JPH0247656A - Positive type photoresist - Google Patents

Abstract

PURPOSE:To improve definition and heat resistance while maintaining sensitivity and process stability by using an alkaline soluble novolak resin contg. a specific co-condensation polymer. CONSTITUTION:The alkaline soluble resin of the positive type photoresist consisting of the alkaline soluble resin and 1,2-quinonediazide photosensitive agent is formed of the novolak resin constituted of the phenol/xylenol co- condensation polymer expressed by the formula I. Pattern formation is executed by using the positive type photoresist. In the formula I, m and n denote positive integer; m/n is 99.9/0.1-0.1/99.9. The sensitivity, definition, heat resistance, and the process stability are improved in this way.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides an alkali-soluble novolac resin and a 1°2- The present invention relates to a positive photoresist made of a quinonediazide compound and a pattern forming method.

[Prior Art] In recent years, the density and integration of semiconductor integrated circuits have progressed, and we have entered an era where the degree of integration is 4 Mbits or more, and pattern formation of submicron rules or even smaller ones has become necessary.

The positive photoresist consists of an alkali-soluble novolak resin and a 1°2-quinonediazide compound that functions as an alkali dissolution inhibitor.

In the radiation irradiated part, the 1,2-quinonediazide compound becomes ketene via carbene, reacts with moisture inside and outside the system to produce indene carboxylic acid, and becomes easily dissolved in the alkaline aqueous solution. On the other hand, the unirradiated area is dissolved in an alkaline developer, exhibits almost no swelling, and maintains a high residual film rate. As a result, a high resolution resist pattern is obtained. Conventional cyclized polyisoprene-based negative resists have limited resolution due to swelling of the film during development.
Recently, positive resists have been mainly used.

By the way, in order to meet increasingly stringent requirements, repeated attempts have been made to improve positive photoresists, and a wide range of detailed studies have been carried out on everything from resins, photosensitizers, developers, and additives. There is.

In particular, high sensitivity, high resolution, rectangularity of pattern profile, high dry etching resistance, high heat resistance, and process stability are strongly desired and are the goals of improvement.

For example, regarding resin, JP-A-58-17112. Japanese Patent Publication Showa (i2-35348. Japanese Patent Publication Showa (i2-130G37
discloses that high sensitivity and high resolution can be achieved by limiting the composition ratio of 〇-/m-/p-cresol. Also, JP-A-60-1584
40. JP-A-Sho GO-11115741. JP-A-81-2
75748. In JP-A-82-138837, m
-/p-cresol/xylenol is disclosed.

[Problems to be Solved by the Invention] Generally, sensitivity and resolution, sensitivity and heat resistance, and sensitivity, resolution, heat resistance, and process stability tend to contradict each other. For example, increasing the molecular weight of the resin increases heat resistance, but reduces sensitivity, resolution, pattern profile rectangularity, and process stability. If copolymerization is performed to improve heat resistance, the rectangularity of the pattern profile and process stability will decrease. Furthermore, when the amount of photosensitizer is increased, the resolution improves, but the sensitivity decreases. As described above, since there are many contradictory properties, it has been extremely difficult to achieve high performance without degrading other properties.

In addition, the above-mentioned o −/m −/p-cresol, m
-/ p-Cresol/xylenol resin exhibits good properties, but since the reaction rates of each monomer are greatly different, it is difficult to obtain a random copolymer and quality control is difficult.

However, if a random copolymer is synthesized, it becomes possible to form a homogeneous film on the micro-order compared to a block copolymer. It is expected that the characteristics will further improve.

[Means for Solving the Problem] As a result of extensive research based on the above background, the present inventors have developed an alkali-soluble novolac resin containing a cocondensation polymer represented by the following general formula (I). The present inventors have discovered that resolution, pattern profile, and heat resistance can be improved while maintaining sensitivity and process stability by using a stepper, and have completed the present invention.

That is, the present invention provides a positive photoresist comprising an alkali-soluble resin and a 1,2-quinonediazide-based photosensitizer, in which the alkali-soluble resin substantially has the general formula (1), (where m and n are positive differences). Indicates the number, m/n is 99
．． It is 910.1 to 0.1/99.9. The present invention provides an all-positive type photoresist characterized by being made of a novolac resin composed of a phenol/xylenol cocondensation polymer represented by the following formula, and a pattern forming method using this positive type photoresist.

In the positive photoresist of the present invention, the xylenol component of the phenol/xylenol cocondensation polymer is
The properties are particularly good when derived from 3,4-xylenol.

The alkali-soluble novolac resin of the present invention can be produced by a known method by mixing phenol, xylenol and aldehydes such as formaldehyde, paraformaldehyde, and acetaldehyde in the presence of an acidic catalyst such as formic acid, oxalic acid, acetic acid, hydrochloric acid, nitric acid, sulfuric acid, and Lewis acid. It can be synthesized by polycondensation according to the following. The weight average molecular weight of the resin is 2000 to 3000
0 (polystyrene equivalent) is preferred. Within this range, sensitivity, resolution, heat resistance, and process stability are excellent.

Furthermore, if necessary, some of the hydroxyl groups may be substituted with sulfonic acid or carboxylic acid ester.

Examples of the esterification component include alkyl groups such as methyl, ethyl, and propyl, and aromatic rings such as phenyl, tolyl, benzoic acid, naphthyl, benzyl, cumyl, and phenethyl.

The 1,2-quinonediazide compound used in the present invention is, for example, 1,2-naphthoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-5
- It is a sulfonic acid ester, and the ester component is:
Polyhydroxybenzophenones such as trihydroxybenzophenone, tetrahydroxybenzophenone, and hexahydroxybenzophenone, gallic acid esters such as methyl gallate, ethyl gallate, and phenyl gallate, flavones such as quercetin, trihydroxybenzene, and trihydroxyphenyl-n- Examples include polyhydroxyphenylalkyl ketones such as xylketone, dihydroxydiphenylmethane, dihydroxydiphenylpropane, dihydroxydiphenylhexafluoropropane, dihydroxydiphenylsulfone, and dihydroxydiphenylamine. The 1,2-quinonediazide compound is preferably used in an amount of 20 to 50 parts by weight based on 100 parts by weight of the alkali-soluble novolac resin. Within this range, a sufficient difference in solubility in the developer between exposed and unexposed areas can be obtained, and a pattern with excellent sensitivity and resolution can be obtained.

The positive photoresist of the present invention is obtained by dissolving the alkali-soluble novolac resin and the 1,2-quinonediazide compound in a suitable solvent such that the solid content is 20 to 40 parts by weight. Examples of the solvent include ethylene glycol monoalkyl ether and its acetates, propylene glycol monoalkyl ether and its acetates, diethylene glycol dialkyl ether,
Ketones such as methyl ethyl ketone and cyclohexanone,
Examples include acetic acid esters such as ethyl acetate and butyl acetate, aromatic hydrocarbons such as toluene and xylene, dimethylacetamide, and dimethylformamide. These solvents can be used alone or in combination of two or more. Furthermore, if necessary, a nonionic, fluorine-based, silicone-based surfactant, etc. can be added to improve coating properties. In addition, sensitizers, colorants, stabilizers, etc.
Compatible additives can be blended.

[Function] The positive photoresist comprising the alkali-soluble novolak resin and 1°2-quinonediazide compound of the present invention has the following properties:
It can be used to form resist patterns using ultraviolet rays, deep ultraviolet rays, electron beams, X-rays, etc., and has excellent sensitivity, resolution, heat resistance, and C process stability.

There are no particular limitations on the method of using the positive photoresist comprising the alkali-soluble novolak resin and 1°2-quinonediazide compound of the present invention to form a resist pattern by radiation, and the method can be carried out according to a conventional method.

For example, the positive photoresist solution of the present invention is prepared by dissolving an alkali-soluble novolak resin, a 1,2-quinonediazide compound, and additives in a solvent, and filtering the solution through a 0.2 μm filter. A resist film is obtained by spin-coding a resist solution onto a substrate such as a silicon wafer and bre-baking. Thereafter, a resist pattern can be formed by performing exposure using a reduction projection exposure device, an electron beam exposure device, or the like, and developing.

Examples of liquids include: tetramethylammonium hydroxide, quaternary ammonium salts such as choline, organic alkali aqueous solutions such as amines, or inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, aqueous ammonia, etc. Aqueous solutions can be used. Other methods such as coating, blebake, exposure, development, etc. can be carried out by conventional methods.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Synthesis Example 1 150 g of phenol, 98 g of 3.4-xylenol, 4.0 g of monooxalic acid dihydrate, 175 g of 37% formalin, and 1-200 g of ethylene glycol monoethyl ether acetate were added to a 1000 ml four-tube separable flask. Without stirring, the mixture was immersed in an oil bath and the internal temperature was raised to 100°C to start the reaction. After 10 hours of reaction, 100 d of water was added and the temperature was increased to 180°C under 2 gmmHg.
The temperature was gradually raised to . Under these conditions, dehydration, solvent removal, and monomer removal were performed for 3 hours, followed by cooling, and methanol was added. Thereafter, dissolution and precipitation of the resin were repeated in a methanol/water system, followed by drying to obtain 221 g of resin powder.

The weight average molecular weight of novolac resin is G P Cell
As a result, it was 3850 in terms of polystyrene. In addition, the dispersity (1m average molecular weight/number average molecular weight) is 4.3
It was 2.

In addition, when the reaction was followed after 10 hours by gas chromatography, the reaction rate was 92% for phenol and 85% for 3.4-xylenol, judging from the remaining monomers.
Met.

Synthesis Example 2 169 g of phenol, 77 g of 3.4-xylenol, 5.3 g of monooxalic acid dihydrate, 190 g of 37% formalin, and 200 g of ethylene glycol monoethyl ether acetate were added to a 1000 Id 4-tube separable flask. Without stirring, the mixture was immersed in an oil bath and the internal temperature was raised to 100°C to start the reaction. After 10 hours of reaction, water was added to 1
001d was added, and the temperature was gradually raised to 180° C. under 2 gmmHg. Under these conditions, dehydration, solvent removal, and monomer removal were performed for 3 hours, followed by cooling, and methanol was added. After that, the resin is dissolved in a methanol/water system.
The precipitation was repeated and drying was performed to obtain 235 g of resin powder.

The weight average molecular weight of the novolak resin is G P C1l1
The constant result was 6530 in terms of polystyrene.

Further, the degree of dispersion (weight average molecular ffi/number average molecular weight) was 4.55.

In addition, when the reaction was followed after 10 hours by gas chromatography, the reaction rate was 95% for phenol and 88% for 3.4-xylenol, judging from the remaining monomers.
Met.

Synthesis Example 3 Phenol 1 was placed in a 1000-liter separable flask.
69 g, 2.5-xylenol 77 g 1 oxalic acid dihydrate 5
．． 3 g, 190 g of 37% formalin and 200 g of ethylene glycol monoethyl ether acetate were added. Without stirring, the mixture was immersed in an oil bath and the internal temperature was raised to 100°C to start the reaction. After 10 hours of reaction, add 10 hours of water
0- was added and the temperature was gradually raised to 180° C. under 2 gmmHg. Under these conditions, dehydration, desolvation,
After demonomerization, cooling was performed and methanol was added. Thereafter, dissolution and precipitation of the resin were repeated in a methanol/water system, followed by drying to obtain 228 g of resin powder.

The weight average molecular weight of the novolac resin was 7200 in terms of polystyrene as a result of GPC-11. Also,
Dispersity (weight average molecular weight/number average molecular weight) is 4.8.5
Met.

In addition, when the reaction was followed after 10 hours by gas chromatography, the reaction rate was 93% for phenol and 76% for 3.4-xylenol, judging from the remaining monomers.
Met.

Example 1 8 g of phenol/3,4-xylenol novolac resin obtained in Synthesis Example 1, 2,3,4.4''-tetrahydroxybenzophenone and 1,2-naphthoquinonediazide-5-
Dissolve 2.24 g of esterified product with sulfonyl chloride (3.5 hydroxyl groups are esterified on average) in 24 g of ethylene glycol monoethyl ether acetate,
．． Filtration was performed using a 2 μm membrane filter to obtain a resist solution. Using a spinner, apply the resist solution to 4
Spin coating onto inch silicon wafer, 90℃, 30℃
Brebake was performed in a circulating constant temperature bath for minutes to obtain a resist film with a thickness of 1.5 μm. Next, a reduction projection exposure device (manufactured by GCA, DSW-6300A).

N, A, -0,35) through the reticle. As a developer, a 2.38 tffi% aqueous solution of tetramethylammonium hydroxide was used at 25°C for 1
Immersion development was performed for a minute.

The exposure dose for one-to-one resolution of 1.0 μm lines/spaces was 285 mJ/cm2.

Also, even in 0.8μm line/space, 290
A one-to-one pattern could be resolved with mJ/cm2, and the mask fidelity was good.

Regarding the resolution, a 0.65 μm line/space could be resolved, and the pattern was rectangular.

Next, resist patterns with 2 μm lines/spaces of 130, 135, 140, 145°150.15
5. Baking was performed at each temperature of 160° C. for 30 minutes in a circulating constant temperature bath, and heat resistance was evaluated based on 9 no deformation of the pattern. As a result, the heat resistance was 150°C.

Example 2 The resin obtained in Synthesis Example 2 was subjected to an exposure test and a heat resistance test according to Example 1.

'c' Result, 1.0μm line/space 1:1
The exposure amount for resolution was 256 mJ/cm2.

Also, even in 0.8μm line/space, 256
A one-to-one pattern could be resolved with mJ/cm2, and the mask fidelity was good.

Regarding the resolution, a 0.65 μm line/space could be resolved, and the pattern was rectangular.

Heat resistance was 150°C.

Example 3 The resin obtained in Synthesis Example 3 was subjected to an exposure test and a heat resistance test according to Example 1.

As a result, the exposure dose for resolving 1.0 μm line/space one-to-one was 310 mJ/cm2.

Regarding the resolution, a 0.70 μm line/space could be resolved, and the pattern was rectangular.

Heat resistance was 150°C.

[Effects of the Invention] The positive photoresist comprising the alkali-soluble novolak resin and the 1°2-quinonediazide compound of the present invention has the following properties:
Consists of phenol/xylenol copolycondensed alkali-soluble novolak resin. In particular, phenol/3,4-xylenol provides a resist with excellent sensitivity, resolution, pattern shape, and process stability, and is therefore suitable for manufacturing semiconductor integrated circuit elements such as VLSIs.

Claims (3)

[Claims] (1) In a positive photoresist consisting of an alkali-soluble resin and a 1,2-quinonediazide-based photosensitizer, the alkali-soluble resin substantially has a general formula, ▲mathematical formula, chemical formula, table, etc.▼ (in the formula, m and n indicates a positive integer, m/n is 99.9
/0.1 to 0.1/99.9. ) A positive photoresist characterized by being made of a novolak resin composed of a phenol/xylenol cocondensation polymer represented by: (2) The positive photoresist according to claim 1, wherein the xylenol component of the phenol/xylenol cocondensation polymer is derived from 3,4-xylenol. (3) A pattern forming method using the positive photoresist according to claim 1.