Unified Analysis of Ellipsometry Errors Due to Imperfect Components, Cell-Window Birefringence, and Incorrect Azimuth Angles*

Abstract

Coupling constants are introduced that determine the extent to which a component imperfection, window birefringence, or azimuth-angle error couple to cause an error of the specimen reflectance ratio. A unified scheme for treating these sources of error is presented. By expressing the coupling constants as functions of the nulling angles, any of the nulling methods can be considered. Results are presented for the compensator at ±π/4 and nulling by the polarizer and analyzer, which show the contributions of the different sources of error to ψ and Δ in the four ellipsometry zones. The limitations of one- and two-zone measurements are discussed. A procedure is described and demonstrated experimentally for determining the quantities characterizing the different sources of error in the ellipsometer. These results can be used in correcting data from one-, two-, or four-zone measurements.