JPH05198562A - Method of forming polyimide pattern - Google Patents

Abstract

PURPOSE:To provide a polyimide pattern without unwanted film left at a development step by treating a copper wiring layer with an aqueous solution of hydrogen peroxide, forming photosensitive polyimide precursor film on the copper wiring layer, exposing the wiring layer to a pattern of light and developing it, and heat-treating the developed pattern. CONSTITUTION:A silicon wafer with a copper wiring pattern is immersed in an aqueous solution of hydrogen peroxide to cover the wiring pattern with copper oxide. A solution of a photosensitive polyimide precursor is spread on the copper wiring pattern, dried, exposed, and developed. The developed pattern is rinsed with alcohol; thus a polyimide precursor pattern is obtained. After the precursor pattern is thermally cured to obtain a polyimide pattern, the copper oxide on the through holes is etched away. In this manner, no unwanted film remains on through holes at the pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a polyimide pattern having no development residual film on a copper wiring by using a photosensitive polyimide.

[0002]

2. Description of the Related Art The formation of a polyimide pattern using a photosensitive polyimide precursor in which a polyimide precursor is provided with photosensitivity is known as described in, for example, Japanese Patent Publication No. 59-52822. Such a photosensitive material is useful as an interlayer insulating layer of multilayer wiring in an electronic device mounting substrate. In this application, it is necessary to form a through hole (connection hole) in the insulating layer for the conduction of the lower wiring and the external lead.

The through-hole is usually formed through the following four steps.

(1) A film of a photosensitive polyimide precursor is formed on a substrate on which lower wiring has been formed, (2) exposure is performed by masking a through-hole portion, and (3) through-hole with a developing solution. (4) Heat treatment is carried out to dissolve and remove the photosensitive polyimide precursor in the unprinted portion (unexposed portion) for imidization.

[0005]

However, when a polyamic acid type photosensitive polyimide precursor is used to form a through hole on a copper wiring by this method, copper and the photosensitive polyimide precursor structure are Due to the reaction with the carboxyl group, there is a problem that a residual film for development is generated in the through-hole portion where the photosensitive polyimide precursor should be originally removed by the developing solution, resulting in poor conduction between the upper and lower wirings. It was This development residual film is
Even if treated with an etchant or plasma of polyimide, it cannot be easily removed, so to prevent reaction between copper and photosensitive polyimide in advance on copper wiring, a thin film of metal chromium or the like is provided by sputtering or the like, A method of removing this by etching is generally adopted.
However, such a conventional method has a problem that the process is complicated and the cost is high. The present invention was created in view of the above-mentioned drawbacks of the prior art, and an object thereof is to provide a method for forming a polyimide pattern capable of reliably preventing the development residual film on a copper wiring. To provide.

[0006]

The object of the present invention is as follows.
In the method of forming a polyimide pattern on a copper wiring using a polyamic acid type photosensitive polyimide precursor,
A. Applying a hydrogen peroxide solution treatment on the copper wiring, B. Forming a film of a photosensitive polyimide precursor on the copper wiring, C.I. Irradiate pattern-like light, and then develop, D.I. It is achieved by a method for forming a polyimide pattern, which comprises the steps of heating the obtained pattern of the polyimide precursor to convert it into a polyimide pattern.

The term "copper wiring" as used in the present invention means a pattern or a layer formed on the entire surface of metallic copper or an alloy of copper provided on a substrate. The copper layer is usually formed on the substrate by electroplating, sputtering, vacuum deposition or the like, and the pattern layer can be formed by a known method such as a photolithography method.

The hydrogen peroxide solution treatment in the present invention means a treatment for forming a copper oxide film on the copper wiring by exposing the substrate on which the copper wiring is formed to the hydrogen peroxide solution. The aqueous hydrogen peroxide solution in the present invention means an aqueous solution containing hydrogen peroxide and also includes an aqueous solution containing other components. The hydrogen peroxide concentration is not particularly limited, but is preferably 10 to 30%. It is also possible to heat the aqueous hydrogen peroxide solution in order to accelerate the formation of the copper oxide film. The heating temperature is not particularly limited, but is preferably 30 to 50 ° C. The treatment time is not particularly limited, but it is preferably 1 to 72 hours, more preferably 6 to 30 hours. The treated substrate is preferably washed with water and dried.

As the polyimide precursor in the present invention, pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3',
4,4'-biphenyltetracarboxylic dianhydride, 1,
Tetracarboxylic acid dianhydrides such as 2,5,6-naphthalenetetracarboxylic acid dianhydride and cyclobutanetetracarboxylic acid dianhydride, and 4,4′-diaminodiphenyl ether
Ter, 3,3'-diaminodiphenyl sulfone, 4,4
Polyamic acids obtained by reacting diamines such as ′ -diaminodiphenylmethane, bis (3-aminopropyl) tetramethyldisiloxane, metaphenylenediamine, and paraphenylenediamine in an aprotic polar solvent are mentioned. Not limited.

Preferred examples of the aprotic polar solvent include, but are not limited to, N-methyl-2-pyrrolidone, N, N-dimethylacetamide and N, N-dimethylformamide.

The polyamic acid-type photosensitive polyimide precursor used in the present invention refers to a polyamic acid into which a photosensitive compound has been introduced. Examples of the photosensitive compound used for sensitizing the polyimide precursor include an acrylic ester compound, an acrylamide compound, a bisazide, and an amino compound having a vinyl group. Specific examples of the composition of the photosensitive polyimide precursor include those described in JP-B-59-52822.

As a method for forming a film of the photosensitive polyimide precursor on the copper wiring treated with the hydrogen peroxide solution, a known coating film forming method can be adopted. For example, the spinner method is a good example. At this time, for the purpose of improving the adhesiveness, it is also effective to apply a solution containing an organosilicon compound such as aminosilane on the treated copper wiring in advance before forming the film of the photosensitive polyimide precursor. is there.

As a method of irradiating pattern-like light,
An example is a known method in which a mask is placed on the photosensitive polyimide precursor film and light is irradiated. From the viewpoint of photosensitivity of photosensitive polyimide, ultraviolet light is usually used as a light source.

The development is preferably performed with an optimum developing solution according to the composition of the photosensitive polyimide precursor. Usually, N-methyl-2-pyrrolidone, N, N-dimethylacetamide,
A solvent for a polyimide precursor such as N, N-dimethylformamide, or a mixed solvent of these solvents and a non-solvent for a polyimide precursor such as methanol or ethanol can be used as a developing solution.

The conversion of the polyimide precursor into polyimide can be carried out by heat treatment at 200 to 450 ° C. The heat treatment may be performed at a single temperature, or may be performed stepwise or continuously while raising the temperature. The conversion temperature, that is, the heat treatment time at 200 to 450 ° C. is 5
About 60 minutes is enough. Since the contact resistance of the copper oxide coating on the through-hole portion increases when heat-treated, it is desirable to remove the surface by etching with an acid such as an aqueous solution of ammonium persulfate or an aqueous solution of acetic acid, or by a method such as plasma treatment. The concentration of ammonium persulfate when etching the surface of the aqueous solution of ammonium persulfate is not particularly limited, but is preferably 1 to 40%, more preferably 3 to 20%.
Is. The etching time is not particularly limited, but is preferably 5 seconds to 3 minutes.

[0016]

EXAMPLES Example 1 A silicon wafer was sputtered to 3.0 by sputtering.
After forming a copper layer having a thickness of μm, a desired wiring pattern was obtained by photoetching. Next, the silicon wafer on which the wiring pattern was formed was dipped in a 25% hydrogen peroxide aqueous solution at 35 ° C. and treated for 24 hours to form a copper oxide film on the copper wiring pattern.

On the other hand, 20.0 g of 4,4'-diaminodiphenyl ether was dissolved in 200 cc of N-methyl-2-pyrrolidone and stirred at room temperature (about 18 ° C.) to obtain 3,3.
32.2 g of ′, 4,4′-benzophenonetetracarboxylic dianhydride was charged as a powder, and the mixture was stirred at room temperature for 1 hour and further at 55 ° C. for 2 hours. To this solution, 31.4 g of dimethylaminoethyl methacrylate and Michler
A solution of 0.94 g of s-ketone dissolved in 85 g of N-methyl-2-pyrrolidone was added and mixed to obtain a photosensitive polyimide precursor solution. The resulting photosensitive polyimide precursor solution was applied onto a copper wiring pattern treated with an aqueous hydrogen peroxide solution with a spinner. After drying at 80 ° C. for 1 hour, exposure with an exposure dose of 300 mj / cm ² was performed, and development was performed with a mixture of N-methyl-2-pyrrolidone, xylene and water in a ratio of 7: 3: 1. Rinsing was performed to form a polyimide precursor pattern. At this time, no development residual film was formed on the through-hole portion. After that, cure at 120 ° C for 1 hour, then 400
The temperature was raised to 5 ° C / min and the temperature was kept at 400 ° C for 1 hour to obtain a polyimide pattern. Then, the copper oxide film on the through-hole portion was etched with a 10% aqueous solution of ammonium persulfate. The film thickness of the polyimide pattern thus obtained was 10 μm. Further, when the electric conductivity of the through-hole portion was examined, it was found that the conduction was good.

Comparative Example 1 After a wiring pattern was obtained on a silicon wafer in the same manner as in Example 1, the same photosensitive polyimide precursor as in Example 1 was used.
It was applied with a spinner. Then, drying, exposure, development and rinsing were performed under the same conditions as in Example 1 to form a polyimide precursor pattern. At this time, formation of an undeveloped film was observed in the through-hole portion. Then cure at 120 ℃ for 1 hour,
Further, the temperature is raised to 400 ° C. at 5 ° C./min and the temperature is 400 for 1 hour.
The temperature was kept at ℃ to obtain a polyimide pattern. The thickness of the polyimide pattern thus obtained was 10 μm, and the thickness of the residual film after development in the through-hole portion was about 0.5 μm. In addition, when the electric conductivity of the through-hole portion was examined, it was found that conduction was poor.

Example 2 A 0.2 μm copper layer was formed on a silicon wafer by vacuum evaporation, and a 2.8 μm copper layer was further formed by electrolytic plating, and then a desired wiring pattern was formed by photoetching. -I got it. Next, the silicon wafer on which the wiring pattern was formed was treated in the same manner as in Example 1 so that the hydrogen peroxide solution was treated. Drying, exposure, development and rinsing were performed under the same conditions as in Example 1 to form a polyimide precursor pattern. At this time, no development residual film was formed on the through-hole portion. After that, cure at 120 ° C for 1 hour, then 40 more
The temperature was raised to 0 ° C. at 5 ° C./min and kept at 400 ° C. for 1 hour to obtain a polyimide pattern. Then, the copper oxide film on the through-hole portion was etched with a 10% aqueous solution of ammonium persulfate. The polyimide pattern thus obtained
The film thickness of the film was 10 μm. Further, when the electric conductivity of the through-hole portion was examined, it was found that the conduction was good.

Comparative Example 2 After a wiring pattern was obtained on a silicon wafer in exactly the same manner as in Example 2, the same photosensitive polyimide precursor as in Example 1 was applied by a spinner. Then, drying, exposure, development and rinsing were performed under the same conditions as in Example 1 to form a polyimide precursor pattern. At this time, formation of an undeveloped film was observed in the through-hole portion. After that, it is cured at 120 ° C for 1 hour, and further heated to 400 ° C at 5 ° C / min for 1 hour 4
It was kept at 00 ° C. The polyimide thus obtained
The film thickness of the pattern was 10 μm, and the film thickness of the residual film after development in the through-hole portion was about 0.5 μm. See through
When the electrical conductivity of the solder part was examined, it was found that conduction was poor.

Example 3 A wiring pattern was obtained on a silicon wafer in exactly the same manner as in Example 2, and then treated with an aqueous hydrogen peroxide solution in exactly the same manner as in Example 1.

On the other hand, 20.0 g of 4,4'-diaminodiphenyl ether was dissolved in 200 cc of N-methyl-2-pyrrolidone and stirred at room temperature (about 18 ° C.) for 3,3.
′, 4,4′-Biphenyltetracarboxylic dianhydride 2
Charge 9.4g with powder and stir at room temperature for 1 hour, then add 5
Stirring was continued at 5 ° C for 3 hours. A solution prepared by dissolving 31.4 g of dimethylaminomethacrylate and 0.94 g of Michler's ketone in 85 g of N-methyl-2-pyrrolidone was added to and mixed with this solution to obtain a photosensitive polyimide precursor. A solution was obtained. The obtained photosensitive polyimide precursor solution was applied by a spinner onto copper wiring treated with an aqueous hydrogen peroxide solution. Then, drying, exposure, development and rinsing were performed under the same conditions as in Example 1 to form a polyimide precursor pattern. At this time, no development residual film was formed on the through-hole portion. Thereafter, it was cured at 120 ° C. for 1 hour, further heated to 400 ° C. at 5 ° C./min and kept at 400 ° C. for 1 hour to obtain a polyimide pattern. Then, the copper oxide film on the through-hole portion was etched with a 10% aqueous solution of ammonium persulfate. The film thickness of the polyimide pattern thus obtained was 10 μm. Further, when the electric conductivity of the through-hole portion was examined, it was found that the conduction was good.

Comparative Example 3 After a wiring pattern was obtained on a silicon wafer in exactly the same manner as in Example 2, the same photosensitive polyimide precursor as in Example 3 was applied by a spinner. Then, drying, exposure, development and rinsing were performed under the same conditions as in Example 1 to form a polyimide precursor pattern. At this time, formation of an undeveloped film was observed in the through-hole portion. After that, it is cured at 120 ° C. for 1 hour, and further heated to 400 ° C. at 5 ° C./min for 1 hour 4
It was kept at 00 ° C. The polyimide thus obtained
The film thickness of the pattern was 10 μm, and the film thickness of the residual film after development in the through-hole portion was about 0.5 μm. See through
When the electrical conductivity of the solder part was examined, it was found that conduction was poor.

Example 4 The silicon wafer on which the copper wiring pattern was formed in Example 3 was dipped in a 25% hydrogen peroxide aqueous solution at 35 ° C. 2
A polyimide pattern was obtained in exactly the same manner as in Example 3 except that the treatment was carried out by immersing in a 20% hydrogen peroxide aqueous solution at 40 ° C. for 24 hours instead of performing the treatment for 4 hours. Then, the copper oxide film on the through-hole portion was etched with a 10% aqueous solution of ammonium persulfate. The film thickness of the polyimide pattern thus obtained was 10 μm. Further, when the electric conductivity of the through-hole portion was examined, it was found that the conduction was good.

[0025]

According to the forming method of the present invention, when the polyimide pattern is formed on the copper wiring, the polyimide pattern without the residual film of development can be surely formed and formed on the copper wiring. It is possible to solve the problem of poor electrical continuity of electrical connection in a through hole.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G03F 7/027 514 7/038 504 H05K 3/28 D 7511-4E

Claims (1)

[Claims] 1. A method of forming a polyimide pattern on a copper wiring by using a polyamic acid type photosensitive polyimide precursor, comprising the steps of: Applying a hydrogen peroxide solution treatment on the copper wiring, B. Forming a film of a photosensitive polyimide precursor on the copper wiring, C.I. Irradiate with pattern light, and then develop, D. The resulting polyimide precursor pattern is heated to convert it into a polyimide pattern, which comprises the steps of:
How to form