JP3019484B2 - Photoresist composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to radiation-sensitive photoresist compositions, and more particularly to improvements in photoresist compositions comprising a base resin, a radiation-sensitive compound, and a solvent.

[0002]

2. Description of the Related Art Integrated circuits are becoming highly integrated with each passing year, and dynamic random access memories (DRA) are being developed.
Taking M) as an example, full-scale production has been started at present with a storage capacity of 4 Mbits. As a result, the demand for photolithography technology, which is indispensable for the production of integrated circuits, is increasing year by year. For example, the production of 1 Mbit DRAM requires a lithography technology of 1 μm level.
It is said that lithography techniques of 0.8 μm 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 such methods as increasing the proportion of the radiation-sensitive compound or increasing the amount of radiation-sensitive groups introduced into the radiation-sensitive compound molecules, as compared to conventional photoresists. To achieve high resolution. However, along with this, the solubility in a solvent when preparing a photoresist solution is reduced, and the photoresist solution cannot be prepared, or storage stability is reduced and fine particles are generated in a short time. Yes, not practically preferable.

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. In this respect, sufficient studies have not been made yet. On the other hand, ethyl cellosolve acetate, which is a solvent conventionally used in photoresist compositions, has recently been pointed out as having a problem of safety, and an alternative solvent has been required. For example, JP-A-62-123444 discloses that a monooxymonocarboxylic acid ester is used as a solvent for a radiation-sensitive resin composition, and ethyl lactate contained in such a solvent has recently been used. Although it has been proposed as a highly safe solvent, the viscosity of the photoresist solution has increased, and large-diameter wafers that have recently begun to be used for LSI manufacturing have suffered from poor coating uniformity within the wafer surface, resulting in an industrial value. There is a problem that is reduced.

[0005]

The present invention is based on the premise that a high-resolution photoresist using a quinonediazidesulfonic acid ester of a low-molecular-weight novolak resin as a radiation-sensitive compound is used. An object of the present invention is to provide a photoresist that uses a solvent having no problem, has good storage stability, has appropriate viscosity, and has good coating uniformity. The present inventors have studied to achieve such an object, and as a result, have found that the intended object can be achieved by using a specific solvent.

[0006]

SUMMARY 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, wherein at least one hydroxyl group of a novolak resin having a weight-average molecular weight of 300 to 4000 is used as the radiation-sensitive compound. A photoresist composition using a partially esterified quinonediazide sulfonic acid ester and using, as a solvent, a lower alkyl ester of 3-oxypropionic acid and / or a lower alkyl ester of 3-lower alkoxypropionic acid. Exists.

Hereinafter, the present invention will be described in more detail. The base resin in the present invention is generally an alkali-soluble resin, and more specifically, a novolak resin is used. Novolak resins include phenols such as phenol, resorcinol and catechol; o-cresol,
alkylphenols such as m-cresol, p-cresol, 3-ethylphenol, 2,5-xylenol and 3,5-xylenol; 2-methoxyphenol, 4-methoxyphenol
Alkoxy or allyloxyphenols such as methoxyphenol and 4-phenoxyphenol; naphthols which may be substituted with an alkyl group such as α-naphthol, β-naphthol, 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 Formaldehyde, paraformaldehyde, aliphatic aldehydes such as acetaldehyde, aromatic aldehydes such as benzaldehyde,
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, and oxalic acid.

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

In the present invention, it is essential to use, as a radiation-sensitive compound, a quinonediazide sulfonic acid ester obtained by esterifying at least a part of hydroxyl groups of a novolak resin having a weight-average molecular weight of 300 to 4000. I do. The novolak resins having a weight average molecular weight of 300 to 4000 are novolak resins which are polycondensates of a hydroxy aromatic compound and a carbonyl compound as exemplified as the base resin, and have a weight average molecular weight of 300 to 4000. No. In such novolak resins, it is necessary that at least a part of the hydroxyl groups is esterified with a quinonediazidesulfonic acid compound. Number of sulfone groups) ×
100 / (number of hydroxyl groups per molecule of novolak resin)]
Is 35 to 90%.

The quinonediazidesulfonic acid esters include 1,2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-4-sulfonic acid ester, and 1,2-naphthoquinonediazide-5-sulfonic acid ester.
Sulfonates 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.

[0011]

Embedded image

(In the formula, R ¹ represents a lower alkyl group having 1 to 4 carbon atoms. 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 each independently Independently represents a hydrogen atom, a lower alkyl group or an aryl group having 1 to 4 carbon atoms, Q represents a hydroxyl group, l is an integer of 1 to 4, m is 0
And n is an integer of 3 to 35. )
The weight-average molecular weight of the novolak resins which are the parent of the radiation-sensitive compound is preferably from 400 to 2500.

The radiation-sensitive compound per se of the present invention, a hydroxyaromatic compound and a carbonyl compound combined presence Shimoshige condensation of an acid catalyst in accordance with a conventional known method (for example, JP-table flat 3-502010 Patent forth), resulting Novolak resin
-Naphthoquinonediazide-5-sulfonic acid chloride or the like to produce a sulfonic acid ester. In the present invention, as the solvent for the photoresist containing the radiation-sensitive compound, among the known monooxymonocarboxylic acids as the solvent for the radiation-sensitive resin composition, particularly, 3-oxypropionic acid lower alkyl ester and / or 3-lower acid It is characterized in that a lower alkyl ester of alkoxypropionic acid is used. Here, "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-methoxypropionate. 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 preferred. The photoresist composition of the present invention,
By using a lower alkyl ester of 3-oxypropionic acid and / or a lower alkyl ester of 3-lower alkoxypropionic acid as a solvent, the coating uniformity is better than, for example, ethyl lactate proposed recently.

In the present invention, a solvent obtained by mixing ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, ethyl lactate, ethyl pyruvate, xylene and the like can be used as long as the effects of the present invention are not impaired. In this case, the preferable mixing ratio is usually such that the solvent of the present invention is 50% by weight or more, preferably 70% by weight in the total 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. Furthermore, in the present invention, for example, an additive such as a surfactant for improving the coating property, a light absorbing material for reducing the influence of irregularly reflected light from the substrate, and a sensitizer for improving the sensitivity is added. You can also.

[0018]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the examples unless it exceeds the gist thereof. Examples 1-3, Comparative Examples 1-2 m-cresol, p-cresol as base resin,
A novolak resin having a weight average molecular weight shown in Table 1, produced from 2,5-xylenol and formaldehyde, and the following radiation-sensitive compounds A to E and methyl 3-methoxypropionate are mixed and dissolved in the proportions shown in Table 1. In order to further improve the coating property, a fluorine-based surfactant (trade name "Florald" FC-430 Sumitomo 3M Co., Ltd.)
Was added, and the mixture was microfiltered with a 0.2 μm Teflon filter to prepare a photoresist composition.

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

These photoresist compositions were heated and maintained at 40 ° C. for 4 weeks, and storage stability was examined. To determine the storage stability, apply the photoresist composition to a 5-inch silicon wafer and use a laser surface inspection device (LS-500).
0, manufactured by Hitachi Electronics Engineering Co., Ltd.) to determine the number of particles of 0.3 μm or more in the photoresist film. The critical 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 second to form a resist film having a thickness of 1.22 μm. This is connected to an i-line stepper (NSR1755i
7A, manufactured by Nikon Corporation, and baked on a hot plate at 110 ° C. for 90 seconds, and then 2.38
Developed with a 1% aqueous solution of tetramethylammonium hydroxy for 1 minute. The limit resolution was determined by observing with an electron microscope how far a fine pattern was resolved at an exposure amount at which a 0.6 μm test pattern was resolved to 0.6 μm on a wafer. The results are summarized in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

Example 4 The same experiment as in Example 3 was conducted except that the solvent was changed to ethyl 3-ethoxypropionate.
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 a photoresist composition was coated on an 8-inch silicon wafer at 4000 points.
When spin-coated at rpm, about 1.20
Example 1 The amount of the solvent was adjusted so that a coating thickness of μm was obtained.
A photoresist composition was prepared according to the procedure described in Example 1.

The content of the photosensitizer, the novolak resin and the solvent in the photoresist composition was determined in Example 5 by using the photosensitizer 19.
1 g, 74.7 g of novolak resin and 276.2 g of solvent
Comparative Example 3 contained 17.9 g of a photosensitizer, 69.9 g of a novolak resin, and 282.2 g of a solvent. The viscosity of this photoresist composition and 1.2 for 8-inch wafers
The coating uniformity at the time of coating to a coating thickness of 0 μm was measured. The viscosity of Example 5 was 12 cp and the coating uniformity was 34 °, and the viscosity of Comparative Example 3 was 33 cp and the coating uniformity was 124 °. The coating uniformity is a value obtained by measuring the film thickness at nine points in the resist film plane as a value of 3σ, where 3σ means a statistical probability, and the measured values are assumed to have a normal distribution. It means that 99.7% is distributed in ± 3σ value.

[0026]

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, a lower alkyl ester of 3-oxypropionic acid, especially a lower alkyl ester of 3-oxypropionic acid, among solvents known as a solvent is used. By using a lower alkyl ester of 3-or lower alkoxypropionic acid, a photoresist having good storage stability and coating uniformity and high resolution can be obtained, which is extremely useful in practice.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-56960 (JP, A) JP-A-2-254451 (JP, A) JP-A-2-96164 (JP, A) JP-A-62- 143056 (JP, A) JP-A-62-123444 (JP, A) JP-A-50-141614 (JP, A) Japanese Translation of PCT International Publication No. 3-502010 (JP, A) (58) Fields investigated (Int. ^7, DB name) G03F 7/022 G03F 7/004 G03F 7/023 H01L 21/027

Claims (4)

(57) [Claims] 1. A quinonediazide sulfonic acid in which at least a part of hydroxyl groups of a novolak resin having a weight average molecular weight of 300 to 4000 is esterified as a radiation sensitive compound in a photoresist composition containing a base resin, a radiation sensitive compound and a solvent. A photoresist composition using an esterified product and using a lower alkyl 3-oxypropionate and / or a lower alkyl 3-alkoxypropionate as a solvent. 2. The base resin having an average molecular weight of 2,000 to 3,000.
000, which is the parent of the radiation-sensitive compound
Radiation-sensitive compounds that are larger than the molecular weight of the block resin
Of quinonediazidesulfonic acid ester
2. The conversion rate is from 35 to 90%.
The photoresist composition of any of the preceding claims. 3. The method according to claim 1, wherein the solvent is methyl 3-methoxypropionate.
, Ethyl 3-methoxypropionate, 3-ethoxy
Methyl lopionate and ethyl 3-ethoxypropionate
A member selected from the group consisting of
3. The photoresist composition according to claim 1 or 2. 4. The concentration of the base resin is 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 base resin is 0.1
3. The method according to claim 1, wherein the weight is 0.5 to 0.5 times.
3. The photoresist composition according to any one of items 3.