Reflection and transmission ellipsometry measurement under incoherent superposition of light

Abstract

Optical constants and thickness of a single layer on the transparent substrate can be extracted simultaneously from four ellipsometric parameters - 𝑟 , ∆ 𝑟 ,  𝑡 , ∆ 𝑡 -, which are obtained through reflection and transmission ellipsometry measurement at a single wavelength and a single incidence angle. A transparent substrate, however, induces the problem of backside reflections, and then incoherent superposition of light. In this work, the effects of such reflections were empirically investigated as a function of incident angle and analyzed by using single-point measurement results obtained with a commercialized spectroscopic ellipsometer. Our study shows that at the Brewster angle illumination, the effect of backside reflection can be minimized. Based on this result, a reflection and transmission imaging ellipsometer was configured for the measurement of a Si film deposited on a quartz glass plate. The measurement results showed the availability, as well as the limitation, of the reflection and transmission imaging ellipsometry.