Anomalous plasma evolution in the erosion process in high-power reactive magnetron sputtering

During magnetron sputtering erosion, the change in the morphology and magnetic field of the target surface affects the plasma discharge. Especially in high power and reactive conditions, the plasma evolution during erosion determines the continuity and stability of the discharge. In this work, a global model with iterative modification of the erosion profile is established, by which the reactive sputtering of an Al target in Ar/N2 is simulated to study the plasma evolution and surface combination in the erosion process at different power densities. With increasing discharge power density, the electron density and electron temperature increase significantly to enhance plasma ionization. Consequently, the proportion of adsorbed N2 participating in surface combination decreases from 70% to 31%, while the proportions of N deposition and N-containing ion sub-plantation increase to 44% and 25%, respectively. In the erosion process, the proportion of N participating in surface combination remains essentially unchanged at low power densities. In contrast, at a large power density, N2 adsorption weakens, and the proportion of N-containing ion sub-plantation increases further from 25% to 37%, becoming the main reason for target poisoning. Calculation of the generation and consumption of target surface compounds reveals that the coverage rate of target surface compounds decreases and then increases in the sputtering process at a low power density, while that rises all the time at a large power density, leading to a severe target poisoning.