Growth conditions for sputter deposited niobium oxides

A Nb target was sputtered in radio‐frequency‐excited, Kr/O₂ discharges and films were deposited on unheated fused silica and 〈111〉‐cut Si substrates. Two independent process parameters, cathode voltage and gas O₂ content, were varied. Optical emission spectrometry was used for in situ discharge diagnostics. From this data, we determined: (1) the values of the process parameters at which a complete target surface oxide layer was formed, and (2) the fractional flux of gaseous atomic Nb and molecular Nb‐oxide incident on the substrate over the entire range of process parameters. Post‐deposition film characterization for metallurgical phase identification included x‐ray diffraction, infrared absorption, and electrical resistivity measurements. A ‘‘phase map’’ was constructed, interrelating the independent process parameters, the growth environment, and the metallurgical phases in the films. Comparison with phase maps previously developed for the Nb–O system grown in Ar/O₂ and Ne/O₂ discharges allowed generalizations to be made regarding the growth environment (in terms of Nb, Nb oxide, and oxygen flux to the substrate) under which different Nb‐oxide phases were formed in the film.