JP2003151940A - Back grind tape and method of polishing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back-grind tape which is firmly bonded on a face of a semiconductor wafer, which is located on a side opposite from one to be polished to protect the semiconductor wafer in a polishing process of a semiconductor wafer and is easily peeled from the semiconductor wafer, after polishing is finished, and also to provide a method of polishing a semiconductor wafer using the tape. SOLUTION: The backgrind tape is for protecting a face opposite from one to be polished, in a polishing process of a semiconductor wafer. The back grind tape is such that an adhesive layer is formed on one face of a base material, and the adhesive layer contains an azide compound which generates gas, by applying stimulus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in the step of polishing a semiconductor wafer, firmly adheres to the surface of the semiconductor wafer opposite to the surface to be polished to protect the semiconductor wafer, and easily peels off after polishing. The present invention relates to a back grind tape that can be used and a method for polishing a semiconductor wafer using the back grind tape.

[0002]

2. Description of the Related Art A semiconductor integrated circuit (IC chip) is usually obtained by slicing a high-purity semiconductor single crystal or the like into a wafer, forming a predetermined circuit pattern on the wafer surface using a photoresist, and then forming the wafer. It is manufactured by polishing the back surface with a polishing machine to reduce the thickness of the wafer to about 100 to 600 μm, and finally dicing it into chips.

Here, at the time of polishing, an adhesive sheet called a back grind tape is attached to the surface of the wafer to protect the circuit pattern formed on the surface of the wafer, prevent damage to the wafer, and facilitate polishing. I am.

In order to proceed to the next step after polishing,
It is necessary to peel off this back grinding tape. However, in order to be able to withstand the impact during polishing, the back grind tape needs to have a strong adhesive force, and it has been difficult to peel off the back grind tape that has been firmly adhered. As described above, the back grind tape has been required to satisfy the contradictory conditions of high adhesion and easy peeling.

[0005]

In view of the above situation, the present invention protects a semiconductor wafer by firmly adhering it to the surface of the semiconductor wafer opposite to the surface to be polished in the step of polishing the semiconductor wafer. An object of the present invention is to provide a back grinding tape which can be easily peeled off after polishing and a method for polishing a semiconductor wafer using the back grinding tape.

[0006]

The present invention is a back-grinding tape for protecting a surface opposite to a surface to be polished in a step of polishing a semiconductor wafer, wherein a pressure-sensitive adhesive layer is formed on one surface of a base material. The pressure-sensitive adhesive layer is a back-grinding tape containing an azide compound that generates a gas by applying a stimulus. The present invention is described in detail below.

The back-grinding tape of the present invention comprises an adhesive layer formed on one side of a base material. The base material is not particularly limited, and examples thereof include those made of a resin such as polyethylene terephthalate (PET). When the base material is made of a substance that transmits ultraviolet rays, it is preferable that the semiconductor wafer and the base material can be separated by irradiating the base material with ultraviolet rays.

The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, but it is preferable that the pressure-sensitive adhesive contains a polymerizable oligomer, and the pressure-sensitive adhesive is reduced by polymerization-crosslinking. Examples of such an adhesive include an acrylic acid alkyl ester-based and / or methacrylic acid alkyl ester-based polymerizable polymer having a radiation-polymerizable unsaturated bond in the molecule, and a radiation-polymerizable polyfunctional oligomer or Examples thereof include a photocurable pressure-sensitive adhesive containing a monomer as a main component.

As the above-mentioned polymerizable polymer, for example, a (meth) acrylic polymer having a functional group in the molecule (hereinafter, also referred to as a functional group-containing (meth) acrylic polymer) is synthesized in advance, and A compound having a functional group that reacts with a functional group and a radiation-polymerizable unsaturated bond (hereinafter,
It can be obtained by reacting with a functional group-containing unsaturated compound). In the present specification, the (meth) acrylic polymer means an acrylic polymer and a methacrylic polymer.

The above-mentioned functional group-containing (meth) acrylic polymer is a polymer having tackiness at room temperature, and like the general (meth) acrylic polymer, the alkyl group usually has a carbon number in the range of 2-18. Of the acrylic acid alkyl ester and / or the methacrylic acid alkyl ester as a main monomer, and a functional group-containing monomer and, if necessary, another modifying monomer which can be copolymerized therewith by a conventional method. It is obtained by

Examples of the functional group-containing monomer 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 glycidyl methacrylate. Epoxy group-containing monomers; isocyanate group-containing monomers such as isocyanate ethyl acrylate and isocyanate ethyl methacrylate; amino group-containing monomers such as aminoethyl acrylate and aminoethyl methacrylate.

Examples of the other copolymerizable modifying monomer include various monomers used for general (meth) acrylic polymers such as vinyl acetate, acrylonitrile and styrene.

The weight average molecular weight of the functional group-containing (meth) acrylic polymer is usually about 200 to 2,000,000.

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

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 reticulation of the pressure-sensitive adhesive layer can be efficiently performed by irradiation with light. 2,000 or less and the number of radiation-polymerizable unsaturated bonds in the molecule is 2 to 6. Examples of such more preferable polyfunctional oligomers or monomers include trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate. Alternatively, methacrylates similar to the above may be used. Other examples include 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, commercially available oligoester acrylate, and the same methacrylates as described above. These polyfunctional oligomers or monomers may be used alone,
One or more species may be used in combination.

The photocurable pressure-sensitive adhesive contains the above-mentioned polymerizable polymer and polyfunctional oligomer or monomer as essential components, and when an actinic ray such as ultraviolet ray is used for the polymerization and curing, a photopolymerization initiator is usually added. Is preferred.

The photopolymerization initiator is, for example, 25
Examples thereof include those activated by irradiation with light having a wavelength of 0 to 800 nm. Examples of such photopolymerization initiators include acetophenone derivative compounds such as methoxyacetophenone; benzoinpropyl ether, benzoin isobutyl ether, and the like. Benzoin ether compounds; ketal derivative compounds such as benzyl dimethyl ketal and acetophenone diethyl ketal; phosphine oxide derivative compounds; bis (η5-cyclopentadienyl) titanocene derivative compounds, benzophenone, Michler's ketone, chlorothioxanthone, todecylthioxanthone, dimethylthioxanthone , Diethylthioxanthone, α-hydroxycyclohexyl phenyl ketone, 2
Examples thereof include a radical photopolymerization initiator such as hydroxymethylphenylpropane. These photopolymerization initiators may be used alone or in combination of two or more.

In addition to the above-mentioned components, the above-mentioned photocurable pressure-sensitive adhesive is optionally blended with general pressure-sensitive adhesives such as isocyanate compounds, melamine compounds, and epoxy compounds for the purpose of adjusting the cohesive force of the pressure-sensitive adhesive. You may mix | blend various various polyfunctional compounds. Further, known additives such as a plasticizer, a resin, a surfactant, a wax and a fine particle filler can be added.

In the above-mentioned photo-curable pressure-sensitive adhesive, the entire photo-foamable pressure-sensitive adhesive layer is uniformly and rapidly polymerized and crosslinked by irradiation of light to be integrated, so that the elastic modulus is significantly increased by polymerization and curing. The power is greatly reduced.

The pressure-sensitive adhesive layer contains an azide compound which generates a gas by applying a stimulus. Examples of the azide compound include 3-azidomethyl-3-methyloxetane, terephthalazide, p-tert-butylbenzazide; glycidylazide polymer obtained by ring-opening polymerization of 3-azidomethyl-3-methyloxetane, and the like. Examples thereof include polymers having an azide group. The azide compound decomposes by being stimulated by light, heat, ultrasonic waves, and impact, and is split into nitrogen and active radical species to generate nitrogen gas.

The nitrogen gas generated from the azide compound is released to the outside of the adhesive layer. Thereby, when the back grinding tape of the present invention is stimulated by light, heat, ultrasonic waves, or impact, nitrogen gas generated from the azide compound peels off a part of the adhesive surface to reduce the adhesive strength, and thus the semiconductor wafer is easily The back grind tape can be peeled off from. At this time, it is preferable that all the nitrogen gas generated from the azide compound is released to the outside of the adhesive layer and does not exist in the adhesive substance. However, even in this case, part of the generated nitrogen gas may be present as bubbles in the pressure-sensitive adhesive layer as long as the pressure-sensitive adhesive foams and the cohesive force of the pressure-sensitive adhesive is not significantly reduced.

The active radical species generated by the decomposition of the azide compound act on the polymerizable oligomer to promote the polymerization and crosslinking. Therefore, for example, in the case where the adhesive substance is composed of the photo-curable pressure-sensitive adhesive, polymerization crosslinking occurs due to active radical species generated by decomposition of the azide compound without giving a stimulus by light, resulting in an adhesive force. Is reduced.

The azide compound may be dispersed in the pressure-sensitive adhesive layer, but is preferably present on the surface in contact with the semiconductor wafer. More preferably, the concentration of the azide compound in the surface in contact with the semiconductor wafer is higher than the concentration of the azide compound in the surface in contact with the base material, and more preferably the azide compound is present in the surface in contact with the semiconductor wafer, and the base material It does not exist on the contact surface. As a result, peeling occurs only on the bonding surface between the pressure-sensitive adhesive layer and the semiconductor wafer, and no adhesive residue is generated on the semiconductor wafer.

In order to produce a back-grinding tape having such a structure, the pressure-sensitive adhesive layer has a multi-layer structure composed of at least two layers, and the azide compound constitutes the pressure-sensitive adhesive layer. Of the plurality of layers, it is preferably contained in the layer in contact with the semiconductor wafer and not contained in the layer in contact with the base material.

The method for producing the back grind tape of the present invention is not particularly limited, and for example, a layer made of an adhesive substance not containing the azide compound is formed on a substrate, and the azide compound is contained on the layer. It can be produced by forming a layer made of an adhesive substance.

The method of polishing a semiconductor wafer using the back grinding tape of the present invention is, for example, as follows. First, the back grinding tape of the present invention is attached to a semiconductor wafer. The surface to be attached is the surface opposite to the surface to be polished and on which the circuit pattern is formed in advance. By attaching the back grinding tape, it is possible to prevent the circuit pattern from being damaged or the semiconductor wafer itself from being damaged during polishing.

Then, the semiconductor wafer to which the back grinding tape is attached is fixed to a grinder and the semiconductor wafer is polished. Polishing is usually 100-600 for semiconductor wafers.
The process is performed to a thickness of about μm, but in recent years, polishing may be performed to a thickness of 50 μm or less.

Upon completion of polishing, the pressure-sensitive adhesive layer of the back grind tape is stimulated to reduce the adhesive strength. Examples of the stimulus include light, heat, ultrasonic waves, and impact. When a transparent base material is used, the stimulus can be applied by irradiating light from the base material side. By giving a stimulus, the azide compound contained in the pressure-sensitive adhesive layer is decomposed to generate nitrogen gas, and the nitrogen gas generated from the azide compound peels off a part of the adhesive surface, thereby decreasing the adhesive strength. .

Finally, the back grinding tape is peeled off from the semiconductor wafer. By applying the above-mentioned stimulus, the adhesive force of the pressure-sensitive adhesive layer is reduced, so that the back grinding tape can be easily peeled from the semiconductor wafer. Such a method for polishing a semiconductor wafer is also one aspect of the present invention.

[0030]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation of Adhesive Substance> The following compounds were dissolved in ethyl acetate and irradiated with ultraviolet rays for polymerization to obtain an acrylic copolymer having a weight average molecular weight of 700,000. Resin solid content of the obtained ethyl acetate solution containing the acrylic copolymer 1
To 100 parts by weight, 3.5 parts by weight of 2-isocyanatoethyl methacrylate are added and reacted, and further 20 parts by weight of pentaerythritol triacrylate is added to 100 parts by weight of the resin solid content of the ethyl acetate solution after the reaction. , 0.5 parts by weight of benzophenone and 0.3 parts by weight of polyisocyanate were mixed to prepare an ethyl acetate solution of the pressure-sensitive adhesive (1). Butyl acrylate 79 parts by weight Ethyl acrylate 15 parts by weight Acrylic acid 1 part by weight 2-Hydroxyethyl acrylate 5 parts by weight Photoinitiator 0.2 parts by weight (Irgacure 651, 50% ethyl acetate solution) Lauryl mercaptan 0.01 parts by weight

100 parts by weight of 3-azidomethyl-3-methyloxetane was mixed with 100 parts by weight of the resin solid content of the ethyl acetate solution of the adhesive (1) to prepare an adhesive (2) containing an azide compound. An ethyl acetate solution was prepared.

<Preparation of Back Grinding Tape> A transparent polyethylene terephthalate (P) having a thickness of 38 μm obtained by corona-treating one side of an ethyl acetate solution of the adhesive (1) was used.
The ET) film was coated on the corona-treated surface with a doctor knife so that the thickness of the dried film was about 10 μm, and the solvent was volatilized to dry the coating solution. The dried pressure-sensitive adhesive layer exhibited tackiness in a dry state.

On the other hand, the ethyl acetate solution of the adhesive (2) was
A 38 μm-thick PET film having a surface subjected to a release treatment was applied so that the thickness after drying using a bar coater would be 5 μm, and the solvent was volatilized to dry the pressure-sensitive adhesive layer.

A pressure-sensitive adhesive (1) layer formed on a PET film having one surface subjected to corona treatment and a pressure-sensitive adhesive (2) layer formed on a PET film subjected to release treatment were bonded together. Then, it was cured at 40 ° C. for 3 days to obtain a back grind tape.

<Polishing of Semiconductor Wafer> The PET film for protecting the adhesive (2) layer of the back grind tape was peeled off and attached to a silicon wafer having a diameter of 20 cm and a thickness of about 750 μm. Next, the silicon wafer attached to the back grind tape was attached to a polishing apparatus and polished until the thickness of the silicon wafer was about 200 μm.
From the PET film side, using an ultra-high pressure mercury lamp, 365n
Irradiation intensity of 40 m of ultraviolet light on the PET film surface is 40 m
The illuminance was adjusted to W / cm ² and irradiation was performed for 2 minutes.
After irradiation, the back grinding tape was peeled off from the silicon wafer. The back-grinding tape was not peeled off during the polishing process and could be easily peeled off after irradiation with ultraviolet rays.

[0037]

According to the present invention, in the step of polishing a semiconductor wafer, the surface of the semiconductor wafer opposite to the surface to be polished is firmly adhered to protect the semiconductor wafer and easily peeled off after polishing. It is possible to provide a back grinding tape which can be used and a method for polishing a semiconductor wafer using the back grinding tape.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09J 11/06 C09J 11/06 H01L 21/68 H01L 21/68 N (72) Inventor Yasuhiko Oyama Mishima, Osaka Prefecture 2-1 Hyakusan, Korishima Honcho, Sekisui Chemical Co., Ltd. (72) Inventor Shigeru Dangami 2-1 Hyakusan, Shimahoncho, Mishima-gun, Osaka 2-1 Satoshi Chemical Co., Ltd. Satoshi Hayashi Mishima-Korijima, Osaka Honcho Hyakusan 2-1 Sekisui Chemical Co., Ltd. (72) Inventor Kazuhiro Shimomura Shimamoto Mishima-gun, Osaka Prefecture Hyakusan 2-1 Sekisui Chemical Co., Ltd. (72) Inventor Go Hasegawa Mishima-gun Shimamoto-cho, Osaka Prefecture Yama 2-1 Sekisui Chemical Co., Ltd. F term (reference) 3C058 AA01 AB04 CA01 CB03 4J004 AA10 AB07 AC03 CA06 FA04 4J040 DF041 DF051 HC18 JB08 KA37 PA39 5F031 CA02 DA15 MA22

Claims (6)

[Claims] 1. A back grinding tape for protecting a surface opposite to a surface to be polished in a step of polishing a semiconductor wafer, which comprises an adhesive layer formed on one side of a base material. The backing tape, wherein the pressure-sensitive adhesive layer contains an azide compound that generates a gas by giving a stimulus. 2. The back grinding tape according to claim 1, wherein the azide compound is present on the surface of the adhesive layer which is in contact with the semiconductor wafer. 3. The method according to claim 1, wherein the concentration of the azide compound on the surface of the adhesive layer contacting the semiconductor wafer is higher than the concentration of the azide compound on the surface of the adhesive layer contacting the base material. Back grind tape. 4. The back according to claim 1, wherein the azide compound is present on the surface of the pressure-sensitive adhesive layer that contacts the semiconductor wafer and not on the surface of the pressure-sensitive adhesive layer that contacts the base material. Grind tape. 5. The pressure-sensitive adhesive layer has a multi-layered structure including at least two layers, and the azide compound is contained in a layer in contact with a semiconductor wafer among a plurality of layers constituting the pressure-sensitive adhesive layer. The back grind tape according to claim 1, wherein the back grind tape is not contained in a layer in contact with the base material. 6. A back grind tape in which a pressure-sensitive adhesive layer made of an adhesive substance is formed on at least one surface of a base material, and the pressure-sensitive adhesive layer contains an azide compound which generates a gas when stimulated. To a semiconductor wafer, a step of polishing the semiconductor wafer by fixing the semiconductor wafer on which the back grind tape is stuck to a grinder, and a back grind that is stuck to the semiconductor wafer after polishing. A method for polishing a semiconductor wafer, comprising: a step of stimulating an adhesive layer of the tape to reduce the adhesive force; and a step of peeling the back grinding tape from the semiconductor wafer.