High rate reactive magnetron sputtering of ZnO:Al films from rotating metallic targets

Aluminum doped zinc oxide (ZnO:Al) films were reactively sputtered at a high discharge power from dual rotating metallic targets (Zn:Al = 99.5:0.5 wt.%). Deposition conditions like substrate temperature and working points were varied in order to prepare high quality ZnO:Al films. The influences on electrical and optical ZnO:Al thin film properties and surface texture before and after chemical etching in diluted HCl were studied in order to achieve light scattering films as front contact for solar cells. High dynamic deposition rate close to 90 nm m/min and high Hall mobility of up to 47 cm2/Vs were obtained. Transmission of more than 85% in the visible spectral range is obtained for all ZnO:Al films in this study. In addition, the absorption in near infrared region is low due to low doping. Surface texture after etching is usually much rougher than before. However, some films reveal after etching small surface features that are similar to initial surface features. We propose a relationship between initial and post-etched surface textures.