JPH05195255A - Method for surface protection during etching - Google Patents

Abstract

PURPOSE:To protect the surface of a body to be treated by sticking a radiation- curable adhesive tape on an area not to be etched, irradiating the adhesive layer of the tape with radiation for curing thereof and then subjecting the body to etching treatment. CONSTITUTION:In an etching process of a plate material, the area not to be etched is coverd with a radiation-curable adhesive tape to protect the surface. Etching resistance is given to the plate material by preliminarily curing the radiation-curable adhesive layer of the tape by irradiation, then etching is performed, and the adhesive tape is peeled from the plate material. Thereby, the plate material shows improved acid resistance against an etching soln. and decreased water absorption and has etching resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to protect a patterned surface of a wafer on which a pattern is formed in the process of manufacturing various semiconductors according to each application, or to protect the pattern surface when chemical etching is performed on the back surface of the wafer or when etching various metal materials. The present invention relates to a protective tape for a non-etched portion used.

[0002]

2. Description of the Related Art Silicon, gallium-arsenic and the like are generally well known as wafers used in the manufacture of semiconductors, and among them, silicon is often used. This silicon wafer was made from a high-purity silicon-ingot obtained by the single crystal pulling method and had a thickness of 500 to 1000 μm.
It is sliced and manufactured with a thickness of about m. By processing the thus manufactured silicon wafer by various methods, a large number of integrated circuit patterns are formed on the wafer. Then, the back surface of the wafer on which the circuit pattern is formed is subjected to a grinding process by a device called a backside grinder or a chemical etching process (hereinafter referred to as etching) depending on the intended use. Reduce wafer thickness.

The back surface grinding process of this semiconductor wafer is as follows.
The surface of the wafer circuit pattern is fixed by vacuum suction and the back surface of the wafer is ground.
It is processed to a thickness as thin as 200 μm and a uniform thickness.
After that, for the purpose of removing processing strain caused by heat or the like at the time of grinding processing, or for the purpose of further reducing the thickness of the wafer, an etching process of, for example, dipping in an etching solution is performed.

Therefore, in these wafer back surface processing steps, it was necessary to apply a resist ink or the like having excellent etching resistance for the purpose of protecting the pattern surface. However, in order to remove the resist ink after etching, it is necessary to wash with an organic solvent. for that reason,
There are problems such as work environment pollution and solvent regulations, and countermeasures are required. Therefore, a new surface protection method that does not use resist ink has been desired.

On the other hand, attempts have been made to use a tape for surface protection having a low adhesive strength for the purpose of protecting the wafer surface during etching, but the etching resistance is poor and the protective tape adheres to the adherend during the etching process. The problem that the pattern on the wafer is corroded by peeling from the wafer is often generated. In order to prevent the tape from peeling, it has been attempted to increase the adhesive strength of the tape, but not only the etching resistance is still insufficient, but the adhesive strength when peeling the tape from the adherend wafer after the etching process is still insufficient. There was also a problem that the wafer was damaged due to its strength.

In order to solve these problems, a support which is transparent to radiation, for example, light such as ultraviolet rays, or ionizing radiation such as electron beams, has etching resistance, and a support coated on the support. A radiation-curable pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer having a property of being cured by irradiation with radiation has been developed. This is because the adhesive strength before radiation curing is made strong to reduce the penetration of the etching solution when the tape is attached to the adherend and then etched, and the tape itself has etching resistance. Therefore, the tape is made to have a low adhesive force by irradiation with radiation after etching to facilitate peeling from the adherend.

[0007]

However, since the adhesive itself of this radiation-curable adhesive tape is inferior in etching resistance, the portion where the adhesive itself is exposed in the etching solution is attacked by the etching solution and adhesive residue remains. Is the cause of. The adhesive residue itself does not reach up to the pattern surface only in the peripheral portion of the wafer, but since this adhesive contains etching liquid, corrosive gas is generated due to heat at the time of radiation irradiation.
There was a problem that it volatilizes and tends to adversely affect the aluminum terminal part.

Further, the radiation-curable pressure-sensitive adhesive tape itself may be heated by heat generated during etching, and the adhesive force after radiation-curing may increase. When the adhesive force at the time of peeling increases in this way, there arises a problem that the peeling of the tape is defective, the adhesive remains on the pattern surface, or the wafer is likely to be damaged due to the stress at the time of peeling the tape.

According to the present invention, a glue surface caused by corrosion deterioration of the glue exposed on the peripheral portion of the wafer due to absorption of an etching solution is prevented, and a pattern surface caused by a fluctuation in adhesive strength of the radiation curable pressure sensitive adhesive due to heat generated during the etching treatment. It is an object of the present invention to provide a surface protection method for preventing the above-mentioned adhesive residue or peeling failure of the tape.

[0010]

The inventors of the present invention have conducted various studies to overcome the drawbacks of the surface protection method during etching by the conventional radiation-curable pressure-sensitive adhesive tape, and as a result, the adherend wafer By attaching a tape and curing the radiation-curable pressure-sensitive adhesive layer by irradiation with radiation to form a three-dimensional reticulated structure and then etching it, the acid resistance to the etching solution is improved and the water absorption is reduced. It has been found that this can be achieved and that etching resistance can be imparted, and the present invention has been completed based on this finding.

That is, in the present invention, when a plate-shaped material is subjected to chemical etching, a radiation-curable pressure-sensitive adhesive tape is attached to the non-etched portion of the plate-shaped material, and then the radiation-curable pressure-sensitive adhesive layer is irradiated with radiation. The present invention provides a method for protecting a surface during an etching treatment, which comprises subjecting the plate-shaped material to an etching treatment after imparting etching resistance thereto.

The radiation-curable pressure-sensitive adhesive tape used in the surface protection method of the present invention comprises a radiation-transmissive film-like support made of a material having etching resistance and coated with the radiation-curable pressure-sensitive adhesive. .. The chemical etching solution for chemical etching includes a chemical etching solution containing at least one of hydrogen fluoride, hydrogen chloride, sulfuric acid, nitric acid, acetic acid, hydrogen peroxide and phosphoric acid.

Examples of the film-like support include α-types such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, isotactic polypropylene and poly-4-methylpentene-1.
It is a homopolymer of olefin, and as the fluorine-containing resin, it is a fluoropolymer such as polytetrafluoroethylene (PTFE), tetrafluoroethylene hexafluoropropylene copolymer, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, and polyester resin. Is preferably polyethylene terephthalate.

Of these resins, high density polyethylene, isotactic polypropylene and polyethylene terephthalate are more preferably used. It also has the function of absorbing and absorbing the external impact force applied to the adherend during the grinding process of the semiconductor wafer required on the film-like support, preventing the damage of the wafer itself such as microcracks, and providing the tape with cushioning properties. , A film obtained by laminating another resin on a layer of a resin having etching resistance in order to satisfy the function of closely adhering to a wafer pattern surface having complicated unevenness and imparting flexibility without floating or peeling. It can also be a support. However, in this case, it is necessary to set the combination of resins so as not to impair the etching resistance of the film-shaped support.

Examples of the resin laminated on the resin having such etching resistance include ethylene-vinyl acetate copolymer, polybutene-1,1,2-polybutadiene,
Polyurethane, ethylene-ethyl acrylate copolymer,
Ethylene-methyl acrylate copolymer, ethylene-acrylic acid copolymer, homopolymers or copolymers of α-olefins such as ionomers or mixtures thereof, and the like, depending on the required properties of the film-like support. You can choose arbitrarily.

As a method for producing these film-like supports, conventionally known extrusion methods can be used, but in the case of film-like supports obtained by laminating various resins,
A coextrusion method, a laminating method, or the like is used, in which case an adhesive layer may be provided between the resins, as is commonly done in the production of ordinary laminated films. The thickness of such a film-like support is usually appropriate to be 30 to 300 μm from the viewpoint of strength / elongation property and radiation transparency.

The radiation-curable pressure-sensitive adhesive provided on the film-like support is not particularly limited as long as it exhibits desired radiation-curability, but for example, 100 parts by weight of the acrylic pressure-sensitive adhesive may be added to a carbon-carbon double adhesive. 5 to 200 parts by weight of at least one compound selected from the group of a cyanurate compound having a bond and an isocyanurate compound, and a photoinitiator and a polymerization accelerator, other known tackifiers, softening agents, antioxidants Examples thereof include compositions containing agents, pigments and the like.

A polyester or polyol urethane acrylate compound having two or more carbon-carbon double bonds may be added to the above compound in order to impart flexibility to the pressure-sensitive adhesive after irradiation with radiation.

The acrylic pressure-sensitive adhesive used in the present invention is a homopolymer having acrylic acid or methacrylic acid ester as a main constituent unit, acrylic acid or methacrylic acid or its ester, or its acid amide, and the like. It is a copolymer with a copolymerizable comonomer or a mixture of these polymers. As its monomers and comonomers, for example, alkyl esters of acrylic acid or methacrylic acid, such as methyl ester, ethyl ester, butyl ester, 2-ethylhexyl ester, octyl ester, glycidyl ester, hydroxymethyl ester, 2-hydroxyethyl ester, hydroxypropyl ester. And acrylic acid or methacrylic acid amides and N-substituted amides such as N-hydroxymethyl acrylic acid amides or methacrylic acid amides. If necessary, a crosslinking agent such as a polyisocyanate compound or an alkyl etherified melamine compound may be added thereto.

The cyanurate or isocyanurate compound is a compound having a triazine ring or an isotriazine ring in the molecule and further having at least two radiation-polymerizable carbon-carbon double bonds, a monomer,
It may be an oligomer or a mixture thereof. A compound having a triazine ring or an isotriazine ring can be generally synthesized from a halocyan compound, a dianiline compound, a diisocyanate compound or the like as a raw material by a conventional cyclization reaction. Furthermore, a compound used in the present invention can be obtained by introducing a functional group containing a radiation-polymerizable carbon-carbon double bond-containing group such as a vinyl group, an acryloxy group or a methacryloxy group into the compound thus synthesized. ..

In the present invention, the cyanurate or isocyanurate compound is not particularly limited except the above points, but the carbon-carbon double bond-containing group introduced into the triazine ring or the isotriazine ring has a so-called rigid molecular structure,
For example, those containing no aromatic ring heterocyclic group are desirable. The reason is that if the radiation-polymerizable compound is given excessive rigidity by these, the pressure-sensitive adhesive of the present invention becomes excessively brittle by radiation curing. Therefore, it is preferable that the bonding group between the carbon-carbon double bond and the triazine ring or the isotriazine ring contains a group rich in free rotation of atoms. Examples of these groups are alkylene groups, aliphatic groups such as alkylidene groups, and these groups include -O-, -OCO-,
It may have a -COO-, -NHCO-, -NHCOO- bond or the like. When this bonding group is bonded to the triazine ring via -O-, at least one of the three alkylene groups, alkylidene groups and the like bonded to -O- preferably has 2 or more carbon atoms.

Specific examples of these cyanurate or isocyanurate compounds include 2-propenyldi-3-
Butenyl cyanurate, 2-hydroxyethyl bis (2
-Acryloxyethyl) isocyanurate, tris (acryloxyethyl) isocyanurate, tris (methacryloxyethyl) isocyanurate, bis (2-acryloxyethyl) 2- (5-acryloxy) hexyloxyethyl isocyanurate, tris (1 , 3-Diacryloxyisopropyl-oxycarbonyl-n-hexyl)
Isocyanurate, tris (1-acryloxy-3-methacryloxyisopropyl-oxycarbonylamino-
and n-hexyl) isocyanurate.

The number of radiation-polymerizable carbon-carbon double bonds per repeating unit of the monomer or oligomer of the cyanurate compound or isocyanurate compound used in the present invention is usually at least 2, and more preferably 2 to. 6 is good. If the number of double bonds is less than 2, a sufficient degree of cross-linking cannot be obtained by irradiation to reduce the adhesive strength, and if it exceeds 6, the embrittlement of the adhesive after radiation curing becomes excessive. Sometimes.

The amount of the cyanurate compound or isocyanurate compound in the radiation-curable pressure-sensitive adhesive of the present invention is usually 5 to 20 relative to 100 parts by weight of the acrylic pressure-sensitive adhesive.
0 parts by weight. If this blending amount is too small, the radiation-curable pressure-sensitive adhesive may be insufficiently cured (three-dimensional reticulation) by irradiation with radiation, and the deterioration of the radiation-curable pressure-sensitive adhesive due to the penetration of the etching solution is likely to occur. There is.
On the other hand, if the blending amount is too large, the adhesive force after radiation curing becomes too low and the tape is apt to float or peel off during etching.

The urethane acrylate compound which can be added to the above-mentioned compound in order to impart flexibility in the physical properties of the pressure-sensitive adhesive after irradiation with radiation has two or more radiation-polymerizable carbon-carbon double bonds and is radiation-curable. It is a compound having rubber-like elasticity in the subsequent physical properties, and is a urethane acrylate compound such as polyester or polyol having a urethane bond in the molecule, which is a linear aliphatic compound as its structure, and may be a monomer or an oligomer. It doesn't matter.

Examples of such compounds include methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl acrylate and dimethylaminoethyl meta. Acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, polyethylene glycol acrylate and the like and polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-
It can be synthesized using xylylene diisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, etc. as a raw material.

When the radiation-curable pressure-sensitive adhesive tape of the present invention is cured by irradiation with ultraviolet rays, a photopolymerization initiator,
For example, isopropyl benzoin ether, isobutyl benzoin ether, benzophenone, Michler's ketone, chlorothioxanthone, dodecyl thioxanthone,
Dimethylthioxanthone, diethylthioxanthone, benzyl dimethyl ketal, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethyl phenyl propane and the like can be used in combination. By adding one or more of these to the pressure-sensitive adhesive layer, the curing reaction can proceed efficiently and the adherence for fixing the adherend can be reduced even if the curing reaction time or the ultraviolet irradiation amount is small. ..

The thickness of the radiation-curable pressure-sensitive adhesive layer provided on this film support is usually 10 to 50 μm in order to improve the adhesion to the pattern surface. Here, the term “radiation” refers to light rays such as ultraviolet rays or ionizing radiation such as electron beams.

In the present invention, first, the radiation-curable pressure-sensitive adhesive tape is attached to the protective surface of the material to be etched. Then, the adhesive tape attached to the protective surface is irradiated with radiation for a predetermined time to cure the adhesive layer and reduce the adhesive strength. The curing means that the adhesive layer is cured enough to impart etching resistance (acid resistance, water resistance). This curing treatment can be arbitrarily adjusted by appropriately setting the radiation irradiation time. By this curing treatment, the pressure-sensitive adhesive layer forms a three-dimensional reticulated structure, and the adhesive strength of itself decreases. Curing in the present invention to impart etching resistance means to reduce the adhesive force and maintain the adhesive force sufficient to prevent the tape from peeling from the adherend during the etching treatment. The degree of this curing can be set using the adhesive force as an index. For example, the adhesive strength after radiation curing measured according to JIS Z0237 is preferably 20 g / 25 m as a stainless steel plate obtained by polishing the adherend of the radiation curable pressure sensitive adhesive tape with water resistant polishing paper No. 280.
m or more, more preferably 20 to 200 g / 25 mm, most preferably 20 to 100 g / 25 mm. If the adhesive strength is too low, the adhesive tape peels off from the adhered surface during etching, and sufficient etching resistance cannot be obtained regardless of the type of etching solution or the processing time. Further, when it is 200 g / 25 mm or less, the resistance to the etching solution can be more ensured. Furthermore 10
When it is 0 g / 25 mm or less, the tape can be more easily peeled off without being damaged from the adherend after the etching is completed, and the adhesive residue on the peripheral portion of the adherend can be eliminated.

In the method of the present invention, after the etching treatment is completed to facilitate the peeling of the adhesive tape after the etching treatment, before the peeling step, the adhesive tape is additionally irradiated with radiation to be radiation-cured. The adhesive layer may be completely cured.

[0031]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

Example 1 100 parts by weight of an acrylic adhesive (copolymer of 2-ethylhexyl acrylate and n-butyl acrylate) was added to a polyisocyanate compound (Nippon Polyurethane Co., Ltd.).
(Product name: Coronate L) 3 parts by weight, 150 parts by weight of an isocyanurate compound having 5 functional groups and 1 part by weight of α-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator are added and mixed to prepare a radiation curable adhesive. did. The radiation-curable pressure-sensitive adhesive is subjected to corona treatment on a film-like support made of a high-density polyethylene resin having a thickness of 100 μm, and the surface is coated so that the thickness after drying is 20 μm, and thus radiation-curable. An adhesive tape was created.

This radiation-curable pressure-sensitive adhesive tape was cut into a width of 25 mm, and a stainless steel plate polished with water-resistant polishing paper No. 280 was adhered as an adherend, and the adhesive force before and after ultraviolet irradiation was measured according to JIS Z0237 (90 °). Peeling, peeling speed 50 mm / min, and ultraviolet irradiation conditions were a high-pressure mercury lamp of 80 w / cm as an ultraviolet lamp, irradiation time was 10 seconds, and cumulative light amount was 1000 mJ / cm ^{2. The} following Examples and Comparative Examples It depends on the method.). Further, this radiation-curable pressure-sensitive adhesive tape is attached as an adherend to a silicon wafer having a circuit pattern formed thereon and having a diameter of 5 inches, and after leaving it for about 1 hour, it is irradiated with ultraviolet rays to obtain a radiation-curable pressure-sensitive adhesive layer. Was completely cured. The conditions of this ultraviolet irradiation were the same as above. This wafer is treated with nitric acid (conc. 61
%) And hydrogen fluoride water (conc. 46%) mixed solution for etching for 5 minutes in an etching solution (mixing ratio is nitric acid: hydrogen fluoride water = 10: 1 by volume ratio). The state of the tape during the etching treatment was observed, and the peeling, floating, and alteration of the adhesive tape were evaluated.

Next, the adhesive tape was peeled off from the wafer and the peripheral portion of the wafer and the adhesive residue on the pattern were observed with a microscope. The results are shown in Tables 1 and 2.

Example 2 As a radiation curable adhesive, 100 parts by weight of an acrylic adhesive (a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate) was added to a polyisocyanate compound (trade name, manufactured by Nippon Polyurethane Co., Ltd.). Coronate L) 3
8 parts by weight of isocyanurate compound having 6 functional groups
Example except that a radiation-curable pressure-sensitive adhesive prepared by adding and mixing 0 part by weight and 20 parts by weight of a urethane acrylate compound having a functional group of 2 and 1 part by weight of α-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator were used. A radiation-curable pressure-sensitive adhesive tape was prepared in exactly the same manner as in 1.

Next, the adhesive strength of this radiation-curable pressure-sensitive adhesive tape was measured in the same manner as in Example 1, and the surface of the silicon wafer on which the circuit pattern was formed was protected by using this adhesive tape. Etching after irradiation,
The tape was peeled off. The observation and evaluation results during that period are shown in Table 1,
Shown in 2.

Example 3 As a radiation curable pressure sensitive adhesive, 100 parts by weight of an acrylic pressure sensitive adhesive (a copolymer of 2-ethylhexyl acrylate and n-butyl acrylate) was added to a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., trade name). Coronate L) 3
1 part by weight of isocyanurate compound having 6 functional groups
A radiation-curable pressure-sensitive adhesive tape was prepared in exactly the same manner as in Example 1 except that 50 parts by weight and a radiation-curable pressure-sensitive adhesive prepared by adding and mixing 1 part by weight of α-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator were used. Created.

Then, the pressure-sensitive adhesive tape thus obtained was measured in the same manner as in Example 1, and the surface of a predetermined portion of the silicon wafer on which a circuit pattern was formed was protected by using this adhesive tape, and ultraviolet rays were used. Irradiation was performed to semi-cure the adhesive layer. As for the conditions of this ultraviolet irradiation, a high pressure mercury lamp 80 w / cm was used as an ultraviolet lamp, the irradiation time was 2 seconds, and the integrated light amount was 200 mJ / cm ² . After that, etching treatment was performed. After the etching treatment, ultraviolet rays were further irradiated to cure the adhesive layer to further reduce the adhesive strength, and then the adhesive tape was peeled off from the silicon wafer. The observation and evaluation results during that time are shown in Tables 1 and 2.

Comparative Example 1 As a radiation curable adhesive, 100 parts by weight of an acrylic adhesive (copolymer of 2-ethylhexyl acrylate and n-butyl acrylate) was added to a polyisocyanate compound (trade name, manufactured by Nippon Polyurethane Co., Ltd.). Coronate L) 3
Parts by weight, dipentaerythritol hexaacrylate 1
A radiation-curable pressure-sensitive adhesive tape was prepared in exactly the same manner as in Example 1 except that a radiation-curable pressure-sensitive adhesive prepared by adding and mixing 100 parts by weight of α-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator was used. did.

Then, in the same manner as in Example 1, the adhesive strength of this radiation-curable pressure-sensitive adhesive tape was measured. Then, using this adhesive tape, the surface of the silicon wafer on which the circuit pattern was formed was protected and irradiated with ultraviolet rays in the same manner as in Example 1, followed by etching and tape peeling. The observation and evaluation results during that time are shown in Tables 1 and 2.

Comparative Example 2 The radiation-curable pressure-sensitive adhesive tape prepared in Example 1 was adhered as an adherend to a silicon wafer having a circuit pattern formed thereon and having a diameter of 5 inches, and allowed to stand for about 1 hour before being irradiated with ultraviolet rays. An etching process was performed before. After the etching process,
Irradiation with ultraviolet rays was performed and the radiation-curable adhesive tape was peeled off from the adherend wafer. In this case as well, the adhesive strength test of the adhesive tape used was carried out in the same manner as in Example 1, and the state of surface protection was observed. The results are shown in Tables 1 and 2.

[0042]

[Table 1]

[0043]

[Table 2]

As is clear from the results of Table 2, according to the present invention, it is possible to prevent the adhesive residue from remaining in the pattern portion and the peripheral portion of the wafer, and the adhesive tape does not peel off during etching.

[0045]

In the surface protection method of the present invention, the radiation-curable pressure-sensitive adhesive tape is attached to the adherend wafer and the adhesive treatment is performed after the radiation-curing, so that the adhesive residue on the peripheral portion of the wafer can be prevented and at the time of etching. It is possible to prevent the adhesive force of the radiation-curable pressure-sensitive adhesive tape from fluctuating due to the heat generation, and to prevent defective peeling of the tape or adhesive residue on the pattern surface.

Front page continuation (72) Inventor Isamu Noguchi 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. When a plate-shaped material is subjected to a chemical etching treatment, a radiation-curable pressure-sensitive adhesive tape is attached to a non-etched portion of the plate-shaped material, and the radiation-curable pressure-sensitive adhesive layer is irradiated with radiation to be cured, thereby etching resistance. A method for protecting a surface during an etching process, which comprises subjecting the plate-shaped material to an etching process after imparting a property. 2. The surface protection according to claim 1, wherein the radiation-curable pressure-sensitive adhesive tape is irradiated with radiation, cured so that the adhesive force is reduced within a range not lower than 20 g / 25 mm, and then etched. Method.