Experimental techniques on the understanding of the charge loss in a SONOS nitride-storage nonvolatile memory

The endurance and charge loss are the most critical issue in the design of a SONOS memory cell. The origin of the window closure and charge loss was partly caused by the electrons and holes mismatch along the channel lateral direction during the cycling. In this paper, two measurement techniques to observe the mismatch of programmed electrons and erased holes have been developed. It was demonstrated on an MTP (Multi-Time-Programming) SONOS flash memory. By observing the charge distribution, the mismatch which led to window closure and charge loss can be well understood, and better operating schemes can then be developed.