Target erosion process during broad ion beam sputtering using 3D modeling of ion trajectories

Abstract

Understanding the distribution of particles sputtered from a target requires an appreciation of how ions impinge on the target. In pursuit of this goal, a fully three-dimensional model of the ion trajectories in a broad ion beam, assuming full space charge compensation, Gaussian emission characteristics of the beamlets, and beamlet deflection, was constructed. The modeled ion trajectories were used to simulate target erosion, enabling a comparison between the modeled erosion and the experimental erosion. The focus was on Ar and Xe ion species at ion energies in the range of 1.4–1.9 keV and on target materials, Si, Ta, and SiO2. Conclusions were drawn on the erosion process, the potential radial inhomogeneity of the plasma in the discharge chamber of the ion source, and on the opening angle of the emission characteristics of the beamlets. For the investigated process and an applied target tilt angle of 55°, the model verified that material-specific and angle-dependent ion–solid interaction mechanisms at the atomic level played only a minor role in the target’s macroscopic surface modification in the context of the qualitative distribution of the erosion profile. In contrast, the applied sputtering geometry played a significant role.