Using reflectometry to obtain parameters such as thickness, absorption coefficient and refractive index is a very mature technique. Nanometrics expertise in this field dates back into the early 1970’s. For years, the Nanospec metrology series has been the reference in optical metrology using reflectometry.
Every transparent material is characterized by its dispersion curve. The dispersion defines, how much light is absorbed by the material and how much light is refracted. These two parameters vary over wavelength and are specific to every material. When light travels through a material and is reflected by a substrate, it will form a interference pattern with the surface reflected light. This interference pattern contains the parameters of the material such as thickness (T), refractive index (n) and absorption coefficient (k).
To extract these parameters from the reflected light, a model is laid over the experimental light spectrum and the model parameters are floated until the model matches the experimental light spectrum.
While the optical setup of a reflectometer does have a significant influence to the quality of data and accuracy of a measurement, the modelling capabilities contribute as well. Nanometrics newest generation of table top and standalone reflectometers benefit from more than 30 years of optical competence and our latest generation of analysis & modelling software – the industry leading NanoDiffract™ software. Even complicated multi-layer structures can be measured and modelled in an easy and intuitive way.