JP2018147989A - Method for manufacturing power device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a power device, by which even if a wafer with many concave and convex portions formed therein is subjected to a high-temperature treatment, the wafer can be surely protected, and an adhesive can be prevented from remaining deposited on the wafer.SOLUTION: A method for manufacturing a power device comprises: a tape-sticking step of laminating a wafer protection tape with a curable sticker layer made of a curable sticker composition on a circuit-side face of a wafer with a circuit protected by a polyimide film, provided that the wafer protection tape has a 23°C-tensile storage elastic modulus of 1×10Pa or more; a curing step of stimulating the wafer protection tape to cure the curable sticker composition; a back-grinding step of grinding a face of the wafer on a side opposite to a face where the wafer protection tape is laminated; a film formation step of forming a metal film on the ground face of the wafer; an ashing step of ashing the metal film; and a peeling step of peeling the wafer protection tape.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of manufacturing a power device that can reliably protect a wafer and prevent adhesive residue on the wafer even when a high-temperature treatment is performed on a wafer having a large number of irregularities.

In the manufacturing process of a semiconductor chip, it is generally performed to reinforce the semiconductor chip with an adhesive tape (wafer protection tape) in order to facilitate handling during processing of the semiconductor chip and prevent damage. For example, when a thick film wafer cut from a high-purity silicon single crystal or the like is ground to a predetermined thickness to form a thin film wafer, the grinding process is performed after applying an adhesive tape to protect the wafer. ing. In addition, conductive connection with electrodes on a substrate or another semiconductor chip is also performed while reinforcing the wafer with an adhesive tape.
As such a semiconductor wafer protective tape, for example, in Patent Document 1, a crosslinked polymer layer is formed on one surface of a base film, and the surface on which the crosslinked polymer layer is formed is adjusted to be peelable. A back grind tape on which a pressure-sensitive adhesive layer for wafer sticking is laminated, wherein the tensile modulus of the base film is 2 GPa or more in the average value in the longitudinal direction and the width direction of the film, A back grind tape having a warp of 4 mm or less is disclosed.

On the other hand, in a manufacturing process of a power device used for power conversion and control, a circuit is formed on one surface (front surface) of a wafer, and after the circuit is protected with a polyimide film, the opposite surface (back surface) is processed. As processing of this back surface, there are a back grinding process, a film forming process, and an ashing process in which a wafer is ground to form a thin film, and a wafer protective tape is used in the back grinding process.

In the conventional power device manufacturing method, the wafer protective tape is peeled off at the end of back grinding, and the subsequent steps are performed. However, the conventional manufacturing method has a problem that scratches, cracks, and deterioration occur in the wafer after the back surface processing is completed.
Therefore, it has been proposed to perform the subsequent processing as it is without peeling off the wafer protective tape attached at the time of back grinding. However, when a subsequent process is performed with the conventional wafer protective tape attached, there is a problem that an adhesive residue is generated on the wafer.

In the power device, a polyimide film is formed to protect the circuit on the wafer, and the polyimide film has many irregularities on the wafer surface. In order to sufficiently protect such a wafer having many irregularities with the wafer protective tape, the adhesive of the wafer protective tape needs to be flexible enough to follow the irregularities. However, when the pressure sensitive adhesive is made to follow the unevenness, the softened pressure sensitive adhesive bites into the unevenness during high-temperature processing such as a film forming process or an ashing process, and adhesion progresses. As a result, when the wafer protective tape was peeled off after the processing was finished, adhesive residue was generated on the wafer.

JP 2010-34379 A

The present invention provides a method of manufacturing a power device that can reliably protect a wafer even when a high temperature treatment is performed on a wafer on which a large number of irregularities are formed, and can prevent adhesive residue on the wafer. Objective.

The present invention relates to a curable pressure-sensitive adhesive comprising a curable pressure-sensitive adhesive composition having a tensile storage elastic modulus at 23 ° C. of 1 × 10 ⁵ Pa or more on a surface of a wafer whose circuit is protected by a polyimide film. A tape attaching step of laminating a wafer protective tape having a layer, a curing step of stimulating the wafer protective tape to cure the curable adhesive composition, and a side of the wafer on which the wafer protective tape is laminated A back grinding process for grinding a surface opposite to the surface; a film forming process for forming a metal film on the ground surface of the wafer; an ashing process for ashing the metal film; and the wafer protective tape It is a manufacturing method of the power device which has a peeling process which peels.
The present invention is described in detail below.

As a result of intensive studies on the cause of adhesive residue, the inventors of the present invention sufficiently follow a wafer having many irregularities by setting the storage elastic modulus of the adhesive of the wafer protective tape at 23 ° C. to a specific range. Found that it can be protected. In addition, by using a curable adhesive as the adhesive for the wafer protection tape and curing it before high-temperature processing, the wafer can be reliably protected and the adhesion progress under high temperature is suppressed, and the wafer is protected without adhesive residue after processing. It has been found that the tape can be peeled off, and the present invention has been completed.

In the method for producing a power device of the present invention, first, a curable pressure-sensitive adhesive having a tensile storage elastic modulus at 23 ° C. of 1 × 10 ⁵ Pa or more on a surface of the wafer on which a circuit is protected by a polyimide film. A tape attaching step of laminating a wafer protective tape having a curable pressure-sensitive adhesive layer made of the composition is performed.
By affixing the wafer protective tape, handling during processing can be facilitated and damage to the wafer can be prevented. The wafer protective tape may be a support type having a base material or a non-support type having no base material.
Here, FIG. 1 schematically shows a state in which the wafer protective tape is attached to the wafer. The circuit and the polyimide film 3 are formed on one surface of the wafer 2, and the circuit and the polyimide film 3 have a large number of irregularities on the one surface of the wafer. Wafer protective tape 1 having a curable pressure-sensitive adhesive layer made of a curable pressure-sensitive adhesive composition is attached to the surface on which this circuit and polyimide film 3 are formed. In the present invention, since the storage elastic modulus at 23 ° C. of the curable pressure-sensitive adhesive composition is in a specific range, the wafer protective tape follows a large number of irregularities on the wafer and can sufficiently protect the wafer. Hereinafter, the surface on which the wafer protective tape is laminated is also referred to as the front surface, and the surface opposite to the surface on which the wafer protective tape is laminated is also referred to as the back surface.

Examples of the curable pressure-sensitive adhesive in the curable pressure-sensitive adhesive composition include a photo-curable pressure-sensitive adhesive that is crosslinked and cured by light irradiation and a thermosetting pressure-sensitive adhesive that is crosslinked and cured by heating.
Examples of the resin component when the curable pressure-sensitive adhesive is photocurable include a photocurable pressure-sensitive adhesive containing a polymerizable polymer as a main component and a photopolymerization initiator.
Examples of the resin component when the curable pressure-sensitive adhesive is thermosetting include a thermosetting pressure-sensitive adhesive containing a polymerizable polymer as a main component and a thermal polymerization initiator.

The polymerizable polymer is prepared by, for example, previously synthesizing a (meth) acrylic polymer having a functional group in the molecule (hereinafter referred to as a functional group-containing (meth) acrylic polymer) and reacting with the functional group in the molecule. It can obtain by making it react with the compound (henceforth a functional group containing unsaturated compound) which has a functional group to perform and a radically polymerizable unsaturated bond.

The functional group-containing (meth) acrylic polymer is an acrylic having an alkyl group usually in the range of 2 to 18 as a polymer having adhesiveness at room temperature, as in the case of a general (meth) acrylic polymer. By copolymerizing an acid alkyl ester and / or methacrylic acid alkyl ester as a main monomer, a functional group-containing monomer, and, if necessary, another modifying monomer copolymerizable therewith by a conventional method It is obtained. The weight average molecular weight of the functional group-containing (meth) acrylic polymer is usually about 200,000 to 2,000,000.

Examples of the functional group-containing monomer include a carboxyl group-containing monomer such as acrylic acid and methacrylic acid; a hydroxyl group-containing monomer such as hydroxyethyl acrylate and hydroxyethyl methacrylate; and an epoxy group containing glycidyl acrylate and glycidyl methacrylate. Monomers; Isocyanate group-containing monomers such as isocyanate ethyl acrylate and isocyanate ethyl methacrylate; and amino group-containing monomers such as aminoethyl acrylate and aminoethyl methacrylate.

Examples of other modifying monomers that can be copolymerized include various monomers used in general (meth) acrylic polymers such as vinyl acetate, acrylonitrile, and styrene.

The functional group-containing unsaturated compound to be reacted with the functional group-containing (meth) acrylic polymer is the same as the functional group-containing monomer described above according to the functional group of the functional group-containing (meth) acrylic polymer. it can. For example, when the functional group of the functional group-containing (meth) acrylic polymer is a carboxyl group, an epoxy group-containing monomer or an isocyanate group-containing monomer is used, and when the functional group is a hydroxyl group, an isocyanate group-containing monomer is used. When the functional group is an epoxy group, a carboxyl group-containing monomer or an amide group-containing monomer such as acrylamide is used, and when the functional group is an amino group, an epoxy group-containing monomer is used.

Examples of the photopolymerization initiator include those activated by irradiation with light having a wavelength of 250 to 800 nm. Examples of such a photopolymerization initiator include acetophenone derivative compounds such as methoxyacetophenone; Benzoin ether compounds such as benzoin propyl ether and benzoin isobutyl ether; ketal derivative compounds such as benzyldimethyl ketal and acetophenone diethyl ketal; phosphine oxide derivative compounds; bis (η5-cyclopentadienyl) titanocene derivative compounds, benzophenone, Michler's ketone, Chlorothioxanthone, Todecylthioxanthone, Dimethylthioxanthone, Diethylthioxanthone, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenylpropane, etc. These radical photopolymerization initiators. These photoinitiators may be used independently and 2 or more types may be used together.

When the curable pressure-sensitive adhesive composition contains, for example, a polymer having an unsaturated double bond such as a vinyl group in the side chain and a photopolymerization initiator activated at a wavelength of 250 to 800 nm, light having a wavelength of 365 nm or more. Can be cross-linked and cured.
For such a curable pressure-sensitive adhesive composition, for example, light with a wavelength of 365 nm is preferably irradiated with an illuminance of 5 mW or more, more preferably with an illuminance of 10 mW or more, and irradiation with an illuminance of 20 mW or more. It is more preferable to irradiate with an illuminance of 50 mW or more. In addition, it is preferable to irradiate light with a wavelength of 365 nm with an integrated illuminance of 300 mJ or more, more preferably with an integrated illuminance of 500 mJ or more and 10,000 mJ or less, and more preferably with an integrated illuminance of 500 mJ or more and 7500 mJ or less. It is particularly preferable to irradiate with an integrated illuminance of 1000 mJ or more and 5000 mJ or less.

Examples of the thermal polymerization initiator include those that decompose by heat and generate active radicals that initiate polymerization. Examples thereof include dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, t- Examples thereof include butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramentane hydroperoxide, and di-t-butyl peroxide. These thermal polymerization initiators may be used independently and 2 or more types may be used together.

The curable pressure-sensitive adhesive composition may contain a crosslinking agent. As said crosslinking agent, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned, for example. In particular, an isocyanate-based crosslinking agent is preferable because of excellent adhesion stability to the substrate. Examples of the isocyanate-based crosslinking agent include Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation). These crosslinking agents may be used independently and 2 or more types may be used together.

Although the usage-amount of the said crosslinking agent is not restrict | limited in particular, The preferable minimum with respect to 100 weight part of the said polymeric polymers is 0.05 weight part, and a preferable upper limit is 10 weight part. When the amount of the crosslinking agent used is within this range, the curable pressure-sensitive adhesive composition can be sufficiently crosslinked.

The curable pressure-sensitive adhesive composition preferably further contains a radical polymerizable polyfunctional oligomer or monomer. By containing a radical polymerizable polyfunctional oligomer or monomer, curability is improved.
The polyfunctional oligomer or monomer preferably has a molecular weight of 10,000 or less, and more preferably has a molecular weight of 5000 or less and intramolecular radical polymerization so that a three-dimensional network of the curing component can be efficiently formed. The number of sex unsaturated bonds is 2-20.

The polyfunctional oligomer or monomer is, for example, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, or the same methacrylate as described above. And the like. Other examples include 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polypropylene glycol # 700 diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, and methacrylates similar to those described above. These polyfunctional oligomers or monomers may be used alone or in combination of two or more.

The said curable adhesive composition may contain the gas generating agent which generate | occur | produces gas by irritation | stimulation. When the curable pressure-sensitive adhesive composition contains the gas generating agent, it is easier to generate gas from the gas generating agent by stimulating the curable pressure-sensitive adhesive composition in the peeling step described later. In addition, the wafer protective tape can be peeled from the wafer without any adhesive residue.

Although the said gas generating agent is not specifically limited, Since it is excellent in the tolerance with respect to the process with a heating, carboxylic acid compounds, such as phenylacetic acid, diphenylacetic acid, and triphenylacetic acid, or its salt, 1H-tetrazole, 5-phenyl-1H- A tetrazole compound such as tetrazole or 5,5-azobis-1H-tetrazole or a salt thereof is preferred. Such a gas generating agent generates gas when irradiated with light such as ultraviolet rays, and has high heat resistance that does not decompose even at a high temperature of about 200 ° C.

Although content of the said gas generating agent in the said curable adhesive composition is not specifically limited, The preferable minimum with respect to 100 weight part of the said polymeric polymers is 5 weight part, and a preferable upper limit is 50 weight part. When the content of the gas generating agent is within this range, a sufficient peelability improving effect can be obtained. The minimum with more preferable content of the said gas generating agent is 10 weight part, and a more preferable upper limit is 30 weight part.

The curable pressure-sensitive adhesive composition may further contain an inorganic filler such as fumed silica. By blending the inorganic filler, the cohesive force of the curable pressure-sensitive adhesive composition is increased. For this reason, when protection becomes unnecessary after the reflow process, the wafer protective tape can be easily peeled off from the semiconductor chip without leaving glue.

The curable pressure-sensitive adhesive composition may further contain a silicone compound. Especially when the said curable adhesive composition contains a photocurable adhesive or a thermosetting adhesive, the silicone compound which has a functional group crosslinkable with this photocurable adhesive or a thermosetting adhesive It may contain.
Since the silicone compound is excellent in chemical resistance and heat resistance, the adhesive is prevented from being burnt even after high-temperature treatment in the ashing process, and at the time of peeling, it bleeds out to the adherend interface to facilitate peeling. When the silicone compound has a functional group capable of crosslinking with the photocurable pressure-sensitive adhesive or the thermosetting pressure-sensitive adhesive, chemical reaction with the photocurable pressure-sensitive adhesive or the thermosetting pressure-sensitive adhesive component by light irradiation or heating. And since it is taken in in the said photocurable adhesive or a thermosetting adhesive, a silicone compound adheres to an adherend and does not contaminate.

The curable pressure-sensitive adhesive composition may further contain known additives such as a plasticizer, a resin, a surfactant, a wax, and a fine particle filler.

The curable pressure-sensitive adhesive composition has a tensile storage elastic modulus at 23 ° C. of 1 × 10 ⁵ Pa or more during the tape attaching step.
By setting the tensile storage elastic modulus at 23 ° C. of the curable pressure-sensitive adhesive composition before curing to 1 × 10 ⁵ Pa or more, the curable pressure-sensitive adhesive composition acquires appropriate flexibility, and a wafer having a large number of irregularities. Even when affixed to the wafer, the wafer can be reliably protected by following the unevenness. The tensile storage elastic modulus at 23 ° C. of the curable pressure-sensitive adhesive composition is preferably 5.0 × 10 ⁵ Pa or more. In addition, the tensile storage elastic modulus at 23 ° C. is a condition of a dynamic viscoelasticity measurement tensile mode and an angular frequency of 10 Hz using a dynamic viscoelasticity measuring device (for example, DVA-200, manufactured by IT Measurement Control Co., Ltd.). It can be obtained by performing measurement.

Although the thickness of the said curable adhesive layer is not specifically limited, A preferable minimum is 5 micrometers and a preferable upper limit is 200 micrometers. When the thickness of the curable adhesive layer is within this range, it can adhere to the wafer with sufficient adhesive force following the unevenness of the wafer surface and prevent warping and cracking of the processed wafer. can do. The minimum with more preferable thickness of the said curable adhesive layer is 10 micrometers, and a more preferable upper limit is 100 micrometers.

In the method for producing a power device of the present invention, a curing step is then performed in which the wafer protective tape is stimulated to cure the curable pressure-sensitive adhesive composition.
When the curable pressure-sensitive adhesive composition is crosslinked and cured by light irradiation or heating, the elastic modulus of the curable pressure-sensitive adhesive composition is increased, and the adhesion is hardly promoted even at a high temperature. As a result, the wafer protective tape can be peeled without leaving glue even when high-temperature processing is performed on a wafer having a large number of irregularities.

The curable pressure-sensitive adhesive is a photo-curable pressure-sensitive adhesive, and contains a polymer having an unsaturated double bond such as a vinyl group in a side chain and a photopolymerization initiator activated at a wavelength of 250 to 800 nm. When an agent is used, the photocurable pressure-sensitive adhesive can be crosslinked and cured by irradiating light with a wavelength of 365 nm or more.
For such a photocurable pressure-sensitive adhesive, for example, light with a wavelength of 365 nm is preferably irradiated with an illuminance of 5 mW or more, more preferably with an illuminance of 10 mW or more, and irradiation with an illuminance of 20 mW or more. More preferably, irradiation with an illuminance of 50 mW or more is particularly preferable. In addition, it is preferable to irradiate light with a wavelength of 365 nm with an integrated illuminance of 300 mJ or more, more preferably with an integrated illuminance of 500 mJ or more and 10,000 mJ or less, and more preferably with an integrated illuminance of 500 mJ or more and 7500 mJ or less. It is particularly preferable to irradiate with an integrated illuminance of 1000 mJ or more and 5000 mJ or less.

The curable pressure-sensitive adhesive is a thermosetting pressure-sensitive adhesive and contains a polymer having an unsaturated double bond such as a vinyl group in the side chain and a thermal polymerization initiator that is activated by heating at about 50 to 150 ° C. When a thermosetting pressure-sensitive adhesive is used, the thermosetting pressure-sensitive adhesive can be crosslinked and cured by heating to a temperature of about 50 to 150 ° C.

In the power device manufacturing method of the present invention, a back grinding process is then performed in which the surface of the wafer opposite to the surface on which the wafer protective tape is laminated is ground.
The wafer is ground to a predetermined thickness by the back grinding process. In the present invention, since the wafer protective tape is stuck on the surface of the wafer, damage to the wafer due to impact and vibration during back grinding can be prevented.

In the method for manufacturing a power device according to the present invention, a film forming process for forming a metal film on the ground surface of the wafer is then performed. Examples of the metal film include Cu, Ti, and Al. In addition to the metal film, there may be a case where SiO, SiN or the like is formed as an insulating film for forming a metal circuit, and a polyimide film is formed as a protective film.
In the film forming step, high-temperature treatment at about 150 ° C. and chemical treatment are performed. However, in the present invention, since the curable pressure-sensitive adhesive composition is cured, the adhesion of the wafer protective tape due to the high-temperature treatment can be suppressed. Moreover, since the tolerance with respect to a chemical | medical solution is also improving by hardening of a curable adhesive composition, deterioration of the wafer protective tape by a chemical | medical solution can also be prevented.

In the method for manufacturing a power device of the present invention, an ashing process for ashing the metal film is then performed.
Unnecessary portions of the metal film are removed by ashing, and a predetermined pattern is formed. In the ashing process, since the wafer is exposed to a high temperature of about 200 ° C., the conventional wafer protection tape causes adhesion progress due to the high temperature and causes a residue of adhesive when the wafer protection tape is peeled off. In the present invention, since the curable pressure-sensitive adhesive composition is cured, adhesion progress can be suppressed even when a large number of irregularities exist on the wafer surface. In the ashing process, not only the metal film but also the wafer protective tape is decomposed. Among them, the adhesive with high flexibility is likely to be decomposed, and in the conventional wafer protection tape, adhesive residue is also generated due to the adhesive around the wafer being left in an island shape due to the decomposition by ashing. In the present invention, since the resistance to ashing is improved by curing the curable pressure-sensitive adhesive composition, the wafer protective tape can be peeled without any adhesive residue after the processing of the wafer.

In the method for manufacturing a power device of the present invention, a peeling process for peeling the wafer protective tape is then performed.
Since the curable pressure-sensitive adhesive composition is cured in the curing step, the wafer protective tape can be easily peeled off without leaving glue on the wafer even when there are numerous irregularities on the wafer surface. it can.

In the case where the curable pressure-sensitive adhesive composition contains the gas generating agent, the stage substrate is more easily generated by generating a gas from the gas generating agent by stimulating the wafer protective tape after the treatment in the peeling step. The wafer protective tape can be peeled off.

For example, when a gas generating agent that generates gas by irradiating light with a wavelength of 300 nm or less is used as the gas generating agent, gas is emitted from the gas generating agent by irradiating light with a wavelength of 300 nm or less. The support plate can be easily peeled off from the wafer.
For such a gas generating agent, for example, light with a wavelength of 254 nm is preferably irradiated with an illuminance of 5 mW or more, more preferably with an illuminance of 10 mW or more, and irradiation with an illuminance of 20 mW or more. More preferably, irradiation with an illuminance of 50 mW or more is particularly preferable. Moreover, it is preferable to irradiate light with a wavelength of 254 nm with an integrated illuminance of 1000 mJ or more, more preferably with an integrated illuminance of 1000 mJ or more and 20 J or less, and more preferably with an integrated illuminance of 1500 mJ or more and 15 J or less. It is particularly preferable to irradiate with an integrated illuminance of 2000 mJ or more and 10 J or less.

Further, for example, when a gas generating agent that generates gas by heating at 200 ° C. or higher is used as the gas generating agent, the gas is generated from the gas generating agent by heating to a temperature of 200 ° C. or higher, The support plate can be easily peeled from the wafer.

According to the present invention, there is provided a method for manufacturing a power device capable of reliably protecting a wafer and preventing adhesive residue on the wafer even when a high temperature treatment is performed on a wafer on which a large number of irregularities are formed. be able to.

It is the figure which represented typically the state by which the wafer protection tape was affixed on the wafer.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Production of wafer protective tape A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared. In this reactor, 94 parts by weight of 2-ethylhexyl acrylate as a (meth) acrylic acid alkyl ester, a monomer containing a functional group After adding 6 parts by weight of hydroxyethyl methacrylate, 0.01 part by weight of lauryl mercaptan and 80 parts by weight of ethyl acetate, the reactor was heated to start refluxing. Subsequently, 0.01 parts by weight of 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane was added as a polymerization initiator in the reactor, and polymerization was started under reflux. It was. Next, after 1 hour and 2 hours from the start of polymerization, 0.01 parts by weight of 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane was added, and the polymerization was started. 4 hours later, 0.05 part by weight of t-hexylperoxypivalate was added to continue the polymerization reaction. Then, 8 hours after the start of polymerization, an ethyl acetate solution of a functional group-containing (meth) acrylic polymer having a solid content of 55% by weight and a weight average molecular weight of 600,000 was obtained.
The resin solid content of 100 parts by weight of the ethyl acetate solution containing the functional group-containing (meth) acrylic polymer was added and reacted with 3.5 parts by weight of 2-isocyanatoethyl methacrylate as the functional group-containing unsaturated compound. To obtain a polymerizable polymer A. Thereafter, 20 parts by weight of silicone acrylate (EBECRYL 350, manufactured by Daicel Ornex Co., Ltd.), silica filler (Leosil Seal MT-10, manufactured by Tokuyama Co., Ltd.) with respect to 100 parts by weight of the resin solid content of the ethyl acetate solution of the obtained polymerizable polymer ) 20 parts by weight, 0.5 parts by weight of a chemical cross-linking agent (Coronate L-45, manufactured by Sekisui Fuller), and 1 part by weight of a photopolymerization initiator (Esacure One, manufactured by Nippon Siebel Hegner) were mixed to form acetic acid as a curable adhesive. An ethyl solution was obtained (see Table 1).

(2) As a sample for measuring and evaluating the tensile storage modulus of the curable pressure-sensitive adhesive composition, release of a transparent PET film having a thickness of 50 μm obtained by subjecting one side of the ethyl acetate solution of the curable pressure-sensitive adhesive to release treatment On the treated surface, apply a doctor knife so that the thickness of the curable pressure-sensitive adhesive layer after drying is 50 μm, and paste a transparent PET film with a thickness of 50 μm on which the release treatment is performed on the opposite side, The coating solution was dried by heating at 110 ° C. for 5 minutes, and then subjected to static curing at 40 ° C. for 3 days. Thereafter, the PET film was peeled off, and the pressure-sensitive adhesives were folded to form a 400 μm thick wafer protection tape, which was cut into a rectangular shape having a length of 0.6 cm and a width of 1.0 cm, and this was used as a sample for evaluation.
About the obtained sample for evaluation, using a dynamic viscoelasticity measuring device (DVA-200, manufactured by IT Measurement Control Co., Ltd.), measurement is performed at a tensile mode of dynamic viscoelasticity measurement, an angular frequency of 10 Hz, The value of tensile storage modulus was obtained. The results are shown in Table 1.

(3) Manufacturing a power device A wafer having a thickness of 700 μm on which a circuit film (thickness: 0.01 μm) and a polyimide film (the film is extracted in a lattice shape with a thickness of 2 μm, 1 cm □, and an interval of 3 mm) are formed. A wafer protective tape was affixed to the surface (front surface) on which the circuit was formed under vacuum. Next, using an ultra-high pressure mercury lamp from the wafer protective tape side, irradiating 365 nm ultraviolet rays for 1 minute while adjusting the illuminance so that the irradiation intensity to the wafer protective tape is 80 mW / cm ^2, and then curable adhesive composition Was crosslinked and cured. Thereafter, the wafer was ground from the back surface until the thickness of the wafer reached 100 μm. Next, a Cu film was formed on the ground wafer by sputtering. Subsequently, plasma ashing was performed on the formed wafer using PC-300 (manufactured by SUMCO) for 1 minute under predetermined conditions. The wafer protective tape was peeled off after plasma ashing.

(Comparative Example 1)
Production of wafer protective tape and measurement of tensile storage elastic modulus of curable pressure-sensitive adhesive layer in the same manner as in Example 1 except that the curable pressure-sensitive adhesive composition was not crosslinked and cured in “(3) Production of power device” And the manufacture of the power device was performed.

(Comparative Example 2)
Production of wafer protective tape, curable pressure-sensitive adhesive layer in the same manner as in Example 1 except that the blending amounts of silica filler and chemical crosslinking agent used in “(1) Production of wafer protective tape” are as shown in Table 1. The tensile storage elastic modulus was measured and the power device was manufactured.

<Evaluation>
The wafer tapes obtained in the examples and comparative examples were evaluated as follows.
The results are shown in Table 1.

(Evaluation of wafer protection performance)
The surface of the wafer after the wafer protection tape is peeled off is visually observed. If the wafer is not scratched, cracked, or deteriorated, “◯” is indicated. If the wafer is scratched, cracked, or deteriorated, “×” is indicated. evaluated.

(Evaluation of adhesive residue)
The surface of the wafer after peeling the wafer protective tape was visually observed. “◎” if no adhesive residue was present, “○” if the adhesive residue was less than 5% of the total area, and adhesive residue. The case where it was 5% or more of the entire area was evaluated as “x” and the adhesive residue was evaluated.

According to the present invention, there is provided a method for manufacturing a power device capable of reliably protecting a wafer and preventing adhesive residue on the wafer even when a high temperature treatment is performed on a wafer on which a large number of irregularities are formed. be able to.

1 Wafer protection tape 2 Wafer 3 Circuit and polyimide film

Claims (1)

A wafer having a curable pressure-sensitive adhesive layer made of a curable pressure-sensitive adhesive composition having a tensile storage elastic modulus at 23 ° C. of 1 × 10 ⁵ Pa or more on a surface of a wafer whose circuit is protected by a polyimide film. Tape affixing process for laminating protective tape;
A curing step of stimulating the wafer protective tape to cure the curable pressure-sensitive adhesive composition;
A backgrinding step of grinding the surface of the wafer opposite to the surface on which the wafer protective tape is laminated;
A film forming step of forming a metal film on the ground surface of the wafer;
An ashing step of ashing the metal film;
A method for producing a power device, comprising: a peeling step of peeling the wafer protective tape.

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