Optimization of process parameters for sputtering of ceramic ZnO:Al2O3 targets for a-Si:H/μc-Si:H solar cells

Aluminum doped ZnO layers with a thickness of 800 nm were deposited dynamically by d.c. magnetron sputtering from a ceramic planar ZnO: Al2O3 target (1 wt.%). A wide range of process parameters, namely oxygen partial pressure, total pressure and power, was covered, while temperature was held constant at 300 °C. Visual absorption in the range of 2.3–4.7% and resistivities between 380 and 2150 µΩcm were obtained. In addition static imprints were performed to reveal the dependence of layer properties on target erosion. It was shown, that films deposited from targets with a race track deeper than 1.8 mm had very stable etching morphologies as well as optical and electrical properties in the range of the observed process parameters. In contrast, a new target yields very different etching structures and an increased resistivity.