Engineering of Si-Rich Nitride Charge-Trapping Layer for Highly Reliable Metal–Oxide–Nitride–Oxide–Semiconductor Type NAND Flash Memory with Multi-Level Cell Operation

The relationship between chemical structure (N/Si ratio) or physical structure (bilayer or laminate structure) of Si-rich nitride charge-trapping layer for metal–oxide–nitride–oxide–semiconductor (MONOS) type NAND flash memory and its electrical characteristics (including program/erase Vth window, fresh cell data retention and data retention after program/erase cycling stress) are investigated in detail. A bilayer charge-trapping structure formed by two different composite Si-rich nitride films has been developed that can realize a sufficient program/erase window and excellent data retention characteristics for multi-level cell (MLC) operation.