Electrochemically measured porosity of magnetron sputtered TiN films deposited at various substrate orientations

TiN layers were deposited by magnetron sputtering on polished stainless steel substrates, the position of which was changed in steps from parallel to perpendicular relative to the target surface. Substrate target distance was varied between 25 and 50 mm. Bias current density and substrate temperature at the beginning of deposition were also varied. The porosity of the films deposited under these circumstances was measured by an electrochemical method. The double layer capacity electrolyte/TiN film is a measure of the porosity and the true surface area of the deposited film. Dense films were deposited in all substrate positions when the starting temperature was around 300 °C and the bias current densities were above 2 mA/cm². With bias current densities below 1 mA/cm² or no bias and a position of the coated plane perpendicular to the target surface, the true surface of the film is enlarged to 500 times that of the geometrical area of the substrate used. The structural changes responsible for the increase in the porosity are shown in scanning electron microscope (SEM) micrographs.