Effect of air annealing on mechanical properties and structure of SiCxNy magnetron sputtered films

Amorphous SiCxNy films (of 2.2–2.7μm) were deposited on Si(111) substrates by reactive DC magnetron sputtering. The SiC target with small excess of carbon was sputtered at various N2/Ar gas flow ratios (0–0.48). The as-deposited films were additionally annealed at temperatures of 700, 900 and 1100°C in the air during 30min and at 900°C in vacuum during 1h. The depth profile of hardness and elastic modulus (nanoindentation), change of the film thickness, film composition and structure (Raman and Infrared spectroscopy) were investigated in dependence on annealing temperature and content of nitrogen. The hardness of the as-deposited films decreases with the growth of N2/Ar flow ratio. Air annealing at 700°C leads to atomic short-range ordering in the amorphous SiCxNy films that significantly increases their hardness and elastic modulus at all used loads (10–100mN). The hardness of the SiCxNy films annealed in air at 900°C reduces when measured at low indenter loads (10–20mN) due to onset of top layer oxidation. Hardness of inner layers, measured at 50–100mN loads, increases approaching values exhibited by the vacuum annealed films. Air annealing at 1100°C leads to intensive surface oxidation and formation of graphite-like structure in carbon clusters of inner layers. The hardness and oxidation resistance of the investigated SiCxNy films reduce with the increase of N2/Ar ratio. •Hardness and oxidation resistance of a-SiC film are higher than those of a-SiCxNy (C/Si~1).•Hardness behavior reflects temperature induced changes in structure and composition.•Atomic short range ordering leads to hardness increase at 700°C.•Oxidation decreases surface hardness after annealing at 900 and especially 1100°C.•Higher nitrogen content facilitates graphite-like ordering in C clusters at 1100°C.