Characterization of scaled SONOS EEPROM memory devices for space and military systems

We present recent results on an integrated radiation-hardened technology, which consists of scaled silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile semiconductor memory (NVSM) and bulk CMOS devices - devices designed specifically for high-density, 1 Mb EEPROMs operating in space and military environments. These devices operate at low-voltage (+7V, 2.5 ms write, -7V, 7.5 ms erase) with 10-year retention at 150C and greater than 10⁵ erase/write cycles. We describe erase/write, retention and endurance results over a 22-250C temperature range with a tunnel oxide of 1.8 nm, ´oxynitride´ of 6.5 nm, and a blocking or ´cap´ oxide of 3.0 nm. These scaled SONOS devices exhibit an extrapolated 10-year memory window of 1.2V (22C) and acceptable 0.3V (150C). A SONOS retention model is presented, which includes charge loss from both direct tunneling and thermal excitation. We discuss recent results of a radiation-hardened 1Mb SONOS EEPROM and its memory cell. In addition, we discuss experiments on ´localized´ charge storage with hot electron injection to write SONOS/NROM™ memory devices for higher functional density with increased retention.