CHARACTERIZATION OF SILICON OXYNITRIDE THIN-FILMS BY INFRARED REFLECTION-ABSORPTION SPECTROSCOPY

Silicon oxynitride thin films deposited by plasma enhanced chemical va por deposition on various substrates have been characterized by infrar ed reflection absorption spectroscopy. Shifts of the LO Si-O vibration al band to lower wave numbers have been observed with increasing N con tent and also with the thickness of the films. We observe that the rat io of LO Si-O vibrational mode wave number to him thickness (v/t) vari es linearly with the ratio of refractive index to thickness (n/t). Thi s linear relationship does not depend on the nature of substrates on w hich 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. (C) 1996 American Vacuum Socie ty.