Correlation between the stress and microstructure in bias-sputtered ZrO2-Y2O3 films

Abstract Thin films of ZrO 2 -8mol.%Y 2 O 3 were produced by r.f. diode sputter deposition using applied substrate bias voltages ranging to -200V. Unlike previous studies that employed scanning electron microscopy, transmission electron microscopy was used here to investigate changes in the grain structure, the defect structure and the columnar morphology of the films due to changes in the bias parameter. Films produced with low bias contained small (20–40 nm) intergranular voids and large intercolumnar cracks and voids. Films produced with high bias were fully dense and their microstructure resembled that of a highly stressed plastically deformed material. Measurements of the film stress showed that the intrinsic component of the film stress became increasingly compressive as the bias increased, in agreement with the microstructural data. In films deposited onto SiO 2 substrates the total stress ranged from + 6 × 10 8 Pa (tensile) in unbiased films to -1.7 × 10 9 Pa (compressive) in films produced with -200 V applied substrate bias.