Characteristics of continuous high power magnetron sputtering (C-HPMS) in reactive O₂/Ar atmospheres

Target poisoning is prevalent in reactive magnetron sputtering and causes deleterious effects, especially in deposition using metal targets. Both the deposition rate and the stoichiometry ratio of the coatings will be compromised because of the quicker coverage of the poisoning materials on the target relative to removal by sputtering. Continuous high-power magnetron sputtering (C-HPMS) possesses merits such as more rapid sputtering than high-power impulse magnetron sputtering and better target poisoning resistance. In this work, the discharge and plasma characteristics of C-HPMS for an Al metal target in reactive O₂/Ar atmospheres are investigated by modeling and alumina deposition. At a constant oxygen partial pressure, larger discharge power increases target etching significantly compared to surface combination with O₂, leading to reduced surface poisoning. Besides, a higher temperature is produced near the target to produce more intense rarefaction effects and decrease the risk of target poisoning. In Al discharge, the stable deposition window in the O₂/Ar ratio under 120 W/cm² is 5 times of that under 20 W/cm². Moreover, a large deposition rate of 112 nm/min is achieved at the poisoning-saturated point and a target/substrate distance can be increased to larger than 40 cm, thus providing more flexibility in the design of deposition parameters and hardware requirement. Our results show that high discharge intensity improves plasma density and ionization rates of reactive particles boding well for the deposition of under-stoichiometric and higher-quality amorphous Al₂O₃ films. The reactive C-HPMS technique has large potential in the commercial production of functional coatings and thin films.