Improved charge injection in Si nanocrystal non-volatile memories

We report in this work a metal-oxide-semiconductor Si-nanocrystal memory basic cell which shows, at the same time, fast writing, long charge retention and high resistance to Write/Erase cycling (endurance). This has been achieved by optimizing a structure reported previously that exhibited excellent retention characteristics. For the new structure, 15 keV Si ions have been implanted in a 40 nm thick oxide at high doses in order to obtain Si excess ranging from 10 to 20 at.% at projected range. We show that increasing the implanted dose worsens the retention time but there is a compromise in which writing times are improved several orders of magnitude while maintaining retention times still long enough.