X-ray reflectivity spectra of ultrathin films and nanometric multilayers: Experiment and simulation

Abstract

Amorphous silicon–nitrogen (a–Si1−xNx:H) alloys, thin films, and multilayers deposited by ultrahigh-vacuum plasma-enhanced chemical vapor deposition were studied and modeled by x-ray reflectivity (XRR) measurements. The analysis of XRR data obtained from the single-layer samples allowed us to calculate the density, thickness, and interface roughness of each layer. To check the deposition parameters, the deviation (tnom–texp)/(tnom) of the measured thicknesstexpfrom the nominal thicknesstnomwas evaluated. Based on these results, a simulation of a multilayer film, obtained by deposition alternating stoichiometric and substoichimetric layers was carried out. It is shown that the best fitting is obtained by introducing into the XRR calculation a thickness distribution with a standard deviation related to the deviation (tnom–texp)/(tnom) estimated for the single layers.