Effects of thermal annealing and Si incorporation on bonding structure and fracture properties of diamond-like carbon films

The effects of thermal annealing and Si incorporation on the structure and properties of diamond-like carbon (DLC) films were investigated. As-deposited DLC film (DLC) and Si incorporated DLC film (Si-DLC), both with and without thermal annealing, were analyzed for bonding structure, residual stress, film thickness, elastic modulus and fracture properties using Raman spectroscopy, wafer curvature, nanoindentation, four-point bend fracture testing, and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy clearly showed that thermal annealing of DLC films promotes more sp2 bonding character, whereas Si incorporation into the films promotes more sp3 bonding character. Interfacial fracture energies, film hardness and elastic modulus, and residual film stress were all found to vary strongly with the degree of sp3 bonding in the DLC film. These changes in mechanical properties are rationalized in terms of the degree of three dimensional inter-links within the atomic bond network.