JPH05291300A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing semiconductor device to form a gate electrode of a short gate length with good reproducibility and uniform distribution within the surface by a photolithography. CONSTITUTION:An SiO2 insulating film 2 is deposited on a GaAs semiconductor substrate 1 having horizontal surfaces 21, 21 and an inclined surface 22. When the horizontal planes 21, 21 of the GaAs semiconductor substrate 1 is vertically irradiated with plasma by the ECR plasma CVD method, an insulating film 2 formed on the horizontal surfaces 21, 21 is formed as a dense film with an adequate ion bombardment. Meanwhile, the insulating film 2 formed on the inclined surface 22 is easily etched with weak ion bombardment. A photoresist 3 is deposited on the insulating film 2 and an aperture 6 exposing only the inclined surface 22 is formed on the insulating film 2 with the etching. A gate electrode 5 is formed at the aperture 6 by the lift-off method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device,
In particular, it relates to a method for forming a gate electrode of a compound semiconductor transistor.

[0002]

2. Description of the Related Art Transistors using GaAs-based compound semiconductors are important as high-frequency devices, and particularly metal-semiconductor contact field effect transistors (metal semiconductors).
ctorField Effect Transistor (MESFET) has been widely studied as a device for integrated circuits (ICs). This MESF
To improve the high-frequency operating characteristics of ET, shortening the gate length is an extremely effective means, and various measures have been taken in the manufacturing process to shorten the gate length.

When the gate electrode is formed by the usual photolithography technique, the gate length is limited to about 0.5 μm. Therefore, the gate length is shortened by a method of obliquely vapor-depositing the gate electrode, a method of forming a dummy gate, or the like.

[0004]

FIG. 1 is a schematic sectional view showing a step of forming a gate electrode by a conventional oblique vapor deposition method. An insulating film 2 is formed on a GaAs semiconductor substrate 1 as shown in FIG. Photoresist 3 is deposited on this surface to form an opening. And metal 4 from diagonally above
Is vapor-deposited, metal is vapor-deposited on the photoresist 3 surface and one side of the bottom surface of the opening. As shown in FIG. 1B, the insulating film 2 on the bottom of the opening where the metal has not been vapor-deposited is etched, and the gate electrode 5 is formed in the opening thus formed by the lift-off method.

By such a method, a gate electrode having a gate length which is about ½ of the photoresist opening can be formed. However, there are problems that the gate length is changed and the in-plane distribution uniformity of the gate electrode is deteriorated due to the difference in vapor deposition angle and the variation in the film thickness of the photoresist 3.

Further, in the method of forming the dummy gate,
The formed dummy gate is made thin and the pattern is inverted,
In the process of thinning the dummy gate, there was a problem that reproducibility was poor and in-plane distribution uniformity was poor.

There is also a method of using an electron beam lithography technique for shortening the gate length, but it takes a lot of time for exposure and there is a problem that throughput is poor.

The present invention has been made in view of the above circumstances, and manufactures a semiconductor device in which a gate electrode having a short gate length can be formed by photolithography with good reproducibility and a uniform in-plane distribution. The purpose is to provide a method.

[0009]

According to the method of manufacturing a semiconductor device of the present invention, an insulating film deposited on a compound semiconductor substrate is etched, and a gate electrode is formed in an opening formed by the etching to form a semiconductor. In the method of manufacturing a device, a step of forming an inclined surface on a compound semiconductor substrate, a step of depositing an insulating film on a horizontal surface and an inclined surface of the compound semiconductor substrate so as to have different etching rates, and the inclination film on the insulating film. And a step of forming the opening in which only the surface is exposed.

[0010]

First, the basic principle of the present invention will be described. Figure 2
It is a schematic cross section showing a process of forming a gate electrode on a GaAs semiconductor substrate. As shown in Fig. 2 (a), horizontal planes 21,2
1 and SiO ₂ on the GaAs semiconductor substrate 1 having the inclined surface 22
Insulating film 2 is deposited. ECR plasma CV during this deposition
When the D method is used, the horizontal planes 21 and 21 of the GaAs semiconductor substrate 1
Then, the plasma is vertically irradiated. A dense insulating film 2 is formed on the horizontal planes 21 by the appropriate ion bombardment. On the other hand, on the inclined surface 22, since the ion impact is weak,
The insulating film 2 that is easily etched is formed. This slope
The insulating film 2 on 22 has a higher etching rate than the insulating film 2 on the horizontal surfaces 21, 21.

After that, the insulating film 2 is etched. Figure 2
As shown in (b), a photoresist 3 is deposited on the insulating film 2, and the portion including the inclined surface 22 is patterned by photolithography. Then, the opening 6 is formed in the insulating film 2 by etching. As described above, the insulating film 2 formed on the inclined surface 22 is the insulating film 2 formed on the horizontal surfaces 21, 21.
Since the etching rate is faster than that, it is possible to perform etching so that only the inclined surface 22 is exposed. Also,
The patterning when etching the insulating film 2 does not require precision. In the opening 6 thus formed, the gate electrode 5 is formed by the lift-off method as shown in FIG. 2 (c).

In the method of manufacturing a semiconductor device of the present invention, only the inclined surface of the GaAs semiconductor substrate is selectively exposed due to the difference in etching rate, and the gate electrode is formed there.
The length of the inclined surface becomes the gate length, and the gate electrode can be formed at a predetermined position while controlling the gate length.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 3 is a schematic cross-sectional view showing a process of manufacturing MESFET according to the present invention. First, Fig. 3 (a)
As shown in, the GaAs semiconductor substrate 1 is mesa-etched to 2000 Å to form a horizontal plane and an inclined plane. Next, an n layer 7 is formed in the center by Si ion implantation and activation annealing, and n ⁺ layers 8 and 8 to be source and drain region forming portions are formed on both sides thereof.

As shown in FIG. 3 (b), ECR plasma CVD
Method is used to irradiate plasma vertically to the horizontal plane of the GaAs semiconductor substrate 1. An SiO ₂ insulating film 2 is deposited on the surface of the GaAs semiconductor substrate 1. The portion including the insulating film 2 formed on the inclined surface is patterned by photolithography,
As shown in (c), the opening 6 is formed in the insulating film 2 by etching. As described above, the insulating film 2 on the horizontal surface and the insulating film 2 on the inclined surface are formed by the horizontal surface of the dense film quality and the inclined surface of the weak film quality. Since the etching rate is faster, only the inclined surface can be exposed. As a result, the bottom of the opening 6
Only the inclined surface of the GaAs semiconductor substrate 1 is provided. Next, the gate electrode 5 is formed in the opening 6 by the lift-off method as shown in FIG. 3 (d), and the ohmic electrode 9 is formed as shown in FIG. 3 (e).
9 is formed and MESFET is manufactured.

The gate of the MESFET thus formed has
The gate length is controlled to be short and the in-plane distribution is good.

[0016]

As described above, in the method of manufacturing a semiconductor device of the present invention, since the length of the inclined surface of the semiconductor substrate becomes the gate length, a gate electrode having a short gate length is formed with good reproducibility. It is formed by making its in-plane distribution uniform, etc.
The present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a step of forming a gate electrode by a conventional oblique vapor deposition method.

FIG. 2 is a schematic cross-sectional view showing a step of forming a gate electrode on a GaAs semiconductor substrate.

FIG. 3 is a schematic cross-sectional view showing a process of manufacturing a MESFET according to the present invention.

[Explanation of symbols]

 1 GaAs semiconductor substrate 2 Insulating film 3 Photoresist 5 Gate electrode 6 Opening 21 Horizontal surface of GaAs semiconductor substrate 22 Sloped surface of GaAs semiconductor substrate

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device by etching an insulating film deposited on a compound semiconductor substrate and forming a gate electrode in an opening formed by the etching, wherein an inclined surface is formed on the compound semiconductor substrate. And a step of depositing an insulating film on the horizontal surface and the inclined surface of the compound semiconductor substrate so as to have different etching rates, and a step of forming the opening in which the inclined surface is exposed in the insulating film. A method of manufacturing a semiconductor device, comprising: