In-situ time-resolved reflectivity: a technique useful to investigate solid-state transformations

Solid-state transformations occurring in thin films can be studied by directing a laser beam on to the sample surface and measuring the reflected intensity by means of a photodiode. The technique, called Time-Resolved Reflectivity, is an in-situ technique very fast and simple. Under proper conditions, it allows the entire evolution of a transformation to be followed while it occurs during a thermal treatment, allowing the kinetics of the process to be studied. In this work we present a method and some criteria to extract physical information on layered samples interesting for the microelectronic industry. The surface reflectivity depends on the refractive indices (wavelength dependent) of the materials employed and on the thicknesses of the layers. The results extracted from the raw reflectivity data (obtained with a conventional He-Ne 632.8 nm laser) by means of few simple assumptions, are discussed and compared to those obtained with more conventional, but in most cases, destructive and ex-situ techniques. (C) 2002 Elsevier Science B.V. All rights reserved.