JPH06242613A - Formation of polyimide pattern - Google Patents

Abstract

PURPOSE:To surely form the polyimide patterns free from films remaining after development in the case of formation of the polyimide patterns on copper wirings and to obtain the polyimide patterns which solve the problem of a conduction defect of electrical connection in through-holes and prevent the oxidation of the copper wirings during a heat treatment and have excellent moisture resistant adhesiveness between the polyimide and the copper wirings. CONSTITUTION:This method for formation of the polyimide patterns is a method for forming the polyimide patterns on the copper wirings by using photosensitive polyimide precursor and includes respective stages for forming a film of a silicon alkoxide compd. having no amino groups and a photosensitive polyimide precursor film in this order on the copper wirings, then patterning the photosensitive polyimide precursor film, converting these patterns to the polyimide patterns by heating and removing the films of both silicon alkoxide compds. in the through-hole parts.

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 on copper wiring using a photosensitive polyimide precursor.

[0002]

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

The through hole is usually formed by (1) forming a film of a photosensitive polyimide precursor on a substrate on which lower wiring has been 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 developing solution, and (4) imidizing by heat treatment. It is formed by going through each process.

[0004]

However, especially 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 of 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. This undeveloped film cannot be easily removed by treating with a polyimide etchant or plasma.

Another problem that generally occurs when forming a polyimide pattern using a polyimide precursor is as follows.
There is oxidation of copper wiring under the polyimide during heat treatment. Even if the curing is done in nitrogen, the traces of oxygen present in the oven often oxidize the copper wiring under the polyimide through the polyimide.

In order to prevent this oxidation, a thin film of metallic chromium or the like is provided on the copper wiring by sputtering, etc., and after patterning the polyimide, a thin film of metallic chromium or the like in the through holes is removed by etching. Is generally adopted. However, such a conventional method has a problem that the process is complicated and the cost is high.

As a simple method for forming a through hole of a polyamic acid type photosensitive polyimide precursor on a copper wiring, a method of patterning the photosensitive polyimide precursor after applying an organosilicon compound on the copper wiring is also considered. (Japanese Patent Application Laid-Open No. 4-63421, Japanese Patent Application No. 4-1)
No. 04332), the former has a problem in moisture-proof adhesion between polyimide and copper wiring, and the latter has a problem that the copper wiring under the polyimide is oxidized during curing.

The present invention was devised in view of the above-mentioned drawbacks of the prior art. An object of the present invention is to reliably form a polyimide pattern without a development residual film on a copper wiring, and further, to form a copper wiring during heat treatment. Another object of the present invention is to provide a method for forming a polyimide pattern, which is capable of preventing oxidization of copper and excellent in moisture-resistant adhesion between polyimide and copper wiring.

[0009]

The object of the present invention is as follows.
A method of forming a polyimide pattern on a copper wiring by using a photosensitive polyimide precursor, comprising: A. A step of forming a film of a silicon alkoxide compound having an amino group on the copper wiring, B. A step of forming a film of a silicon alkoxide compound having no amino group on the film of a silicon alkoxide compound having an amino group, C. A step of forming a photosensitive polyimide precursor film on the film of the silicon alkoxide compound having no amino group, D. A step of selectively exposing the photosensitive polyimide precursor film and then developing it to form a pattern, E. Converting the pattern of the photosensitive polyimide precursor to a polyimide pattern by heating, F. A through hole portion of the polyimide pattern, a step of removing a coating of a silicon alkoxide compound having an amino group and a coating of a silicon alkoxide compound not having an amino group, To be achieved.

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. Here, the copper wiring may have a copper oxide layer formed on the surface of the copper wiring by a natural oxide film or an oxide film forming treatment such as oxygen plasma treatment. The copper layer is usually formed on the substrate by electroplating, sputtering, vacuum deposition, or the like, and the pattern can be formed by a known method such as a photolithography method.

A film of a silicon alkoxide compound having an amino group is formed on the copper wiring. Examples of the method include a method in which a coating solution containing a silicon alkoxide compound having an amino group is applied and then dried.

Examples of the silicon alkoxide compound having an amino group in the present invention include compounds represented by the following formula.

[0013]

[Chemical 1] Here, x is an integer of 0 to 3. R ¹ and R ¹ ′ represent hydrogen or a monovalent hydrocarbon 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 and an allyl group, an aryl group such as a phenyl group and a tolyl group, or a group of these groups. Examples thereof include a group in which some or all of hydrogen atoms are substituted with an organic group such as an amino group. However, at least one group of R ¹ or R ¹ ′ must have an amino group. R ¹ and R ¹ ′ may be the same or different. Further, it may contain a partial condensate of the above compound.

A preferred specific example of the silicon alkoxide compound having an amino group is N-β (aminoethyl).
γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ
Examples thereof include, but are not limited to, aminosilane compounds such as aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane.

These silicon alkoxide compounds having an amino group are dissolved in an organic solvent, and water is added as necessary to prepare a coating solution. The organic solvent includes alcohols, esters, ketones and aromas. Known compounds such as group hydrocarbons can be used alone or in combination of two or more.

As the coating liquid containing a silicon alkoxide compound having an amino group, a commercially available coating liquid can be used. For example, AP-420 (manufactured by Toray), VM-65
1 (manufactured by Du Pont) or the like 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 condition, drying at 100 ° C. or lower, preferably 10 to 90 ° C. for 1 minute to 40 minutes is suitable.

The film thickness of the silicon alkoxide compound having an amino group is not particularly limited, but is 0.0
01 to 0.1 μm is preferable, and 0.00 is more preferable.
It is 5 to 0.05 μm.

Then, a film of a silicon alkoxide compound having no amino group is formed on the obtained film of a silicon alkoxide compound having an amino group. Examples of the method include a method in which a coating solution containing a silicon alkoxide compound having no amino group is applied and then dried.

Examples of the silicon alkoxide compound having no amino group in the present invention include compounds represented by the following formula.

[0021]

[Chemical 2] Here, x is an integer of 0 to 3. R ² and R ² ′ represent hydrogen or a monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group and butyl group, alkenyl groups such as vinyl group and allyl group, aryl groups such as phenyl group and tolyl group. However, these groups must not have an amino group. R ² and R ² ′ may be the same or different. Further, it may contain a partial condensate of the above compound.

Specific preferred examples of the silicon alkoxide compound having no amino group include tetraethoxysilane, monoethyltriethoxysilane, monomethyltriethoxysilane, diethyldiethoxysilane, dimethyldiethoxysilane, tetramethoxysilane and monobutyltrisilane. Examples include, but are not limited to, ethoxysilane.

These silicon alkoxide compounds having no amino group are dissolved in an organic solvent and, if necessary, water is added to prepare a coating solution. The organic solvent to be used includes alcohols, esters, Known compounds such as ketones and aromatic hydrocarbons can be used alone or in combination of two or more.

As the coating liquid containing a silicon alkoxide compound having no amino group, a commercially available coating liquid can be used. For example, "Atron" NSi-500 (manufactured by Nisso Kasei), OCD-TYPE2 (manufactured by Tokyo Ohka) or the like 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, 70 to 200 ° C., preferably 80 to 150 ° C. and 1 minute to 20 minutes are suitable. A coating of a silicon alkoxide compound having no amino group, if necessary,
It can be converted into a silicon dioxide film by heating. 300-500 degreeC is suitable as a heating temperature.

The film thickness of the film of the silicon alkoxide compound having no amino group is not particularly limited, but can be 0.
05-1 μm is preferable, and more preferably 0.08-
It is 0.5 μm.

Then, a photosensitive polyimide precursor film is formed on the obtained film of the silicon alkoxide compound having no amino group. Examples of the method include a method in which a photosensitive polyimide precursor is applied and then dried.

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. Introducing a photosensitive compound here means adding a photosensitive compound, forming a structure in which the photosensitive compound is reacted with a polyamic acid by a bond such as an ester bond, and the like.

The 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, and 4,4′-diaminodiphenyl ether,
3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, bis (3-aminopropyl)
Tetramethyldisiloxane, metaphenylenediamine,
Examples thereof include, but are not limited to, polyamic acid obtained by reacting a diamine such as paraphenylenediamine in an aprotic polar solvent.

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

Examples of the photosensitive compound capable of sensitizing the polyimide precursor include bisazide, an amino compound having a vinyl group, a hydrocarbon compound having an acrylic acid group, and a hydrocarbon compound having a methacrylic acid group. Examples of the sensitizing method include a method of imparting a photosensitive compound to a polyamic acid through an ester bond and a method of imparting a photosensitive compound to a polyamic acid through an ionic bond. Specific photosensitive polyimide precursor compositions include, for example, JP-B-59-52822 and JP-B-55-302.
No. 07, JP-A No. 53-127723 can be mentioned.

The coating of the photosensitive polyimide precursor coating on the coating of the silicon alkoxide compound having no amino group may be carried out by a known method. For example, a spinner method is a good example. The drying condition is usually 50 to 250 [deg.] C. for 1 minute to several hours. When drying at a high temperature of 100 ° C. or higher, it is preferable to carry out in a nitrogen atmosphere.

Then, the photosensitive polyimide precursor coating is selectively exposed and then developed to remove the unexposed portion (including the polyimide precursor coating in the through hole portion) to form a predetermined pattern. .

As a method of irradiating the photosensitive polyimide precursor film with a pattern of light, a method of placing a mask on the film of the photosensitive polyimide precursor and irradiating with light can be mentioned as an example. In view of the photosensitivity of the photosensitive polyimide precursor, ultraviolet light is usually used as the light source.

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

Then, the pattern of the photosensitive polyimide precursor is heat-treated to be converted into a polyimide pattern. 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 carried out at a single temperature, or may be carried out stepwise or continuously while raising the temperature. By heat treatment, the through hole part of the polyimide pattern and the film of the silicon alkoxide compound having an amino group and the film of the silicon alkoxide compound having no amino group, which existed under the polyimide pattern, become a film having a structure close to that of silicon dioxide. Change.

Then, the film of the silicon alkoxide compound having an amino group and the film of the silicon alkoxide compound having no amino group are removed from the through holes of the polyimide pattern. Examples of the method include a method of treating with an etching agent or plasma.

Examples of the etching agent include sulfuric acid aqueous solution and hydrofluoric acid aqueous solution. It is also possible to use a fluorine-based gas for etching. When the through-hole coating is etched with an etchant, the coating immediately below the polyimide pattern is gradually etched, so the etching can be stopped to the extent necessary and sufficient to remove only the through-hole coating. Is desirable. As a treatment condition when using an aqueous solution of sulfuric acid, for example, it is preferable to use an aqueous solution of sulfuric acid having a concentration of 0.5 to 3% by volume for 1 to 3 minutes.

[0039]

【Example】

Example 1 3.0 μ was formed on a silicon wafer by sputtering.
After forming a copper layer of m, a desired copper wiring pattern was obtained by photoetching. Next, a coating solution "AP-420" (made by Toray) of a silicon alkoxide compound having an amino group is applied on a silicone wafer having a copper wiring pattern formed thereon by a spinner to form a film of the silicon alkoxide compound having an amino group. Formed. Then 20 ℃
And dried for 1 minute. The film thickness was about 0.01 μm.

Next, a coating solution "Atron" NSi-500 (manufactured by Nisso Kasei) of a silicon alkoxide compound having no amino group was coated on the coating film of a silicon alkoxide compound having an amino group with a spinner to remove the amino group. A silicon alkoxide compound coating film having no ash was formed. Then 1
It was dried at 00 ° C for 2 minutes. The film thickness was 0.2 μm.

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.).
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 obtained solution of the photosensitive polyimide precursor was applied onto a silicon wafer having a film formed thereon by a spinner. After drying at 80 ° C. for 1 hour, exposing at an exposure dose of 300 mJ / cm ² , developing with a mixture of N-methyl-2-pyrrolidone, xylene and water in a ratio of 7: 3: 1, and then using isopropyl alcohol. And rinsed to form a pattern of the polyimide precursor. At this time, no development residual film was formed in the through hole portion.

After that, a nitrogen atmosphere (mixed oxygen concentration of about 10
00ppm) at 120 ℃ for 1 hour, then 4
The temperature was raised to 00 ° C at 5 ° C / min and kept at 400 ° C for 1 hour. The thickness of the polyimide pattern thus obtained (including the 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 coating film in the through holes was completely removed. At this time, the film thickness of the polyimide pattern (including the film immediately below the pattern) did not change. Further, when the electric conductivity of the surface of the through hole portion was examined, the conduction was good.

Further, in order to examine the oxidation of the copper wiring under the polyimide, the polyimide was removed with a knife to expose the copper wiring and the surface was observed with an optical microscope, but no interference color observed during the formation of copper oxide was observed. It had the luster of pure copper, and the electrical conductivity of the surface was examined. Moreover, when the moisture-resistant adhesiveness was examined, 2 atm,
It was good even after 240 hours at 120 ° C. and 100% humidity.

Comparative Example 1 After a copper wiring pattern was obtained on a silicone wafer in exactly the same manner as in Example 1, a solution of the same photosensitive polyimide precursor used in Example 1 was applied by a spinner, 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 an undeveloped film was observed in the through holes.

After that, it was cured at 120 ° C. for 1 hour, further heated to 400 ° C. at 5 ° C./min, and then heated at 400 ° C. for 1 hour.
Kept at. The thickness of the polyimide pattern thus obtained was 10 μm. Next, when the film in the through hole portion was removed in the same manner as in Example 1, a development residual film was observed to be formed in the through hole portion, and the film thickness was about 0.5 μm. Further, when the electric conductivity of the surface of the through hole portion was examined, it was found that there was poor conduction.

Further, in order to examine the oxidation of the copper wiring under the polyimide, the polyimide was removed with a knife to expose the copper wiring, and the surface was observed with an optical microscope. As a result, an interference color due to the formation of copper oxide was observed, and the color was red, and when the electric conductivity of the surface was examined, it was found that conduction was poor. In addition, when the moisture-resistant adhesion was examined, it was good even after 240 hours under 2 atmospheres, 120 ° C., and 100% humidity.

Comparative Example 2 After a copper wiring pattern was obtained on a silicone wafer in exactly the same manner as in Example 1, a coating solution of the same silicon alkoxide compound having an amino group as that used in Example 1 was used. Under the same conditions as above, it was applied onto a copper wiring pattern and dried. Next, a solution of the same photosensitive polyimide precursor as that used in Example 1 was applied by a spinner and dried under the same conditions as in Example 1,
Exposure, development and rinsing were performed to form a polyimide precursor pattern. At this time, no development residual film was formed in 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. The thickness of the polyimide pattern thus obtained was 10 μm. Then, after removing the coating film on the through holes as in Example 1, the conductivity of the surface of the through holes was examined. However, when the copper wiring was exposed and the surface was observed with an optical microscope, an interference color due to the formation of copper oxide was observed and the color was red, and when the electrical conductivity of the surface was examined, there was poor conduction. Moreover, when the moisture-resistant adhesiveness was examined,
It was good even after 240 hours under atmospheric pressure, 120 ° C., and 100% humidity.

Comparative Example 3 After a copper wiring pattern was obtained on a silicone wafer in exactly the same manner as in Example 1, the same silicon alkoxide compound coating liquid having no amino group as that used in Example 1 was used. Under the same conditions as above, it was applied onto a copper wiring pattern and dried. Next, the same photosensitive polyimide precursor solution as that used in Example 1 was applied by a spinner, and dried, exposed, developed and rinsed under the same conditions as in Example 1 to form a polyimide precursor pattern. At this time, no development residual film was formed 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, and heated at 400 ° C. for 1 hour.
Kept at. The thickness of the polyimide pattern thus obtained was 10 μm. Next, as in Example 1,
After removing the coating film on the through holes, the electrical conductivity of the surface of the through holes was examined, and it was confirmed that the electrical continuity was good.

Furthermore, the copper wiring was exposed and the surface was observed with an optical microscope. The interference color observed during the formation of copper oxide was not seen, and the copper had the luster of pure copper. As a result, it was found that conduction was good. However, when the moisture-resistant adhesiveness was examined under 2 atm, 120 ° C., and 100% humidity, after 50 hours, the polyimide pattern was observed to float from the copper wiring.

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. At this time, there was no development residual film in the through hole portion. The thickness of the polyimide pattern thus obtained (including the 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 coating film in the through holes was completely removed. At this time, the film thickness of the polyimide pattern (including the film immediately below the pattern) did not change. Further, when the electric conductivity of the surface of the through hole portion was examined, the conduction was good.

When the polyimide was removed with a knife to expose the copper wiring and the surface was observed with an optical microscope, the interference color observed during the formation of copper oxide was not observed, and the copper had a luster of pure copper. Further, when the electric conductivity of the surface was examined, it was found that the electrical continuity was good. Moreover, when the moisture-resistant adhesion was examined,
It was good even after 240 hours under 2 atm, 120 ° C. and 100% humidity.

COMPARATIVE EXAMPLE 4 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 thickness of the polyimide pattern thus obtained was 10 μm. In addition, a development residual film was found to be formed in the through hole portion, and the film thickness was about 0.5 μm. Further, when the electric conductivity of the surface of the through hole portion was examined, it was found that there was poor conduction.

Further, in order to investigate the oxidation of the copper wiring under the polyimide, the polyimide was removed with a knife to expose the copper wiring, and the surface was observed with an optical microscope. As a result, an interference color due to the formation of copper oxide was observed, and the color was red, and when the electric conductivity of the surface was examined, it was found that conduction was poor. In addition, when the moisture-resistant adhesion was examined, it was good even after 240 hours under 2 atmospheres, 120 ° C., and 100% humidity.

The above results are summarized in Table 1.

[0058]

[Table 1]

[0059]

According to the present invention, when a polyimide pattern is formed on a copper wiring, it is possible to surely form a polyimide pattern without a development residual film, and to solve the problem of electrical continuity failure in a through hole. Moreover, the copper wiring is not oxidized during the heat treatment, and a polyimide pattern having excellent moisture-resistant adhesion between the polyimide and the copper wiring can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H01L 21/312 B 7352-4M H05K 3/28 D 7511-4E

Claims (2)

[Claims] 1. A method of forming a polyimide pattern on a copper wiring using a photosensitive polyimide precursor, which comprises: A step of forming a film of a silicon alkoxide compound having an amino group on the copper wiring, B. A step of forming a film of a silicon alkoxide compound having no amino group on the film of a silicon alkoxide compound having an amino group, C. A step of forming a photosensitive polyimide precursor film on the film of the silicon alkoxide compound having no amino group, D. A step of selectively exposing the photosensitive polyimide precursor film and then developing it to form a pattern, E. Converting the pattern of the photosensitive polyimide precursor to a polyimide pattern by heating, F. A method of forming a polyimide pattern, comprising: a step of removing a coating film of a silicon alkoxide compound having an amino group and a coating film of a silicon alkoxide compound having no amino group in a through hole portion of the polyimide pattern. 2. The method for forming a polyimide pattern according to claim 1, wherein the photosensitive polyimide precursor is a polyamic acid type photosensitive polyimide precursor.