Evaluating thin-film multilayer structures by X-ray diffraction

摘要

Thin-film multilayer structures, e.g. InP/InGaAs multiquantum well (MQW) structures 21, 22 are evaluated as to the thickness and composition of metamorphic layers 23 - 27 formed at the heterointerfaces by calculating X-ray diffraction patterns of assumed structures (a) with no such layers; (b) with layers of predetermined composition and thickness; and (c) with layers having predetermined fluctuations of composition (or thickness); and varying the predetermined parameters to match corresponding aspects of the calculated diffraction pattern with those of the measured pattern and thereby estimate the actual value of those parameters. The matches are (a) an overall pattern match, which indicates an ideal structure with no metamorphic layers; (b) coincidence of the positions of the main and satellite peaks in the respective patterns, which indicates the average layer composition and thickness; and (c) coincidence of the interference fringes around the satellite peaks, which indicates the fluctuations of composition (or thickness) in the layers. IMAGE