JPH0519462A - Photoresist composition - Google Patents

Abstract

PURPOSE:To obtain a photoresist compsn. having high resolution, satisfactory shelf stability and uniform appliability. CONSTITUTION:This photoresist compsn. contains a base resin, quinone- diazidosulfonic ester as a radiation sensitive compd. and lower alkyl ester of 3-oxypropionic acid and/or lower alkyl ester of 3-alkoxypropionic acid as a solvent. The quinonediazidosulfonic ester is prepd. by esterifying at least part of hydroxyl groups in novolak resins having 300-4,000 weight average mol.wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a radiation-sensitive photoresist composition, and more particularly to improvement of a photoresist composition comprising a base resin, a radiation-sensitive compound and a solvent.

[0002]

2. Description of the Related Art Integrated circuits have become highly integrated year by year, and dynamic random access memories (DRA) have been developed.
Taking M) as an example, at present, full-scale production of a device having a storage capacity of 4 Mbits has started. Along with this, demands for photolithography technology, which is indispensable for the production of integrated circuits, are becoming stricter year by year. For example, in the production of 1M bit DRAM, a 1 μm level lithography technology is required, and in 4M and 16MDRAM,
It is said that lithography techniques of 0.8 μm level and 0.5 μm level are required respectively.

In recent years, various high-resolution photoresists have been developed to meet this demand. These high-resolution photoresists are generally used in a method such as increasing the compounding ratio of the radiation-sensitive compound or increasing the introduction amount of the radiation-sensitive group in the molecule of the radiation-sensitive compound as compared with the conventional photoresist. Has achieved high resolution. However, along with this, the solubility in the solvent when preparing the photoresist solution is reduced, the photoresist solution cannot be prepared, or the storage stability is reduced and there are problems such as generation of fine particles in a short time. Yes, it is not preferable for practical use.

As a high-resolution photoresist, a photoresist containing a quinonediazide sulfonic acid ester of a low molecular weight novolak resin as a radiation-sensitive compound has been proposed, but it has a storage stability or a coating property. In that respect, it has not been sufficiently examined. On the other hand, the problem of safety has been pointed out in recent years for ethyl cellosolve acetate, which is a solvent conventionally used for photoresist compositions, and a solvent that can replace it has been demanded. For example, JP-A-62-123444 discloses the use of monooxymonocarboxylic acid esters as a solvent for a radiation-sensitive resin composition, and ethyl lactate contained in such a solvent has been recently Although it has been proposed as a highly safe solvent, the viscosity of the photoresist solution becomes high, and in the large-diameter wafers that have recently begun to be used for LSI manufacturing, the coating uniformity within the wafer surface deteriorates, which is an industrial value. Has been raised.

[0005]

DISCLOSURE OF THE INVENTION The present invention is premised on a photoresist having a high resolution in which a radiation-sensitive compound is a quinonediazide sulfonic acid ester of a low molecular weight novolak resin, and is safe as a solvent. (EN) It is intended to provide a photoresist which uses a solvent free from the above problems, has good storage stability, has an appropriate viscosity, and has good coating uniformity. As a result of studies to achieve such an object, the present inventors have found that the intended purpose can be achieved by using a specific solvent.

[0006]

DISCLOSURE OF THE INVENTION The gist of the present invention is to provide a photoresist composition containing a base resin, a radiation-sensitive compound and a solvent, and at least the hydroxyl group of novolak resins having a weight average molecular weight of 300 to 4000 as the radiation-sensitive compound. A photoresist composition, characterized in that a partially esterified quinonediazide sulfonic acid ester compound is used, and 3-oxypropionic acid lower alkyl ester and / or 3-lower alkoxypropionic acid lower alkyl ester is used as a solvent. Exist in.

The present invention will be described in more detail below. The base resin in the present invention is generally an alkali-soluble resin, and more specifically, a novolac resin is used. Examples of the novolac resin include phenols such as phenol, resorcinol, and catechol; o-cresol,
Alkylphenols such as m-cresol, p-cresol, 3-ethylphenol, 2,5-xylenol, 3,5-xylenol; 2-methoxyphenol, 4-
Alkoxy or allyloxyphenols such as methoxyphenol and 4-phenoxyphenol; naphthols which may be substituted with an alkyl group such as α-naphthol, β-naphthol and 3-methyl-α-naphthol;
3-dihydroxybenzene, 1,3-dihydroxy-2
-Polyhydroxy which may be substituted with an alkyl group such as methylbenzene, 1,2,3-trihydroxybenzene, 1,2,3-trihydroxy-5-methylbenzene and 1,3,5-trihydroxybenzene Hydroxy aromatic compounds such as benzene are converted to formaldehyde, paraformaldehyde, acetaldehyde and other aliphatic aldehydes, benzaldehyde and other aromatic aldehydes,
Examples thereof include those produced by heating and polycondensing a carbonyl compound such as an alkyl ketone such as acetone in the presence of an acidic catalyst such as hydrochloric acid, sulfuric acid or oxalic acid.

The hydroxyaromatic compound may have a substituent such as a halogen atom, a nitro group or an ester group as long as it does not adversely affect the present invention. If desired, these resins may be further reduced with hydrogen or the like to reduce absorption in the short wavelength region. The optimum weight average molecular weight of the base resin is usually 2,000 to 30,000, preferably 3,000 to 20,000, and is larger than the molecular weight of the novolak resin, which is the base of the radiation-sensitive compound described later, and the two are clearly distinguished.

In the present invention, it is an essential requirement to use, as the radiation-sensitive compound, a quinonediazide sulfonic acid ester compound in which at least a part of the hydroxyl groups of the novolak resins having a weight average molecular weight of 300 to 4000 are esterified. To do. As the novolak resins having a weight average molecular weight of 300 to 4000, there are novolak resins which are polycondensates of hydroxyaromatic compounds and carbonyl compounds as exemplified as the base resin and have a weight average molecular weight of 300 to 4000. Can be mentioned. Such novolak resins require at least a part of the hydroxyl groups to be esterified with a quinonediazide sulfonic acid compound, and preferably, the esterification rate of the quinonediazide sulfonic acid esterified product [(quinonediazide sulfonic acid ester compound per quinonediazide sulfonic acid ester molecule is Number of sulfone groups) ×
100 / (number of hydroxyl groups per molecule of novolac resin)]
Is 35 to 90%.

Examples of the quinonediazide sulfonic acid ester are 1,2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-4-sulfonic acid ester and 1,2-naphthoquinonediazide-5-ester.
Sulfonic acid esters are preferred. More specifically, the radiation-sensitive compound of the present invention is a 1,2-benzoquinonediazide-4-sulfonic acid ester of a novolak resin represented by the following general formula [A] and having a weight average molecular weight of 300 to 4000: , 2-naphthoquinonediazide-4-sulfonic acid ester or 1,2-naphthoquinonediazide-5-sulfonic acid ester compound.

[0011]

[Chemical 1]

(In the formula, R ¹ represents a lower alkyl group having 1 to 4 carbon atoms, and when m is an integer of 2 or more, a plurality of R ¹ may be the same or different, and R ² and R ³ are respectively Independently represent a hydrogen atom, a lower alkyl group having 1 to 4 carbon atoms or an aryl group, Q represents a hydroxyl group, 1 is an integer of 1 to 4, and m is 0.
Represents an integer of 3 and n is an integer of 3 to 35. )
The weight average molecular weight of the novolak resin, which is the matrix of the radiation-sensitive compound, is preferably 400 to 2500.

The radiation-sensitive compound itself of the present invention is a novolak obtained by polycondensing a hydroxyaromatic compound and a carbonyl compound in the presence of an acidic catalyst according to a conventionally known method (for example, described in JP-B-3-502010). Resin 1, 2
-A naphthoquinone diazide-5-sulfonic acid chloride or the like can be used for sulfonic acid ester production. In the present invention, as a solvent for a photoresist containing such a radiation-sensitive compound, 3-oxypropionic acid lower alkyl ester and / or 3-lower is particularly preferable among monooxymonocarboxylic acids known as solvents for radiation-sensitive resin compositions. It is characterized in that a lower alkyl ester of alkoxypropionic acid is used. Here, the term "lower" means having 1 to 3 carbon atoms.

Specific examples of such a solvent include methyl 3-hydroxypropionate, ethyl 3-hydroxypropionate, propyl 3-hydroxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate and 3-methoxypropione. Propyl acid, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, propyl 3-ethoxypropionate, methyl 3-propoxypropionate, ethyl 3-propoxypropionate, and propyl 3-propoxypropionate.

Of these, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate and ethyl 3-ethoxypropionate are particularly preferable. The photoresist composition of the present invention is
By using 3-oxypropionic acid lower alkyl ester and / or 3-lower alkoxypropionic acid lower alkyl ester as the solvent, for example, the coating uniformity is better than that of ethyl lactate which has been proposed in recent years.

In the present invention, it is also possible to use a solvent mixed with ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, ethyl lactate, ethyl pyruvate, xylene, etc. within a range that does not impair the effects of the present invention. In this case, the preferable mixing ratio is usually 50% by weight or more, and preferably 70% by weight in the whole solvent.
It is better to use above.

The concentration of the alkali-soluble resin in the photoresist composition of the present invention is usually 1 to 30% by weight, and the concentration of the radiation-sensitive compound is 0.1 to 15% by weight. The ratio of the radiation-sensitive compound to the alkali-soluble resin is usually 0.1 to 0.5 times by weight. Further, in the present invention, for example, a surfactant is added to improve coatability, a light-absorbing material is added to reduce influence of diffused light from the substrate, and an additive such as a sensitizer is added to improve sensitivity. You can also do it.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples unless the gist thereof is exceeded. Examples 1 to 3 and Comparative Examples 1 to 2 m-cresol, p-cresol as a base resin,
A novolak resin having a weight average molecular weight shown in Table 1, produced from 2,5-xylenol and formaldehyde, the following radiation-sensitive compounds AE and methyl 3-methoxypropionate were mixed and dissolved at a ratio shown in Table 1. Furthermore, in order to further improve the coating property, a fluorine-based surfactant (trade name "Florard" FC-430 Sumitomo 3M Limited)
(Manufactured by the same company) was added at 100 ppm and microfiltered with a 0.2 μm Teflon filter to prepare a photoresist composition.

Photosensitizer A: 1,2-naphthoquinonediazide-5-sulfonic acid ester of resin (weight average molecular weight 1300) obtained by polycondensing pyrogallol and acetone (photoesterification rate 50%) Photosensitizer B : 1,2-naphthoquinonediazide-5-sulfonic acid esterified product of resin (weight average molecular weight 1000) obtained by polycondensing m-cresol and formaldehyde (photoesterification rate 65%) C: m- 1,2-naphthoquinonediazide-5-sulfonic acid esterified product of resin (weight average molecular weight 1000) obtained by polycondensing cresol and acetaldehyde (photoesterification rate 40%) Photosensitizer D: 2, 3, 4, Total esterification product of 1,2-naphthoquinonediazide-5-sulfonic acid of 4'-tetrahydroxybenzophenone Photosensitizer E: 2 , 2 ', 4,4'-Tetrahydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonic acid total esterified product

These photoresist compositions were heated and kept at 40 ° C. for 4 weeks and examined for storage stability. To determine the storage stability, a photoresist composition was applied to a 5-inch silicon wafer, and a laser surface inspection device (LS-500) was used.
0, manufactured by Hitachi Electronics Engineering Co., Ltd.), and the number of particles of 0.3 μm or more in the photoresist film was measured and judged. Further, the limiting resolution of these photoresists was measured by the following method.

The photoresist composition was applied to a 5 inch silicon wafer and heated on a hot plate at 80 ° C. for 9 hours.
Baking was performed for 0 seconds to form a resist film having a thickness of 1.22 μm. This is an i-line stepper (NSR1755i
7A Nikon), and then baked on a hot plate at 110 ° C. for 90 seconds, and then 2.38.
% Tetramethylammonium hydroxy aqueous solution for 1 minute. The electron microscopic observation was used to determine to what extent the fine pattern was resolved at the exposure amount at which the test pattern with the limiting resolution of 0.6 μm was resolved to 0.6 μm on the wafer. The results are summarized in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

Example 4 As a result of conducting the same experiment as in Example 3 except that the solvent was changed to ethyl 3-ethoxypropionate in Example 3,
The number of particles was 2 before heating and holding, and 3 after heating and holding. Example 5 and Comparative Example 3 Methyl 3-methoxypropionate (Example 5) or ethyl lactate (Comparative Example 3) was used as a solvent, and the photoresist composition was placed on an 8-inch silicon wafer at 4000.
Approximately 1.20 when spin-coated at rpm
The amount of solvent was adjusted so as to obtain a coating film thickness of μm, and Example 1 was used.
A photoresist composition was prepared according to.

The contents of the photosensitizer, the novolak resin and the solvent in the photoresist composition are as follows.
1 g, novolac resin 74.7 g and solvent 276.2 g
Comparative Example 3 contained 17.9 g of the photosensitizer, 69.9 g of the novolac resin, and 282.2 g of the solvent. The viscosity of this photoresist composition and 1.2 for an 8-inch wafer
The coating uniformity was measured when coating was performed so that the coating film thickness was 0 μm. The viscosity of Example 5 was 12 cp and the coating uniformity was 34 Å, and the viscosity of Comparative Example 3 was 33 cp and the coating uniformity was 124 Å. The coating uniformity is the result of measuring the film thickness at 9 points on the resist film surface as a value of 3σ, where 3σ means a statistical probability and the measured value has a normal distribution. This means that 99.7% is distributed in ± 3σ values.

[0026]

INDUSTRIAL APPLICABILITY According to the present invention, in a photoresist using a quinonediazide sulfonic acid ester of a low molecular weight novolak resin as a radiation-sensitive compound, 3-oxypropionic acid lower alkyl ester and By using / or 3-lower alkoxypropionic acid lower alkyl ester, a photoresist having good storage stability and coating uniformity and high resolution can be obtained, which is extremely useful in practice.

Claims (1)

Claim: What is claimed is: 1. A photoresist composition containing a base resin, a radiation-sensitive compound and a solvent, wherein at least a part of hydroxyl groups of novolak resins having a weight average molecular weight of 300 to 4000 is an ester as the radiation-sensitive compound. A photoresist composition comprising a quinonediazide sulfonic acid esterified compound and a 3-oxypropionic acid lower alkyl ester and / or a 3-alkoxypropionic acid lower alkyl ester as a solvent.