A Comparative Study of Single-Poly Embedded Flash Memory Disturbance, Program/Erase Speed, Endurance, and Retention Characteristic

Single-poly embedded flash (eFlash) memory is a unique category of embedded nonvolatile memory (eNVM) that can be built in a generic logic technology. Several single-poly eFlash cells have been proposed for cost-effective moderate density eNVM applications. However, the optimal cell configuration of single-poly eFlash is still under debate. In this paper, we compared various single-poly eFlash memory structures in terms of disturbance, program/erase speed, endurance, and retention characteristic based on simulated and experimental data from two eFlash test chips fabricated in a generic 65-nm logic process using standard 2.5 V I/O transistors with 5-nm tunnel oxide. We conclude that a 5T eFlash cell structure combining a pMOS coupling device, an NCAP tunneling device, and an nMOS read/program device with two additional pass transistors to support self-boosting is the most attractive option for logic-compatible eNVMs.