Investigation of Methods That Greatly Improve 3D NOR Flash to Either Gain Superb Retention or Become DRAM-like with High Endurance $(> 1\mathrm{G}$ cycling) and High Write-bandwidth $(> 4\text{Gb}/\mathrm{s})$

Recently we proposed a micro wall heater in the 3D AND-type NOR Flash for thermally assisted Flash operations [1]. In this work, we further propose three efficient methods to improve this novel device: (1) A 3DIC chip-to-chip Cu hybrid bonding technique is proposed to provide an external heater controller chip to support the high drive current ( $> 50\text{mA}$ ) with address selection capability for many small units of heater, without disturbing the conventional peripheral circuit for normal Flash operations. (2) For a sample S1 with regular thick bandgap engineered tunnel oxide (BE-Tox), an electrical “refill” method that iteratively repeats the programming and de-trapping (by heater pulse) will retain only “deeper $(> 1.1\text{eV})$ ” electron traps and provide superb post-1M cycled retention that keeps $\sim 5\mathrm{V}$ Vt memory window after 150C 168hr baking. (3) In a second sample S2 with special tuned thin BE-Tox, we achieve fast write speed $(\sim 500\text{ns}$ at FN programming and erasing) with $\sim 3\mathrm{V}$ Vt memory window after 1G endurance and $>1000\sec$ retention time. Supported by the low-power and fast FN programming, it is projected that this device can provide high write bandwidth of $\sim 4\text{Gb}/\mathrm{s}$ by 2Kb page programming at only $\sim 200\mathrm{m}$ 1W chip power. This work paves two potential paths to support either robust retention non-volatile memory at high-temperature storage, or DRAM-like dynamic Flash memory devices with high-endurance and high write bandwidth.