Integration of resistive switching NiO in small via structures from localized oxidation of nickel metallic layer

Conventional memories approaching their scaling limit, reversible resistance switching effects attract considerable attention because of the potential for high density non volatile memory devices. These resistive switching phenomena have been reported in many simple transition metal oxide films such as TiO₂ or NiO deposited by standard sputtering techniques. This paper is investigating the feasibility of emerging resistive-switching stacks enabling integration of the memory element in interconnect structures resulting in very small memory cells. Indeed, we have developed innovative process steps leading to localized formation of bi-stable NiO at the bottom of via structures. Thickness-controlled NiO layers were formed from the partial oxidation of blanket Ni metallic layer through via holes opened in SiO₂. Reversible and repetitive switching was demonstrated on arrays of vias with diameter down to 150 nm. Besides, encouraging reliability performances in terms of endurance and retention were obtained.