JPH0794477A - Dry etching method - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to improve the etching resistance of a resist and realize a high resolution in a lithography process using a multilayer resist and an etching process of an LSI process. According to the present invention, by irradiating a resist pattern made of a silicon-containing material after exposure and development with ionizing radiation to break the bonds of silicon atoms in the resist, oxygen gas or its ions, radicals and plasma can be formed. It is characterized by enhancing reactivity, promoting oxidation, and improving resistance to subsequent dry etching. [Effect] Since the dry etching resistance of the resist is improved in the dry etching used in the steps of etching and plasma development, a fine pattern having higher resolution and higher aspect ratio than the conventional etching method can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing technique, and more particularly to a dry etching method used in plasma development and etching processes in a lithography process.

[0002]

2. Description of the Related Art With the high integration of LSIs, quarter-micron order fine processing is required in the current semiconductor element manufacturing process. In the lithography process, in order to obtain a resist pattern with high throughput and a high aspect ratio, a method of using a multi-layer resist, patterning the upper layer by exposure and development, and then transferring the pattern to the lower layer by dry etching is drawing attention. . As such a tendency progresses, development of a substance having high dry etching resistance as an upper layer resist material has become an important issue.

When oxygen-reactive ion etching is performed using a resist material containing silicon or a metal element, the silicon or metal in the resist is oxidized by oxygen used as an etching gas and is not etched, so that the lower layer is masked. There are things that work as. In particular, materials containing silicon are often used because they do not have the problem of contamination.
Patterning bilayer resists using silicon-containing resists is described, for example, in Journal of Vacuum Science Technology B3 (1985) pp. 306-309.

[0004]

In the silicon-containing resist material described above, the higher the silicon content, the higher the dry etching resistance. However, the higher the silicon content, the lower the exposure sensitivity and the development sensitivity, and the more difficult the ashing is. Therefore, it is necessary to further improve the dry etching resistance without increasing the silicon content.

[0005]

In a silicon-containing resist, oxidized silicon in the resist has high dry etch resistance. For example, when oxygen reactive ion etching is performed on a resist using a silicon-containing polymer represented by polysilane, the reactive species of oxygen gas plasma used as an etching gas collide with the surface of the resist material. Then, the collision oxygen breaks the interatomic bond in the resist and causes the oxidation of silicon in the resist with a certain probability to generate SiO _x . Si
O _x is a substance that is difficult to evaporate, and further, it is difficult to decompose even when it is impacted by oxygen ions.

However, the remaining silicon atoms in the resist are released together with the surrounding atoms without being oxidized. That is, if the oxidation efficiency of silicon atoms in the resist is low, the dry etching resistance is low. Therefore, the dry etching resistance of the conventional silicon-containing resist can be improved by increasing the reactivity of silicon atoms in the resist and increasing the oxidation efficiency. It has
It is effective to increase the reactivity with oxygen by preliminarily breaking the bonds between atoms before exposing it to an oxygen atmosphere. The above-mentioned object is achieved by irradiating with ionizing radiation having energy necessary for exciting valence electrons or core electrons involved in the bonding of silicon atoms.

[0007]

As shown in FIGS. 1 (a) and 1 (b), when the silicon-containing polymer 1 is irradiated with ionizing radiation 3 having a high energy such as soft X-rays before oxygen reactive ion etching, the polymer is The bond of the silicon atom 3 therein is broken, and a highly reactive dangling bond 4 is generated. If oxygen reactive ion etching is performed in such a state, as shown in FIG.
As shown in (c) and (d), most of the silicon atoms are oxidized, so compared with the case where no ionizing radiation is applied,
The dry etching resistance is improved.

[0008]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, reference numeral 7 is a pattern of the upper layer resist produced by exposure and development. In this example, a polydimethylsilane / polystyrene copolymer was used as the upper layer resist material. Further, the patterning of the upper layer resist material was performed by using an X-ray reduction lithography technique. 8 is a lower layer resist, which is 200 ° C. in this embodiment.
A novolac resin having a film thickness of 2 μm, which was baked at 20 ° C. for 20 minutes, was used. 9 is a silicon substrate, 10 is a wavelength from 4.5 nm to 2
Soft X-ray with intensity of 0.1 W / cm ² at 0 nm, 11 is soft X-ray
The upper-layer resist pattern in which the Si-Si bonds have been broken by the line irradiation, 12 is a plasma of oxygen gas, 13 is a resist pattern containing silicon oxide, and 14 is a patterned lower-layer resist.

First, after depositing a two-layer resist film as shown in FIG. 2A, a soft X-ray 10 is applied to the entire surface of the substrate 9 having the upper layer patterned for 5 seconds as shown in FIG. 2B. Irradiated. As a result, the bond of silicon atoms contained in the upper layer resist was broken, and the resist pattern 7 became a resist pattern 11 having high reactivity. After that, Figure 2
As a result of performing oxygen reactive ion etching as shown in (c), ions and radicals in the oxygen plasma 12 react with silicon in the resist to form a resist pattern 13 containing silicon oxide, and an upper layer is formed on the lower layer resist 8. The resist pattern was transferred. After performing sufficient oxygen-reactive ion etching, a novolac resin pattern 14 having a high aspect ratio was obtained as shown in FIG.

The wavelength of 300 nm is used instead of the soft X-ray 10.
The use of the following ultraviolet rays or vacuum ultraviolet rays also cut the bonds of silicon atoms and obtained the same effect.

[0012]

The dry etching resistance of the resist is improved. As a result, it is possible to reduce the cost in the semiconductor process and improve the resolution and the throughput. This method is also clean and does not damage the substrate because it does not use gas, plasma, ions, etc. further,
Since it is a dry process, it is compatible with vacuum consistency.

[Brief description of drawings]

FIG. 1 shows a silicon-containing polymer material represented by polysilane in which a bond of a silicon atom is cleaved using the present invention.
It is a conceptual diagram of the reaction at the time of performing oxygen reactive ion etching.

FIG. 2 is a conceptual diagram of a dry etching method according to the present invention, which shows a process of transferring a pattern of an upper layer resist to a lower layer resist by oxygen reactive ion etching to form a pattern having a high aspect ratio.

[Explanation of symbols]

1: Silicon-containing polymer material such as polysilane, 2: Silicon atom, 3: Ionizing radiation, 4: Silicon dangling bond, 5: Oxygen gas plasma, 6: Oxidized silicon-containing polymer material, 7: Upper layer Resist pattern,
8: Lower layer resist, 9: Silicon substrate, 10: Soft X-ray with wavelength of 4.5 nm to 20 nm and intensity of 0.1 W / cm ² , 11: Pattern of upper layer resist in which bond of silicon atom is broken, 12: Oxygen gas plasma, 13: pattern of oxidized upper layer resist, 14: pattern formed on lower layer resist by reactive ion etching.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taro Ogawa 1-280 Higashi Koikekubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Takashi Soga 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Eiji Takeda 1-280, Higashi Koikekubo, Kokubunji, Tokyo Central Research Laboratory, Hitachi, Ltd. (72) Inventor Hiroaki Tachibana 1-1, East Higashi, Tsukuba-shi, Ibaraki Industrial Technology Research Institute In-house (72) Inventor Mutsura Matsumoto, 1-1, Higashi 1-1 Tsukuba, Ibaraki Prefecture Institute of Industrial Science and Technology

Claims (3)

[Claims] 1. A desired pattern is formed on a silicon-containing resist film, and the resist pattern is used as a mask.
In the dry etching method for processing the lower layer resist or substrate by oxygen reactive ion etching, prior to oxygen reactive ion etching, ionizing radiation is partially or entirely irradiated and the atoms constituting the resist molecule are irradiated in the irradiated portion. A dry etching method characterized by promoting the oxidation of silicon in a resist pattern to improve the resistance of the resist pattern to dry etching in the subsequent oxygen-reactive ion etching by breaking the bond between the two. 2. The dry etching method according to claim 1, wherein the silicon-containing resist film is a silicon compound, polysilane, a polysilane derivative having a silicon-silicon bond in the main chain, or a polysilane / sulfone copolymer. A dry etching method using a polyolefin or polymethylmethacrylate having a silyl group introduced into a side chain. 3. A dry etching method according to any one of claims 1 to 2, wherein the bond of silicon atoms is efficiently cut by selecting the wavelength of ionizing radiation. Etching method.