Optical determination of the film thicknesses in multilayer thin film structures

An optical method for determining the layer thicknesses in a multilayer thin film structure is developed and its performance in terms of accuracy and resolving power is characterized. The effects of layer thicknesses, their indices of refraction, light absorption, measurement wavelength range, thickness non-uniformity and unintentional transition layers are characterized. The measurement procedure is applied to oxide, sulphide and fluoride thin film multilayer structures, up to nine individual layers thick, deposited on a glass substrate using atomic layer deposition. In most cases the method is found reliable and error estimates of film thickness vary between 1 and 50 nm depending on the thin film structure in the sample.