Three-dimensional thickness and property distribution of TiC films deposited by DC magnetron sputtering and HIPIMS

Abstract

High power impulse magnetron sputtering (HIPIMS) is known for ionising a reasonable amount of the deposition particles emitted from a magnetron sputtering source. Besides improved density and mechanical properties of the deposited films a higher thickness uniformity in three-dimensional structures has also been reported as a benefit of this technology.In this work TiC thin films were deposited from a 50mm diameter TiC-target in Ar atmosphere using direct current magnetron sputtering (dcMS) and HIPIMS with a peak power density of 1kW/cm2. A special three-dimensional structure with three different drilled blind holes (10, 4 and 2mm diameter) was built and used as the substrate. Flat polished high speed steel samples were mounted as parts of the side wall and the bottom of each hole in such a way that the coating thickness and hardness could be detected afterwards at several locations. It turned out that in most cases HIPIMS did not show any improvement in the homogeneity of the film thickness. In fact mostly the dcMS deposited films even exhibited better thickness uniformity. However, the differences between dcMS and HIPIMS remained rather limited at an Ar pressure of 0.4Pa, whereas at 1Pa they have been much more significant. Applying a substrate bias voltage of −50V again nearly did not show any important impact. On the other hand the film properties in part changed distinctly. The hardness of the dcMS deposited TiC-films at the hole walls was up to 4 times lower than that of the HIPIMS deposited ones. Examination of the samples prepared by focused ion beam (FIB) and observed by scanning electron microscopy revealed a far more porous film morphology as an obvious reason for the severe drop of the hardness of the dcMS films at the side walls. The samples facing the magnetron exhibited very high hardness values (>2500HV) which were nearly independent of the deposition method.A detailed overview and discussion of the data will be provided, together with ionisation data obtained by optical emission spectroscopy.