Development of a Thermal Wave Interferometry System for Thin-Film Characterisation.

摘要

This report describes the development of a thermal wave interferometry system for the characterisation of film thickness. The system furnishes a measurement of the relative phase between a modulated heat flux applied to a thin film by a diode laser and the oscillatory temperature response of the film. The relative phase is then converted to a thickness estimate by means of an inverse solution of the heat diffusion equation. A validation of the facility was performed on an experimental test coupon prepared with paint layers of varying thickness. Estimates of the paint thickness profile furnished by the facility were compared to and corroborated by independent measurements obtained using an eddy current probe and a surface profilometer. The system is shown to resolve variations in paint thickness of less than 1.5 micrometer.