JP2011026615A - Surface treatment method for masking tape and wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a masking tape with excellent adhesive power at ordinary temperature capable of exerting a high adhesive power in high temperature water of 80-100°C and to be removed easily after use. <P>SOLUTION: The masking tape comprises a substrate and an adhesive layer formed on one side of the substrate, is capable of exerting a high adhesive power even in high temperature water of 80-100°C and is to be removed easily after use. The adhesive layer includes a copolymer having at least a segment derived from an alkylacrylate having a 5C or less alkyl group, a segment derived from an acrylic monomer having a 80-120°C glass transition temperature of a homopolymer, and a segment having a radically polymerizable unsaturated bond in the side chain, and having a -5 to 15°C glass transition temperature. The content of the segment derived from an alkylacrylate having a 5C or less alkyl group in the copolymer is 40 wt.% or more, and the content of the segment having a radically polymerizable unsaturated bond in the side chain is 0.1 meq/g or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a masking tape that has excellent adhesive strength at room temperature, exhibits high adhesive strength even in high-temperature water at 80 to 100 ° C., and can be easily peeled off after use. The present invention also relates to a wafer surface treatment method capable of easily and reliably protecting the wafer surface during plating.

In the manufacture of semiconductor wafers, a metal film made of nickel, gold, or the like on one side of the wafer is used for the purpose of improving adhesion between aluminum pads and wiring wires, improving adhesion when mounting solder balls, and preventing solder diffusion. Barrier metal) is formed. Such a barrier metal has been formed by a dry processing method such as sputtering.
In recent years, since higher reliability has been required for semiconductor devices, it has been required to increase the thickness of the barrier metal. However, in order to form a thick barrier metal by the conventional dry processing method, there are problems in terms of cost and work efficiency. Therefore, a wet processing method capable of forming a thick barrier metal more easily has been studied.

Typical wet treatment methods include plating methods such as electroless plating and electrolytic plating. According to the plating method, a relatively thick barrier metal can be easily formed. However, in the plating method, a step of immersing the entire wafer in a plating bath is essential. Due to this dipping process, the other surface of the wafer may be contaminated with the plating solution, or in some cases, the other surface of the wafer may be plated, causing a decrease in yield.

A resist method has been proposed as a method for protecting the surface to be prevented from contacting with the plating solution (for example, Patent Document 1). That is, by coating a liquid resist on one side of the wafer in advance by spin coating or the like before the plating step and curing the resist, one side of the wafer can be reliably protected. However, in order to completely remove the resist after the plating process, there is a problem that a complicated resist removing process using a solvent or the like is required.

JP-A-5-206064

On the other hand, the inventor considered to protect one side of the wafer with a masking tape. If the masking tape is used, it can be expected that one side of the wafer is easily protected without troublesome operations. However, in order to form a thick barrier metal by plating, it is necessary to immerse the wafer in a relatively high temperature plating solution at 80 to 100 ° C. Even if a conventionally known masking tape used for lead frame plating protection is diverted, the adhesive strength is remarkably reduced in high-temperature water at 80 to 100 ° C. and peels off during the plating process. In particular, in order to perform uniform plating, it is necessary to perform stirring while the wafer is immersed in a plating bath. However, the masking tape is more easily peeled off by the stirring. For such a problem, it was considered to increase the glass transition temperature of the pressure-sensitive adhesive layer of the masking tape to improve the high-temperature adhesive force, but in this case, the adhesive strength at room temperature is reduced. There was a problem that it was difficult to mask correctly. Furthermore, it is required that the wafer can be easily peeled after the plating process so as not to break the wafer.
An object of this invention is to provide the masking tape which is excellent in the adhesive force in normal temperature, exhibits high adhesive force also in the high temperature water of 80-100 degreeC, and can peel easily after use. Another object of the present invention is to provide a wafer surface treatment method capable of easily and reliably protecting the wafer surface during plating.

The present invention comprises a base material and a pressure-sensitive adhesive layer formed on one surface of the base material, exhibits high adhesive force even in high-temperature water at 80 to 100 ° C., and can be easily peeled off after use. A masking tape, wherein the pressure-sensitive adhesive layer comprises at least a segment derived from an alkyl acrylate ester having an alkyl group having 5 or less carbon atoms, and an acrylic monomer having a homopolymer having a glass transition temperature of 80 to 120 ° C. And a segment having a radically polymerizable unsaturated bond in the side chain, and having a glass transition temperature of -5 to 15 ° C, the alkyl group in the copolymer The content of the segment derived from the alkyl acrylate ester having 5 or less carbon atoms is 40% by weight or more, and the content of the segment having a radical polymerizable unsaturated bond in the side chain There is a masking tape is 0.1meq / g or more.
The present invention is described in detail below.

The present inventor has studied the pressure-sensitive adhesive layer of the masking tape, has as its main component a segment derived from an alkyl acrylate ester having an alkyl group having 5 or less carbon atoms, and a glass transition temperature of the homopolymer of 80 to 120 ° C. The masking tape using the pressure-sensitive adhesive layer containing a copolymer having a glass transition temperature adjusted to a certain range by copolymerizing a segment derived from an acrylic monomer, has an adhesive strength at room temperature and a temperature of 80 to 100 ° C. It was found that the adhesive strength in high temperature water can be compatible. Furthermore, by copolymerizing the copolymer with a segment having a radical polymerizable unsaturated bond in the side chain, it was found that it can be easily peeled off simply by irradiating ultraviolet rays or the like, and the present invention is completed. It came.

The masking tape of this invention consists of a base material and the adhesive layer formed in the one surface of this base material.
Although the said base material is not specifically limited, It is preferable that it is what permeate | transmits or passes light, for example, transparent, such as an acryl, an olefin, a polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, a polyimide. Examples thereof include a sheet made of resin, a sheet having a network structure, and a sheet having holes.

The base material has a tensile strength of 60 N or less at an elongation of 20% when a tensile test is performed on a sample having a width of 10 mm and a length of 15 cm using a tensile tester at 80 ° C. and a chucking distance of 10 cm. A base material (hereinafter also referred to as “flexible base material”) is preferable. When such a flexible substrate is used, even if the wafer with the masking tape attached is plated in a plating bath at about 80 ° C., the masking tape is hardly peeled off.
The present inventor has studied an aspect in which the masking tape peels from the wafer in high-temperature water at about 80 ° C. As a result, it has been found that there is a cause in the stress generated between the wafer and the masking tape when immersed in a plating bath at about 80 ° C. That is, when the wafer with the masking tape attached is immersed in a plating bath at about 80 ° C., the member tends to expand with a rapid temperature change. The base material of the masking tape, the pressure-sensitive adhesive layer, and the wafer have different coefficients of thermal expansion, and therefore have different expansion coefficients when the temperature changes. Due to the difference in expansion coefficient, stress is generated at each interface. Further, in order to perform uniform plating, it is necessary to stir the wafer while being immersed in the plating bath. However, a water flow hits the masking tape portion protruding from the wafer by the stirring, and the masking tape and the wafer are in contact with each other. In the meantime, peeling stress occurs.
As a result of intensive studies, the inventor used a substrate having a tensile strength of not more than a certain value when a tensile test was performed under a certain condition as a masking tape substrate in a plating bath of about 80 ° C. It has been found that the stress generated between the wafer and the masking tape when relaxed can be relaxed to suppress peeling. This is because a flexible base material that satisfies the above conditions can be used to relieve the stress generated due to the difference in expansion coefficient, and the peeling pressure generated even when a water flow strikes the masking tape portion that protrudes from the wafer during stirring. Is considered to be smaller.

The lower limit of the tensile strength of the flexible base material is not particularly limited, but when a sample having a width of 10 mm and a length of 15 cm is subjected to a tensile test with a tensile tester at 80 ° C. and a chucking distance of 10 cm, the sample is stretched. It is preferable that the tensile strength at a rate of 20% is 0.1 N or more. If the tensile strength under the above conditions is less than 0.1 N, it becomes difficult to substantially maintain the shape as a substrate.

The said flexible base material can adjust the tensile strength on the said conditions to 60 N or less by selecting the material which comprises a base material, and the thickness of a base material.
Although the material which comprises the said flexible base material is not specifically limited, Since it is flexible and can achieve desired tensile strength even if it is comparatively thick, for example, a polyethylene terephthalate (PET), polyethylene, a polypropylene, ethylene-acetic acid A vinyl copolymer (EVA), a polyimide, vinyl chloride, etc. are mentioned.
What is necessary is just to adjust suitably the thickness of the said flexible base material so that the tensile strength on the said conditions may be 60 N or less according to a material.

A masking tape comprising a base material and a pressure-sensitive adhesive layer formed on one surface of the base material and exhibiting high adhesive force even in high-temperature water at 80 to 100 ° C., the base material having a width of 10 mm and a length A masking tape having a tensile strength of 60 N or less at an elongation of 20% when a tensile test is performed on a 15 cm long sample with a tensile tester at 80 ° C. and a chucking distance of 10 cm is also the present invention. It is one of.

The base material is preferably a base material having an oxygen permeability measured by a method according to JIS K 7126 of 9 cc / m ² / hr / atm or less (hereinafter also referred to as “low oxygen permeability base material”). When such a low oxygen permeability base material is used, the masking tape is not easily peeled off even when the wafer with the masking tape attached is plated in a plating bath at about 80 ° C. It is possible to prevent the occurrence of electrical defects in the semiconductor wafer obtained by performing the treatment.

One of the causes of the present inventor's peeling of the masking tape from the wafer in high-temperature water of about 80 ° C. is that the plating solution permeates the base material and reaches the pressure-sensitive adhesive layer, thereby reducing the adhesion to the wafer. I found. In addition, when a semiconductor wafer obtained by performing plating while protecting one side of the wafer with a masking tape is actually used as a device, an electrical failure such as a short circuit may occur. As a result of studying the cause of the occurrence of this electrical failure, the present inventors have found that not only the plating solution penetrates due to peeling of the tape, but also a small amount of anions contained in the plating solution, particularly chlorine ions, are masking tape or resist. It has been found that this is caused by the fact that it passes through and adheres to the electrode metal film formed on the protective surface.
As a result of further investigation, it was found that by making the oxygen permeability of the base material of the masking tape below a certain level, peeling in high-temperature water can be prevented and the occurrence of electrical defects due to permeation of chlorine ions can be prevented. It was.

When the oxygen permeability of the low oxygen permeability base material exceeds 9 cc / m ² / hr / atm, it is impossible to suppress the transmission of chlorine ions and the like, and the occurrence of electrical defects in the obtained semiconductor wafer is prevented. I can't. The oxygen permeability of the low oxygen permeability substrate is preferably 9 cc / m ² / hr / atm or less. If the oxygen permeability of the low oxygen permeability substrate is 9 cc / m ² / hr / atm or less, the occurrence of electrical defects in the semiconductor wafer can be sufficiently prevented under the general electroless plating conditions. Can do.
In addition, the current general electroless plating conditions are 70 to 90 ° C. and 30 to 90 minutes, but in order to give higher reliability to devices in the future, electroless plating is performed under more severe conditions. It is predicted that thick plating will be applied. Therefore, a more preferable upper limit of the oxygen permeability of the low oxygen permeability substrate is 1 cc / m ² / hr / atm. If the oxygen permeability of the low oxygen permeability substrate is 1 cc / m ² / hr / atm or less, it is possible to reliably prevent transmission of chlorine ions and the like even when electroless plating is performed under more severe conditions. It is possible to prevent the occurrence of electrical defects in the semiconductor wafer and to prevent the masking tape from peeling off during electroless plating.

As long as the said low oxygen permeability base material satisfy | fills the said oxygen permeability, it may consist of a single layer, or may consist of a several layer.
Examples of the low oxygen permeability substrate made of a single layer include a highly stretched polyethylene terephthalate film. The polyethylene terephthalate film originally has a relatively low oxygen permeability, but the oxygen permeability can be reduced to 9 cc / m ² / hr / atm or less by performing a high stretching treatment.

Examples of the low oxygen permeability substrate composed of a plurality of layers include a film obtained by laminating a layer that prevents permeation of oxygen on a film made of an olefin resin such as polyethylene or polypropylene. Specifically, for example, a laminated film obtained by laminating a highly stretched polyethylene terephthalate film on a film made of an olefin resin, a vapor deposition film obtained by depositing a metal film or a silica film on a film made of an olefin resin, and the like can be given.

In the deposited film, the preferred lower limit of the thickness of the deposited layer is 5 nm, and the preferred upper limit is 300 nm. If the thickness of the vapor deposition layer is less than 5 nm, the oxygen transmission rate may not be sufficiently reduced, and if it exceeds 300 nm, the substrate may be hardened and easily peeled off. The minimum with more preferable thickness of the vapor deposition layer of the said vapor deposition film is 50 nm, and a more preferable upper limit is 200 nm.

A masking tape for protecting a non-plated surface during plating by an electroless plating method or an electrolytic plating method, comprising a base material and an adhesive layer formed on one surface of the base material, A masking tape whose material has an oxygen permeability of 9 cc / m ² / hr / atm or less measured by a method according to JIS K 7126 is also one aspect of the present invention.

The pressure-sensitive adhesive layer comprises a segment derived from an alkyl acrylate ester having an alkyl group having 5 or less carbon atoms, a segment derived from an acrylic monomer having a glass transition temperature of 80 to 120 ° C., and a side chain. Contains a copolymer having a segment having a radical polymerizable unsaturated bond (hereinafter, also simply referred to as “copolymer”).

A segment derived from an alkyl acrylate ester having 5 or less carbon atoms in the alkyl group serves as the base of the copolymer. Since the copolymer constituting the pressure-sensitive adhesive layer has a segment derived from an alkyl acrylate ester having an alkyl group with 5 or less carbon atoms, the masking tape of the present invention has high adhesion in high-temperature water at 80 to 100 ° C. Can demonstrate power.

Examples of the acrylic acid alkyl ester having 5 or less carbon atoms in the alkyl group include ethyl acrylate, methyl acrylate, butyl acrylate, isobutyl acrylate, and t-butyl acrylate. Of these, ethyl acrylate and methyl acrylate are preferred.

The minimum with preferable content of the segment derived from the acrylic acid alkylester whose carbon number of the said alkyl group in the said copolymer is 5 or less is 40 weight%, and a preferable upper limit is 90 weight%. When the content of the segment derived from an alkyl acrylate ester having 5 or less carbon atoms in the alkyl group is less than 40% by weight, sufficient cohesive strength of the adhesive at a high temperature of 80 to 90 ° C. cannot be obtained. If it exceeds 90% by weight, the stress relaxation force as a pressure-sensitive adhesive is reduced, and the adhesive strength may be impaired. The more preferable lower limit of the content of the segment derived from the alkyl acrylate ester having 5 or less carbon atoms in the alkyl group is 50% by weight, and the more preferable upper limit is 80% by weight.

A segment derived from an acrylic monomer having a glass transition temperature of 80 to 120 ° C. of the homopolymer has a role of adjusting the glass transition temperature of the copolymer. In the homopolymer of acrylic acid alkyl ester in which the carbon number of the alkyl group in the copolymer is 5 or less, the glass transition temperature is less than −20 ° C., and the necessary elastic modulus cannot be adjusted at high temperature. By copolymerizing a monomer having a glass transition temperature of 80 to 120 ° C. of the homopolymer, the glass transition temperature of the copolymer can be adjusted.

Examples of the monomer having a glass transition temperature of 80 to 120 ° C. of the homopolymer include methyl methacrylate, isobornyl acrylate, acrylonitrile, and acrylic acid. Of these, methyl methacrylate and acrylonitrile are preferable.

The content of the segment derived from the acrylic monomer having a glass transition temperature of the homopolymer of 80 to 120 ° C in the copolymer is appropriately determined so that the glass transition temperature of the copolymer is -5 to 15 ° C. Adjust it. In general, the preferable lower limit of the content of the segment derived from the acrylic monomer having a glass transition temperature of 80 to 120 ° C. of the homopolymer in the copolymer is 10% by weight, and the preferable upper limit is 40% by weight. . When the content of the segment derived from the acrylic monomer having a glass transition temperature of 80 to 120 ° C. of the homopolymer is less than 10% by weight, the cohesive force at a sufficiently high temperature may not be obtained. If it exceeds%, the adhesive strength may be significantly reduced. The more preferable lower limit of the content of the segment derived from the acrylic monomer having a glass transition temperature of 80 to 120 ° C. of the homopolymer is 15% by weight, and the more preferable upper limit is 35% by weight.

The segment having a radical polymerizable unsaturated bond in the side chain has a role of imparting photocurability to the copolymer. When the copolymer constituting the pressure-sensitive adhesive layer has a segment having a radical polymerizable unsaturated bond in the side chain, if the masking tape of the present invention is irradiated with light after the plating step, the pressure-sensitive adhesive layer is cured. To do. The cured pressure-sensitive adhesive layer can be easily peeled off because the elastic modulus is remarkably increased and most of the adhesive force is lost.

The method of inserting a segment having a radical polymerizable unsaturated bond in the side chain into the copolymer is, for example, copolymerizing an acrylic monomer having a functional group in the molecule and then reacting with the functional group. Examples thereof include a method of reacting with a compound having a functional group and a radical polymerizable unsaturated bond (hereinafter referred to as a functional group-containing unsaturated compound).

Examples of acrylic monomers having functional groups in the molecule include carboxyl group-containing monomers such as acrylic acid and methacrylic acid, hydroxyl group-containing monomers such as hydroxyethyl acrylate and hydroxyethyl methacrylate, glycidyl acrylate, and methacrylic acid. Examples thereof include epoxy group-containing monomers such as glycidyl acid, isocyanate group-containing monomers such as isocyanate ethyl acrylate and isocyanate ethyl methacrylate, and amino group-containing monomers such as aminoethyl acrylate and aminoethyl methacrylate.

Examples of the functional group-containing unsaturated compound include an epoxy group-containing monomer and an isocyanate group-containing monomer when the functional group of the acrylic monomer having a functional group in the molecule is a carboxyl group, and the functional group is a hydroxyl group. Is an isocyanate group-containing monomer, when the functional group is an epoxy group, a carboxyl group-containing monomer or an amide group-containing monomer such as acrylamide, and when the functional group is an amino group, an epoxy group-containing monomer is used. Can be mentioned.

The minimum with preferable content of the segment which has a radically polymerizable unsaturated bond in the said side chain in the said copolymer is 0.1 meq / g, and a preferable upper limit is 2 meq / g. If the content of the segment having a radical polymerizable unsaturated bond in the side chain is less than 0.1 meq / g, sufficient photocurability cannot be imparted and the masking tape cannot be peeled off even when irradiated with light. When it exceeds 2 meq / g, the cured adhesive may become brittle. The minimum with more preferable content of the segment which has a radically polymerizable unsaturated bond in the said side chain is 0.2 meq / g, and a more preferable upper limit is 1.5 meq / g.

The copolymer may contain a segment derived from another copolymerizable monomer within the range not impairing the object of the present invention. Examples of the other copolymerizable monomers include acrylic monomers having a side chain having 6 or more carbon atoms, such as 2-ethylhexyl acrylate, isooctyl acrylate, and cyclohexyl acrylate.

The pressure-sensitive adhesive layer preferably contains a gas generating agent that generates gas when irradiated with light. When the pressure-sensitive adhesive layer containing such a gas generating agent is irradiated with light, the copolymer is cross-linked and cured to increase the elastic modulus of the entire pressure-sensitive adhesive layer, and is generated in such a hard pressure-sensitive adhesive layer. Since the gas is released from the pressure-sensitive adhesive layer to the adhesion interface and peels at least part of the adhesion surface, the masking tape can be more easily peeled off.

Although the said gas generating agent is not specifically limited, For example, an azide compound, an azo compound, etc. are mentioned. Of these, an azide compound having excellent heat resistance is preferable.
The azide compound is not particularly limited. For example, glycidyl obtained by ring-opening polymerization of 3-azidomethyl-3-methyloxetane, terephthalazide, p-tert-butylbenzazide, 3-azidomethyl-3-methyloxetane. Examples thereof include a polymer having an azide group such as an azide polymer (GAP).

The pressure-sensitive adhesive layer preferably contains a photopolymerization initiator.
Examples of the photopolymerization initiator include those that are activated by irradiation with light having a wavelength of 250 to 800 nm. Examples of such a photopolymerization initiator include acetophenone derivative compounds such as methoxyacetophenone, benzoin ether compounds such as benzoin propyl ether and benzoin isobutyl ether, ketal derivative compounds such as benzyldimethyl ketal and acetophenone diethyl ketal, Phosphine oxide derivative compound, bis (η5-cyclopentadienyl) titanocene derivative compound, benzophenone, Michler ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenylpropane, etc. These radical photopolymerization initiators. These photoinitiators may be used independently and 2 or more types may be used together.

The pressure-sensitive adhesive layer preferably contains a polyfunctional oligomer or monomer. The polyfunctional oligomer or monomer has a role of improving curability when the copolymer is irradiated with light.
The polyfunctional oligomer or monomer preferably has a molecular weight of 10,000 or less, and more preferably has a molecular weight of 5, so that the three-dimensional network of the pressure-sensitive adhesive layer can be efficiently formed by heating or light irradiation. 000 or less and the number of radically polymerizable unsaturated bonds in the molecule is 2 to 20. Such more preferred polyfunctional oligomers or monomers are, for example, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or Examples thereof include the same methacrylates as described above. Other examples include 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, and methacrylates similar to those described above. These polyfunctional oligomers or monomers may be used alone or in combination of two or more.

The pressure-sensitive adhesive layer may appropriately contain various polyfunctional compounds that are blended in a general pressure-sensitive adhesive such as an isocyanate compound, a melamine compound, and an epoxy compound for the purpose of adjusting the cohesive force as the pressure-sensitive adhesive. In addition, known additives such as an antistatic agent, a plasticizer, a resin, a surfactant, a wax, and a fine particle filler can be added. Furthermore, you may mix | blend a heat stabilizer and antioxidant in order to improve stability of an adhesive.

The method for producing the masking tape of the present invention is not particularly limited. For example, a conventionally known method such as applying a pressure-sensitive adhesive containing the copolymer on the substrate using a doctor knife or a spin coater. Can be used.

Since the pressure-sensitive adhesive layer containing the copolymer is formed on one surface of the base material, the masking tape of the present invention has an adhesive strength at a plating temperature of 1 N / inch or more and is peeled off. The peeling force at the time can be 0.5 N / inch or less.
The masking tape of the present invention having such performance is excellent in adhesive strength at room temperature, exhibits high adhesive strength even in high-temperature water at 80 to 100 ° C., and can be easily peeled off after use. Therefore, if the masking tape of this invention is used, the surface treatment method of the wafer which can protect the surface of a wafer simply and reliably at the time of plating can be provided.

A step of applying a masking tape to the side where the circuit is not formed on a wafer having a circuit formed on one side, and a step of plating the wafer on which the masking tape is attached by an electrolytic plating method or an electroless plating method; A wafer surface treatment method comprising a step of peeling a masking tape from a wafer after plating, wherein the masking tape comprises a base material and an adhesive layer formed on one surface of the base material, and A surface treatment method for a wafer in which the adhesive layer has an adhesive strength at a plating temperature of 1 N / inch or more and a peeling force at the time of peeling of 0.5 N / inch or less is also one aspect of the present invention. .

The wafer surface treatment method of the present invention includes a step of applying a masking tape to a side of the wafer having a circuit formed on one side thereof, on which the circuit is not formed.
The masking tape is composed of a base material and an adhesive layer formed on one surface of the base material, and the adhesive layer has an adhesive strength of 1 N / inch or more at a plating temperature and is peeled off. The peel force is 0.5 N / inch or less. By using a masking tape having such performance, the masking tape may be peeled from the wafer even when a plating process including a step of immersing the wafer in a relatively high temperature plating solution at 80 to 100 ° C. is performed. Thus, the surface of the wafer can be reliably protected, and the masking tape that has become unnecessary after the plating process can be easily peeled off.

If the adhesive strength at the plating treatment temperature of the masking tape is less than 1 N / inch, the masking tape is peeled off during the plating treatment, and reliable protection cannot be performed. The adhesive strength at the plating temperature is preferably 1.5 N / inch or more.
In this specification, the adhesive strength at the plating treatment temperature is 180 ° peel measurement at the same temperature as the temperature of the plating bath (usually 80 to 100 ° C.) in the step of plating by the electrolytic plating method or the electroless plating method. It means the peeling force from the Si wafer measured by a method according to the method (JIS Z 0237).

If the peeling force at the time of peeling the masking tape exceeds 0.5 N / inch, it is difficult to peel the masking tape from the wafer, or the wafer may be damaged at the time of peeling. The peeling force at the time of peeling is preferably 0.2 N / inch or less.
In addition, in this specification, the peeling force at the time of peeling is a 180 ° peel measurement method at normal temperature (usually the temperature at which peeling is performed, about 23 ° C.) after giving a stimulus to reduce the adhesive strength of the masking tape described later. It means the peeling force from a Si wafer measured by a method according to (JIS Z 0237).

The masking tape used in the wafer surface treatment method of the present invention is particularly limited as long as the adhesive strength at the plating temperature is 1 N / inch or more and the peeling force at the time of peeling is 0.5 N / inch or less. Although not specifically, the masking tape of the present invention is suitable.

When applying the masking tape to the wafer, it is preferable to apply the masking tape so that the width of the protruding portion of the masking tape from the wafer is 2 mm or less. The smaller the width of the protruding portion, the smaller the portion that is exposed to the water flow when stirring is performed while immersed in the plating bath, and the generated peeling pressure is also reduced.

In the wafer surface treatment method of the present invention, a step of plating the wafer with the masking tape attached thereto by an electrolytic plating method or an electroless plating method is then performed. The said plating method is not specifically limited, A conventionally well-known method is mentioned.
In a normal plating method, the wafer is immersed in a relatively high temperature plating solution of 80 to 100 ° C. Since the adhesive strength at the plating processing temperature of the masking tape is 1 N / inch or more, the masking tape Can be reliably protected without peeling.

In the wafer surface treatment method of the present invention, a step of peeling the masking tape from the plated wafer is then performed. Since the peeling force when peeling the masking tape is 0.5 N / inch or less, peeling can be easily performed without damaging the wafer. In addition, when the said masking tape has an adhesive layer which consists of an adhesive which gave the device which reduces the adhesive force by giving the said irritation | stimulation, this irritation | stimulation is given prior to peeling.

ADVANTAGE OF THE INVENTION According to this invention, it is excellent in the adhesive force in normal temperature, exhibits high adhesive force also in high temperature water of 80-100 degreeC, and can provide the masking tape which can be peeled easily after use. ADVANTAGE OF THE INVENTION According to this invention, the surface treatment method of the wafer which can protect the surface of a wafer simply and reliably at the time of metal plating can be provided.

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

Example 1
(1) Preparation of pressure-sensitive adhesive The following compound was dissolved in ethyl acetate and polymerized by irradiating with ultraviolet rays to obtain an ethyl acetate solution of a photocurable pressure-sensitive adhesive made of a copolymer having a weight average molecular weight of 500,000.
Ethyl acrylate 75 parts by weight Methyl methacrylate 20 parts by weight Acrylic acid 3 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
Lauryl mercaptan 0.01 parts by weight

(2) Preparation of composition solution for pressure-sensitive adhesive layer The reaction was conducted by adding 3.5 parts by weight of 2-isocyanatoethyl methacrylate to 100 parts by weight of the resin solid content of the obtained ethyl acetate solution of the photocurable pressure-sensitive adhesive. Further, 5 parts by weight of a photopolymerization initiator (Irgacure 651) and 0.5 parts by weight of a polyisocyanate are mixed with 100 parts by weight of the resin solid content of the ethyl acetate solution after the reaction to form a composition solution for an adhesive layer. Was prepared.

(3) Production of masking tape The obtained pressure-sensitive adhesive layer composition solution was subjected to a corona treatment on a transparent polyethylene terephthalate (PET) film having a thickness of 75 μm with one side subjected to a corona treatment. Coating was performed with a doctor knife so as to be 15 μm, and the coating solution was dried by heating at 110 ° C. for 5 minutes. The pressure-sensitive adhesive layer after drying showed adhesiveness in a dry state. Next, a PET film that was subjected to a release treatment was attached to the surface of the pressure-sensitive adhesive layer. Thereafter, static curing was performed at 40 ° C. for 3 days to obtain a masking tape.

(Example 2)
The following compounds were dissolved in ethyl acetate and polymerized by irradiating with ultraviolet rays to obtain an ethyl acetate solution of a photocurable pressure-sensitive adhesive comprising a copolymer having a weight average molecular weight of 500,000.
Butyl acrylate 65 parts by weight Acrylonitrile 30 parts by weight Acrylic acid 3 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
0.01 parts by weight of lauryl mercaptan 0.01 parts by weight of resin solid content of ethyl acetate solution of the above photocurable adhesive is added with 3.5 parts by weight of 2-isocyanatoethyl methacrylate and further reacted. 10 parts by weight of glycidyl azide polymer (GAP5003, manufactured by NOF Corporation), 5 parts by weight of a photopolymerization initiator (Irgacure 651), and 1.0 part by weight of polyisocyanate with respect to 100 parts by weight of the resin solid content of the ethyl acetate solution The mixture was mixed to prepare an ethyl acetate solution of an adhesive for gas generating adhesive layer.
A masking tape was obtained in the same manner as in Example 1 except that the obtained ethyl acetate solution of the pressure-sensitive adhesive for gas generating pressure-sensitive adhesive layer was used.

(Example 3)
The following compounds were dissolved in ethyl acetate and polymerized by irradiating with ultraviolet rays to obtain an ethyl acetate solution of a photocurable pressure-sensitive adhesive comprising a copolymer having a weight average molecular weight of 500,000.
Ethyl acrylate 77 parts by weight Methyl methacrylate 19 parts by weight Acrylic acid 2 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
Lauryl mercaptan 0.01 parts by weight

Example 4
To 100 parts by weight of the resin solid content of the ethyl acetate solution of the photocurable adhesive obtained in Example 3, 3.5 parts by weight of 2-isocyanatoethyl methacrylate was added and reacted. 10 parts by weight of glycidyl azide polymer (GAP5003, manufactured by NOF Corporation), 2 parts by weight of a photopolymerization initiator (Irgacure 651), and 1.0 part by weight of polyisocyanate are mixed with 100 parts by weight of resin solids in an ethyl solution. Then, an ethyl acetate solution of the pressure-sensitive adhesive for gas generating pressure-sensitive adhesive layer was prepared.
A masking tape was obtained in the same manner as in Example 3 except that the ethyl acetate solution of the obtained gas generating pressure-sensitive adhesive layer was used.

(Example 5)
To 100 parts by weight of the resin solid content of the ethyl acetate solution of the photocurable adhesive obtained in Example 3, 3.5 parts by weight of 2-isocyanatoethyl methacrylate was added and reacted. For 100 parts by weight of the resin solid content of the ethyl solution, 10 parts by weight of thermally foamed fine particles (ADVANCEL EMH403, manufactured by Sekisui Chemical Co., Ltd.) and 1.0 part by weight of polyisocyanate are mixed to form a thermally foamable pressure-sensitive adhesive layer. An ethyl acetate solution of an adhesive was prepared.
A masking tape was obtained in the same manner as in Example 3 except that the ethyl acetate solution of the obtained adhesive for heat-foaming pressure-sensitive adhesive layer was used.

(Comparative Example 1)
A commercially available masking tape (manufactured by Sekisui Chemical Co., Ltd., $ 6364F) was prepared for lead frame plating protection.

(Comparative Example 2)
The following compounds were dissolved in ethyl acetate and polymerized by irradiating with ultraviolet rays to obtain an ethyl acetate solution of a photocurable pressure-sensitive adhesive comprising a copolymer having a weight average molecular weight of 500,000.
Ethyl acrylate 73 parts by weight Methyl methacrylate 15 parts by weight Acrylic acid 10 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
0.01 parts by weight of lauryl mercaptan After that, a composition solution for an adhesive layer was prepared in the same manner as in Example 3, and then a masking tape was produced.

(Comparative Example 3)
The following compounds were dissolved in ethyl acetate and polymerized by irradiating with ultraviolet rays to obtain an ethyl acetate solution of a photocurable pressure-sensitive adhesive comprising a copolymer having a weight average molecular weight of 500,000.
Ethyl acrylate 45 parts by weight 2-ethylhexyl acrylate 45 parts by weight methyl methacrylate 6 parts by weight Acrylic acid 2 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
0.01 parts by weight of lauryl mercaptan After that, a composition solution for an adhesive layer was prepared in the same manner as in Example 3, and then a masking tape was produced.

(Evaluation)
About the masking tape manufactured by the Example and the comparative example, it evaluated by the following method.
The results are shown in Table 1.

(1) Evaluation of initial adhesive strength The adhesive tapes obtained in Examples and Comparative Examples were cut into 25 mm × 100 mm and then bonded to a Si wafer. After leaving at 23 ° C. for 20 minutes, the initial adhesive strength was measured by a method according to the 180 ° peel measurement method defined in JIS Z 0237.

(2) Evaluation of adhesive strength at 90 ° C. The adhesive tapes obtained in Examples and Comparative Examples were cut into 25 mm × 100 mm and then bonded to a Si wafer. After leaving at 23 ° C. for 20 minutes, the wafer was heated to 90 ° C. with a masking tape attached thereto, and in that state, the adhesive strength was measured by a method according to the 180 ° peel measurement method defined in JIS Z 0237.

(3) Plating bath immersion test After the adhesive tapes obtained in Examples and Comparative Examples were cut, they were bonded to one side of a Si wafer having a diameter of 150 mm, and then allowed to stand at 23 ° C. for 20 minutes. Thereafter, it was immersed in an electroless Ni plating solution (pH 5) kept at 90 ° C. for 60 minutes. After immersion, the gap between the wafer edge and the tape was visually observed to evaluate the presence or absence of plating solution penetration.
After plating, the wafer with the masking tape attached was taken out and dried at room temperature for 1 hour. After drying, the masking tape obtained in Examples and Comparative Examples was applied with the masking tape obtained in Examples 1, 2, 3, and 4 and Comparative Examples 2 and 3 in a state where the masking tape was applied to the wafer. The resulting sample was irradiated with 2000 mJ / cm ² of ultraviolet rays from the substrate side of the masking tape. The masking tape obtained in Example 5 was heated at 130 ° C. for 5 minutes with the masking tape attached to the wafer. After the ultraviolet irradiation, the masking tape was peeled off, and the surface of the wafer was visually observed to evaluate the presence or absence of adhesive residue. With respect to the masking tape obtained in Comparative Example 1, the masking tape was peeled off without performing ultraviolet irradiation, and the surface of the wafer was visually observed to evaluate the presence or absence of adhesive residue.

(Experimental example 1)
(1) Preparation of pressure-sensitive adhesive The following compound was dissolved in ethyl acetate and polymerized by irradiating ultraviolet rays to obtain an ethyl acetate solution of a photocurable pressure-sensitive adhesive made of a copolymer having a weight average molecular weight of 300,000.
Ethyl acrylate 75 parts by weight Methyl methacrylate 20 parts by weight Acrylic acid 3 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
Lauryl mercaptan 0.01 parts by weight

(2) Preparation of composition solution for pressure-sensitive adhesive layer The reaction was conducted by adding 3.5 parts by weight of 2-isocyanatoethyl methacrylate to 100 parts by weight of the resin solid content of the obtained ethyl acetate solution of the photocurable pressure-sensitive adhesive. Further, 5 parts by weight of a photopolymerization initiator (Irgacure 651) and 0.5 parts by weight of a polyisocyanate are mixed with 100 parts by weight of the resin solid content of the ethyl acetate solution after the reaction to form a composition solution for an adhesive layer. Was prepared.

(3) As a masking tape manufacturing base material, a transparent polyethylene terephthalate (PET) film having a thickness of 38 μm with a corona treatment on one side (a sample having a width of 10 mm and a length of 15 cm, conditions of 80 ° C. and a chucking distance of 10 cm) When a tensile test was performed with a tensile tester below, the tensile strength at an elongation rate of 20% was 60 N, and a transparent polyethylene terephthalate (PET) film having a thickness of 50 μm with a corona treatment on one side (width 10 mm, When a tensile test was performed on a sample having a length of 15 cm with a tensile tester under conditions of 80 ° C. and a chucking distance of 10 cm, the tensile strength at an elongation rate of 20% was 200 N), and one side was subjected to corona treatment. Transparent polypropylene film with a thickness of 75 μm (10 mm wide, 15 cm long sample, chucked at 80 ° C. When subjected to tensile test at a tensile tester under the conditions of the release 10 cm, tensile strength at elongation of 20% was prepared three 25 N).
The obtained pressure-sensitive adhesive layer composition solution was coated with a doctor knife on the corona treatment of each substrate so that the dry film thickness was about 15 μm, and heated at 110 ° C. for 5 minutes to give a coating solution. Dried. The pressure-sensitive adhesive layer after drying showed adhesiveness in a dry state. Next, a PET film that was subjected to a release treatment was attached to the surface of the pressure-sensitive adhesive layer. Thereafter, static curing was performed at 40 ° C. for 3 days to obtain a masking tape.

(4) Evaluation After the obtained masking tape was cut into a certain size, the PET film that had been subjected to the mold release treatment was peeled off and attached to one side of a silicon wafer having a diameter of 20 cm and a thickness of 200 μm. At this time, the width of the protruding portion of the masking tape from the wafer was set to 0, 0.5, 1, 2, and 5 mm.
The entire wafer with the masking tape attached was immersed in a plating bath at 80 ° C. and stirred at a stirring speed of 300 rpm for 60 minutes. After the stirring was completed, the wafer was taken out and peeling of the masking tape was confirmed.
This experiment was performed 10 times for each masking tape and the width of the protruding portion, and the number of occurrences of peeling of the masking tape was counted.
The results are shown in Table 2.

(Experimental example 2)
(1) Preparation of photocurable pressure-sensitive adhesive The following compounds are dissolved in ethyl acetate, polymerized by irradiating ultraviolet rays, and an ethyl acetate solution of a photocurable pressure-sensitive adhesive made of a copolymer having a weight average molecular weight of 500,000 is prepared. Obtained.
Ethyl acrylate 75 parts by weight Methyl methacrylate 20 parts by weight Acrylic acid 3 parts by weight 2-hydroxyethyl acrylate 2 parts by weight Photopolymerization initiator 1 part by weight (Irgacure 651, 50% ethyl acetate solution)
Lauryl mercaptan 0.01 parts by weight

(2) Preparation of composition solution for pressure-sensitive adhesive layer The reaction was conducted by adding 3.5 parts by weight of 2-isocyanatoethyl methacrylate to 100 parts by weight of the resin solid content of the obtained ethyl acetate solution of the photocurable pressure-sensitive adhesive. Further, 5 parts by weight of a photopolymerization initiator (Irgacure 651) and 0.5 parts by weight of a polyisocyanate are mixed with 100 parts by weight of the resin solid content of the ethyl acetate solution after the reaction to form a composition solution for an adhesive layer. Was prepared.

(3) As a base material for manufacturing the masking tape, a corona-treated one side of a 50 μm thick highly stretched polyethylene terephthalate film (manufactured by Teijin DuPont, Teijin Tetron Film SL) was prepared. With respect to this highly stretched polyethylene terephthalate film, the oxygen transmission rate was measured by a method according to JIS K 7126. As a result, it was 7.0 cc / m ² / hr / atm.
On the corona-treated surface of the above-mentioned highly stretched polyethylene terephthalate film, apply the obtained pressure-sensitive adhesive layer composition solution with a doctor knife so that the dry film thickness is about 15 μm, and heat at 110 ° C. for 5 minutes. The working solution was dried. The pressure-sensitive adhesive layer after drying showed adhesiveness in a dry state. Next, a PET film that was subjected to a release treatment was attached to the surface of the pressure-sensitive adhesive layer. Thereafter, static curing was performed at 40 ° C. for 3 days to obtain a masking tape.
As a base material, “a base material having a corona treatment on one side of a 12 μm thick silica-deposited polyethylene terephthalate film (Mitsubishi Resin, Tech Barrier VX, oxygen permeability is 0.3 cc / m ² / hr / atm)” , “Aluminum-deposited polyethylene terephthalate film having a thickness of 12 μm (Hitapac VM-PET, manufactured by Hitachi IC Corporation, oxygen transmission rate is 0.1 cc / m ² / hr / atm)”, “Polyethylene film having a thickness of 50 μm and thickness A base material obtained by laminating and laminating a 12 μm highly stretched polyethylene terephthalate film (oxygen permeability is 9.0 cc / m ² / hr / atm) and corona-treated on one side ”,“ 50 μm thick aluminum deposited polyethylene film (oxygen permeability ^{0.2cc / m 2 / hr / atm} ) substrate was corona-treated on one side of the ""Unstretched polyethylene terephthalate film having a thickness of 50μm one side based on the corona treated material (Toray Advanced Film Co., Toyofuron, oxygen permeability ^{15.0cc / m 2 / hr / atm} ) ", "the thickness of 75μm A masking tape was obtained by the same method except that a substrate having a polyethylene film (oxygen permeability of 250 cc / m ² / hr / atm) was used.

(Evaluation)
The obtained masking tape was evaluated by the following method. The results are shown in Table 3.

(1) Evaluation of adhesion amount of chlorine ions After masking tapes manufactured in Examples and Comparative Examples were bonded to one side of a Si wafer having a thickness of 200 μm and a diameter of 150 mm, the sample was allowed to stand at 23 ° C. for 20 minutes. Thereafter, the masking tape was cut along the outer periphery of the wafer.
After immersing the surface of the wafer protected by the masking tape in an electroless Ni plating solution (ph5) at 80 ° C. for 60 minutes, the masking tape is irradiated with 2000 mJ / cm ² of ultraviolet light from the base material side to mask it. The tape was peeled off.

The adhesion amount of chlorine ions on the wafer surface after peeling of the masking tape was measured using an X-ray photoelectron analyzer (manufactured by Perkin Elmer, PHI15400MC). The case where the adhesion amount of chlorine ions was less than 1 × 10 ¹¹ atm / cm ² (below the measurement limit of the apparatus) was evaluated as “◯”, and the case where it was 1 × 10 ¹¹ atm / cm ² or more was evaluated as “×”. did.

(2) Evaluation of plating solution soaking After masking tapes manufactured in Examples and Comparative Examples were bonded to one side of a Si wafer having a thickness of 200 μm and a diameter of 150 mm, the plate was allowed to stand at 23 ° C. for 20 minutes. Thereafter, the masking tape was cut along the outer periphery of the wafer.
The surface of the wafer protected by the masking tape was immersed in an electroless Ni plating solution (ph5) at 80 ° C. for 10 hours. After immersion, the gap between the wafer edge and the tape was visually observed, and the case where no penetration of the plating solution was observed was evaluated as “◯”, and the case where it was observed was evaluated as “X”.

ADVANTAGE OF THE INVENTION According to this invention, it is excellent in the adhesive force in normal temperature, exhibits high adhesive force also in high temperature water of 80-100 degreeC, and can provide the masking tape which can be peeled easily after use.
ADVANTAGE OF THE INVENTION According to this invention, the surface treatment method of the wafer which can protect the surface of a wafer simply and reliably at the time of metal plating can be provided.

Claims (5)

It is a masking tape that consists of a base material and an adhesive layer formed on one surface of the base material, exhibits high adhesive strength even in high-temperature water at 80 to 100 ° C., and can be easily peeled off after use. And
The pressure-sensitive adhesive layer includes at least a segment derived from an alkyl acrylate ester having an alkyl group having 5 or less carbon atoms, a segment derived from an acrylic monomer having a homopolymer glass transition temperature of 80 to 120 ° C., and Containing a copolymer having a radically polymerizable unsaturated bond in the side chain and having a glass transition temperature of −5 to 15 ° C .;
The content of a segment derived from an alkyl acrylate ester having 5 or less carbon atoms of the alkyl group in the copolymer is 40% by weight or more, and the content of a segment having a radical polymerizable unsaturated bond in the side chain Is a masking tape, characterized by being 0.1 meq / g or more. The masking tape according to claim 1, wherein the pressure-sensitive adhesive layer is a gas generating agent that generates gas when irradiated with light. The masking tape according to claim 1 or 2, wherein the substrate has an oxygen permeability of 9 cc / m ² / hr / atm or less measured by a method according to JIS K 7126. A step of applying a masking tape to the side of the wafer on which the circuit is formed on the side where the circuit is not formed, a step of plating the wafer on which the masking tape is attached by an electrolytic plating method or an electroless plating method, A wafer surface treatment method comprising a step of peeling a masking tape from a plated wafer,
The masking tape is composed of a base material and an adhesive layer formed on one surface of the base material, and the adhesive layer has an adhesive strength of 1 N / inch or more at a plating temperature and is peeled off. Peeling force of 0.5 N / inch or less,
The wafer surface treatment method according to claim 1, wherein the masking tape is the masking tape according to claim 1. 5. The width of the protruding portion of the masking tape from the wafer is set to 2 mm or less in the step of applying the masking tape to the side of the wafer on which the circuit is formed on one side. The wafer surface treatment method as described.