OPTIMIZATION OF PROGRAM THRESHOLD WINDOW FROM UNDERSTANDING OF NOVEL FAST CHARGE LOSS IN NONVOLATILE MEMORY

This paper describes and discusses intensively the charge loss charact eristics in the stacked-gate memory device with interpoly oxide-nitrid e-oxide (ONO) dielectric at elevated temperatures, There exist two dis tinct phases in the charge loss characteristics. The dominant mechanis m in the first phase can be described as the charge transport in the n itride layer. The second phase is dominated by effective thermionic em ission effect from the stacked gate system. A linearly proportional re lationship is also observed between normalized charge loss in the firs t phase and initial threshold voltage shift. Due to the fast charge lo ss rate, the charge loss in the first phase governs the threshold inst ability of the stacked-gate device. A method to determine the programm ing window for better threshold voltage stability based on charge loss in first phase is proposed.