Low operation voltage and high thermal stability of a WSi2 nanocrystal memory device using an Al2O3/HfO2/Al2O3 tunnel layer

Abstract

A WSi2 nanocrystal nonvolatile memory device was fabricated with an Al2O3/HfO2/Al2O3 (AHA) tunnel layer and its electrical characteristics were evaluated at 25, 50, 70, 100, and 125 degrees C. The program/erase (P/E) speed at 125 degrees C was approximately 500 mu s under threshold voltage shifts of 1V during voltage sweeping of 8V/-8V. When the applied pulse voltage was +/- 9V for 1 s for the P/E conditions, the memory window at 125 degrees C was approximately 1.25V after 10(5) s. The activation energies for the charge losses of 5%, 10%, 15%, 20%, 25%, 30%, and 35% were approximately 0.05, 0.11, 0.17, 0.21, 0.23, 0.23, and 0.23 eV, respectively. The charge loss mechanisms were direct tunneling and Pool-Frenkel emission between the WSi2 nanocrystals and the AHA barrier engineered tunneling layer. The WSi2 nanocrystal memory device with multi-stacked high-K tunnel layers showed strong potential for applications in nonvolatile memory devices. (C) 2012 American Institute of Physics.