Characterization of silicon oxynitride thin films by infrared reflection absorption spectroscopy

Silicon oxynitride thin films deposited by plasma enhanced chemical vapor deposition on various substrates have been characterized by infrared reflection absorption spectroscopy. Shifts of the LO Si–O vibrational band to lower wave numbers have been observed with increasing N content and also with the thickness of the films. We observe that the ratio of LO Si–O vibrational mode wave number to film thickness (υ/t) varies linearly with the ratio of refractive index to thickness (n/t). This linear relationship does not depend on the nature of substrates on which films are deposited (Al/Si, Si, Si/Al). Our results show that the composition of silicon oxynitride films could be determined directly by measuring the LO Si–O mode position.