General window correction method for ellipsometry measurements.

In the ellipsometry measurement, optical windows attached to the sample chamber are often considered as retarders with small retardation. In reality, the retardation is not always small enough to adopt small angle approximation, and furthermore the retardation over optical beam varies point to point. The general window correction method proposed here copes with both the large birefringence and birefringence variance. This method is valid for correction of both isotropic and anisotropic sample measurements. An isotropic reference sample is premeasured by a spectroscopic Mueller matrix ellipsometer to predetermine the effect of windows. The Mueller matrices of samples such as the silicon and low-dielectric constant film in the chamber were measured, and ellipsometric parameters (Δ, Ψ) of these samples were extracted from these matrices, then compared with ex situ measurement results. The ellipsometric parameters of the reflection diffraction grating were also measured under the window effect and corrected by using the proposed method. Excellent agreements of corrected results with ex situ parameters show the significance of this method.