JP2568883B2 - Positive photoresist composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a specific alkali-soluble novolak resin and 1,2
A quinonediazide compound, a positive photoresist composition sensitive to ultraviolet rays, far ultraviolet rays, X-rays, electron beams, molecular beams, γ-rays, radiation such as synchrotron radiation, and has resolution, sensitivity, heat resistance, The present invention relates to a photoresist composition for fine processing excellent in developability.

The positive photoresist according to the present invention is applied to a semiconductor wafer or a substrate made of glass, ceramics, metal or the like by a spin coating method or a roller coating method to a thickness of 0.5 to 3 μm. After that, it is heated and dried, and the circuit pattern and the like are baked by ultraviolet irradiation or the like through an exposure mask,
Development gives a positive image. Further, pattern processing can be performed on the substrate by performing etching using the positive image as a mask. Typical application fields are semiconductor manufacturing processes such as ICs, manufacturing of circuit boards such as liquid crystals and thermal heads, and other photo-fabrication processes.

<Conventional Technology> As a positive photoresist composition, a composition containing an alkali-soluble resin and a naphthoquinonediazide compound as a photosensitive material is generally used. For example, US Pat. No. 3,666,473, US Pat. No. 4,115,128, and US Pat. No. 3,666,473 as “Novolak-type phenolic resin / naphthoquinonediazide-substituted compound”
No. 4173470, and the most typical composition is a "novolak resin comprising cresol-formaldehyde /
An example of “trihydroxybenzophenone-1,2-naphthoquinonediazidesulfonic acid ester” is Thompson “Introduction to Microlithography” (L.
F. Thompson "Introduction to Microlithography")
(ACS Publishing, No. 219, pp. 112-121).

Novolak resin as a binder is soluble in an alkaline aqueous solution without swelling, and is particularly useful in this application because it gives high resistance to plasma etching especially when the generated image is used as a mask for etching. It is. Further, the naphthoquinonediazide compound used in the photosensitive material itself acts as a dissolution inhibitor that reduces the alkali solubility of the novolak resin, but when decomposed by irradiation with light, generates an alkali-soluble substance and rather increases the alkali solubility of the novolak resin. It is unique in that it acts to enhance it, and is particularly useful as a photosensitive material for a positive photoresist because of its large property change to light.

From this point of view, a number of positive photoresists containing a novolak resin and a naphthoquinonediazide-based photosensitive material have been developed and put into practical use, and satisfactory results have been achieved in line width processing down to about 1.5 μm to 2 μm. Was.

<Problems to be Solved by the Present Invention> However, integrated circuits have been increasingly integrated,
2. Description of the Related Art In the manufacture of semiconductor substrates such as LSIs, it has become necessary to process ultrafine patterns having a line width of 1 μm or less. In such applications, there is a demand for a photoresist having particularly high resolution, high pattern shape reproduction accuracy for accurately capturing the shape of an exposure mask, and high sensitivity from the viewpoint of high productivity.

In addition, in order to increase the degree of integration of integrated circuits, the etching method has shifted from the conventional wet etching method to the dry etching method, but during dry etching, the temperature of the resist rises, causing thermal deformation and the like. High heat resistance is required for the resist so that it does not exist. Use a resin containing no component having a weight average molecular weight of 2000 or less to improve the heat resistance of the resist (JP-A-60-97347), and use a resin having a total content of from monomer to trimer of 10% by weight or less. (JP-A-60-189739) is disclosed. However, when a resin from which the above-mentioned low molecular weight component is removed or reduced is used, there is a drawback that sensitivity is usually lowered and adhesion to a silicon substrate is further deteriorated.

On the other hand, when the exposed portion which should be removed by the development is not sufficiently removed and a slight residue is generated, or when the surface layer of the fine resist pattern in the unexposed portion is peeled off, poor development occurs. When a substrate having a resist pattern having a defective development is etched, a portion to be etched is not etched, and as a result, the ratio of defective chips to the total number of chips in one wafer increases. In particular, when such a residue is generated between the patterns, the substantial resolution is reduced, and a resist that does not cause development failure has been required at the same time.
In fact, conventional positive photoresists cannot sufficiently meet these demands.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a positive photoresist composition which does not generate resist residue and scum in an exposed portion, particularly in the production of semiconductor devices.

A second object is to provide a positive photoresist composition having high resolution.

A third object of the present invention is to provide a positive photoresist composition which can provide a resist image having high sensitivity and excellent heat resistance.

<Means for Solving the Problems> The inventors of the present invention have paid careful attention to the above-mentioned properties and made intensive studies. As a result, in a positive photosensitive resin composition containing a quinonediazide compound and an alkali-soluble novolak resin, By controlling the dimer content to be in a specific range, it was found to be useful for eliminating poor development and obtaining a high resolution, and thus completed the present invention.

Furthermore, the present inventors have found that this effect is particularly remarkable when a specific quinonediazide compound is blended with the specific novolak resin.

That is, an object of the present invention is to provide a photosensitive resin composition containing a quinonediazide compound and an alkali-soluble novolak resin, wherein the alkali-soluble novolak resin dissolves the synthesized novolak resin in a polar solvent and then water or a water-polar solvent mixture. Method to precipitate resin content by placing in water, or 10 mmHg at 250 ° C or higher
The amount of dimer contained in the resin was adjusted to the range of 2 to 6% by weight of the novolak resin by the following vacuum distillation method.
A positive photoresist composition comprising a 1,2-naphthoquinonediazidosulfonic acid ester of a polyhydroxy compound having 5 or more aromatic hydroxyl groups in a molecule.

 Hereinafter, the present invention will be described in detail.

The alkali-soluble novolak resin used in the present invention can be obtained by subjecting 0.5 to 1.0 mol of aldehyde to addition condensation of 1 mol of phenol in the presence of an acidic catalyst and then partially removing a dimer component.

As the phenols, phenol, m-chlorophenol, p-chlorophenol, o-chlorophenol, m-cresol, p-cresol, o-cresol, ethylphenol, xylenol, resorcinol, naphthol, etc., alone or in combination of two or more Can be used in combination. In addition, as aldehydes,
Formaldehyde, paraformaldehyde, acetaldehyde, furfural and the like can be used, and as the acidic catalyst, hydrochloric acid, sulfuric acid, formic acid, acetic acid, oxalic acid and the like can be used.

The weight average molecular weight of the thus obtained novolak resin is preferably in the range of 2,000 to 30,000. If it is less than 2000, the film loss of the unexposed portion after development is large, and if it exceeds 30,000, the development speed is reduced. Particularly suitable is
It is in the range of 6000-20000.

Here, the weight average molecular weight is defined as a value in terms of polystyrene of gel permeation chromatography.

As a method for adjusting the dimer component, for example, after synthesizing a novolak resin according to a conventional method, methanol, ethanol, acetone, methyl ethyl ketone, dioxane,
There is a method in which the resin is dissolved in a polar solvent such as tetrahydrofuran and then added to water or a water-polar solvent mixture to precipitate a resin component. As another method, when synthesizing an alkali-soluble resin, after reaction for a predetermined time, water, unreacted monomer, formaldehyde and oxalic acid are usually removed by distillation under reduced pressure at 150 ° C to 200 ° C. On the other hand, 230 ° C or higher, preferably 2
By performing distillation under reduced pressure of 10 mmHg or less at 50 ° C. or more, dimer components can be efficiently distilled off.

The dimer content of the novolak resin used in the present invention is in the range of 2 to 6% by weight of the whole resin. It is preferable that the content of the dimer is small in order to eliminate poor development and increase the resolving power. However, when the content is reduced to less than 2%, not only the solubility in an alkaline aqueous solution is deteriorated, but also the sensitivity is lowered. The resolution, which is one of the factors, also decreases. Further, a disadvantage that adhesion to the silicon substrate is deteriorated occurs, which is not preferable.

It is not clear why the dimer content is related to the resolving power and developability of the photoresist, but the same effect cannot be obtained even if the amount of other low molecular weight components in the novolak resin, that is, the remaining monomer or trimer, is adjusted. Therefore, it is presumed that this is a dimer-specific effect.

In order to exhibit the effects of the present invention, the phenolic compound serving as the raw material of the novolak resin is not limited to the kind as described above, but it is preferable that one of its components contains p-cresol.

As the 1,2-quinonediazide compound used in the present invention, 1,2-naphthoquinonediazide-5-sulfonic acid,
1,2-naphthoquinonediazide-4-sulfonic acid or 1,2
Esters of benzoquinonediazide-4-sulfonic acid and polyhydroxyaromatic compounds are used.

The polyhydroxy aromatic compound is a polyhydroxy compound having 5 or more aromatic hydroxyl groups in one molecule, for example, 2,4,6,3 ', 4', 5'-hexahydroxybenzophenone , 2,3,4,3 ', 4', 5'-Hexahydroxybenzophenone and other polyhydroxybenzophenones, polyhydroxyphenylalkyl ketones, bis (2,3,4-trihydroxyphenyl) ) Bis [(poly) hydroxyphenyl] alkanes such as methane, polyhydroxybenzoates, bis (2,3,4-trihydroxybenzoyl) methane, bis (2,3,4-trihydroxybenzoyl) benzene (Polyhydroxybenzoyl) alkane or bis (polyhydroxybenzoyl) aryls, alkylene-di (polyhydroxybenzoates), 2,4,6,3 ', 5'-biphenyl pen Polyhydroxybiphenyls such as tall, 2,4,6,2 ', 4', 6'-biphenylhexol, 4,4 ', 2 ", 3", 4 "-pentahydroxy-3,5, Polyhydroxytrif such as 3 ', 5'-tetramethyltriphenylmethane, 2,3,4,2', 3 ', 4', 3 ", 4"-octahydroxy-5,5'-diacetyltriphenylmethane Enylmethanes, 3,3,3 ', 3'-tetramethyl-1,1'-spirobi-indane-5,6,7,5',
6 ', 7'-hexol, 3,3,3', 3'-tetramethyl-
1,1'-spirobi-indane-4,5,6,4 ', 5', 6'-hexol, 3,3,3 ', 3'-tetramethyl-1,1'-spirobi-indane-4, Polyhydroxyspirobi-indanes such as 5,6,5 ', 6', 7'-hexol and flavono dyes such as quercetin and rutin can be used.

By using such a photosensitive agent comprising a 1,2-naphthoquinonediazidosulfonic acid ester of a polyhydroxy compound having five or more aromatic hydroxyl groups in one molecule for a part or all of the photosensitive agent, the present invention The effect becomes more remarkable.

Examples of such polyhydroxy compounds are preferably pentahydroxybenzophenones, hexahydroxybenzophenones, bis (trihydroxyphenyl) methanes, and bis (trihydroxybenzoyl) methane among the above-mentioned compounds exemplified by the photosensitizer. And benzenes, biphenylpentol and hexols, pentahydroxytriphenylmethanes, hexahydroxytriphenylmethanes, octahydroxytriphenylmethanes, spirobiindanehexools, and some flavono dyes And the like.

The ratio of the photosensitive material to the alkali-soluble novolak resin in the present invention is 5 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the novolak resin. When the use ratio is 5 parts by weight or less, the residual film ratio is significantly reduced,
On the other hand, if it exceeds 100 parts by weight, sensitivity and solubility in a solvent decrease.

In the present invention, a polyhydroxy compound can be further contained to promote dissolution in a developer. Preferred polyhydroxy compounds include phenols, resorcinol, phloroglucin, 2,3,4-trihydroxybenzophenone, 2,3,4,4'-tetrahydroxybenzophenone, acetone-pyrogallol condensed resin, phloroglucid and the like. It is.

Examples of the solvent for dissolving the photosensitive material of the present invention and the alkali-soluble novolak resin include ketones such as methyl ethyl ketone and cyclohexanone; alcohol ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; ethers such as dioxane and ethylene glycol dimethyl ether. Cellosolve esters such as methyl cellosolve acetate and ethyl cellosolve acetate; fatty acid esters such as butyl acetate, methyl lactate and ethyl lactate; halogenated hydrocarbons such as 1,1,2-trichloroethylene; dimethylacetamide;
-Highly polar solvents such as methylpyrrolidone, dimethylformamide and dimethylsulfoxide can be exemplified.
These solvents can be used alone or as a mixture of a plurality of solvents.

The positive photoresist composition of the present invention may optionally contain a dye, a plasticizer, an adhesion aid, a surfactant, and the like. Specific examples include dyes such as methyl violet, crystal violet, and malachite green; plasticizers such as stearic acid, acetal resins, phenoxy resins, and alkyd resins; and adhesion promoters such as hexamethyldisilazane and chloromethylsilane. And surfactants such as nonylphenoxypoly (ethyleneoxy) ethanol and octylphenoxypoly (ethyleneoxy) ethanol.

The above-mentioned positive photoresist composition is applied on a substrate (eg, silicon / silicon dioxide coating) to be used in the manufacture of precision integrated circuit devices by an appropriate application method such as a spinner or a coater, and then exposed through a predetermined mask. Then, a good resist can be obtained by developing.

Examples of the developer for the positive photoresist composition of the present invention include 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 -butylamine, triethylamine,
Tertiary amines such as methyldiethylamine; alcoholamines such as dimethylethanolamine and triethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; and cyclic amines such as pyrrole and piperidine. Aqueous solutions of alkalis can be used. Further, an appropriate amount of an alcohol or a surfactant may be added to the aqueous solution of the above alkalis for use.

<Effect of the Invention> The positive photoresist of the present invention is particularly excellent in resolving power and developability, does not leave development residues such as scum in exposed portions, has excellent heat resistance, and is suitable as a photoresist for fine processing. What is used.

<Examples> Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto. In addition,% shows weight% unless otherwise specified. The weight average molecular weight and the content of the monomer, dimer or trimer were measured as follows.

The measurement was carried out using gel permeation chromatography (GPC) at 40 ° C., a flow rate of 1 ml / min, a THF solvent, and a detection wavelength of 282 nm. The column used was TSK gel G manufactured by Toyo Soda Kogyo.
One each of MH _XL , G4000H _XL , G3000H _XL , and G2000H _XL was connected, and the weight average molecular weight was calculated using monodisperse polystyrene as a standard.

The contents of the monomer to the trimer were measured and calculated under the same conditions.

Comparative Examples 1-3 (1) Synthesis of novolak resin (a) (Comparative Example) (1)-(i) 60 g of m-cresol, 40 g of p-cresol, 53 g of 37% formalin aqueous solution and 0.1 g of oxalic acid in a three-necked flask. The mixture was heated to 100 ° C. while stirring and charged, and reacted for 15 hours. Thereafter, the temperature was raised to 200 ° C. and the pressure was gradually reduced to 5 mmHg, and water, unreacted monomers, formaldehyde, oxalic acid and the like were distilled off. Next, the molten alkali-soluble novolak resin was returned to room temperature and collected. The obtained novolak resin had a weight average molecular weight of 11,000 (in terms of polystyrene), and the contents of the monomer, dimer and trimer were each 0.1.
They were 50%, 13.4% and 6.9% (20.8% in total).

(1)-(ii) After completely dissolving 20 g of the novolak resin obtained in (1)-(i) in 62 g of methanol, 28 g of water was gradually added thereto with stirring to precipitate a resin component. The upper layer was removed by decantation, and the precipitated resin was recovered, heated to 40 ° C. and dried under reduced pressure for 24 hours to obtain the desired alkali-soluble novolak resin (a). The obtained novolak resin has a weight average molecular weight of 14,500 (in terms of polystyrene), the content of each of the monomer, dimer and trimer is 0%,
7.0% and 4.0% (11.0% in total).

(2) Synthesis of novolak resin (b) (the present invention) 40 g of m-cresol, 60 g of p-cresol, 47 g of 37% formalin aqueous solution and 0.1 g of oxalic acid were charged into a three-necked flask, and heated to 100 ° C. while stirring, The reaction was performed for 15 hours. Thereafter, the temperature was raised to 250 ° C. and the pressure was gradually reduced to 1 mmHg, and water, unreacted monomers, formaldehyde, oxalic acid, dimer components, and the like were distilled off. Next, the molten alkali-soluble novolak resin was returned to room temperature and collected. The obtained novolak resin had a weight average molecular weight of 7,700 (in terms of polystyrene), and the contents of monomer, dimer, and trimer were 0%, 5.2%, and 8.1%, respectively (13.3% in total).

(3) Synthesis of novolak resin (c) (the present invention) 25 g of m-cresol, 50 g of p-cresol, 28 g of 2,5-xylenol, 53 g of 37% aqueous solution of formalin and 0.3 g of oxalic acid
1 g was charged into a three-necked flask, and the temperature was raised to 100 ° C. while stirring, and the mixture was reacted for 15 hours. Thereafter, the temperature was raised to 250 ° C. and the pressure was gradually reduced to 1 mmHg, and water, unreacted monomers,
Formaldehyde, oxalic acid, dimer components and the like were distilled off. Next, the molten alkali-soluble novolak resin was returned to room temperature and collected. The obtained novolak resin has a weight average molecular weight of 4800 (in terms of polystyrene), and the contents of monomer, dimer and trimer are 0.5%, 5.9%,
It was 9.0% (15.4% in total).

(4) Synthesis of photosensitive material (Comparative Example) 9.3 g of 2,3,4,4'-tetrahydroxybenzophenone,
1,3-Naphthoquinonediazide-5-sulfonyl chloride 28.0 g and acetone 270 ml were charged into a three-necked flask,
The mixture was uniformly dissolved with stirring. Then 11.1 g of triethylamine
Was gradually added dropwise and reacted at room temperature for 1 hour. After completion of the reaction, the content was dropped into a 1% aqueous hydrochloric acid solution, and the resulting precipitate was separated, washed with methanol and dried to obtain an ester compound of 2,3,4,4'-tetrahydroxybenzophenone. Was.

(5) Preparation and evaluation of positive photoresist composition 1.30 g of photosensitive material obtained in (4) and novolak resin (a), (b) and (c) obtained in (1) to (3), respectively Dissolve 5g in ethyl cellosolve acetate 15g, 0.2
The mixture was passed through a microfilter of μm to prepare a photoresist composition. This photoresist composition was applied to a silicon wafer using a spinner, and dried in a convection oven under a nitrogen atmosphere at 90 ° C. for 30 minutes to form a film having a thickness of 1.5 μm.
Was obtained. The film was exposed using a reduction projection exposure apparatus, developed with a 2.38% aqueous solution of tetramethylammonium hydroxide for 1 minute, washed with water for 30 seconds, and dried. The resist pattern on the silicon wafer thus obtained was observed with a scanning electron microscope to evaluate the resist. The results are shown in Table 1 below. 2.0μm sensitivity
Is defined as the reciprocal of the exposure amount that reproduces the mask pattern of Example 1, and the relative value of the sensitivity of Comparative Example 1 is shown. 2.0μ resolution
It represents the critical resolution at the exposure dose for reproducing the m mask pattern. The heat resistance was a temperature at which the resist-patterned silicon wafer was baked in a convection oven for 30 minutes and the pattern did not deform. Developability is
The resist pattern was observed with a scanning electron microscope, and the presence or absence of resist residue and scum in the exposed portion was examined. The results were compared for the novolak resins (a) to (c) with Comparative Examples 1 to 3.
The results are shown in Table 1.

Examples 1-4 Using the novolak resin synthesized in (2) and (3) above,
Each photosensitive material described in Table 2 below was synthesized in the same manner as in (4), and the resist composition was evaluated in the same manner as in (5). The results are shown in Table 1.

As can be seen, the positive photoresist of the present invention was excellent in resolution, heat resistance and developability.

In particular, in these comparative examples, as is clear from comparison with Examples 2 and 3, a remarkably excellent resolution was obtained, and the combination with a specific photosensitive agent was effective for the effect of the present invention. It will be understood that it is more prominent.

Comparative Examples 4 to 5 Novolak resins (d) and (e) shown in Table 3 below were synthesized in the same manner as in the above (1) to (i). 5 g of this novolak resin and 1.30 g of the photosensitive material obtained in the above (4) were dissolved in 15 g of ethyl cellosolve acetate, and the resist composition was evaluated in the same manner as in Examples. The results are shown in Table 1. The sensitivity, resolution, heat resistance and developability were inferior to those of the examples.

Comparative Example 6 Novolak resin (f) shown in Table 3 below was synthesized in the same manner as in (2) above. At this time, by extending the dimer distillation time, the dimer content was reduced to 1.3%. 5 g of this novolak resin and 1.30 g of the photosensitive material obtained in the above (4) were dissolved in 15 g of ethyl cellosolve acetate, and the resist composition was evaluated in the same manner as in Examples. The results are shown in Table 1. Compared to the examples, the sensitivity and the resolving power were inferior, and the adhesion of the pattern was poor.

Comparative Example 7 5 g of the novolak resin used in Comparative Example 4 and 1.3 g of the photosensitive material used in Example 2 were dissolved in 15 g of ethyl cellosolve acetate, and the resist composition was evaluated in the same manner as in Example. The results are shown in Table 1. Indicated.

Comparative Example 8 5 g of the novolak resin used in Comparative Example 5 and 1.3 g of the photosensitive material used in Example 3 were dissolved in 15 g of ethyl cellosolve acetate, and the resist composition was evaluated in the same manner as in Example. The results are shown in Table 1. Indicated.

Each of Comparative Examples 7 and 8 was inferior in resolution, heat resistance, and developability as compared with the examples.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadayoshi Kokubo 4000 Kawajiri, Yoshida-cho, Haibara-gun, Shizuoka Prefecture Inside Fuji Photo Film Co., Ltd. (56) References JP-A-60-150047 (JP, A) JP-A-62- 10646 (JP, A) JP-A-60-45238 (JP, A) JP-A-62-227144 (JP, A) JP-A-62-284354 (JP, A) JP-A-62-150245 (JP, A)

Claims (1)

(57) [Claims] 1. A photosensitive resin composition comprising a quinonediazide compound and an alkali-soluble novolak resin, wherein the alkali-soluble novolak resin is prepared by dissolving the synthesized novolak resin in a polar solvent and then adding the resulting solution to water or a water-polar solvent mixture. The amount of dimer contained in the resin is adjusted to a range of 2 to 6% by weight of the novolak resin by a method of precipitating the resin component or a method of distilling the resin under a reduced pressure of 10 mmHg or less at 250 ° C. or higher. A positive photoresist composition characterized in that the quinonediazide compound contains a 1,2-naphthoquinonediazidesulfonic acid ester of a polyhydroxy compound having 5 or more aromatic hydroxyl groups in one molecule.