$V_{\rm th}$ Control by Complementary Hot-Carrier Injection for SONOS Multi-Level Cell Flash Memory

In this paper, a complementary hot-carrier injection programming/erasing (P/E) scheme is proposed for accurate threshold voltage (V _th) control for polysilicon-oxide-nitride-oxide-silicon (SONOS) multi-level cell (MLC) flash memory. Alternate hot electrons (HEs) and hot holes (HHs) are injected by pulse gate and drain biases, and complementary HE and HH injections spontaneously correct the V _th offsets via a feedback control enabled by the programming and the offset-correcting cycles. The HE and HH fluxes are balanced at a steady state induced by the tunnel oxide potential transformation. Accurate V _th control is accomplished, and endurance reliability is significantly improved for SONOS MLCs.