JPH0690441B2 - Positive photoresist composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates generally to a positive-type photoresist composition that is sensitive to broad-ray radiation, and more specifically to an alkali-soluble resin and a 1,2-naphthoxine diazide group. The present invention relates to an improvement in a positive photoresist composition produced from a compound containing

(Prior Art) The degree of integration of integrated circuits is accelerating year by year, and now it is the era of so-called VLSI with an integration of 100,000 or more.
We are in the age of designing rules and even 1.0 μm rules. As a result, the demand for photolithographic technology has become stricter year by year. Most of the resists conventionally used in the photolithography technique are negative resists obtained by adding a bisazide compound as a photocrosslinking agent 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 or more.

A positive photoresist can meet the above demands. The positive photoresist composition contains an alkali-soluble resin together with a photosensitive substance, generally a compound containing a substituted naphthoquinonediazide group. Naphthoquinonediazide absorbs ultraviolet rays as shown in the following formula upon irradiation, forms ketene through carbene, reacts with water present in the system to form indenecarboxylic acid, which is dissolved in alkaline water of the developer. is doing.

As described above, since the positive type photoresist uses the alkaline aqueous solution as the developing solution, the resist does not swell unlike the case of the negative type, and accordingly, the resolution can be enhanced.

As described above, the positive type photoresist has generally appeared as a resist characterized by non-swelling and high resolution as compared with the negative type resist, and has been used as a 2 μm rule VLSI.

(Problems to be solved by the invention) However, the design rule of VLSI is 1.5 μm or even 1.0
As the μm rule becomes smaller and finer, the resolution of conventional positive photoresist becomes insufficient, and the reactive ion etching method (hereinafter abbreviated as RIE method) is generally used as an etching method. It has become clear that the heat resistance and RIE resistance of the type photoresist are insufficient, and it has been desired to develop a resist that overcomes the above problems.

(Means for Solving the Problems) The inventors of the present invention have paid particular attention to this point, and as a result of intensive investigations, as a result, in a positive photoresist composition comprising an alkali-soluble resin and a compound containing a 1,2-naphthoquinonediazide compound, It was found that a naphthoquinonediazide group content within a certain range gives a resist having excellent resolution, heat resistance and RIE resistance, and has reached the present invention.

That is, the gist of the present invention is an alkali-soluble resin and 1,2
A positive photoresist composition comprising a compound containing a naphthoquinone azide group, wherein the alkali-soluble resin is a novolak obtained from a mixture of one of the isomers of m-cresol, p-cresol and xylenol and formaldehyde. A resin, wherein the compound containing the 1,2-naphthoquinonediazide group is 1,2-
One of an ester of naphthoquinonediazide-5-sulfonic acid or 1,2-naphthoquinonediazide-4-sulfonic acid and 2,3,4-trihydroxybenzophenone or 2,3,4,4'-tetrahydroxybenzophenone or A positive-type photoresist composition comprising a plurality of types and having a ratio of 1,2-naphthoquinonediazide groups to all solids of 0.7 meq / g or more and 1.5 meq / g or less.

The present invention will be described below. As the alkali-soluble resin of the present invention, a novolak resin obtained from a mixture of m-cresol, p-cresol, and one of xylenol isomers and formaldehyde is used.

Particularly desirably, any one isomer of m-cresol, p-cresol, and xylene, preferably the 2,5-isomer, of the mixture and fluor having a composition falling within the hatched portion of the triangular coordinate shown in FIG. Novolac resin obtained from mualdehyde is used.

These resins can be easily obtained by a known method in which a mixture of a phenol and an aldehyde is condensed with an acid catalyst. The alkali-soluble resin has a weight average molecular weight of 1,000 to 30,00 when the polystyrene-converted value is used to determine the molecular weight using gel permeation chromatography.
0, preferably 1,500 to 20,000, more preferably 2,000
Those in the range of ~ 15,000 are used.

As the compound containing a 1,2-naphthoquinonediazide group,
2,3,4-trihydroxybenzophenone or 2,3,4,4 '
One or more of an ester of tetrahydroxybenzophenone and 1,2-naphthoquinonediazide-5-sulfonic acid or 1,2-naphthoquinonediazide-4-sulfonic acid is used.

2,3,4-trihydroxybenzophenone or 2,3,4,4 '
-If the esterification rate of tetrahydroxybenzophenone is too low, the apparent sensitivity increases, but the residual film rate after development of the unexposed area decreases, so it is desirable to use at 30% or more, preferably 55% or more. .

Such sensitizers include 2,3,4-trihydroxybenzophenone or 2,3,4,4'-tetrahydroxybenzophenone and 1,2-naphthoquinonediazide-5-sulfonic acid, or 1,2-naphthoquinonediazide-4. It can be easily obtained by a known method in which an acid chloride of sulfonic acid is reacted in the presence of a base.

Ratio of a compound containing a 1,2-naphthoquinonediazide group to an alkali-soluble resin, more specifically, 1,2-
The proportion of the naphthoquinonediazide group is extremely important in determining the performance of the resist, and constitutes the essence of the present invention. As an index showing the proportion of 1,2-naphthoquinonediazide groups in the total solids, it is expressed as milliequivalents of 1,2-naphthoquinonediazide groups contained in 1 g of the total solids. Since the quinonediazide group is often represented by the abbreviation Q, it is called Q rate.

The Q factor is closely related to the resist sensitivity, resolution, residual film rate after development of the unexposed area, heat resistance, RIE resistance, etc. Performances other than sensitivity are improved by increasing the Q factor. . In particular, heat resistance and RIE resistance are significantly improved. As a result of intensive studies to obtain the optimum value of the Q rate, the present inventors have found that the range of the Q rate is 0.7 to 1.5 meq / g.

If the Q ratio is less than this, the heat resistance and the RIE resistance are poor, and the resolving power and the residual film rate of the unexposed area after development are not sufficient. When the Q factor is higher than this, the sensitivity becomes extremely low, and the coating property also deteriorates.

Conventionally known positive photoresist compositions composed of an alkali-soluble resin and a compound containing a 1,2-naphthoquinonediazide group are known, for example, Japanese Patent Laid-Open Nos. 52-51931, 58-17112, and 59- 165053, JP-A-60-57339, JP-A-60-164740, and the like. When calculating the Q factor from the disclosed examples, it is 0.52 in JP-A-52-51931. ~ 0.62, 0.43 in JP-A-58-17112
0.58, and in JP-A-59-165053, all are 0.5 or less, such as 0.57 to 0.64.

Usually, these are dissolved in a suitable solvent before use. As a solvent, it has sufficient solubility for the photosensitizer and the resin,
There is no particular limitation as long as it is a solvent that gives good coating properties,
Cellosolve solvents such as methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate and ethyl cellosolve acetate; ester solvents such as butyl acetate and amyl acetate; or highly polar solvents such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone, or Examples thereof include mixed solvents of these, and those to which aromatic hydrocarbon is further added.

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

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, secondary amines such as di-n-propylamine, triethylamine,
Tertiary amines such as methyldimethylamine, quaternary ammonium salts such as tetramethylammonium hydroxide and trimethylhydroxyethylammonium hydroxide, or those obtained by adding alcohols, surfactants or the like can be used.

The positive photoresist composition of the present invention is useful not only for VLSI production 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.
It goes without saying that the present invention is not limited by the embodiments unless the gist thereof is exceeded.

(Synthesis Example 1: Resin A (see Table 1)) A mixture of metacresol 300 mmole, paracresol 200 mmole, and 2,5-xylenol 300 mmole was heated to 100 ° C. with stirring. After the inner temperature is kept constant at about 95 ° C, a solution of 52 ml of 37% formalin aqueous solution and 40 mmole of oxalic acid is added dropwise in 20 minutes. After the dropping, the mixture is reacted at 95 ° C for 6 hours. After completion of the reaction, water and unreacted monomer were distilled off while gradually raising the bath temperature (final liquid temperature 160 ° C, final pressure 20 mmHg). Allow product to cool, 86g
Novolak resin was obtained.

The weight average molecular weight of this novolak resin was measured by gel permeation chromatography and found to be 3480 in terms of polystyrene.

(Synthesis Examples 2 and 3) Resin B and Resin C (see Table 1) were synthesized in the same manner as in Synthesis Example 1.

(Example 1) 3.0 g of novolak resin synthesized in Synthesis Example 1 and 2,3,4,4'-
An esterified product of 1,2-naphthoquinonediazide-5-sulfonic acid of tetrahydroxybenzophenone (esterification rate 75%) 1.37 g (Q factor 1.00 meq / g) was dissolved in ethyl cellosolve acetate 9.5 ml to obtain 0.2 μm. A Teflon filter paper (manufactured by Sumitomo Electric Industries, Ltd.) is used for microfiltration to prepare a photoresist composition.

This photoresist composition was applied onto a 4-inch silicon wafer with a thickness of 1.5 μm using a spin coating device (Hikaru H-2 type manufactured by Mikasa Co., Ltd.), and after prebaking at 90 ° C. for 30 minutes, Reduction projection exposure machine (Canon Corp., FP
A-141 type) and exposed using a mask for resolution test, tetramethylammonium hydroxide 2.38
% Aqueous solution for 1 minute at 25 ° C.

The sensitivity was defined by the relative value of the reciprocal of the exposure energy for reproducing a mask pattern of 2.0 μm, and the residual film rate was expressed as a percentage of the ratio of the film thickness of the unexposed portion before and after development. The resolution is determined by observing the cross section of the resist with a scanning electron microscope (SEM) (× 10,
000) Shown with the smallest line and space that can be resolved.
The heat resistance was evaluated by scanning electron microscopy (SEM) of the cross section of the resist after post-baking at various temperatures (× 10,00).
0) Display the temperature just before the resist flow starts. The results are summarized in Table 1.

(Examples 2 to 5) Solution preparation and evaluation were performed in the same manner as in Example 1. The results are summarized in Table 1.

(Comparative Examples 1 to 3) Preparation and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.
Put together.

Binder resin A: m-cresol / p-cresol / 2,5-xylenol (= 3/2/3) formaldehyde novolak resin Mw3,500 B: m-cresol / p-cresol (= 3/2) Ormaldehyde novolak resin Mw = 12,000 C: m-cresol / p-cresol / 2,5-xylenol (= 1 / 1.8 / 1) formaldehyde novolak resin, Mw
= 4180 D: m-cresol / p-cresol / 2,5-xylenol (= 3/4/3) formaldehyde novolak resin E: m-cresol / p-cresol / 2,5-xylenol (= 4 / 3/3) Formaldehyde novolak resin Photosensitizer X: 1,2- of 2,3,4,4'-tetrahydroxybenzophenone
Naphthoquinone diazide-5-sulfonic acid ester. Esterification rate 75% Y: 1,2-naphthoquinonediazide-5-sulfonic acid ester of 2,3,4-trihydroxybenzophenone. Esterification rate 98% Z: 1,2-naphthoquinonediazide-5-sulfonate of quercetin. Esterification rate 100% (Effect of the invention) According to the composition of the present invention, a photoresist excellent in various characteristics such as resolution and heat resistance can be obtained, which can be very suitably used for development of VLSI and the like. .

[Brief description of drawings]

FIG. 1 is a triangular coordinate showing a suitable mixing ratio of m-cresol, p-cresol and xylenol suitable for obtaining the novolak resin used in the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Kameyama 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryoh Chemical Industry Co., Ltd. (72) Inventor Chie Tanaka 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa (56) Reference JP-A-60-158440 (JP, A) JP-A-60-164740 (JP, A) JP-A-60-57339 (JP, A)

Claims (3)

[Claims] 1. A positive photoresist composition comprising an alkali-soluble resin and a compound containing a 1,2-naphthoquinonediazide group, wherein the alkali-soluble resin is an isomer of m-cresol, p-cresol and xylenol. A novolak resin obtained from a mixture of one and formaldehyde, wherein the compound containing the 1,2-naphthoquinonediazide group is 2,3,4.
-One or more kinds of esters of trihydroxybenzophenone or 2,3,4,4'-tetrahydroxybenzophenone and 1,2-naphthoquinonediazide-5-sulfonic acid or 1,2-naphthoquinonediazide-4-sulfonic acid The positive photoresist composition is characterized in that the ratio of 1,2-naphthoquinonediazide groups to the total solid is 0.7 meq / g or more and 1.5 meq / g or less. 2. The alcal-soluble resin is m-cresol,
A novolak resin obtained from formaldehyde with a mixture of p-cresol and any isomer of any one of the xylenols having a composition corresponding to the hatched portion of the triangular coordinate shown in the first figure. The positive photoresist composition according to the first item. 3. The esterification rate of the compound containing the 1,2-naphthoquinonediazide group (esterification rate is defined as the percentage of esterified hydroxy groups relative to all hydroxy groups) is 55% or more. The positive photoresist composition according to claim 1, characterized in that