IN-SITU MEASUREMENT OF PRINCIPAL REFRACTIVE-INDEXES OF THIN-FILMS BY 2-ANGLE ELLIPSOMETRY

We show that the principal refractive indices of a tilted-columnar bia xial film can be determined from ellipsometric measurements made simul taneously at two angles in the deposition plane during the growth of t he film. The index n(3), perpendicular to the deposition plane, is det ermined by a standard method using interference modulations in the s-p olarized transmittance T-s versus thickness d profile recorded by one ellipsometer. For the computation of n(1) and n(2), we simultaneously log the data for mio profiles of phase retardation Delta versus d. The se profiles are subject to substantial interference modulations, but t he smoothed gradients correspond to material values in the absence of interference. An algebraic solution is developed for n(1) and n(2). Th is requires the columnar angle psi, which we determine from a scanning electron microscope photograph of a section of the film fractured in the deposition plane. (C) 1998 Elsevier Science S.A.