JPS58129266A - Measuring device for micro current - Google Patents

Abstract

PURPOSE:To eliminate errors by fluctuations in the amplification factor of an amplifier and to measure micro currents such as leak currents of semiconductors with good stability and accuracy by comparing the micro current to be measured and reference current and measuring the difference thereof. CONSTITUTION:Leak current il to be measured is supplied to the inversion input terminal of an operational amplifier 21. The voltage signal which increases gradually from 0V is generated from a reference voltage generator 20, and reference current ig is increased gradually. In this case, right after the start of measurement, the current il is larger than the current ig, and the output signal of the amplifier 21 is negative. The negative output signal thereof is outputted to a control line E. Right after the voltage of the generator 20 rises to ig=il and further to ig>il, the output signal of the amplifier 21 inverts positive, and the output voltage of the generator 20 at this moment is sampled and held with a capacitor 27 and is read out from an output terminal B. Thus, from the relation il=iR=V/R<3>, the value of the leak current il is determind.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a microcurrent measuring device for measuring leakage current of various semiconductor elements such as transistors, ICs, and FETs.

[Technical background of the discovery]

2. Description of the Related Art Leakage current is measured in the manufacturing and management of various semiconductor devices such as transistors and IC1FETs. At this time, since the leakage current value to be measured is extremely small, the leakage current is usually amplified once using a circuit as shown in FIG. 1 and then measured. That is, the non-inverting input terminal 12 of the operational amplifier 11 is grounded, and the input terminal A
from the inverting input terminal 13 to the output terminal B via the resistor R.
Outputs a more amplified voltage. This calculation tIll-output voltage of the circuit 11. , the voltage Vl generated at the input terminal A due to the leakage current it is equal to the voltage Vl. , resistors R1 and R
, there is a leak at input terminal A from the box! 114 is detected.

[Problems with background technology]

In a microcurrent measuring device with such a configuration, the resistance R
, and R3, the increase rate of υ changes depending on the respective errors and fluctuations. The variable wheel of this increase rate is resistors R1 and R1
It has been difficult to obtain accurate and stable measurements due to the relative error of each, the sum of the fluctuations, and the sum of the fluctuations.

[Purpose of the invention]

This invention was made in view of the above points, and provides a microcurrent measuring device that stably measures leakage current with high accuracy without using an amplifier circuit that is susceptible to errors and fluctuations in resistance. This is what we are trying to provide.

[Summary of the invention]

That is, the microcurrent measuring device according to the present invention converts a voltage from a reference voltage generator that generates a calibrated voltage that gradually increases or decreases into a reference voltage that gradually increases or decreases using a voltage-current conversion means. This reference current signal is then compared with a small current to be measured, such as leakage current of a semiconductor device, using comparison means such as an operational amplifier.
1.1: Sample and hold the output voltage of the reference voltage generator when the reference current signal described above and the measured microcurrent match and read it, and find out the value of the measured microcurrent from this output voltage value. It is something to do.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows its configuration. Input terminal C is a measurement operation signal input terminal to which a constant voltage signal that rises at the start of measurement operation is supplied, and 20 is a measurement operation signal input terminal that is supplied with a constant voltage signal that rises at the start of measurement operation. When a measurement operation signal is input to terminal C, for example, A reference voltage generator generates a voltage that increases.

The output nID of this reference voltage generator 20 is connected via a resistor R to the non-inverting input of a first operational amplifier 2.1. The resistor R3 acts as a voltage-to-electricity fIt conversion means, and if the output voltage of the reference voltage generator 20 is the reference voltage V, then the reference voltage fi'a where "5IL=voltage" is operationally amplified by I! 2
Supply to 1. That is, as the reference voltage V increases, the current value i gradually increases.

Further, from the input terminal A, a leakage current 41, for example, as well as the current to be measured is fed into the inverting input terminal of the first operational amplifier 21.

That is, in the first operational amplifier 21, for example, a gradually increasing reference current i flows into the non-inverting input terminal, and a constant leakage current flit flows into the inverting input terminal. It functions as a converter that compares the magnitude and outputs a positive signal if rLz (SmJ, and a negative signal if r it > is a mouse).

The output signal of the first mm amplifier 21 is supplied to a second operational amplifier '622 which amplifies it with an appropriate gain. This second arithmetic booster 22, for example, has an inverting input end grounded,
A feed resistor R4 providing an appropriate gain is connected to the non-inverting input terminal, and the output terminal of the first operational amplifier 21 is connected to the non-inverting input terminal.

Then, the output signal of the operational amplifier 22 of the broom 2 is output to the dirt control line E.

On the other hand, the output end of the reference voltage generator 20 is further fitted into a sandal hold circuit 23. This sandal hold circuit 23 is connected to the f− on the dirt control line E mentioned above.
) Controlled by sampling control signals,
For example, configure it as follows. First, a third arithmetic multiplier 24 having a power amplifier configuration to which the signal voltage from the output 4D is supplied is provided at the first stage, and its output terminal is connected to the above-mentioned r-1
A gate 25 such as an FET analog switch or switch whose opening/closing is controlled by a control signal on a control signal line E is connected.

For example, if the dart control signal is positive, the gate 25 is open, and if the dart control signal is negative, it is closed. The output terminal of this gate 25 is connected to a resistor R6 and a capacitor 2.
7 is connected to the non-inverting input terminal of the fourth operand unit 26.

In the nine microcurrent detection devices configured in this way, the first
For example, the inverting input terminal of the operational amplifier 21 is connected to the F' to be tested.
A leakage current S1 to be measured, such as a leakage current between the drain and source when the ET is in the off state, is supplied. Then, the reference voltage generator 20 generates a voltage signal that gradually increases from OvJ, and gradually increases the current i based on the reference.
After the start of measurement, the output signal of the leakage current (t is larger than the reference voltage tlim, and the first operational term @ device 2) is negative. This negative output signal is output to f-) control line E via the second operational amplifier 22 as a negative dart control signal.

On the other hand, the reference voltage V of the reference voltage generator 20 gradually increases.
is supplied to the RT 25 in the sample hold circuit 23 via the third operational amplifier 24 of PA and FA. And pa, fan! The output is passed through the resistor R through the p-t 26 which is opened by the negative r-t control signal.
, to supply electric charge to the capacitor 27.

That is, while the r-) 25 is open, the capacitor 27 is charged with a reliability voltage corresponding to the reference voltage V mentioned above.

In this way, the voltage of the reference voltage generator 20 is increased by 1 = i
tJ, and immediately after [i mouse > izJ, the first
When the output signal of the operational amplifier 21 is absent, the output voltage V of the reference voltage generator 20 at this moment is sample-held by the capacitor 27, and an output voltage signal corresponding to the sample-held voltage is read out from the output terminal B. .

Therefore, the final output appearing at the output terminal B,
■ The value of the leakage current 41 can be determined by reading the force voltage (■) and using the relationship "1t=S凰=read". In this case, if the relationship between the voltage appearing at the output terminal B and the reference current sB is calibrated, accurate current measurement can be performed.

Such a minute current measuring device directly compares the minute current to be measured with a reference current. It is possible to completely eliminate fluctuations in the amplification rate of the intensifier itself.

Note that the reference voltage generator 20 shown in FIG. 2 can be constructed by, for example, a circuit as shown in FIG. 3. In other words, the measurement operation start signal instructing the start of measurement from terminal C is sent to the FET.
31 f-), and from the rising edge of this signal, the FF
: The capacitor of the integrating circuit consisting of the resistor 32 and capacitor 33 connected to the source of T 31? 33 with a time constant. That is, the charging voltage of the capacitor 33 gradually increases. In this case, the rate at which the reference voltage at the set pressure rises can be adjusted by resistor 32 and capacitor 33'.

The circuit shown in FIG. 44 shows another embodiment. That is, the measurement operation signal is input from the input terminal C to the AND gate 3.
The output signal of this antenna 9r-to 34 is supplied to an FET 4, which constitutes a reference voltage generator as shown in FIG.
37 y-to. And this FET 3J
An integrating circuit consisting of a resistor 32 and a capacitor 33 is connected to the source circuit of , and the output voltage of this integrating circuit is expressed as ・f,
-7 is detected by the angle 36, and the direct voltage at the output end is taken out as the reference voltage V.

This reference voltage V is connected to a resistor R3 as a voltage-current conversion means.
to the non-inverting input terminal of the operational amplifier 21 via the reference [current iB
supply. The inverting input terminal of this operational amplifier 21 has a second
Similarly to the figure, leakage current it is supplied from input terminal A and compared with reference current i11. The output signal from the performance amplifier 21 is appropriately amplified by an operational amplifier 22, and the output signal from the performance amplifier 22 is outputted to the r-to control line E as an f-) control signal. Then, this f-) control wandering number is reversed at Inno-Ni-Y35, and i1 ■ and gate 3
4 as r−)fg.

That is, during non-measurement, the signal on the dart control line E is at a low level, and therefore the AND gate 34 receives the dart signal from the inverter 35.

When a positive measurement operation signal is input from input terminal C, the output signal of ANDGOO) 34 becomes positive, and FET3
1 is turned on, and the terminal voltages of the resistor 32 and capacitor 33 gradually rise. (1) A reference voltage V which gradually rises is applied to the output 4D via the buffer amplifier 361r, and due to this reference voltage V, the voltage gradually rises to the non-inverting input terminal of the operational amplifier 2. Reference voltage Rim is 15! Stagnant.

In other words, as in the case of diagram @2, this operator @@21
The output signal of r 't > $RJ is negative as mentioned above, but ill rises and r it
Immediately after becoming ``= iB'', it switches to positive.

Therefore, the signal on the r-t control line E is
When the output signal of 1 and 1 change, and when il=imJ, the output voltage of the inverter 35 goes from high level to low level, and ff- of AND r-1-34 is closed, and the FE
Appears in the T31fyF7 status issue. In this way, the FET
31 is turned off, the supply of electric charge to the capacitor 33 is corrected, and the capacitor 3 when "1t=i凰" is
The terminal voltage of 3 is maintained. This terminal voltage is buffer un! 36 to the output end as a reference voltage V, and by reading this voltage r, 1+N of the leakage wax flow Ll can be obtained as in the 1gII actual relaxation example.

The holding means is shared by the capacitor of the integrating circuit that generates the reference voltage.

In the above embodiment, an operational amplifier is used as a comparison means for comparing the reference current iII and the measured leakage current 41, but a combination of transistors, FgT, etc. may also be used, and the The I-amplifier using the second operational amplifier 22 and the sample hold circuit 23 may also be constructed by combining other elements.

〔Effect of the invention〕

As described above, according to the present invention, the minute current to be measured is measured by comparing it with a reference current without directly comparing it. Therefore, it is possible to eliminate measurement errors caused by fluctuations in the amplification factor of the amplifier, which conventionally caused intermittent hearing, and to provide a microcurrent measuring device that can measure microcurrents such as semiconductor leakage currents stably and accurately. be able to.

[Brief explanation of the drawing]

Figure 1 shows the input St- of a conventional copying small electric control device.
2 is a circuit diagram showing a microcurrent measuring device according to one embodiment of the present invention, FIG. 3 is a circuit diagram showing a configuration example of a reference voltage generator, and FIG. 4 is a circuit diagram showing a microcurrent measuring device according to one embodiment of the present invention. It is a circuit diagram showing an example of. 20...Reference voltage generator, R1...Resistance, 21゜2
2.24.26.36...operational term l11! Vessel, 25・
...Ket, 27.33...Capacitor.

Claims (1)

[Claims] A reference voltage generator that generates a gradually changing voltage, a voltage-current conversion means that converts the voltage output of the reference voltage generator into a voltage-current to generate a reference current, and a comparison between the reference current and the minute current to be measured. A minute current characterized by the fact that the comparison means for detecting coincidence and the sample-holding means for detecting the output voltage of the reference voltage generator in correspondence with the coincidence detection of the comparison means and obtaining the measurement result are made of plates. measuring device.