Dual-Mechanism Memory Combining Charge Trapping and Polarization Switching for Wide Memory Window Flash Cell

Abstract

We propose a novel memory device to overcome the limited Vth window in charge trap flash (CTF) memory, which prevents the realization of a high number of bits/cell. The proposed memory device (named "dual mechanism memory") has a ferroelectric HfZrO(2 )layer on the channel so that the conductance of the channel can be controlled by the remanent polarization (P-r). In addition, since trap-rich Si3N4 and tunnel SiO2 layers are located on top of the ferroelectric layer, the conductance of the channel can also be controlled by electron injection/removal from/to the gate electrode. Compared to a reference memory that uses only charge trapping, the dual-mechanism memory provided up to 96% wider memory window and exceeded the theoretical limit of ISPP slope in a conventional CTF. It also showed up to 36% improvement in retention characteristics. The enhanced retention performance is attributed to compensation of the E-field stress by Pr.