On the homogeneity of sputter-deposited ITO films Part I. Stress and microstructure

Tin-doped indium oxide films deposited by d.c. magnetron sputtering were characterized by electrical resistivity, optical transmission, X-ray diffraction (XRD), transmission electron microscopy and stress measurements. Deposition was performed at low temperature and 520 K in different oxygen ambients. The influence of post-deposition annealing was investigated. Special attention was paid to the homogeneity throughout the film thickness with respect to microcrystallinity and stress. It turned out that the low-temperature films consisted of an amorphous phase adjacent to the glass substrate with a severely stressed polycrystalline layer on top. After annealing, the amorphous phase was crystallized and stress free. This anomaly in stress-depth dependence was also reflected in doublet-type peak profiles observed in XRD diagrams. The high-temperature films were homogeneously polycrystalline after deposition and contained high compressive stresses when the oxygen partial pressure during deposition was not too low.