Process stabilization and a significant enhancement of the deposition rate in reactive high-power impulse magnetron sputtering of ZrO2 and Ta2O5 films

High-power impulse magnetron sputtering with a pulsed reactive gas (oxygen) flow control was used for high-rate reactive depositions of densified stoichiometric ZrO2 and Ta2O5 films onto floating substrates. The depositions were performed using a strongly unbalanced magnetron with a planar zirconium or tantalum target of 100 mm diameter in argon-oxygen gas mixtures at the total pressure close to 2 Pa. The repetition frequency was 500 Hz at the average target power density from 5 W cm− 2 to 103 W cm− 2 during a deposition. The duty cycles ranged from 2.5% to 10%. The target-to-substrate distance was 100 mm. For the same duty cycle of 10%, the deposition rates were up to 140 nm/min for the ZrO2 films and up to 345 nm/min for the Ta2O5 films. The ZrO2 films were crystalline with a dominant monoclinic phase. They exhibited a hardness of 16 GPa, a refractive index of 2.19-2.22 and an extinction coefficient of 2 × 10− 3-6 × 10− 3 (both at the wavelength of 550 nm). The Ta2O5 films were nanocrystalline. They exhibited a hardness of 7 GPa, a refractive index of 2.09-2.15 and an extinction coefficient of less than 1 × 10− 4.