JPH0462938A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To highly accurately manufacture a gate electrode of a mushroom structure inclined toward the side of a source by a method wherein a window is opened and installed with high accuracy in order to form a gate electrode by utilizing the window in a photoresist film. CONSTITUTION:An active layer 2 and an oxide film 3 are formed on a GaAs substrate 1; and individual ohmic electrodes of a source electrode 4 and a drain electrode 5 are formed respectively through a window in the oxide film 3. Then, the whole surface is coated with a photoresist film 6; and a window 7 is opened and installed. The window 7 in the photoresist film 6 is constituted of the following: an upper-part window 7a whose width size is large; and a lower-part window 7b which is formed at the bottom of the upper-part window 7a and whose width size is very small. A recess 8 and a gate electrode 9A are formed so as to correspond to the window 7 formed in the resist film 6; and their size and their positional accuracy are controlled by the size and the positional accuracy of the window 7. Since the window 7 can be opened and installed with high accuracy by patterning the flat face of the photoresist film 6, the recess 8 and the gate electrode 9A can be formed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device.
The present invention relates to a method of manufacturing a compound semiconductor device for high frequency amplification including T.

[Conventional technology]

Generally, this type of semiconductor device has a structure in which an active layer is formed on a compound semiconductor substrate, a recess is formed in the active layer, and a gate electrode is further provided in the recess. In this case, in order to reduce the source resistance, the gate electrode often has a so-called offset structure in which it is biased toward the source side.

Conventionally, in the manufacturing method of this type of semiconductor device, a recess is formed in the semiconductor substrate by a wet etching method using a mask formed on the semiconductor substrate, and then a gate metal such as aluminum is obliquely evaporated using the same mask. By doing this, a method has been adopted in which the gate electrode is formed offset within the recess. For example, IEICE ED,
88-16゜Furthermore, conventionally, in the manufacturing method of this type of semiconductor device, a manufacturing method has been proposed in which the gate electrode is formed in an offset structure and the gate electrode is formed in a pine mushroom structure to reduce the resistance of the gate electrode. . For example, the Institute of Electronics, Information and Communication Engineers ED89-54
As shown in Figures (a) to e).

First, as shown in FIG. 3(a), a source electrode 14. is formed on a semiconductor substrate 11 on which an active layer 12 is formed. Each ohmic electrode is formed as a drain electrode 15, and a silicon oxide film 13 for forming an offset recess gate is patterned to a desired width in the intermediate portion thereof.

Next, as shown in FIG. 3(b), the entire surface is covered with a silicon nitride film 16, and a window 16a is formed in a part of the silicon nitride film 16 on the source electrode side.

Then, as shown in FIG. 3C, the silicon oxide film 13 is etched through the window 16a of the silicon nitride film 16. Subsequently, as shown in FIG. 3(d), a silicon nitride film 16 is formed.
The semiconductor substrate 11 is etched through the window 16a to form a recess 17.

Then, as shown in FIG. 3(e), a gate metal is formed on the entire surface, and this gate metal is selectively etched leaving a region including the window 16a of the silicon nitride film 16.
The gate electrode 18 having a T-shaped (mushroom-shaped) cross-sectional shape can be formed in an offset structure.

[Problem to be solved by the invention]

Among the conventional manufacturing methods described above, the former method cannot form the gate electrode in a mushroom structure, making it difficult to reduce gate resistance and cannot be used in semiconductor devices that require high-speed operation. There is a problem.

Furthermore, in the latter method, it is difficult to form the silicon oxide film 13 for forming the offset recess gate with good reproducibility, and it is difficult to form the recess with high precision.

Furthermore, since the window 16a formed in the silicon nitride film 16 must be opened near the step on the source side, it is difficult to handle the window 16a using the photolithography technology used for this purpose, and the size and position of the window must be determined with high precision. There is a problem in that it is difficult to control the offset position of the gate electrode with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device, which makes it possible to form a recess with high precision and to form a low-resistance, high-precision offset gate electrode with high precision.

[Means to solve the problem]

The method for manufacturing a semiconductor device of the present invention includes a step of forming an oxide film on a compound semiconductor substrate, a step of forming a photoresist film on the oxide film and opening a window in the photoresist film, and a step of forming a window in the photoresist film. etching the oxide film through the window of the film; etching the semiconductor substrate through the window of the oxide film to form a recess; and depositing metal from an oblique direction on the drain side with respect to the window of the photoresist film. and forming a gate electrode at a source side position of the recess.

In this case, the photoresist film window consists of an upper window with a large width and a lower window with a small width provided at the bottom of the upper window, and the gate extends over the bottom of the upper window including the lower window. A gate electrode having a pine mushroom structure is formed by vapor-depositing a metal.

Further, it is preferable that the upper window has a tapered cross-sectional shape, and the lower window has a reverse tapered cross-sectional shape.

[Effect]

According to the method of the present invention, since the gate electrode is formed using the window in the photoresist film, by opening the window with high precision, it is possible to manufacture with high precision the gate electrode with the mushroom structure biased toward the source side. becomes possible.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) to d) are cross-sectional views showing the first embodiment of the present invention in the order of manufacturing steps.
An example of application to MESFET is shown.

First, as shown in FIG. 1(a), an active layer 2 is formed on a GaAs substrate 1, an oxide film 3 is formed on the surface, and windows (not shown) are formed in required areas of this oxide film 3. ) respectively through the source electrodes 4. Each ohmic electrode of the drain electrode 5 is formed. After that, a photoresist film 6 is applied to the entire surface.
A window 7 is opened in this photoresist film 6.

At this time, the window 7 of the photoresist film 6 is formed to include an upper window 7a having a large width and a lower window 7b having a small width formed on the bottom surface of the upper window 7a. In this case, in the illustrated example, the upper window 7a has a tapered cross section, and the lower window 7b has a reverse tapered cross section, but these may be formed as windows in a vertical wall.

Next, as shown in FIG. 1(b), the oxide film 3 is wet-etched through the window 7 of the photoresist film 6 to form a window 3a, and the GaAs substrate 1 is further wet-etched through this window 3a. Active layer 2 of GaAs substrate 1
A recess 8 is formed in.

Then, as shown in FIG. 1C, aluminum 9 is vapor-deposited over the entire surface through the window 7 of the photoresist film 6. At this time, oblique deposition is performed so that aluminum 9 is deposited obliquely toward the source side. As a result, aluminum is vapor-deposited in the upper window 7 of the photoresist film 6 at a location biased toward the source side, and an aluminum gate electrode 9A is formed at a location biased toward the source side of the recess 8 through the lower window 7b.

Thereafter, as shown in FIG. 1(d), by removing the photoresist film 6, a MESFET having a mushroom shape and having a gate electrode 9A formed at a position biased toward the source side within the recess 8 is formed. Ru.

Therefore, in this manufacturing method, the recess 8 and the gate electrode 9A are formed in accordance with the window 7 formed in the photoresist film 6, and the accuracy of their dimensions and position is controlled by the accuracy of the dimension and position of the window 7. become. Since this window 7 can be formed with high precision by patterning the flat surface of the photoresist film 6, it becomes possible to form the recess 8 and the gate electrode 9A with high precision.

It goes without saying that the gate resistance is reduced because the gate electrode 9A has a mushroom shape.

FIGS. 2(a) to 2d) are cross-sectional views showing a second embodiment of the present invention in the order of manufacturing steps. Here, the present invention will be described as HJFE.
This figure shows an example applied to T, and the same or equivalent parts as in the first embodiment are given the same reference numerals.

In this manufacturing method, as shown in FIG. 2(a), an n-A/2 GaAs layer 2A and an n''
A GaAs layer 2B is formed, and a recess 8 and a gate electrode 9A are formed thereon in the steps shown in FIGS. 2(b) to 2d). This process is exactly the same as the first embodiment.

By this manufacturing method, a good mushroom gate can be formed, and an H J FET with reduced gate resistance can be formed.

〔Effect of the invention〕

As explained above, the present invention provides a photoresist film with an upper window with a large width and a lower window with a small width provided at the bottom of the upper window, and a diagonal direction on the drain side with respect to these windows. Since the gate electrode is formed by vapor-depositing the gate metal from the source, it is easy to form a window with high precision in the flat photoresist film. Can be manufactured with high precision.

[Brief explanation of drawings]

FIGS. 1(a) to d) are cross-sectional views showing the first embodiment of the present invention in the order of manufacturing steps, and FIGS. 2(a) to d) are cross-sectional views showing the second embodiment of the present invention in the order of the manufacturing steps. Figure, Figure 3 (a
) to e) are cross-sectional views showing an example of a conventional manufacturing method in the order of steps. 1...GaAs substrate, 2...active layer, 2A...n
-AlGaAs layer, 2B-n"GaAs layer, 3... Oxide film, 4... Source electrode, 5... Drain electrode, 6
... Photoresist film, 7... Window, 8... Recess, 9... Aluminum, 9A... Gate electrode, 11
... Semiconductor substrate, 12... Active layer, 13... Silicon oxide film, 14... Source-side electrode, 15... Drain electrode, 16... Silicon nitride film, 17... Recess , 18...gate electrode. Figure 2 (C) Meme N Noah 111 Ward Wa: vm Figure

Claims (1)

[Claims] 1. A step of forming an oxide film on a compound semiconductor substrate, a step of forming a photoresist film on the oxide film, and a step of opening a window in the photoresist film, and a step of forming a window in the photoresist film. etching the oxide film through the window;
A step is to form a recess by etching the semiconductor substrate through the window of the oxide film, and a gate electrode is formed at a position on the source side of the recess by depositing metal from an oblique direction on the drain side with respect to the window of the photoresist film. The window of the photoresist film is composed of an upper window with a large width and a lower window with a small width provided at the bottom of the upper window, and the window of the photoresist film includes a 1. A method of manufacturing a semiconductor device, comprising depositing a gate metal up to the bottom to form a mushroom-structured gate electrode. 2. The upper window has a tapered cross section, and the lower window has a reverse tapered cross section.
A method for manufacturing a semiconductor device according to section 1.