Computed tomography imaging of optical emission from copper-sputter deposition plasma: evaluation of the atomic density using the self-absorption effect

Abstract

Optical emission from axisymmetric copper-sputter deposition plasma has been measured in a spatially resolved way, and the radial distribution profiles are obtained using a computed tomography technique. Among the emission spectrum two strong copper emissions at 324.8 and 510.6 nm are analyzed, because both emissions originate from the same excited state, so their intensity ratio reflects the spatial density of ambient copper atoms. As gas pressure and/or discharge power were increased, the decrease in the relative intensity of the 324.8 nm emission was observed experimentally. The density of copper atoms in the plasma is discussed with the optical absorption and the re-emission being taken into consideration.