JP3147843B2 - Method for manufacturing field effect semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect semiconductor device and a method of manufacturing the same, and more particularly, to a GaAs MESF-ET and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, a field effect transistor (FET) using GaAs as a semiconductor material has a symmetrical recess structure in which a gate is located at the center between a source and a drain. By making the distance at the bottom of the recess on the drain electrode side longer than the distance,
The source resistance Rs is reduced, the transconductance gm is increased, the gate reverse breakdown voltage is improved, and output power, efficiency, and distortion are reduced even in microwave characteristics. For this reason, various methods for manufacturing an FET having an asymmetric recess have been studied.

As a first example of such a production method, a production method described in JP-A-61-154177 is known. In this technique, first, as shown in FIG.
A low-temperature growth plasma nitride film 22 is formed on an As substrate 21, and then a CVD oxide film 23 and a plasma nitride film 24 are formed.
Grow. Next, a photoresist film (hereinafter, referred to as PR) 25 is formed, and the plasma nitride film 24 and the CVD oxide film 23 are dry-etched using the PR 25 as a mask. Next, as shown in FIG. 2B, the low temperature growth plasma nitride film 22 is removed by wet etching.
After the PR 25 is also removed, recess etching is performed. Next, as shown in FIG. 3C, a metal film 28 is applied, and a gate electrode 29 is formed by a lift-off method, thereby completing the FET.

As a second example of the conventional manufacturing method,
A manufacturing method described in JP-A-3-145140 is known.

In this technique, first, as shown in FIG. 3A, an oxide film 32 is formed on a GaAs substrate 31, and a PR 38 having three openings is formed on the oxide film 32. . Next, using PR33 as a mask, the oxide film 3
2 after dry etching, P
Form R35. Next, as shown in FIG.
The oxide film 32 is removed by etching using B33 and PR35 as a mask, and a recess 36 is formed in this portion. Next, as shown in FIG. 3C, a metal film 37 is deposited.
The gate electrode 3 is formed on the recess 36 by a lift-off method.
8 is formed, and the FET is completed.

[0006]

According to such a conventional technique, in the first example, a low-temperature-grown plasma nitride film 22 is used.
However, it is necessary to position the opening 26 for forming the gate electrode with high precision. However, the accuracy of alignment in the current lithography technology is about 0.
1 μm is the limit, and the variation in alignment is R
There is a problem that variations in s and BVgd occur.

In the second example, the distance between the three openings formed in the oxide film 32 on the semiconductor substrate 31 cannot be reduced more than a certain distance. In practice, the spacing between openings cannot be less than about 0.4 μm due to the limitations of lithography and etching techniques. Therefore, there is a problem that the distance of the recess bottom on the source electrode side cannot be reduced and Rs cannot be reduced.

An object of the present invention is to provide a field effect type semiconductor device capable of effectively solving such a conventional problem.

[0009]

According to the present invention, in order to achieve the above object, an insulating film is formed on a semiconductor substrate, and an opening is formed in a part of the insulating film. A photoresist having a similar opening at a position slightly deviated from the entrance of the insulating film is formed on and above the opening, and the insulating film is used as a mask with the photoresist as a mask, and the opening of the insulating film is formed on one side. To the photoresist located in the area, and the other side is etched to the design dimensions, then recessed on the semiconductor substrate using the photoresist and the insulating film as a mask, and then a gate electrode is formed on the recess by a lift-off method. It is characterized by being formed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, referring to the attached drawings,
Examples of the present invention will be described more specifically. FIG. 1 (a)-
(E) illustrates an embodiment of the present invention. First, as shown in FIG. 1A, after a source electrode 2 and a drain electrode 3 are formed on a GaAs substrate 1, a CVD electrode is formed thereon.
An oxide film 4 as an insulating film is formed by a method. Next, an opening 5 is formed in the oxide film 4 by a lithography technique and a dry etching technique. Next, the oxide film 4
A PR 6 having a gate forming window 6a is formed thereon. The gate forming window 6a is formed at a position closer to the drain than the opening 5. Next, as shown in FIG. 1B, the oxide film 4 is etched with hydrofluoric acid using the PR6 as a mask. At this time, due to side etching, PR6 serves as an etching stopper on the source side, and the drain side is etched to the designed size. Thus, the recess forming window 7 is formed. Next, as shown in FIG. 1C, a recess 8 is formed using the oxide film 4 and PR6 as a mask. Next, as shown in FIG. 1D, A19 is deposited as a gate metal, and then, as shown in FIG. 1E, a gate electrode 9a is formed by a lift-off method to complete the FET.

As described above, in the present embodiment, the gate forming window 6a only needs to be formed at a position closer to the drain than the opening 5, and the recess pattern and the gate pattern need not be superimposed with high accuracy. An asymmetric recess can be easily formed.

[0012]

As described above, according to the present invention,
Since the asymmetric recess can be reliably formed without the necessity of a high-accuracy superposition process, the source resistance Rs can be reduced, the transconductance gm can be increased, and the gate reverse breakdown voltage can be improved. Also, the output power and efficiency can be improved and the distortion can be reduced in the microwave characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing main steps of one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing main steps of a first conventional example.

FIG. 3 is a sectional view showing main steps of a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 GaAs substrate (semiconductor substrate) 2 Source electrode 3 Drain electrode 4 Oxide film (insulating film) 5 Opening 6 PR (photoresist film) 6a Gate formation window 7 Recess formation window 8 Recess 9 Al film 9a Gate electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/338 H01L 29/812

Claims (2)

(57) [Claims] 1. After depositing an insulating film on a semiconductor substrate,
Opening a part of the insulating film;
A little from the opening of this insulating film
At a position with an opening exposing the insulating film.
Forming the photoresist and masking the photoresist.
Side etching the insulating film
Therefore, this insulating film is formed on the source electrode side by opening the insulating film.
To the position regulated by the photoresist
And the drain electrode side is etched,
Stop etching when etching to the design dimensions
Removing by stopping, and the photoresist
A recess is formed on the semiconductor substrate using the
And a lift-off method on this recess.
Forming a gate electrode.
A method for manufacturing a fruit-shaped semiconductor device . A source electrode and a drain electrode on the semiconductor substrate;
A step of forming the in-electrodes and covering them with an insulating film.
Attaching, and opening a part of the insulating film;
The opening of the insulating film is formed on the insulating film and the opening thereof.
An opening that exposes the insulating film at a position slightly deviated from
Forming a photoresist having
Using the dist as a mask, this insulating film is
By the photoresist located at the opening of the insulating film
Removed to the regulated position, and drain electrode side
When the etching process has been etched to the design dimensions,
Removing by stopping the etching process;
The above semiconductor substrate is formed by using the photoresist and the insulating film as a mask.
Forming a recess on the plate and lifting on the recess
Forming a gate electrode by an off method.
A method for manufacturing a field-effect semiconductor device.