On the role of a HTO/Al2O3 bi-layer blocking oxide in nitride-trap non-volatile memories

In this work, we present an experimental and theoretical study of nitride trap devices with a HTO/Al
₂
O
₃
bi-layer blocking oxide. Such SAONOS (Silicon/Alumina/HTO/Nitride/Oxide/Silicon) devices are compared with standard SONOS (Silicon/HTO/Nitride/Oxide/Silicon) and SANOS (Silicon/Alumina/Nitride/Oxide/Silicon) memories. The role of the different layers (blocking oxide and control gate) is deeply analyzed, focusing on their impact on memory performance and reliability. Then, a semi-analytical model is developed, which provides a good understanding of the physical mechanisms at the origin of program/erase characteristics.