JPS63300568A - Formation of schottky electrode - Google Patents

Abstract

PURPOSE:To effectively form a Schottky electrode formed in its shape by forming a certain first insulating film on a heat resistant conductive film, and forming a second insulating film thereon. CONSTITUTION:A semiconductor substrate 11 made of GaAs is covered with a conductive film 12 made of tungsten silicide of a high melting pint conductive material to form a Schottky junction with the GaAs. Then, it is covered with a first insulating film 12 made of a silicon oxide film, and formed in a predetermined shape. Then, after it is heat treated at a high temperature, it is covered with a second insulating film 14 made of silicon nitride, and its surface is flattened by a photoresist film 15. Thereafter, the whole surfaces of the films 14, 15 are gradually etched, and the etching is finished during the period from when the surface of the film 13 is exposed to when the surface of the film 12 is exposed. Then, when it is etched with diluted fluoric acid, the surface of the film 12 is exposed. Subsequently, a low resistance metal film 15 made or noble metal, such as Au is covered in contact with the film 12, and shaped to form a low resistance gate (Schottky electrode).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a Schottky electrode, and particularly to a method for forming a Schottky gate of a field effect transistor.

[Conventional technology]

A conventional technique of this type will be explained with reference to FIGS. 3(a) to 3(d).

First, as shown in FIG. 3(a), a heat-resistant conductive film 2 made of W-3t is coated on the surface of a semiconductor substrate 21 made of GaAs.
form 2. Thereafter, as shown in FIG. 3(b), an insulating film 23 made of silicon oxide is deposited, and the surface is flattened with a photoresist film 24.Then, the entire surface is etched under the condition that the etching rates of the insulating film 23 and the photoresist film 24 are equal. gradually etching. As shown in FIG. 3(c), the etch lag is terminated when the surface of the conductive film 22 is exposed, and a low resistance metal film 25 made of Au is deposited on the surface. next,
As shown in FIG. 3(d), the low resistance metal film 25 was shaped into a predetermined shape to form a low resistance Schottky electrode.

[Problem that the invention seeks to solve]

In the conventional Schottky electrode formation method described above, it is difficult to determine the end point of etching when exposing the surface of a heat-resistant conductive film. If the conductive film and low-resistance metal film do not contact each other and the amount of etching is too large,
The drawback is that the deposition and shaping of the low-resistance metal film are not successful, making it impossible to obtain a Schottky electrode with uniform characteristics.

[Means for solving problems]

The method for forming a Schottky electrode of the present invention includes the steps of forming a conductive film and a first insulating film forming a Schottky junction on the surface of a semiconductor substrate and shaping them into a predetermined shape, and depositing a second insulating film on the entire surface. a step of embedding the conductive film and the first insulating film, a step of depositing a resist film with a flat surface, and a step of exposing the surface of the first insulating film by etching, and then removing the first insulating film. The method includes a step of selectively removing the conductive film to expose the surface of the conductive film, and a step of depositing a metal film in contact with the conductive film.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(d) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining a first embodiment of the present invention.

First, as shown in FIG. 1(a), a conductive film 12 made of tungsten silicide, which is a high melting point conductive material that forms a Schottky junction with GaAs, is deposited to a thickness of 400 nm on the surface of a semiconductor substrate 11 made of GaAs. . Next, a first insulating film 13 made of a silicon oxide film with a thickness of 300 nm is formed.
is applied and shaped into a predetermined shape.

After the high-temperature heat treatment necessary for manufacturing field effect transistors, the first
As shown in Figure (b), a second insulating film 13 made of silicon nitride is applied to a conductive film 12. It is deposited to the same extent as the total thickness of the first insulating film 13, and the surface is made flat by the photoresist film 15. Next, the entire surface is gradually etched under dry etching conditions in which the etching rate of the silicon nitride film (14) and the photoresist film 15 are the same, and after the surface of the first insulating film 13 is exposed as shown in FIG. Etching is completed before the surface of film 12 is exposed. The silicon nitride film (
14) is hardly etched, and the silicon oxide film (
13) is removed, and the surface of the vV-3i film (12) is exposed.Next, a low resistance metal film 16 made of a noble metal such as Au is brought into contact with the conductive film 12 as shown in FIG. 1(d). A low-resistance gate (Schottky electrode) is formed by applying and shaping the
form.

Etching of the second insulating film can be completed at any time between when the surface of the first insulating film is exposed and when the surface of the conductive film 12 is exposed. No problems arise in processing the Schottky electrode made of the metal film 16.

FIGS. 2(a) to 2(c) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining a second embodiment of the present invention.

Next to the steps explained using FIGS. 1(a) and 1(b), etching is performed until the surface of the convex portion of the silicon nitride film (14) is exposed as shown in FIG. 2(a). Next, see Figure 2 (
As shown in b), the silicon nitride film is etched using the photoresist film 15 as a mask, and the etching is completed before the surface of the silicon oxide film 13 is exposed and the surface of the conductive film 12 is exposed. Thereafter, only the remaining silicon oxide film (13) is etched with diluted hydrofluoric acid to expose the surface of the conductive film 12, and a low resistance metal film 16 such as Au is etched as shown in FIG. 2(c). ) to form a low resistance gate electrode. This embodiment has the advantage that the capacitance between the low resistance metal film and the semiconductor substrate can be reduced and the characteristics of the Schottky gate field effect transistor can be improved.

〔Effect of the invention〕

As explained above, in the present invention, a first insulating film is first formed on a heat-resistant conductive film, and a second insulating film is formed on top of the first insulating film. The end point of the process can be arbitrarily selected between the time when the surface of the first insulating film on the heat-resistant conductive film is exposed and the time when the surface of the heat-resistant conductive film is exposed, making it possible to form a well-shaped Schottky electrode. It can be formed reliably and is effective in manufacturing semiconductor devices such as Schottky diodes and Schottky gate field effect transistors with good reproducibility.

[Brief explanation of drawings]

Figures 1 (a) to (d), Figures 2 (a) to (c), and Figure 3.
Figures (a) to (d) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining a first embodiment, a second embodiment, and a conventional example of the present invention, respectively. 11.21... Semiconductor substrate, 12.22... Conductive film, 13... First insulating film, 14.24... Photoresist film, 15... Photoresist film, 16... Metal film , 23... Insulating film, 25... Low resistance metal film. Ml Illustration helmet 2Z No. 37

Claims (1)

[Claims] A conductive film forming a Schottky junction on the surface of a semiconductor substrate and a first
a step of forming an insulating film and shaping it into a predetermined shape, a step of depositing a second insulating film over the entire surface and embedding the conductive film and the first insulating film, and depositing a resist film with a flat surface. exposing the surface of the first insulating film using an etching technique and then selectively removing the first insulating film to expose the surface of the conductive film; and a metal film in contact with the conductive film. A method for forming a Schottky electrode, the method comprising: depositing a Schottky electrode.