Reliable and Radiation-Hardened Push-Pull pFlash Cell for Reconfigured FPGAs

Abstract

The base component of radiation-hardened flash-based field-programmable gate arrays (FPGAs) is a reconfigurable memory cell, which is reliable and has high driving current. A novel push-pull pflash cell was proposed in this article, which combined the advantages of indirect coupling and radiation-hardening. The proposed device consisted of two 2T-flash transistors and a pMOS transistor. The push-pull pflash cell was successfully fabricated using 90 nm technology. Through the indirect coupling of the floating gate (FG), the proposed push-pull pflash cell overcame the interference found in sense-switch pflash cells. Compared to conventional sense-switch pflash cells, the proposed push-pull pflash cell had superior driving current, reliability, and radiation-hardening. Band-to-band tunneling-induced hot-electron (BBHE) programming was used to realize ON state, while Fowler-Nordheim (FN) erasing was used to realize OFF state in the proposed device. The electrical properties of both states were characterized. The ON-state driving current and OFF-state leakage current were shown to be consistent. The uniformity of driving current under -1.2 V was below 3%. The proposed device was capable of being programmed/erased cyclically over 10,000 times, and it had a 10-year lifespan with ON/OFF-state stress at 25°C. Additionally, the proposed device was tolerant of total ionizing dose (TID) over 150 Krad(Si). The purposed push-pull pflash cell was suitable for applications in flash-based FPGAs.