JPS6246577A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an electrode having short gate length by forming a side wall to the side wall section of an opening section, narrowing the opening section and shaping the electrode. CONSTITUTION:An SiN film 2 is grown on the surface of an N-GaAs substrate 1, a photo-resist film3 is applied on the surface of the SiN film 2, and a window is bored to the resist film 3 in width through which a comparatively stable opening is acquired. When a film 4 by the quality of a material of etching characteristics (a selection ratio) different from the SiN film 2 is shaped, the SiO2 film 4 is etched in an anisotropic manner and only SiO2 formed on the side wall section of the opening section for the resist film 3 is left and the left SiO2 is used as a side wall 4', the width of the opening is narrowed only by the thickness of the side wall 4'. The SiN film 2 is etched in an isotropic manner through the opening section, and a Schottky metal is evaporated. Lastly, resist 3 is removed, and an unnecessary metal evaporated film 5 is removed through a lift-off.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for forming fine electrodes in a semiconductor device.

[Summary of the invention]

The present invention provides a method for manufacturing a semiconductor device in which an electrode is formed through an opening in a resist film. This is to obtain an electrode.

rPrior art] A conventional method for forming electrodes of a semiconductor device is described, for example, in JP-A-52
As described in Japanese Patent No. 47372, first, a material to be etched as a spacer is grown on a substrate, and a resist is applied thereon to form the required openings in the resist film. The material to be etched is isotropically etched through the opening of the resist film, and the material to be etched is also etched laterally from the opening of the resist film, so that the opening end of the resist film protrudes from the end of the material to be etched. Then, a gate electrode is formed on the substrate by vapor depositing metal through the opening of the resist film, and then the resist film is melted using a lift-off technique and the unnecessary metal vapor deposition film adhering to the resist film is removed. There is.

Therefore, in the conventional electrode forming method, the width of the gate electrode depends only on the opening width of the resist film.

[Problem that the invention seeks to solve]

In recent years, the speed of semiconductor devices has been increased, and new semiconductor devices such as QaAsFETs and HEMTs have been developed.

In such high-speed semiconductor devices, the DC conductance (g
rn), high frequency characteristics, noise gain, etc., it is necessary to realize an electrode with a short gate length, for example, 1/2 μm to 1/4 μm.

However, in the conventional technique described above, although it is possible to easily reduce the opening width of the resist film to approximately 0.7 μm to 1.0 μtn, it is difficult to reduce the opening width to 0.7 μfT1 or less in terms of reproducibility. Therefore, the gate electrode is 0.7 μm thick.
The limit is to keep it within a certain range. Therefore, electrodes with short gate lengths must be formed by a direct exposure method using an electron beam, but this method is not suitable for mass production and is uneconomical.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a technology that can easily form a semiconductor device having an electrode with a short gate length with good reproducibility and high productivity.

[Means for solving problems]

In order to achieve the above object, the method for manufacturing a semiconductor device of the present invention includes a step of forming a sidewall on the sidewall of the opening of the resist film.

[For production]

By forming a sidewall on the side wall of the opening of the resist film, the width of the opening is narrowed by the sidewall. When a gate electrode is formed by depositing an electrode material through this narrowed opening, an electrode with a short gate length can be obtained.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied to manufacturing a GaAs FET.

FIG. 1 is an explanatory diagram of the gate electrode forming process of this embodiment.

Each step will be explained in order below.

First step: An insulating film as a material to be etched is formed on the surface of the N-GaAS substrate 1 on which a gate is to be formed.
Grow film 2. This SiN film 2 ultimately serves as a spacer for gate metal lift-off, and may be any other insulating film, such as GaAs. Alternatively, the insulating film 2 may not be provided, and the substrate 1 itself may be used as the material to be etched.

Second step: A photoresist (P, R,) film 3 is applied to the surface of the SiN film 2, and a window is opened in the resist film 3 with a width that allows a relatively stable opening. The opening width of the membrane 3 is 0.8 μm.

Third step: A film 4 made of a material having different etching characteristics (selectivity) from the SiN film 2 is formed. In this example, Sin! Film 4 is grown by low temperature plasma CVD.

Like this, Sin! Forming the film 4 at a low temperature is advantageous because edges at the openings of the resist film 3 are not formed.

Fourth step: The Sine film 4 is anisotropically etched to leave only the Sing formed on the side wall of the opening of the resist film 3, and this is used as a sidewall 4'. As a result, the opening width is 4. ′ thickness. For example, if the width of the sidewall 4' is adjusted to 0.25 μm, the opening width will be 0.3 μm.

Fifth step: Next, SiN is passed through the opening with an opening width of 0.3 μm.
When performing isotropic etching of the film 2, the Si sidewall 4' used as an edge can have a sufficiently large selectivity when etching the SiN film 2, which will serve as a spacer. Therefore, etching can proceed without widening the opening (0.3 μm) between the sidewalls, and the narrowed shape can be maintained as it is.

In the sixth step, Schottky metal is deposited. With this vapor deposition,
A part of the Schottky metal vapor deposition film 5 passes through the opening between the sidewalls 4' and forms a gate electrode 5 with a width of 0.3 μm.
' is formed on the substrate l.

When forming the vapor deposited film 5, if oblique vapor deposition is performed, a finer electrode pattern can be formed.

Seventh step: Finally, the resist film 3 is removed, and the unnecessary metal deposited film 5 is removed by lift-off. This is done by dissolving the resist film 3 from the exposed portion of the resist film 3 on the SIN film 2 side using, for example, acetone.

After that, by proceeding with the normal FET process, the short gate a
A Schottky F'E'F is obtained having a gate electrode of . Although the explanation was given using GaAs FET, HE
In MT, an electrode with a short gate length can be obtained in the same way (see Figure 1).Also, in the above example, a method of forming a gate electrode with a width of 0.3 μm was described, but this gate width can be obtained by forming a gate electrode on a resist. An arbitrary width can be set by adjusting the opening width and the side wall thickness.

〔Effect of the invention〕

According to the present invention, an electrode with a short gate length can be formed with good reproducibility and mass production by simply applying conventional techniques such as sidewall technology, lift-off technology, and low-temperature plasma technology.

It is a process explanatory diagram.

Claims (1)

[Claims] 1. A step of forming a resist film having an opening on a material to be etched, and forming a sidewall on a side wall of the opening of the resist film using a material having etching characteristics different from that of the material to be etched. isotropically etching the material to be etched using the resist film on which the sidewalls are formed as a mask; and depositing a conductive material on the resist film to narrow the openings by the sidewalls. A method for manufacturing a semiconductor device, comprising: forming an electrode through an opening; and removing the resist film and removing an unnecessary conductive material deposited film adhering to the resist film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the material to be etched is an insulating film formed on a substrate or the substrate itself.