Large area deposition of transparent and conductive ZnO:Al layers by reactive mid frequency magnetron sputtering
This study is on the up scaling of the reactive mid frequency (MF) magnetron sputter deposition of zinc oxide:aluminum (ZnO:Al) layers developed by our institute. Aluminumdoped zinc oxide films have been prepared by reactive dual cathode magnetron sputtering from metallic Zn:Al targets on glass substrates with dimension of 1,000 x 600 millimeters squared (mm²) in a vertical in-line coater for application as transparent electrodes for a-Si:H thin film solar cells. At approximately 150 °C substrate temperature, resistivity of 3.4 x 10-4 ohm-centimeters (cm) has been reached for sputter deposition in transition mode at dynamic deposition rate of 80 nm m/min. The optical, electrical, and structural properties of these films have been investigated by means of optical spectroscopy (ultraviolet-infrared [UV-IR]), variable angle spectroscopic ellipsometry, X-ray diffraction, atomic force microscopy, Hall mobility, and conductivity measurements. Electron probe micro analysis and secondary ion mass spectroscopy has been used for chemical characterization. Detailed results on film and process properties will be shown.