Ultrathin HfON/SiO2 dual tunneling layer for improving the electrical properties of metal-oxide-nitride-oxide-silicon memory

A high-k gate stack structure with ultrathin HfON/SiO2 as dual tunneling layer (DTL), AlN as charge storage layer (CSL) and HfAlO as blocking layer (BL) is proposed to make a charge-trapping-type metal-oxide-nitride-oxide-silicon non-volatile memory device by employing in-situ sputtering method. The validity of the structure is examined and confirmed by transmission electron microscopy. The memory window, program/erase, endurance and retention properties are investigated and compared with similar gate stack structure with Si3N4/SiO2 as DTL, HfO2 as CSL and Al2O3 as BL. Results show that a large memory window of 3.55 V at a program/erase (P/E) voltage of +8 V/-15 V, high P/E speed, and good endurance and retention characteristic can be achieved using the Au/HfAlO/AlN/(HfON/SiO2)/Si gate stack structure. The main mechanisms lie in the enhanced electron injection through the ultrathin high-k HfON/SiO2 DTL with suitable band offset, high trapping efficiency of the high-k AlN material, and effective blocking role of the high-k HfAlO BL. (C) 2012 Published by Elsevier B. V.