Positive charge instability during bidirectional stress on metal–oxide–silicon capacitors

Abstract

Bidirectional electron injections are made on metal–oxide–silicon capacitors under constant currents or constant voltages. It is shown that both stresses reveal the same generation mechanism of oxide defects and consequently confirm that the gate/oxide interface is more stress resistant than the oxide/silicon interface. It is also shown that the created positive charge is unstable during bidirectional stress. We characterize this instability by studying dielectric defect neutralization following a new procedure. Oxide field intensity and polarity are considered as the principal precursors of this instability. Without any applied field, the neutralization follows a logarithmic law; while under a nonstressing field it follows an exponential law. Both kinetic laws are linked, since the logarithmic law describes the saturation value of the exponential one, and hence both describe the same process. Results of both current and voltage stresses give a power law between the oxide field near the cathode during stress and the capture cross section measured from neutralization kinetics.