Measurement of thickness of thin film by fitting to the intensity profile of Fresnel diffraction from a nano phase step

TL;DR

This paper introduces a fitting method to accurately measure thin film thickness at the nanometer scale using Fresnel diffraction patterns, enabling precise and broad-range measurements with modest equipment.

Contribution

It presents a novel, fast fitting approach to determine thin film thickness from Fresnel diffraction intensity profiles, achieving nanometer precision.

Findings

Fitting theoretical intensity profiles to experimental data yields nanometer-scale thickness measurements.

The method provides accurate results across a broad range of film thicknesses.

An optical device based on Fresnel diffraction was developed for practical thickness measurement.

Abstract

Diffraction of light beams from the phase steps due to the abrupt changes in the boundary of step leads to Fresnel fringes that their visibility and intensity profile depend on the change of the step height or light incident angle. The visibility has been utilized in measurements of different physical quantities. In this paper, for the first time to our knowledge, by introducing the fitting method as a fast method we show that by fitting the theoretical intensity distributions on the experimental intensity profiles of the light diffracted from a step at different incident angles, one can specify the step height with few nano meters precision. In addition, we show that this approach provides accurate film thickness in a broad range of thicknesses using modest instrumentation. Furthermore, based on Fresnel diffraction an optical device is manufactured to measurement of thickness of thin films.