Onset and recovery of electrical instabilities in conducting double-layer dielectric films

The onset and recovery of threshold voltage shift induced in parasitic metal-insulator-semiconductor field-effect transistors by bias-temperature stress in the presence of thick conducting double-layer dielectric films is investigated as a function of the stress conditions. It is found that the threshold voltage shift, which depends on the conductance difference between the two dielectric layers as well as the stress voltage and temperature, is reversible. Moreover, the threshold voltage shift recovers back to its original value when the bias is removed. The result demonstrates that the electrical instability is not caused by stress-induced damage but by the enhanced conduction of charges in the dielectric layers and the consequent trapping of charges inside the nitride and/or at the nitride/oxide interface. The recovery to initial threshold value is explained by charge detrapping on neutral traps. (C) 2004 The Electrochemical Society.