KR920005780B1 - Thermally stable photoresist composition - Google Patents

Abstract

The photoresist compsn. comprises (a) 10-70 wt.% of photoactivating component, (b) 30-90 wt.% of binder resin and condsn. polymer of formaldehyde and phenolic monomer of formula (I), (II) or (III), and (c) a mixed solvent of ethyl lactate/propylene slycol monomethyl ether acetate/diethylene glycol dimethyl ether. In (III), R1 is H, OH or sulfonic acid; R2 is H, OH, sulfonic acid or nitro. The compsn. is used for forming a positive image in the photolithography process, and has a good image force and contrast.

Description

Photoresist composition with excellent heat resistance

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive resin composition which is applied to a photolithography process to form a positive image when manufacturing a highly integrated semiconductor circuit, and maintains excellent properties of resolution and contrast as compared to the conventional one, and relates to a photosensitive resin composition having excellent heat resistance.

In general, the photosensitive resin composition is composed of a photoactive component, a binder resin, various additives, and solvents that provide suitable viscosity and coating properties by dissolving good compatibility. Most of the commercially available positive type photoresist is a mixture of a photoactive component that is insoluble in an aqueous alkaline solution and a phenolic or cresol-based novolak resin dissolved in an aqueous alkaline solution. Examples are USP 3,402,044, USP 3,759,711, USP 3,890,152, USP 4,007,047, USP 4,104,070, USP 3,827,908, USP 4,115,128, USP 4,196,003, USP 4,356,254, USP 4,356,255, GB 1,494,640.

As a photoactive component for producing a positive image, a quinone azide compound that is decomposed into a 5-ring carboxylic acid and dissolved in an aqueous alkali solution is often used when irradiated with strong light (ultraviolet rays, etc.). Therefore, the photosensitive resin composition containing a quinone azide type compound is applied to various fields which require a positive-positive image, such as an adhesion film for printing plates, a printing plate for flat plate printing, and a photoresist for semiconductor microcircuit processing.

In recent years, the semiconductor industry demands high integration and high productivity of circuits. Therefore, even for photoresist, which is essential for the processing thereof, the submicron resolution and line width control characteristics are excellent, and the demand for durability for dry etching is increased. There is an urgent need for the development of photoresists with thermal stability in the 150 ° C-200 ° C range.

The above-mentioned patents mostly relate to a method of preparing a photoresist composition using cresol-based novolak resins. In the case of photoresists using cresol-based novolak resins, the resin has a glass transition temperature, a structure, a monomer ratio, and a resist solvent. Regardless, it exhibits almost the same heat resistance characteristics, and at a temperature of 150 ° C. or more, a phenomenon of pattern profile flow occurs, which is insufficient for high productivity in the semiconductor industry.

The recent research and development direction to improve the thermal stability is to change the binder resin constituent of the porter resist related to the use of novolak resin copolymerized with methacresol and para cresol, hexafluoropropane combined Hydroxy polaramide, hydroxy polyimide, poly parahydroxy styrene, polyhydroxy alpha spirene and the like have been studied, but have a disadvantage in that resolution is reduced while heat resistance is increased.

In the present invention, by modifying the structure and composition of the binder resin as a constituent of the photoresist, a photoresist having thermal stability in the range of 150-200 ° C. and having good resolution is modified.

The binder resin used in the present invention is a photoresist made of a polymer consisting of a condensation reaction of a phenol-based monomer having the following structural formulas (I), (II) and (III) with formaldehyde, compared with conventional photoresists. And excellent thermal stability in the range of 150-200 ° C. without degrading the excellent properties of the contrast.

R ₁ is a group selected from a hydrogen atom, a hydroxy group and a sulfonic acid group, and R ₂ represents a group selected from a hydrogen atom, a hydroxy group, a sulfonic acid and a nitiro group.

Examples of structural formula (I) are metacresol and paracresol, structural formula (II) is 2, 6-bis (hydroxy methyl) -4-methylphenol, and examples of structural formula (III) are 1-naphthol, 1-naphthol -4, 8-disulfonic acid, 2-naphthol-3, 6-disulfonic acid, 2-naphthol-6, 8-disulfonic acid, 1-naphthol-2-sulphonic acid, 1-naphthol-4-sulphonic acid , 2-naphthol-6-sulphonic acid, 2-nitro-1-naphthol, 2, 3-dinitro-1-naphthol and the like.

Representative synthetic methods of these binder resins are as follows. Formaldehyde is added at a molar ratio of 0.6 to 0.95 per 1 mole of phenolic monomer and refluxed at 100 ° C. for 12 hours to 24 hours. Oxalic acid, organic acid, hydrochloric acid, etc. may be used as the catalyst used at this time, and oxalic acid is most commonly used. The amount of catalyst is preferably 0.3 to 7% by weight relative to the total amount of phenolic monomers, and more preferably 1 to 3 by weight.

In this way, after the reflux, most of the water is removed from the normal pressure and distilled under reduced pressure to 225 ° C at a pressure of 30-50mmHg to remove the residual water. The temperature is then raised to 230 ° C. and distilled under reduced pressure under vacuum to remove unreacted monomers. The reaction is discharged under nitrogen atmosphere and cooled to room temperature. Table 1 summarizes the synthesis conditions for each resin.

The composition of the phenolic monomers used in the synthesis of the binder resin used in the present invention is 0 to 60 molar ratios of (Formula I), 20 to 40 molar ratios of (Formula II), and (Formula III) to all the phenolic monomers. It is good to synthesize | combine this at 20-40 molar ratio. The weight average molecular weight is preferably 15,000 to 25,000.

The composition of the photoresist of the present invention is ester substitution reaction of 1 mole of 2,3,4-trihydroxy benzophenone with respect to 2.5 moles of naphthoquinone- (1,2) -diazide-5-sulfonyl chloride as a photoactive component. Photoactive components were used, and the content of the photoactive components in the photoresist composition is 10 to 70 parts by weight, and more preferably 20 to 45 parts by weight, based on the total solids.

In addition, the content of the binder resin in the photoresist composition of the present invention is preferably 30 to 90 parts by weight, more preferably 55 to 80 parts by weight based on the total solids.

Solvents that can be used in the preparation of the photosensitive resin composition using the photoactive components and the binder resin mentioned above include methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve, ethyl cellosolve acetate, and butyl cellosolve. Solvents such as butyl cellosolve acetate, dimethyl formamide, dimethyl sulfoxide, dioxane, acetone, cyclohexanone, trichloroethylon, methyl ethyl ketone, normal butyl acetate, and xylene can be used alone or in combination. .

The solvent used in the present invention was a mixed solvent consisting of 80 parts by weight of ethyl lactate, 10 parts by weight of propylene glycol monomethyl ether acetate, and 10 parts by weight of diethylene glycol dimethyl ether.

Thus far, the photoresist composition was prepared using the binder resin, the photoactive component, and the mixed solvent, and thus the heat resistance from 150 ° C to 200 ° C without deteriorating the excellent properties such as sensitivity, developability, resolution contrast, and etching resistance. Excellent results were obtained.

TABLE 1

Example 1

187.5 g of the binder resin of 62.5 g of the ester compound of naphthoquinone- (1, 2) -diazide-5-sulfonyl chloride with 2, 3, 4-trihydroxybenzophenone (synthesis example 1) were mentioned above. Completely dissolved in 750g of mixed solvent and filtered to the final 0.2㎛. This photoresist is spin-coated to a silicon wafer treated with E.M.D.S so as to have a thickness of 1.22 mu m after soft baking. The soft bake is 80 seconds at 105 ° C. on a heated hotplate. The coated wafer is exposed to 65 zones with increasing energy in 5 msec from 80 msec to 400 msec with Nikon Stepper NSR-1505 G4D. The exposed wafer is developed in a trimethylammonium hydroxide 2.38% developer in a puddle at 25 ° C. for 60 seconds.

After baking the developed wafer at 115 ° C for 90 seconds, the resolution of the pattern was observed in the zone exposed to 1.8 times the energy (threshold energy, ET) of full development using Hitachi S-800 electron microscope. It has a resolution of / S. In addition, the wafer was baked in an oven for 30 minutes at an interval of 10 ° C. from 120 ° C. to 200 ° C., and then observed under an electron microscope, showing excellent thermal properties without a flow phenomenon of the pattern profile up to 160 ° C.

Example 2

Compared with Example 1, the same as in Example 1 except that 187.5 g of the binder resin of Synthesis Example 2 was added instead of the binder resin of Synthesis Example 1. As a result, the resolution was 0.8㎛ L / S, the heat resistance was excellent at 150 ℃.

Example 3

Compared with Example 1, the same as in Example 1 except that 187.5 g of the binder resin of Synthesis Example 3 was added instead of the binder resin of Synthesis Example 1. As a result, the resolution was 075㎛ L / S, and the heat resistance was excellent at 180 ° C.

Comparative Example 1

Compared with Example 1, the same as in Example 1 except that 187.5 g of 100% novolak resin having a molecular weight of 25.000 was substituted for the binder resin of Synthesis Example 1. As a result, the resolution was 0.8μmL / S, the heat resistance was 130 ℃.

Example 4

It is the same as that of [Example 1] except having added 187.5g of binder resins of (Synthesis example 4) instead of the binder resin of (Synthesis example 1) compared with [Example 1]. As a result, the resolution was 0.8㎛ L / S, the heat resistance was 200 ℃.

Example 5

It is the same as that of [Example 1] except having added 187.5g of binder resins of (Synthesis example 5) instead of the binder resin of (Synthesis example 1) compared with [Example 1]. As a result, the resolution was 0.65㎛ L / S and the heat resistance was excellent at 170 ℃.

Claims (2)

A photosensitive resin composition comprising a photoactive component, a binder resin and a solvent, wherein the photosensitive resin composition is 10-70 wt%, more preferably 20-45 wt%, based on at least the total solids that can be exposed to ultraviolet light and developed in an aqueous alkali solution to form a positive image. Condensation polymer of phenol-based monomers and formaldehyde of the following compounds (I), (II) and (III), which occupies 30-90% by weight, more preferably 55-80% by weight of the total solids And a binder resin, and an ethyl lactate / propylene glycol monomethyl ether acetate / diethylene glycol dimethyl ether mixed solvent.

In the above, R ₁ is selected from a hydrogen atom, a hydroxyl group, a sulfonic acid group, R ₂ is selected from a hydrogen atom, a hydroxyl group, a sulfonic acid group, a nitro group. According to claim 1, wherein the composition of the phenolic monomer to be added during the synthesis of the binder resin is 0-60 molar ratio of the compound (I), 20-40 molar ratio of the compound (II), 20- mole ratio of the compound (III) A photosensitive resin composition having excellent heat resistance, characterized in that 40 mole ratio, formaldehyde is 0.6-0.95 molar ratio with respect to 1 mole of the entire phenolic monomer, and the weight average molecular weight of the binder resin is 15,000-25,000.