Measuring Thin Transparent Films Precisely: Reliability of reflectometric measurements for optical thickness determination

Fast Fourier transform (FTT) and nonlinear regression analysis are established analysis methods in the context of reflectometric layer thickness determination on thin transparent films. Where applicable, FFT is a very fast method for determining film thickness, but with limitations in resolution. The far more complex nonlinear regression analysis provides more accurate results. But it also has its problems which are discussed here.