JP2703561B2 - Breakdown voltage measurement method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring a breakdown voltage of a semiconductor device or the like with high accuracy.

[Technical background of the invention and its problems]

There are two important voltage values when measuring the breakdown voltage of a semiconductor device or the like. One is a voltage at which the DUT causes a breakdown phenomenon when the voltage applied to the device under test (DUT) is increased (referred to as a breakdown trigger voltage, hereinafter abbreviated as a trigger voltage).
First, when the applied voltage to the DUT where the breakdown phenomenon occurs is gradually reduced, the voltage at which the breakdown phenomenon stops (the breakdown current is zero at this time) (called the breakdown / latchback voltage). , Hereinafter abbreviated as latchback voltage).

Conventionally, a measuring circuit having a configuration as shown in FIG. 3A has been used to measure such a trigger voltage and a latchback voltage. The measurement was performed by the pulse generator 301 on the DUT101.
A pulse signal is applied, and the current flowing through the DUT 101 is passed through the current probe 302 and the terminal voltage V
This is done by connecting d directly to each channel input of the oscilloscope 303 and observing their waveforms. Third
FIG. 6B shows these measured waveforms. It can be seen that the trigger voltage and the latchback voltage are measured respectively.

However, this measurement method has several disadvantages. First, at the time of the breakdown phenomenon, a large amount of current flows through the DUT, and the DUT may be destroyed by thermal or electrical stress. Particularly, in recent years, individual semiconductor elements used for ICs and the like tend to be increasingly smaller in recent years, and are therefore susceptible to thermal and electrical stress. Also, DUT by current
The temperature of the DUT itself rises due to the heat generation of the DUT, and the characteristic of the DUT changes, so that accurate measurement cannot be performed. Furthermore, observation of such a breakdown phenomenon requires a high-speed waveform observation of about 0.1 μsec, so that the measurement system becomes expensive.

[Object of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a measurement method which can be performed by an inexpensive measurement system in which a thermal stress applied to a DUT in a breakdown voltage measurement is small, and thus a measurement error due to a change in characteristics of the DUT is small.

[Summary of the Invention]

According to an embodiment of the present invention, a constant current source is used to apply a constant current smaller than a breakdown current to a DUT.
The trigger voltage and the latch-back voltage are measured by observing the waveform of the inter-terminal voltage of the above with a waveform observer.

When a constant current I is applied from the constant current source to the DUT, the stray capacitance C between the terminals of the DUT is charged, so that the voltage between the terminals of the DUT increases with time at a constant gradient (I / C).

At this time, if the constant current I is set to a value lower than the breakdown current in advance, when this voltage reaches the trigger voltage, a breakdown current flows, causing a current supply shortage of the current source, and the voltage between the terminals of the DUT decreases. start. When this voltage falls to the latchback voltage, the breakdown phenomenon stops, and the breakdown current becomes zero, so that the voltage between the terminals of the DUT starts increasing with time again at the slope of I / C. This operation is repeatedly performed. When this state is observed with an oscilloscope or the like, the waveform is observed as a saw-tooth wave. The voltage at the peak is the trigger voltage, and the voltage at the valley is the latchback voltage, whereby the breakdown voltage is measured. With such a configuration, an excessive current does not flow through the DUT, so that the thermal stress applied to the DUT is reduced, the characteristic change of the DUT itself due to heat generation is reduced, and the measurement error is also reduced. Furthermore, since a low-speed object can be used for the waveform observer, an inexpensive measurement system can be configured.

(Example of the invention)

One embodiment of the present invention is shown in FIG. As can be seen, a constant current I is applied to the DUT 101 by a constant current source 102. This current I charges the stray capacitance C between the terminals of the DUT 101, so that the voltage between the terminals of the DUT 101 increases with time at a slope of I / C. When this voltage reaches the trigger voltage, the DUT 101 causes a breakdown phenomenon, and the breakdown current tends to flow rapidly, but if the constant current I is set in advance to a predetermined value lower than the breakdown current, the DUT 101 The voltage between terminals will start to drop. When this voltage decreases and becomes the latchback voltage, the breakdown phenomenon stops and the breakdown current stops flowing, so that the voltage between the terminals of the DUT 101 rises again with the I / C slope. This operation is repeatedly performed, and a time-varying sawtooth wave is generated. The measurement of the trigger voltage and the latchback voltage is performed by observing the voltage between terminals of the DUT 101 using the waveform observing device 103 such as an oscilloscope, and observing the above-mentioned sawtooth wave. That is, the peak voltage of the sawtooth wave is the trigger voltage, and the trough voltage is the latchback voltage. This is shown in FIG. 1 (b). Note that the constant current source 102 functions as a constant current source up to a voltage region higher than the breakdown voltage of the DUT 101.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the DUT 101 has a terminal opposite to the constant current source 102 at the constant voltage source 2.
Connected to 01. The measurement is performed by gradually increasing the size of the constant voltage source 201 until a breakdown phenomenon occurs. In this case, a negative voltage whose absolute value gradually increases is applied to one end of the DUT 101. Before the breakdown phenomenon occurs, the current flowing through the DUT is smaller than the constant output current I of the constant current source 102, so that the constant current source 102 is saturated. When the DUT 101 causes a breakdown phenomenon, the constant current source 102 operates to generate the sawtooth wave as described above. This sawtooth wave is used for waveform observation 103
And the breakdown voltage is measured from the voltage of the peak and the voltage of the valley and the output voltage of the constant voltage source 201 at this time. In this circuit, the constant current source 102 and the waveform observer 1
The dynamic range required for 03 can be reduced.

In the above embodiment, the waveform observer 103 can also measure the trigger voltage and the latchback voltage by using a peak detector and a voltmeter instead of the oscilloscope.

〔The invention's effect〕

As described above, by using the present invention, DU
It is possible to measure a breakdown voltage of a semiconductor element or the like with an inexpensive measurement system in which thermal stress applied to T is small and errors due to change in characteristics of the DUT are small.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 1 (a) is a diagram showing the configuration, and FIG. 1 (b) is a waveform diagram for explaining the operation. FIG. 2 is a diagram showing another embodiment of the present invention, FIG. 3 is a diagram showing a conventional breakdown voltage measuring circuit, (a) is a diagram showing the configuration, and (b) is a waveform observed. FIG. 101: DUT, 102: constant current source 103: waveform observer, 201: constant voltage source

Claims (2)

(57) [Claims] 1. A device under test, a current source applied to the device under test and having an output current set to a current value lower than a breakdown current value to flow through the device under test, Measuring means for measuring a voltage between terminals of a measuring device, wherein the measuring means measures a breakdown trigger voltage and a brake-down / latch-back voltage of the device under test. Measuring method. 2. A device under test, and a current source applied to one end of the device under test and having an output current set to a current value lower than a breakdown current value to flow through the device under test, Using a voltage source capable of adjusting a set voltage applied to the other end of the device under test, and measuring means for measuring the voltage at the one end of the device under test,
A breakdown voltage measuring method, comprising: measuring a breakdown trigger voltage and a breakdown / latchback voltage of the device under test by the measuring means.