Angular distribution of sputtered neutrals in a post magnetron geometry: Measurement and Monte Carlo simulation

Abstract

The angular distributions of Cu particles sputtered from a cylindrical (post) magnetron were measured in a pinhole arrangement at various working gas pressures. The differentially pumped pinhole camera—described in a previous article—allows measurements in a pressure range up to 10 Pa and samples the three-dimensional distributions in planar sections. Two different planes, namely, parallel and perpendicular to the magnetron axis, were selected for the investigation. Cu was sputtered by Ar ions with an energy of about 0.5 keV from a post magnetron with a very uniform erosion zone. The orifice of the pinhole camera was located at a distance of 50 mm from the cathode surface and in the middle of the erosion zone. The working gas pressure was varied from 0.1 to 1 Pa. The angular distribution of particles was deduced from thickness measurements of films deposited on a semicircular substrate with a 21 mm radius centered around the pinhole. The pressure-dependent amount of scattering was studied by comparing the measured angular distributions with either analytic results neglecting scattering and with those calculated by Monte Carlo simulations of the gas phase transport. Experiment and simulation give good agreement, especially in the low-pressure range. For high working gas pressures good quantitative coincidence of calculation and experiment can only be achieved by introducing a pressure-dependent exponent n in the cosn θ particle emission characteristic from the target. Generally it can be concluded that, for all considered gas pressures, sputtered neutrals show angular distributions far from isotropy.