JPWO2015152010A1 - Protective film and method for manufacturing semiconductor device using the protective film - Google Patents

Abstract

A polyimide base material, an acrylic polymer (a) provided on one surface of the polyimide base material, a thermal radical generator (b) having a half-life temperature of 140 ° C. or higher and 200 ° C. or lower for 1 minute, and a crosslinking agent ( a thermosetting pressure-sensitive adhesive layer obtained from the composition comprising c), and a protective film to be affixed to the circuit forming surface of the semiconductor wafer.

Description

The present invention relates to a protective film and a method for manufacturing a semiconductor device using the protective film.
Specifically, the present invention relates to a protective film that is used in a manufacturing process of a semiconductor device such as a discrete device or an IGBT element and protects a circuit forming surface of a semiconductor wafer, and a method of manufacturing a semiconductor device using the protective film.

In the manufacture of discrete devices and IGBT elements, conventionally, a step of grinding a circuit non-formed surface of a semiconductor wafer (hereinafter referred to as “wafer backside” as appropriate), a step of etching a work-affected layer on the backside of a wafer with a chemical solution, Various processes are performed on the back side of the wafer, such as a step of forming a metal electrode on the back side of the wafer, and in the case of an IGBT element, a step of ion implantation into the back side of the wafer and an annealing step of activating the implanted dopant.
In particular, in the step of thinning the semiconductor wafer by grinding the back surface of the wafer, an adhesive layer is applied to the circuit forming surface of the semiconductor wafer (hereinafter referred to as “wafer surface” as appropriate) in order to prevent damage and contamination of the semiconductor wafer. A protective film with is attached.

Examples of such a protective film include the following.
For example, JP 2011-216735 A and JP 2011-213919 A disclose an adhesive tape for wafer processing provided with a radiation curable adhesive layer on a base resin film made of polyester resin. Is disclosed.
Japanese Patent Application Laid-Open No. 2010-287819 discloses that “an intermediate resin layer formed by curing an intermediate resin layer composition containing an adhesive component and a curing component on a base film and a radiation curable adhesive layer”. A semiconductor wafer processing pressure-sensitive adhesive tape in which and are laminated in this order is disclosed.
Japanese Patent Application Laid-Open No. 2011-249608 discloses that “a pressure-sensitive adhesive tape for protecting a semiconductor wafer surface comprising an adhesive layer made of a radiation-curable resin composition on a base resin film containing a polyester resin”. Is disclosed.

  In addition to the above, as a film provided with an adhesive layer, as a film for sticking to a semiconductor and protecting it at the time of processing a semiconductor having a reduced pressure heating process, for example, JP-A-2012-109585 discloses " A semiconductor processing tape is disclosed which includes a pressure-sensitive adhesive layer containing a photocurable pressure-sensitive adhesive, silica fine particles having a specific particle diameter, and a gas generating agent on at least one surface of a substrate.

  Furthermore, as a film provided with an adhesive layer, as a sheet for fixing a semiconductor wafer whose adhesive strength is reduced by heating, for example, Japanese Patent Application Laid-Open No. 10-025456 discloses a “sheet-like support and the support. In the semiconductor wafer fixing sheet, the main part of which is formed of a pressure-sensitive adhesive laminated thereon, the main components of the adhesive are 100 parts by weight of the base polymer, 10 to 900 parts by weight of the thermosetting compound and the start of heat polymerization. A sheet for fixing a semiconductor wafer characterized in that it is formed with 0.1 to 10 parts by mass of an agent is disclosed.

Moreover, as an adhesive sheet applied to a decorative sheet or the like, for example, Japanese Patent Laid-Open No. 8-302301 discloses a thickness of 500 μm having an oxygen transmission coefficient of “1 × 10 ⁸ cc · cm / cm ² · sec · cmHg or more. A heat-peelable pressure-sensitive adhesive sheet formed by forming a curable pressure-sensitive adhesive layer that does not cure or is delayed in the presence of oxygen in the following film-like substrate but is cured by heating is disclosed. The curable pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is based on 100 parts by weight of the pressure-sensitive rubber resin (A), 50 to 150 parts by weight of the ethylenically unsaturated group-containing compound (B), and 0 of the organic peroxide (C). It is also disclosed that 0.1 to 15 parts by mass, 0.01 to 5.00 parts by mass of a crosslinking agent (D) and 0.001 to 1.0 parts by mass of a polymerization inhibitor (E) are blended.
Yes.
This pressure-sensitive adhesive sheet has a feature that it can be easily peeled off by heating.

The various processes performed on the wafer back side described above include a step of heating the semiconductor wafer under vacuum.
In particular, in a process of performing processes such as metal vapor deposition, metal sputtering, and ion implantation, the semiconductor wafer is heated to 200 ° C. or higher under vacuum in a vacuum apparatus.
When a semiconductor wafer to which a film provided with the adhesive layer described in each patent document as described above is attached is heated to 200 ° C. or higher under vacuum, the film may be lifted or peeled off from the semiconductor wafer. In some cases, the adhesive strength may increase. If the film floats, it may be difficult to convey.
That is, the present situation is that a film having a conventional adhesive layer cannot be applied to a process in which heating at 200 ° C. or higher is performed under vacuum.
Here, in this specification, heating at 200 ° C. or higher under vacuum is appropriately referred to as “vacuum heating”.

Under the circumstances as described above, an object of the present invention is to apply a process that is performed under vacuum heating while being adhered to a semiconductor wafer after being adhered to a circuit forming surface of a semiconductor wafer and thermosetting the thermosetting adhesive layer. An object of the present invention is to provide a protective film that, when applied to a method for manufacturing a semiconductor device, suppresses the occurrence of floating while protecting the circuit forming surface of the semiconductor wafer and is excellent in releasability when peeling from the semiconductor wafer. .
Moreover, the other subject of this invention is providing the manufacturing method of the semiconductor device including the process performed under vacuum heating using the said protective film.

  Means for solving the above problems are as follows.

<1> a polyimide base material;
A composition comprising an acrylic polymer (a), a thermal radical generator (b) having a half-life temperature of 140 ° C. or more and 200 ° C. or less, and a crosslinking agent (c) provided on one surface of the polyimide substrate. A thermosetting adhesive layer obtained from the product,
A protective film that is attached to a circuit forming surface of a semiconductor wafer.

<2> The protective film according to <1>, wherein the thermal radical generator (b) has a molecular weight of 200 or more and 1000 or less.
<3> The protective film according to <1> or <2>, wherein the composition further contains a bifunctional or higher functional acrylic oligomer (d).
<4> The protective film according to any one of <1> to <3>, wherein the acrylic polymer (a) is a polymer having a radical-reactive double bond in a side chain.
<5> (1) An attaching step of attaching a protective film having a thermosetting adhesive layer to a circuit forming surface of a semiconductor wafer so that the circuit forming surface and the thermosetting adhesive layer are in contact with each other;
(2) a heating step of heating the semiconductor wafer to which the protective film is attached at a temperature of 120 ° C. or higher and 180 ° C. or lower;
(3) After the heating step of (2), a standing step of standing the semiconductor wafer to which the protective film is attached under vacuum,
(4) After the stationary step of (3), any one of metal vapor deposition, metal sputtering, and ion implantation is performed on the non-circuit-formed surface of the semiconductor wafer under vacuum and at 200 ° C. or higher. Processing steps;
The protective film according to any one of <1> to <4>, which is used as the protective film in a method for producing a semiconductor device comprising:

<6> (A) The protective film according to any one of <1> to <5> is attached to a circuit forming surface of a semiconductor wafer so that the thermosetting adhesive layer is in contact with the circuit forming surface. Pasting process,
(B) a grinding step of grinding a non-circuit-formed surface of the semiconductor wafer;
(C) a heating step of heating the semiconductor wafer to which the protective film is attached and the non-circuit-formed surface is ground at a temperature of 120 ° C. or higher and 180 ° C. or lower;
(D) after the heating step of (C), a standing step of standing the semiconductor wafer to which the protective film is stuck under vacuum;
(E) After the standing step of (D), under vacuum and at a temperature of 200 ° C. or higher, metal deposition, metal sputtering, and ion implantation are performed on the non-circuit-formed surface of the semiconductor wafer to which the protective film is attached. A processing step of applying any one of the processing;
(F) a peeling step of peeling the protective film from the semiconductor wafer;
A method for manufacturing a semiconductor device, comprising:

<7> After the pasting step (A) and before the grinding step (B),
(I) The method for producing a semiconductor device according to <6>, including a step of attaching a semiconductor wafer grinding film to the surface of the polyimide base material of the protective film.
<8> The method for producing a semiconductor device according to <6>, wherein the protective film used in the attaching step (A) is obtained by attaching a semiconductor wafer grinding film to a surface of a polyimide base material of the protective film. .
<9> After the grinding step (B) and before the heating step (C),
(Ii) The method for manufacturing a semiconductor device according to <7> or <8>, including a step of peeling the semiconductor wafer grinding film from the protective film.
<10> The method according to any one of <6> to <9>, wherein the grinding step (B) is a step of grinding an inner peripheral portion while leaving an outer peripheral portion of a non-circuit-formed surface in the semiconductor wafer. Semiconductor device manufacturing method.

According to the present invention, there is provided a method for manufacturing a semiconductor device, including a step of applying a vacuum heating while being attached to a semiconductor wafer after being attached to a circuit forming surface of a semiconductor wafer and thermosetting the thermosetting adhesive layer. When applied, it is possible to provide a protective film that suppresses the occurrence of floating while protecting the circuit forming surface of the semiconductor wafer and is excellent in releasability when peeling from the semiconductor wafer.
Moreover, according to this invention, the manufacturing method of the semiconductor device including the process performed under vacuum heating using the said protective film can be provided.

Hereinafter, the present invention will be described in detail.
In this specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
The protective film of the present invention is a polyimide base and a thermal radical generator (a) provided on one surface of the polyimide base and having an acrylic polymer (a) and a one-minute half-life temperature of 140 ° C. or higher and 200 ° C. or lower ( b) (hereinafter referred to as “specific thermal radical generator (b)” as appropriate) and a thermosetting adhesive layer obtained from a composition containing a crosslinking agent (c), and forming a circuit on a semiconductor wafer It is a protective film affixed to the surface.

By adopting the configuration as described above, even when applied to a method of manufacturing a semiconductor device including a process performed under vacuum heating, the occurrence of floating is suppressed while protecting the circuit forming surface of the semiconductor wafer, and A protective film having excellent releasability when peeled from a semiconductor wafer is obtained.
The relationship with the effect produced by adopting the configuration of the present invention is not clear, but is estimated as follows.

The thermal radical generator (b) having a one-minute half-life temperature of 140 ° C. or more and 200 ° C. or less contained in the thermosetting adhesive layer is suitable for storage at room temperature or when forming a thermosetting adhesive layer. Decomposition is difficult to start under dry conditions, and it has the property of decomposing even without heating conditions that develop adhesive strength that makes it difficult to peel from the semiconductor wafer.
In addition, the polyimide base material is unlikely to be softened by heating, can maintain a high elastic modulus even at a high temperature, has a property such that the thermal expansion coefficient is close to that of a semiconductor wafer, and the thermal contraction ratio is low.
By combining the thermosetting adhesive layer using the thermal radical generator (b) as described above and a polyimide base material, the protective film of the present invention is applied to the circuit forming surface of a semiconductor wafer, and the thermosetting adhesive By thermosetting the layer, it is estimated that it is difficult to expand even at a high temperature, and that it can be a pressure-sensitive adhesive layer (after thermosetting) having peelability from the semiconductor wafer.
As a result, due to the presence of the adhesive layer after curing, the protective film of the present invention suppresses the occurrence of floating even when subjected to a process performed in a harsh environment such as under vacuum heating, and protects the circuit forming surface of the semiconductor wafer. Can be continued, and after that, excellent peelability can also be exhibited when peeling from the semiconductor wafer.

  Hereinafter, the polyimide base material and the thermosetting adhesive layer constituting the protective film of the present invention will be described.

(Thermosetting adhesive layer)
The thermosetting pressure-sensitive adhesive layer in the present invention (hereinafter sometimes abbreviated as “pressure-sensitive adhesive layer”) is an acrylic polymer (a), a one-minute half-life temperature of 140 ° C. or higher and 200 ° C. or lower. It is obtained from the composition containing (b) and a crosslinking agent (c).

-Acrylic polymer (a)-
The acrylic polymer (a) is a binder resin that serves as a base for the pressure-sensitive adhesive in the pressure-sensitive adhesive layer, and can be obtained by copolymerizing several general (meth) acrylic acid ester monomers. As the (meth) acrylic acid ester monomer constituting the acrylic polymer (a), those known for pressure-sensitive adhesives can be applied.
Since the protective film of the present invention is exposed to a high temperature, the acrylic polymer (a) preferably has a high thermal decomposition temperature. In general, an acrylic polymer polymerized from an acrylate monomer is more heat resistant than an acrylic polymer polymerized from a methacrylic acid ester monomer (thermally decomposable). 50 mol% or more) is more preferable.

Suitable monomers for obtaining the acrylic polymer (a) are, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl. Examples include methacrylate, octyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, dodecyl acrylate, dodecyl methacrylate, and the like.
The side chain alkyl group of these monomers may be linear or branched. Moreover, you may use together 2 or more types of said acrylic acid alkylester monomers according to the objective.

The acrylic polymer (a) preferably has a functional group that reacts with a cross-linking agent (c) described later from the viewpoint of adjusting the properties (eg, adhesiveness) of the adhesive layer.
Specifically, the functional group that reacts with the crosslinking agent (c) of the acrylic polymer (a) is preferably a carboxylic acid group, a hydroxyl group, a glycidyl group, or the like. In addition, a carboxylic acid group, a hydroxyl group, a glycidyl group, etc. react with polyisocyanate and polyfunctional epoxy resin which are crosslinking agents (c). In order to introduce such a functional group, a (meth) acrylic acid ester monomer having such a functional group may be copolymerized.
Examples of the (meth) acrylic acid ester monomer having a functional group that reacts with the crosslinking agent (c) include monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; And monomers having a hydroxyl group such as ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate; monomers having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate;

Moreover, it is preferable that an acrylic polymer (a) has a radical reactive double bond in a side chain from the point which hardens an adhesion layer. In order to introduce such a radical reactive double bond, a (meth) acrylic acid ester monomer having such a radical reactive double bond may be added to the copolymerized main polymer side chain.
As a combination of such reactions, a well-known technique, in which glycidyl (meth) acrylate is copolymerized in the main chain, and (meth) acrylic acid is added to the glycidyl group of the main chain as a secondary reaction. A method in which (meth) acrylic acid is copolymerized in the main chain and glycidyl (meth) acrylate is added to the (meth) acrylic acid moiety as a secondary reaction; a monomer having the hydroxyl group in the main chain is copolymerized; In addition, a (meth) acrylic acid ester having an isocyanate group such as 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, 1,1- (bisacryloyloxymethyl) ethyl isocyanate is added to the hydroxyl group by a secondary reaction. The method of making it react; etc. are mentioned.
In applications where heat resistance is required, such as the protective film of the present invention, from the viewpoint of thermal decomposability, as the side chain addition reaction mentioned above, the reaction of acid and glycidyl is more effective than the reaction of isocyanate and hydroxyl group. Better than reaction.
The acrylic polymer (a) has a radical-reactive double bond in the side chain so that the radicals generated from the specific thermal radical generator (b) react with each other between the acrylic polymers (a). Alternatively, the reaction between the acrylic polymer (a) and the later-described bifunctional or higher acrylic oligomer becomes possible.

  The acrylic polymer (a) is preferably contained in the composition in the range of 50% by mass to 99.5% by mass, and more preferably in the range of 65% by mass to 99% by mass.

-Specific thermal radical generator (b)-
The specific thermal radical generator (b) used in the present invention is a component selected from the following points.
That is, in the present invention, an adhesive layer formed by dissolving each component (including the acrylic polymer (a), the specific thermal radical generator (b), and the crosslinking agent (c)) used in obtaining the adhesive layer in a solvent. The coating liquid is applied on a polyimide substrate (or separator) and dried to produce a protective film.
Since heat is applied during the drying, it is preferable to select a temperature at which the decomposition is difficult to start at the drying temperature. Also, those having a high decomposition temperature are preferable in terms of storage stability at room temperature. On the other hand, if the decomposition temperature is too high, it will be necessary to raise the temperature to decompose, and the adhesiveness will increase under the high temperature conditions, making it difficult to peel from the semiconductor wafer, so the decomposition temperature is too high. Things are also not preferred.
From the above points, the specific thermal radical generator (b) used in the present invention needs to have a one-minute half-life temperature of 140 ° C. or higher and 200 ° C. or lower.
Here, the 1 minute half-life temperature of the specific thermal radical generator is preferably 145 ° C. or higher and 180 ° C. or lower.

In addition, if the solvent is volatilized together with the solvent during the drying, the amount of the specific thermal radical generator (b) in the adhesive layer decreases, and it becomes difficult to obtain a sufficient reaction. It is preferable to select one that is difficult to do.
From such a point, the molecular weight of the specific thermal radical generator is preferably 200 to 1000, more preferably 200 to 700, and still more preferably 300 to 700.

As the specific thermal radical generator (b), known peroxides, azo compounds and the like having a 1 minute half-life temperature in the above range are used.
Specific examples of the specific thermal radical generator (b) include the following, but the present invention is not limited thereto.
In the following specific examples, in addition to the compound name, a commercial product name (all manufactured by NOF Corporation), molecular weight, and 1-minute half-life temperature are also shown.

  Specific commercial products of the specific thermal radical generator (b) include, for example, Perhexa MC, Perhexa TMH, Perhexa HC, Perhexa C, Pertetra A, Perhexyl I, Perbutyl 355, Perbutyl L, Perbutyl manufactured by NOF Corporation. E, perhexyl Z, perhexa 25Z, perhexa 22, perhexa V, perbutyl P, park mill D, perhexyl D, perhexa 25B, perbutyl C, perhexine 25B, and the like are preferable.

The amount of the specific thermal radical generator (b) added is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the total amount of monomers constituting the acrylic polymer (a). Preferably they are 0.2 mass part or more and 2 mass parts or less, More preferably, they are 0.3 mass part or more and 1 mass part or less.
If the amount of the specific thermal radical generator added is too small, there may be a problem that the adhesive layer is not sufficiently cured by heat and the tackiness is increased. On the other hand, if the amount is too large, X-ray photoelectron spectroscopy (XPS / There may be a problem that contamination of a semiconductor wafer or contamination of a vacuum apparatus is caused by a substance (such as a recombination product of radicals) detected by an ESCA) or a minute particle detector.

-Crosslinking agent (c)-
The crosslinking agent (c) in the present invention is a component that can react with the acrylic polymer (a) to form a crosslinked body (three-dimensional crosslinked body) of the acrylic polymer (a).
By adjusting the acrylic polymer (a) to a crosslinked product, adjustment of the initial adhesive strength of the adhesive layer, ease of cutting of the tape (easiness of cutting the adhesive layer on the cut surface), pressure deformation, etc. are adjusted. Furthermore, thermal decomposition of the main chain of the acrylic polymer (a) can be suppressed.
As the crosslinking agent (c), an isocyanate-based or epoxy-based crosslinking agent, which is a general crosslinking agent for an acrylic pressure-sensitive adhesive, is used.

  Moreover, it is preferable to select a crosslinking agent with high heat resistance (thermal decomposability) from the viewpoint of improving the heat resistance (thermal decomposability) of the acrylic polymer (a).

In the present invention, preferred crosslinking agents (c) include those shown below, but the present invention is not limited thereto.
That is, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, resorcin diglycidyl ether Examples include chemical epoxy compounds such as tetrad C and tetrad X; isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate triadduct of trimethylolpropane, polyisocyanate, isocyanurate type isocyanate, and the like.

When the amount of the crosslinking agent is small, the pressure-sensitive adhesive layer before curing becomes soft and fluid and tends to be excellent in wettability and unevenness followability to the wafer surface. However, when there are few crosslinking agents, shape stability will worsen and there exists a possibility that a level | step difference mark may become easy to produce | generate when the protective film of this invention is preserve | saved as a roll. Moreover, when the protective film of this invention is cut, there exists a possibility that the cut of an adhesive may worsen.
On the other hand, when the amount of the crosslinking agent is large, the adhesive layer before curing becomes hard, it is difficult to obtain wettability and unevenness followability to the wafer surface, and the protective film may float under vacuum heating.
In the present invention, the addition amount of the crosslinking agent (c) may be determined in consideration of the above points.
The proper addition amount of the crosslinking agent is preferably increased because the tendency to become a soft adhesive is promoted when there are many bifunctional or higher acrylic oligomers added to the composition of the present invention. .
For example, the addition amount of the crosslinking agent (c) is preferably 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total amount of monomers constituting the acrylic polymer (a). 2 parts by mass or more and 10 parts by mass or less are more preferable.

-2 or more functional acrylic oligomer (d)-
It is preferable that the composition for obtaining the thermosetting adhesive layer in the present invention further contains a bifunctional or higher functional acrylic oligomer (d).
The bifunctional or higher-functional acrylic oligomer (d) is an acrylic oligomer having two or more radical-reactive double bonds, and reacts with radicals generated by the specific thermal radical generator (b). It is a component that contributes to curing.
When the above-mentioned acrylic polymer (a) does not have a radical reactive double bond in the side chain, it becomes essential as a component for thermosetting the adhesive layer.

When the pressure-sensitive adhesive layer after heat curing is hard and brittle, the pressure-sensitive adhesive layer may break while it is biting into the irregularities on the wafer surface, and a part of the pressure-sensitive adhesive layer may remain on the wafer surface (also referred to as residue). For this reason, it is good to adjust the addition amount, the number of functional groups, etc. of bifunctional or more acrylic oligomer (d) so that the elongation at the time of the tensile fracture of the adhesion layer after thermosetting may become large. If a large number of functional groups having a large molecular weight is added, it may be hard and brittle. On the other hand, if a large amount of a functional group having a small number of functional groups is added, the cured product becomes soft, and there is a risk that the cured product is insufficiently cured and remains stuck.
The bifunctional or higher acrylic oligomer (d) is preferably hexafunctional or lower, more preferably trifunctional or higher and pentafunctional or lower.
Since the protective film of the present invention requires heat resistance, it is preferable to select a bifunctional or higher acrylic oligomer (d) having a structure with high heat resistance (not easily thermally decomposed). From the viewpoint of heat resistance, those having an ester bond are preferable to those having a urethane bond.

  The molecular weight of the acrylic oligomer (d) is preferably from 200 to 10,000, and more preferably from 300 to 5,000, from the viewpoint of cured properties.

  Specific examples of the bifunctional or higher acrylic oligomer (d) include commercially available urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, pentaerythritol polyacrylate, dipentaerythritol polyacrylate, ethoxylated isocyanuric acid triacrylate, tri Examples include methylolpropane triacrylate and ditrimethylolpropane tetraacrylate.

The bifunctional or higher functional acrylic oligomer (d) may be added in the case where the acrylic polymer (a) has a radical reactive double bond in the side chain. The acrylic oligomer (d) functions as a low molecular weight component, and the unevenness followability and wettability of the pressure-sensitive adhesive layer before thermosetting to the wafer surface are improved. Moreover, when many bifunctional or higher functional acrylic oligomers (d) are used, particularly when the number of functional groups is large, the cured adhesive layer becomes hard and brittle, and the adhesive layer described above may break.
From the above points, the addition amount of the bifunctional or higher-functional acrylic oligomer (d) is 0 to 100 parts by mass, more preferably 0 to 50 parts by mass with respect to 100 parts by mass of the acrylic polymer (a). Less than parts by mass is appropriate.
Further, when the acrylic polymer (a) does not have a radical-reactive double bond in the side chain, it is essential as a component for thermally curing the adhesive layer, but a bifunctional or higher-functional acrylic oligomer (d ) Is insufficient, the thermosetting of the adhesive layer is insufficient, and a part of the adhesive layer may remain (cohesive failure) on the wafer surface. Moreover, when many bifunctional or higher functional acrylic oligomers (d) are used, the adhesive layer may break.
From the above points, the amount of addition when the bifunctional or higher functional acrylic oligomer (d) is essential is 1 to 100 parts by mass, more preferably 100 parts by mass with respect to 100 parts by mass of the acrylic polymer (a). 20 mass parts or more and 50 mass parts or less are suitable.

-Thickness of adhesive layer-
The thickness of the pressure-sensitive adhesive layer obtained from the composition containing each component as described above is preferably formed to a thickness that can sufficiently follow the irregularities on the wafer surface.
Specifically, the thickness of the adhesive layer is suitably 10 μm or more and 100 μm or less, more preferably 20 μm or more and 50 μm or less.

(Polyimide substrate)
The polyimide base material in the present invention is selected from the following points.
That is, when the base material is subjected to vacuum heating, if the base material is softened, it is not preferable because the base material is fixed to the contacting member. Moreover, it is preferable that a high elastic modulus can be maintained even at high temperatures.
The semiconductor wafer (silicon wafer) to which the protective film of the present invention is attached is processed to be as thin as 150 μm or less, and in some cases, 100 μm or less. When such a thin semiconductor wafer and a protective film are applied and then heated, if the linear expansion coefficient of the base material is greatly deviated from the thermal expansion coefficient of silicon of the semiconductor wafer, the semiconductor wafer is warped. . When the semiconductor wafer is warped in the apparatus under vacuum heating, there arises a problem that the wafer is detached from the wafer holding means and cannot be transported or the wafer is broken. From this point, a material having a thermal expansion coefficient close to that of silicon is preferable. Further, when the base material is thermally contracted in the heating process due to stress remaining in the base material in the manufacturing process of the base material, warping is also caused, which causes a problem in conveyance and crack side surfaces.
In this way, the base material does not soften at high temperatures and suppresses warping of thin semiconductor wafers, so it is difficult to thermally decompose, maintain the elastic modulus at high temperatures, and the thermal expansion coefficient does not deviate significantly from the semiconductor wafer. In addition, low heat shrinkage is required.
In consideration of such points, polyimide is selected as the material.

  Moreover, the drying process which reduces the water | moisture content contained in a protective film is performed before the process performed under vacuum heating. In this drying step, it is preferable to select a polyimide substrate having good water vapor permeability from the viewpoint of easily removing moisture from the protective film.

If the adhesion between the polyimide substrate and the adhesive layer is poor, the adhesive may remain on the wafer surface when the protective film is peeled off.
Therefore, the adhesive strength between the pressure-sensitive adhesive layer and the polyimide base material is obtained by subjecting the polyimide base material to a surface treatment (such as a known discharge treatment (corona, plasma) or a coupling agent treatment) or an adhesive layer. Is preferably increased.

The thickness of the polyimide base material is preferably 25 μm or more and 100 μm or less, and more preferably 38 μm or more and 50 μm or less.
If the polyimide base material is too thin, wrinkles may be easily formed at the time of sticking. On the other hand, if it is too thick, the water vapor permeability may be deteriorated or the followability to the irregularities on the surface of the semiconductor wafer may be deteriorated. .

A commercially available polyimide substrate may be used as the polyimide substrate.
Specifically, for example, Kapton (registered trademark) of Toray DuPont, Apical (registered trademark) of Kaneka, Upilex (registered trademark) of Ube Industries, etc. have been commercialized and can be used. .

-Production of protective film-
The protective film is produced as follows.
First, each component which comprises the composition used in order to obtain an adhesion layer is melt | dissolved in a solvent, and the coating liquid for adhesion layer formation is prepared.
The prepared adhesive layer forming coating solution is applied on a polyimide substrate with a coating device at a thickness corresponding to the thickness of the adhesive layer after drying, and then dried in a drying furnace to produce a protective film. .
The pressure-sensitive adhesive layer-forming coating solution is applied on the polyimide substrate or separator with a coating device at a thickness corresponding to the thickness of the pressure-sensitive adhesive layer after drying, and then dried in a drying furnace. You may create a protective film using the method of obtaining the laminated body of the structure of a separator / adhesion layer / polyimide base material by bonding with a separator or a polyimide base material. Such a protective film of the laminate may be peeled off before being attached to the semiconductor wafer.
In the drying of the coating solution for forming the adhesive layer, it is preferable to select a temperature and a residence time in the drying furnace that do not decompose the specific thermal radical generator (b). In drying, it is preferable to select the temperature and the residence time in the drying furnace in consideration of sufficiently removing the volatile component such as a solvent so that the protective film can be prevented from floating under vacuum heating.
Specifically, for example, the temperature in the drying step is preferably 60 ° C. or higher and 130 ° C. or lower, and the residence time is preferably 1 minute or longer and 10 minutes or shorter.

-Application of protective film-
It is preferable that the protective film of this invention is used as a protective film in the manufacturing method of the semiconductor device including the process of the following (1)-(4).
(1) A sticking step of sticking a protective film having a thermosetting adhesive layer on a circuit forming surface of a semiconductor wafer so that the circuit forming surface and the thermosetting adhesive layer are in contact with each other. (2) The protective film is attached. Heating step of heating the semiconductor wafer at a temperature of 120 ° C. or higher and 180 ° C. or lower (3) After the heating step of (2), a stationary step of standing the semiconductor wafer to which the protective film is attached under vacuum,
(4) After the stationary step of (3), any one of metal vapor deposition, metal sputtering, and ion implantation is performed on the non-circuit-formed surface of the semiconductor wafer under vacuum and at 200 ° C. or higher. Processing Step Here, the step (1) is described later in (A) a sticking step, the step (2) is described in (C) a heating step, and the step (3) is described in (D) static. The step (4) corresponds to the (E) processing step under vacuum heating described later. The details of each step are the same as the corresponding (A) sticking step, (C) heating step, (D) standing step, and (E) processing step under vacuum heating, and thus are omitted here.

(Method for manufacturing semiconductor device)
Next, the manufacturing method of the semiconductor device using the protective film of this invention is demonstrated.
A method for manufacturing a semiconductor device of the present invention includes:
(A) An attaching step of attaching the protective film of the present invention to the circuit forming surface of the semiconductor wafer so that the thermosetting adhesive layer is in contact with the circuit forming surface;
(B) a grinding step of grinding a non-circuit-formed surface of the semiconductor wafer;
(C) a heating step of heating the semiconductor wafer to which the protective film is attached and the non-circuit-formed surface is ground at a temperature of 120 ° C. or higher and 180 ° C. or lower;
(D) after the heating step of (C), a standing step of standing the semiconductor wafer to which the protective film is stuck under vacuum;
(E) After the standing step of (D), under vacuum and at a temperature of 200 ° C. or higher, metal deposition, metal sputtering, and ion implantation are performed on the non-circuit-formed surface of the semiconductor wafer to which the protective film is attached. A processing step of applying any one of the processing;
(F) a peeling step of peeling the protective film from the semiconductor wafer;
A method for manufacturing a semiconductor device including:
Hereinafter, each step will be described.

-(A) Pasting process-
In the (A) sticking step in the present invention, the sticking is performed so that the thermosetting adhesive layer in the protective film of the present invention is in contact with the circuit forming surface of the semiconductor wafer.
This (A) sticking process is performed before or after the (B) grinding process.
When the (A) sticking step is performed before the (B) grinding step, the semiconductor wafer to which the protective film of the present invention is stuck is applied to the (B) grinding step as it is.
Moreover, when (A) a sticking process is performed after (B) a grinding process, it sticks so that the adhesion layer in a well-known protective film may contact | connect the circuit formation surface of a semiconductor wafer before a (B) grinding process. Perform the process. Moreover, after performing the (B) grinding process using the semiconductor wafer with which the well-known protective film was stuck, the process of peeling a well-known protective film from a semiconductor wafer is performed.
Since the number of steps is small and there is no need to replace the protective film, it is preferable to perform the (A) pasting step before the (B) grinding step.

A known tape applicator can be applied to the protective film of the present invention applied to the semiconductor wafer.
In order to apply air to the irregularities of the circuit on the wafer surface without applying air, it is preferable to use a vacuum applicator. It is not preferable to bite air because (E) the protective film floats in the processing step performed under vacuum heating.

-(B) Grinding process-
In the grinding step (B) in the present invention, the non-circuit-formed surface (wafer back surface) of the semiconductor wafer is ground.
(B) In the grinding process, for example, a semiconductor wafer to which the protective film of the present invention or the conventional protective film is attached is fixed to a chuck table of a grinding machine via a polyimide base material, and a circuit is not formed on the semiconductor wafer. Grind the surface (wafer back).
After the grinding is finished, when the conventional protective film is stuck on the semiconductor wafer, the protective film is peeled off.

  After the grinding of the back surface of the wafer is completed, an etching process step using a chemical solution such as chemical etching or polishing on the back surface of the wafer may be performed on the semiconductor wafer with the protective film attached.

In addition, after the grinding of the back surface of the wafer is completed or the etching process is performed, the semiconductor wafer to which the protective film of the present invention is attached is preheated to remove moisture in the protective film. May be.
The protective film of the present invention is composed of an acrylic pressure-sensitive adhesive and a polyimide base material, both of which are materials having a high moisture absorption rate. Since the grinding process and the etching process are processes using water, the protective film of the present invention is in a moisture-absorbing state.
When the moisture-absorbing protective film is heated in the heating step (C), floating may occur due to rapid expansion of moisture absorbed. In order to suppress this, it is preferable to use an oven or the like and preheat and dry the semiconductor wafer to which the protective film of the present invention is attached at 60 ° C. or higher and 100 ° C. or lower for several minutes to several tens of minutes.

-(C) Heating step-
In the heating step (C) in the present invention, the semiconductor wafer to which the protective film of the present invention is attached and the non-circuit-formed surface is ground is heated at a temperature of 120 ° C. or higher and 180 ° C. or lower. This step may be carried out under reduced pressure or under increased pressure, but if it is carried out under reduced pressure, floating may occur due to the generated gas accompanying decomposition of the peroxide. It is preferable to carry out at atmospheric pressure from the viewpoint that a general-purpose oven can be used.
By this (C) heating step, the adhesive layer of the protective film of the present invention is thermally cured.
By this (C) heating step, it is possible to prevent the adhesion of the pressure-sensitive adhesive layer excellent in wetting and unevenness tracking from being promoted and becoming inseparable.
Moreover, it is preferable that the decomposition of the specific heat radical generator (b) is completed in this step in order to suppress the floating of the protective film by the gas generated by the decomposition of the specific heat radical generator (b). .
From such a point, the heating conditions in the (C) heating step may be set according to the 1-minute half-life temperature of the used specific thermal radical generator (b). For example, the specific thermal radical generator (b ), Preferably within ± 30 ° C. (more preferably within ± 20 ° C.).
(C) Specifically, the heating step is performed at a temperature of 120 ° C. or higher and 180 ° C. or lower (preferably 130 ° C. or higher and 170 ° C. or lower) at atmospheric pressure, and several minutes or longer and 1 hour or shorter (preferably 1). It is preferable to perform heating for 3 minutes to 1 hour, more preferably 3 minutes to 30 minutes, still more preferably 5 minutes to 30 minutes, particularly preferably 10 minutes to 30 minutes.

-(D) Standing step and (E) Processing step under vacuum heating-
In the (D) standing step in the present invention, after the heating step (C), the semiconductor wafer to which the protective film of the present invention is stuck is left under vacuum.
Further, (E) in the treatment step under vacuum heating, (D) after the standing step, the metal is deposited on the non-circuit-formed surface of the semiconductor wafer to which the protective film is attached under vacuum and at 200 ° C. or higher. , Any one of metal sputtering and ion implantation is performed.

(E) In the treatment process under vacuum heating, a vacuum deposition apparatus is applied to metal deposition, a sputtering apparatus is applied to metal sputtering, and an ion implantation apparatus is applied to ion implantation. Vacuum equipment.
In these vacuum apparatuses, generally, a semiconductor wafer is allowed to stand in a preliminary exhaust chamber, and after reaching a certain degree of vacuum (for example, 1 Pa or less), the semiconductor wafer is transferred to this apparatus. The standing in the preliminary exhaust chamber is the above-described (D) standing step. In this apparatus, metal vapor deposition, metal sputtering, or ion implantation is performed under vacuum, and the semiconductor wafer in the apparatus at that time is heated to 200 ° C. or higher. In addition, although the upper limit of the heating in the processing step (E) under vacuum heating is determined by the type of the processing, the heating / cooling mechanism of the apparatus, etc., specifically, it is about 300 ° C.

-(F) Peeling step-
In the (F) peeling process in the present invention, (E) the protective film of the present invention is peeled from the semiconductor wafer after the treatment process under vacuum heating.
Although the operation of peeling the protective film of the present invention from the wafer surface may be performed manually, it is generally performed using an apparatus called an automatic peeling machine. As such an automatic peeling machine, Takatori Co., Ltd., Model: ATRM-2000B, ATRM-2100, Teikoku Seiki Co., Ltd., Model: STP Series, Nitto Seiki Co., Ltd., Model: HR-8500II Etc. Moreover, as an adhesive tape called a peeling tape used when peeling the protective film of the present invention from the wafer surface by the automatic peeling machine, for example, Sumitomo 3M Co., Ltd., Highland Mark Filament Tape No. 897 or the like can be used.

  The temperature at which the protective film of the present invention is peeled off from the wafer surface is usually performed at room temperature of about 25 ° C. However, when the above-described automatic peeling machine has a function of heating the wafer, the semiconductor wafer You may peel off a protective film in the state heated up to predetermined temperature (usually about 40 degreeC-90 degreeC).

  The wafer surface after peeling off the protective film of the present invention is cleaned as necessary. Examples of the cleaning method include wet cleaning such as water cleaning and solvent cleaning, and dry cleaning such as plasma cleaning. In the case of wet cleaning, ultrasonic cleaning may be used in combination. These cleaning methods are appropriately selected depending on the contamination state of the wafer surface.

  In the method for manufacturing a semiconductor device of the present invention, it is preferable to further include the following steps.

That is, the polyimide base material is hard, and when the thickness of the adhesive layer is thin, the unevenness on the wafer surface may not be absorbed. In this case, the back surface of the convex portion may be excessively ground during grinding in the (B) grinding step.
From the standpoint of preventing this, a method of applying a known semiconductor wafer grinding film to the surface of the polyimide base material (non-adhesive surface of the adhesive layer) in the protective film of the present invention is employed.
As a method of applying the semiconductor wafer grinding film, (B) the step of attaching the semiconductor wafer grinding film to the surface of the polyimide base material of the protective film applied to the semiconductor wafer ((i) )) Or a method of applying a semiconductor wafer grinding film in advance to the surface of the polyimide base material of the protective film.
The semiconductor wafer grinding film used here preferably includes a soft / stress relaxation layer that absorbs irregularities on the wafer surface.
The semiconductor wafer grinding film is preferably peeled off from the protective film of the present invention after the (B) grinding step and before the (C) heating step ((ii) step).

(B) A semiconductor wafer that has been ground and thinned in a grinding step is likely to warp or break. From this point, in order to suppress warpage of the thinned semiconductor wafer and increase the strength, (B) the grinding step is a step of grinding the inner peripheral portion while leaving the outer peripheral portion of the circuit non-formed surface in the semiconductor wafer. Preferably there is. That is, in the (B) grinding step, it is preferable to use a so-called Tyco process, in which the outer peripheral edge of the semiconductor wafer is left thick and the strength is increased while the center is ground to a predetermined thickness.
The polyimide base material in the protective film of the present invention does not cause thermal expansion and does not completely match the thermal expansion coefficient with the silicon wafer. Therefore, in situations where more severe warpage control is required (for example, when the semiconductor wafer is further thinned or subjected to high temperatures), the above-described Tyco process is used in combination with the protective film of the present invention applied. Thus, it is preferable to suppress the occurrence of warpage of the semiconductor wafer. This makes it difficult for a conveyance failure or the like due to warpage to occur.

  Semiconductor wafers to which the method for manufacturing a semiconductor device of the present invention can be applied are not limited to silicon wafers, but include semiconductor wafers such as gallium nitride, germanium, gallium-arsenic, gallium-phosphorus, and gallium-arsenic-aluminum.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Preparation of adhesive layer forming coating solution)
The components shown in Table 2 below were used in the amounts shown in Table 2 (described in parentheses) and mixed and stirred to prepare coating solutions 1 to 10 for forming an adhesive layer.
Here, in Table 2, a compounding quantity is a mass part with respect to 100 mass parts of monomers in an acrylic polymer, and is a mass ratio of solid content.

Polymers 1 and 2, oligomers 1 and 2, peroxides 1 to 5, and crosslinking agent 1 abbreviated in Table 2 are as follows.
Polymer 1: 82 parts of ethyl acrylate, 10 parts of methyl methacrylate, 8 parts of hydroxybutyl acrylate and 0.5 parts by weight of benzoyl peroxide as a polymerization initiator are mixed, 65 parts by weight of toluene, 50 parts by weight of ethyl acetate Was added dropwise at 80 ° C. over 5 hours while stirring in a nitrogen-substituted flask containing, and the reaction was further stirred for 5 hours to obtain an acrylate copolymer solution. This was designated as Polymer 1.
Polymer 2: 48 parts by mass of ethyl acrylate, 27 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl acrylate, 5 parts by mass of glycidyl methacrylate, and 0.5 parts by mass of benzoyl peroxide as a polymerization initiator The mixture was added dropwise to a nitrogen-substituted flask containing 65 parts by mass of toluene and 50 parts by mass of ethyl acetate with stirring at 80 ° C. over 5 hours, and further stirred for 5 hours to be reacted. After completion of the reaction, the mixture was cooled, 25 parts by mass of xylene, 2.5 parts by mass of acrylic acid, and 1.5 parts by mass of tetradecylbenzylammonium chloride were added and reacted at 80 ° C. for 10 hours while blowing air. An acrylate copolymer solution having a carbon-carbon double bond introduced therein was obtained. This was designated as Polymer 2.

・ Oligomer 1: AD-TMP (manufactured by Shin-Nakamura Chemical, ditrimethylolpropane tetraacrylate)
・ Oligomer 2: Aronics M-402 (Toagosei, dipentaerythritol penta and hexaacrylate)
・ Peroxide 1: Pertetra A (manufactured by NOF, 2,2-Di (4,4-di- (t-butylperoxy) cyclohexyl) propane, molecular weight 561, 1 minute half-life temperature 154 ° C.)
・ Peroxide 2: Niper BMT (manufactured by NOF, 1 minute half-life temperature 131 ° C)
Peroxide 3: Parroyl TCP (manufactured by NOF, molecular weight 399, half-life temperature 92 ° C. for 1 minute)
Peroxide 4: Perbutyl C (manufactured by NOF, t-Butyl cumyl peroxide, molecular weight 208, 1 minute half-life temperature 173 ° C.)
Peroxide 5: Parkmill P (manufactured by NOF, molecular weight 194, 1 minute half-life temperature 233 ° C.)
・ Crosslinking agent 1: Olester P49-75S (Mitsui Chemicals)

[Production of protective film]
The adhesive layer-forming coating solution shown in Table 2 was applied to a 38 μm-thick polyimide film (Kapton 150EN-A manufactured by Toray DuPont) so that the dry thickness was 30 μm, and dried at 100 ° C. for 6 minutes. The protective film of Examples 1-4 and Comparative Examples 1-6 was produced.
Thereafter, the cross-linking agent was reacted with an acrylic polymer at 40 ° C. for 7 days.

[Evaluation of adhesive tape]
After each protective film was attached to the mirror surface of a 6-inch silicon wafer, it was heated in an oven at 80 ° C. for 10 minutes (preliminary heating), and then heated under the conditions described in Table 2 to form an adhesive layer. Was heat-cured (Comparative Examples 4 and 5 were not heated). Then, after putting the silicon wafer which stuck the protective film into a vacuum oven and putting it under vacuum, it heated at 250 degreeC for 30 minutes. Whether or not the protective film was lifted in the oven was visually confirmed.
After returning to room temperature after vacuum heating, the protective film was peeled off from the silicon wafer, and it was visually confirmed whether or not the adhesive layer remained on the silicon wafer.
The evaluation index is as follows. The results are shown in Table 2.

  As is clear from Table 2, the protective films of Examples 1 to 4 are acrylic polymer (a), specific heat radical generator (b), crosslinker (c), and bifunctional or higher acrylic in the present invention. Because it has a pressure-sensitive adhesive layer obtained from a coating solution containing an oligomer (d), the protective film does not float even when subjected to vacuum heating after thermosetting, and no residue remains I understand.

[Examples A to D, Comparative Examples a to f, and Reference Examples]
Using the protective films of Examples 1 to 4 and Comparative Examples 1 to 6, preheating, thermosetting of the adhesive layer, and vacuum heating were performed as follows.
Example A: After the protective film of Example 1 was attached to the mirror surface of a 6-inch silicon wafer, this was heated in an oven at 80 ° C. for 10 minutes (preliminary heating), and then heated in an oven at 150 ° C. for 15 minutes. Then, the adhesive layer was thermally cured. Subsequently, this was put into a vacuum oven and placed under vacuum, and then heated at 250 ° C. for 30 minutes.
Note that the preheating and the heating during the thermosetting of the adhesive layer were performed under atmospheric pressure.
Examples B to D, Comparative Examples a to f, and Reference Example: Except that the protective film used in Example A was changed to the protective film described in Table 3 below and the heating described in Table 3 below was performed. Same as Example A.
During vacuum heating in Examples A to D, Comparative Examples a to f, and Reference Examples, whether or not the protective film was lifted was visually confirmed in the oven.
Moreover, after returning to room temperature after vacuum heating, the protective film was peeled from the silicon wafer, and it was visually confirmed whether or not the adhesive layer remained on the silicon wafer.
The results are shown in Table 3.

As is apparent from Table 3, using the protective films of Examples 1 to 4, preheating, thermosetting the adhesive layer at a temperature of 120 ° C. or higher and 180 ° C. or lower, and leaving it in a vacuum at 200 ° C. or higher. It can be seen that in Examples A to D in which the protection was performed, the protective film was not lifted, and no residue remained.
Comparative Examples a to c using the protective films of Comparative Examples 1 to 3 which were preheated, thermally cured the pressure-sensitive adhesive layer at a temperature of 120 ° C. or higher and 180 ° C. or lower, and allowed to stand in a vacuum at 200 ° C. or higher It was found that although the protective film did not float, there was a residue.
This is because the one-minute half-life temperature of the thermal radical generator contained in the adhesive layer is less than 140 ° C. (Comparative Examples 1 and 2), or no thermal radical generator is used (Comparative Example). 3). It is speculated that the thermal radical generator decomposes or volatilizes in the drying stage of the adhesive layer due to the 1-minute half-life temperature of the thermal radical generator being less than 140 ° C., and the thermosetting of the adhesive layer is insufficient. The Similarly, when the thermal radical generator is not used, it is presumed that the thermosetting of the adhesive layer was insufficient. As a result, it is presumed that the adhesive layer was suddenly heated to a high temperature by vacuum heating despite the fact that the thermosetting was not sufficiently advanced, so that the adhesiveness increased and a residue was generated.
Comparative Example d using the protective film of Comparative Example 4, after preheating, without performing the thermosetting of the adhesive layer and leaving it under vacuum and at 200 ° C. or higher, did not cause a residue, The protective film was lifted. This is because a coating solution containing a large amount of a crosslinking agent is used, so that it is a hard adhesive layer, has low wettability with respect to the silicon wafer, and was unable to maintain adhesion to the silicon wafer during vacuum heating. Presumed to be.
In Comparative Example e, in which the protective film of Comparative Example 5 was used, and after the preliminary heating, the adhesive layer was not thermally cured, and was left in a vacuum at 200 ° C. or higher, the protective film did not float. However, it was found that there was a residue. This is because it uses a coating solution with a small amount of crosslinking agent added, it is a soft adhesive layer, excellent wettability to the silicon wafer, and was able to maintain adhesion to the silicon wafer even under vacuum heating, It is presumed that the adhesiveness has increased due to the high temperature, and the residue remains.
According to the reference example, even if the protective film of Example 1 was used, it was found that if the heat curing process was not performed, no residue remained, but the protective film floated. This is presumed that the gas component accompanying the decomposition of the specific thermal radical generator (peroxide) triggered the generation of floating under vacuum heating.

Example E
The protective film of Example 1 was affixed to the mirror surface of an 8-inch silicon wafer (mirror) ((A) affixing process).
Subsequently, the back surface of the wafer was ground to a thickness of 100 μm using a disco back grinder ((B) grinding step).
After grinding, the wafer was not cracked and warpage was 1 mm or less.
Next, the wafer was dried in an oven at 80 ° C. for 10 minutes (preliminary heating), and then further heated in an oven at 150 ° C. for 15 minutes to cure the adhesive layer ((C) heating step). Note that the preheating and the heating during the thermosetting of the adhesive layer were performed under atmospheric pressure.
After the adhesive layer was cured, the warpage of the wafer was about 2 mm, which was the amount of warpage that could be handled by the wafer transfer device.
Subsequently, the wafer was put into a vacuum oven and placed under vacuum, and then heated at 250 ° C. for 30 minutes. No floating occurred in the vacuum oven.
Thereafter, when the protective film of Example 1 was peeled off from the wafer returned to the atmospheric pressure and room temperature environment, no residue was observed on the wafer surface.

The disclosure of Japanese application 2014-07489, filed on March 31, 2014, is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims (10)

A polyimide substrate;
A composition comprising an acrylic polymer (a), a thermal radical generator (b) having a half-life temperature of 140 ° C. or more and 200 ° C. or less, and a crosslinking agent (c) provided on one surface of the polyimide substrate. A thermosetting adhesive layer obtained from the product,
A protective film that is attached to a circuit forming surface of a semiconductor wafer.   The protective film according to claim 1, wherein the thermal radical generator (b) has a molecular weight of 200 or more and 1,000 or less.   The protective film according to claim 1, wherein the composition further contains a bifunctional or higher functional acrylic oligomer (d).   The protective film according to any one of claims 1 to 3, wherein the acrylic polymer (a) is a polymer having a radical-reactive double bond in a side chain. (1) An attaching step of attaching a protective film having a thermosetting adhesive layer to a circuit forming surface of a semiconductor wafer so that the circuit forming surface and the thermosetting adhesive layer are in contact with each other;
(2) a heating step of heating the semiconductor wafer to which the protective film is attached at a temperature of 120 ° C. or higher and 180 ° C. or lower;
(3) After the heating step of (2), a standing step of standing the semiconductor wafer to which the protective film is attached under vacuum,
(4) After the stationary step of (3), any one of metal vapor deposition, metal sputtering, and ion implantation is performed on the non-circuit-formed surface of the semiconductor wafer under vacuum and at 200 ° C. or higher. Processing steps;
The protective film of any one of Claims 1-4 used as the said protective film in the manufacturing method of the semiconductor device containing this. (A) an attaching step of attaching the protective film according to any one of claims 1 to 5 to a circuit forming surface of a semiconductor wafer so that the thermosetting adhesive layer is in contact with the circuit forming surface; ,
(B) a grinding step of grinding a non-circuit-formed surface of the semiconductor wafer;
(C) a heating step of heating the semiconductor wafer to which the protective film is attached and the non-circuit-formed surface is ground at a temperature of 120 ° C. or higher and 180 ° C. or lower;
(D) after the heating step of (C), a standing step of standing the semiconductor wafer to which the protective film is stuck under vacuum;
(E) After the standing step of (D), under vacuum and at a temperature of 200 ° C. or higher, metal deposition, metal sputtering, and ion implantation are performed on the non-circuit-formed surface of the semiconductor wafer to which the protective film is attached. A processing step of applying any one of the processing;
(F) a peeling step of peeling the protective film from the semiconductor wafer;
A method for manufacturing a semiconductor device, comprising: After the attaching step (A) and before the grinding step (B),
(I) The manufacturing method of the semiconductor device of Claim 6 including the process of sticking the film for semiconductor wafer grinding on the surface of the polyimide base material of the said protective film.   The method for manufacturing a semiconductor device according to claim 6, wherein the protective film used in the attaching step (A) is obtained by attaching a semiconductor wafer grinding film to a surface of a polyimide base material of the protective film. After the grinding step (B) and before the heating step (C),
(Ii) The method for manufacturing a semiconductor device according to claim 7 or 8, comprising a step of peeling the semiconductor wafer grinding film from the protective film.   10. The semiconductor device according to claim 6, wherein the grinding step (B) is a step of grinding an inner peripheral portion while leaving an outer peripheral portion of a circuit non-formation surface in the semiconductor wafer. Manufacturing method.