BEAM SIZE AND COLLIMATION EFFECTS IN SPECTROSCOPIC ELLIPSOMETRY OF TRANSPARENT FILMS WITH OPTICAL-THICKNESS INHOMOGENEITY

In spectroscopic ellipsometry (SE) measurements of thin films with inh omogeneous optical thickness, the spot size of the probe beam on the s ample surface is a highly critical parameter in the treatment of the e xperimental data. SE measurements were performed on transparent sample s prepared by various techniques: plasma enhanced chemical vapor depos ition of diamond film, spin-coated PMMA films and thermally grown SiO2 film. The first two deposition techniques can produce films with inho mogeneous optical thickness. By comparing SE measurements using differ ent set-up configurations, we demonstrate that a combination of lenses and small diaphragms is most suitable for minimizing the effects rela ted to the optical thickness distribution and light beam divergence. I n this way mistakes are avoided in extracting physical parameters from SE optical modeling of these films.