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Picoampere Current Source and Measuring Circuit

IP.com Disclosure Number: IPCOM000084038D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hohl, JH: AUTHOR [+2]

Abstract

This test circuit provides a simple and fast method for forcing and measuring very low currents in integrated circuit devices. The circuit is suitable for automatic testing and provides little risk of device damage.

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Picoampere Current Source and Measuring Circuit

This test circuit provides a simple and fast method for forcing and measuring very low currents in integrated circuit devices. The circuit is suitable for automatic testing and provides little risk of device damage.

The circuit is intended particularly for investigation of gate insulator breakdown mechanisms, which represent one of the most critical reliability exposures for field-effect transistor (FET) circuits. Traditionally, gate insulators have been stressed with constant voltage. When breakdown occurred, the dielectric was burned out and failure analysis would only reveal the local destruction of the dielectric, without any clues of the process which had led to the breakdown in the first place.

The current source of this circuit allows the observation of the developing phases of dielectric breakdown. The circuit has a current range of picoamperes to milliamperes over a wide voltage range.

In operation, a device 10, for example a metal-oxide semiconductor (MOS)FET, to be tested is connected between terminals A and B which may be a test socket or voltage probe tips. Initially, the gate of the device 10 is brought to ground potential and capacitor C1 is discharged through transistor T1, in response to a START pulse. At the same time, a predetermined input voltage - Vin, corresponding to a particular value of current desired to be applied across the device 10, is applied through resistor R4 to the noninverting inp...