Improvement of thickness distribution and crystallinity of ZnO thin films prepared by radio frequency planer magnetron sputtering

Abstract

An improvement of thickness distribution and crystallinity in ZnO thin films prepared by radio frequency (rf) planer magnetron sputtering have been studied. Optimum thickness distribution of less than ±2.2% in a 3-inch wafer is obtained by changing the substrate angle to the ZnO target and is in accordance with cosine law. C-axis orientation perpendicular to the silicon substrate is confirmed by X-ray diffraction. The stress of ZnO thin films is more than 0.3 GPa and its distribution is independent of the substrate angle that is set at a slant to the optimum angle for thickness distribution. These results indicate that thickness distribution of ZnO thin films heavily depends on the substrate angle, while the c-axis orientation, the stress and its distribution are independent of the setting angle of the substrate. The stress distribution is attributed to the lattice constant distribution and the crystallinity distribution of ZnO thin films.