JPH0733874A - Production of polyimide precursor - Google Patents

Abstract

PURPOSE:To obtain the subject precursor free from contamination with ionic impurities (halogenated ions) and useful in the field of semiconductor material by carrying out transesterification of a specific ester with a polyamic acid. CONSTITUTION:This precursor having a structure of the formula III [R3 is H or organic group (containing CH2-O-R4); R4 is >=1C organic group] is produced by reacting (A) a compound of the formula I obtained by the reaction of (i) an organic carboxylic acid of the formula RCOOH (R is >=1C organic group; the dissociation constant in aqueous solution (Ka) is pKa<1.5) with (ii) a halogenated alkyl ether of the formula X-CH2-O-R5 (R5 is >=1C organic group; X is halogen) with (B) a polyamic acid having the structural unit of the formula II (bond shown by an arrow is a bond substitutable by isomerization; R1 is tetravalent aromatic or aliphatic hydrocarbon residue; R2 is bivalent aromatic or aliphatic hydrocarbon residue).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyimide precursor used for producing a heat-resistant positive photoresist free from ionic impurities.

[0002]

2. Description of the Related Art Conventionally, a heat-resistant photoresist made of a photosensitive polyimide or its precursor and its use are well known. For example, in the case of a negative type photoresist, the polyimide precursor is bonded through an ester bond or an ionic bond. Method of introducing methacryloyl group (Japanese Patent Laid-Open No. 49-1154)
1, JP-A-50-40922, and JP-A-54-40.
-145794, JP-A-56-38038), soluble polyimides having a photopolymerizable olefin (JP-A-59-108031, JP-A-59-22).
No. 0730, JP-A-59-232122, JP-A-60-6729, JP-A-60-72925, JP-A-61-57620), a benzophenone skeleton, and a nitrogen atom. Self-sensitized polyimide having an alkyl group at the ortho position of the aromatic ring to which is bonded (JP-A-59-219330 and JP-A-59-23153).
3), a polybenzoxazole precursor having heat resistance comparable to that of polyimide (Proceedings of Annual Meeting of the Polymer Society of Japan,
p664, 1988) and the like have been proposed.

On the other hand, in the positive type, a method of introducing an o-nitrobenzyl group into a polyimide precursor through an ester bond (J. Macromol. Sci. Chem., A24, 10 , 1407, 1987), soluble hydroxylimide or poly A method of mixing a naphthoquinonediazide compound with an oxazole precursor (JP-B-64-60630, U.S. Pat. No. 4,395,548).
No. 2), a method of introducing naphthoquinonediazide into a soluble polyimide through an ester bond (Macromolecules, 2
3,1990), a chemically amplified polyimide (Japanese Patent Laid-Open No. 3-76).
3), a method in which a naphthoquinonediazide is mixed with a polyimide precursor (JP-A-52-13315), and the like.

However, in the negative type, there are problems in resolution due to its function, and depending on the application, the yield at the time of manufacturing may be reduced. Further, in the above-mentioned ones, since the structure of the polymer used is limited, the physical properties of the film finally obtained are limited, which is not suitable for multipurpose use. On the other hand, even in the positive type, the sensitivity and resolution are low due to the problems associated with the absorption wavelength of the photosensitizer as described above, and the structure of the above is also limited, and therefore, the same problems as those from the above limitation are caused. Further, in the above, there is a problem of film loss due to high temperature processing after image formation, and it is the actual situation that it has not yet been put to practical use. Furthermore, in recent years, a chemically amplified photosensitive composition has been proposed in which a resin component in which a specific protecting group is introduced into a carboxyl group of a polyimide precursor and a compound which exhibits acidity upon irradiation with actinic rays are blended (Japanese Patent Laid-Open No. Hei 10 (1999) -242242). 4-120
171). When a tetrahydropyranyl group, a 1-ethoxyethyl group, a methoxymethyl group, or a trimethylsilyl group is used as a protective group in this composition, the sensitivity is good, but these protective groups are likely to be eliminated, which causes a problem in solution storability. However, it is still insufficient in practical use.
Also, as a protecting group, a methyl group, an ethyl group, a propyl group,
When a butyl group, a benzyl group or the like is used, even if heating is used together with acid generation by irradiation with an actinic ray, the elimination reaction of the protective group is difficult to sufficiently occur, and it is hard to say that it is a practical level resist. .

Further, in JP-A-4-120171, a polyimide precursor is obtained by condensing a tetracarboxylic acid diester, but it is difficult to obtain a high molecular weight polyimide precursor, and as a result, finally obtained. It is difficult to say that the resist film obtained is practically satisfactory in terms of physical properties, particularly mechanical strength. Furthermore, when a halogenated methyl alkyl ether is used in the preparation of the polyimide precursor, halogenated ions are generated,
This is a serious drawback in semiconductor materials such as sealing materials, insulating films, and buffer coat films.

[0006]

It is an object of the present invention to provide a polyimide precursor used in the above conventional heat-resistant photoresist, which is free from halogen ion contamination which is a problem particularly in the field of semiconductor materials. To provide a method of obtaining.

[0007]

Means for Solving the Problems As a result of intensive studies made by the present inventors, an ester obtained from a specific organic carboxylic acid and a halogenated methyl ether was used to conduct a transesterification reaction between this and a polyamic acid. It was found that a polyimide precursor capable of achieving the above-mentioned object can be obtained by carrying out, and the present invention has been completed.

That is, the method for producing a polyimide precursor of the present invention comprises: an organic carboxylic acid represented by the following (Chemical Formula 6):
(Chemical Formula 7), which is a reaction product with a halogenated methyl ether represented by (Chemical Formula 7), is reacted with a polyamic acid having a structural unit represented by (Chemical Formula 9), and represented by (Chemical Formula 10). And a polyimide precursor having a structural unit shown in FIG.

[0009]

[Chemical 6]

(However, the dissociation constant Ka in the aqueous solution is p
Ka <1.5, and in the formula, R is an organic group having 1 or more carbon atoms. )

[0011]

[Chemical 7]

(In the formula, R ₅ is an organic group having 1 or more carbon atoms, and X is a halogen atom.)

[0013]

[Chemical 8]

(In the formula, R and R ₅ are organic groups having 1 or more carbon atoms.)

[0015]

[Chemical 9]

(However, the arrow bond in the formula represents a bond which can be replaced by isomerization, R ₁ is a tetravalent aromatic or aliphatic hydrocarbon residue, and R ₂ is a divalent aromatic or aliphatic hydrocarbon residue. It is a hydrocarbon residue.)

[0017]

[Chemical 10]

(However, the arrow bond in the formula represents a bond which can be substituted by isomerization, R ₁ is a tetravalent aromatic or aliphatic hydrocarbon residue, and R ₂ is a divalent aromatic or aliphatic hydrocarbon residue. It is a hydrocarbon residue, and R ₃ is a hydrogen atom or an organic group (-C
Containing _{H 2 -O-R 4),} R 4 is one or more organic groups carbon atoms. The organic carboxylic acid represented by the formula (6) used in the present invention is a carboxylic acid having an organic group having 1 or more carbon atoms, preferably 1 to 3, and has a dissociation constant K in an aqueous solution.
a shows pKa <1.5. pKa is 1.
When it is 5 or more, the introduction rate of the oxymethyl group introduced into the polyamic acid by transesterification in a later step becomes low, which is not preferable.

R in such an organic carboxylic acid is specifically an electron-withdrawing group such as a perfluoroalkyl group typified by a trifluoromethyl group or a halogenated alkyl group typified by a trichloromethyl group. And the like. Of these, it is preferable to use a perfluoroalkyl group because it can be distilled at a low boiling point, and when it is mixed in the polyimide precursor, it is decomposed by heating at a high temperature and halogen ions are not generated.

On the other hand, the halogenated methyl ether represented by (Chemical formula 7) is to be reacted with the organic carboxylic acid represented by the above-mentioned (Chemical formula 6), and is dehydrohalogenated to produce (Chemical formula 8). The indicated ester is formed. Examples of such a halogenated methyl ether include methyl, ethyl, propyl, benzyl, methoxymethyl as R ₅ ,
An alkyl group having 1 or more carbon atoms such as methoxyethyl, ethoxymethyl, and ethoxyethyl can be used, and it is preferable to use an alkyl group having 1 to 4 carbon atoms. As the halogen, chloro (Cl), bromo (Br), iodo (I) or the like can be used.

In the production method of the present invention, the above (Chemical formula 6)
The oxymethyl ester of the halogenated alkylcarboxylic acid shown in (Formula 8) is prepared by reacting the compound shown in and (Formula 7). As the preparation method, for example, the organic carboxylic acid shown in (formula 6)
It is dissolved in an organic solvent such as ether together with a double molar equivalent of a basic catalyst such as triethylamine, and 0.9 times molar equivalent of the halogenated methyl ether shown in Chemical formula 7 is added dropwise for reaction. After the reaction, the produced hydrochloride can be filtered and removed, and the filtrate can be distilled off with ether to obtain the residue by a known purification means such as distillation or recrystallization.

The compound represented by (Chemical Formula 8) thus obtained is ionic even in the mixing of ionic impurities, which is a problem in the field of semiconductor materials, and in the esterification reaction with polyamic acid which is the next step. There is no possibility of generation of impurities.

In the present invention, the compound represented by (Chemical formula 8) obtained as described above is reacted with a polyamic acid having a structural unit represented by (Chemical formula 9) to produce a compound represented by (Chemical formula 10). A polyimide precursor having a structural unit is obtained.

R ₁ in the structural unit represented by the chemical formula 9 is
Specifically, a tetravalent aromatic or aliphatic hydrocarbon residue having a skeleton such as benzene, naphthalene, perylene, diphenyl, diphenyl ether, diphenyl sulfone, diphenyl propane, diphenyl hexafluoropropane, benzophenone, butane, cyclobutane is typical. However, the present invention is not limited to these. Preferred groups are phenyl, biphenyl, diphenyl ether and benzophenone. In addition, two or more kinds of the groups exemplified above may be contained as R ₁ if necessary.

Further, as R ₂ , specifically, diphenyl ether, diphenyl thioether, benzophenone, diphenylmethane, diphenylpropane, diphenylhexafluoropropane, diphenyl sulfoxide,
A divalent aromatic or aliphatic hydrocarbon residue having a skeleton such as diphenyl sulfone, biphenyl, pyridine or benzene is exemplified as a typical example, but the present invention is not limited thereto. Preferred groups are diphenyl ether, diphenyl sulfone, and benzene. If necessary, R ₂ may contain two or more types of the groups exemplified above.

Further, R in the structural unit in the polyimide precursor having the structural unit of (Chemical Formula 10) finally obtained
₃ and R ₄ are protective groups which are bonded to a carboxyl group, and at least one of the carboxyl groups contained in the polyamic acid shown in Chemical formula 9 is protected by an oxymethyl group (alkoxymethyl group). R ₃ is a hydrogen atom or an organic group (including —CH ₂ —O—R ₄ ), and R ₄ is an organic group having 1 or more carbon atoms. R ₃ is a hydrogen atom or an organic group (including —CH ₂ —O—R ₄ ), and a part thereof may be a hydrogen atom in order to balance the solubility and the contrast during exposure. On the other hand, specific examples of R ₄ include a methyl group, an ethyl group, an isopropyl group, a methoxyethyl group and a benzyl group.

Obtained by the production method of the present invention (Chemical Formula 1
In the polyimide precursor having the structural unit of 0), an oxymethyl group as a protective group is bonded to at least one of the carboxyl groups in the polyimide precursor as described above. The introduction rate is preferably 20 mol% or more, and more preferably 40 mol% or more with respect to the amount (concentration) of the carboxyl group of the polyimide precursor in order to reduce film loss during development.

The above polyimide precursor can be obtained, for example, by the following method.

[0029] with an aromatic or aliphatic tetracarboxylic acid dianhydride having in the R ₁ molecule, approximately equimolar amounts of aromatic or aliphatic diamines having in the R ₂ molecule, N- methyl-2 -Reacting in an organic solvent such as pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, hexamethylphosphoramide to prepare a polyamic acid (Formula 9).

Next, the polyamic acid (Chemical Formula 9) obtained by the above reaction is diluted to an appropriate concentration, and the compound (Chemical Formula 8) prepared above is added to a tertiary aliphatic amine such as triethylamine or diisopropylamine or pyridine, A polyimide precursor having a structural unit represented by (Chemical Formula 10) can be obtained by adding it together with a basic catalyst such as imidazole, reacting it under cooling or at room temperature, reprecipitating, filtering and purifying. The obtained polyimide precursor (Chemical Formula 10) is N,
It is stable for a long time in an organic solvent such as N-dimethylacetamide or N-methylpyrrolidone, and has excellent storage stability in a solution state.

The polyimide precursor having the structural unit of (Chemical Formula 10) obtained by the present invention is a compound that exhibits acidity upon irradiation with actinic rays (photo-acid generator) or a basic compound when heated with the photo-acid generator. A heat-resistant positive photoresist composition can be obtained by blending with a compound (thermal base generator) to be exhibited.

In the above composition, the photo-acid generator becomes acidic upon irradiation with actinic rays such as ultraviolet rays and acts on the oxymethyl group as a protecting group in the polyimide precursor (Chemical Formula 10) to eliminate the protecting group. Has the effect of causing. Specific examples of such a compound include diallyl sulfonium salt, triallyl sulfonium salt, dialkyl phenacyl sulfonium salt, allyl diazonium salt, aromatic tetracarboxylic acid ester, aromatic sulfonic acid ester, nitrobenzyl ester, and aromatic sulfamide. , Naphthoquinonediazide-4-sulfonic acid ester and the like are used. Such compounds can be used in combination of two or more kinds as required, or can be used in combination with other sensitizers,
The amount is 5 to 50 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the polyimide precursor.
If the compounding amount is small, the sensitivity is lowered, and if the compounding amount is large, the physical properties of the film after high temperature curing, the storability of the solution and the imageability may be adversely affected.

When the heat-resistant positive photoresist composition contains a photo-acid generator and a thermal base generator,
Since the thermal base generator exhibits basicity when heated, it has a function of neutralizing the acid generated by the decomposition of the photo-acid generator. Therefore, when the composition of the present invention is used for a wiring board or the like, it is possible to effectively prevent corrosion of the metal wiring due to an acid, and it is possible to improve the film strength after heating at a high temperature. Specific examples of such a compound include carbamate derivatives such as 1-methyl-1- (4-biphenylyl) ethyl carbamate and 1,1-dimethyl-2-cyanoethyl carbamate, urea and N, N-dimethyl-N. A urea derivative such as'-methylurea, a dihydropyridine derivative such as 1,4-dihydronicotinamide, a quaternized ammonium salt of organosilane or organoborane, or dicyandiamide is used. Such thermal base generators can be used in combination of two or more, if necessary, and are contained in the range of 0.1 to 10 molar equivalents, preferably 0.8 to 4 molar equivalents relative to the photoacid generator. Let When the content is low, the acid generated by heating the photo-acid generator cannot be sufficiently neutralized, and when it is high, the solution storability, image quality, and film physical properties after high temperature curing are adversely affected. May be given.

Next, an example of a method for forming an image using the above heat resistant positive photoresist composition will be shown.

First, the above-mentioned polyimide precursor (Chemical Formula 10), a compound which exhibits acidity upon irradiation with actinic rays (photoacid generator), and a compound which exhibits basicity upon heating (thermal base generation) Agent) to be used in combination with the organic solvent to prepare a photosensitive solution. Next, this photosensitive solution is applied onto a substrate so that the film thickness after drying is 1 to 50 μm, preferably 5 to 30 μm.

After the applied coating film is dried, it is exposed to light through an ordinary photomask, and after exposure, post-heating (80-
After 150 ° C.), a developing process is performed using a dipping method, a spray method, or the like to remove the irradiated portion. The developer used at this time is preferably one capable of completely dissolving and removing the exposed film within a suitable time, and an inorganic alkaline aqueous solution such as sodium hydroxide or potassium hydroxide, or propylamine, butylamine, monoethanolamine, or tetraethylamine. Methyl ammonium hydroxide (hereinafter TM
AH), an organic alkaline aqueous solution such as choline, or the like is used alone or in combination of two or more. Further, the alkaline aqueous solution may contain organic solvents such as alcohols and various surfactants, if necessary.

After development, a positive type image having a desired pattern is obtained by washing with a rinse liquid.

The image obtained as described above becomes a polyimide image having heat resistance and practical mechanical strength by being subjected to high temperature heat treatment (about 200 to 400 ° C.).

[0039]

EXAMPLES The present invention will be described in more detail below by showing Examples of the present invention.

Example 1 About equimolar amounts of tetracarboxylic dianhydride and diamine having R ₁ and R ₂ shown in Table 1 were converted into dimethylacetamide (hereinafter referred to as DMAc) or N-methyl-
Reaction was carried out in 2-pyrrolidone (hereinafter referred to as NMP) at room temperature to obtain polyamic acid solutions No. 1 to 3 having the structural unit shown in (Chemical Formula 9).

[0041]

[Table 1]

On the other hand, trifluoroacetic acid was diluted with diethyl ether, and 1.1 times molar equivalents of triethylamine and 0.9 times molar equivalents of chloromethylethyl ether were added dropwise thereto in an ice-water bath, followed by stirring for 2 hours. And reacted.

After the reaction was completed, the filtrate obtained by filtering the reaction solution was distilled to collect a fraction at 45 ° C. It was confirmed by ¹ H-NMR, ¹³ C-NMR and the like that the obtained liquid was trifluoromethylcarbonyloxymethyl ethyl ether (hereinafter referred to as TFME) represented by the following (Chemical Formula 11).

[0044]

[Chemical 11]

Then, the polyamic acid solutions No. 1 to 3 prepared above were diluted until a uniform reaction was possible,
The above TFM for the carboxyl group in the polyamic acid
1.3 times the molar equivalent of E, and triethylamine 1.2
A double molar equivalent was added, and the mixture was stirred at 0 ° C to room temperature for about 2 hours.
Next, reprecipitation treatment was performed with methanol, and the precipitate was vacuum dried to obtain a solid content of the polyimide precursor represented by (Chemical Formula 10). ^When confirmed by ¹ H-NMR, 80 to 9 of all carboxyl groups in the polyamic acid were confirmed.
0% was substituted with ethoxymethyl groups.

The solid content thus obtained was redissolved in NMP, and naphthoquinonediazide-4-sulfonic acid benzophenone ester (hereinafter referred to as "photoacid generator") was added to the solution.
NQDS) was added in an amount of 0.05 equivalent mol based on the concentration of the carboxyl group in the polyamic acid.

These solutions were spin-coated on a silicon wafer to form a coating film having a dry film thickness of 18 to 22 μm,
After that, vacuum contact exposure was performed for 3 minutes at a distance of 30 cm from the light source using a 250 W ultra-high pressure mercury lamp through the glass film.

After exposure, heat at 110 ° C. for 10 minutes, and
After developing with a 5 wt% TMAH aqueous solution until the exposed surface of the silicon wafer is exposed, rinse with water, and the residual film thickness rate after development shown in Table 2 and high temperature heating (360 ° C / 1 hour) according to the following calculation formula. The residual film thickness ratio and the aspect ratio afterward were calculated. The film thickness and pattern width of the unexposed portion in the calculation formula were obtained by a surface roughness meter.

Residual film thickness after development = (film thickness of unexposed area after development) / (film thickness of unexposed area before development)

Ratio of residual film thickness after high temperature heating = (residual film thickness of unexposed portion after high temperature heating) / (film thickness of unexposed portion before development)

Aspect ratio = (pattern thickness) / (pattern width)

[0052]

[Table 2]

Further, the stability of solution storage of the above composition at 4 ° C. was examined by examining the introduction rate of oxymethyl group in the carboxyl group by ¹ H-NMR spectrum. As a result, the spectrum remained almost unchanged even after 3 months, and the development characteristics such as the residual film thickness ratio and the aspect ratio after development and after high temperature heating were almost unchanged from those at the time of solution preparation, and were extremely stable. It was

Example 2 Instead of trifluoroacetic acid in Example 1, trichloroacetic acid (pKa = 0.66) and oxalic acid (pKa = pKa =
A polyimide precursor was prepared in the same manner as in Example 1 except that 1) and nitroacetic acid (pKa = 1.46) were used. As a result, the introduction rate of the ethoxymethyl group into the polyamic acid was 80 to 95%, and the introduction was extremely efficient.

Comparative Example 1 In place of trifluoroacetic acid in Example 1, acetic acid (pKa = 4.8), benzoic acid (pKa = 4.20),
Maleic acid (pKa = 1.75), formic acid (pKa = 3.
A polyimide precursor was prepared in the same manner as in Example 1 except that 55) was used. As a result, the introduction rate of the ethoxymethyl group into the polyamic acid was 50% or less, and the introduction efficiency was poor.

[0056]

According to the manufacturing method of the present invention, a photosensitive polyimide precursor useful as a skeletal polymer of a heat-resistant positive photoresist can be obtained. Since this polyimide precursor has the carboxyl group in the polyamic acid esterified with a specific protecting group, the protecting group can be easily removed by adding a photoacid generator and irradiating it with an actinic ray such as ultraviolet rays. Release to become an alkali-soluble polyamic acid. Therefore, it is possible to obtain a positive type pattern having a high sensitivity and a high resolution, which cannot be achieved by the conventional heat-resistant photoresist composition, and which can be put to practical use. Furthermore, since an oxymethyl group is introduced as a protective group, the storage stability in a solution state will be significantly improved.

Furthermore, the polyimide film finally obtained by heating at high temperature from the heat-resistant positive photoresist composition obtained from the polyimide precursor obtained by the production method of the present invention has heat resistance, electrical characteristics and mechanical characteristics. Therefore, it can be suitably used as a material for forming a protective film or an insulating film for a solid element or a circuit board in the semiconductor industry.

In particular, according to the manufacturing method of the present invention, since ionic impurities (halogenated ions) are not mixed, it is extremely useful for use in the field of semiconductor materials which are adversely affected by such impurities.

Claims (1)

[Claims] 1. A reaction product of an organic carboxylic acid represented by the following (Chemical formula 1) and a halogenated alkyl ether represented by the (Chemical formula 2) to (Chemical formula 4) A method for producing a polyimide precursor, which comprises reacting a polyamic acid having a structural unit represented by the following formula to obtain a polyimide precursor having a structural unit represented by Chemical formula 5. [Chemical 1] (However, the dissociation constant Ka in the aqueous solution is pKa <1.5.
And in the formula, R is an organic group having 1 or more carbon atoms. ) [Chemical 2] (However, in the formula, R ₅ is an organic group having 1 or more carbon atoms, and X is
Is a halogen atom. ) [Chemical 3] (However, in the formula, R and R ₅ are organic groups having 1 or more carbon atoms.) (However, the bond of the arrow in the formula represents a bond which can be replaced by isomerization, R ₁ is a tetravalent aromatic or aliphatic hydrocarbon residue, and R ₂ is a divalent aromatic or aliphatic hydrocarbon residue. It is a group.) (However, the bond of the arrow in the formula represents a bond which can be replaced by isomerization, R ₁ is a tetravalent aromatic or aliphatic hydrocarbon residue, and R ₂ is a divalent aromatic or aliphatic hydrocarbon residue. a group, R ₃ is a hydrogen atom or an organic group (-CH ₂ -O-R
Including _4), R ₄ is one or more organic groups carbon atoms. )