JPH01306581A - Method for etching thin film - Google Patents

Abstract

PURPOSE:To suppress damage due to irradiation with ions and to gently slope the pattern edge of a thin film by etching the thin film through a resist as a mask, removing the pattern edge of the resist with oxygen plasma and etching the thin film again. CONSTITUTION:A thin Cr film 2 is laminated on a substrate 1 and a resist 3 is selectively left on the film 2. This film 2 is selectively etched and the pattern edge of the resist 3 is removed with oxygen plasma so that the resist 3 is made to stand back from the pattern edge of the film 2. The film 2 is then etched again to gently slope the pattern edge of the film 2. By this method, the reliability of a TFT device, a semiconductor device, etc., can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a taper etching method for metal thin films, etc., and particularly to an etching method for forming wiring for thin film transistors (TPT), liquid crystal display devices, etc.

[Summary of the Invention] The present invention involves etching a thin film such as a metal film using a resist as a mask, removing the edges of the resist using oxygen plasma, and etching the thin film again to gently smooth the edges of the thin film pattern. Accordingly, the present invention provides thin film transistors, liquid crystal display devices, etc., which have a high interlayer dielectric strength voltage and are resistant to disconnection.

[Prior art] Cr thin film has high melting point, hardness, light shielding properties, etc.
It is used as part of the wiring and electrodes of LCDs and liquid crystal display devices.

The selective etching of Cr used in this process has conventionally been performed using dibasic sulfuric acid (
Wet etching using an aqueous solution of cerium ammonium (nitric acid) and perchloric acid has been mainly used. However, with this method, it is difficult to control the shape of the Cr end face, which is almost perpendicular to the substrate surface. If an interlayer insulating film is deposited on this Cr thin film by CVD or the like, the step coverage at the end face will be poor (this may cause a short circuit with the upper layer wiring or a breakdown voltage failure), and the wiring that crosses the Cr wiring will break. To prevent this problem, it is necessary to smooth the end face of the Cr thin film, but this is generally difficult with the above wet etching, so dry etching is used.

Ion etching (milling) is particularly advantageous in that it allows the anisotropy of etching to be controlled. FIG. 2 shows an example of selective etching of a Cr thin film using ion etching.

FIG. 2(a) is a cross-sectional view in which a Cr thin film 2 is deposited on the entire surface of the substrate 1, and then a photoresist 3 is selectively left by a normal mask process. Thereafter, the Cr thin film 2 is selectively etched by rotating the substrate 1 while obliquely irradiating the substrate surface with ions such as Ar'' (FIG. 2(b)).
, then the resist 3 was removed and selectively etched Cr
A thin film 2 is left (FIG. 2(C)). If ion etching is used as in this example, taper etching is possible, but there are problems such as expensive equipment, difficulty in detecting the end point of etching, and ion irradiation damage to the substrate.

[Problems to be Solved by the Invention] As described above, in wet etching, the edge of the etched Cr thin film is formed perpendicular to the substrate surface, so an interlayer insulating layer and a conductive layer are formed on the Cr thin film. When the layers are deposited, there are problems such as disconnection of the conductive layer, short circuit between the Cr thin film and the conductive layer, and breakdown voltage failure. Further, although dry etching allows taper etching and can prevent the above-mentioned problems, it also has problems such as ion irradiation damage to the substrate and high cost.

[Means for Solving the Problems] In order to solve the above problems, the present invention etches a thin film using a resist as a mask, and then etches the ends of the resist using oxygen plasma or the like so that the ends of the resist are inside the ends of the thin film. After the removal, the thin film is etched again.

[Operation] As described above, according to the thin film etching method of the present invention, after etching the thin film using a resist as a mask, the edges of the resist are removed using oxygen plasma using, for example, a parallel plate type anodic coupled plasma etching apparatus. However, by etching the thin film again, it is possible to form gentle pattern edges of the thin film with little ion irradiation damage and at low cost.

Therefore, by the thin film etching method of the present invention, TP
When forming elements with a multilayer structure such as T, the shape of the edge of the thin film pattern is gentle, so step coverage at the edge is improved, preventing short circuits or breakdown voltage failures in upper and lower layer wiring. Moreover, it is possible to prevent the occurrence of disconnection of the upper layer wiring, thereby achieving improvement in reliability of TPT and semiconductor manufacturing, and improvement in manufacturing yield.

(Example 1 The present invention will be explained in detail below using the drawings.

FIG. 1 shows an explanatory diagram of the etching process of a Cr thin film according to the present invention. FIG. 1(a) shows a state in which a Cr thin film 2 is laminated by sputtering or the like on a substrate 1, with a resist 3 selectively left behind. Those that have advanced up to that point are also used. Cr
The thin film 2 is deposited to a thickness of, for example, 2000 angstroms by sputtering, and the resist 3 is formed, for example, of a positive type to a thickness of 1.3 μm. FIG. 1(b) shows the Cr thin film 2 selectively etched by wet etching, which is a conventional etching method. Etching can be performed at approximately 45+ using a mixed solution of ceric ammonium nitrate and perchloric acid aqueous solution. . FIG. 1(C) shows a state in which the resist 3 is brought to the inside of the edge of the Cr thin film 2 by oxygen plasma treatment.
．． It was etched for 2 minutes at 3 Torr, power 0, and 4 W/cm''. Figure 1(d) shows wet etching, which was immersed in the etchant for about 5 minutes of the first etching time and then etched again. The state after Cr etching is shown. FIG. 1(e) shows the state after the resist has been removed. As shown in the figure, the Cr thin film 2 has a gentler cross-sectional shape than the conventional one.

Examples of Cr thin films have been described above, but for example, A1.
The present invention is also effective for thin films such as insulating films.

[Effects of the Invention] As is clear from the above description, unlike conventional taper etching of thin films, the edges of the thin film can be formed smoothly without damaging the substrate by ion irradiation, leading to cost reduction. In addition, since the edges of the thin film have a gentle shape, it is possible to provide highly reliable TPT devices, semiconductor devices, liquid crystal display devices, etc. with improved interlayer dielectric breakdown voltage of multilayer wiring and disconnection of upper layer wiring at low cost. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the thin film etching process according to the present invention;
FIG. 2 is an explanatory diagram of a thin film etching process according to a conventional method. 1...Substrate 2...Cr thin film 3...Resist and above Applicant Seiko Electronics Industries Co., Ltd. Agent Patent attorney Keisuke Hayashi Figure 1

Claims (1)

[Claims] After etching the thin film coated on the substrate using the resist as a mask, the edges of the resist pattern are removed by oxygen plasma, the thin film is etched again, and the edges of the formed thin film pattern are smoothed. A thin film etching method characterized by: