JPH10221846A - Production of sensitizer and positive photoresist composition containing the sensitizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a sensitizer having high sensitivity and a large difference between alkali solution velocity before exposure and that after exposure by adding a specified amt. of 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride to specified methylentetra-p-cresol and bringing them into esterification reaction under specified conditions. SOLUTION: 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride is added by 2.5-4.5mol to 1mol methylenetetra-p-cresol represented by the formula and they are brought into esterification reaction in dimethylactamide as a solvent in the presence of triethylenediamine. The resultant soln. is poured into an aq. hydrochloric acid soln. and a formed precipitate is separated by filtration, washed and dried to obtain the objective sensitizer having a high concn. of high sensitivity diester and not contg. 1,2-naphthoquinone-2-diazido-5-sulfonic acid as an impurity which reduces action to inhibit the dissolution of an alkalisoluble resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive photoresist composition having a high-resolution resist performance, and which can be effectively used for an i-line exposure method, and more particularly to a method for producing a photosensitive agent therefor.

[0002]

2. Description of the Related Art Exposure apparatuses and photoresists used in semiconductor lithography have advanced rapidly, exceeding the design rule of 0.5 μm by the i-line exposure method to 0.35 μm.
Furthermore, 64MD according to the 0.30 μm design rule
RAM is being produced and efforts are being made to pursue finer linewidths.

[0003] The photoresist composition used here is a positive photoresist composition in which a photosensitive agent is mainly blended with an alkali-soluble resin, especially a novolak resin. As this photosensitizer, 1,2 naphthoquinone-2-diazido-5-sulfonic acid ester compound is usually used.

[0004] This compound itself acts as a dissolution inhibitor for reducing the alkali solubility of the novolak resin, but decomposes upon irradiation with light (exposure) to form an indene carboxylic acid which is an alkali-soluble substance, which is a novolak resin. Is an ideal compound that promotes alkali dissolution of the compound and increases the difference in alkali dissolution rate before and after exposure. The action of this photosensitizer is mainly due to the action of the 1,2 naphthoquinone-2-diazide-5-sulfonic acid group, and in particular, the selection of a ballast molecule is extremely important to sufficiently exert this action.

Therefore, the development of a photosensitizer which has a higher compatibility with a resist solvent and a greater inhibitory action on alkali dissolution in a novolak resin than the conventional one, and conversely promotes the alkali solubility greatly after irradiation with light has been promoted. ing.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made in view of the above-mentioned circumstances. It is an object of the present invention to provide a method for producing a photosensitive agent having a large difference and a high-resolution positive photoresist composition containing the same.

[0007]

Means for Solving the Problems To solve such problems, the invention described in claim 1 of the present invention has the following general formula I:

Embedded image 1,2 naphthoquinone-2-diazido-5-sulfonyl chloride is added at a ratio of 2.5 mol or more and 4.5 mol or less to 1 mol of methylenetetra-p-cresol represented by the following formula, and dimethylacetamide is added to the solvent. After an esterification reaction in the presence of triethylenediamine, the reaction solution was poured into an aqueous hydrochloric acid solution, and the resulting precipitate was separated by filtration.
A method for producing a photosensitive agent, comprising washing with water and drying.

According to such a production method, 1,2-naphthoquinone-2-diazide-5-sulfonic acid as an impurity which has a high concentration of a highly sensitive diester compound and lowers the dissolution inhibiting action of an alkali-soluble resin is completely contained. It is possible to obtain an unsensitized photosensitive agent.

In the invention of claim 2 of the present invention, 1,2 naphthoquinone-2-diazide-5-sulfonyl chloride is used in an amount of at least 2.5 moles per mole of methylenetetra-p-cresol. A positive photoresist composition comprising a photosensitizer and an alkali-soluble resin obtained by an esterification reaction in the presence of triethylenediamine using dimethylacetamide as a solvent in a proportion of 5 mol or less. . In this case, it is preferable that the alkali-soluble resin is a cresol-novolak resin (claim 3).

When the positive photoresist composition is constituted as described above, a positive photoresist composition having high sensitivity, high resolution, and excellent resist performance such as alkali solubility can be obtained.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto. The positive photoresist composition of the present invention contains the photosensitive agent and the alkali-soluble resin produced by the production method of the present invention as main components. First, the method for producing the photosensitive agent according to the present invention will be described.

The composition of the photosensitizer of the present invention is represented by the following general formula I: methylenetetra-p-cresol {2,2 ′
-Methylenebis [6-[(2-hydroxy-5-methylphenyl) methyl] -4-methylphenol]};
An ester compound obtained by reacting with 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride, which is a mixture of a diester, a triester, and a trace amount of a tetraester.

This method for producing a photosensitizer uses dimethylacetamide as a solvent, and 1,2 moles per mole of methylenetetra-p-cresol (hereinafter abbreviated as MTPC).
-Naphthoquinone-2-diazide-5-sulfonyl chloride (hereinafter abbreviated as NQASC) in the presence of triethylenediamine at a ratio of 2.5 mol or more and 4.5 mol or less to form an ester, and the reaction solution is treated with aqueous hydrochloric acid. And the resulting precipitated product is filtered off, washed with water and dried.

In general, when synthesizing a photosensitive agent, MTPC
Even when NQASC is reacted in a large excess of 4 times or more, a triester is hardly formed, a tetraester is hardly formed, and a diester is obtained as a main component. In the present invention, the concentration of the diester is about 60
%, So the upper limit is 4.5
When the molar ratio exceeds 4.5, the concentration and the resist performance are saturated, which is economically disadvantageous.

In a further excess, NQASC generates 1,2-naphthoquinone-2-diazide-5-sulfonic acid (hereinafter abbreviated as NQASA) during the treatment of the reaction product, and this is produced in large amounts as an impurity. It is contained in the photosensitive agent. NQASA as this impurity reduces the dissolution inhibiting action of the alkali-soluble resin of the photosensitive agent,
It has been found that the performance of the resist composition deteriorates.
Conversely, if the molar ratio is less than 2.5 times, the concentration of the diester decreases, and the resist performance also decreases.

Next, selection of the reaction solvent is also an important requirement. Conventionally, often used solvents such as dioxane and acetone, and triethylamine known as amines,
With a combination of tributylamine, pyridine, diazabicyclooctane and the like, it is difficult to suppress the generation of NQASA contained as an impurity in the photosensitive agent.

However, only in the case of a combination of a dimethylacetamide solvent and triethylenediamine [1,4-diazabicyclo (2,2,2) octane],
Surprisingly, they have found that NQASA is not contained in the photosensitive agent at all, and it has been found that they exhibit high resist performance. Thus, they have reached the present invention. The amount of this triethylenediamine used is sufficient to be equimolar to NQASC.

Next, the positive photoresist composition will be described. The positive photoresist composition of the present invention,
It is a mixture of an alkali-soluble resin and a photosensitive agent produced by the production method of the present invention.

As the alkali-soluble resin, for example, novolak resin, styrene-maleic anhydride copolymer, polyvinylhydroxybenzoate, polyhydroxystyrene, carboxyl group-containing acrylic resin and the like can be used. In particular, cresol-novolak resin is used. It is suitable.

The cresol novolak resin has a weight-average molecular weight (Mw, GPC, in terms of polystyrene) of 1,000 to 20,000, especially 3,000.
Those having 0 to 10,000 are preferred. Molecular weight 1,0
If it is less than 00, the heat resistance may decrease, and 2
If it exceeds 000, the heat resistance will be improved, but the alkali solubility will decrease as the molecular weight increases, and the resolution may deteriorate.

The amount of the photosensitive agent is 10 to 50 parts by weight, especially 20 parts by weight, per 100 parts by weight of the alkali-soluble resin.
~ 40 parts by weight are preferred. If the amount is less than 10 parts by weight, the ability to reduce the alkali dissolution rate of the resin may not be exhibited, or the alkali dissolution rate after photolysis by exposure may not be sufficiently increased, and the performance as a resist may not be sufficiently exhibited. If the amount exceeds the above range, the resist performance may decrease as the exposure amount increases (sensitivity decreases). This is considered to be caused by incomplete dissolution inhibition by exposure or by reaction with the resin due to photolysis.

The method of using the positive photoresist composition of the present invention is to dissolve it in a solvent, apply it on a semiconductor substrate, bake it (pre-bake), and after exposure, develop with alkali to form a pattern. . As the solvent used here, for example, ethyl cellosolve acetate,
Cellosolve esters such as methyl cellosolve acetate; glycol ethers such as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether; ethers such as 1,2-diethoxyethane and 1,2-dibutoxyethane; ethyl lactate; diethyl malonate; And ketones such as cyclopentanone and cyclohexanone. The compounding amount of the solvent is adjusted according to the required resist film thickness, but it is generally a solution having a concentration of 50 to 90% by weight.

In preparing this solution, it is desirable to add a surfactant to improve the coatability and striation of the positive photoresist composition, and to add polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; Nonionic surfactants such as polyoxyethylene alkyl phenyl ethers such as ethylene nonyl phenyl ether; Florad FC-430, F
Fluorinated surfactants such as C-431 (trade name, manufactured by Sumitomo 3M Limited) are exemplified. The amount of the surfactant is preferably 0.01 to 0.1% by weight based on the solution.

Further, a sensitizer, a storage stabilizer, a light absorbing agent, an adhesion aid and the like can be added as optional components to the composition.

The method for applying the positive photoresist composition of the present invention to a semiconductor substrate is usually carried out by using a spin coater at a rotational speed of 2000 to 5000 rpm.
It is prepared so as to have a thickness of about 5 to 5 μm, but a spray coat, a knife coat and the like are also used.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these.

[0027]

【Example】

(Example 1) [Synthesis of photosensitizer] In a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, methylenetetra-p-cresol (M
TPC) 6 g (0.0128 mol), 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride (N
QASC) 10.3 g (0.0384 mol) of 60 g
Was dissolved in dimethylacetamide, and a solution of 4.3 g (0.0384 mol) of triethylenediamine dissolved in 20 g of dimethylacetamide was gradually added dropwise, followed by reaction at 20 ° C. for 4 hours. The reaction mixture was poured into 1 liter of a 1% aqueous hydrochloric acid solution, and the resulting precipitate was filtered off, washed with pure water, dried, and NPCAS of MTPC.
11 g of a photosensitizer of the A ester compound was obtained. According to liquid chromatographic analysis, the diester content was 68.9.
%, And no NQASA impurity was detected.

(Example 2) [Synthesis of photosensitizer] 6 g (0.0128 mol) of MTPC, NQASC1
3.8 g (0.0513 mol) was dissolved in 120 g of dimethylacetamide, and a solution of 5.8 g (0.0513 mol) of triethylenediamine dissolved in 30 g of dimethylacetamide was gradually added dropwise thereto.
The reaction was performed at 4 ° C. for 4 hours. The reaction mixture was diluted with 1% aqueous hydrochloric acid 1
The resulting precipitate was separated by filtration, washed sufficiently with pure water, and dried to obtain 11.3 g of a photosensitizer of an esterified product. The diester content by liquid chromatography analysis was 70.5%, and no NQASA impurity was detected.

(Comparative Example 1) [Synthesis of Photosensitive Agent] A photosensitizer was synthesized under the same conditions as in Example 1 except that dioxane was used instead of dimethylacetamide. The sulfonic acid impurity was 3.6. %Met.

Comparative Example 2 [Synthesis of Photosensitive Agent] A photosensitizer was synthesized under the same conditions as in Example 1 except that dioxane was used instead of dimethylacetamide and triethylamine was used instead of triethylenediamine. The sulfonic acid impurity was 12.5%.

(Example 3) [Preparation of cresol-novolak resin] In a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, 43.3 g (0.40 g) of m-cresol was placed.
mol), 64.9 g of p-cresol (0.60 mol)
l), 52 g of 37% formalin aqueous solution and oxalic acid 3
g was charged and the temperature was raised to 100 ° C. while stirring, and the reaction was carried out for 16 hours. After the reaction, methyl isobutyl ketone 300
After dissolving in water and washing thoroughly with water, the solvent was removed to obtain 85 g of a cresol-novolak resin having a weight average molecular weight (GPC, calculated as polystyrene) of 4,000.

[Preparation of Positive Photoresist Composition and Its Performance Evaluation] 3 g of the photosensitizer obtained in Examples 1 and 2 and 10 g of the cresol / novolak resin synthesized above were dissolved in 56 g of ethyl lactate. After that, the mixture was filtered using a micro filter having a pore size of 0.2 μm to prepare a positive photoresist composition.

The obtained resist composition was spin-coated on a silicon wafer vapor-treated with hexamethyldisilazane using an auto coater, and prebaked at 90 ° C. for 60 seconds to obtain a film thickness of 1.05 μm. . This resist-coated wafer is converted into a reduced projection exposure apparatus NSR1755i7A.
After exposing through a mask pattern using (Nikon product name), baking at 110 ° C. for 50 seconds, 2.38%
With aqueous tetramethylammonium hydroxide solution
After developing with water, washing with water and drying with an auto developer, a resist pattern was obtained.

The obtained resist pattern was observed with a scanning electron microscope and evaluated by the following method. The results are shown in Table 1. i) Sensitivity: exposure amount at which the film thickness becomes 0 (threshold exposure amount). ii) Remaining film ratio: expressed as a percentage before and after development of an unexposed portion. iii) Resolution: The minimum dimension at the exposure amount at which the line and space image dimensions of the mask pattern and the resist pattern reproduce 1: 1 (± 10% tolerance). iv) Depth of focus: indicated a value of 0.5 μmL / S. v) Resist shape: From the electron micrograph of the cross section, the case where the angle between the wafer surface and the resist wall surface was 85 degrees or more was evaluated as good.

[0035]

[Table 1]

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention. Within the technical scope of

For example, in the above description, the cresol-novolak resin is used as the alkali-soluble resin in the positive photoresist composition of the present invention.
It goes without saying that the present invention is effective even if a styrene-maleic anhydride copolymer, polyvinyl hydroxybenzoate, polyhydroxystyrene, a carboxyl group-containing acrylic resin or the like is used.

[0038]

According to the present invention, a photosensitive agent having high sensitivity, high resolution, resist performance with a large alkali dissolution rate difference before and after exposure, and capable of drawing 0.35 μm or less by i-line exposure. And a positive photoresist composition containing the same can be produced, and its utility in the semiconductor industry is extremely high.

Claims (3)

[Claims] 1. A compound represented by the following general formula I: 1,2 naphthoquinone-2-diazido-5-sulfonyl chloride is added at a ratio of 2.5 mol or more and 4.5 mol or less to 1 mol of methylenetetra-p-cresol represented by the following formula, and dimethylacetamide is added to the solvent. A method for producing a photosensitizer, comprising the steps of: subjecting an esterification reaction in the presence of triethylenediamine, pouring the reaction solution into an aqueous hydrochloric acid solution, filtering the formed precipitate, washing with water, and drying. 2. At least 2.5 mol or more of 1,2 naphthoquinone-2-diazido-5-sulfonyl chloride to 1 mol of methylenetetra-p-cresol.
A positive photoresist composition comprising a photosensitizer obtained by an esterification reaction in the presence of triethylenediamine using dimethylacetamide as a solvent in an amount of 5 mol or less and an alkali-soluble resin. 3. The positive photoresist composition according to claim 2, wherein the alkali-soluble resin is a cresol novolak resin.