JPH01170024A - Dry etching - Google Patents

Abstract

PURPOSE:To improve the reproducibility and the evenness by a method wherein, after removing a protective film formed by plasma etching process, the photoexciting etching process is performed. CONSTITUTION:A silicon oxide film 12 (gate oxide film) and a polycrystalline film 13 doped with phosphorus are laminated on a silicon substrate 11. Then, a photoresist pattern and the polycrystalline silicon film 13 is plasma-etched simultaneously a protective film 15 is formed on the sidewalls of a pattern and the bottom. Furthermore, the protective film 15 is etched away by fluoric acid solution, any residual polycrystalline silicon film 13 is etched away by photoexciting process to form a pattern of polycrystalline silicon film. Through these procedures, a fine pattern with high precision can be processed in excellent reproducibility and evenness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dry etching method used for manufacturing semiconductor integrated circuits, thin film devices, etc., and relates to a microfabrication method with extremely high precision and excellent reproducibility.

- [Prior art] In the microfabrication process of thin films, anisotropy, high selectivity, and low damage are required, and for this reason, a method that uses plasma etching (reactive ion etching, reactive sputter etching) and photoexcited etching in combination is recommended. Proposed. Related methods of this type include, for example, the patent application filed in 1983-
No. 168903, Japanese Patent Application No. 60-287748, and the like.

[Problem that the invention seeks to solve]

In the above-mentioned conventional techniques, no consideration is given to the reproducibility and uniformity of photoexcited etching after plasma etching.

It is an object of the present invention to improve the reproducibility and uniformity of a combined plasma etching and photo-stimulated etching process.

c. Means for Solving Problems] The above object is achieved by removing the protective film formed on the surfaces exposed by plasma etching (the side and bottom surfaces of the pattern) and then performing photoexcited etching. .

[Effect]

In the plasma etching (reactive ion etching) method, a protective film (referred to as a side protection film) is formed on the surface exposed by etching, particularly on the sidewalls of the pattern. This protective film is formed by a reaction product of a photoresist mask or a thin film to be processed that is eroded by plasma, or a reaction product of a plasma reaction vessel or electrode material and plasma gas mixed into the reaction atmosphere. Ru. By adhering this protective film to the sidewalls of the etching pattern, etching anisotropy is achieved. The protective film attached to the bottom of the etching pattern is
Sputtered by vertically accelerated plasma flow,
Etching of the thin film to be processed progresses.

On the other hand, photoexcited dry etching is sensitive to surface conditions, and the etching rate is affected by protective films, natural oxide films, etc., which becomes an obstacle to improving reproducibility and uniformity.

The present invention involves removing the protective film formed after plasma etching and then performing photo-excited dry etching, thereby improving the reproducibility and uniformity of etching.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The dry etching of polycrystalline silicon in the manufacturing process of the spastic M-top polycrystalline silicon gate MO8 structure will be explained with reference to FIG.

FIG. 1(a) shows a silicon oxide film 12 (gate oxide film) with a thickness of 140 nm and a silicon oxide film 12 with a thickness of 300 nm on a silicon substrate 11.
This shows a state in which phosphorus-doped polycrystalline silicon films 13 are stacked.

Figure 1(b) has a width of 0.8 by ordinary photolithography.
A state in which a μm photoresist pattern 14 is formed is shown.

FIG. 1(c) shows a state in which the polycrystalline silicon film 13 has been etched to a thickness of 280 to 290 nm by plasma etching. At this time, a protective film 15 is formed on the sidewalls of the pattern and the etched bottom surface.

In plasma etching, a silicon substrate is placed on the cathode of a reaction vessel, and CzCQFs is used as a reaction gas at a pressure of Q,
It was maintained at 2 Torr. High frequency power supply (13,56M
Hz, output 200W) to generate plasma,
A polycrystalline silicon film was reactive ion etched to a thickness of 280 to 290 nm. The pattern dimensions are within the measurement limit of ±0.05 μm compared to the photoresist pattern.

FIG. 1(d) shows the protective film removed by etching with a hydrofluoric acid solution (5% concentration).

FIG. 1(e) shows a state in which the remaining polycrystalline silicon film 13 is etched by photoexcitation etching, and a pattern of the polycrystalline silicon film is formed.

In photo-excited etching, a silicon substrate is placed in a reaction vessel, H (12) is introduced as a reaction gas, and the pressure is 50 Torr.
was held at A low-pressure mercury lamp (wavelength 18
The silicon substrate was irradiated with light using 5 nm and 254 nm, and the illumination intensity of 185 nm light on the substrate surface was 4 mW/cm. Polycrystalline silicon film 13
The underlying silicon oxide film 1 is etched selectively.
2 does not etch at all. Although the radical reaction is isotropic, since the thickness of the polycrystalline silicon film to be etched is small, the amount of side etching is small, and a high accuracy within ±0.05 μm can be achieved with good reproducibility compared to a photoresist pattern.

Dry etching of large groove j1 metal silicide and polycrystalline silicon film stack will be explained.

The film to be processed is one in which a molybdenum film is deposited on a polycrystalline silicon film by a sputtering method, and a molybdenum silicide film is formed by heat treatment.

As in Example 1, a photoresist pattern was formed.

First, most of the molybdenum silicide film and polycrystalline silicon film were etched by plasma etching (reactive ion etching). The remaining thickness of the polycrystalline silicon film is 5 to 30 nm.

The formed protective film and photoresist film were removed by plasma etching. Etching is performed by a chemical dry etching method using microwave (2.45 GHz, output 270 W) excitation of 02 gas. Since the surfaces of the molybdenum silicide film and the remaining polycrystalline silicon film are oxidized by this step, the oxide film is subsequently removed by microwave-induced chemical drying using HCQ.

Next, in the same manner as in Example 1, the remaining polycrystalline silicon film was etched by photo-excited etching to form a laminated film pattern of a molybdenum silicide film and a polycrystalline silicon film. Here, the photoexcitation etching speed of the molybdenum silicide film is several percent compared to that of the polycrystalline silicon film, and even after the photoresist mask is removed, the film thickness of molybdenum silicide decreases by less than 1 nm, which poses no practical problem. . In addition, high accuracy and uniformity within ±0.05 μm were confirmed for the pattern size distribution at 9 points within a 5'φ wafer and at 25 wafers within a lot.

〔Effect of the invention〕

According to the present invention, by rationally combining plasma etching by discharge excitation and gas phase reaction by photoexcitation,
High-precision fine pattern reproducibility.

Can be processed with good uniformity.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a semiconductor substrate according to an embodiment of the present invention. 11... Silicon substrate, 12... Silicon oxide film,
13... Polycrystalline silicon film, 14... Photoresist pattern, 15... Protective film.

Claims (1)

[Claims] 1. When finely processing a thin film on the surface of a substrate into a desired pattern, (a) a step of plasma etching to a predetermined thickness by discharge excitation. (b) a step of removing the protective film formed on the etched surface exposed in the above step; and (c) a step of etching the entire thickness of the thin film by a gas phase reaction caused by light excitation. Etching method.