Tunneling barrier engineered charge trap flash memory with ONO and NON tunneling dielectric layers

Tunneling barrier engineered charge trap flash (TBE-CTF) memory devices were fabricated using the tunneling barrier engineering technique. Variable oxide thickness (VARIOT) barrier and CRESTED barrier consisting of thin SiO₂ and Si₃N₄ dielectric layers were used as engineered tunneling barrier. A faster program/erase speed as well as a larger memory window was achieved from the TBE-CTF memory. The VARIOT-type tunneling barrier composed of oxide-nitride-oxide (ONO) layers revealed a longer retention time and superior endurance characteristic. On the other hand, the CRESTED tunneling barrier composed of nitride-oxide-nitride (NON) layers showed degraded retention and endurance characteristics. It is found that the degradation of NON barrier is associated with the increase of interface state density at the tunneling barrier/silicon channel by programming and erasing (P/E) stress.