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

Abstract

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 100mm diameter in argon–oxygen gas mixtures at the total pressure close to 2Pa. The repetition frequency was 500Hz at the average target power density from 5Wcm−2 to 103Wcm−2 during a deposition. The duty cycles ranged from 2.5% to 10%. The target-to-substrate distance was 100mm. For the same duty cycle of 10%, the deposition rates were up to 140nm/min for the ZrO2 films and up to 345nm/min for the Ta2O5 films. The ZrO2 films were crystalline with a dominant monoclinic phase. They exhibited a hardness of 16GPa, a refractive index of 2.19–2.22 and an extinction coefficient of 2×10−3–6×10−3 (both at the wavelength of 550nm). The Ta2O5 films were nanocrystalline. They exhibited a hardness of 7GPa, a refractive index of 2.09–2.15 and an extinction coefficient of less than 1×10−4.