JPH05198559A - 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 oxygen plasma, forming photosensitive polyimide precursor film on the copper wiring layer, exposing the film to light and developing it, and heat-treating the developed pattern. CONSTITUTION:A copper layer is formed on a silicon wafer and made into a desired wiring pattern by photoetching. The silicon wafer is treated in an oxygen plasma to coat the wiring pattern with copper oxide. A solution of a photosensitive polyimide precursor is spread on the copper wring pattern, exposed, and developed to form a polyimide precursor pattern. The precursor pattern is heat-treated to obtain a polyimide pattern. In this manner, no unwanted film of the polyimide pattern remains in the development step. Therefore, through holes at the copper wiring do not cause the problem of electrical discontinuity or poor connections.

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 oxygen plasma treatment on the copper wiring, B. Forming a film of a photosensitive polyimide precursor on the copper wiring, C.I. Pattern
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 oxygen plasma treatment in the present invention is a treatment for forming a copper oxide film on the copper wiring by exposing the substrate on which the copper wiring is formed to oxygen plasma.
The oxygen plasma in the present invention means plasma containing plasma of oxygen molecules and atoms, and also includes plasma in a mixed state with plasma of other molecules and atoms.

In the plasma of the present invention, positively charged particles and negatively charged electrons have almost the same density,
It refers to a group of particles that are distributed with almost electrical neutrality.
At this time, it does not matter even if atoms or molecules that are not ionized, that is, neutral particles are mixed therein.

A commercially available plasma reactor can be used as the oxygen plasma processing apparatus. The oxygen plasma treatment time is preferably 1 to 60 minutes, more preferably 5 to 30 minutes. As high frequency output, 100 to 5
00W is preferable. The oxygen flow rate is 10 to 200 m
1 / min is preferable.

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 the 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 of forming a film of the photosensitive polyimide precursor on the copper wiring which has been subjected to the oxygen plasma treatment, 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 a pattern of 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 carried out 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 the polyimide precursor such as N, N-dimethylformamide, or a mixed solvent of these solvents and a non-solvent for the polyimide precursor such as methanol or ethanol can be used as the 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 with an aqueous solution of ammonium persulfate is not particularly limited, but is preferably 1 to 40%, more preferably 3 to 20.
%. The etching time is not particularly limited, but 5
Seconds to 3 minutes are preferred.

[0018]

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.

[0019]

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

Example 1 3.0 μ was sputtered on a silicon wafer.
After forming a copper layer of m, by photoetching,
A desired wiring pattern was obtained. Next, the silicon wafer on which the wiring pattern is formed is connected to the plasma reactor (PR
-501A Yamato Scientific Co., Ltd., high frequency output 3
Oxygen plasma treatment was carried out for 20 minutes under the conditions of 00 W and an oxygen flow rate of 30 ml / min 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.) for 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 an oxygen plasma-treated copper wiring pattern by a spinner. After drying at 80 ° C. for 1 hour, exposure with an exposure amount of 300 mj / cm ² was performed, and N
7: methyl-2-pyrrolidone, xylene and water:
After development with a 3: 1 mixture, rinsing with isopropyl alcohol was performed to form a polyimide precursor pattern.
At this time, no development residual film was formed on the through-hole portion. Then cure at 120 ° C for 1 hour, then 400 ° C
Up to 5 ° C./min and kept at 400 ° C. for 30 minutes 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. to min and the temperature is raised to 400 ° C. for 3 minutes.
After keeping for 0 minutes, a polyimide pattern was obtained. The film thickness of the polyimide pattern thus obtained was 10 μm, and the film 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 deposition, 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 subjected to oxygen plasma treatment in exactly the same manner as in Example 1. 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. 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 30 minutes 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 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 to 400 ° C.
I kept it for 30 minutes. 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 After a wiring pattern was obtained on a silicon wafer in exactly the same manner as in Example 2, oxygen plasma treatment was performed in 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 resulting photosensitive polyimide precursor solution, on the copper wiring subjected to oxygen plasma treatment,
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, no development residual film was formed on the through-hole portion. Then cure at 120 ℃ for 1 hour,
Furthermore, the temperature is raised to 400 ° C at 5 ° C / min, and the temperature is raised to 400 ° C for 3
After keeping for 0 minutes, a polyimide pattern was obtained. 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 to 400 ° C.
I kept it for 30 minutes. 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.

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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 oxygen plasma 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