Heterostructure thickness measurement is an important quality control step after deposition. It can work together with the in-situ real-time thickness control or instead of it. Heterosctructure filmstack, typically, consists of repeated alternating layers of low and high reflective index material, e.g. Al oxide and Zn oxide. Double layer can be repeated 10s or 100s of times – typically from 60x to 200x. They are widely used for filters, anti-reflection coatings and other applications. One of these applications is LED and semiconductor laser: heterostructure filmstack, in this case, is used to concentrate light radiation in the narrow wavelength range. Frequently, optical constants of the constituent materials are measured separately and only thickness is measured in the actual heterosctucture. Unfortunately, it is not always possible because materials in heterostructure may have different optical properties. It is possible, however, to measure both thickness and optical constants assuming that all the same material layers have identical properties. How to measure heterostructure? - Heterostructure, typically, includes thin layers of the metal oxides. In this case, it is best to use MProbe 20 UVVis measurement system - Use of the linked layers helps reduce the number of independent layers for the first step in the data analysis - If the fit to the measured data is not good – one can try to add optical constants of one of the materials to measured parameters. It is likely that they are different from the previously measured data - If the fit improves but still not perfect – one can fix the optical constant at the latest results and let thickneses of the individual layers flow independently
