Growth characteristics and residual stress of RF magnetron sputtered ZnO:Al films

Transparent and conductive ZnO:Al films were deposited by RF reactive magnetron sputtering on glass substrates. The growth characteristics of the films as function of oxygen fraction and RF power were investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy; while the induced residual stress in the films was calculated by the Stoneyʹs equation. It is shown that the deposits were flat and dense with a columnar structure in the cross-section morphology. A ZnO (0002) preferred orientation was obtained when the oxygen fraction used in the deposition process was larger than 12%. The growth rate reveals a maximum value depending on the oxygen fraction and RF power. All the deposits show a compressive stress which increased as the RF power was increased when the oxygen fraction in the deposition process was 8∼10%, while it decreased as the oxygen fraction was 12∼15%.