Superconducting Nb interconnects for Cryo-CMOS and superconducting digital logic applications

Abstract

A 100 nm wide superconducting niobium (Nb) interconnects were fabricated by a 300-mm wafer process for Cryo-CMOS and superconducting digital logic applications. A low pressure and long throw sputtering was adopted for the Nb deposition, resulting in good superconductivity of the 50-nm-thick Nb film with a critical temperature (Tc) of 8.3 K. The interconnects had a titanium nitride (TiN)/Nb stack structure, and a double layer hard mask was used for dry etching process. The exposed area of Nb film was minimized to decrease the effects of plasma damage during fabrication and atmosphere. The developed 100-nm-wide and 50-nm-thick Nb interconnect showed good superconductivity with a Tc of 7.8 K and a critical current of 3.2 mA at 4.2 K. These results are promising for Cryo-CMOS and superconducting digital logic applications in 4 K stage.