Improvement of Thermal Stability in Dual Mechanism Memory Using HfxAl1-xO Blocking Layer for 3D V-NAND Flash Application

Dual mechanism memory, which combines charge trapping and polarization switching, was demonstrated as a way to overcome the limited memory window of charge trap flash (CTF) memory. However, due to the poor thermal stability of the Hfy Zr $_{\text {1-y}}$ O (HZO) film, the dual mechanism memory scheme cannot be integrated into the current 3D V-NAND flash device fabrication process where the poly-silicon channel is deposited and annealed after the HZO blocking layer is deposited. In this study, HfxAl $_{\text {1-x}}$ O (HAO) is investigated as the blocking layer due to its superior thermal stability. The dual mechanism memory with HAO blocking layer has achieved a 47% larger memory window compared to the device with HZO blocking layer. It is also demonstrated that the expanded memory window of the dual mechanism memory with HAO enables quad-level cell operation (QLC) with 1 V spacing between each state.