Correlation of target properties and plasma parameters in DC magnetron sputtering with Langmuir probe measurements

Abstract

Utilizing different manufacturing methods for producing sputtering targets leads to significant variations in target microstructure with the latter showing a pronounced impact on the performance of the target in direct current magnetron sputtering (DCMS) in terms of varying sputtering yields. This study aims at correlating measured plasma parameters on the one hand with varying microstructure of molybdenum targets on the other hand. To this end, the sputtering performance of targets manufactured by means of selected powder metallurgy as well as melting metallurgy processes in DCMS is experimentally investigated. Ranging over two orders of magnitude, the mean grain size is identified as the major varying microstructural parameter of the investigated targets. Measurements of spatially varying plasma parameters under steady state sputtering conditions are carried out by means of a Langmuir probe moved over the target at several distances perpendicular to the target top surface. The largest differences in the measured parameters are found in the vicinity of the target surface. In particular, the electron density is found to decrease with increasing mean grain size.