High-Sensitivity Infrared Characterization of Ultra-Thin SiO2 Film on Si by Grazing Internal Reflection

Abstract

Infrared absorption in SiO2 ultra-thin film has been characterized by the grazing internal reflection (GIR) method, which is a high-sensitivity infrared spectroscopic technique for measuring weak absorption of ultra-thin dielectric film. It is confirmed from theoretical analysis that GIR is very sensitive to measurements of infrared absorption even in nanometer-order-thick SiO2 film sandwiched between a metal and semiconductor. The spectral configuration of the Si-O-Si stretching mode in the wavenumber range of 1000 to 1400 cm−1 changes drastically by changing the film thickness of 1–100 nm and the incident angle of 20–80°. The experimental spectra agree well with the calculated spectra. The spectral changes are attributed to the fact that optical confinement is subtly changed by the incident angle and the film thickness.