Feed-back Pulsed Reactive Gas Flow Control: A Simple and Cheap Method for High-rate Reactive AC Magnetron Sputtering of High-quality ZrO2 Films

Densified and highly optically transparent zirconium dioxide films (extinction coefficient of 2 x 10-4 at 550 nm) were prepared by reactive ac magnetron sputtering on a floating substrate in argon-oxygen gas mixtures. We used two unbalanced magnetrons in a closed-field configuration equipped with zirconium targets (100 mm in diameter) driven by a mid-frequency ac power supply producing sinusoidal waveforms of the target voltage and current. The depositions of the films were performed at the repetition frequency of about 85 kHz, the total pressure close to 1 Pa and the average target power densities of 5 – 15 Wcm-2 which are used in industrial ac magnetron sputtering systems. We found that a simple feed-back pulsed reactive gas flow control [1] is very effective also in industrially-demanded reactive ac magnetron sputtering. The method led to a stable, arc-free sputtering process with enhanced deposition rates (up to 84 nm/min), being up to 2.5 times higher compared with the depositions in an oxide mode at the same target power density. We will report on deposition characteristics, mechanical and optical properties of the films and their surface morphology.