JP2511651B2 - How to form a pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is a method for forming a predetermined pattern from a photocrosslinkable polymer composition used as a precursor when forming an interlayer insulating film in the semiconductor industry. It is about.

[Prior art]

In recent years, in the semiconductor industry, a resin having a heterocycle, such as a polyimide resin, which has high heat resistance and is excellent in step formability as compared with an inorganic substance, is used as an insulating film or a passivation film in a solid element, or as an integrated circuit or a multilayer printed wiring. It has come to be used as an interlayer insulating film of a plate.

When forming an interlayer insulating film, it is necessary to provide via holes for establishing conduction between upper and lower layers, and as a method therefor, a pattern forming method using a photosensitive polyimide precursor composition or the like having excellent processability is used. Is proposed.

Among these materials used for pattern formation, the photocrosslinkable polymer composition having the repeating unit represented by the formula [I] is excellent in thick film forming property and has no film loss at the exposed portion during development. It has excellent features such as

The pattern forming method using the composition is performed, for example, in the following order of steps.

(1) Application: The precursor composition varnish is applied on a predetermined substrate.

(2) Drying: The solvent is evaporated to form a coating film of the precursor composition.

(3) Exposure: Exposure is performed using a predetermined photomask.

(4) Development: The unexposed area is dissolved and removed with a developing solution, and further washed with a rinse solution to obtain a pattern.

(5) Thermosetting: By heating, it is converted into a heat resistant resin such as a polyimide resin to obtain a predetermined pattern.

As a conventional developing solution in a series of steps, for example, a developing solution of dimethylacetamide alone or a developing solution of a mixed solvent of dimethylformamide and xylene in a volume ratio of 1: 1 (volume ratio) is used. A mixture of solvent and antisolvent has been used.

[Problems to be solved by the invention]

However, in the case of forming a pattern by the above method, since the development allowable range is narrow, swelling of the exposed portion and further elution occur if the development time becomes slightly longer than the set time, resulting in pattern sag and undeveloped residue. However, there is a problem that it occurs and the resolution becomes poor. In the worst case, for example, a thin film may remain on the bottom of the via hole, or the patterns may adhere to each other to fill the space. Further, when the developer is used after being left for several hours, the developer is deteriorated due to, for example, volatilization or moisture absorption of the poor solvent of the precursor, resulting in a problem that the development time is significantly deviated. It has occurred.

[Means for solving problems]

In order to solve the above-mentioned problems, in the past, the exposure amount was increased to deal with over-development and deterioration of the developer, but at the same time as the process problem that the exposure time becomes long, the pattern portion becomes thick and the resolution is poor. There is a new problem of becoming.

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems of the prior art, and as a result, by using a developing solution having a wide development allowable range and not changing with time as described in detail below. , Was able to provide high resolution patterns.

That is, the present invention provides a method of forming a predetermined pattern from a photocrosslinkable polymer composition having a repeating unit represented by the formula [I], in which a good solvent alone or a good solvent and a poor solvent of the polymer are combined. The present invention relates to a pattern forming method, which comprises using a developing solution containing 92% by volume or more and 99% by volume or less of mixed solvent and 1% by volume or more and 8% by volume or less of water.

[Wherein X is a (2 + n) -valent carbocyclic or heterocyclic group, Y is a (2 + m) -valent carbocyclic or heterocyclic group, Z
Is R is a covalent bond group having a carbon-carbon double bond, W is a group capable of reacting with a carboxyl group of -COOR to form a ring by heat treatment, n is 1 or 2, m is 0, 1 or 2, Moreover, COOR and Z are in the ortho position or the peri position. The photo-crosslinkable polymer having the repeating unit represented by the formula [I] used in the present invention is typically pyromellitic anhydride, benzophenonetetracarboxylic acid anhydride, biphenyltetracarboxylic acid. Tetracarboxylic acid anhydride such as anhydride, 4,4'-diaminodiphenyl ether, 4,4 '
-Diaminodiphenyl sulfone, polyimide precursor having a photosensitive group in the side chain of the repeating unit produced by polycondensation with diamine such as 4,4'-diaminodiphenylmethane, but not limited to these .

As the photosensitive group introduced into the precursor, a group having a carbon-carbon double bond capable of being dimerized or polymerized by light is typical, and a vinyl group, an allyl group, an acryl group, a methacryl group, a cinnamyl group. A group having a maleimide group or the like is mentioned as a preferable example.

The bonding form of the photosensitive group generally includes covalent bond such as ester bond and amide bond and ionic bond. For example, in the case of a polyimide precursor in which a photosensitive group is introduced by an ionic bond as disclosed in JP-A-54-145794, there is a problem that the exposed portion is reduced during development. Further, for example, in the case of an interlayer insulating film of a hybrid integrated circuit or the like, a film thickness of 10 μm or more is required, but the polymer concentration cannot be increased because of an ionic bond in the molecule, and therefore, it is possible to apply it only once. It is not possible to obtain a coating film having a high film thickness. further,
Since the ionic bond is easily hydrolyzed by moisture in the air, there are problems in storage method and storage stability.

On the other hand, in the case of covalent bond such as ester bond and amide bond as described in U.S. Pat. The sex is also good. Also, the storage stability is extremely good.

From the above points, a covalent bond such as an ester bond or an amide bond is used as the bonding form of the photosensitive group.

Examples of the photosensitive compound mixed for the purpose of improving the photosensitivity of the photocrosslinkable polymer having the repeating unit represented by the formula [I] include the following examples of sensitizers.
It is not limited to these. For example, benzophenone, 4,
Benzophenones such as 4'-bis (dimethylamino) benzophenone, benzoin ether or anthraquinone, or thioxanthone derivatives, 2,6-bis- (4'-
Diethylaminobenzal) -cyclohexanone and other bisazides, 1-phenyl-5-mercaptotetrazole and other mercapto compounds, 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) -oxime and other oximes, 2,4 Examples include imidazoles, such as 5,5-triphenylimidazolyl dimer.

Further, the following are preferable examples of the photosensitive monomer, but the photosensitive monomer is not limited thereto. For example, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, (meth) acrylates such as dimethylaminoethyl methacrylate, mercapto compounds such as thioglycolic acid,
Examples thereof include maleimides such as phenylsulfonylmaleimide, and isocyanates such as ethyl methacrylate isocyanate.

These additives to 100 parts by weight of photocrosslinkable polymer
It is preferable to add 0.1 to 50 parts by weight.

As the solvent, N, N'-dimethylformamide, N, N '
-Dimethylacetamide, γ-butyrolactone, N-methylpyrrolidone and the like are mentioned as preferable examples.

As a coating method on the substrate, a spinner, a roll coater or the like is typical, and as the substrate, a silicon wafer, a gallium arsenide substrate, glass, ceramics, a copper plate or a substrate having elements formed on these substrates is used. As a representative example, the present invention is not limited to these.

Drying methods include, but are not limited to, circulating ovens, hot plates, and infrared heaters. The drying temperature is preferably 50 to 140 ° C, more preferably 60 to 90 ° C. The drying time varies depending on the film thickness, but is 3 minutes to 15 hours. The film thickness is preferably 0.
The thickness is 1 to 200 μm, but the thickness is not limited to this.

As a method of exposure, it is preferable to irradiate ultraviolet rays through a photomask by an exposure device used in a normal photoresist process. The exposure time depends on the type of photocrosslinkable polymer,
Although it depends on the kind of the additive and the light intensity of the exposure machine, generally, the optimum time may be selected from 1 second to 30 minutes. If heat treatment is performed after exposure, the exposure time can be shortened by 2 to 5 times. The heat treatment temperature is preferably 40 to 140 ° C, more preferably 60 to 100 ° C. The heat treatment time varies depending on the temperature, but is preferably 1 second to 1 hour, and the heating method includes, but is not limited to, a circulation oven, a hot plate, and an infrared heater.

As the developing solution, one prepared by adding water to a good solvent for the polymer alone or a mixed solvent obtained by combining a good solvent and a poor solvent is used. By adding these, the viscosity of the developing solution can be lowered, so that the difference in dissolution rate between the exposed portion and the unexposed portion becomes large, and the development allowable range can be widened. In addition, there is no change over time.

As a good solvent, N, N'-dimethylformamide, N,
Examples include N′-dimethylacetamide, cyclopentanone, cyclohexanone, N-methylpyrrolidone, γ-butyrolactone, dimethylsulfoxide, hexamethylphosphoric triamide, acetonitrile, tetrahydrofuran, etc., as long as they dissolve the polymer, It is not limited to these. Further, these may be used alone or in a mixture of two or more kinds.

Examples of the poor solvent include, but are not limited to, toluene, xylene, ethylbenzene, isopropylbenzene, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, n-propyl alcohol, isobutyl alcohol, and ethanol. Further, these may be used alone or as a mixture of two or more kinds, and there is no particular limitation as long as the mixing ratio with the good solvent is within the range in which the polymer is dissolved in the final developer composition containing water. In the present invention, an extremely sharp pattern can be formed by using such a developing solution.

The optimum amount of water added may be selected from the range of 1 to 8% by volume, which is suitable for the type of the polymer and the type of the additive.
Addition of such water has the effect of providing a wide range of tolerance and sharpness of the pattern during development.

If added in excess of these ranges, development becomes impossible, or even if development is possible, it takes an extremely long time, the amount of undeveloped residue increases, and the swelling and pattern sag of the exposed area are remarkable. Moreover, it is preferable to use ion-exchanged water as the water from the viewpoint of application to the semiconductor industry.

As a developing method, spray development, immersion development, and ultrasonic development are mentioned as favorable examples, and the spray development is the one that can obtain the highest resolution.

The developed pattern image of the polymer composition is immediately rinsed with a rinse to remove the developer. As the rinse liquid, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, methanol, ethanol,
Examples include, but are not limited to, n-propyl alcohol, isopropyl alcohol, toluene, xylene, ethylbenzene, water and the like. Further, these may be used alone or in a mixture of two or more kinds.

The conversion of the obtained polyimide precursor pattern into polyimide is carried out by thermosetting at 200 to 500 ° C. for 5 minutes to 3 hours. Examples of the method include, but are not limited to, a circulation oven, a hot plate, and an infrared heater.

〔The invention's effect〕

If pattern formation is performed using the photocrosslinkable polymer composition according to the method of the present invention, the development allowable range, which has been a problem in the past, is significantly widened, and further, the deterioration of the developer is eliminated, so that the exposure time is lengthened. Moreover, it is not necessary to strictly control the developing time, and an extremely high-resolution pattern can be provided.

〔Example〕

Next, the present invention and its effects will be described with reference to examples, but the present invention is not limited to these.

Reference Example 1 100 ml of γ-butyrolactone and pyromellitic anhydride 2
1.8 g, 2-hydroxyethyl methacrylate 27.0 g and pyridine 33.0 g were dissolved and stirred for 15 hours at room temperature. Next, 23.8 g of thionyl chloride was added dropwise with stirring. Further, 16 g of 4,4'-diaminodiphenyl ether slurried with 50 ml of γ-butyrolactone was added dropwise under ice cooling and stirred for 2 hours, and then added dropwise to 10 l of ion-exchanged water while stirring, The precipitate was filtered, washed and air-dried to obtain a pale yellow powder. 10 g of this powder, 1.5 g of trimethylolpropane triacrylate and 0.6 g of Michler's ketone were added to 15 ml of N-methylpyrrolidone to obtain a uniform solution S-1.

Reference Example 2 The same operation was performed below, except that 21.8 g of pyromellitic anhydride in Reference Example 1 was replaced with 32.2 g of benzophenone tetracarboxylic acid anhydride. This solution is hereinafter referred to as S-2.

Reference Example 3 110 g of diaminodiphenyl ether was dissolved in 278 g of N-methylpyrrolidone to prepare an amino solution. 120 g of pyromellitic dianhydride was dispersed in 308 g of dimethylacetamide, and then 184 g of N-methylpyrrolidone was added and dissolved to obtain an acid solution. An acid solution was added to the amine solution at 60 ° C., and the mixture was reacted for 3 hours to obtain a uniform solution.

50 g of this solution, a solution of 1.15 g of Michler's ketone dissolved in 30 g of dimethylacetamide and a solution of 0.2 g of diethylaminoethyl methacrylate dissolved in 10 g of dimethylacetamide were mixed and passed. This solution is referred to below as S-3
Called.

Example 1 S-1 was applied onto a silicon wafer using a spinner and dried in a circulating oven at 70 ° C. for 2 hours. Film thickness is 20
μm. 5μm-100μm square (5μm
A photomask on which a through-hole test pattern of (steps) was printed was brought into close contact, and exposed for 110 seconds using a MA-10 exposure machine manufactured by Mikasa Co., Ltd. Next, spray development is carried out for 30 seconds with a developing solution of N, N'-dimethylacetamide / ethyl cellosolve / water (70/25/5, volume ratio), followed by acetone /
Spray rinse was performed for 15 seconds with a rinse solution of methanol (1/3, volume ratio). The resolution (minimum via hole diameter) of the obtained pattern was 20 μm. The image was sharp and no pattern swelling or elution was observed.

Comparative Example 1 A coating film was formed in the same manner as in Example 1, and after exposing for 110 seconds,
Spray development was carried out with a developer of N, N'-dimethylacetamide / ethyl cellosolve / water (60/20/20, volume ratio), but it took 50 seconds. The resolution of the obtained pattern was 35 μm, and the swelling of the pattern was remarkable.

Examples 2 to 5 Experiments were conducted by changing the conditions such as the composition of the developing solution and the developing time. The equipment used is the same as in Example 1.

Comparative Examples 2 to 10 Comparative experiments were carried out by changing the conditions such as developing solution composition, developing time, and composition solution. The equipment used is the same as in Example 1.

The conditions and results of the above Examples and Comparative Examples are summarized in Table 1.

Claims (1)

(57) [Claims] 1. A method for forming a predetermined pattern from a photocrosslinkable polymer composition having a repeating unit represented by the formula [I], which comprises mixing a good solvent of the polymer alone or a combination of a good solvent and a poor solvent. A pattern forming method comprising using a developing solution containing water in an amount of 92% by volume or more and 99% by volume or less and 1% by volume or more and 8% by volume or less of a solvent. [Wherein X is a (2 + n) -valent carbocyclic or heterocyclic group, Y is a (2 + m) -valent carbocyclic or heterocyclic group, Z
Is R is a covalent bond group having a carbon-carbon double bond, W is a group capable of reacting with a carboxyl group of -COOR to form a ring by heat treatment, n is 1 or 2, m is 0, 1 or 2, Moreover, COOR and Z are in the ortho position or the peri position. )