Synthesis and characterization of BON thin films using low frequency RF plasma enhanced MOCVD: Effect of deposition parameters on film hardness

With the expectation of getting hard material, we have firstly grown the BON thin film by radio frequency plasma enhanced metal-organic chemical vapor deposition with 100 kHz frequency and trimethyl borate precursor. The plasma source gases used in this study were Ar and H₂, and two kinds of nitrogen source gases, N₂ and NH₃, were also employed. The as-grown films were characterized with XPS, IR, SEM and Knoop microhardness tester. The film growth rate was influenced both by substrate temperature and by nitrogen source gas. It decreased with increasing the substrate temperature, and was higher by using NH₃ rather than by N₂. The hardness of the film was dependent on several factors such as nitrogen source gas, substrate temperature and film thickness due to the variation of the composition and the structure of the film. Both nitrogen and carbon-content could raise the film hardness, on which nitrogen content had stronger effect than carbon. The smooth morphology and continuous structure yielded high hardness. The maximum hardness of BON film was approximately 10 GPa.