Development of a Fast Technique for Characterizing Interface States

Abstract

Characterizing interface states is an important task for test engineers. The existing techniques typically have a measurement time in the order of seconds. Recent results, however, show that degradation can recover substantially within seconds and there is a need for improving the speed for measuring interface states. The central task of this work is to reduce the time for measuring interface states to the order of microseconds, so that the recovery during measurement can be minimized. An analysis of the existing techniques ruled out the popular techniques, such as conductance, various capacitance-voltage methods and the subthreshold swing, since they all require a gate voltage ramp that must be slow enough to maintain thermal equilibrium with interface states. Although conventional charge pumping (CCP) does not require such equilibrium, the DC recombination current used limits the speed. By replacing the DC current with transient currents, we will show that interface states can be extracted from a single pulse applied to the gate, allowing the measurement time being reduced to the order of microseconds. The results are calibrated against those from the well-established technique and accuracy in the order of 10 10 cm -2 is achieved.