Process control for low temperature reactive deposition of Al doped ZnO films by ICP-assisted DC magnetron sputtering

Al-doped ZnO (AZO) films were deposited by inductively coupled plasma (ICP) assisted DC magnetron sputtering at low temperatures. The AZO films were produced by sputtering a metallic target (Zn/Al) in a mixture of argon and oxygen gases. AZO films with an electrical resistivity of 6.3 × 10− 4 Ω cm and an optical transmittance of 82% were obtained even at a low deposition temperature (< 150 °C). In situ process control methods were used to obtain stable deposition conditions in the transition region without any hysteresis effect. The target voltage was changed using oxygen flow or DC power as control-parameter. It was found that the ratio of the oxygen to zinc emission intensity, I (O 777 nm) / I (Zn 481 nm) decreased with increasing the target voltage in the transition region.