Process effect analysis on nitride trap distribution in silicon-oxide-nitride-oxide-silicon flash memory based on charge retention model

Abstract

This paper analyzes data retention characteristics to determine process effects on the trap energy distribution of silicon nitride in silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices. Nitride films were prepared by low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD). PEVCD films embedded with silicon nanocrystals (Si-NCs) were also compared. The flat band voltage shift in the programmed device was measured at high temperatures to observe the thermal excitation of electrons from the nitride traps in retention mode. The trap energy distribution was extracted using the charge decay rates, and the experimental results showed that nitride fabricated by PECVD has a shallower trap than nitride fabricated by LPCVD. In nitride with Si-NCs, increased trap sites were observed in the range of 1.14 eV to 1.24 eV.