Sputtering of ZnO:Al films from dual tube targets with tilted magnetrons

Aluminum doped zinc oxide (ZnO:Al) films were deposited by mid-frequency sputtering rotating tube targets at high discharge powers in a double cathode system. The magnetrons located inside the tube targets were tilted by ± 30°, leading to different racetrack orientations. Deposition rate and electrical properties of statically deposited films were investigated. Different properties of ZnO:Al films show lateral variations corresponding to the racetrack positions, which shift according to the tilt angles of double magnetrons. The highest average static deposition rate and the corresponding dynamic value were up to 360 nm/min and 111 nm m/min, respectively, for magnetrons tilted towards the center of the cathodes. The material properties of the ZnO:Al film prepared in dynamic mode were found to behave like the superpositions of properties of static films at different positions. Upon wet chemical etching in diluted hydrochloric acid (HCl), the surfaces of sputtered ZnO:Al films became rough, and three typical surface structures were observed and identified on statically deposited ZnO:Al films. The related plasma physics, growth and chemical etching mechanisms were discussed.