JPS63273856A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To enhance resolution and dry etching resistance by using a resist material obtained by esterifying 2-diazonaphthoquinone-5-sulfonyl group with a specified chlorophenol novolak resin. CONSTITUTION:The resist film to be formed on a substrate is obtained by esterifying the 2-diazonaphthoquinone-5-sulfonyl group with the chlorophenol novolak resin of a polymerization degree of 3-20 obtained by condensing chlorophenol with formaldehyde, then, exposed to patternwise electron beams, and developed with an acetate or ketone type solvent as a developing solution, thus permitting the obtained resist pattern to be high in resolution and also excellent in dry etching resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of forming a resist pattern in manufacturing a semiconductor device.

(Prior Art) In recent years, demands for higher integration of semiconductor devices have become more and more severe, and advanced techniques for forming fine resist patterns are required. Exposure methods using electron beams or X-rays are effective for miniaturizing such resist patterns, especially for pattern formation at half a micron or less, but there is a need for the development of high-resolution resist materials suitable for these methods. There is.

In recent years, various techniques for dry etching substrates using a resist pattern as a mask have been adopted in the manufacture of semiconductor devices, etc., and resist materials for such methods require high dry etching resistance in addition to the above-mentioned high resolution. be done.

PMM is generally well known as a positive electron beam resist.
Although A has high resolution characteristics, it is inferior to the above-mentioned dry etching resistance, and its sensitivity to electron beams is also somewhat low.

On the other hand, chloromethylated polystyrene, which is a negative electron beam resist, has an aromatic ring in its structure and has excellent dry etching resistance as described above, and because it is a resist that utilizes gelation, its molecular weight is high. It has the characteristic that high sensitivity can be obtained by doing so.

(Problem to be Solved by the Invention) However, due to the high sensitivity of the above-mentioned negative electron beam resists, so-called whiskers and bridges are likely to occur during pattern formation, making it extremely difficult to apply the so-called quarter-micron rule to semiconductor devices. becomes difficult. The above-mentioned whiskers and bridges are thought to be mainly caused by a decrease in resist contrast and swelling of the resist, and in particular, it is presumed that the negative formation mechanism of the resist depends on gelation.

The object of the invention is to provide a method for forming a resist pattern with high resolution and excellent dry etching resistance by eliminating the problem of poor resolution in such a resist.

(Means for Solving the Problems) The present invention provides a 2-diazonaphthoquinone-5-sulfonyl group in a chlorophenol novolak resin with a degree of polymerization of 3 to 20 obtained by condensation of chlorophenol and formaldehyde, particularly as a material for pattern formation. The resist material is characterized by using a resist material formed by ester bonding.

That is, the present invention provides a film made of a resist material made by ester bonding a 2-diazonaphthoquinone-5-sulfonyl group to a chlorophenol novolac resin with a degree of polymerization of 3 to 20 obtained by condensation of chlorophenol and formaldehyde on a substrate. a step of pattern-irradiating this resist film with an electron beam; a step of developing with an acetate-based or ketone-based solvent as a developer;
This is a method of forming a resist pattern consisting of:

In this invention, the reason why the degree of polymerization of the novolac resin of the resist material is limited to 3 or more is that if the degree of polymerization is less than this, it becomes difficult to form a film of the resist, and the degree of polymerization is 20.
This is because if the molecular weight exceeds 100%, the molecular weight becomes too large and it becomes impossible to develop with an acetate-based or ketone-based solvent during subsequent development.

Next, in this invention, as the solvent for the developer, ethyl acetate, butyl acetate, isoamyl acetate, 2-methoxyethyl acetate, methyl isobutyl ketone, acetone, etc. are used. A suitable amount of cyclohexane, which is a poor solvent, can be mixed with these to form a developer, but in the case of B, it is preferable that the above acetate esters be contained in an amount of 45% by volume or more.

(Function) In the invention of Party B, the above-mentioned film-forming resist material is obtained by introducing a 2-diazonaphthoquinone-5-sulfonyl group into a chlorophenol novolak resin obtained by condensation of chlorophenol and formaldehyde through ester bonding. It is believed that the presence of the introduced groups maintains the above-mentioned high resolution and exhibits high dry etching resistance due to the presence of the introduced groups.

(Example) The present invention will be specifically explained below with reference to Examples.

Example 1 2-diazonaphthoquinone-5-sulfonic acid ester of O-chlorophenol novolac resin having a molecular weight of about 3000 was dissolved in 2-methoxyethyl acetate to prepare a 25 wt % solution. This was filtered through a membrane filter with 0.2 .mu.m holes, transferred onto a silicon substrate, and baked on a hot plate at 80.degree. C. for 1 minute to obtain a 0.7 .mu.m thick resist film.

Next, an electron beam with an acceleration voltage of 20 KV was selectively irradiated with varying doses to draw a plurality of sets of 20 lines of 1 μm at a pitch of 2 μm. The film was developed with a mixed solvent of 2-methoxyethyl acetate/isoamyl #acid 70/30 for 60 seconds, and rinsed with cyclohexane for 10 seconds. From the curve in which the film thickness of the obtained pattern was normalized by the initial film thickness and plotted against the above dose, the sensitivity was 7.1 μC/cl.
It turned out to be lr.

Next, the resist contrast (γ value) was evaluated and found to be 0.7.

In the same manner as above, various patterns were drawn at a dose of 8.5 μC/Cd, and their resolution was observed using a scanning electron microscope (SEM). It was observed that an isolated space of .6 μm was resolved.

Example 2 After forming a resist film and performing electron beam drawing in exactly the same manner as in Example 1, development was performed with 2-methoxyethyl acetate, and the sensitivity was also 12 μc/crl.

γ-0.9. Furthermore, lines with a resolution of 0.5 μm were resolved at a pitch of 1.0 μm, and isolated spaces of 0.5 μm were resolved.

Example 3 Molecules] Approximately 2,500 2-diazonaphthoquinone-5-sulfonic acid esters of p-chlorophenol novolak resin were dissolved in 2-methoxyethyl acetate to form a 25 wt/% solution. This was filtered through a Membrane filter with 0.2 μm pores to obtain a resist solution.

Thereafter, in the same manner as in Example 1, a 0.7 μm thick resist film was formed on the substrate, and the electron beam sensitivity was determined.

The developer used is isoamyl acetate/cyclohexane 55/4.
I gave it a 5. D, =27.5μclcsp&, γ=1.
5. The resolution was 0.4 μm lines at a 0.8 μm pitch and 0.4 μm isolated spaces.

Example 4 A resist film formed in the same manner as in Example 3 above was subjected to electron beam lithography to obtain isoamyl acetate/cyclohexane 4.5155
When developed with D: 5-12μc/cd1γ
A result of =1.0 was obtained. Also, set the 0.3pm line to 0.
．． Group images were captured at a pitch of 7 μm and isolated spaces of 0.3 μm.

Comparative Example 1 In Example 1, 2. Except for using the IT body, the above spin code was performed using the same resist solution and prebaking was performed, but at that time cracks occurred in the film and it could not be used. We also attempted to develop a resist film made of 2-diazonaphthoquinone-5-sulfonic acid ester of novolak resin with a molecular weight of about 3500 (N content of about 21) after exposing it to electron beam in the same way, but it was difficult to develop it after exposing it to an electron beam. No patterning was possible with methoxyethyl or the like.

Example 5 A resist film obtained in the same manner as in Example 3 was subjected to electron beam drawing,
When developed with methyl ethyl ketone/cyclohexane 45155, D′,”=19 p c /eIlr,
It was 7-1.2. The resolution was 0.4 μm lines with a total pitch of 0.8 μm, and isolated spaces of 0.5 μm were resolved.

Comparative Example 2 The dry etching resistance of the material used in the present invention was compared with AZ-1350J 1PMMA, a conventional resist material. Dry etching resistance was determined using a parallel plate dry etcher, with an RF power density of 0, 08 W/c/,
O□ Gas pressure-flow rate: 50 Pa-20 SCCM.

The amount of etching of the material used in the present invention is 1/2 that of PMMA.
AZ-1350 has excellent dry etching resistance.
It was almost equivalent to J.

(Effects of the Invention) As explained above, in this invention, by using 2-diazonaphthoquinone-5-sulfonic acid ester of chlorophenol novolac resin with a degree of polymerization of 3 to 20 as a resist material, the minimum 0.3μ
It is possible to form a fine pattern with a maximum sensitivity of 7.1 μc/cnf.

Furthermore, since the resist of the present invention contains a large number of aromatic rings in its structure, it exhibits dry etching resistance comparable to that of general positive photoresists, and therefore microfabrication of substrates is possible using the resist of the present invention. This is an effect that can be expected to be applied to the production of highly integrated semiconductor devices.

Claims (2)

[Claims] (1) On a substrate, a chlorophenol novolac resin with a degree of polymerization of 3 to 20 obtained by condensation of chlorophenol and formaldehyde is coated with 2-diazonaphthoquinone-5-
The process consists of the following steps: forming a film using a resist material in which sulfonyl groups are ester-bonded; pattern-irradiating the resist film with an electron beam; and developing the resist film using an acetate-based or ketone-based solvent as a developer. How to form a resist pattern. (2) The above-mentioned developer is either a mixed solvent with a poor solvent containing at least 45% of an acetate-based or ketone-based solvent, or a single solvent of an acetate-based or ketone-based solvent (1). ) The method for forming a resist pattern described in section 2.