JPS63173375A - Schottky junction type field-effect transistor - Google Patents

Abstract

PURPOSE:To improve a breakdown strength of gate.drain, by providing, on the N-type operating layer on the drain side, a drain Schottky metal layer wherein a part of the surface at least is covered by an ohmic electrode and which is electrically connected to an N<+> type active layer. CONSTITUTION:On a semi-insulative gallium arsenide substrate 1, an N<+> active layer 3 is formed in an N-type operating layer 2 and a source.drain region by an ion implantation method. After a tungsten silicide layer is formed on the whole surface, a gate electrode 4 composed of tungsten silicide is formed on the N-type operative layer 2 by a dry etching method, and at the same time, a drain Schottky metal layer 5 is formed in the vicinity of a boundary between the N-type operating layer 2 of the drain side and the N<+> type active layer 3. After a passivation film 7 covering the gate electrode 4 is formed, an ohmic electrode 6 composed of AuGe.Ni is formed in the source.drain region and alloyed. At this time, the ohmic electrode 6 on the drain side is formed so as to lap on the upper part of the drain Schottky metal layer 5 formely formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Schottky junction field effect transistor.

[Conventional technology]

In order to improve the breakdown voltage between the gate 1 and the drain of a Schottky junction field effect transistor having an n+ active layer in the source/drain region, conventionally a gate electrode 4 and an ohmic electrode 6 are used as shown in FIG. Generally, a method has been used in which an offset structure is formed by increasing the distance between the gate electrode 4 and the n+ type active layer 3A.

[Problem that the invention seeks to solve]

However, since the ohmic electrode 6 is usually formed by a lift-off method, the processing condition near the etch is relatively rough, and electric field concentration points (hot spots) are likely to be formed in this area, resulting in variations in breakdown voltage between the gate and drain. becomes larger. Furthermore, if the distance between the gate electrode 4 and the ohmic electrode 6 or the n+ type active layer 3A is too large, the channel resistance increases and the characteristics of the device deteriorate.

The object of the present invention is to eliminate the above-mentioned problems and to improve the breakdown voltage between the gate and drain.
The purpose is to provide transistors.

[Means for solving problems]

The Schottky junction field effect transistor of the present invention includes:
A Schottky junction field effect transistor having an n-type active layer formed on a semi-insulating substrate, an n+ active layer, and an ohmic electrode formed in contact with the n+ active layer, the transistor having a drain region side. a drain formed on the n-type active layer, at least a part of the surface of which is covered by the ohmic electrode, and electrically connected to the n+ active layer;
A Schottky metal layer is provided.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the invention.

In FIG. 1, an n-type active layer and an n+ active layer are formed in the drain and source regions on a semi-insulating gallium arsenide substrate 1 by ion implantation. Next, after forming a tungsten silicide layer on the entire surface, an electrode 4 is formed on the gate 1 made of tungsten silicide on the top of the n-type active layer 2 by dry etching, and at the same time, the n-type active layer 2 and the n+ type active layer on the train side are formed. A drain Schottky metal layer 5 is formed near the boundary of 3. And gate electrode 4
After forming a passivation film 7 made of SiO□ covering the
An ohmic electrode 6 made of uGe.Ni is formed and alloyed. At this time, the ohmic electrode 6 on the drain side is formed so as to overlap the top of the previously formed Train Schottky metal layer 5. Thereafter, a source electrode 8 and a drain electrode 8A are formed to complete a Schottky junction field effect transistor.

In the first embodiment configured in this way, the drain connection is a Schott I-key connection on the side closer to the gate electrode 4, so the resistance is higher than that of an ohmic connection.
Furthermore, since the drain Schottky metal layer 5 is processed by dry etching, the edge portion on the gate 1-electrode side is processed less than when the ohmic electrode 6 is formed using only the lift-off method to form a train connection. Roughness has decreased, and electric field concentration points (hot spots) are less likely to form. Therefore, the breakdown voltage between the drain and gate is improved.

FIG. 2 is a sectional view of a second embodiment of the invention.

In this second embodiment, an n-type active layer 2 is formed on a gallium arsenide substrate 1 by ion implantation, epitaxial growth, etc.
A Schottky metal is grown thereon, and then a gate electrode 4 and a drain Schottky metal layer 5 are simultaneously formed by dry etching. Thereafter, an n'' type active layer 3 is formed by epitaxial growth, and at this time, the n1 type active layer 3 on the drain side is grown in a self-aligned manner with respect to the drain Schottky metal layer 5.The subsequent process is performed in the first embodiment. Similar to the example.

In the second embodiment configured in this way, the short channel effect does not occur because it is formed on the n+ type active layer 3 or the n type operating layer 2 and is connected to the drain Schottky metal layer 5. , and has the advantage that the withstand voltage between the gate and drain is improved.

〔Effect of the invention〕

As explained above, the present invention provides a Schottky junction field effect transistor on which the n-type active layer on the drain side is covered at least a part of the surface with an ohmic electrode and is electrically connected to the n+ active layer. By providing the drain Schottky metal layer, the breakdown voltage between the gate and drain can be improved.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of first and second embodiments of the present invention, and FIG. 3 is a cross-sectional view of an example of a conventional Schottky junction field effect transistor. DESCRIPTION OF SYMBOLS 1... Gallium arsenide substrate, 2... N-type operating layer, 3...
... n+ active layer, 4... gate electrode, 5... drain Schottky metal layer, 6... ohmic electrode,
7... Passivation film, 8... Drain electrode,
8A...source electrode.箭i'Il - 恭itsu

Claims (1)

[Claims] In a Schottky junction field effect transistor having an n-type active layer and an n^+ active layer formed on a semi-insulating substrate, and an ohmic electrode formed in contact with the n^+ active layer, the drain A drain Schottky metal layer is formed on the n-type active layer on the region side, at least a part of the surface is covered with the ohmic electrode, and is electrically connected to the n^+ active layer. A Schottky junction field effect transistor characterized by: