Sylvain Garaud

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Capacitance vs. time (c-t) characteristics of a MOS structure show the capacitance change after a pulse bias is applied which drives the structure first into accumulation then into deep inversion. Since the time constant of minority carrier generation is relatively long, the MOS structure requires time to reach equilibrium after the pulse bias is applied. Immediately after the pulse bias is applied, the depletion layer extends more widely then the depletion layer becomes narrower - the MOS structure approaches equilibrium as more and more minority carriers are generated. Finally, the depletion layer reaches its equilibrium width. This proves charge neutrality. The C-t characteristics are obtained from this change in the depletion layer width. During this project, capacitance vs. time measurements were made using an external bias source. The system consists of a probe station located within a dark box, a Keithley K182 system and a ICS metrics software. The measured capacitance-time (C-t) data were converted into a Zerbst plot using the Zerbst equation. The effective generation lifetime (τg,eff) and the surface generation velocity (seff) were extracted from the slope and the intercept of the Zerbst plot. The main problem with this technique is that times of hundreds or even thousands of seconds per measurement are not uncommon. One method of optical excitation to reduce this measurement time was investigated. We have achieved our goal: setup the pulsed MOS capacitor recombination lifetime measurement technique in the JUT test area. Besides this project did not require the purchase of hardware or additional software. Finally we have shown that the total measurement time was significantly reduced by illumination and there was virtually no error compared to the curve recorded entirely in the dark.

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