Optical Characterization Of Silicon Oxycarbide Thin Films

The local bonding environments in silicon oxycarbide thin films with different amounts of carbon were analyzed using the complementary optical techniques of Fourier transform infrared (FTIR) and Raman spectroscopies. Film formation was accomplished by low-temperature (250°C), plasma-enhanced CVD using SiH4, CH4 and O2 as the source gases. Control samples were also deposited using only SiH4 and CH4, and SiH4 and O2 source gases. The films were then subjected to rapid thermal annealing at 800, 900 and 1100 °C for 90 seconds. Results showed that carbon incorporation into the oxide hinders stoichiometric SiO2 formation upon annealing at 800 and 900 °C. Annealing at 1100 °C produced films which showed stoichiometric SiO2 formation. Phase separation into nano-crystalline silicon (<5 nm) and a mixture of amorphous silicon carbide and silicon oxide was also observed upon annealing, with crystallite size decreasing as the carbon content of the films was increased.