Universal guiding principle for the fabrication of highly scalable MONOS-type memory -atomistic recipes based on designing interface oxygen chemical potential-

For the fabrication of highly scalable metal-oxide-nitride-oxide-semiconductor (MONOS) type memories, we propose a universal guiding principle, where the interfacial O chemical potential is designed to prevent the formation of defects that undergo irreversible structural changes. Our first principles calculations indicate that O-related defects in SiN charge trap layers in a MONOS-type memory intrinsically cause the local collapse of the SiN layer and memory degradation. These features originate from the existence of a large number of metastable structures, which can readily appear with program/erase cycles or thermal activation. To overcome this issue, we propose a skilful and realistic recipe to prevent O incorporation into SiN layers: an insert of a thin Si layer into the SiO₂ layer near SiO₂/SiN interface. This fabrication process leads to drastic lowering of O chemical potential in the interface. Moreover, the present proposal is a general and universal guiding principle to synthesize the sharp and high quality oxide interfaces which are necessary to form aggressively downsized devices.