Simultaneous measurement of film and substrate optical parameters from multiple sample single wavelength ellipsometric data

A procedure has been developed for the accurate measurement of film and sub strate optical parameters from the multiple sample single-wavelength ellips ometric data. The dimensional reduction of the unknowns from newly formulat ed ellipsometric functions, the root selection and the thickness-dependent integer deduction enhance the rapidity of finding solutions and the converg ence from a wide range of initial guesses while avoiding undesirable soluti ons. An error analysis carried out shows that the procedure is very resista nt to the propagation of angular errors and allows the estimation of optimu m film thickness ranges under which the parameters can be accurately found. The standard SiO2/Si structure is particularly studied using the procedure that is further illustrated with the experimental data on Ni/BK7-glass str uctures. The SiO2 film refractive index and thickness are thus shown to be accurately determined when sought along with the substrate optical constant s. Moreover, the film and substrate real indexes are not altered in the pre sence of an interface layer between the film and the substrate while its ex istence is indicated by a systematic lowering of the Si substrate extinctio n coefficient. The procedure can be efficiently used in the continuous real -time optical characterization of films growing on substrates.