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

Abstract

In this work, we present an experimental and theoretical study of nitride trap devices with a HTO/Al2O3 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.

Fundamental reliability issues of advanced charge-trapping Flash memory devices

“…Trap assisted current through Ab03 blocking oxide is reported to be the primary cause of charge loss in retention especially at low temperature [25,32], when trap-to-band (TBT) and TAT contributions current dominate [33]. For this reasons, CT-NVM solutions with a BGE blocking dielectric stacks have been proposed to improve retention [34][35]. In addition, undesired charge trapping into the alumina defects can take place during PIE operations [36].…”

“…In order to limit the Ab03 reliability issues, blocking oxide engineering stacks have been proposed. The most popular solution is the insertion of a thin Si02 layer between alumina and silicon nitride layers [34,35], which is found to improve retention and read disturbs [5).…”

The effects of RF power on the interfacial property between Al2O3 and Si3N4 and on the memory property in a MANOS structure

“…The use of an Al 2 O 3 blocking oxide increases the electric field across the tunnel oxide and charge-storage layer and decreases the electric field across the blocking oxide layer. The high quality of the blocking oxide serves the improvement of program/erase speed and to increase the charge retention time in MANOS-type flash memory [3][4][5][6][7].…”