  Uniformity in thickness and electronic properties of superconducting niobium
titanium nitride (NbTiN) thin films is a critical issue for upscaling
superconducting electronics, such as microwave kinetic inductance detectors for
submillimeter wave astronomy. In this article we make an experimental
comparison between the uniformity of NbTiN thin films produced by two DC
magnetron sputtering systems with vastly different target sizes: the Nordiko
2000 equipped with a circular 100mm diameter target, and the Evatec LLS801 with
a rectangular target of 127 mm x 444.5 mm. In addition to the films deposited
staticly in both systems, we have also deposited films in the LLS801 while
shuttling the substrate in front of the target, with the aim of further
enhancing the uniformity. Among these three setups, the LLS801 system with
substrate shuttling has yielded the highest uniformity in film thickness
(+/-2%), effective resistivity (decreasing by 5% from center to edge), and
superconducting critical temperature (T_c = 15.0 K - 15.3 K) over a 100 mm
diameter wafer. However, the shuttling appears to increase the resistivity by
almost a factor of 2 compared to static deposition. Surface SEM inspections
suggest that the shuttling could have induced a different mode of
microstructural film growth.
