JPH0451985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a GaAs insulated gate field effect transistor.

(Prior art and its problems) GaAs has electron mobility several times higher than that of Si, so it has been expected to be a material for high-speed operating devices.
However, with Si, the interface between the thermal oxide film SiO ₂ and Si is good, and a MOSFET can be realized in the container.
GaAs has a high interface state density no matter what insulating film formation method is used, and a good MIS structure cannot be obtained. For this reason, as a GaAs field effect transistor, a shot gate field effect transistor (hereinafter abbreviated as MESFET), which utilizes a shot barrier between GaAs and a metal, has been used. However, with GaAs MESFETs, it is not possible to apply a positive voltage of +0.8V or more to the gate electrode, so GaAs ICs (DCFLs) using enhancement-type MESFETs have had the problem of not being able to achieve a large logic amplitude. Another problem was that the shot gate was susceptible to heat and electrical shock and was easily damaged.

However, GaAs insulated gate field effect transistors (hereinafter abbreviated as GaAs MISFETs) are
It has faster operating speed than MOSFET, and GaAs
Compared to short-gate field effect transistors (MESFETs), it is possible to apply a positive voltage to the gate, so the logic width when forming an integrated circuit can be increased, making it suitable for all fields where FETs and ICs are currently used. The field of industrial application is extremely wide, especially in fields that require high-speed processing, such as computer CPV,
There is a strong demand for the development of GaAs MISFETs as they are expected to be used in memory, image processing, etc.

In the production of GaAs MISFETs, with conventional methods, when an insulating film is formed on the GaAs surface, Ga vacancies are generated and the interface state density increases, regardless of the type of insulating film, making it difficult to obtain a good interface. Nakatsuta.

(Structure of the Invention) The present invention has been made to solve these problems, and provides a method for manufacturing a GaAs MISFET.

The present invention will be explained below.

In order to suppress this diffusion of Ga on the GaAs surface to the insulating side, the inventors added Ga to an alcohol solution of SiO ₂ .
A good interface was obtained by pre-impregnating and heat-treating. The inventors also obtained a good interface by anodizing the vacuum-deposited Al on the GaAs surface right up to the interface. However, the present invention further improves these insulating film forming methods, and uses a method of forming an Al film containing a large amount of Ga following the growth of GaAs in an ultra-high vacuum.

The manufacturing method of the present invention will be explained below based on the drawings.

First, as shown in Figure 1a, an SI-doped n-type GaAs layer 2 of 1000 Å is grown on a semi-insulating GaAs substrate 1 by molecular beam epitaxial method, and after lowering the substrate temperature, GaAs layer 2 is grown in an ultra-high vacuum. A solid solution alloy film 3 of Ga and Al is grown to a thickness of 500 Å using molecular beams of Ga and Al. The mole percent of Ga in the solid solution alloy is 20-80%.

In solid solution alloys of Al and Ga, phase separation occurs at temperatures above 29°C, so cool the substrate sufficiently.
Ga-Al film is grown.

Next, the solid solution alloy film 3 is immediately oxidized in oxygen plasma until all the solid solution alloy film 3 becomes an insulating film 4 (FIG. 1b).

Next, as shown in FIG. 1c, two regions of the insulating film 4 are removed.

Thereafter, an electrode pattern of AuGeNi is formed in this region and heat treated at 450° C. for 3 minutes to form ohmic electrodes 5 and 6 (FIG. 1d).

Next, as shown in FIG. 1e, the ohmic electrode 5,
A gate electrode 7 of Al is formed on the insulating film 3 between the gate electrodes 6 and 6.

The method for insulating the Ga-Al film is not limited to the anodic oxidation method in oxygen plasma described in the embodiment, but may also be an anodic oxidation method in an electrolyte solution, for example. Detection of completion of oxidation of Ga-Al film using these methods is as follows:
It can be easily detected by a change in the slope of the anode voltage one hour curve or by the appearance of interference colors.

(Effect of the invention) The present invention has the following excellent effects.

When a GaAs layer is exposed to the atmosphere, GaAs
A GaAs native oxide film is formed on the surface, making it impossible to obtain a good interface, but in the present invention,
The above problem does not exist because the Al film containing Ga is grown in an ultra-high vacuum.

This Ga-Al film contains a large amount of Ga, so it can be used during oxidation or subsequent heat treatment.
Diffusion of Ga into the insulating film is suppressed.

Since this Ga-Al film contains Al, a stable oxide film with a high electricity supply rate and good chemical resistance is obtained.

This Ga-Al film contains Al, so even though it is in an ultra-high vacuum, GaAs
It absorbs the very small amount of oxygen present on its surface.

(Industrial Applicability) In the above embodiment, the n-type GaAs layer 2 is used as the active layer, and the thickness of the depletion layer directly under the gate electrode is changed by the voltage applied to the gate electrode.
It is a type of FET that modulates the current flowing through the
The FET structure is not limited to this embodiment. For example, an inverted type using a p ^-type layer as the active layer
The insulating film forming method according to the present invention can also be applied to MISFET.

[Brief explanation of the drawing]

FIGS. 1A, 1B, 1C, 1D, and 1E are diagrams for explaining one embodiment of the present invention, and are for showing the cross-sectional structure of the device at each stage of the manufacturing process. 1 is a semi-insulating GaAs substrate, 2 is an n-type GaAs layer,
3 is a Ga-Al solid solution alloy film, 4 is a Ga-Al oxide film,
5 and 6 are ohmic electrodes (AuGeNi), and 7 is a gate electrode (Al).

Claims (1)

[Claims] 1 In an ultra-high vacuum on a semi-insulating GaAs substrate,
a step of growing a GaAs layer; a step of subsequently growing an Al film containing a large amount of Ga on the GaAs layer in an ultra-high vacuum; and a step of insulating the Al film;
A GaAs insulated gate field effect transistor comprising the steps of removing the insulating film in two regions, forming an ohmic electrode in the two regions, and forming a gate electrode on the insulating film between the two ohmic electrodes. manufacturing method.