Trapped Electron and Hole Distribution Mismatch Induced Reliability Degradation of SONOS Type Memory Devices

The reliability of silicon-oxide-nitride-oxide-silicon (SONOS) type memories was analyzed using the charge pumping method and Ⅰ-Ⅴ tests at different temperatures to study its endurance and retention characteristics. A simple model was used to explain the charge loss phenomenon, with a dual-erasure method developed to improve the endurance and retention characteristics. The results indicate that the coexistence of injected holes and electrons after long term cycling, referred to as the mismatch problem, leads to degradation of the device characteristics. With the dual-erasure method, the threshold voltage, V_T, window is maintained after 1×10⁴ programming and erasing cycles and the charge loss is reduced by 410 mV after 72 h baking at 120℃.