Refractive Index of SiO2 Films Grown on Silicon

Abstract

By more precise variable angle monochromatic fringe observation (VAMFO), it has been found possible to improve the precision of thickness determinations of transparent thin films (800 Å to several microns) on reflective substrates to better than 0.1%, and to extend the determination of the refractive index to films as thin as 900 Å. The measured refractive indices (at 5459 Å) of silicon dioxide films grown in steam and/or dry oxygen (atmosphere pressure) at 980° to 1200°C varied from 1.461₀ to 1.462₄ for 3500‐ to 6800‐Å films. These compare with the refractive indices (at 5461 Å) of 1.461₄ for a thick (2.148 μ) steam‐grown film (at 980°C) and 1.461₉ for a thick (2.135 μ) oxygen‐grown film (at 1200°C). The technique has also been used to measure the refractive indices of thin films (>900 Å) other than thermal SiO₂.