JP5950869B2 - Adhesive tape for semiconductor wafer surface protection - Google Patents

Description

  The present invention relates to an adhesive tape for protecting a semiconductor wafer surface. More specifically, for protecting the surface of a semiconductor wafer that is used to grind the back surface of a semiconductor wafer that is bonded to the surface of the semiconductor wafer after being condensed inside the semiconductor wafer using a laser to form a modified layer therein. It relates to an adhesive tape.

  A semiconductor package is manufactured by slicing a high-purity silicon single crystal or the like into a semiconductor wafer, and then forming an integrated circuit on the wafer surface by ion implantation, etching, or the like. By grinding the back surface of the semiconductor wafer on which the integrated circuit is formed, the semiconductor wafer has a desired thickness. At this time, in order to protect the integrated circuit formed on the surface of the semiconductor wafer, an adhesive tape for protecting the surface of the semiconductor wafer is used. The back-ground semiconductor wafer is stored in a wafer cassette after the back-side grinding is completed, transported to a dicing process, and processed into semiconductor chips. The adhesive tape for semiconductor wafer surface protection is generally formed by laminating an adhesive layer on a base film, and the adhesive layer is attached to the back surface of the semiconductor wafer. Is completed, the wafer is peeled off from the wafer surface.

  Conventionally, as an important performance required for an adhesive tape for protecting a semiconductor wafer surface, there is a precision (TTV) of a finished thickness of a semiconductor wafer after grinding. The accuracy (TTV) of the finished thickness of the semiconductor wafer leads to an improvement in processing quality, and is required from the viewpoint of the yield of semiconductor chips and operational reliability. In general, the surface of a semiconductor wafer has unevenness caused by an integrated circuit device incorporated or a protective film formed on the integrated circuit. Some have improved the followability to the unevenness of the adhesive tape for protecting the front surface of the semiconductor wafer in order to improve the TTV by reducing the grinding stress when grinding the back surface to prevent the wafer from being damaged.

  As described above, when the semiconductor wafer is diced after grinding the back surface of the semiconductor wafer, the surface of the semiconductor wafer is infiltrated with cutting water or dust (slurry) even with a conventional semiconductor wafer surface protective adhesive tape. It was possible to protect the semiconductor wafer from intrusion, the semiconductor wafer could be prevented from being damaged, and there was no problem with the accuracy of the TTV.

  However, in recent years, the spread of IC cards has progressed, and it is desired to reduce the thickness of chips. For this reason, it is necessary to reduce the thickness of a semiconductor chip, which has conventionally been about 350 μm, to a thickness of 50 to 100 μm or less. In order to achieve such thinning of the chip, a new semiconductor wafer cutting method has been proposed. First, after a groove having a predetermined depth is formed from the front side of the semiconductor wafer using a blade, a chip is manufactured by grinding it from the back side using an adhesive tape for protecting the surface of the semiconductor wafer. (For example, refer to Patent Document 1).

  When such a semiconductor wafer cutting method is used, the adhesive tape for surface protection of semiconductor wafers that has been widely used in the past has used a relatively soft adhesive layer. It was easy to do. In order to solve the problem, it has been proposed to reduce chip cracks that occur during back grinding by specifying the compression strain of the adhesive tape for protecting the surface of a semiconductor wafer and the elastic modulus of the adhesive layer (for example, patents). Reference 2).

  Furthermore, instead of forming the groove by the blade described above, a modified layer is formed inside by condensing the laser inside the wafer, and then the semiconductor wafer is attached to the back surface using an adhesive tape for protecting the semiconductor wafer surface. A dicing method has been proposed in which a semiconductor wafer is thinned by grinding from the side, and then a dicing tape is applied and stretched to divide the chip into chips (see, for example, Patent Document 3). By using this dicing method, the width of the groove becomes narrower than dicing with a blade, so that the number of chips manufactured from one semiconductor wafer is improved.

JP-A-5-335411 Japanese Patent No. 3410371 JP2012-124300A

  However, when the semiconductor wafer surface protecting adhesive tape described in Patent Document 2 is used for grinding the back surface of the semiconductor wafer by the laser dicing method, the chip is damaged because it does not follow the irregularities on the wafer surface. There was a thing. Further, since the dicing method using the laser is in a very narrow state between the chips as compared with the dicing method using the blade, more followability to the device step on the chip is required. When the semiconductor wafer surface protective adhesive tape described in Patent Document 2 is used for grinding the back surface of the semiconductor wafer by the laser dicing method, the followability to the device step is not sufficient, and the semiconductor wafer surface protective adhesive tape Since there is a gap between the semiconductor wafer and the semiconductor wafer, the cutting water is cut into the gap between the semiconductor wafer surface protecting adhesive tape and the semiconductor wafer from between the chips separated by the laser modified region during back grinding. And there was a problem that dust invades and TTV deteriorates.

  On the other hand, when the adhesive layer or the base film is made soft in order to improve the followability of the semiconductor wafer surface protection adhesive tape to the unevenness of the semiconductor wafer surface (circuit surface), the chip pressed by the backside polishing device sinks. Since there is a step between the chip that is not pressed and the chip that is not pressed, a gap is generated between the chip that is not pressed by the back surface polishing apparatus and the adhesive tape for protecting the semiconductor wafer surface, and cutting water enters and chip peeling or TTV occurs. Deterioration occurs. If the pressure-sensitive adhesive layer or the base film is soft, the chip in the portion pressed by the back surface polishing device also moves due to the pressure in the grinding rotation direction, and there is a gap between the chip and the adhesive tape for protecting the semiconductor wafer surface. And cutting water enters and chip peeling and TTV deterioration occur.

  Also, when grinding the backside of the semiconductor wafer and dividing it into chips, the stress of the semiconductor wafer surface protection adhesive tape is weak against the grinding force, reducing the semiconductor chip to the semiconductor wafer surface protection adhesive tape. There was a problem that TTV deteriorated.

  Therefore, the present invention reduces damage to a semiconductor wafer or chip even if the back surface of the semiconductor wafer is ground after the laser beam is focused inside the semiconductor wafer to form a modified layer inside the semiconductor wafer. It is an object of the present invention to provide an adhesive tape for protecting the surface of a semiconductor wafer, which can be ground with high thickness accuracy (TTV).

  In order to solve the above-mentioned problems, the adhesive tape for protecting the surface of a semiconductor wafer according to the present invention polishes the back surface of the semiconductor wafer having a modified region formed therein by being focused on a laser beam and irradiated with a laser. A semiconductor wafer surface protecting pressure-sensitive adhesive tape that is bonded to the surface of the semiconductor wafer on which the circuit pattern is formed and is used to protect the surface of the semiconductor wafer, the pressure-sensitive adhesive on at least one side of the base film A layer having an elastic modulus of 75 MPa or more and a stress relaxation rate of 10 to 18% or less.

  The pressure-sensitive adhesive tape for protecting a semiconductor wafer surface is a radiation-curable pressure-sensitive adhesive layer in which the pressure-sensitive adhesive layer is cured by irradiating radiation, and the adhesive strength at 25 ° before radiation irradiation to stainless steel is 3. It is 0 N / 25mm-20.0N / 25mm, and it is preferable that the adhesive force in 25 degreeC after irradiation of the radiation of the irradiation amount 500mJ is 0.01N / 25mm-2.0N / 25mm.

  Moreover, it is preferable that the contact angle with respect to the pure water of the adhesive layer surface of the adhesive layer is 85 degrees or more as for the adhesive tape for semiconductor wafer surface protections.

  In the semiconductor wafer surface protecting pressure-sensitive adhesive tape, the main component polymer constituting the pressure-sensitive adhesive is preferably a (meth) acrylic polymer.

Moreover, it is preferable that the said adhesive tape for surface protection of a semiconductor wafer has the storage elastic modulus in 25 degreeC before the radiation irradiation of the said adhesive layer at 7 * 10 < ⁴ > Pa or more, and a loss tangent is 0.20 or less.

Further, the adhesive tape for protecting a semiconductor wafer surface has a tack force change rate calculated by the following formula (1) of 30% or more before and after the pressure-sensitive adhesive layer irradiates radiation with an irradiation amount of 500 mJ. An adhesive tape for protecting a semiconductor wafer surface.
[Tα−Tβ (air)] ÷ [Tα−Tβ (N ₂ )] × 100 (%) (1)
(In the formula, Tα represents a measured value of tack force before irradiation, Tβ (air) represents a measured value of tack force after irradiation with an irradiation amount of 500 mJ in the presence of oxygen, and Tβ (N ₂ ) represents nitrogen. (A measured value of tack force after irradiation with an irradiation amount of 500 mJ in an atmosphere.)

  According to the present invention, damage to a semiconductor wafer or chip can be reduced due to adhesion and moderate stress relaxation. In addition, according to the present invention, it is possible to prevent the intrusion of dust and grinding water since the followability to the unevenness of the semiconductor wafer surface (circuit surface) is good. Furthermore, since the stress is not relaxed more than necessary, the semiconductor wafer is not excessively reduced to the adhesive tape for protecting the surface of the semiconductor wafer due to the force applied when grinding the back surface of the semiconductor wafer. Grinding with TTV).

It is sectional drawing which shows typically the structure of the adhesive tape for semiconductor wafer surface protection which concerns on embodiment of this invention. It is sectional drawing which shows typically the back grinding process using the adhesive tape for semiconductor wafer surface protection which concerns on embodiment of this invention. It is sectional drawing which shows typically the back grinding process using the adhesive tape for semiconductor wafer surface protection which concerns on embodiment of this invention. It is sectional drawing which shows typically the dicing process after the back grinding process using the adhesive tape for surface protection of the semiconductor wafer which concerns on embodiment of this invention. It is sectional drawing which shows typically the dicing process after the back grinding process using the adhesive tape for surface protection of the semiconductor wafer which concerns on embodiment of this invention. It is sectional drawing which shows typically the expansion process after the back grinding process using the adhesive tape for semiconductor wafer surface protection which concerns on embodiment of this invention. It is sectional drawing which shows typically the pick-up process after the back grinding process using the adhesive tape for semiconductor wafer surface protection which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  As shown in FIG. 1, the adhesive layer 1 for protecting a semiconductor surface according to an embodiment of the present invention has at least one adhesive applied to at least one surface of a base film 2 to form an adhesive layer 3. ing. Hereafter, each component of the adhesive tape 1 for semiconductor wafer surface protection of this embodiment is demonstrated in detail.

(Base film 2)
The base film 2 is not particularly limited as long as the elastic modulus of the entire semiconductor wafer surface protecting adhesive tape 1 is 75 MPa or more and the stress relaxation rate is 10 to 18% or less. Polyolefins such as polyethylene, polypropylene and polybutene; ethylene copolymers such as ethylene-vinyl acetate copolymers, ethylene- (meth) acrylic acid copolymers and ethylene- (meth) acrylic acid ester copolymers. Polymer: Polymer materials such as soft polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, semi-rigid polyvinyl chloride, polyester, polyurethane, polyamide, polyimide, natural rubber and synthetic rubber, or two or more selected from these groups Mixed or multi-layered Arbitrariness. In particular, in the present invention, an ethylene-vinyl acetate copolymer is preferable because the elastic modulus can be arbitrarily controlled by changing the content of vinyl acetate. 10-500 micrometers is preferable and, as for the thickness of a base film, 50-200 micrometers is more preferable.

(Adhesive layer 3)
The pressure-sensitive adhesive layer 3 is preferably a radiation curable type that cures when irradiated with radiation. The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer is such that the elastic modulus of the semiconductor wafer surface protective pressure-sensitive adhesive tape 1 is 75 MPa or more and the stress relaxation rate of the semiconductor wafer surface protective pressure-sensitive adhesive tape 1 is 10 to 18%. If there is, it will not be specifically limited.

  The pressure-sensitive adhesive composition constituting the radiation-curable pressure-sensitive adhesive layer 3 is a combination of a pressure-sensitive adhesive polymer and a radiation polymerizable compound, or a functional group that is polymerized by radiation in the polymer constituting the pressure-sensitive adhesive (preferably Can be used polymers incorporating ethylenically unsaturated groups). In order to promote polymerization with radiation, it is preferable to include a photopolymerization initiator. It is also preferable to contain a crosslinking agent. Film hardness and gel fraction can be adjusted by incorporating a monomer having a functional group capable of reacting with a crosslinking agent into the polymer constituting the pressure-sensitive adhesive. Furthermore, additives and additives other than those described above can be included as necessary.

  The main component polymer (adhesive polymer, also called base polymer) that constitutes the adhesive is made up of various types of polymers such as (meth) acrylic resins, epoxy resins, natural rubber resins, synthetic rubber resins, etc. Among them, a (meth) acrylic resin is preferable. The (meth) acrylic resin is easy to control the adhesive force.

  In the present invention, the main component of the pressure-sensitive adhesive layer is preferably a (meth) acrylic copolymer resin. By using (meth) acrylic resin, the adhesive force can be easily controlled and the gel fraction and the like can be controlled. Therefore, the adhesive residue remains on the surface of the semiconductor wafer, and so-called adhesive residue and organic contamination are reduced. can do. When the polymer is a (meth) acrylic resin, the main monomer constituting the polymer is preferably a (meth) acrylic acid alkyl ester or a monomer mixture of two or more different (meth) acrylic acid alkyl esters.

  Specific examples of alkyl esters of (meth) acrylic acid include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, Examples thereof include isoamyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and isodecyl (meth) acrylate. These may be used singly or in combination of two or more.

In the present invention, it is preferable to use a mixture of two or more types, and by mixing two or more types, various functions as an adhesive can be exhibited. More preferably, 3 or more types are mixed, methyl (meth) acrylate, butyl acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, (meth) It is particularly preferable to copolymerize at least three, preferably at least four selected from glycidyl acrylate and 2-isocyanatoethyl (meth) acrylate described below. By copolymerizing three or more types of monomers, it becomes possible to achieve both adhesion to the step and non-contamination including adhesive residue.
In the present invention, in addition to the above, it is preferable to use a monomer component having a polymerizable group, a polyfunctional monomer, and a monomer component having a functional group capable of reacting with a crosslinking agent.

  Examples of the monomer for reacting with radiation (preferably ultraviolet rays) include (meth) acrylic acid ester having an isocyanate (—N═C═O) group in the alcohol portion, and among them, isocyanate (—N═C═O). (Meth) acrylic acid alkyl esters substituted with groups are preferred. Examples of such a monomer include 2-isocyanatoethyl methacrylate and 2-isocyanatoethyl acrylate. As appropriate, these can be added to the acrylic polymer copolymer and reacted with the hydroxyl group of the side chain of the acrylic polymer copolymer to incorporate a polymerizable group into the copolymer, thereby reducing the adhesive strength after irradiation. Can do.

The content of the monomer that reacts with radiation (preferably ultraviolet rays) in the polymer is preferably 30 to 90% by mass, more preferably 40 to 80% by mass with respect to 100% by mass of the polymer.
In addition, incorporation of a monomer that reacts with radiation (preferably ultraviolet rays) into a polymer reacts with this functional group after synthesizing a polymer having a functional group such as a hydroxyl group, a carboxyl group, an epoxy group, or an amino group in the side chain. It can be obtained by adding a monomer that reacts with radiation having a functional group (preferably ultraviolet rays) and reacting it.

  The polymer contained in the pressure-sensitive adhesive may have a functional group that can react with the crosslinking agent, and examples of the functional group that can react with the crosslinking agent include a hydroxyl group, a carboxyl group, an epoxy group, and an amino group. As a method for introducing functional groups capable of reacting with these crosslinking agents into the pressure-sensitive adhesive polymer, a method of copolymerizing monomers having these functional groups when polymerizing the polymer is generally used.

Moreover, in order to adjust the gel fraction of the pressure-sensitive adhesive layer, a polyfunctional monomer component can be copolymerized when the polymer contained in the pressure-sensitive adhesive is polymerized.
Examples of the functional group of these polyfunctional monomer components include (meth) acryloyl group, vinyl group, and allyl group.

Examples of the polyfunctional monomer include diethylene glycol diacrylate, diethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1 , 6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate Jibi Such as Rubenzen can be mentioned up.

These polyfunctional monomers are preferably used as a radiation-polymerizable compound contained in combination with the pressure-sensitive adhesive polymer, in addition to being incorporated as a polymer component contained in the pressure-sensitive adhesive.
In this case, the pressure-sensitive adhesive polymer may or may not have a radiation polymerizable group.
When used as a radiation-polymerizable compound contained in combination with a pressure-sensitive adhesive polymer, the amount of the radiation-polymerizable compound is preferably 30 to 200 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive polymer of the base polymer. 150 parts by mass is more preferable.

  As the pressure-sensitive adhesive constituting the radiation curable pressure-sensitive adhesive layer 3, for example, those described in JP-B-1-56112, JP-A-7-135189 and the like are preferably used, but are not limited thereto. Absent.

It is preferable that the pressure-sensitive adhesive contains a photopolymerization initiator because a curing reaction by radiation irradiation can be efficiently performed.
As photopolymerization initiators, 4,4′-bis (diethylamino) benzophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy- 1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl]- 2-hydroxy-2-methyl-1-propan-1-one and the like can be mentioned.
1-10 mass parts is preferable with respect to 100 mass parts of base polymers, and, as for the compounding quantity of a photoinitiator, 2-5 mass parts is more preferable.

In order to add cohesive force to the base polymer, a crosslinking agent can be blended.
In particular, when the base polymer is a (meth) acrylic resin, the adhesive force is controlled by blending a curing agent. A predetermined adhesive force can be obtained by adjusting the number of parts of the curing agent.
Examples of such a crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, an aziridine crosslinking agent, and an amine resin.
1-10 mass parts is preferable with respect to 100 mass parts of base polymers, and, as for the compounding quantity of a crosslinking agent, 3-5 mass parts is more preferable.

  Further, the pressure-sensitive adhesive can contain various additive components as desired within the range in which the object of the present invention is not impaired. The pressure-sensitive adhesive may be an adhesive that can be used for dicing and dyne bonding.

  The pressure-sensitive adhesive layer 3 can be formed by applying the pressure-sensitive adhesive composition as described above onto the base film 2 and drying it. The thickness of the pressure-sensitive adhesive layer 3 is preferably 5 to 30 μm.

  The pressure-sensitive adhesive layer 3 may have a configuration in which a plurality of layers are laminated. In the case of having a plurality of layers, at least the layer in contact with the semiconductor wafer uses the above-mentioned radiation curable pressure-sensitive adhesive, but at least the layer other than the layer in contact with the semiconductor wafer also uses a heat-foaming pressure-sensitive adhesive. it can. The radiation-curing pressure-sensitive adhesive is cured by ultraviolet rays, electron beams or the like, and is easily peeled off at the time of peeling. The heat-foaming pressure-sensitive adhesive is easily peeled off by a foaming agent or an expansion agent. Moreover, you may provide intermediate | middle layers, such as a primer layer, between the base film 2 and the adhesive layer 3 as needed.

  Moreover, you may affix the release film 4 (refer FIG. 1) normally used as a separator in order to protect an adhesive layer to the adhesive layer 3 side until it uses for practical use as needed. Examples of the constituent material of the release film 4 include synthetic resin films such as polyethylene, polypropylene, and polyethylene terephthalate, and paper. The surface of the synthetic resin film may be subjected to a release treatment such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc., if necessary, in order to enhance the peelability from the pressure-sensitive adhesive layer. The release film 4 has a thickness of usually 10 to 100 μm, preferably about 25 to 50 μm.

  The adhesive tape 1 for protecting a semiconductor wafer surface of the present embodiment has an elastic modulus of 75 MPa or more, preferably 90 MPa or more, and more preferably 110 MPa or more. The elastic modulus here is the behavior of the force applied during pulling, and the measurement can be performed using a commercially available “strograph”. If the elastic modulus is less than 75 MPa, the adhesive tape 1 for protecting the surface of the semiconductor wafer is soft, so that the semiconductor wafer fluctuates when the back surface of the semiconductor wafer is ground, and the semiconductor wafer cracks (that is, the grindability is poor). ) Or TTV may get worse.

The stress relaxation rate of the adhesive tape 1 for protecting a semiconductor wafer surface of the present embodiment is 10 to 18%, preferably 12 to 15%. In the present invention, the stress relaxation rate of the adhesive tape 1 for protecting a semiconductor wafer surface means a ratio of a reduced stress to an initial stress value. Specifically, this stress relaxation rate is obtained by placing a test piece having a width of 25 mm and a length of 65 mm on a compression parallel plate, bringing a bending indenter into contact with the thickness of the test piece, and compressing at a speed of 1.0 mm / min. Then, the stress obtained when a load is applied up to a stress of 50N and the displacement at the time of the stress of 50N is held for 3 minutes is measured and calculated by the following equation (2). In the formula (2), F ₀ is an initial compressive stress, and is 50 N in the present invention. F _(t) is the compressive stress after elapse of time t, and in the present invention, it is the compressive stress after elapse of 3 minutes. In addition, this stress relaxation measurement can be measured using, for example, a tensile tester (Twin Column Tabletop Model 5567) manufactured by Instron.

  When the stress relaxation rate of the pressure-sensitive adhesive tape 1 for protecting the semiconductor wafer surface is less than 10%, the followability of the pressure-sensitive adhesive layer with respect to the step difference on the surface of the semiconductor wafer is deteriorated. Deterioration of accuracy (TTV) is caused. On the other hand, if it exceeds 18%, the followability of the pressure-sensitive adhesive layer to the step difference on the surface of the semiconductor wafer is good, but the force applied to the semiconductor wafer during grinding is released, the semiconductor wafer is damaged, and the thickness accuracy (TTV) deteriorates. May end up.

In order for the elastic modulus of the adhesive tape 1 for protecting the semiconductor wafer surface to be 75 MPa or more and the stress relaxation rate to be 10 to 18%, the base film 2 is made of polyethylene terephthalate (PET) film or ethylene-vinyl acetate. A polymer (EVA) film is used. As an adhesive, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methacrylic acid, 2-isocyanatoethyl methacrylate, adduct isocyanate crosslinking agent, photoinitiator 4,4′-bis (diethylamino) benzophenone, etc. are added. .
Specifically, when the base film 2 is a polyethylene terephthalate (PET) film, if the monomer 100 has a long side chain such as 2-ethylhexyl acrylate as parts by weight, the monomer having a hydroxyl group is 30 to 50, methacryl An acid is added in 2 to 3, and an adduct isocyanate cross-linking agent is appropriately blended between 1 to 3, and a copolymer 100 obtained by copolymerization with 40-isocyanatoethyl methacrylate. It can be obtained by adding ~ 80.

  Further, for a copolymer composed of 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, methacrylic acid, 2-isocyanatoethyl methacrylate, adduct isocyanate crosslinking agent Coronate L, photoinitiator 4,4′-bis ( When a pressure-sensitive adhesive containing diethylamino) benzophenone is used, the base film 2 can be obtained by setting the vinyl acetate content to 7% or less if it is an ethylene-vinyl acetate copolymer (EVA) film.

The pressure-sensitive adhesive layer 3 preferably has a storage elastic modulus at 25 ° C. before radiation irradiation of 7 × 10 ⁴ Pa or more and a loss tangent of 0.20 or less. When the storage elastic modulus is less than 7 × 10 ⁴ Pa at 25 ° C., the stress is easily relaxed and may exceed the range of 10 to 18%. Further, the above range is preferable because the loss tangent may be the same even if it exceeds 0.20.

In order to make the storage elastic modulus at 25 ° C. before radiation irradiation of the pressure-sensitive adhesive layer 3 be 7 × 10 ⁴ Pa or more, for example, when the monomer is a monomer 100 having a long side chain such as 2-ethylhexyl acrylate as a mass part. The monomer having a hydroxyl group is added in an amount of 30 to 50, methacrylic acid is added in an amount of 2 to 3, and 1 part or more of an adduct isocyanate crosslinking agent is blended and copolymerized. It is good to add 40-80 of isocyanatoethyl methacrylate. In order to make the loss tangent 0.20 or less, for example, when the monomer 100 having a long side chain such as 2-ethylhexyl acrylate is used as the weight part, the monomer having a hydroxyl group is 30 to 50, and methacrylic acid. It is good to add 40-80 of 2-isocyanatoethyl methacrylate with respect to the copolymer 100 obtained by adding and adding 1 part or more of adduct type isocyanate type crosslinking agents at 10 or less, and copolymerizing.

  The adhesive tape 1 for protecting a semiconductor wafer surface of this embodiment has an adhesive strength at 25 ° C. to stainless steel (Steel Use Stainless, SUS) of 3.0 N / 25 mm to 20.0 N / 25 mm, and a radiation dose of 500 mJ. It is preferable that the adhesive force in 25 degreeC after irradiation is 0.01N / 25mm-2.0N / 25mm. The adhesive strength before irradiation is preferably 3.0 N / 25 mm to 17.0 N / 25 mm, and the adhesive strength after irradiation is preferably 0.01 N / 25 mm to 1.2 N / 25 mm.

  When the adhesive strength before radiation irradiation is less than 3.0 N / 25 mm, when the semiconductor wafer surface protective adhesive tape 1 is bonded and the back surface of the semiconductor wafer is ground, due to insufficient adhesion with the periphery of the semiconductor wafer, Contamination such as seapage may be caused and the semiconductor wafer may be damaged. Conversely, if it exceeds 20.0 N / 25 mm, the adhesive strength after irradiation with an irradiation dose of 500 mJ does not decrease to 2.0 N / 25 mm. As a result, not only peeling after curing becomes heavy, but also a residue of adhesive remains on the surface of the semiconductor wafer. Moreover, in order to make the adhesive force after radiation irradiation 2.0N / 25mm or less when exceeding 20.0N / 25mm, the quantity of the double bond which exists in an adhesive, and a photoinitiator are required many. Therefore, the curing shrinkage after irradiation is strong, and the semiconductor wafer surface is likely to bite into the irregularities, which also causes peeling failure and adhesive residue.

  The adhesive strength before irradiation can be adjusted by the ratio of hydroxyl group, acid group, and amount of curing agent, and the adhesive strength after irradiation by adjusting the amount of double bonds or the amount of photopolymerization initiator in the adhesive. It can be carried out. The adhesive strength at 25 ° C. to stainless steel (SUS) is 3.0 N / 25 mm to 20.0 N / 25 mm, and the adhesive strength at 25 ° C. after irradiation with radiation of 500 mJ is 0.01 N / In order to make it 25 mm to 2.0 N / 25 mm, for example, if the monomer has a long side chain such as 2-ethylhexyl acrylate as the mass part, the methacrylic acid is 10 parts by mass or less, and the curing agent is 1 to 10 parts and the amount of double bonds may be suitably blended at 30 parts by mass or more with respect to 100 parts by mass of the copolymer.

The adhesive strength to stainless steel (SUS # 280) can be measured using a tensile tester.
Specifically, a test piece having a width of 25 mm and a length of 150 mm was taken from the adhesive tape, and the thickness of the sample specified in JIS G 4305 finished with No. 280 water-resistant abrasive paper specified in JIS R 6253 is as follows. Using a tensile tester conforming to JIS B 7721 where a 2 kg rubber roller is reciprocated three times on a 5 mm to 2.0 mm SUS steel plate, left for 1 hour, and the measured value falls within the range of 15 to 85% of its capacity. Then, it is measured at room temperature (25 ° C.) by a 90 ° peeling method at a tensile speed of 50 mm / min. Further, the adhesive strength after radiation irradiation is measured in the same manner as described above after the adhesive tape having the radiation curable pressure-sensitive adhesive layer is cured by irradiating with 500 mJ ultraviolet rays.

  The pressure-sensitive adhesive layer 3 of the semiconductor wafer surface protecting pressure-sensitive adhesive tape 1 of the present embodiment preferably has a surface contact angle φ of 85 ° or more with respect to pure water. If the value of the contact angle φ is less than 85 °, the hydrophilicity becomes high. Therefore, a large amount of cutting water used for back surface grinding and chip cutting is used to protect the semiconductor wafer surface with grinding water containing silicon grinding debris. In some cases, so-called seapage, which contaminates the wafer circuit surface, easily occurs through the gap between the adhesive tape 1 and the semiconductor wafer.

  The contact angle φ with respect to pure water can be 85 ° or more by adjusting the molecular weight of the polymer copolymer, the steric structure of the side chain, the ratio of hydroxyl groups and acid groups.

The adhesive layer 3 of the semiconductor wafer surface protecting adhesive tape 1 of this embodiment has a tack force change rate of 30% or more determined by the following formula (1) before and after irradiation with an irradiation dose of 500 mJ. Is preferred.
[Tα−Tβ (air)] ÷ [Tα−Tβ (N ₂ )] × 100 (%) (1)
In the formula, Tα represents a measured value of tack force before irradiation, Tβ (air) represents a measured value of tack force after irradiation with an irradiation amount of 500 mJ in the presence of oxygen, and Tβ (N ₂ ) represents a nitrogen atmosphere. It represents a measured value of tack force after irradiation with a lower irradiation dose of 500 mJ.

  When the rate of change of tack force obtained by formula (1) is less than 30%, the surface state of the radiation-curing pressure-sensitive adhesive layer on the surface in contact with the semiconductor wafer is almost unchanged from that before irradiation with radiation (ultraviolet rays). For this reason, peeling is heavy and adhesive residue is also caused. By setting the rate of change of tack force to 30% or more, peeling is reduced and adhesive residue can be suppressed.

  In order to make the change rate of the tack force calculated by the formula (1) to be 30% or more, the molecular weight of the polymer copolymer and the three-dimensional structure of the side chain, the ratio of hydroxyl groups and acid groups, or the curing agent are adjusted. Can be done.

<How to use>
Next, the usage method of the adhesive tape 1 for semiconductor wafer surface protection of this invention is demonstrated.

  First, as shown in FIG. 2, the adhesive layer 3 of the semiconductor wafer surface protecting adhesive tape 1 from which the release film 4 has been peeled is bonded to the surface of the semiconductor wafer 5 on which the circuit pattern is formed. The modified region 7 is formed inside the semiconductor wafer 5 by irradiating the laser with the focusing point inside the semiconductor wafer 5 from the back surface side.

  The thickness of the pressure-sensitive adhesive layer 3 of the semiconductor wafer surface protecting pressure-sensitive adhesive tape 1 used for protecting the surface of the semiconductor wafer 5 is preferably used according to the height of the surface irregularities of the semiconductor wafer 5 to be protected. It is preferable to use a pressure-sensitive adhesive tape 1 for protecting a semiconductor wafer surface having a pressure-sensitive adhesive layer 3 thinner than the surface unevenness height of 5.

  Next, as shown in FIG. 3B, the semiconductor wafer 5 on which the modified region 7 is formed is modified by a back grinding process in which the back surface is ground by the grinding device 8 as shown in FIG. Grind until the region 7 is reached. A normal back grinding process can be applied except that the semiconductor wafer surface protecting adhesive tape is used in consideration of the relationship between the semiconductor wafer surface protecting adhesive tape and the surface irregularities of the semiconductor wafer to be protected.

  After the back grinding process is completed, the dicing tape 6 is bonded to the back surface of the semiconductor wafer 5 and the ring frame 9 is bonded to the outer peripheral portion of the pressure-sensitive adhesive layer 3 as shown in FIG. Thereafter, as shown in FIG. 5, the semiconductor wafer surface protecting adhesive tape 1 is peeled off.

  Thereafter, for example, as shown in FIG. 6, the dicing tape 6 on which the semiconductor wafer 5 and the ring frame 9 are bonded is placed on the stage (not shown) of the expanding apparatus, and the ring frame 9 is fixed. The push-up member 10 of the expanding device is raised and the dicing tape 6 is expanded. As the dicing tape 6 is stretched in the circumferential direction in this way, the semiconductor wafer 5 is divided into chips 11 starting from the modified region 7.

  Then, as shown in FIG. 7, the semiconductor chip 11 can be obtained by pushing up the chip 11 from the back surface side of the dicing tape 6 with the push-up pin 12 and attracting and picking it up with the collet 13.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

<Example 1>
70 mass parts 2-ethylhexyl acrylate, 28 mass parts 2-hydroxyethyl acrylate, 5 mass parts methacrylic acid, a copolymer having a weight average molecular weight of 900,000 obtained by polymerization in ethyl acetate 60 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass to obtain an acrylic copolymer. 2 parts by mass of adduct isocyanate crosslinking agent Coronate L (trade name, manufactured by Nippon Polyurethane) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are blended into the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. An adhesive tape for protecting the surface of a semiconductor wafer according to Example 1 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Example 2>
25 parts by weight of ethyl acrylate, 35 parts by weight of 2-hydroxyethyl acrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of a copolymer having a weight average molecular weight of 450,000 obtained by polymerization in ethyl acetate 40 parts by mass of 2-isocyanatoethyl methacrylate was added to the part to obtain an acrylic copolymer. 5 parts by mass of adduct isocyanate crosslinker Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are blended into the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. An adhesive tape for protecting the surface of a semiconductor wafer according to Example 2 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Example 3>
40 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of butyl acrylate, 25 parts by mass of 2-hydroxyethyl acrylate, 10 parts by mass of methacrylic acid, and a weight average obtained by copolymerization in ethyl acetate 70 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass of a copolymer having a molecular weight of 400,000 to obtain an acrylic copolymer. 1 part by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photopolymerization initiator 4,4′-bis (diethylamino) benzophenone are blended into the polymerized acrylic copolymer. The pressure-sensitive adhesive composition was obtained by adjusting with ethyl acetate to adjust the viscosity to be easy to apply. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. A semiconductor wafer surface protecting pressure-sensitive adhesive tape according to Example 3 was produced by laminating by bonding onto a PET film.

<Example 4>
60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of 2-hydroxyethyl acrylate, 2 parts by mass of methacrylic acid, a copolymer having a weight average molecular weight of 800,000 obtained by polymerization in ethyl acetate 60 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass to obtain an acrylic copolymer. 4 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are added to the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. An adhesive tape for protecting the surface of a semiconductor wafer according to Example 4 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Example 5>
10 parts by mass of 2-ethylhexyl acrylate, 25 parts by mass of ethyl acrylate, 40 parts by mass of 2-hydroxyethyl acrylate, 10 parts by mass of methacrylic acid, and a weight average obtained by copolymerization in ethyl acetate 50 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass of the copolymer having a molecular weight of 650,000 to obtain an acrylic copolymer. 2 parts by mass of adduct isocyanate crosslinking agent Coronate L (trade name, manufactured by Nippon Polyurethane) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are blended into the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a polyethylene terephthalate (PET) separator having a thickness of 25 μm as a release film so that the film thickness after drying was 40 μm and dried, and then a substrate film having a thickness of 100 μm was formed. The adhesive tape for surface protection of a semiconductor wafer according to Example 5 was manufactured by laminating by bonding onto a PET film.

<Example 6>
70 parts by weight of ethyl acrylate, 20 parts by weight of 2-hydroxyethyl acrylate, 5 parts by weight of methacrylic acid, and 100 parts by weight of a copolymer having a weight average molecular weight of 200,000 obtained by polymerization in ethyl acetate. 30 parts by mass of 2-isocyanatoethyl methacrylate was added to the part to obtain an acrylic copolymer. 1.5 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photopolymerization initiator 4,4′-bis (diethylamino) benzophenone on the polymerized acrylic copolymer The pressure-sensitive adhesive composition was obtained by adjusting with ethyl acetate to adjust the viscosity to be blended and easy to apply. A pressure-sensitive adhesive composition was applied on a polyethylene terephthalate (PET) separator having a thickness of 25 μm as a release film so that the film thickness after drying was 40 μm and dried, and then a substrate film having a thickness of 100 μm was formed. An adhesive tape for protecting the surface of a semiconductor wafer according to Example 6 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Example 7>
30 parts by mass of ethyl acrylate, 30 parts by mass of 2-hydroxyethyl acrylate, 20 parts by mass of methacrylic acid, and 100% by mass of a copolymer having a weight average molecular weight of 350,000 obtained by polymerization in ethyl acetate. 70 parts by mass of 2-isocyanatoethyl methacrylate was added to the part to obtain an acrylic copolymer. 4 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are added to the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a polyethylene terephthalate (PET) separator having a thickness of 25 μm as a release film so that the film thickness after drying was 40 μm and dried, and then a substrate film having a thickness of 100 μm was formed. An adhesive tape for protecting the surface of a semiconductor wafer according to Example 7 was produced by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Example 8>
60 mass parts 2-ethylhexyl acrylate, 30 mass parts 2-hydroxyethyl acrylate, 5 mass parts methacrylic acid, a copolymer having a weight average molecular weight of 700,000 obtained by polymerization in ethyl acetate 60 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass to obtain an acrylic copolymer. 1.5 parts by weight of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane) and 2 parts by weight of photoinitiator 4,4′-bis (diethylamino) benzophenone are added to the polymerized acrylic copolymer. And in order to adjust to the viscosity which is easy to apply, it adjusted with ethyl acetate and obtained the adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. A semiconductor wafer surface protecting pressure-sensitive adhesive tape according to Example 8 was produced by laminating by bonding onto a PET film.

<Example 9>
60 parts by weight of butyl acrylate, 30 parts by weight of 2-hydroxyethyl acrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of a copolymer having a weight average molecular weight of 700,000 obtained by polymerization in ethyl acetate 30 parts by mass of 2-isocyanatoethyl methacrylate was added to the part to obtain an acrylic copolymer. 1.5 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photopolymerization initiator 4,4′-bis (diethylamino) benzophenone on the polymerized acrylic copolymer The pressure-sensitive adhesive composition was obtained by adjusting with ethyl acetate to adjust the viscosity to be blended and easy to apply. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. A semiconductor wafer surface protecting pressure-sensitive adhesive tape according to Example 9 was produced by laminating by bonding onto a PET film.

<Example 10>
50 parts by weight of ethyl acrylate, 40 parts by weight of 2-hydroxyethyl acrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of a copolymer having a weight average molecular weight of 400,000 obtained by polymerization in ethyl acetate 60 parts by mass of 2-isocyanatoethyl methacrylate was added to the part to obtain an acrylic copolymer. 8 parts by mass of adduct isocyanate crosslinker Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are blended into the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. The adhesive tape for semiconductor wafer surface protection which concerns on Example 10 was produced by laminating by bonding on a PET film.

<Comparative Example 1>
60 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of 2-hydroxyethyl acrylate, 5 parts by mass of methacrylic acid, a copolymer having a weight average molecular weight of 1,000,000 obtained by polymerization in ethyl acetate 60 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass to obtain an acrylic copolymer. The polymerized acrylic copolymer contains 2.5 parts by weight of adduct isocyanate crosslinking agent Coronate L (trade name, manufactured by Nippon Polyurethane) and 2 parts by weight of photoinitiator 4,4'-bis (diethylamino) benzophenone. And in order to adjust to the viscosity which is easy to apply, it adjusted with ethyl acetate and obtained the adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. An adhesive tape for protecting the surface of a semiconductor wafer according to Comparative Example 1 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Comparative example 2>
90 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of 2-hydroxyethyl acrylate, 2 parts by weight of methacrylic acid, a copolymer having a weight average molecular weight of 500,000 obtained by polymerization in ethyl acetate 50 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass to obtain an acrylic copolymer. 0.5 parts by mass of adduct isocyanate crosslinking agent Coronate L (trade name, manufactured by Nippon Polyurethane) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are added to the polymerized acrylic copolymer. And in order to adjust to the viscosity which is easy to apply, it adjusted with ethyl acetate and obtained the adhesive composition. A pressure-sensitive adhesive composition was applied on a polyethylene terephthalate (PET) separator having a thickness of 25 μm as a release film so that the film thickness after drying was 40 μm and dried, and then a substrate film having a thickness of 100 μm was formed. An adhesive tape for protecting the surface of a semiconductor wafer according to Comparative Example 2 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Comparative Example 3>
20 parts by mass of 2-ethylhexyl acrylate, 60 parts by mass of butyl acrylate, 20 parts by mass of 2-hydroxyethyl acrylate, 1 part by mass of methacrylic acid, weight average obtained by polymerization in ethyl acetate 70 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass of the copolymer having a molecular weight of 500,000 to obtain an acrylic copolymer. 0.5 parts by mass of adduct isocyanate cross-linking agent Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photopolymerization initiator 4,4′-bis (diethylamino) benzophenone are added to the polymerized acrylic copolymer. The pressure-sensitive adhesive composition was obtained by adjusting with ethyl acetate to adjust the viscosity to be blended and easy to apply. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. An adhesive tape for protecting the surface of a semiconductor wafer according to Comparative Example 3 was produced by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

<Comparative example 4>
10 parts by mass of 2-ethylhexyl acrylate, 40 parts by mass of ethyl acrylate, 40 parts by mass of 2-hydroxyethyl acrylate, 10 parts by mass of methacrylic acid, a weight average obtained by polymerization in ethyl acetate 50 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass of the copolymer having a molecular weight of 600,000 to obtain an acrylic copolymer. 5 parts by mass of adduct isocyanate crosslinker Coronate L (trade name, manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts by mass of photoinitiator 4,4′-bis (diethylamino) benzophenone are blended into the polymerized acrylic copolymer. In order to adjust the viscosity to be easy to apply, adjustment was performed with ethyl acetate to obtain an adhesive composition. A pressure-sensitive adhesive composition was applied on a 25 μm-thick polyethylene terephthalate (PET) separator as a release film so that the film thickness after drying was 30 μm and dried. The adhesive tape for surface protection of the semiconductor wafer which concerns on the comparative example 4 was produced by laminating by bonding on a PET film.

<Comparative Example 5>
90 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of 2-hydroxyethyl acrylate, 1 part by weight of methacrylic acid, a copolymer having a weight average molecular weight of 900,000 obtained by polymerization in ethyl acetate 40 parts by mass of 2-isocyanatoethyl methacrylate was added to 100 parts by mass to obtain an acrylic copolymer. 1.5 parts by weight of adduct isocyanate crosslinking agent Coronate L (trade name, manufactured by Nippon Polyurethane) and 2 parts by weight of photoinitiator 4,4′-bis (diethylamino) benzophenone are added to the polymerized acrylic copolymer. And in order to adjust to the viscosity which is easy to apply, it adjusted with ethyl acetate and obtained the adhesive composition. A pressure-sensitive adhesive composition was applied on a polyethylene terephthalate (PET) separator having a thickness of 25 μm as a release film so that the film thickness after drying was 40 μm and dried, and then a substrate film having a thickness of 100 μm was formed. An adhesive tape for protecting the surface of a semiconductor wafer according to Comparative Example 5 was prepared by laminating by bonding onto an ethylene-vinyl acetate copolymer (EVA) film.

  The stress relaxation rate, elastic modulus, adhesive force, contact angle, storage elastic modulus, loss tangent, and tack force of the adhesive tape for protecting a semiconductor wafer surface according to each of Examples and Comparative Examples prepared as described above are as follows. And measured. The results are shown in Tables 1 and 2.

(Stress relaxation rate)
The semiconductor wafer surface protecting adhesive tapes according to the above examples and comparative examples were cut into a width of 25 mm and a length of 65 mm, respectively, to prepare test pieces. Using an Instron tensile tester (twin column tabletop model 5567), a test piece was placed on the compression parallel plate, the bending indenter was brought into contact with the thickness of the test piece, and the speed was 1.0 mm / min. After compressing, a load was applied up to a stress of 50N, and the stress obtained when the displacement at the time of the stress of 50N was maintained for 3 minutes was measured. The stress reduced by stress relaxation was obtained from the difference between the initial stress of 50 N and the stress obtained by measurement, and the ratio of the reduced stress to the initial stress value was calculated to obtain the stress relaxation rate.

(Elastic modulus)
A 25 mm wide strip of adhesive film was measured at a temperature of 23 ± 2 ° C. (preferably 23 ° C.), a relative humidity of 50 ± 5% (preferably 50%), a distance between marked lines and a distance between grips of 100 mm, and a pulling speed of 300 mm. The measurement was performed using a strograph tester at / min. The measured value is a value in the machining direction (MD). The elastic modulus of the adhesive tape for protecting the semiconductor wafer surface was determined from the stress-rate curve obtained by the measurement. The average of three measurements was used as the actual value.

(Adhesive strength to SUS)
Three test pieces each having a width of 25 mm and a length of 150 mm were collected from the semiconductor surface protecting adhesive tape before irradiation according to each example and each comparative example, and the sample was subjected to No. 280 water resistant polishing specified in JIS R 6253. A 2 kg rubber roller was applied to a 1.5 mm to 2.0 mm thick SUS steel plate specified in JIS G 4305, finished with paper, and pressed for 3 reciprocations. After 1 hour, the measured value was 15 to 85% of the capacity. Using a tensile tester conforming to JIS B 7721 that falls within the range, the adhesive strength was measured at room temperature (25 ° C.) by a 90 ° peeling method at a tensile speed of 50 mm / min, and the average value of three points was determined. Immediately after the measurement, the remaining surface of the adhesive tape for protecting a semiconductor surface according to each of the above examples and each comparative example was cured by irradiating with an irradiation amount of 500 mJ of ultraviolet light, and then the semiconductor surface after irradiation with radiation in the same manner as described above The adhesive strength of the protective adhesive tape was measured and the average value of 3 points was determined. Moreover, from the obtained value of each adhesive strength, the decrease rate of the adhesive strength before and after radiation irradiation [(adhesive strength before radiation irradiation-adhesive strength after radiation irradiation) / adhesive strength before radiation irradiation] × 100 was determined. .

(Contact angle φ for pure water on the surface of the adhesive layer)
The contact angle φ with respect to pure water of the adhesive layer surface of the adhesive tape for protecting a semiconductor wafer surface according to each example and each comparative example is a θ / 2 method using a contact angle meter at a temperature of 23 ° C. and a humidity of 50%. The measurement was performed under the conditions, and reading was performed 30 seconds after the dropping with a droplet volume of 2 μL of pure water.

(Storage modulus, loss tangent)
The storage elastic modulus and loss tangent were measured under the conditions of a frequency of 1 Hz and 25 ° C. using a shear type viscoelastic device (RES, manufactured by ARES). The test piece used was a cylindrical shape having a thickness of about 2 mm and a diameter of 8 mm obtained by laminating an adhesive layer.

(Measurement of tack force and change rate of tack force)
The tack force was measured at room temperature (25 ° C.) as follows using a tack tester (manufactured by Resuka Co., Ltd., TACII).
A test piece having a width of 25 mm and a length of 250 mm was taken from the adhesive tape for protecting the surface of a semiconductor wafer before irradiation according to each example and each comparative example, and this test piece was placed in a testing machine. The 3 mmφ cylindrical probe is pushed into the back surface side of the base film of the test piece (opposite to the pressure-sensitive adhesive coating surface) at a speed of 30 mm / min. The load at the time (tack force (Tα)) was measured. Also, the adhesive tape for protecting the surface of a semiconductor wafer according to each example and each comparative example was cured by irradiating ultraviolet rays with an irradiation amount of 500 mJ in an oxygen atmosphere, and an irradiation amount of 500 mJ with ultraviolet rays in the air. Specimens were collected from the specimens that had been irradiated and cured in the same manner as before, and the tack force (Tβ (N ₂ )) after irradiation in a nitrogen atmosphere and irradiation in air were performed in the same manner as before irradiation. The tack force (Tβ (air)) after measurement was measured. The unit of tack force is kPa. Using the obtained tack force values, the rate of change of tack force was determined by the following formula (1).
[Tα-Tβ air)] ÷ [Tα-Tβ (N ₂ )] × 100 (1)

  Moreover, about the adhesive tape for surface protection of the semiconductor wafer which concerns on said Example and comparative example, the following tests were done and the performance was evaluated. The evaluation results are shown in Tables 1 and 2.

1. Grindability test Using a Nitto Seiki Co., Ltd. DR8500II (trade name) as a pasting machine, a semiconductor wafer having a 725 μm thick 8-inch diameter device surface height of 30 μm, a width of 200 μm, and a depth of 5 μm. The adhesive layer surface exposed by peeling off the release film of the adhesive tape for protecting the surface of a semiconductor wafer according to Examples and Comparative Examples was bonded to the back surface of the adhesive layer. Thereafter, a laser was irradiated to the inside 50 μm above the final wafer grinding thickness to form a modified region inside. Subsequently, the back surface of each of the 25 semiconductor wafers was polished to a thickness of 200 μm using a grinder having an inline mechanism (manufactured by DISCO Corporation, DFG8760 (trade name)). In addition, final finishing was performed by dry polishing in order to improve the strength of the semiconductor wafer.

(Grindability evaluation)
About the semiconductor wafer ground by the said method, the presence or absence of an edge crack and the crack were observed visually. The results are shown in Tables 1 and 2. A good product that has been ground with all 25 semiconductor wafers with almost no edge cracks ◎, but with some edge cracks, the semiconductor wafers could be ground without cracks, or in 25 semiconductor wafers Those having 1 to 2 cracks were indicated as “good” and those having 3 or more semiconductor wafers cracked as “NG”.

(TTV measurement evaluation)
About the semiconductor wafer ground by the said method, the thickness was measured with TTV measuring apparatus Semidex300 (ISIS company make, brand name) in each arbitrary point. The results are shown in Tables 1 and 2. A product having a thickness variation of less than 4 μm on all 25 semiconductor wafers is regarded as a good product, and a product having a thickness variation of not less than 4 μm and less than 5 μm on all 25 semiconductor wafers is treated as a good product. A semiconductor wafer with three or more of the semiconductor wafers showing a thickness variation of 5 μm or more is indicated by “x” as a defective product.

(Dust penetration evaluation)
The semiconductor wafer ground to 200 μm thickness by the above method was observed for dust intrusion with a microscope and evaluated according to the following rank.
In all 25 semiconductor wafers, no dust or grinding water entered between the chips: Excellent product ◎
Only one or two of the 25 semiconductor wafers had dust or grinding water intruded between the chips:
3 or more of 25 semiconductor wafers in which dust or grinding water entered between chips:

2. Peel test (peelability evaluation)
After grinding the semiconductor wafer to a thickness of 200 μm by the above method, the adhesive layer of the adhesive tape for protecting the surface of the semiconductor wafer is cured by irradiating with an irradiation amount of 500 mJ, and mounter RAD2700 (product of Lintec Corporation, product) The adhesive tape for protecting the semiconductor wafer surface was peeled from the surface of the semiconductor wafer. The following ranks evaluated whether it was able to peel favorably.
All 25 semiconductor wafers could be peeled without damage: Excellent product
Those that could not be peeled in 25 semiconductor wafers, or those that could be peeled but had only one or two damaged semiconductor wafers:
What could not be peeled in 25 semiconductor wafers, or those where 3 or more semiconductor wafers were damaged:

(Adhesive residue evaluation)
The semiconductor wafer surface that was peeled off in the peeling experiment was observed for the presence or absence of adhesive residue, and evaluated according to the following rank.
No adhesive residue on all peeled semiconductor wafers: ◎
A peeled semiconductor wafer with one or two glue residues:
Exfoliated semiconductor wafer with 3 or more adhesive residues: ×

As shown in Table 1, the semiconductor wafer surface protecting adhesive tapes according to Examples 1 to 10 have an elastic modulus of 75 MPa or more and a stress relaxation rate of 10% to 18%. The remaining results were good in all of dust intrusion and peelability. In particular, in Examples 1 to 5, the adhesive strength of the adhesive layer to stainless steel was 3.0 N / 25 mm to 20.0 N / 25 mm before irradiation (normal temperature 25 ° C.), and after irradiation with radiation of 500 mJ. The adhesive strength (normal temperature 25 ° C.) is 0.01 N / 25 mm to 2.0 N / 25 mm, the contact angle of pure water on the pressure-sensitive adhesive layer surface is 85 ° or more, and the pressure-sensitive adhesive layer has a storage elasticity of 23 ° C. before irradiation. Since the rate is 7 × 10 ⁴ Pa or more, the tangent loss is 0.20 or less, and the change rate of tack force is 30% or more, it is particularly excellent in all of grindability, TTV, adhesive residue, dust intrusion, and peelability. It was a result.

  On the other hand, as shown in Table 2, the semiconductor wafer surface protecting adhesive tapes according to Comparative Examples 1 to 3 and 5 have an elastic modulus of less than 75 MPa or a stress relaxation rate of more than 18%. Occurred or the force applied to the semiconductor wafer was released, resulting in poor grindability and TTV. In addition, in Comparative Example 3, before irradiation (normal temperature 25 ° C.) exceeded 20.0 N / 25 mm, and the adhesive strength after irradiation with radiation of 500 mJ (normal temperature 25 ° C.) exceeded 2.0 N / 25 mm. The adhesive residue and peelability were also poor. In Comparative Example 4, since the stress relaxation rate is less than 10%, the followability with respect to the step difference on the surface of the semiconductor wafer is poor. As a result, the semiconductor wafer is broken and the TTV is poor. In addition, in Comparative Example 4, since the contact angle of pure water on the pressure-sensitive adhesive layer surface was less than 85 °, dust intrusion was poor.

1: Semiconductor wafer surface protective adhesive tape 2: base film 3: adhesive layer 4: release film 5: semiconductor wafer 6: dicing tape 7: modified region 8: grinding device 9: ring frame 11: chip

Claims (6)

When polishing the back surface of a semiconductor wafer in which a condensing point is aligned and a modified region is formed inside by being irradiated with a laser, the semiconductor is bonded to the surface on which the circuit pattern of the semiconductor wafer is formed. An adhesive tape for protecting the surface of a semiconductor wafer used for protecting the surface of a wafer,
Having an adhesive layer on at least one side of the base film,
The pressure-sensitive adhesive layer is a radiation-curable pressure-sensitive adhesive layer that is cured by irradiation with radiation,
A pressure-sensitive adhesive tape for protecting a semiconductor wafer, having an elastic modulus of 75 MPa or more and a stress relaxation rate obtained by the following formula (2) of 10 to 18% or less.
Stress relaxation rate R (t) = (F ₀ -F _(T) ) / F ₀ × 100 [%] (2)
(In the formula, F ₀ represents an initial compressive stress and is 50 N. The stress is compressed by a bending indenter at a speed of 1.0 mm / min. F _(t) represents a compressive stress after a lapse of 3 minutes. .) Adhesion at 25 ° C. before irradiation for stainless steel, a 3.0N / 25mm~20.0N / 25mm, adhesion at 25 ° C. after irradiation with radiation dose 500mJ is 0.01 N / 25 mm ~ The pressure-sensitive adhesive tape for protecting a semiconductor wafer according to claim 1, wherein the pressure-sensitive adhesive tape is 2.0 N / 25 mm.   The adhesive tape for protecting a semiconductor wafer surface according to claim 1 or 2, wherein a contact angle of the pressure-sensitive adhesive layer surface with respect to pure water is 85 ° or more.   4. The adhesive tape for protecting a semiconductor wafer surface according to claim 1, wherein the polymer as a main component constituting the adhesive layer is a (meth) acrylic polymer. 5. 5. The adhesive layer according to claim 1, wherein the adhesive layer has a storage elastic modulus at 25 ° C. before irradiation of radiation of 7 × 10 ⁴ Pa or more and a loss tangent of 0.20 or less. The adhesive tape for semiconductor wafer surface protection as described in one item | term. The change rate of tack force calculated | required by following formula (1) is 30% or more before and after the said adhesive layer irradiates radiation with an irradiation amount of 500 mJ, Any one of Claims 1-5 characterized by the above-mentioned. An adhesive tape for protecting a semiconductor wafer surface according to claim 1.
[Tα−Tβ (air)] ÷ [Tα−Tβ (N ₂ )] × 100 (%) (1)
(In the formula, Tα represents a measured value of tack force before irradiation, Tβ (air) represents a measured value of tack force after irradiation with an irradiation amount of 500 mJ in the presence of oxygen, and Tβ (N ₂ ) represents nitrogen. (A measured value of tack force after irradiation with an irradiation amount of 500 mJ in an atmosphere.)

Images