Dependence of the mechanical properties of Cr-DLC films on the acetylene flow and substrate bias

Internal stress and hardness of chromium-diamond like carbon (Cr-DLC) films deposited by reactive sputter deposition from a chromium target in argon/acetylene atmosphere have been studied as a function of the acetylene gas flow and substrate bias. The Cr-DLC films were deposited using a dc current of 150 mA and substrate temperature of as-deposited. The films were characterized by Raman spectroscopy, Auger electron spectroscopy (AES), scanning electron microscopy (SEM), wafer curvature for stress determination and nanoindentation. The internal stress changes from tensile to compressive for acetylene flow higher than 0.3 sccm. Also, the internal stress and hardness increase with the substrate bias. From Raman spectroscopy the ratio ID/IG changes with the acetylene flow and the substrate bias. From AES the chromium content decreases with both, the acetylene gas flow and substrate bias. Based on the experimental results, it is concluded that the variation in compressive stress and hardness are associated to changes in the chemistry and microstructure of the Cr-DLC coatings.