Tunneling oxide engineering for improving retention in nonvolatile charge-trapping memory with TaN/Al2O3/HfO2/SiO2/Al2O3/SiO2/Si structure

In this paper, we demonstrate retention improvement in nonvolatile charge-trapping memory cells by tunneling oxide engineering with Al2O3. By utilizing SiO2/Al2O3/SiO2 layers for the tunneling oxide, it is shown that the threshold voltage window after 10 years is significantly improved from 0.78 V to 4.18 V through Synopsys Sentaurus technology computer-aided design simulation. In addition, retention improvement from incorporating SiO2/Al2O3/SiO2 tunneling layers is compared with that using SiO2/Si3N4/SiO2 tunneling layers. The relationship between charge-trapping layer thickness and trapped charge emission is also investigated. As a result, we open up the possibility of using HfO2 as a charge-trapping layer with significant reliability enhancement.