JPH07130762A - Multifinger-type field effect transistor - Google Patents

Abstract

PURPOSE:To reduce a source inductance by a method wherein a belt-shaped electrode which is electrically connected to the respective tip parts of source electrode finger parts and a source electrode extraction part through through- holes in an insulating film provided on it is formed on a semiconductor substrate. CONSTITUTION:Gate electrode finger parts 2 which are arranged into a comb shape on a semiconductor substrate 1 and drain electrode finger parts 3 and source electrode finger parts 4 which are arranged into comb shapes respectively so as to face each other with the gate electrode finger parts 2 therebetween are provided. In a multifinger-type FET like this, a belt-shaped electrode 5 which is electrically connected to the respective tip parts of the source electrode finger parts 4 and a source electrode leading part 4a through through-holes 7 in an insulating film 6 provided on it is formed on the semiconductor substrate 1 below the respective tip parts of the source electrode finger parts 4. With this constitution, routes from the tip parts of the source electrode finger parts 4 to a grounding terminal can be shortened, so that a source inductance can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-finger type field effect transistor (hereinafter referred to as multi-finger FET).

[0002]

2. Description of the Related Art A conventional multi-finger FET is shown in FIG.
As shown in FIG. 2, a gate electrode finger portion 2 arranged in a comb-teeth shape on an active layer formed on a semi-insulating GaAs substrate, and a drain electrode finger portion 3 facing each other with the gate electrode finger portion 2 interposed therebetween. Source electrode finger portions 4 and gate electrode lead-out portions 2a, drain electrode lead-out portions 3a, source electrode lead-out portions 4a respectively connected to these.
And the source electrode lead-out portion 4a and the back surface electrode were connected to each other through the via hole 9 provided in the semi-insulating GaAs substrate and grounded.

In the microwave band and millimeter wave band FETs, when the finger length becomes long, the high frequency characteristics are deteriorated due to the phase shift at the gate electrode fingers, the non-uniformity of the channel temperature is increased, and the material of the active layer is processed. Since problems such as a decrease in gain due to an increase in non-uniformity occur, a multi-finger structure is generally used to increase the gate width.

Usually, when a circuit such as an amplifier is constructed, a grounded source circuit which has a high input impedance and a high gain is often used, but it is known that the gain is lowered when the source inductance is large. ing.

[0005]

In this conventional multi-finger FET, since nothing is connected to the tip of the source electrode finger portion and it is open, the path from the tip of the source electrode finger portion to the ground end is There is a problem that the inductance becomes longer and the inductance in this section is not reduced.

[0006]

A multi-finger FET according to the present invention is arranged in a comb-teeth shape so as to face a gate electrode finger section arranged in a comb-teeth shape on a semiconductor substrate with the gate electrode finger section interposed therebetween. In a multi-finger type field effect transistor having a drain electrode finger portion and a source electrode finger portion, the insulating film is formed on the semiconductor substrate below each tip of the source electrode finger portion and through a through hole of an insulating film provided thereon. And a strip-shaped electrode electrically connected to each tip of the source electrode finger portion and each of the source electrode lead portions.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

1A and 1B are a plan view and a sectional view taken along the line AA 'of a semiconductor chip showing an embodiment of the present invention.

As shown in FIGS. 1A and 1B, a gate electrode finger portion 2 having a Schottky junction on the surface of an active layer formed on a semi-insulating GaAs substrate 1 and having a comb-teeth shape. And a drain electrode finger portion 3 and a source electrode finger portion 4 which are opposed to each other with the gate electrode finger portion 2 sandwiched therebetween, and on the surface of the semi-insulating GaAs substrate 1 on the lower surface of each tip of the source electrode finger portion 4. A strip electrode 5 made of a gold film or the like, which is isolated from the active layer and intersects each tip of the source electrode finger portion 4 and each of the drain electrode finger portions 3, is formed and provided on the insulating film 6 formed on the strip electrode 5. The strip electrodes 5 are connected to the source electrode finger portions 4 and the source electrode lead portions 4a via the through holes 7. It should be noted that the gate electrode finger portion 2 is provided on the opposite side of the drain electrode lead portion 3a connected to the drain electrode finger portion 3 and led to the tip side of the gate electrode finger portion 2 and the source electrode finger portion 4.
Is formed on the back surface of the semi-insulating GaAs substrate 1 by forming a gate electrode lead-out portion 2a connected to the source electrode lead-out portion 4a connected to the source electrode finger portion 4a via an insulating film. Is connected to the source electrode lead-out portion 4a through a via hole (not shown) formed in the semi-insulating GaAs substrate 1 on which the back surface electrode 8 is formed.

FIGS. 2A and 2B are an equivalent circuit diagram showing the source inductance of one embodiment of the present invention and an equivalent circuit diagram showing the source inductance of a conventional field effect transistor.

As shown in FIG. 2A, according to the embodiment of the present invention, the shortest path from the point A to the ground is the path passing through the inductors 51-32, but as shown in FIG. In the conventional example, the shortest path from the point A to the ground is the path passing through the inductance 41-21-31, and the present invention can be shortened because it does not pass the inductance 41 of the source electrode finger portion, and the source inductance can be reduced.
Similarly, the shortest path from the point B or C to the ground can be shortened because the source electrode finger portion is not passed in the present invention, and the source inductance can be reduced.

In this embodiment, the tip of the source electrode is connected by the strip-shaped electrode provided in the layer below the drain electrode, but the same effect can be obtained by using the air bridge wiring extending over the drain electrode.

[0013]

As described above, according to the present invention, by connecting the tips of all the source electrode finger portions of the multi-finger FET to the source electrode lead portions, the source electrode lead portions are grounded from the tip of the source electrode finger portions. This has the effect that the path to the end can be shortened and the source inductance can be reduced by 30 to 70%.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view taken along the line AA ′ of a semiconductor chip showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram showing a source inductance of one embodiment of the present invention and an equivalent circuit diagram showing a source inductance of a conventional example.

FIG. 3 is a plan view showing an example of a conventional multi-finger FET.

[Explanation of symbols]

 1 semi-insulating GaAs substrate 2 gate electrode finger portion 2a gate electrode lead-out portion 3 drain electrode finger portion 3a drain electrode lead-out portion 4 source electrode finger portion 4a source electrode lead-out portion 5 strip electrode 6 insulating film 7 through hole 8 back surface electrode 9 via hole

Claims (1)

[Claims] 1. A gate electrode finger portion arranged in a comb tooth shape on a semiconductor substrate, and a drain electrode finger portion and a source electrode finger portion arranged in a comb tooth shape facing each other with the gate electrode finger portion sandwiched therebetween. In a multi-finger type field effect transistor, each tip of the source electrode finger portion and the source electrode are formed through a through hole of an insulating film formed on the semiconductor substrate below each tip of the source electrode finger portion and provided on the semiconductor substrate. A multi-finger type field effect transistor characterized in that a strip-shaped electrode electrically connected to each of the lead-out portions is provided.