JP4511840B2 - Adhesive film and method for protecting semiconductor wafer using the same - Google Patents

Description

  The present invention relates to an adhesive film and a method for grinding a back surface of a semiconductor wafer using the same. Specifically, the adhesive film is attached to the surface of the semiconductor wafer such as a silicon wafer where the integrated circuit is incorporated (hereinafter referred to as the wafer surface), and the other surface of the wafer (hereinafter referred to as the wafer back surface) is ground. In this case, the present invention relates to a semiconductor wafer back surface grinding method useful for preventing breakage of a semiconductor wafer, and an adhesive film used in the method.

  In general, a semiconductor integrated circuit is obtained by slicing a high-purity silicon single crystal or the like into a wafer, and then incorporating the integrated circuit by ion implantation or etching, and grinding the back surface of the wafer by grinding, polishing, lapping, etc. It is manufactured by a method of dicing into chips after reducing the thickness to about 100 to 600 μm. In these processes, an adhesive film is used to prevent the semiconductor wafer from being damaged when the back surface of the wafer is ground.

  Specifically, an adhesive film is directly attached to the wafer surface via the adhesive layer to protect the wafer surface, and then the other surface of the wafer (hereinafter referred to as the wafer back surface) is ground. After the grinding is completed, the adhesive film is peeled off from the wafer surface.

  When conventional adhesive films are used to grind the backside of a semiconductor wafer that has integrated circuits built into the periphery of the wafer, that is, the scribe line reaches the outermost periphery of the wafer, Water may enter between the wafer surface and the pressure-sensitive adhesive layer through the recess caused by the line, and the wafer may be damaged due to this, or grinding waste may enter with the water to contaminate the wafer surface. In order to prevent this problem, measures are taken to increase the thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film and improve the adhesion between the recesses on the wafer surface and the pressure-sensitive adhesive layer. However, when this means is used, the process proceeds to the next step after the completion of grinding. Therefore, when peeling the adhesive film, it is difficult to peel the adhesive film firmly adhered. As described above, the pressure-sensitive adhesive film for wafer back grinding has been required to satisfy the contradictory conditions of high adhesion and easy peeling.

  As means for solving such a problem, for example, in Japanese Patent Laid-Open No. 60-189938, when polishing the back surface of a semiconductor wafer, a pressure-sensitive adhesive film is attached to the surface of the wafer, and after the polishing, the adhesion is performed. In a method for protecting a semiconductor wafer from which a film is peeled off, the pressure-sensitive adhesive film is a light-transmitting support and a pressure-sensitive adhesive having a property of being cured by light irradiation provided on the support to form a three-dimensional network. A method for protecting a semiconductor wafer is disclosed, comprising: a layer, wherein the adhesive film is irradiated with light before being peeled off after polishing.

  The method for protecting a semiconductor wafer disclosed in the above invention can reduce the adhesive force of the adhesive film to the wafer surface by irradiating with light before peeling. Without consideration, the adhesion to the wafer surface at the time of back surface grinding can be sufficiently increased, and the above-described problem of water and grinding dust intrusion between the wafer surface and the adhesive layer is solved.

  However, when this adhesive film is used, it is necessary to irradiate light before peeling the adhesive film from the wafer surface after back grinding, so it is necessary to introduce light irradiation equipment into the process, There is a problem that the apparatus becomes larger and complicated, or the process becomes complicated and workability is lowered. There is also a problem that the working environment is deteriorated by ozone generated by light irradiation. Furthermore, depending on various conditions such as the surface shape of the wafer, light irradiation intensity, and time, a problem of adhesive residue may occur on the wafer surface after peeling due to poor curing of the pressure-sensitive adhesive layer. In order to prevent this problem, it is necessary to fill the inside of the light irradiation device with an inert gas such as nitrogen. Therefore, there are problems that the manufacturing cost increases and the process is further increased in size and complexity.

  In recent years, semiconductor wafers tend to have larger diameters and thinner layers year by year due to technological innovation and cost reduction in the semiconductor industry. In particular, the thickness of semiconductor wafers after back grinding is becoming increasingly thinner due to increasing demand for semiconductor chips that are required to be thin, such as thin packaging and smart card applications. is there. Since the time required for grinding the back surface increases with the area of the wafer, it is considered that the problem of wafer breakage / contamination due to the ingress of water and grinding debris during grinding becomes more likely as the wafer becomes larger in diameter. Furthermore, considering that the strength of the wafer itself decreases as the thickness of the wafer decreases, the above-mentioned problem of damage to the wafer during peeling is expected to become more serious as the wafer becomes thinner. Is done.

  In addition, due to diversification of semiconductor wafer back surface grinding processes in recent years, there are an increasing number of wafers having a surface shape in which a part of the adhesive tends to remain. For example, as a wafer having a chip suitable for the smart card application, a wafer having a protruding high bump electrode having a height of 5 to 100 μm has been produced. When grinding the back surface of a semiconductor wafer having a protruding high bump electrode as described above, when the adhesive film is peeled from the ground wafer, a part of the adhesive remains on the surface of the wafer (hereinafter referred to as The surface of the wafer may be contaminated. This contamination often occurs around the high bump electrode. In that case, it is difficult to remove the contamination even after the post-treatment such as washing after the adhesive film is peeled off from the wafer, which is a particularly serious problem. There was a thing.

Under such circumstances, the back surface is well grounded to the concave portion of the wafer surface and does not cause damage to the wafer and contamination of the wafer surface due to the ingress of water and grinding debris. There is a demand for a pressure-sensitive adhesive film for semiconductor wafer back grinding that can be peeled off without causing damage to the wafer and that can be used as it is in the conventional process without investing in new facilities.
Japanese Patent Laid-Open No. 60-189938

  In view of the above problems, the object of the present invention is to prevent damage and contamination of the wafer due to the ingress of water and grinding debris between the wafer surface and the adhesive layer when grinding the back surface of the semiconductor wafer. Another object of the present invention is to provide a pressure-sensitive adhesive film that can be easily peeled off after completion of grinding, and a method of grinding a back surface of a semiconductor wafer using the same.

  As a result of intensive studies, the inventors of the present invention have made it possible to regenerate isocyanate groups by heating in the pressure-sensitive adhesive layer, blocked polyisocyanates having at least two blocked isocyanate groups, and polymers having groups capable of reacting with isocyanate groups. The present invention was completed by finding that an adhesive film capable of controlling the adhesive force by heating can be obtained by containing.

    When grinding the back surface of the semiconductor wafer, if the adhesive film of the present invention is used, not only does the wafer break during grinding due to the grinding stress on the back surface, but also water and the adhesive layer between the wafer surface and the adhesive layer. There is no wafer breakage or contamination of the wafer surface due to the ingress of grinding debris. In addition, since the adhesive force can be controlled by the heat treatment, the wafer can be prevented from being damaged when the adhesive film is peeled from the wafer.

  Hereinafter, the present invention will be described in detail. The present invention is a pressure-sensitive adhesive film in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive having a specific composition is formed on one surface of a base film, and a semiconductor wafer back surface grinding method using the pressure-sensitive adhesive film.

  The pressure-sensitive adhesive film of the present invention is, for example, a polymer having a group capable of reacting with an isocyanate group (hereinafter also referred to as a pressure-sensitive adhesive polymer), a blocked polyisocyanate, and other crosslinks as necessary on one surface of a base film or a release film. It can be produced by applying a solution or emulsion solution containing an agent and other additives (hereinafter collectively referred to as a pressure-sensitive adhesive coating solution) and drying to form a pressure-sensitive adhesive layer.

  When forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive coating solution to one surface of a base film, a release film is stuck on the surface of the applied pressure-sensitive adhesive layer in order to protect it from contamination caused by the environment. It is preferable. On the other hand, when an adhesive coating liquid is applied to one surface of a release film to form an adhesive layer, a method of transferring the adhesive layer to a substrate film is employed. Whether to apply the pressure-sensitive adhesive coating solution to one surface of the base film or release film is determined in consideration of the heat resistance of the base film and release film and the contamination of the semiconductor wafer surface. For example, when the heat resistance of the release film is superior to that of the base film, it is preferable to transfer to the base film after providing an adhesive layer on the surface of the release film. When the heat resistance is equivalent or the base film is excellent, it is preferable to provide a pressure-sensitive adhesive layer on the surface of the base film and attach a release film to the surface.

  However, the adhesive film for grinding the back surface of the semiconductor wafer is adhered to the surface of the semiconductor wafer through the surface of the adhesive layer exposed when the release film is peeled off. In order to prevent this, the method of using a release film with good heat resistance, applying an adhesive coating solution on the surface, drying to form an adhesive layer, and transferring this to a base film is better. preferable. The pressure-sensitive adhesive film for semiconductor wafer backside grinding of the present invention is usually stored in a state where a release film is stuck on the surface of the pressure-sensitive adhesive layer, and is peeled off during use.

As the base film used in the present invention, a film obtained by molding a synthetic resin into a film is used. The base film may be a single layer or a laminate. As for the thickness of a base film, 10-500 micrometers is preferable. More preferably, it is 70-500 micrometers. Examples of the raw material resin include synthetic resins such as polyamide and polyethylene terephthalate. When the melting point of at least one layer of the base film is 200 ° C. or higher, melting of the resin by heating does not occur, and the semiconductor wafer and the base material Is preferable because it can be peeled off smoothly.
Examples of the release film used in the present invention include synthetic resin films such as polypropylene and polyethylene terephthalate. It is preferable that the surface is subjected to silicone treatment or the like as necessary. The thickness of the release film is usually 10 to 200 μm. Preferably it is 30-100 micrometers.

The polymer having a group capable of reacting with an isocyanate group used in the present invention is not particularly limited as long as it is a polymer having a group capable of reacting with an isocyanate group such as a hydroxyl group, an amino group, a carboxyl group, and an amide group. An acrylic pressure-sensitive adhesive polymer of a copolymer obtained by emulsion polymerization of an acrylic acid alkyl ester monomer unit (A) and a monomer unit (B) having a functional group capable of reacting with an isocyanate group is preferred. It is further preferable that the functional group of the monomer unit (B) can react with the crosslinking agent. When used as a solution, the acrylic pressure-sensitive adhesive polymer is separated from the emulsion liquid obtained by emulsion polymerization by salting out and then re-dissolved with a solvent, etc., but the acrylic pressure-sensitive adhesive polymer has a sufficient molecular weight. In the case where the solubility in the solvent is low or not dissolved, it is preferable to use the emulsion liquid as it is from the viewpoint of cost.
Hereinafter, the polymer having a group capable of reacting with an isocyanate group will be described in detail by taking an acrylic adhesive polymer as an example.

Acrylic pressure-sensitive adhesive polymer is a copolymer of a monomer composition containing a main monomer (hereinafter referred to as monomer (A)) and a monomer (B) having a functional group, alkyl acrylate ester, alkyl methacrylate ester, or a mixture thereof. Is obtained.
Examples of the monomer (A) include acrylic acid alkyl esters or methacrylic acid alkyl esters having an alkyl group having about 1 to 18 carbon atoms (hereinafter collectively referred to as (meth) acrylic acid alkyl esters). Preferably, it is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms. Specific examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, and 2-ethylhexyl acrylate. These may be used alone or in combination of two or more. The amount of the monomer (A) used is usually preferably in the range of 10 to 98% by weight in the total amount of the polymerizable monomer that is the raw material of the pressure-sensitive adhesive polymer. More preferably, it is 70 to 95% by weight. By making the usage-amount of a monomer (A) into this range, the polymer which contains 10-98 weight% of (meth) acrylic-acid alkylester monomer units (A), Preferably 70-95 weight% is obtained.

  The monomer unit (B) having a functional group capable of reacting with an isocyanate group includes a carboxyl group-containing monomer such as acrylic acid and methacrylic acid; a hydroxyl group such as acrylic acid-2-hydroxyethyl and methacrylate-2-hydroxyethyl Monomers, amide group-containing monomers such as acrylamide and methacrylamide; and amino group-containing monomers such as tertiary-butylaminoethyl acrylate and tertiary-butylaminoethyl methacrylate. Preferred are acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, and the like, and monomers having a hydroxy group are particularly preferred. One of these may be copolymerized with the main monomer (A), or two or more may be copolymerized. It is preferable that the amount of the monomer (B) having a functional group capable of reacting with an isocyanate group is usually contained in the range of 1 to 40% by weight in the total amount of the polymerizable monomer that is the raw material of the pressure-sensitive adhesive polymer. . More preferably, it is 1 to 30% by weight. Thus, a polymer having the structural unit (B) having a composition almost equal to the monomer composition is obtained.

  In the present invention, a specific comonomer having properties as a surfactant (hereinafter referred to as a polymerizable surfactant) may be copolymerized. The polymerizable surfactant has a property of copolymerizing with a main monomer and a comonomer, and also has an action as an emulsifier when emulsion polymerization is performed. When an acrylic pressure-sensitive adhesive polymer emulsion-polymerized using a polymerizable surfactant is used, the surface of the wafer is usually not contaminated by the surfactant. Even when slight contamination caused by the pressure-sensitive adhesive layer occurs, it can be easily removed by washing the wafer surface with water.

  Examples of such polymerizable surfactants include, for example, those obtained by introducing a polymerizable 1-propenyl group into the benzene ring of polyoxyethylene nonylphenyl ether [Daiichi Kogyo Seiyaku Co., Ltd .; trade name: Aqualon RN-10, RN-20, RN-30, RN-50, etc.], polyoxyethylene nonylphenyl ether sulfate ester ammonium salt introduced with a polymerizable 1-propenyl group on the benzene ring [first Manufactured by Kogyo Seiyaku Co., Ltd .; trade names: Aqualon HS-10, HS-20, etc.], and sulfosuccinic acid diester system having a polymerizable double bond in the molecule [manufactured by Kao Corporation; trade name: Latemul S -120A, S-180A, etc.].

  Further, if necessary, a monomer having a polymerizable double bond such as vinyl acetate, acrylonitrile, or styrene may be copolymerized. The amount of the surfactant used is from 0.1% by weight to 5% by weight, preferably from 0.2% by weight to 2% by weight, based on 100 parts by weight of the monomer raw material.

  Examples of the polymerization reaction mechanism of the acrylic pressure-sensitive adhesive polymer include radical polymerization, anionic polymerization, and cationic polymerization. Polymerization by radical polymerization is preferable in consideration of the production cost of the pressure-sensitive adhesive, the influence of the functional group of the monomer, the influence of ions on the surface of the semiconductor wafer, and the like. When polymerizing by radical polymerization reaction, organic compounds such as benzoyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, di-tertiary-butyl peroxide, di-tertiary-amyl peroxide as radical polymerization initiators Inorganic peroxides such as peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 4,4 Examples include azo compounds such as' -azobis-4-cyanovaleric acid.

  In the case of polymerization by emulsion polymerization method, among these radical polymerization initiators, inorganic peroxides such as water-soluble ammonium persulfate, potassium persulfate, and sodium persulfate, and water-soluble 4,4′-azobis are also used. An azo compound having a carboxyl group in the molecule such as -4-cyanovaleric acid is preferred. Considering the influence of ions on the surface of the semiconductor wafer, azo compounds having a carboxyl group in the molecule such as ammonium persulfate and 4,4′-azobis-4-cyanovaleric acid are more preferable. An azo compound having a carboxyl group in the molecule such as 4,4′-azobis-4-cyanovaleric acid is particularly preferable.

  A cross-linking agent having two or more cross-linkable functional groups in one molecule is preferably used because the adhesive force and cohesive force can be adjusted by reacting with the functional group of the acrylic pressure-sensitive adhesive polymer. As crosslinking agents, epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, resorcin diglycidyl ether, etc. , Tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane toluene diisocyanate triadduct, isocyanate compounds such as polyisocyanate, trimethylolpropane-tri-β-aziridinyl propionate, tetramethylolmethane-tri-β- Aziridinyl propionate, N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxyamino ), N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-toluene-2,4-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β Examples include aziridin compounds such as-(2-methylaziridine) propionate and melamine compounds such as hexamethoxymethylol melamine. These may be used alone or in combination of two or more.

  The content of the cross-linking agent is preferably contained in such a range that the sum of the number of functional groups in the cross-linking agent and the number of functional groups in the blocked isocyanate does not exceed the number of functional groups in the acrylic pressure-sensitive adhesive polymer. However, when a functional group is newly generated by the crosslinking reaction, or when the crosslinking reaction is slow, it may be contained excessively as necessary. A preferred content is 0.1 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the acrylic pressure-sensitive adhesive polymer. When the content is small, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient, and adhesive residue due to the pressure-sensitive adhesive layer tends to occur on the wafer surface (especially in the case of a wafer having a high bump electrode). When the adhesive film is peeled off from the wafer surface, there may be a case where an automatic peeling machine causes a peeling trouble or the wafer is completely damaged. If the content is high, the adhesive force between the adhesive layer and the wafer surface will be weak, and water and grinding debris may enter during grinding and damage the wafer, or the wafer surface may be contaminated by grinding debris. is there.

The pressure-sensitive adhesive coating solution contains at least two blocked polyisocyanates whose isocyanate groups can be regenerated by thermal dissociation in one molecule. Blocked polyisocyanates that thermally dissociate at 100 ° C. or higher and lower than 250 ° C., more preferably 110 ° C. or higher and lower than 200 ° C. are preferred. As the blocked polyisocyanate, a known blocked polyisocyanate can be used. For example, the isocyanate group of a bifunctional isocyanate compound is blocked with a compound having active hydrogen, or a polyisocyanate compound is reacted with a trihydric alcohol such as trimethylolpropane, and the remaining isocyanate group of the resulting compound is converted to active hydrogen. And the like blocked with a compound or the like.
The content of the blocked polyisocyanate is preferably contained in a range such that the sum of the number of functional groups in the blocked polyisocyanate and the number of functional groups in the crosslinking agent does not exceed the number of functional groups in the acrylic pressure-sensitive adhesive polymer. . However, when a functional group is newly generated by the crosslinking reaction, or when the crosslinking reaction is slow, it may be contained excessively as necessary. The preferred content is 0.1 to 50 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the acrylic pressure-sensitive adhesive polymer.

In the above-mentioned blocked polyisocyanate-containing pressure-sensitive adhesive, the isocyanate group is regenerated by heating and reacts with the functional group of the acrylic pressure-sensitive adhesive polymer, so that the elastic modulus is remarkably increased and the pressure-sensitive adhesive strength is greatly reduced.
In addition, the adhesive coating solution used in the present invention appropriately contains rosin-based, terpene resin-based tackifiers, various surfactants, etc., in order to adjust the adhesive properties, so as not to affect the purpose of the present invention. May be. When the coating solution is an emulsion solution, a film-forming aid such as diethylene glycol monoalkyl ether may be added as appropriate so as not to affect the purpose of the present invention. Considering that diethylene glycol monoalkyl ether and its derivatives used as film-forming aids may cause contamination of the wafer surface to the extent that cleaning is impossible when contained in a large amount in the pressure-sensitive adhesive layer. It is preferable to use a material that volatilizes at the drying temperature after the pressure-sensitive adhesive coating, and to reduce the residual amount in the pressure-sensitive adhesive layer.

  The thickness of the pressure-sensitive adhesive layer is preferably 3 to 100 μm. A more preferred thickness is 5 to 80 μm. If the thickness of the pressure-sensitive adhesive layer is reduced, the water resistance will be inferior, and water will penetrate between the wafer surface and the pressure-sensitive adhesive layer during backside grinding, causing damage to the wafer or contamination of the wafer surface by grinding debris. Tend to. When the thickness of the pressure-sensitive adhesive layer is increased, it may be difficult to produce a pressure-sensitive adhesive film, or the productivity may be affected, leading to an increase in manufacturing cost.

  As a method of grinding a semiconductor wafer using the adhesive tape for grinding a semiconductor wafer back surface of the present invention, for example, the following steps are used. First, the release film is peeled off from the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film, the pressure-sensitive adhesive layer surface is exposed, and the surface (surface) of the semiconductor wafer on which the integrated circuit is incorporated is attached via the pressure-sensitive adhesive layer. . Next, the semiconductor wafer is fixed to the chuck table or the like of the grinding machine via the base film layer of the adhesive film, and the back surface (the surface where the integrated circuit is not formed) of the semiconductor wafer is ground.

After grinding is completed, the adhesive tape is heated to reduce the adhesive strength. The heating temperature is equal to or higher than the thermal dissociation temperature of the blocked polyisocyanate compound, and preferably 10 ° C. or higher. The heating time is preferably 2 minutes to 60 minutes. By heating, the blocked polyisocyanate is dissociated, the isocyanate group is regenerated, the crosslinking reaction proceeds, and the adhesive strength is reduced.
Finally, the adhesive film is peeled from the semiconductor wafer. Since the adhesive force of the pressure-sensitive adhesive layer is reduced by the heating operation, the pressure-sensitive adhesive film can be easily peeled from the semiconductor wafer without damaging the wafer during peeling.

  Hereinafter, the present invention will be described in more detail with reference to examples. In all the examples and comparative examples shown below, the preparation and application of the adhesive coating solution and the backside grinding of the semiconductor silicon wafer in an environment maintained at a cleanness of class 1,000 or less as defined in US Federal Standard 209b Etc. were carried out. The present invention is not limited to these examples. Various characteristic values shown in the examples were measured by the following methods.

(1) Adhesive strength before heating (g / 25mm)
Except for the conditions specified below, all measurements are made in accordance with JIS Z-0237-1991. In an atmosphere of 23 ° C., the adhesive film obtained in the example or comparative example was attached to the surface of a 5 cm × 20 cm SUS304-BA board (JIS G-4305-1991 regulation) through the adhesive layer. Leave for 60 minutes. One end of the sample was clamped, the peeling angle was 180 degrees, and the peeling speed was 300 mm / min. Then, the stress at the time of peeling the sample from the surface of the SUS304-BA plate is measured and converted to an adhesive force of g / 25 mm.

(2) Adhesive strength after heating (g / 25mm)
Except for the conditions specified below, all measurements are made in accordance with JIS Z-0237-1991. In an atmosphere of 23 ° C., the adhesive film obtained in the example or comparative example was attached to the surface of a 5 cm × 20 cm SUS304-BA board (JIS G-4305-1991 regulation) through the adhesive layer. Leave for 60 minutes. Then, it is left on a plate heated to 200 ° C. for 2 minutes and cooled to room temperature. One end of the sample was clamped, the peeling angle was 180 degrees, and the peeling speed was 300 mm / min. Then, the stress at the time of peeling the sample from the surface of the SUS304-BA plate is measured and converted to an adhesive force of g / 25 mm.

(3) Semiconductor wafer breakage (number)
The semiconductor wafer is heated at 180 ° C. for 2 minutes with the adhesive film attached after the semiconductor wafer back surface grinding step, and the number of damaged semiconductor wafers in the surface protective adhesive film peeling step is shown.

(4) Adhesion (%)
An adhesive film for a sample is placed on the surface of a semiconductor silicon wafer (diameter: 6 inches, thickness: 600 μm, scribe line depth: 8 μm, scribe line width: 100 μm) with an integrated circuit interposed therebetween. In a state of being attached to the entire surface of the semiconductor silicon wafer, observation is performed at 250 magnifications using a laser focus microscope (manufactured by KEYENCE, model: VF-7510, VF-7500, VP-ED100) and photographed. For the adhesion evaluation, the ratio of the adhesive area to the scribe line and the total area of the scribe line is used as an index of adhesion, and the adhesive ratio to the scribe line is 70% or more. To do.
Example 1
<Polymerization of adhesive main agent>
In a polymerization reactor, deionized water 150 wt%, polymerization initiator 4,4′-azobis-4-cyanovaleric acid [manufactured by Otsuka Chemical Co., Ltd., trade name: ACVA] 0.625 parts by weight, monomer ( A) 74.3 parts by weight of 2-ethylhexyl acrylate, 13.7 parts by weight of methyl methacrylate, 9 parts by weight of 2-hydroxyethyl methacrylate, 2 parts by weight of methacrylic acid, and 1 part by weight of acrylamide 1 part of the benzene ring of the ammonium salt of polyoxyethylene nonylphenyl ether (average value of the number of moles of ethylene oxide added: about 20) as a water-soluble comonomer [1st. Kogyo Seiyaku Co., Ltd., trade name: AQUALON HS-10] at 0.75 part by weight, with stirring at 70-72 ° C. Emulsion polymerization was carried out for 8 hours to obtain an acrylic resin emulsion. This was neutralized with 9% by weight aqueous ammonia (pH = 7.0) to obtain an acrylic pressure-sensitive adhesive polymer (pressure-sensitive adhesive main agent) having a solid content of 42.5% by weight.

<Preparation of adhesive coating solution>
100 parts by weight of the resulting pressure-sensitive adhesive main agent was sampled, and 5.0 parts by weight of an epoxy-based crosslinking agent [manufactured by Nagase Kasei Kogyo Co., Ltd., trade name: Denacol Ex-614] and blocked polyisocyanate [manufactured by Takeshi Mitsui Polychemicals] , Trade name: Takenate WB-920] was added to obtain 10 parts by weight of an adhesive coating solution.

<Production of adhesive film>
The pressure-sensitive adhesive coating solution was applied to a polypropylene film (release film, thickness: 50 μm) using a roll coater, and dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 20 μm. The pressure-sensitive adhesive layer was transferred by attaching and pressing the corona-treated surface to a PET film having a corona-treated surface on one side. After the transfer, the film was heated at 60 ° C. for 48 hours, and then cooled to room temperature to produce an adhesive film for grinding a semiconductor wafer back surface. The measurement results are shown in [Table 1].
Comparative Example 1
A pressure-sensitive adhesive film for grinding a semiconductor wafer back surface having a pressure-sensitive adhesive layer thickness of 20 μm was prepared by the same method as in Example 1 except that the blocked polyisocyanate was not used for the same pressure-sensitive adhesive main component as in Example 1. Produced. The adhesive properties of the obtained adhesive film were evaluated using the same method as in the examples. The measurement and evaluation results are shown in [Table 1].

Claims (4)

An adhesive layer is formed on at least one surface of the base film,
The pressure-sensitive adhesive layer contains a blocked polyisocyanate having at least two blocked isocyanate groups and a polymer having a group capable of reacting with an isocyanate group, in which an isocyanate group can be regenerated by thermal dissociation in one molecule. Characteristic adhesive film.   The pressure-sensitive adhesive film according to claim 1, wherein the polymer having a group capable of reacting with an isocyanate group is a vinyl polymer having at least one hydroxyl group in one molecule.   The pressure-sensitive adhesive film according to claim 1 or 2, wherein at least one layer of the base film is formed of a resin having a melting point of 200 ° C or higher. The first step of adhering the adhesive film according to claim 1 to a circuit forming surface of the semiconductor wafer, sequentially carrying out the second step of processing the non-circuit-formed surface of the semiconductor wafer, then, A method for protecting a semiconductor wafer in a manufacturing process of a semiconductor wafer, comprising performing a third step of peeling the adhesive film after heating to a temperature higher than the thermal dissociation temperature of the blocked isocyanate.