Threshold voltage instability in high-k based flash memories

In this work we use an innovative transient technique based on the pulsed C–V measurement and present detailed investigation and simulation of threshold voltage instability in Al2O3 flash memories, on a timescale spanning from hundreds of microseconds to ten minutes. Advantages of the pulsed over the steady-state C–V technique lye in that it can monitor capacitance transients at extremely short times, and it does not affect the flat-band condition itself, since the measurement time is short enough that trapping during the measurement does not occur. The flat-band voltage instability has been studied systematically as a function of the film thickness, the detrapping time and the discharge accelerating voltage. A detailed description of the detrapping dynamics is given.