Charge loss in TANOS devices caused by Vt sensing measurements during retention

Abstract

In TANOS stuctures in retention, the major decrease in the programmed threshold voltage is found to be caused by the Vt sensing (IdVg measurements) rather than by intrinsic charge loss (when no bias is applied). This Vt decrease can be understood within the process of the temperature-activated charge transport through the Al2O3 blocking oxide. The charge loss can be minimized when Vt sensing time is decreased down to micro seconds. Blocking oxides engineered by adding a thin SiO2 layer at the SiN/AlO interface demonstrate significant suppression of the charge loss.