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.

► An Au/HfAlO/AlN/(HfON/SiO2)/Si high-k gate stack structure is proposed.
► A band-engineered dual tunneling layer (HfON/SiO2) is proposed and prepared.
► A good trade-off among the memory characteristics is obtained.
► In-situ sputtering method is employed to fabricate the gate stack structure.