Fast Detrapping Transients In High-K Dielectric Films

Charge trapping and detrapping are mechanisms which substantially modify dynamically the electric features of high-k dielectrics and cause instability of the MOS flat band voltage. The timescale on which such phenomena take place depends on the space and energy distribution of traps and in high-k dielectrics it may span on a very wide interval. On the other hand, conventional electrical measurements operating in stationary conditions take several seconds, thus affecting the measurement result and inhibiting from monitoring charge transients at shorter times. In this work, we present a detailed investigation of flat band transients due to charge detrapping in Al2O3 films designed for nonvolatile applications, on a timescale spanning from hundreds of microseconds to ten minutes. For this purpose, a technique based on the pulsed C-V measurement has been used. The flat band voltage instability due to charge detrapping has been studied systematically.