Ellipsometer analysis in the n–k plane

Ellipsometry is an optical analytical method based on measuring the change in polarization state of reflected or transmitted polarized light. A major challenge of the method has been the computation of reflecting surface physical parameters of interest from the raw measured data. This arises because the most common relationship is transcendental and cannot be inverted thus requiring numerical methods. The most popular methods are variations of least squares, for example Levenburg–Marquardt. These methods are plagued by local minima inherent in least squares. The work presented is a description of the geometry of the n–k plane for the case of a single measurement on a single layer film. This geometry lays the groundwork for a set of solution algorithms which are much more powerful and convenient than existing algorithms. It also illustrates the multiple solution problems inherent in least squares methods.