JPH0648381B2 - Positive photoresist composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to radiation sensitive positive photoresist compositions, and more specifically to metacresol,
The present invention relates to a positive photoresist composition containing a novolak resin obtained by condensing a mixture of para-cresol and xylenol with formaldehyde and a specific 1,2-naphthoquinonediazide-based photosensitizer.

The degree of integration of integrated circuits has been accelerated year by year, and at present, the era of so-called VLSI having an integration degree of 100,000 or more is being entered, and it is an era of designing a rule of 3 μm or a rule of 2 μm. As a result, the demand for photolithographic technology has become stricter year by year. In the photolithographic technique, most of the resists conventionally used are negative resists obtained by adding a photocrosslinking agent bisazide compound to cyclized polyisoprene rubber. However, this type of resist has a limited resolution due to swelling during development, and it is difficult to obtain a resolution of 3 μm.

A positive resist can meet the above demands. The positive resist composition contains an alkali-soluble phenol formaldehyde novolak resin, a photosensitive material,
It is generally included with a substituted naphthoquinone diazide. Naphthoquinonediazide absorbs ultraviolet rays as shown in the following formula upon irradiation, produces ketene via carbene, reacts with water present in the system to form indenecarboxylic acid, and this phenomenon is dissolved in the alkaline aqueous solution of the developing solution. ing.

In this way, the positive resist does not swell unlike the negative resist because an alkaline aqueous solution is used as the developing solution, so that the resolution can be increased.

As described above, the positive type photoresist is generally characterized by high resolution, but it is said to be inferior to the negative type photoresist in terms of half-surface sensitivity and adhesive strength. Of these, the adhesiveness can be improved by operations such as pretreatment of the substrate, but measures for sensitivity have been delayed. Further, generally, a positive type resist having a high resolution is used, but as the degree of integration increases, a resist having a higher resolution is required.

Furthermore, in the recent lithographic process, a process of performing reduced projection using monochromatic light with small light intensity to improve the resolution and exposing a wafer divided into many times is introduced. Furthermore, as the degree of integration increases, the figure to be drawn becomes more and more complicated, and as the number of exposures also increases, the proportion of exposure time that can be included in the entire process is increasing. Therefore, improving the sensitivity of the resist greatly improves the throughput of VLSI manufacturing, and further contributes to the cost performance by improving the throughput of the process using a small projection exposure machine and an extremely expensive machine. Is also extremely large. Under these circumstances, there has been a strong demand for the emergence of a positive resist which has improved resolution and improved sensitivity as compared with the conventional one.

However, in general, when the sensitivity is increased, the residual film ratio is lowered, and there are many disadvantages such as pinholes and other film defects.

The inventors of the present invention have paid particular attention to this point and, as a result, have conducted extensive studies, and as a result, by combining a specific 1,2-naphthoquinonediazide-based photosensitizer and a specific novolak resin, the sensitivity and the residual film rate are good. It was found that a positive photoresist composition with improved resolution can be obtained, and the present invention has been completed.

That is, the gist of the present invention is (a) 1,2-naphthoquinonediazide-5-sulfonic acid ester of 2,3,4-trihydroxybenzophenone, and 90% or more of which is a triester. 2-naphthoquinonediazide-based photosensitizer, and (b) a positive type resin containing a novolak resin obtained by condensing formaldehyde with a mixture of metacresol, paracresol and 2,5-xylenol It exists in a photoresist composition.

To explain the present invention below, the novolak resin of the present invention,
A mixture of meta-cresol, para-cresol and 2,5-xylenol, preferably a mixture of 10-80 mol% of meta-cresol, 10-80 mol% of para-cresol and 10-80 mol% of 2,5-xyler, more preferably,
Meta-cresol 10-50 mol%, para-cresol 40
~ 80 mol% and 2,5-xylenol 10-50 mol%
It is obtained by condensing a mixture of the above with formaldehyde according to a known method.

For example, a certain amount of meta-cresol, para-cresol and
A mixture of 2,5-xylenol and formaldehyde,
Acid, hydrochloric acid, phosphoric acid, etc. as catalyst
After reacting for 0.5 to 15 hours, the pressure is reduced to 100-
It can be easily obtained by heating at 250 ° C. to remove water and unreacted monomers. The novolak resin has a weight average molecular weight of 1,000 to 30,000, preferably 1,500 to 3, when the molecular weight is determined by using a gel permeation chromatography and having a polystyrene conversion value.
Those in the range of 15,000 are preferably used.

As the 1,2-naphthoquinonediazide-based photosensitizer, it is preferable that substantially all three hydroxyl groups of 2,3,4-trihydroxybenzophenone are esterified. More specifically, the proportion of the three molecules which have been esterified is 90% or more, preferably 95% or more, particularly preferably 98% or more. If the esterification rate is less than this, the apparent sensitivity will increase but the residual film rate will decrease. Such sensitizers are 2,3,4-
It can be easily synthesized by a known method in which trihydroxybenzophenone and 3-fold molar amount of 1,2-naphthoquinonediazide-5-sulfonyl chloride are reacted in the presence of a base in a solvent such as dioxane, cellosolve or acetone. It is possible. The esterification rate can be quantified by liquid chromatography according to a conventional method.

The ratio of the 1,2-naphthoquinonediazide-based photosensitizer to the novolak resin is 10 to 30 parts by weight, preferably 12 to 25 parts by weight of the photosensitizer per 100 parts by weight of the novolak resin.

Usually, these are dissolved in a suitable solvent before use. The solvent is not particularly limited as long as it is a solvent that does not react with the photosensitizer and novolak resin, has sufficient solubility, and gives good coating properties, but is not limited to methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl cellosolve acetate. ,
A cellosolve-based solvent such as ethyl cellosolve acetate,
Examples thereof include ester solvents such as butyl acetate and amyl acetate, highly polar solvents such as dimethylformamide and dimethylsulfoxide, mixed solvents thereof, and those to which aromatic hydrocarbon is added.

A good resist can be obtained by applying the resist composition to a substrate by a known method, exposing it to a predetermined pattern, and developing it.

The developer of the positive photoresist composition of the present invention contains sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, inorganic alkalis such as aqueous ammonia, ethylamine, n-propylamine and the like. Primary amines, diethylamine, di-n-
Secondary amines such as propylamine, tertiary amines such as triethylamine and methyldiethylamine, aqueous solutions of quaternary amines such as tetramethylammonium hydroxide and trimethylhydroxyethylammonium hydroxyoxide, or alcohols, interfaces It is possible to use those to which an activator or the like is added.

The positive photoresist composition of the present invention is useful not only for VLSIs, but also for general IC production, mask production, or offset printing.

Next, the present invention will be described in more detail with reference to specific examples.
The present invention is not restricted by the embodiments.

Synthesis Example 1 m-cresol 50 g (0.46 mol), p-cresol 1
00 g (0.93 mol), 2,5-xylenol 56 g (0.46 mol)
Mol), 120% (1.48 mol) of 37% formalin and 4.2 g of dihydrogen oxalic acid are reacted for 3 hours with stirring at 91 to 94 ° C. Then, the mixture was cooled to room temperature, decompressed to 30 mmHg and gradually heated again to expel water and residual monomer. Finally, the heating was finished up to 175 ° C. to complete the ejection. It took about 2 hours. The remaining resin was poured into a stainless steel butt and cooled.

The weight average molecular weight in terms of polystyrene was 3,200 by gel permeation chromatography.

Synthesis Example 2 2,3,4-trihydroxybenzophenone 2.0 g (8.7 mmol
e), 1,2-naphthoquinonediazide-5-sulfonic acid chloride 7.0g (26mmole) is dissolved in dioxane 57m,
While stirring, 3.2 g of triethylamine was added and the reaction was continued for 1 hour at 25 to 27 ° C. 100 m of water is added and the reaction product is precipitated and separated. The washing was repeated with water until the washing liquid had a pH of 7, and finally, it was suspended and washed in 100 m of ethanol, separated and dried. Yield 7.7 g (96%). As a result of analysis by liquid chromatography, the content of the esterified product was 98.1%.

Synthesis Example 3 In the same manner as in Synthesis Example 2 except that the molar ratio of 2,3,4-trihydroxybenzophenone and 1,2-naphthoquinonediazide-5-sulfonic acid chloride was 1: 2, A 2-naphthoquinonediazite type photosensitizer was obtained. As a result of analysis by liquid chromatography, the content of the esterified product was about 81%.

Example 1 Novolac resin synthesized as described in Synthesis Example 1.
3 g and 0.39 g of the photosensitizer obtained in Synthesis Example 2 were dissolved in 7.3 g of ethyl cellosolve acetate, and the mixture was passed through a 0.2 μ Millipore filter to prepare a positive type photoresist composition. This was spin-coated on a silicon wafer having a 5000 Å oxide film (SiO ₂ ) and prebaked at 90 ° C. for 30 minutes to obtain a 1.0 μm coating film. The sensitivity (represented by the relative value of the reciprocal of the minimum exposure time at which the residual film rate becomes 0) was determined using a stepper plate manufactured by Kodak Co., Ltd. and a mask aligner MA-10 manufactured by Mikasa Co., Ltd. The development was performed at 20 ° C. for 1 minute using a developer NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd. The results are shown in Table-1.

Example 2 A novolak resin synthesized in the same manner as in Synthesis Example 1 except that metacresol was 20 mol%, para-cresol was 60 mol%, and 2,5-xylenol was 20 mol%, and a photosensitive compound synthesized in Synthesis Example 2 was used. Using the agent, evaluation was performed in the same manner as in Example 1. The results are shown in Table-1.

Comparative Example 1 Metacresol 70 mol% and para-cresol 30
Mol% Novolac resin synthesized in the same manner as in Synthesis Example 1 except that 2,5 xylenol was not used, and Synthesis Example 2
Evaluation was carried out in the same manner as in Example 1 using the photosensitizer synthesized in 1. The results are shown in Table-1.

Comparative Example 2 Evaluation was performed in the same manner as in Example 1 except that the novolak resin synthesized in Synthesis Example 1 and the photosensitizer synthesized in Synthesis Example 3 were used. The results are shown in Table-1.

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Claims (3)

[Claims] 1. A) 1,2-naphthoquinonediazide-5-sulfonic acid ester of (3) 2,3,4-trihydroxybenzophenone, 90% or more of which is a triester.
1,2-naphthoquinonediazide-based photosensitizer, and (b) a novolak resin obtained by condensing a mixture of metacresol, para-cresol and 2,5-xylenol with formaldehyde. Positive photoresist composition. 2. The novolak resin is metacresol 1
0-80 mol%, para-cresol 10-80 mol% and
A photoresist composition according to claim (1), which is a resin obtained by condensing a mixture of 10 to 80 mol% of 2,5-xylenol with formaldehyde. 3. The weight average molecular weight of the novolak resin is 1,
Claims characterized by being 000-30,000
The photoresist composition according to items (1) and (2).