A Linear Model for the Interpretation of Optical Emission Spectroscopy Measurements in Low Pressure DC Magnetron Sputtering

Abstract

For a balanced dc magnetron discharge a linear model for the formation of excited and ionized species is presented. The consideration is based on collisional kinetic theory and a correlation of discharge current with ionization rates, and leads to normalized rate coefficients. The electron energy distribution changes according to the determining external parameters, but needs neither to be known in detail nor to be of Maxwellian type.The model calculations are consistent with measurements done by optical emission spectroscopy (OES) on the magnetron sputtering of aluminium in argon discharges. The dependences of optical emission intensities on discharge current and on argon pressure show that both, excited argon atoms as well as excited argon ions, are generated from neutral argon by direct, fast electron impact. It is additionally shown that a t least for low argon pressure the excitation of aluminium atoms is also caused by direct electron impact.