Optical depth profiling by attenuated total reflection Fourier transform infrared spectroscopy: A new approach

A new analytical technique for depth profiling using multiple-angle attenuated total reflection Fourier transform infrared spectroscopy has been developed. The analysis does not require prior knowledge of the profile of the complex refractive indices with respect to depth from the surface for the depth profiling calculation. This depth profiling analysis consists of two steps. First, the estimated complex refractive index profile is obtained by solving a set of linear equations of absorptance. Second, the reflectances from experiment are nonlinearly fitted with those from exact optical theory. The estimated complex refractive index profile from the first step is used as a trial profile for the fitting. The converged complex refractive index profile from the fitting is then defined as the reconstructed complex refractive index profile of the film. The noise-added reflectances are used as experimental data to show the applicability of the new analytical approach.