Showing papers by "E. R. G. Eckert published in 1971"

Methods for Determining Film Thickness and Optical Constants of Films and Substrates

Abstract: Several methods are developed for deducing optical constants and film thickness from measurements of the monochromatic specular reflectance for linearly polarized radiation at varying angles of incidence. Consideration is given both to transparent films and to slightly absorbing films on absorbing substrates. The methods for transparent films are based on the property that, at any angle of incidence, there are upper and lower bounds on the reflectance that, for given substrate properties, depend only on the index of refraction of the film. For slightly absorbing films, an additional relevant property is that the angular positions of the maxima and minima of the reflectance curve are insensitive to the extinction coefficient of the film. Utilization of the foregoing properties in conjunction with measured distributions of reflectance vs incidence angle leads to the determination of the refractive indices and extinction coefficients of films and substrates as well as the film thickness. Monochromatic reflectances measured for two film–substrate pairs and a pure metal were used to illustrate the application of the methods. A He–Ne laser served as the source of monochromatic polarized light in the experiments.

Film Thickness and Refractive Indices of Dielectric Films on Dielectric Substrates

Abstract: Methods are described for determining the refractive indices of dielectric films and substrates and the thickness of the film. The determination makes use of a single measured distribution of monochromatic, specular reflectance as a function of incidence angle. The methods are based on certain properties of the reflectance maxima and minima, which properties are deduced from electromagnetic theory. Either perpendicular-polarized or parallel-polarized light may be employed; the latter has some advantage, in that it provides a cross check on one of the results and also facilitates the treatment of very thin films.