Data Retention Enhancement of Modern 55nm NOR Flash Memory

Charge loss of NOR flash cell originates from H species diffused to interface of tunnel oxide and silicon substrate from CESL (contact etch stop layer) was reported. On the contrary to data loss from intrinsic defects of growth tunnel oxide, the observed data loss is directly related to CESL layer thickness. Hydrogen species released from PECVD (plasma enhanced chemical vapor deposition) of silicon oxy-nitride and silicon nitride diffuse into Si/SiO
2
interface, which may significantly affect interface states and bulk traps of tunnel oxide, which are responsible for NOR flash memory data loss. Stress exhibit negligible influence on data retention for presented study. By choosing proper CESL layer thickness, greatly enhanced data retention performance is achieved.