Hollow cathode effect modified time-dependent global model and high-power impulse magnetron sputtering discharge and transport in cylindrical cathode

High-power impulse magnetron sputtering boasts high ionization, large coating density, and good film adhesion but suffers from drawbacks such as low deposition rates, unstable discharge, and different ionization rates for different materials. Herein, a cylindrical cathode in which the special cathode shape introduces the hollow cathode effect to enhance the discharge is described. To study the discharge performance of the cylindrical cathode, a hollow cathode effect modified time-dependent global model is established to fit the discharge current pulses. The simulation results indicate that the cylindrical cathode has relatively large Hall parameters of 24 (700 V) to 26 (1000 V). Compared to the planar cathode, the cylindrical cathode has a larger plasma density as a result of the hollow cathode effect. In addition, the ionization rate and ion return probability increase by about 3.0% and 4.3%, respectively. Particle transport derived from the plasma diffusion model shows that the magnetic field enables further diffusion of ions than atoms, resulting in nearly pure ion deposition on the substrate. The deposition rate and ion current measured experimentally support the simulation model and results, and this model provides a universal platform to simulate plasma systems with similar structures.