A spatially resolved spectroscopic study of ionization in the planar magnetron discharge

Spatially resolved optical emission spectroscopy has been used to investigate the sputtering and ionization of titanium in a DC planar magnetron using argon as a sputtering gas. Maps of argon and titanium atomic and ionic emission have been obtained. Characteristic emission patterns have been identified and explained by the sputtering of atoms from the magnetron target and their subsequent ionization in the dense plasma at the magnetron target. The inverse Abel transformation was used to reconstruct plasma emission profiles, revealing that the non-uniform erosion profile at the magnetron target leads to a non-uniformity in plasma properties some distance into the discharge. An enhanced metal ionic content has been found in the plasma on the axis of symmetry of the discharge, and this has been explained by an enhanced lateral diffusion of metal ions arising from the change in momentum of sputtered metal during collisional ionization by metastable argon atoms.