A fast genetic algorithm to fully characterize transparent-film-absorbing-substrate systems using ellipsometry

摘要

We show that only one measurement of the ellipsometric function p at one angle of incidence and one wavelength is totally sufficient to determine the optical constant of the filmN_1, its thickness d, and the substrate optical constant N_2. Obviously, it's also sufficient to only characterize the film; determine N_1 and d, and to only characterize the substrate; determine N_2 and d. A genetic algorithm (GA) is presented that is based on a physical condition of the film-substrate system. This GA is used to characterize the system in those three separate cases. We show that by removing the film thickness from the fitness function of the GA, the computational effort to characterize the film is reduced from 20 000 to 69 calculations. And that to characterize an absorbing layer is reduced from 80 000 to 180. An error analysis is presented that shows the GA is resilient to random experimental errors.