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

Abstract

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 (Δ V TH) could cause the band bending of Al 2O 3, which reduced the tunneling distance across Al 2O 3. Thus, the dominant charge loss path is not only toward SiO 2 but also toward Al 2O 3 direction. Compared to low-metal work function ( Ф M), ONA stack with high- Ф M showed better data retention characteristics, even if Δ V TH is high. This could be explained by Fermi level alignment for different Ф M, which results in the reduction of electric field across the Al 2O 3 compensated by the Δ Ф M ( Ф Pt − Ф Al).