The promising multi-bit/level programming operations for nano-scaled SONOS memory

摘要

In order to obtain a reliable multi-bit/level operation for nano-scaled polycrystalline silicon-oxide-nitride-oxide-silicon (SONOS) memory, two different localized charge-injection programming methods, the channel hot electron injection with a positive substrate bias (CHEI-P) and pulse agitated substrate hot electron injection (PASHEI), are operated in 90 nm SONOS cells. It is found that the cells programmed by CHEI-P have the better endurance property than by PASHEI. The better endurance is due to the less accumulation of charges in the nitride layer, evidenced by surface potential profiling technique. CHEI-P program further exhibits the superior endurance and retention properties after 10~4 program/erase cycles in 4-bit/4-level operations. These results illustrate that CHEI-P program is a promising candidate for multi-bit/levels nano-sized SONOS memory.