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Low Current and Capacitance Measurement Technique

IP.com Disclosure Number: IPCOM000084428D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

El-Kareh, B: AUTHOR [+2]

Abstract

This technique allows manual or automated measurement of current and capacitance, particularly on small geometry elements of integrated circuits. It is best suited for measurement of current in the subpicoamp range and capacitance in the picofarad range.

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Low Current and Capacitance Measurement Technique

This technique allows manual or automated measurement of current and capacitance, particularly on small geometry elements of integrated circuits. It is best suited for measurement of current in the subpicoamp range and capacitance in the picofarad range.

The current is inferred from the instantaneous voltage delay rate and device capacitance as: I - C(V) . dV/dt where C(V) is the voltage dependent total capacitance of the structure.

Because of the extremely low value of units involved, the measurements should be carried out in an AC and light-shielded enclosure and well-controlled environment.

A typical parameter important in integrated circuits is the reverse bias leakage of a PN junction or Schottky barrier diode. The diode is represented in its equivalent circuit form as the device under test between points A and B in the figure. The diode leakage current I is a function of reverse bias applied between A and B.

In order to determine I at any particular reverse bias voltage, the total capacitance C (V) must be measured. The capacitance is measured using the voltage division method. The input voltage Vin is varied by Delta Vin after the initial bias has been applied to the diode and switch 10 has been opened. This results in a variation in the output voltage Delta Vo across the load capacitance CL.

Switch 10 is a very high-impedance, low-capacitance switch such as a reed relay. The output voltage can be measured...