Two Metal Level Semi-Damascene Interconnects for Superconducting Digital Logic

In this paper we present a superconducting two-metal level (2ML) BEOL unit process based on NbxTi(1-x)N (NbTiN) that was developed in imec’s 300 mm pilot line using a semi-damascene flow and 193i lithography. The unit process features direct-metal-etch wires with minimum critical dimension (CD) of 50 nm and shallow planarized vias with minimum CD of 80 nm deposited at 420 ˚C, compatible with CMOS BEOL dielectrics. Normalized line resistance of 50 nm NbTiN wires show that 95% of the devices meet the expected resistance 800–1200 Ω/μm consistent with blanket films resistivity. Low temperature measurements show that NbTiN wires and vias have a critical temperature of 12-13.5 K and a critical current density of 80–113 mA/μm².