Refractive index determination of materials on thin transparent substrates using ellipsometry

Ellipsometry techniques are often used in the microelectronics industry to monitor substrate cleanliness. The principle of ellipsometry is introduced briefly by describing what is involved when measuring transparent materials. This exercise helps in understanding why absorbing substrates are often used in the ellipsometry technique, without having to derive complicated equations. Moreover, the technique is presented in a simple way with a view to applying and reviewing the concepts of internal reflections occurring in a thin piece of material (substrate). Refractive index measurements of thin transparent substrates such as glass slides can be inaccurate when using ellipsometry because of multiple reflections occurring on both the top and bottom surfaces. Some measurements of the refractive indices of transparent substrates (glass slides) are presented and discussed.