Fabrication and program/erase characteristics of 30-nm SONOS nonvolatile memory devices

In this paper, we have fabricated nanoscale silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory devices by means of the sidewall patterning technique. The fabricated SONOS devices have a 30-nm-long and 30-nm-wide channel with 2.3/12/4.5-nm-thick oxide/nitride/oxide film on fully depleted-silicon-on-insulator (FD-SOI) substrate. The short channel effect is well suppressed though devices have very short channel length and width. Also, the fabricated SONOS devices guarantee good retention and endurance characteristics. In 30-nm SONOS devices, channel hot electron injection program mechanism is inefficient and 2-b operation based on localized carrier trapping in the nitride film is difficult. The erase speed is improved by means of band-to-band (BTB) assisted hole injection mechanism. In 30-nm SONOS devices, program and erase operation can be performed efficiently with improved erase speed by combination of Fowler-Nordheim (F-N) tunneling program and BTB assisted hole injection erase mechanism because the entire channel region programmed by F-N tunneling can be covered by two-sided hole injection from source and drain.