JPH01277234A - Resist - Google Patents

Abstract

PURPOSE:To ensure faithful transfer of a pattern to a substrate, etc., by using novolak resin obtd. by condensing isopropenylphenol and other phenol deriv. with a carbonyl compd. as an alkali-soluble resin. CONSTITUTION:Novolak resin contg. structure units of isopropenylphenol which clears the profile of a pattern, increases the mol.wt. and improves the heat resistance is used as an alkali-soluble resin for a resist. The novolak resin further contains structural units of xylenol having high heat resistance and/or structural units of cresol which clears the profile of a pattern. Novolak resin obtd. by condensing m-isopropenylphenol, m-cresol and 3,5-xylenol with a carbonyl compd. can remarkably improve the characteristics of a resist because it has superior heat resistance and resolving power and can extremely clear the profile of a pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a resist useful for forming fine resist patterns.

(Prior Art) Resists are widely used in the field of flat plate processes, including the manufacture of semiconductor devices such as LSIs. In particular, in order to increase the density of electronic devices as they become more multi-functional and sophisticated, resist patterns are becoming finer and heat resistance is required for reactive ion etching (RIE), which is widely used as a recent etching method. is required.

In response to the above-mentioned requirements, resists with excellent heat resistance and resolution have been proposed, for example, in JP-A-81-185741 and JP-A-81-184740. However, using such resists, particularly fine (e.g. 0.7
When a pattern (micrometer or less) is formed, there is a problem in that the pattern profile is poor and it is difficult to faithfully transfer the pattern (draetching process) onto a semiconductor substrate or the like.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and it not only has excellent sensitivity, heat resistance, and resolution, but also has fine (0.7 μm or less) To provide a resist which has a good pattern profile even during pattern formation (2), and which enables faithful pattern transfer (etching) to the substrate, etc. when dry etching the substrate, etc. using such a pattern as a mask. It is.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a resist comprising an alkali-soluble resin and a photosensitizer, wherein the alkali-soluble resin is a novolac resin obtained by condensing isopropenylphenol and a phenol derivative with a carbonyl compound. This is a resist characterized by containing.

The above-mentioned isopropenylphenol includes 0-isopropenylphenol, m-isopropenylphenol, p-isopropenylphenol,
-There is isopropenylphenol. Among them, m-isopropenylphenol is suitable because it has excellent reproducibility in the condensation reaction.

The above-mentioned phenol derivatives are not particularly limited as long as they condense with carbonyl compounds, and include, for example, cresol, xyresol, ethylphenol, propylphenol, butylphenol, dihydroxybenzene, trihydroxybenzene, naphthol, polyvinylphenol derivatives, etc. can. Among these phenol derivatives, cresol and xyresol are particularly preferred.

This cresol includes 0-cresol, m-cresol, and p-cresol, among which m-cresol has the effect of improving the pattern profile, and p-cresol has the effect of increasing the molecular weight and improving heat resistance. Therefore, it is desirable to select these depending on the purpose of use of the resist.

In addition, as xyresol, 3,5-xyresol, 2
．． 5-xyresol is preferred, and 3.5-xyresol is particularly effective in improving the pattern profile and improving heat resistance.

Examples of the carbonyl compound include formaldehyde, acetaldehyde, acetone, benzaldehyde,
Examples include benzylaldehyde.

The composition ratio of each structural unit in the above novolak resin can basically take any value, but usually the isopropenylphenol structural unit is 5 to 50 mol%, the cresol structural unit is 10 to 50 mol%, and It is desirable that the xyresol constituent unit is 15 to 70 mol%.

The reason for this is that if the composition ratio of each structural unit deviates from the above range, there is a risk of a decrease in resolution and sensitivity.

The molecular weight of the above novolak resin is 1X103 to 5X10
5, more preferably in the range of 3x103 to 1x105. The reason for this is that if the molecular weight of the novolac resin is less than 1 x 103, the heat resistance may decrease, but if the molecular weight exceeds 5 x 105, it will be difficult to remove the novolac resin from the reaction vessel after synthesis. It is.

Among the above structural units, a combination of m-isopropenylphenol, m-cresol and 3.5-xyresol,
A novolak resin obtained by condensing these with a carbonyl compound has excellent properties such as both heat resistance and resolution, so the novolak resin itself can constitute an alkali-soluble resin. The composition ratio of each structural unit in such a novolac resin is usually 10 to 40 mol% of the m-isopropenylphenol structural unit, 10 to 40 mol% of the 3,5-xyresol structural unit, and the remainder m-cresol. It is desirable that there be. The reason for this is that if the composition ratio of each structural unit deviates from the above range, there is a risk of a decrease in resolution and sensitivity. In addition, regarding the molecular weight of such novolac resin, as mentioned above, lX1
03~5X105, more preferably 3X103~1x1
A range of 0.05 is desirable.

The alkali-soluble resin may have a composition in which a polymer containing an aryl group or a carboxyl group into which a hydroxy group has been introduced is mixed in addition to the above-mentioned novolak resin. Examples of such polymers include phenol novolac resins, cresol novolac resins, xyresol novolac resins, vinyl phenol resins, isopropenyl phenol resins, copolymers of vinyl phenol with acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives, etc. Copolymers of isopropenylphenol and acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives, acrylic resins, methacrylic resins,
Examples include copolymers of acrylic acid or methacrylic acid and acrylonitrile and styrene derivatives, and copolymers of malonic acid and vinyl ether. Moreover, the polymer containing silicon can also be used. The amount of the above-mentioned novolak resin contained in these alkali-soluble resins is
It is desirable that the content be at least 10% by weight or more, preferably in the range of 40 to 90% by weight. Of course, the novolac resin alone may be used as the alkali-soluble resin.

As the above-mentioned photosensitizer, either a positive type or a negative type can be used. Examples of such photosensitizers include p-quinonediazides such as β-naphthylamide of p-benzoquinonediazide sulfonic acid, p-quinonediazides such as β-naphthylamide of p-benzoquinonediazide sulfonic acid, p-
-Iminoquinone diazides, British Patent No. 1110017
organic solvent-soluble condensation products of diazonium salts and formaldehyde, p-diazodiphenylamine salts, and co-condensation products of 4,4-bismethoxymethyldiphenyl ether and formaldehyde described in the specification of this patent and French Patent No. 2,022,413. Aromatic diazonium salts such as condensation products and copolymerization products of formaldehyde with other aromatic products and British Patent No. 7458
Mention may be made of aromatic azides such as the azide compounds described in No. 88. However, low-molecular diazonium salts, diazosulfonic acid salts of aromatic and heterocyclic amines, quinone diazides, polymer products having diazo groups, azide groups, or other photosensitive groups, and polyethylene oxide are polyvinylphenol. Organic halogen compounds such as bromoform may be used if used in a mixture with bromoform. Among these photosensitizers, 0-quinonediazides such as aromatic esters or amides of 0-naphthoquinonediazide sulfonic acid or 0-naphthoquinonediazidecarboxylic acid are particularly preferred, and specifically 2.3.4-trihydroxy 1.2 of benzophenone
- Naphthoquinonediazide sulfonic acid esters and 2.3
．． 4.1 of 4'-tetrahydroxybenzophenone.
Most preferred are 2-naphthoquinonediazide sulfonic acid esters.

Among 2Fl suitable as the above-mentioned photosensitizer, the latter is preferable because it can improve the heat resistance of the resist. It takes 2
, 2.3.4.4'-tetrahydroxybenzophenone-1,2-naphthoquinonediazide-5-sulfonic acid ester among the 1,2-naphthoquinonediazide sulfonic acid esters of 3,4.4'-tetrahydroxybenzophenone. is generally suitable as a photosensitizer for g-line exposure,
2.3.4.4'-Tetrahydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester is suitable as a photosensitizer for exposure to shorter wavelength ultraviolet rays. In addition, in these photosensitizers, the esterification rate of 2,3.4.4'-tetrahydroxybenzophenone with 1,2-naphthoquinonediazide sulfonic acid is 2.3
．． It is desirable that the total number of hydroxyl groups in 4.4'-tetrahydroxybenzophenone be 40 to 100%. For example, the number of naphthoquinone diazide introduced is 2, 3, 4, 4.
'-Tetrahydroxybenzophenone shows an average of 1.8 to 4 per molecule, generally 1,2.8.4
It is a mixture of tetrahydroxybenzophenones having an incorporation number of .

The amount of the photosensitive agent to be blended with the alkali-soluble resin containing the novolak resin varies depending on the type of each constituent unit of the novolac resin mentioned above and the composition of the alkali-soluble resin, and although it cannot be generally limited, it is usually The agent is 5 to 30% by weight based on the total amount of alkali-soluble resin.
It is desirable to mix them. The reason for this is that if the amount of the photosensitizer exceeds the above range, the resist resolution, heat resistance,
This is because there is a possibility that either the adhesion to the substrate or the like, the sensitivity, etc. will be significantly reduced.

Each resist according to the present invention further includes an ultraviolet absorber, a sensitizer, a stabilizer for storage stability, an antihalation agent to prevent halation from the substrate, and adhesion to the substrate, as necessary. Adhesion improvers to improve coating properties, surfactants to smooth the coating surface, or other polymers to improve solubility and coating coatings, such as epoxy resins, polymethyl methacrylate resins, and polyesters. It is also possible to blend methyl acrylate resin, propylene oxide-ethylene oxide copolymer, polyvinylphenol, polystyrene, etc.

Each resist according to the present invention is applied onto a predetermined substrate in a state dissolved in a solvent. Examples of such solvents include cellosolve acetate alone such as ethyl cellosolve acetate and butyl cellosolve acetate, or ethyl cellosolve acetate, butyl cellosolve acetate,
A mixed solution of two or more selected from ethyl cellosolve and methyl cellosolve is suitable. However, these may contain an appropriate amount of xylene, toluene, butyl acetate, γ-butyl alcohol, dimethylformamide, or an aliphatic alcohol such as isopropyl alcohol, and may further contain a trace amount of a surfactant.

Next, a process for forming a resist pattern using the resist of the present invention will be explained.

First, the above-mentioned novolac resin and photosensitizer are included on the substrate,
The resist solution of the present invention dissolved in the organic solvent is applied by a spin coating method or a dipping method, and then dried at 150° C. or lower, preferably 70 to 120° C. to form a resist film. Examples of the substrate used here include a single silicon single crystal wafer, the same wafer with various coatings such as an insulating film and a conductive film deposited on its surface, or a mask blank.

Next, the resist film is exposed. Ultraviolet light is usually used as this exposure light source. However, when used as a negative resist, short wavelength ultraviolet rays, electron beams, X-rays, etc. can be used.

Subsequently, after baking at 110° C. for about 1 minute, the resist film is developed with an alkaline aqueous solution to form a desired resist pattern.

Examples of the alkaline aqueous solution used here include a tetramethylammonium hydroxide aqueous solution and a choline aqueous solution.

(Function) The resist of the present invention has a good pattern profile as a novolak resin that constitutes an alkali-soluble resin, and
In addition, since it contains isopropenylphenol as a structural unit, which increases the molecular weight and improves heat resistance, it has superior properties compared to ordinary novolak resists. Moreover, even more excellent characteristics can be exhibited by including a xyresol structural unit with high heat resistance and/or a cresol structural unit that improves the pattern profile in the novolac resin. In particular, m-isopropenylphenol and m-
Novolak resin, which is a combination of cresol and 3.5-xyresol and condensed with a carbonyl compound, has excellent both heat resistance and resolution, and can also have a very good pattern profile, significantly improving resist properties. can. In addition, by incorporating specific photosensitizers such as naphthoquinonediazide sulfonic acid ester of 2.3.4.4'-tetrahydroxybenzophenone, it is possible to create an excellent resist that can resolve patterns with dimensions close to the wavelength of the exposure ultraviolet light. is obtained. Therefore, by coating such a resist on a substrate to form a resist film, exposing it to light, and developing it, a fine resist pattern having a good pattern profile and excellent heat resistance due to the excellent properties of the resist can be obtained. By dry etching the substrate, etc. using the resist pattern as an etching mask, the pattern can be faithfully transferred and etched onto the substrate, etc., without causing any sag.

(Example) Examples of the present invention will be described in detail below.

[Synthesis Example After adding oxalic acid as an acid catalyst to an aqueous coformin solution and mixing, add isopropenylphenol monomer, xyresol monomer, and cresol monomer in the proportions shown in Table 1 listed below to this mixed solution, Six types of novolac resins were synthesized by heating. The molecular weights of these novolak resins are also listed in Table 1.

[Resist Solution Preparation Example] As shown in Table 2 below, the novolak resin and photosensitizer synthesized in the synthesis example above were mixed in the proportions shown in Table 2, and dissolved in ethyl cellosolve acetate. Eight types of resist solutions were prepared.

[Examples 1 to 8] First, eight types of resist solutions shown in Table 2 prepared in the above preparation examples were applied onto a hydrophilized silicon wafer by a spin code method to form a 1.5 μm thick resist solution. A resist film was formed. Subsequently, these resist films were baked at 90° C. for 5 minutes, and then pattern exposure was performed using a g-line stepper with N and A of 0.45. Then 11
After baking at 0° C. for 1 minute, each resist film was spray developed with a 2.38% aqueous tetramethylammonium hydroxide solution to form a resist pattern.

For the resist patterns formed in Examples 1 to 8, the deformation temperature (heat resistance) when heated on a hot plate, the sensitivity (evaluated by the optimum exposure amount), the resolution at the optimum exposure amount, and I looked at the pattern profile. The results are shown in Table 3 below. In addition, in Tables 1 to 3, as Comparative Example 1.2, the resist composition of a normal novolak resist and the heat resistance, sensitivity, resolution, and pattern profile of the formed resist pattern are also listed.

As is clear from Table 3 below, the resists of Examples 1 to 8 have excellent sensitivity, resolution, and heat resistance equivalent to or better than the resists of Comparative Example 1. It can be seen that a resist pattern with an excellent pattern profile can be formed by comparison.

[Effects of the Invention] As detailed above, the present invention not only has excellent sensitivity, resolution, and heat resistance, but also has a good pattern profile when forming a fine pattern, and allows the formed resist pattern to be When dry etching a substrate, etc. as an etching mask, it is possible to perform faithful pattern transfer (etching processing) to the substrate, etc., and it can be effectively used in the photoetching process for manufacturing highly integrated semiconductor devices, etc. We can provide resist.

Claims (4)

[Claims] (1) A resist containing an alkali-soluble resin and a photosensitizer, wherein the alkali-soluble resin contains a novolac resin obtained by condensing isopropenylphenol and a phenol derivative with a carbonyl compound. (2) The resist according to claim 1, wherein the alkali-soluble resin contains a novolak resin obtained by condensing m-isopropenylphenol and cresol and/or xyresol with a carbonyl compound. (3) The resist according to claim 1, wherein the alkali-soluble resin is a novolac resin obtained by condensing m-isopropenylphenol, m-cresol, and 3,5-xyresol with a carbonyl compound. (4) A claim characterized in that the photosensitizer is a naphthoquinonediazide sulfonic acid ester of 2,3,4,4'-tetrahydroxybenzophenone or a naphthoquinonediazide sulfonic acid ester of 2,3,4-trihydroxybenzophenone. Items 1 to 3. The resist according to any one of items 1 to 3.