A logic-compatible embedded flash memory for zero-standby power system-on-chips featuring a multi-story high voltage switch and a selective refresh scheme

Embedded flash memory implemented using standard I/O devices can open doors to new applications and system capabilities, as it can serve as a secure on-chip non-volatile storage for VLSI chips built in standard logic processes. For example, it is indispensable for adaptive self-healing techniques targeted for mitigating process variation and circuit aging related issues where system information must be retained during power down periods. Embedded non-volatile memory can also enable zero-standby power systems by allowing them to completely power down without losing critical data. There has been numerous device and circuit level research on high-density non-volatile memories such as flash, STT-MRAM, PRAM, and RRAM. However, only few attempts have been made to develop a cost effective moderate-density non-volatile solution using standard I/O devices. In this paper, a logic-compatible embedded flash memory that uses no special devices other than standard core and I/O transistors is demonstrated in a generic logic process having a 5 nm tunnel oxide. An overstress-free high voltage switch and a selective WL refresh scheme are employed for improved cell threshold voltage window and higher endurance cycles.