Data retention characteristics of MANOS-type flash memory device with different metal gates at various levels of charge injection

We investigated the impact of charge injection and metal gates (Al and Pt) on the data retention characteristics of metal-alumina-nitride-oxide-silicon (MANOS) devices for NAND flash memory application. Through the theoretical and experimental results, the highly injected charge (ΔV_TH) could cause the band bending of Al₂O₃, which reduced the tunneling distance across Al₂O₃. Thus, the dominant charge loss path is not only toward SiO₂ but also toward Al₂O₃ direction. Compared to low-metal work function (F{cyrillic}_M), ONA stack with high-F{cyrillic}_M showed better data retention characteristics, even if ΔV_TH is high. This could be explained by Fermi level alignment for different F{cyrillic}_M, which results in the reduction of electric field across the Al₂O₃ compensated by the ΔF{cyrillic}_M (F{cyrillic}_Pt - F{cyrillic}_Al).