We have compared the quality of Nb and NbN films obtained by de magnetron s
puttering from a new and a fully eroded Nh target. Since current supercondu
cting electronic devices such as SIS mixers, RSFQ digital circuits and hot
electron bolometers are produced by reactive sputtering, we are interested
in optimum source operating conditions over the target life time. We find t
hat stress-free Nb films can, at any state of the target, be obtained under
the same Ar pressure and de power applied to the sputtering source. We sho
w that this approach also works for NbN reactive sputtering if the nitrogen
flow rate is maintained proportional to the deposition rate of Nh In both
cases the zero-stress point shifts to lower cathode de voltage as the targe
t erodes. Additionally we find that the effectiveness of the magnetic trap
of the magnetron influences the normal state resistivity of the NbN films.