Redox Molecules for a Resonant Tunneling Barrier in Nonvolatile Memory

To attain better program/erase (P/E) efficiency while maintaining retention, durable redox molecules were integrated into the flash memory gate stack to form resonant tunneling barrier by either a hybrid organic/inorganic deposition or a simple solution-based layer-by-layer (LBL) method. Compared with fullerene molecules, the proposed porphyrin has high number density and a wafer-ready LBL process. Improvement in electron retention of approximately six orders of magnitude to programming time (tR/t_PE) was observed for Au nanocrystal memory with a hybrid organic-inorganic tunnel barrier. With the LBL method, the tR/t_PE improved by at least two orders of magnitude for both electron and hole carriers, with the P/E cycling endurance larger than 10⁴ cycles. Furthermore, the gate current is used to characterize the transport mechanism and study the electrical reliability of the organic layers. A better understanding of the charge storage and insulation properties of these organic barriers can improve future design integration on all-organic or hybrid molecular electronics.