Deposition of Si-DLC films with high hardness, low stress and high deposition rates

In this work silicon-incorporated diamond-like carbon (Si-DLC) films were produced by plasma enhanced chemical vapor deposition (PECVD) from gaseous mixtures of CH4 and SiH4. A study of the influence of self-bias and gas composition on the mechanical and structural properties of the films was carried out. Results show that films deposited at high self-bias present high deposition rates, low stress and surprisingly high hardness. Increasing silane concentration in the gas phase leads to an enhancement of the observed effects. Compositional and structural characterization show that deposition at high bias leads to increased sp2 character and rather low silicon contents. Increasing the silane content in the plasma leads to an increase in the sp3 fraction of the films, and yields a further reduction of stress with almost no effect upon hardness. In this way, the possibility of producing films with high hardness (>20 GPa), low stress (∼0.5 GPa) and high deposition rates (>40 nm/min) has been demonstrated. This result is thought to be very important from the point of view of technological applications.