Simultaneous determination of thickness and refractive index of thin films by mean squared error analysis of reflectivity measurements

Abstract

Reflectivity equations give a relation of thin film thickness and index of refraction to the amount of reflected light, thus measuring the reflected beam is a simple way to determine both the thickness and index of refraction of a thin film. In this study, we use reflectivity measurement to obtain simultaneously the thickness and refractive index of a single layer thin film. The feasibility and accuracy of the method was verified by comparing values with standard SiO₂/Si thin films. The mean-squared error between the experimental data and numerical simulations was calculated and we show that for thin films with thickness of at least 100 nm, both thickness and refractive index can be determined simultaneously. Lower than this value, thickness can also be measured if the index of refraction of the film is known.