Diffusion Transport of Target Material for a Planar Asymmetrical Hollow Cathode Sputtering System

This work investigates the features of a sputtering system with an asymmetrical planar hollow cathode discharge at 10-100 Pa pressures. The asymmetrical hollow cathode discharge occurs between two planar cathodes with different negative potentials. The problem of diffusion transport of sputtered material was formulated and numerically solved. To verify the results of the numerical model, tungsten coatings were deposited at a pressure of 40 Pa. The numerical model results based on the diffusion transport were compared with experimental data. The qualitative agreement between the model and experimental results was demonstrated. For substrates with positive curvature and a size smaller than the output aperture of the sputtering system, a characteristic increase in film thickness to the edges has been experimentally and numerically shown, which is associated with the diffusive nature of the sputtered material transport.