JPH04338959A - Pattern forming method - Google Patents

Abstract

PURPOSE:To improve the cross-sectional form of the resist pattern high in resolution. CONSTITUTION:When a substrate 1 is coated with a resist thin film, the resist coating surface of the substrate 1 is processed with an acid, so that a phenomenon that the part of the hem of the resist pattern is bitten is prevented when a chemical amplifying negative type resist 3 is used, and a highly accurate resist pattern 5 is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a resist pattern used in the manufacture of high-density integrated circuits such as LSIs and VLSIs, and more particularly to a method of forming highly accurate resist patterns.

0002

[Prior Art] Semiconductor integrated circuits such as ICs, LSIs, and VLSIs are manufactured by applying a resist onto a substrate to be processed such as a silicone wafer, exposing a desired pattern using a stepper, etc., and then performing so-called lithography such as development and etching. It is manufactured by repeating the process.

Resists used in such lithography processes are increasingly required to have higher precision as semiconductor integrated circuits become more sophisticated and highly integrated. For example, a 1M bit DRAM has a diameter of 1.2μm, and a 4Mbit DRAM has a diameter of 0.5μm.
With the demand for further miniaturization of 8 μm, 0.6 μm for 16 Mbit DRAM, and 0.35 μm for 64 Mbit DRAM, various resists are being actively researched.

[0004] In general, resist materials used in ultrafine lithography using a high-energy radiation source are required to have the following properties. (b) High sensitivity. (b) Must be of high resolution. (c) It is possible to form a homogeneous thin film. (d) Excellent dry etching resistance because dry etching is applied, which is essential for high-density, fine patterning. (e) Excellent developability.

Conventionally developed negative resists include CMS and PGMA. This resist has a polymerizable functional group such as an epoxy group in its side chain, and undergoes a crosslinking reaction when irradiated with ionizing radiation.

[0006] Recently, a chemically amplified negative resist consisting of three components: an acid generator, a crosslinking agent, and a novolac resin has been developed. As shown in FIG. 3, acid 33 is generated from acid generator 32 by irradiation with ionizing radiation 31, and by applying heat 34, acid 33 acts as a catalyst for the crosslinking reaction between crosslinking agent 35 and novolak resin 36. It is known for its high sensitivity. It also has excellent resolution and dry etching resistance.

However, at present, a resist that satisfies all characteristics such as sensitivity, resolution, adhesion, stability, and dry etching resistance has not been obtained.

[0008]

[Problems to be Solved by the Invention] In order to form fine, high-precision patterns such as those used in manufacturing highly integrated LSIs, vertical resist patterns have been indispensable. It was also particularly important when patterning by dry etching. however,
With current resists, it is quite difficult to form a pattern with a cross-sectional shape perpendicular to the substrate surface.

Particularly in chemically amplified resists, FIG.
When a pattern is formed as shown in FIG. 1, a cut-in portion 43 occurs at the interface between the substrate 41 and the resist 42, and if wet etching or the like is performed as it is, the cross-sectional shape of the pattern on the silicon, chrome, etc. substrate to be processed will be trapezoidal. Furthermore, there was a problem that the adhesion of the resist was poor and the pattern line width became considerably thin.

0010

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems in forming a highly accurate resist pattern, and aims to improve the interface between the substrate and the resist by treating the substrate with acid. The purpose is to improve adhesion and provide highly accurate resist patterns.

As a result of research into a pattern forming method that enables ultra-fine lithography, the present invention has developed a method of treating the substrate surface with an acid or an acid generator to increase the crosslinking density on the substrate surface before applying the resist. This is a method of forming a resist pattern having a cross-sectional shape perpendicular to the substrate surface.

In the above-mentioned chemically amplified negative resist, the phenomenon in which the bottom portion of the resist digs in at the interface between the resist and the substrate is caused by the low crosslinking density near the substrate despite being exposed to light. This is thought to be because it is dissolved by the liquid. The cause of the decrease in crosslink density is
Although it is not certain, the following may be considered. (1) The distribution of the acid generator in the resist is uneven. (2) The generated acid reacts with the substrate surface and is consumed. Based on the above considerations, acid treatment of the substrate surface was adopted as a means to solve this problem.

FIG. 1 shows the steps of the pattern forming method of the present invention. When a substrate 1 is treated with an acid (a), the surface of the substrate becomes rich in protons 2 (b). A resist 3 is applied to the proton-rich substrate (c), and then a series of photolithography steps such as exposure, post-bake, and development are performed to obtain a resist 4 with scum (d). remove the
A desired resist pattern 5 is obtained (e).

In the method of the present invention, protons, that is, acids on the substrate surface act as catalysts for the crosslinking reaction of the resist in the vicinity of the substrate, and the crosslinking density of the resist can be increased particularly in the vicinity of the substrate. It is possible to prevent the resist from digging into the vicinity of the substrate as seen in .

On the other hand, in the treatment using an acid generator, an acid is generated by irradiation with ionizing radiation during the exposure process, and the same effect as the treatment with an acid is obtained.

The substrate to which the present invention can be applied can be made of many materials such as metal, ceramic, glass, and synthetic resin, but in particular, the surface on which the resist pattern is to be formed is made of silicon, silicon oxide, etc. Suitable for semiconductor device wafers and photomask substrates made of films, silicon nitride films, aluminum, polysilicon, glass, chromium, tungsten, chromium oxide, chromium nitride, molybdenum, molybdenum silicide, etc., and phase shifters such as SOG. .

Further, as the resist to which the method of the present invention is applied, a chemically amplified negative type resist is preferable. These resists include chemically amplified resists SAL-601 and XP8843 manufactured by Shipley, and RA manufactured by Hoechst.
There are Y-PN, etc.

To explain the acid treatment method of the present invention, examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, hydrofluoric acid, or a mixed acid thereof. Further, as the acid generator, orthodiazonaphthoquinone derivatives, trichloromethyl-s-triazine derivatives, halogenated phenols, and onium salts are used.

The treatment method using an acid or an acid generator may be carried out by immersion in a solution of the acid or an acid generator, an application method using a brush or the like, a spray method, etc., or by spin coating or Langmuir blowing on the surface of the substrate. A cumulative film of acid or acid generator may be formed by a jet method. Further, the temperature for treatment with an acid or an acid generator is suitably 5°C to 80°C.

After the treatment with the acid or acid generator, excess acid is removed from the substrate surface by rinsing with pure water, high pressure cleaning, or scrub cleaning.

[0021]

[Action] By treating the substrate with acid or an acid generator, the crosslinking density near the substrate of the resist using the acid generator is increased, and the bottom part of the resist is perpendicular to the substrate and can dig into the inside of the resist. It is possible to form a resist pattern with no resist pattern.

[0022]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1 A photomask substrate consisting of a two-layer film of chromium and low-reflection chromium was immersed in 1N hydrochloric acid at a temperature of 21° C. for 5 minutes, washed with pure water, spin-dried, and made into a proton-rich film. I got the board.

A resist solution of XP-8843 manufactured by Shipley Co., Ltd., which is a chemically amplified negative type resist, was spin-coated on this photomask substrate and prebaked at 120° C. for 30 minutes to form a uniform resist film with a thickness of 0.5 μm. Obtained.

[0025] This was subjected to pattern exposure at an irradiation dose of 1.5 μC/cm 2 using an electron beam exposure device with an accelerating voltage of 10 kV. After exposure, use MF manufactured by Shipley, which is an alkaline aqueous solution containing tetramethylammonium hydroxide as a main component.
321 for 2 minutes and rinsed with pure water to obtain a resist pattern. After that, descum treatment was performed to remove scum.

When the cross-sectional shape of the obtained resist pattern was observed with a scanning electron microscope, a resist pattern 22 was obtained that was perpendicular to the surface of the substrate 21, as shown in FIG. 2(a).

Example 2 A photomask substrate consisting of a two-layer film of chromium and low-reflection chromium was placed in a 1M solution of orthodiazonaphthoquinone, an acid generator, dissolved in cellusolve acetate at a temperature of 2.
After soaking at 1° C. for 5 minutes, spin drying was performed.

A resist solution of XP-8843 manufactured by Shipley Co., Ltd., which is a chemically amplified negative resist, was spin-coated on this photomask substrate, and prebaked at 120° C. for 30 minutes to obtain a uniform resist film with a thickness of 0.5 μm. .

This was subjected to pattern exposure at an irradiation dose of 1.5 μC/cm 2 using an electron beam exposure device with an accelerating voltage of 10 kV. After exposure, use MF manufactured by Shipley, which is an alkaline aqueous solution containing tetramethylammonium hydroxide as a main component.
321 for 2 minutes and rinsed with pure water to obtain a resist pattern. In this case no scum was formed. As in Example 1, a vertical resist pattern was obtained by the acid generator treatment. Comparative Example 1 A resist pattern was formed in the same manner as in Example 1, except that the substrate was not treated with hydrochloric acid. occured.

[0030]

[Effects of the Invention] When forming a resist pattern, by treating the resist-coated surface of the substrate with an acid or an acid generator before applying the resist, the hem of the resist digs into the inside, resulting in the formation of the pattern. It becomes possible to prevent accuracy from decreasing.

[Brief explanation of drawings]

FIG. 1 shows the process of forming a resist pattern in the method of the present invention.

FIG. 2 shows cross-sectional views of resist patterns obtained in Examples and Comparative Examples.

FIG. 3 shows the mechanism of chemically amplified negative resist.

FIG. 4 shows a cross-sectional shape of a conventional chemically amplified resist pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Substrate, 2...Proton, 3...Resist, 4...Resist with scum, 5...Resist pattern, 21...Substrate,
22... Resist pattern, 23... Biting portion, 31... Ionizing radiation, 32... Acid generator, 33... Acid, 34... Heat, 35
...Crosslinking agent, 36...Novolac resin, 41...Substrate, 42...
Resist, 43... biting part

Claims (6)

[Claims] 1. A method for forming a pattern of a chemically amplified negative resist on a substrate, the method comprising treating the surface of the substrate with an acid or an acid generator before applying the resist. 2. The pattern forming method according to claim 1, wherein the substrate is SOG or sputtered SiO2, which is a shifter material in a phase shift mask. 3. The pattern forming method according to claim 1, wherein the acid is selected from hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, acetic acid, formic acid, and mixed acids thereof. 4. The pattern forming method according to claim 1, wherein the acid generator is orthodiazonaphthoquinone. 5. Any one of claims 1 to 4, characterized in that the treatment with the acid or acid generator is carried out by immersing, coating, or spraying the substrate in the acid or acid generator solution. The pattern forming method described in . 6. The pattern forming method according to claim 1, wherein the treatment with an acid or an acid generator is accumulated on the substrate surface by a Langmuir-Blodgett method.