JPH05197159A - Forming method for polyimide pattern - Google Patents

Abstract

PURPOSE:To surely form a polyimide pattern having no development residual film and prevent the defective conduction of the electric connection on through holes formed on copper wires when the polyimide pattern is formed on the copper wires. CONSTITUTION:In the forming method of a polyimide pattern on copper wires with a polyamic acid type photosensitive polyimide precursor, a coating liquid containing an organic silicon compound is coated and dried on copper wires (A), a film of the photosensitive polyimide precursor is formed on the organic silicon compound film (B), the precursor film is exposed and developed to form a pattern (C), the pattern of the precursor is heated and converted into a polyimide pattern (D), and the silicon dioxide film at through hole sections of the polyimide pattern is processed by an etching agent or plasma to remove the silicon dioxide film (E).

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, and more particularly to a method for forming a polyimide pattern having no development residual film on a copper wiring by using a photosensitive polyimide. It is about.

[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 or the passivation layer for the conduction between the lower wiring and the external lead.

The through hole is usually (1) forming a film of a photosensitive polyimide precursor on a substrate on which a lower wiring is formed,
(2) masking and exposing the through-hole portion, (3) dissolving and removing the photosensitive polyimide precursor in the through-hole portion (unexposed portion) with a developer, and (4) performing heat treatment. It is formed by undergoing each step of imidization by.

[0004]

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 a carboxyl group in the photosensitive polyimide precursor structure are formed. Due to the reaction with the above, 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 electrical connection between the upper and lower wirings. Since this development residual film cannot be easily removed even if it is treated with a polyimide etchant or plasma, a method of forming a thin film of metal chromium or the like on the copper wiring by sputtering and removing it by etching is generally adopted. ing. However, such a conventional method has a problem that the process is complicated and the cost is high.

The present invention was devised in view of the above-mentioned drawbacks of the prior art. An object of the present invention is to provide a method for surely forming a polyimide pattern having no development residual film on a copper wiring. Especially.

[0006]

The object of the present invention is as follows.
A method for forming a polyimide pattern on a copper wiring using a polyamic acid type photosensitive polyimide precursor, which comprises: Applying a coating liquid containing an organosilicon compound on the copper wiring and then drying it. B. Forming a film of a photosensitive polyimide precursor on the organosilicon compound film, C.I. Selectively exposing the photosensitive polyimide precursor coating and then developing to form a pattern, D. By heating the pattern of the photosensitive polyimide precursor, it is converted into a polyimide pattern, E. A polyimide pattern comprising the steps of removing the silicon dioxide film by treating the silicon dioxide film in the through holes of the polyimide pattern with an etching agent or plasma.
This is achieved by the method of forming a film.

In the present invention, the copper wiring means a pattern or a layer formed on the entire surface and made of metallic copper or an alloy of copper provided on a substrate such as a silicon wafer. 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.

A coating liquid containing an organosilicon compound is applied onto the copper wiring and then dried. Here, as the copper wiring, a copper oxide layer may be previously formed on the surface of the copper wiring by heat treatment in oxygen, oxygen plasma treatment, ozone treatment, chemical treatment or the like, as described later.

Examples of the organosilicon compound in the present invention include compounds represented by the following formula.

[0010]

[Chemical 1] Here, n is an integer of 1 or more. R ₁ and R ₃ represent a monovalent hydrocarbon group or an alkoxy group. Examples of the monovalent hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, a propyl group, and a butyl group, an alkenyl group such as a vinyl group or an allyl group, a phenyl group, or an aryl group such as a tolyl group, or the like. And a group in which some or all of the hydrogen atoms of the group are substituted with an organic group such as an amino group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group and a butoxy group.
R ₂ and R ₄ represent a hydrogen atom or a monovalent hydrocarbon group. As the monovalent hydrocarbon group, a methyl group, an ethyl group,
Examples thereof include alkyl groups such as propyl group and butyl group.
Specific preferred examples of the organosilicon compound include N-β
Examples of the aminosilane include (aminoethyl) γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane. However, it is not limited to these.

These organic silicon compounds are dissolved in an organic solvent and then added with water to prepare a coating solution. The organic solvents used include alcohols, esters,
Known compounds such as ketones and aromatic hydrocarbons can be used alone or in combination.

As the coating liquid containing the organosilicon compound,
A commercially available coating solution can be used. For example AP-4
20 (manufactured by Toray Industries, Inc.), VM-651 (Du Pont
Manufactured) can be used.

As a coating method, a known method such as a spinner method, a spray method or a dipping method may be used. As the drying conditions, drying at a temperature of less than 100 ° C., preferably 10 to 90 ° C. for 1 minute to 40 minutes is suitable.

Then, a photosensitive polyimide precursor coating is applied on the obtained organosilicon compound coating and then dried to form a photosensitive polyimide precursor coating.

The photosensitive polyimide precursor used in the present invention is one prepared by introducing a photosensitive compound into polyamic acid, and all known ones can be used.

Polyimide precursors that can be used include pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4 '.
-Biphenyltetracarboxylic dianhydride, 1,2,5
Tetracarboxylic dianhydrides such as 6-naphthalene tetracarboxylic dianhydride and cyclobutane tetracarboxylic dianhydride, 4,4′-diaminodiphenyl ether,
3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, bis (3-aminopropyl)
Tetramethyldisiloxane, metaphenylenediamine,
Examples thereof include, but are not limited to, a polyamic acid obtained by reacting a diamine such as paraphenylenediamine in an aprotic polar solvent. Preferred examples of the aprotic polar solvent include N-methyl-2-pyrrolidone,
Examples thereof include, but are not limited to, N, N-dimethylacetamide and N, N-dimethylformamide. As the photosensitive compound capable of sensitizing the polyimide precursor,
Examples thereof include bisazide and amino compounds having a vinyl group. Specific examples of the composition of the photosensitive polyimide precursor include those described in JP-B-59-52822.

The formation of the photosensitive polyimide precursor coating on the organosilicon compound coating may be carried out by a known method. For example, the spinner method is a good example. As drying conditions, drying is usually performed at 50 to 100 ° C. for 15 minutes to several hours.

This photosensitive polyimide precursor coating is then selectively exposed and then developed to remove unexposed portions (including the polyimide precursor coating in the through holes) to form a predetermined pattern. ..

A pattern is formed on the photosensitive polyimide precursor film.
An example of the method of irradiating the film-shaped light is a method of placing a mask on the film of the photosensitive polyimide precursor and irradiating with light. In view of the photosensitivity of the photosensitive polyimide precursor, ultraviolet light is usually used as the 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,
It is used as a solvent for a polyimide precursor such as N, N-dimethylformamide, or a non-solvent for these solvents and methanol, ethanol and other polyimide precursors and a developer.

The photosensitive polyimide precursor pattern is then converted into a polyimide pattern by heat treatment. The heat treatment is usually performed in the range of 200 to 400 ° C. The heat treatment time may be about 5 to 30 minutes. The heat treatment may be performed at a single temperature, or may be performed stepwise or continuously while raising the temperature.

By the heat treatment, the through hole portion of the polyimide pattern and the organic silicon compound film existing immediately below the polyimide pattern are changed to a silicon dioxide film. Therefore, only the silicon dioxide film in the through holes of the polyimide pattern is treated with an etching agent or plasma to remove the silicon dioxide film.

Examples of the etching agent for the silicon dioxide film in the through-hole portion include sulfuric acid aqueous solution and hydrofluoric acid aqueous solution. It is also possible to use a fluorine-based gas for etching. When the silicon dioxide film on the through hole is etched with an etching agent, the silicon dioxide film immediately below the polyimide pattern is also gradually etched, so only the silicon dioxide film on the through hole is removed by etching. It is desirable to stop the etching to the extent necessary and sufficient for this purpose. The treatment conditions when using a sulfuric acid aqueous solution include, for example, a concentration of 0.5.
It is preferable that the treatment is performed with a 3% by volume sulfuric acid aqueous solution for 1 to 3 minutes.

Next, a method for forming a copper oxide layer on the copper wiring surface in advance will be described.

The heat treatment in oxygen means that the copper wiring is heat-treated in an atmosphere in which oxygen is present to form a copper oxide film on the copper wiring, and the heat treatment is not necessarily performed in a 100% oxygen atmosphere. No need to do. As an example of a preferable atmosphere, heat treatment in air can be mentioned. The heat treatment temperature is preferably 100 to 400 ° C. More preferably, it is 100 to 300 ° C. More preferably, it is 150 to 250 ° C. The heat treatment time is 5 to
120 minutes is preferred. It is more preferably 15 to 60 minutes. More preferably, it is 20 to 40 minutes. As a heating means, a commercially available oven or furnace can be used.

The oxygen plasma treatment is to form a copper oxide film on the copper wiring by exposing the substrate on which the copper wiring is formed to oxygen plasma. Here, the oxygen plasma means plasma including plasma of oxygen molecules and atoms, and also includes plasma in a mixed state with plasma of other molecules and atoms. Here, the plasma refers to a group of particles in which positively charged particles and negatively charged electrons are distributed with substantially the same density and while maintaining substantially electrical neutrality. At this time, it does not matter 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 50
0 W is preferable. The oxygen flow rate is 10 to 200 ml
/ Min is preferable.

Further, the ozone treatment is to form a copper oxide film on the copper wiring by exposing the substrate on which the copper wiring is formed to ozone.

Here, ozone means a gas mainly containing ozone molecules represented by the structural formula O ₃ , and gas of other molecules or atoms may be mixed. As the ozone treatment device, for example, a commercially available ozone cleaning device can be used. The ozone treatment time is not particularly limited, but is 1
The time is preferably 120 to 120 minutes, more preferably 10 to 90 minutes.

The chemical treatment means treatment with a halogen acid solution treatment, a hydrogen peroxide solution treatment, an alkali metal hydroxide solution treatment or the like. Usually, the copper wiring is immersed in these solutions and oxidized. The copper coating is formed on the copper wiring.

Here, the halogen acid-based solution treatment is to immerse the substrate on which the copper wiring is formed in a halogen acid-based solution to form a copper oxide film on the copper wiring. The halogen acid-based solution here means a solution containing a halogen oxygen acid or a salt thereof. Examples include bromic acid, chloric acid,
Examples thereof include solutions containing perchloric acid, chlorous acid, hypochlorous acid, hypobromite, and the like, and solutions containing metal salts thereof. Preferable examples of the halogen acid solution include sodium chlorite aqueous solution, sodium hypochlorite aqueous solution, sodium chlorate aqueous solution, sodium perchlorate aqueous solution, potassium chlorate aqueous solution, potassium perchlorate aqueous solution, and the like. The concentration of the halogen acid solution is not particularly limited, but is preferably 5 to 40%. It is also possible to heat the halogen acid-based solution in order to accelerate the formation of the copper oxide film. The heating temperature is 40 to 10
0 ° C is preferred. The time for the treatment with the halogen acid solution is not particularly limited, but 5 minutes to 3 hours is preferable. After the treatment with the halogen acid solution, the substrate is preferably washed with water and dried.

The hydrogen peroxide solution treatment is to form 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 hydrogen peroxide solution in order to accelerate the formation of the copper oxide film. The heating temperature is not particularly limited, but 3
0-50 degreeC is preferable. 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.

Further, the alkali metal hydroxide aqueous solution treatment is to form a copper oxide film on the copper wiring by exposing the substrate on which the copper wiring is formed to the alkali metal hydroxide aqueous solution.

Examples of the alkali metal hydroxide aqueous solution include an aqueous solution containing an alkali metal hydroxide, and other components may be contained in addition to the alkali metal hydroxide. For example, potassium persulfate, ammonium persulfate or the like may be added as a reaction accelerator. The term "alkali metal hydroxide" as used herein means an alkali metal in the periodic table, that is, a hydroxide of an element other than hydrogen belonging to Group IA. For example, potassium hydroxide,
Examples thereof include sodium hydroxide and lithium hydroxide. Preferred are potassium hydroxide and sodium hydroxide.

The alkali metal hydroxide concentration is not particularly limited, but is preferably 1 to 30%. Further, it is also preferable to heat the alkali metal hydroxide aqueous solution in order to accelerate the formation of the copper oxide film. The heating temperature is not particularly limited, but is preferably 50 to 100 ° C. The treatment time is not particularly limited, but is preferably 1 to 20 minutes,
It is more preferably 5 to 15 minutes. The treated substrate is preferably washed with water and dried.

[0035]

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

Example 1 3.0 μ was sputtered on a silicon wafer.
After forming the copper layer of m, the desired copper wiring pattern was obtained by photoetching. Next, an organosilicon compound film forming coating solution "AP-420" (manufactured by Toray Industries, Inc.) was applied on a silicon wafer having a copper wiring pattern formed thereon by a spinner to form an organosilicon compound film. Formed.
Then, it was dried at 20 ° C. for 1 minute.

On the other hand, 4,4'-diaminodiphenyl ether
Teru 20.0 g was dissolved in 200 cc of N-methyl-2-pyrrolidone and stirred at room temperature (about 18 ° C.).
32.2 g of 3 ', 4,4'-benzophenone tetracarboxylic acid dianhydride was charged as powder and stirred at room temperature for 1 hour,
The stirring was continued at 55 ° C. for 2 hours. To this solution, a solution prepared by dissolving 31.4 g of dimethylaminoethyl methacrylate and 0.94 g of Michler's ketone in 85 g of N-methyl-2-pyrrolidone was added and mixed,
A solution of the photosensitive polyimide precursor was obtained.

The solution of the obtained photosensitive polyimide precursor was applied onto a silicon wafer on which an organosilicon compound film was formed by 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, and further to 400 ° C at 5 ° C /
The temperature was raised at min and kept at 400 ° C. for 1 hour. The film thickness of the polyimide pattern thus obtained (including the silicon dioxide film immediately below the pattern) was 10 μm. Then, the obtained polyimide pattern was treated with a 2% by volume sulfuric acid aqueous solution at 25 ° C. for 2 minutes, whereby the silicon dioxide film on the through-hole portion was completely removed. The film thickness of the polyimide pattern (including the silicon dioxide film immediately below the pattern) did not change. When the electrical conductivity of the through-hole portion was examined, the conduction was good.

Comparative Example 1 After a copper wiring pattern was obtained on a silicon wafer in exactly the same manner as in Example 1, the same photosensitive polyimide precursor solution as used in Example 1 was applied by a spinner. Example 1
Under the same conditions as above, drying, exposure, development and rinsing were performed to form a polyimide precursor pattern. At this time, formation of a development residual 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.
It was kept at 400 ° C. for an hour. The film thickness of the polyimide pattern thus obtained was 10 μm. Also through
The development residual film was found to be formed in the hole portion, and the film thickness was about 0.
It was 5 μm. In addition, when the electric conductivity of the through-hole portion was examined, it was found that the conduction was poor.

Example 2 In place of forming a copper layer by sputtering in Example 1, a 0.2 μm copper layer was formed by vacuum evaporation, and a 2.8 μm copper layer was further formed by electrolytic plating. A polyimide pattern was obtained in exactly the same manner as in Example 1. Film thickness of the polyimide pattern thus obtained (including the silicon dioxide film directly below the pattern)
Was 10 μm. Then, the obtained polyimide pattern was treated with a 2% by volume sulfuric acid aqueous solution at 25 ° C. for 2 minutes, whereby the silicon dioxide film on the through-hole portion was completely removed. The film thickness of the polyimide pattern (including the silicon dioxide film immediately below the pattern) did not change. When the electrical conductivity of the through-hole portion was examined, the conduction was good.

COMPARATIVE EXAMPLE 2 Instead of forming a copper layer by sputtering in Comparative Example 1, a 0.2 μm copper layer was formed by vacuum vapor deposition, and a 2.8 μm copper layer was further formed by electrolytic plating. A polyimide pattern was obtained exactly as in Comparative Example 1. The film thickness of the polyimide pattern thus obtained was 10 μm. Further, a residual film of development was found to be formed in the through-hole portion, and the film thickness was about 0.5 μm. In addition, when the electric conductivity of the through-hole portion was examined, it was found that the conduction was poor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G03F 7/40 521 7124-2H 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 coating liquid containing an organosilicon compound on the copper wiring and then drying it. B. Forming a film of a photosensitive polyimide precursor on the organosilicon compound film, C.I. Selectively exposing the photosensitive polyimide precursor coating and then developing to form a pattern, D. By heating the pattern of the photosensitive polyimide precursor, it is converted into a polyimide pattern, E. A polyimide pattern comprising the steps of removing the silicon dioxide film by treating the silicon dioxide film in the through holes of the polyimide pattern with an etching agent or plasma.
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