoxide type crosslinking agent, metal chelate type crosslinking agent, metal salt type crosslinking agent, carbodiimide type crosslinking Agents, oxazoline based crosslinking agents, aziridine based crosslinking agents, amine based crosslinking agents and the like. The crosslinking agent may be used alone or in combination of two or more. In addition, the usage-amount of a crosslinking agent may be set to arbitrary appropriate values according to a use application. The amount of the crosslinking agent used is preferably 20 parts by weight or less, more preferably 1 part by weight to 6 parts by weight, and still more preferably 1.8 parts by weight to 5 parts by weight with respect to 100 parts by weight of the base polymer It is. Within such a range, a pressure-sensitive adhesive layer can be formed in which the elastic modulus and the amount of stress relaxation are appropriate.

  Any appropriate plasticizer can be used as the above-mentioned plasticizer. For example, in addition to carboxylic acid ester plasticizers such as phthalic acid ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, adipic acid ester plasticizers, etc., phosphoric acid plasticizers, epoxy resins Plasticizers, polyester plasticizers (low molecular weight polyester etc.) and the like can be mentioned. The amount of the plasticizer used is preferably 30 parts by weight or less, more preferably 5 parts by weight to 25 parts by weight, and still more preferably 8 parts by weight to 15 parts by weight with respect to 100 parts by weight of the base polymer . Within such a range, a pressure-sensitive adhesive layer can be formed in which the elastic modulus and the amount of stress relaxation are appropriate.

  The back grind tape of the present invention can be manufactured by applying the above-mentioned adhesive on the above-mentioned base material. Coating methods include bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexo printing, screen printing, etc. Various methods can be employed. Alternatively, a pressure-sensitive adhesive layer may be separately formed on the release liner, and then the pressure-sensitive adhesive layer may be bonded to the base material layer or the antistatic layer.

  When a curable pressure-sensitive adhesive is used as the pressure-sensitive adhesive, the pressure-sensitive adhesive layer may be subjected to a curing treatment to adjust the characteristics (adhesive strength, elastic modulus, etc.) of the pressure-sensitive adhesive layer. Examples of the curing treatment include ultraviolet irradiation, heat treatment and the like.

C. Substrate Any appropriate material may be selected as the material constituting the substrate . As a material which comprises a base material, resin-type material (for example, sheet-like, net-like, woven fabric, a nonwoven fabric, a foam sheet), paper, a metal etc. are mentioned. The substrate may be a single layer or a multilayer composed of the same or different materials. Specific examples of the resin constituting the substrate layer include, for example, polyester, polyolefin, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, Ethylene-butene copolymer, ethylene-hexene copolymer, polyurethane, polyether ketone, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, cellulose type Examples thereof include resins, fluorine resins, silicone resins, polyethers, polystyrene resins (such as polystyrene), polycarbonates, polyether sulfones, and cross-linked products thereof.

  The substrate can be manufactured in any suitable manner. For example, it can be manufactured by methods such as calendar film formation, casting film formation, inflation extrusion, T-die extrusion and the like. Moreover, you may manufacture by performing an extending | stretching process as needed.

  Depending on the purpose, the substrate may be subjected to any suitable surface treatment. Examples of the surface treatment include chromic acid treatment, ozone exposure, flame exposure, high piezoelectric bombardment exposure, ionizing radiation treatment, matting treatment, corona discharge treatment, primer treatment, crosslinking treatment and the like.

  The thickness of the substrate is preferably 10 μm to 300 μm, and more preferably 30 μm to 200 μm.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In the examples, "parts" and "%" are by weight unless otherwise specified.

Example 1
100 parts by weight of butyl acrylate and 3 parts by weight of acrylic acid were polymerized to obtain a resin liquid containing an acrylic resin having a weight average molecular weight of 1,000,000. In the obtained resin liquid, 0.03 parts by weight of an epoxy-based crosslinking agent (Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), and 2 parts by weight of an isocyanate-based crosslinking agent (Tosoh Corp., trade name "Colonate L") A pressure-sensitive adhesive was obtained by adding 1 part and 15 parts by weight of a plasticizer (trade name "W-230-H" manufactured by DIC Corporation).
The obtained pressure-sensitive adhesive is applied to a separator (Mitsubishi Chemical Co., Ltd., trade name "MRF36") and heated at 120 ° C. for 2 minutes to form a pressure-sensitive adhesive layer (thickness: 55 μm). Transfer to the ethylene vinyl acetate copolymer film side of the material (a base formed by laminating an ethylene vinyl acetate copolymer film with a thickness of 85 μm and a random polypropylene film with a thickness of 30 μm), and it comprises a substrate and an adhesive layer I got a back grind tape.

Example 2
A back grind tape was obtained in the same manner as Example 1, except that the compounding amount of the epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C") was 0.05 parts by weight.

[Example 3]
A back grind tape was obtained in the same manner as Example 1, except that the compounding amount of the epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C") was changed to 0.09 parts by weight.

Example 4
A back grind tape was obtained in the same manner as Example 1, except that the compounding amount of the epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C") was 0.13 parts by weight.

[Example 5]
A back grind tape was obtained in the same manner as Example 1, except that the compounding amount of the epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C") was 0.15 parts by weight.

[Example 6]
In the same manner as in Example 1, except that the compounding amount of the epoxy-based crosslinking agent (Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C") was 0.09 parts by weight, and the thickness of the pressure-sensitive adhesive layer was 90 μm. I got a grind tape.

Comparative Example 1
87 parts by weight of butyl acrylate, 13 parts by weight of acrylonitrile and 2 parts by weight of acrylic acid were polymerized to obtain a resin liquid containing an acrylic resin having a weight average molecular weight of 1,000,000. To the obtained resin solution, 4 parts by weight of a melamine-based crosslinking agent (trade name "Super Beckcamine J-820-60N" manufactured by DIC Corporation) and an isocyanate-based crosslinking agent (trade name "Corronate L" manufactured by Tosoh Corp.) 3 parts by weight and 30 parts by weight of dioctyl phthalate as a plasticizer were added to obtain an adhesive.
The obtained pressure-sensitive adhesive is applied to a separator (Mitsubishi Chemical Co., Ltd., trade name "MRF36") and heated at 120 ° C. for 2 minutes to form a pressure-sensitive adhesive layer (thickness: 45 μm). It transferred to the base material (thickness: 115 micrometers) comprised from a vinyl copolymer, and obtained the back grind tape which consists of a base material and an adhesive layer.

Comparative Example 2
A back grind tape was obtained in the same manner as in Comparative Example 1 except that the thickness of the pressure-sensitive adhesive layer was 65 μm.

Comparative Example 3
100 parts by weight of butyl acrylate, 78 parts by weight of ethyl acrylate, 40 parts by weight of hydroxyl ethyl acrylate, and 42.6 parts by weight of 2-isocyanatoethyl methacrylate (trade name "Kalens MOI" manufactured by Showa Denko KK) Were polymerized to obtain a resin liquid containing an acrylic resin having a weight average molecular weight of 500,000. 0.2 parts by weight of an isocyanate-based crosslinking agent (Tosoh Corp., trade name "Coronato L") and 3 parts by weight of a photopolymerization initiator (manufactured by BASF Corp., Irgacure 651) are added to the obtained resin solution , Got an adhesive.
The obtained pressure-sensitive adhesive is applied to a separator (Mitsubishi Chemical Co., Ltd., trade name "MRF36") and heated at 120 ° C. for 2 minutes to form a pressure-sensitive adhesive layer precursor layer, and the precursor layer is a PET substrate (Toray Industries, Ltd.) It transferred to the company make and brand name "Lumirror S105". Thereafter, the precursor layer was irradiated with UV (irradiation dose: 300 mJ / cm ² ) to form a pressure-sensitive adhesive layer, to obtain a back grind tape. In addition, in the case of following evaluation (4) and (5), after sticking to a wafer, said UV irradiation was performed to the adhesive layer.

<Evaluation>
The back grind tapes obtained in Examples and Comparative Examples were subjected to the following evaluation. The results are shown in Table 1.
(1) Stress Relaxation Amount An adhesive layer (width 10 mm × length 50 mm × thickness 2 mm) having the same composition as that of each example and comparative example was formed and used as a sample.
A tensile test was conducted under the following conditions using an A & D Tenselon universal material tester.
・ Temperature: 23 ° C
Humidity: 50%
-Distance between chucks: 30 mm
-Pulling speed: 200 mm / min
The tensile test was started under the above conditions, and the sample was stretched until the distance between the chucks was 45 mm (that is, the initial length + 15 mm). From the stress (S1) immediately after stretching, the stress (S2) after maintaining the state after stretching (initial length + 15 mm) for 1 minute, and the cross-sectional area (d) of the sample, | S1-S2 | / d The stress relaxation amount was determined by the equation.
(2) Storage elastic modulus G ', tan δ
A pressure-sensitive adhesive layer (width 10 mm × length 50 mm × thickness 2 mm) having the same composition as that of each example and comparative example is formed, and a viscoelasticity measuring apparatus (trade name “ARES-G2” manufactured by TA Instruments) is used. Storage modulus G 'and tan δ at 23 ° C. were measured. The measurement conditions are as follows.
-Mode: Torsion mode-Plate diameter: 7.9 mmφ
Distortion: 1% (25 ° C)
・ Frequency: 1 Hz
・ Measurement range: -20 ° C to 100 ° C
(3) Gel fraction of pressure-sensitive adhesive layer Approximately 0.1 g of the pressure-sensitive adhesive layer was wrapped in a Teflon (registered trademark) sheet (trade name "NTF1122", manufactured by Nitto Denko Corporation) having a 0.2 μm diameter hole. After that, it was tied with a cocoon thread, the weight at that time was measured, and this weight was taken as the weight before immersion. The weight before immersion is the total weight of the pressure-sensitive adhesive layer, the Teflon sheet, and the cocoon thread. Moreover, the weight of the Teflon sheet and the cocoon thread to be used was also measured, and the above-mentioned weight was used as the weight of the packaging. Next, the pressure-sensitive adhesive layer was wrapped with a Teflon sheet, and the one bound with a cocoon was put in a 50 ml container filled with ethyl acetate and allowed to stand at room temperature for 1 week. Thereafter, the Teflon sheet was removed from the container and dried in a drier at 130 ° C. for 2 hours to remove ethyl acetate, and then the sample weight was measured, and the weight was taken as the weight after immersion. The gel fraction was calculated from the following equation. In addition, in the following formula, A is a weight after immersion, B is a package weight, and C is a weight before immersion.
Gel fraction (% by weight) = (A-B) / (C-B) × 100
(4) Fillability A wafer was prepared in which convex portions of height 12 μm × width 20 μm × length 125 μm were formed in the width direction at intervals of 18 μm.
The back grind tape (width: 20 mm) obtained in Examples and Comparative Examples was attached to the convex portion forming surface of this wafer at room temperature using a 5 kg roller. 30 minutes after sticking, the sticking state of the back grind tape was confirmed. Pass the back grind tape which has no bubbles between the wafer and the back grind tape and is excellent in filling property (○ in the table), air bubbles are generated between the convex part and the back grind tape, and the back grind tape is enough for the wafer The case where it did not fill in was made into rejection (in the table, x).
(5) Time to Disappearance of Replica In the same manner as in the above evaluation (4), a back grind tape was attached to the wafer.
Thereafter, the back grind tape was peeled off from the wafer, and the back grind tape was placed in an environment of 23 ° C. and 50% RH. The pressure-sensitive adhesive layer surface of the above-mentioned back grind tape is observed every hour using a laser microscope VK-8500 manufactured by KEYENCE Corporation, and the time until the replica shape of the wafer formed in the pressure-sensitive adhesive layer disappears is measured did.

  As apparent from Table 1, according to the present invention, by setting the stress relaxation amount of the pressure-sensitive adhesive layer to a specific value or less, a back grind tape which can lose the replica shape of the uneven surface formed in the pressure-sensitive adhesive layer You can get it. In addition, if the storage elastic modulus and tan δ of the pressure-sensitive adhesive layer are appropriately adjusted, it is possible to obtain a back grind tape capable of satisfactorily filling the uneven surface of the semiconductor wafer as the adherend.

10 base 20 adhesive layer 100 back grind tape

Claims (4)

A substrate, and an adhesive layer disposed on one side of the substrate,
The stress relaxation amount of the pressure-sensitive adhesive layer is 12 kPa or less
When the stress relaxation amount is a strip-like sample of the pressure-sensitive adhesive layer, and the length of the measurement portion becomes (initial length + 15 mm) in an environment of 23 ° C./50% RH, the length direction From the stress (S1) immediately after stretching and the stress (S2) after maintaining the state after stretching (initial length + 15 mm) for 1 minute, and the cross-sectional area (d) of the sample, | S1-S2 | Obtained by the equation of / d,
Back grind tape.   The back grind tape of Claim 1 whose storage elastic modulus at 23 degrees C of the said adhesive layer is 0.1 Mpa or less.   The back grind tape according to claim 1 or 2, wherein the loss tangent (tan δ) at 23 ° C of the pressure-sensitive adhesive layer is 0.15 or more.   The back grind tape according to any one of claims 1 to 3, wherein the gel fraction of the pressure-sensitive adhesive layer is 50% to 95%.

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