Hybrid plasma model for reactive deposition of CrN thin films by deep oscillation magnetron sputtering

Abstract

Plasma characteristics and target poisoning condition during reactive deep oscillation magnetron sputtering with Cr target are investigated using a time-dependent hybrid model. The hybrid model combines a zero-dimensional global model with a two-dimensional fluid model. Target voltage and current waveforms at a charging voltage of 250–400 V and a nitrogen flow fraction of 10%–75% are utilized as the input. The global model deals with the plasma chemical reactions to obtain the particle densities in the ionization region. The calculated densities then serve as boundary conditions for the fluid model, which simulates the transport of the plasma toward the substrate. The peak densities of metallic ions notably increase as the charging voltage rises from 250 to 400 V, whereas the gas ion densities show only a minor increase. At fN2=10%, the dominant species in the plasma are Ar+ and Cr+. As the nitrogen fraction increases, there is a growing trend in the peak densities of Cr2+, N+, and N2+ ions. However, the peak values of gas recycling parameters decline notably over time during the macropulse, whereas the target species recycling is gradually enhanced. The averaged peak values of the generalized self-sputtering parameter increase significantly as the charging voltage rises, driven by enhanced gas recycling. Increasing the nitrogen fraction shifts the discharge from metal mode toward poisoned mode. Target poisoning dynamics reveals that chemisorption and sputtering are the main mechanisms for surface compound formation and removal, respectively. Simulation results provide insights into reactive sputtering for the optimization of the deposition parameters.