Process control and thin film properties of Al2O3 layers deposited by high power impulse magnetron sputtering

A new process control for the reactive high power impulsemagnetron sputtering (HiPIMS) has been developed. It is based on a superposition of bipolar mid-frequency (MF) with low-frequency high power pulses in combination with reactive gas partial pressure control. Alumina (Al2O3) thin films have been deposited on quartz substrates from metallic aluminum targets in an Ar/O2 gas mixture. The films show a smoother surface and a higher refractive index with increasing peak power density.