JPH06234870A - Etching liquid for polyimide and its use - Google Patents

Abstract

PURPOSE:To obtain a etching liquid for polyimide containing respective specific amounts of quaternary ammonium hydroxide, amino alcohol and alcohol as essential components, having high etching speed, capable of forming a through hole and a deep pattern and useful for electronic material, etc. CONSTITUTION:The etching liquid contains (A) 5-20wt.% of a quaternary ammonium hydroxide such as tetramethylammonium hydroxide, (B) 10-60wt.% of an amino alcohol such as 2-8C aliphatic or alicyclic amino alcohol (e.g. ethanolamine) and (C) 20-80wt.% of an alcohol such as 1-6C aliphatic alcohol as essential components. The etching liquid is preferably used for the wet etching of a polyimide or a fluorine-containing polyimide having low thermal expansion coefficient.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Polyimide has heat resistance, chemical resistance,
It is used for various purposes in the manufacture of ICs, LSIs, module substrates and the like as electronic materials because of its excellent electrical properties and mechanical properties. In these applications, it is often necessary to form a pattern by using a polyimide resin as a film or a coating film and etching a part of the polyimide.

The present invention relates to a novel etching solution and method of use in a wet processing method for forming a pattern on this polyimide.

[0003]

2. Description of the Related Art Conventional wet processing methods for polyimide include a method of etching (dissolving) a partially imidized polyimide precursor (polyamic acid) in an alkaline aqueous solution using a positive resist as a mask, and a completely imidized polyimide precursor. There is known a method of etching (decomposing the main chain by formation of hydrazide) with hydrazine-ethylenediamine using a negative resist as a mask, and the pattern depth that can be formed depends on the pattern size, but is about 15 μm. It is the limit.

Etching with an aqueous alkaline solution in a partially imidized state in which the imidization reaction is not completed cannot change the etching rate due to variations in the imidization rate, and cannot sufficiently process thick films of 20 μm or more. There is a problem that a low thermal expansion polyimide or a fluorine-containing polyimide having such a main chain structure cannot be etched, and etching after the completion of the imidization reaction has a problem that the etching solution is not preferable in the working environment.

As a method for improving these, as to the processing of a low thermal expansion polyimide having a rigid main chain structure, Japanese Patent Laid-Open No. Sho 6-62
2-253621 describes that a polyimide having a rigid main chain structure with a specific composition can have both low thermal expansion and wet processability with hydrazine-ethylenediamine, and JP-A-4-15233 and JP-A-4-15233. -20
No. 541 has 10 wt% or more urea, 8 to 28 wt%
Amine compounds such as ethylenediamine, 1-35 wt%
Describes a method for processing a polyimide with an aqueous solution of alkali hydroxide or quaternary ammonium hydroxide or a hydroalcoholic solution.

This method can process polyimide without using hydrazine, and is excellent as a novel etching composition liquid for improving the working environment, but it still has a problem in using ethylenediamine. It is insufficient for etching low thermal expansion polyimide or fluorine-containing polyimide having a rigid main chain structure developed in recent years.

[0007]

An object of the present invention is to provide a low thermal expansion polyimide or a fluorine-containing polyimide having a rigid main chain structure,
It is an object of the present invention to provide a novel etching solution that enables practical wet processing with a processing depth of 20 μm or more without using hydrazine or ethylenediamine whose use is a problem in operation, and a method of using the same.

[0008]

Means for Solving the Problems In view of the above-mentioned problems of the present inventors, various investigations have been made on the conditions for alkali decomposition of polyimide, and a rigid low thermal expansion polyimide or a fluorine-containing polyimide has a resistance to an alkaline aqueous solution. Since it is far superior to conventional polyimide, it is necessary to improve the wettability with an organic medium in order to carry out a solid-liquid interface reaction quickly. In use as a resist, in view of the fact that it is essential to use a cyclized rubber type negative resist excellent in solvent resistance, the use conditions of the negative resist and a combination of various alkaline solutions were earnestly studied, The present invention has been completed by recognizing the remarkable effect of improving the wet processability of polyimide to amino alcohol, which is relatively safe.

That is, in order to solve the above problems, the novel polyimide etching solution provided by the present invention is 5 to 20 wt% of quaternary ammonium hydroxide and 10 to 10 wt.
60% by weight of amino alcohol and 20 to 80% by weight of alcohol are essential components, and as the quaternary ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, It is a tetraalkylammonium hydroxide such as tetrabutylammonium hydroxide, and the aminoalcohol has 2 to 8 carbon atoms such as ethanolamine, aminopropanol, aminobutanol, aminohexanol and aminocyclohexanol.
Is an aliphatic or alicyclic amino alcohol, and the alcohol has 1 to 6 carbon atoms such as methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, tert-butanol, and ethylene glycol. Can be used. In addition, an organic solvent, water, a stabilizer, or the like may be added in the range in which the action of etching is not significantly changed.

Regarding the content of quaternary ammonium hydroxide in the etching solution, when the concentration is 5 wt% or less, the etching rate becomes slow, and when it is 20 wt% or more, the etching rate is improved but the pattern shape becomes poor, and the amount of amino alcohol added. When the content is less than 10 wt%, the pattern shape is poor, and when the content is 60 wt% or more, the etching rate becomes slow.
The etching rate shows a maximum value depending on the amount of amino alcohol added, and particularly in the range of 15 wt% or more and less than 40 wt%, the etching rate is large and the pattern shape is good.

In etching the polyimide, the polyimide precursor solution or a polyimide precursor composition solution comprising a polyimide precursor solution and a three-dimensional thermosetting resin is applied to the substrate and desolvated, and then 200 to 30.
A polyimide obtained by baking at 0 ° C., particularly a fluorine-containing polyimide or a polyimide composition, wherein the pattern mask is obtained by applying / baking a cyclized rubber negative photoresist and exposing / developing a desired pattern. This is a mask to be used, and the etching treatment is carried out in a liquid temperature range of 10 to 60 ° C. Desolvation is preferably carried out at a low temperature for a long time, and depending on the film thickness of the polyimide, it can be carried out in the range of 50 to 150 ° C. for 10 to 150 minutes in an inert atmosphere such as air or hydrogen. If the temperature is lower than 50 ° C., it takes too much time and is not practical, and if the temperature is higher than 150 ° C., problems such as flatness, whitening phenomenon, and generation of bubbles occur, which is not preferable.

The resist used in the etching of the present invention is not particularly limited.
Examples include MR series, NNR series of Nagase & Co., Ltd., FSR series of Fuji Yakuhin Kogyo.

If the baking temperature of the polyimide is less than 200 ° C., imidization is incomplete and the etching rate is high, but the solvent resistance is poor, and if the stripping solution temperature of the negative resist is 100 ° C. or more, it is completely dissolved in the stripping solution. At 300 ° C. or higher, etching is possible, but the etching rate becomes slow. The method of using the resist is not particularly problematic under the recommended conditions of commercial products, and the etching treatment may be a dipping method, a spray method or the like. The etching treatment temperature tends to increase at high temperatures, but considering the vapor pressure of the organic medium to increase, the range of 10 ° C. to 60 ° C. is preferable.

The polyimide to be etched with the etching solution of the present invention is not particularly limited, but aromatic polyimide is suitable, fluorine-containing aromatic polyimide is more suitable, and diamine component is 2,2'-substituted-4,4'-. Further suitable are polyimides composed of benzidine and pyromellitic acid or pyromellitic acid derivatives and polyimides whose physical properties are improved by copolymerization of siloxydiamine and / or with maleimide compounds. Specifically, the diamine component includes 4,4′-diaminobenzanilide, 4,4′-binaphthylamine and the following formula.

[0015]

[Chemical 1]

(Wherein R is the same or different CF ₃ , C
Represents H ₃ , C ₂ H ₅ , OCH ₃ , OC ₂ H ₅ , Cl, Br or a phenyl group. ) 2,2'-substitution-4,
4'-benzidine or 4,4'-diaminobenzanilide, 4,4'-binaphthylamine and the like, and specific examples of Chemical formula 1 are 2,2'-bis (trifluoromethyl) -4,4'- Benzidine, 2,2'-dimethyl-
4,4'-benzidine, 2,2'-dichloro-4,4 '
-Benzidine, 2,2'-dibromo-4,4'-benzidine, 2,2'-dimethoxy-4,4'-benzidine,
2,2'-diethoxy-4,4'-benzidine, 2,
2'-diphenyl-4,4'-benzidine etc. can be illustrated.

The siloxydiamine is not particularly limited, but 1,2-bis (3-aminopropyl) -1,1,
2,2-tetramethyldisiloxane, 1,2-bis (3
Examples include -aminobutyl) -1,1,2,2-tetramethyldisiloxane, bis (4-aminophenoxy) dimethylsilane, and 1,3-bis (4-aminophenoxy) tetramethyldisiloxane.

The diamine component used in combination with the above diamine in a proportion of less than 30 mol% is not particularly limited, but o-, m-, p-phenylenediamine, 2,4-diaminotoluene, 2, 5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4′-diaminodiphenylmethane, 4,
4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 1, 3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy)
Benzene, 1,4-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy)
Phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4
-(4-Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] hexafluoropropane ,
2,2-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane,
2,2-bis [4- (3-amino-5-trifluoromethylphenoxy) phenyl] hexafluoropropane,
2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2 , 2-bis (3-amino-4-methylphenyl) hexafluoropropane, 4,4'-bis (4-aminophenoxy) octafluorobiphenyl, 3,5-diaminobenzotrifluoride, 2,5-diaminobenzotrifluor Lido,
2,2'-bistrifluoromethyl-4,4'-diaminobiphenyl, 2,2'-bistrifluoromethyl-
2,4'-diaminobiphenyl, 3,3'-bistrifluoromethyl-4,4'-diaminobiphenyl, 3,
Examples thereof include 3'-bistrifluoromethyl-5,5'-diaminobiphenyl.

As the maleimide compound used, bismaleimides are preferable, and 4,4'-bismaleimide diphenylmethane, 4,4'-bismaleimide diphenyl ether, 4,4'-bismaleimide benzanilide,
2,2′-bis [4- (4-maleimidophenoxy) phenyl] propane and the like, as well as 2,2′-bis (4-maleimidophenyl) hexafluoropropane, 2,2 ′
-Bis [4- (4-maleimidophenoxy) phenyl]
Hexafluoropropane, 2,2'-bis [4- (2-
Trifluoromethyl-4-maleimidophenoxy) phenyl] hexafluoropropane, 4,4′-bis (4-
Examples thereof include fluorine-containing bismaleimide such as maleimidophenoxy) octafluorobiphenyl.

The pyromellitic acid derivative is not particularly limited, and examples thereof include pyromellitic acid, trifluoromethylbenzenetetracarboxylic acid, bistrifluoromethylbenzenetetracarboxylic acid, and anhydrides or esters of difluorobenzenetetracarboxylic acid. Also,
In addition, the tetracarboxylic acid component used in combination at a ratio of less than 30 mol% is not particularly limited,
Hexafluoroisopropylidene diphthalic acid, biphenyl tetracarboxylic acid, benzophenone tetracarboxylic acid, oxydiphthalic acid, cyclobutane tetracarboxylic acid, bicyclo (2,2,2) oct-7-ene-2,3,5,6-tetracarboxylic acid An acid anhydride or ester can be illustrated.

The polyimide precursor solution which is etched with the etching solution of the present invention contains the above diamine component and tetracarboxylic acid component, N, N-dimethylacetamide,
It can be obtained by mixing and reacting in a solvent such as N, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, phenol, cresol, halogenated phenol at 0 to 150 ° C.

[0022]

【Example】

Example 1 6.89 g of 2,2 'was placed in a 4-neck separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen introducing tube.
-Bis (trifluoromethyl) -4,4'-benzidine (21.52 mmol, 97 mol%), 0.16 g of 1,3-bis (3-aminopropyl) tetramethyldisiloxane (0.66 mmol, 3 mol%) And 4.84
g of pyromellitic dianhydride (22.19 mmol) and 1.78 g of 2,2′-bis (4- (4-maleimido-2-trifluoromethylphenoxy) phenyl) hexafluoropropane (solid content of polyamic acid) 15 wt%), 77.5 g of γ-butyrolactone was added, and the mixture was stirred under a nitrogen stream at room temperature for 24 hours to obtain a polyimide precursor composition solution having a viscosity of 490 poise (22 ° C.) and a solid content concentration of 15 wt%. Got

The solution was spin-coated on a silicon substrate to a film thickness of about 25 μm, desolvated at 70 ° C. for 1 hour, and then 250 ° C.
After baking for 2 hours at 50 ° C., a negative resist (FSR manufactured by Fuji Yakuhin Kogyo Co., Ltd., the same applies hereinafter) is applied, and then 50, 30,
Exposure of line and space pattern of 20 μm
Developed, tetramethylammonium hydroxide 12 wt%,
2-aminoethanol 20 wt%, methanol 65 wt
%, 3 wt% water at 40 ° C. for 5 minutes, remove the resist, and wash with methanol.
It was dried at 0 ° C. for 30 minutes.

The initial film thickness was 24.7 μm, and when the processed pattern was observed with a scanning electron microscope, even the line and space pattern of 20 μm was clearly etched up to the substrate surface, and the pattern width on the polyimide surface was side-etched. Was not observed, and the pattern widths on the substrate surface were good at about 40 μm, about 20 μm, and about 10 μm, respectively. The film thickness at this time was measured by a stylus type film thickness meter to be 24.9 μm, and the film thickness after baking at 350 ° C. for 1 hour was 23.6 μm.

Example 2 4.86 g of 2,2 'was placed in a four-necked separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen introducing tube.
-Bis (trifluoromethyl) -4,4'-benzidine (15.19 mmol), 0.20 g of 1,3-bis (3-aminopropyl) tetramethyldisiloxane (0.80 mmol), 0.71 g of hexa Fluoroisopropyrodenphthalic acid dianhydride (1.60mmo
l) 3.14 g of pyromellitic dianhydride (14.4 g)
0 mmol) and 50.7 g of γ-butyrolactone were added, and the mixture was stirred under a nitrogen stream at room temperature for 24 hours to obtain a polyimide precursor composition solution having a viscosity of 170 poise (22 ° C.) and a solid content concentration of 15 wt%.

The solution was spin-coated on a silicon substrate so as to obtain a film thickness of about 25 μm, desolvated at 70 ° C. for 1 hour, baked at 250 ° C. for 2 hours, and then coated with a negative resist to give a thickness of 50 μm. Exposure and development of line and space pattern, tetramethylammonium hydroxide 12
40 ° C. in an etching liquid consisting of wt%, 2-aminoethanol 20 wt%, methanol 63 wt% and water 3 wt%
After dipping for 5 minutes, the resist was peeled off, washed with methanol and dried at 60 ° C. for 30 minutes.

The initial film thickness was 22.9 μm, and when the processed pattern was observed with a scanning electron microscope, it was clearly etched to the substrate surface, and no side etching was observed in the pattern width on the polyimide surface. The width was about 40 μm, which was good.
The film thickness at this time was measured by a stylus type film thickness meter to be 23.3.
μm, the film thickness after baking at 350 ° C. for 1 hour is 21.6
was μm.

Comparative Example 1 The solution obtained in Example 1 was spin-coated on a silicon substrate to a film thickness of about 25 μm and desolvated at 70 ° C. for 1 hour.
After baking at 0 ° C. for 2 hours, apply a negative resist and apply 5
When a line and space pattern of 0 μm was exposed and developed and immersed in a hydrazine-ethylenediamine 1: 1 solution at 25 ° C. and 40 ° C. for 5 minutes, the film thickness decrease at 25 ° C. was as small as about 5 μm, and the substrate at 40 ° C. The surface was etched, but the wavy side etch was large and not practical.

Comparative Example 2 The solution obtained in Example 1 was spin-coated on a silicon substrate to a film thickness of about 25 μm and desolvated at 70 ° C. for 1 hour.
After baking at 0 ° C. for 2 hours, apply a negative resist and apply 5
Exposure and development of 0 μm line and space pattern, tetramethylammonium hydroxide 10w at 40 ° C
t%, ethylenediamine 20 wt%, urea 15 wt%,
When immersed in an etching solution containing 65 wt% of methanol for 5 minutes, the reduction in film thickness was about 5 μm, which was not practical.

[0030]

As is apparent from the examples, the etching solution of the present invention has a feature that the etching rate is high and side etching is small. Therefore, through holes and deep patterns can be formed in fine processing of polyimide. It has the effect of being able to.

Claims (4)

[Claims] 1. A quaternary ammonium hydroxide of 5 to 20 wt%, an amino alcohol of 10 to 60 wt% and 20 to 80 w.
An etching solution for polyimide, which comprises t% alcohol as an essential component. 2. The polyimide etching solution according to claim 1, wherein the amino alcohol is an aliphatic or alicyclic amino alcohol having 2 to 8 carbon atoms. 3. The etching solution for a polyimide according to claim 1, wherein the alcohol is an aliphatic alcohol having 1 to 6 carbon atoms. 4. When etching polyimide, the polyimide is a polyimide obtained by applying a polyimide precursor solution to a substrate, removing the solvent, and then baking at 200 to 300 ° C., and the pattern mask is a negative photoresist. The method of using an etching solution according to any one of claims 1 to 3, which is a mask obtained by coating and baking, exposing and developing a desired pattern, and the etching solution having a temperature of 10 to 60 ° C.