JPH03166745A - Evaluating method for field effect transistor - Google Patents

Abstract

PURPOSE:To select a suitable current value and to perform an acceleration test by a DC by supplying a reverse DC current between gate and drain electrodes. CONSTITUTION:A first breakdown voltage BVgd1 between the gate and drain electrodes of a GaAs Schottky barrier type field effect transistor (GaAsFET) is first measured. Then, a current flowing between the gate and drain electrodes is then increased, and a reverse current is continued for predetermined time. Again, a second breakdown voltage BVgd2 between the gate and drain electrodes of the GaAsFET is measured. A field effect transistor can be evaluated from variation amount (BVgd1-BVgd2) between the first and second breakdown voltages. Thus, a decrease in the breakdown voltage between the gate and drain electrodes can be measured by a simple device of supplying the DC current.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for manufacturing field effect transistors, particularly for G a A where excessive high frequency input is expected.
s Schottky barrier field effect transistor (hereinafter referred to as
The present invention relates to a method for evaluating the reliability of G.A.S.F.E.T.

[Conventional technology]

GaAsFET requires reliability evaluation against excessive high frequency input. Conventionally, G a As F E T using high temperature continuous high input tests, high temperature high pulse input tests, etc.
Reliability is evaluated by measuring changes in the characteristics of

Among the characteristics of GaAsFET, measurement of breakdown voltage, which defines the maximum output of high-frequency power, is important as an evaluation item. This breakdown voltage BVgd is GaA
It is defined as the gate-drain voltage when the source electrode of the sFET is open and a predetermined reverse current (usually about several hundred μA per 1 mm of gate width) is passed between the gate and drain electrodes.

In particular, when the QaAsFET is operated for more than several thousand hours with excessive high frequency input, the breakdown voltage BVgd
is known to decrease. For this reason, GaAsF
For quality assurance of ET and evaluation of manufacturing process, a test to evaluate such a decrease in breakdown voltage BVgd is required.

[Problem to be solved by the invention]

However, in these tests, GaAsFETs assembled into amplifiers and tuned to a relatively good matching condition were tested.
In order to conduct a test in which a pulsed wave or continuous wave high frequency excessive power input is maintained for a long period of time at a constant high temperature,
Expensive testing equipment was required, and testing took several thousand hours. In addition, there were other problems such as the large amount of effort required to prepare for the exam.

The present invention solves the above-mentioned drawbacks and provides an evaluation method that can test the decrease in breakdown voltage BVgd caused by excessive high-frequency input of GaAs FET in a short time using a simple test device. It is intended to.

[Means to solve the problem]

The method for evaluating a field effect transistor according to the present invention includes a first step of measuring a breakdown voltage between the gate and drain electrodes of a field effect transistor using a Schottky barrier gate; A second step of flowing a predetermined reverse current between the electrodes for a predetermined time, and again flowing the gate of the field effect transistor.
A third step of measuring the breakdown voltage between the drain electrodes, and evaluating the field effect transistor from the amount of change between the breakdown voltage in the first step and the breakdown voltage in the third step. That is.

In addition, the magnitude of the reverse direction current flowing between the gate and drain electrodes in the second step needs to be selected within a range that does not cause electromigration of the gate electrode, and is approximately 2 mA/mm (0 .5mA
/'mm or more and 10mA/mm or less) is suitable.

[Effect]

The present invention is based on the knowledge that when excessive high-frequency power is input to a GaAsFET, deterioration occurs due to a reverse current flowing between the gate and drain electrodes, and the breakdown voltage between the gate and drain mainly deteriorates. ing. Therefore, by passing a direct current in the opposite direction between the gate and drain electrodes, an effect similar to that obtained when excessive high-frequency power is applied manually is produced, and by selecting an appropriate current value, accelerated testing using direct current becomes possible.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

GaAsFE using Schottky barrier gate using QaAs semiconductor as field effect transistor
Evaluate T. The gate width of this GaAsFE' is 28
It is 0 μm.

First breakdown voltage BVg between the gate and drain electrodes of a GaAsFET manufactured by a predetermined manufacturing process
dl is first measured.

To measure the breakdown voltage, connect a constant current source between the gate electrode and source electrode of the GaAsFET,
A reverse current of A is caused to flow, and the voltage between the gate and drain electrodes at this time is measured and taken as the breakdown voltage BVgd. Note that at this time, the source electrode is not connected and is open.

Next, the current flowing between the gate and drain electrodes is 0.5 mA.
The reverse current is continued to flow for 30 minutes. This reverse current is about 1.8 mA per 1 mm of gate width.

Again, the second electrode between the gate and drain electrodes of the GaAsFET
Measure the breakdown voltage BVgd2.

The above field effect transistor can be evaluated from the amount of change (BVgd 1 - BVgd2) between the first breakdown voltage and the second breakdown voltage. The above rating is about 30
It will be finished in minutes.

As a comparative example, the conventional method is 120°C at an ambient temperature of 95°C.
The amount of change in breakdown voltage between the gate and drain electrodes (the amount of change before and after performing the high temperature continuous input test) when a 0 hour high temperature continuous input test was performed was measured.

G a As of the same lot between the measurement result of the amount of change by this conventional method and the measurement result of the amount of change by the example of the present invention.
The correspondence in FET is shown in Figure 1.

As is clear from this figure, the measurement results obtained by both methods are highly correlated.

Therefore, if the correspondence between the high-temperature, high-continuous input test and the test of the present invention is established in advance, reliability evaluation against excessive high-frequency input can be performed in a few thousandths of the time by the evaluation according to the present invention.

[Effects of the Invention] As explained above, the evaluation method according to the present invention includes the first step of measuring the breakdown voltage between the gate and drain electrodes of a field effect transistor using a Schottky barrier gate, and a second step of flowing a predetermined reverse current for a predetermined time between the gate and drain electrodes of the field effect transistor; a third step of again determining the breakdown voltage between the gate and drain electrodes of the field effect transistor; The field effect transistor is evaluated from the amount of change between the breakdown voltage in the first step and the breakdown voltage in the third step.

Therefore, the present invention can reduce the breakdown voltage between the gate and drain electrodes, which is an important evaluation of the reliability of transistors, by using a simple device that flows a direct current, and can reduce the drop in breakdown voltage between the gate and drain electrodes by a factor of several thousand. Can be measured in a short time.

[Brief explanation of the drawing]

Figure 1 is for explaining the correspondence between changes in breakdown voltage between this example and the conventional method, with the horizontal axis showing the amount of change due to the conventional method, and the vertical axis showing the amount of change due to this example. .

Claims (1)

[Claims] A first step of measuring the breakdown voltage between the gate and drain electrodes of a field effect transistor using a Schottky barrier gate, and flowing a predetermined reverse current between the gate and drain electrodes of the field effect transistor for a predetermined period of time. a second step; a third step of again measuring the breakdown voltage between the gate and drain electrodes of the field effect transistor; and a breakdown voltage in the first step and the breakdown voltage in the third step. A method for evaluating a field effect transistor, characterized in that the field effect transistor is evaluated from the amount of change in the field effect transistor.