JPS6348869A - Semiconductor device - Google Patents

Abstract

PURPOSE:To suppress a leaking current between a gate and a drain and to improve the withstanding voltage of the gate and the withstanding voltage of the drain, by forming an insulating film between a rear surface electrode and a substrate. CONSTITUTION:A high frequency signal is inputted to a source lead line 10, which is connected to a source electrode 4, by way of a gate lead line 12 having a source inductance L1. The amplified high frequency signal is outputted from a drain electrode 5 by way of a drain lead line 11 having a drain inductance L2. A gate parasitic capacitor C1 and a drain parasitic capacitor C2 are present between a rear surface electrode 7 and a gate electrode 6 and the drain electrode 5 through a semi-insulating GaAs substrate 2 and an insulating film 13. Since the insulating film 13 is formed between the lower surface of the semi- insulating substrate 2 and the rear surface electrode 7, no parasitic resistor is generated between the rear surface electrode 7 and the gate electrode 6 and between the electrode 7 and the drain electrode 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor device mainly used as an amplification element in a microwave band, and particularly to a GaAs field effect transistor (hereinafter abbreviated as GaAsFET).

[Conventional technology]

FIG. 3 is a cross-sectional view showing an example of a conventional GaAsFET. In this figure, 1 is a GaAsFET.

2 is a semi-insulating GaAs substrate; 3 is the semi-insulating GaAs substrate;
Active layers 4 and 5 formed on the substrate 2 by ion implantation, etc.
6 is a gate electrode having an ohmic contact with the active layer 3; 7 is a gate electrode formed on the other main surface of the semi-insulating GaAs substrate 2; This is the back electrode.

Then, the GaAsFET 1 is soldered to the carrier 8 using a solder material 9, and the source electrode 4 is connected to the source lead wire 10, and the drain electrode 5 is connected to the drain lead wire 11.
The gate electrode 6 is connected to an external electrode via a gate lead wire 12.

When the GaAsFET 1 is used as a microwave band amplifier, the back electrode 7 of the GaAsFET 1 is electrically connected to the source lead wire 10 and grounded.

The drain electrode 5 is kept at a positive potential via a drain lead wire 11, and the gate electrode 6 is kept at a negative potential via a gate lead wire 12. A high frequency signal is applied to the gate electrode 6, and amplification is achieved by obtaining the high frequency signal amplified from the drain electrode 5.

FIG. 4 is a high frequency equivalent circuit diagram of the GaAsFET 1 shown in FIG. In this figure, the same symbols as in FIG. 3 indicate the same parts, LL is the source inductance, R2 is the drain inductance, R3 is the gate inductance, C1 is the gate parasitic capacitance, C2 is the drain parasitic capacitance, R1 is the gate parasitic resistance, R2 is the drain parasitic resistance.

In this circuit, a source lead wire 10 connected to the source electrode 4 is grounded via a source inductance L1, and a high frequency signal is input to the gate electrode 6 via a gate lead wire 12 having a gate inductance of 3. ,
An amplified high-frequency signal is output from the drain electrode 5 via a drain lead R11 having a drain inductance L2. The gate electrode 6 and the drain electrode 5 have a gate parasitic capacitance C4, a drain parasitic capacitance C2, a gate parasitic resistance R□, a drain parasitic resistance R2, etc. between the gate electrode 6 and the drain electrode 5, respectively, with the back surface S pole 7 via the semi-insulating GaAs substrate 2. exists.

[Problem that the invention seeks to solve]

In the conventional GaAsFET1 as described above, since there is a gate parasitic resistance R1 and a drain parasitic resistance R2, when used as an amplifier, this becomes a cause of leakage current, leading to a decrease in gate withstand voltage and drain withstand voltage in DC operation. Moreover, this leads to an increase in current consumption, and in high-frequency operation, this leads to a decrease in gain and output due to leakage of input and output signals, which impairs the original performance of the GaAsFET.

The present invention has been made to solve these problems, and provides a semiconductor device that can suppress gate and drain leakage currents, improve gate and drain breakdown voltages, and improve gain and output. With the goal.

[Means for solving problems]

A semiconductor device according to the present invention has an insulating film formed between a back electrode and a substrate.

[Effect]

In this invention, the substrate and the back electrode are insulated, and there is no gate parasitic resistance or drain parasitic resistance.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the semiconductor device of the present invention. In this figure, the same reference numerals as in FIG. 3 indicate the same parts, and 13 is an insulating film formed between the semi-insulating G&As substrate 2 and the back electrode 7, which is made of SiN, Sin, 5iON, etc.

A high frequency signal is input to a source lead wire 10 connected to the source electrode 4 via a gate lead wire 12 having a source inductance L1, and a high frequency signal is input from the drain electrode 5 to a drain lead wire 11 having a drain inductance L2.
The amplified high-frequency signal is output through the . Day 1~
The electrode 6 and the drain electrode 5 are each made of semi-insulating Ga.
A gate parasitic capacitance C□ and a drain parasitic capacitance C2 exist between the As substrate 2 and the back electrode 7 via the insulating film 13. However, since the insulation yA13 is formed between the lower surface of the semi-insulating GaAs substrate 2 and the back electrode 7, parasitic resistance does not occur between the back electrode 7 and the gate electrode 6 and between the drain electrode 5. , its high frequency equivalent circuit diagram is shown in the second
The result will be as shown in the figure.

In the above embodiment, an example was explained in which the insulating film 13 was interposed between the GaAsFET and the back electrode 7 of the semi-insulating GaAs substrate 2, but a monolithic microwave IC (MM) using GaAs instead of the GaAsFET was explained.
IC) may also be used, and the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As explained above, in this invention, since an insulating film is formed between the back electrode and the substrate, leakage current between the gate electrode or drain electrode and the back electrode can be prevented, and the gate breakdown voltage can be increased.
This has the effect of improving drain breakdown voltage and improving gain and output.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the semiconductor device of the present invention, FIG. 2 is a high frequency equivalent circuit diagram of the semiconductor device shown in FIG. 1, and FIG. 3 is a sectional view showing an example of a conventional GaAsFET. FIG. 4 is a high frequency equivalent circuit diagram of the GaAsFET shown in FIG. 3. In the figure, 1 is a GaAsFET, 2 is a semi-insulating GaA
s substrate, 3 is an active layer, 4 is a source electrode, 5 is a drain electrode, 6 is a gate electrode, 7 is a back electrode, 8 is a carrier, 9
1 is a solder material, 10 is a source lead wire, 11 is a drain lead wire, 12 is a gate lead wire, and 13 is an insulating film. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa (2 people) Figure 1, Figure 2

Claims (1)

[Claims] A semiconductor device in which an active element is formed on one main surface of a substrate and a back electrode is formed on the other main surface, characterized in that an insulating film is formed between the back electrode and the substrate. .