Source optimization for magnetron sputter-deposition of NbTiN tuning elements for SIS THz detectors

NbTiN is one of the most promising materials for use in the tuning circuits of Nb-based SIS mixers for operating frequencies above the gap frequency o f Nh (approximate to 700 GHz). Device development requires stable and repro ducible film properties. In this manuscript we compare the properties of Nb TiN films obtained with a sputtering source using balanced and unbalanced m agnetic trap configurations. This experiment shows that reducing the effect iveness of the magnetic trap by changing the magnet configuration is equiva lent to reducing the sputtering pressure. We also show that it is possible to optimize the configuration of the magnetron magnets to produce stable an d reproducible NbTiN films under the same gas pressure and applied power th roughout the target lifetime.