Investigation of endurance degradation in a CTF NOR array using charge pumping methods

Abstract

We investigate the effect of interface states on the endurance of a charge trap flash (CTF) NOR array using charge pumping methods. The endurance test was completed from one cell selected randomly from 128 bit cells, where the memory window value after 102 program/erase (P/E) cycles decreased slightly from 2.2 V to 1.7 V. However, the memory window closure abruptly accelerated after 103 P/E cycles or more (i.e. 0.97 V or 0.7 V) due to a degraded programming speed. On the other hand, the interface trap density (Nit) gradually increased from 3.13×1011 cm-2 for the initial state to 4×1012 cm-2 for 102 P/E cycles. Over 103 P/E cycles, the Nit increased dramatically from 5.51×1012 cm-2 for 103 P/E cycles to 5.79×1012 cm-2 for 104 P/E cycles due to tunnel oxide damages. These results show good correlation between the interface traps and endurance degradation of CTF devices in actual flash cell arrays. ? 2016 KIEEME. All rights reserved.