Atomistic Study of Lateral Charge Diffusion Degradation During Program/Erase Cycling in 3-D NAND Flash Memory

Abstract

Impacts of lateral charge diffusion on the retention characteristics of charge-trapping (CT) 3-D NAND flash memory are comprehensively studied in this paper. Atomistic study through ab initio calculation is carried out to understand the correlations between P/E stress induced shallow trap generations and pre-existing traps in Si3N4. It is shown that more shallow traps will be generated with a combination of electron/hole injections and free hydrogen (H) during P/E cycling. Our results strongly suggest that process optimizations to control free H in Si3N4 CT layer could be a key point for robust retention characteristics.

Keywords

• Silicon nitride
• 3D NAND
• charge trapping
• lateral charge diffusion
• shallow trap