Discharge parameters and plasma characterization in a dc magnetron with liquid Cu target

The magnetron discharge with uncooled Cu target has been investigated in a wide range of parameters (magnetic field, power, Ar pressure). The evolution of discharge voltage and current has been measured yielding the transition time to stable gasless self-sputtering regime of 175 s at 2.5 kW total power. I-V curves for the solid- and liquid-target magnetron discharge have been obtained, and the magnetic field magnitude has been optimized to ensure both highest attainable power density (600 W/cm2) and high discharge voltage (∼ 800 V) for the best sputtering efficiency. The spatial distributions of electron temperature and plasma density were systematically measured at different power values spanning from cold solid target to completely molten one. It has been shown that in the transition region plasma density grows unevenly with discharge power. Eventually, maximum densities of around 3 × 1011 cm−3 were recorded 5 cm away from the target. In the gasless self-sputtering mode, the deposition rate at 26 cm above the target increased 40-fold as compared to solid target performance under the same power conditions.