Threshold voltage instability in high-k based flash memories

摘要

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 Al_2O_3 flash memories, on a time-scale 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.