Polarization errors associated with reflective objectives in a micro-spot spectroscopic ellipsometer

A micro-spot spectroscopic ellipsometer covering 1.5–4.8 eV is developed using two infinity-corrected reflective objectives. Only a small portion of the entrance pupil in the objective is used to obtain a ~50 μm × 70 μm spot on a sample. However, non-normal reflections inside the objectives cause experimental errors (up to 2.3° in Δ) when they are arranged symmetrically about a sample. In this paper, we show how to diagnose the polarization errors associated with the reflective objectives and how to deal with them.