Experimentally unraveling the energy flux originating from a DC magnetron sputtering source

Abstract

We present investigations of the energy flux in DC magnetron sputtering for 15 different target-gas combinations. The utilized gases were Ar, Kr and He which were studied using targets made of Ag, Al, Cu, Ti and W. The effect of parameter variations (distance, pressure and discharge power) was investigated by calorimetric measurements utilizing a passive thermal probe. For the variation of discharge power, supplementary measurements of plasma parameters and deposition rate were performed using a planar Langmuir probe and a quartz crystal microbalance. The obtained results were used to gain better insight into the different contributions to the integral energy flux. The measurements illustrate clearly that, depending on the target material and on the target gas combination, the main mechanisms generating the energy flux can vary dramatically. For small gas-target mass ratios, reflected neutrals were identified as the main contribution of the energy flux while for combinations with high sputter yield, condensation and kinetic impact of sputtered particles were found to be the most relevant. For thermally poor conducting targets as in the case of titanium, the target can heat up significantly resulting in a strong energy flux from heat radiation which dominates the otherwise modest energy flux.