Reliability and device scaling challenges of trapping charge flash memories

As flash memories move toward the giga-bits era, several challenges limit their scalability. Floating gate flash memories face the problems of un-scalable tunnel oxide, and the last technology node of NOR flash was predicted to be 65 nm, based on the extrapolation of the difference between physical and electrical cell dimensions vs. generations, which drops to zero at 45 nm. Although SONOS-type flash memories show better scalability and simpler process, there are still some difficulties. In this paper, three SONOS-type flash memories (SONOS, NROM and PHINES) are compared and the scaling problems and reliability issues are disclosed.