Investigation of multilayer thin films using ellipsometry

Light emission from silicon-based materials is a very important research area for optoelectronic and display applications. It is important to derive a practical light source from silicon in order to have complete photonic integrated circuits on silicon. An efficient silicon based light emitting device would revolutionize the silicon photonics field, and thus numerous efforts have been undertaken to develop silicon as a viable optical material. Not only will the Silicon based light source be able to provide an easy route to integrate with silicon electronics but also be compatible with current fabrication technology. In this work, the optical properties of a-SiNx:H/Si02 multi layers thin films have been investigated using spectroscopic ellipsometry (SE). Plasma Enhanced Chemical Vapor Deposition (PECVD) was used to fabricate multilayer thin films. The ellipsometric data was acquired using a rotating analyzer J. A. Woollam variable angle spectroscopic ellipsometer in the wavelength range of 270 nm to 1700. The SE experiments conducted were quite extensive in terms of the range of energy and the angles at which the measurements were performed. SE itself is not a direct readout type technique. It is actually a model-based technique. Thus, it is important to build correct and suitable model for a particular material in the SE fitting. In this project, several dispersion models are investigated to find the one which is best suitable for the fitting of a-SRN. The fitting of the ellipsometric data was carried out using the WVASE32™ software. Several samples were characterized using SE and the data were fitted by software Wvase32 using two dispersion models: Tauc-Lorentz (TL) model and TL with the inclusion of the Urbach tail. Optical constants for the single layer as well as multilayer thin films were obtained using both TL and TLU models. The optical constants obtained from both the models have been compared. Thickness of the films, barrier and bulk layer obtained through SE have been compared with the TEM results and are found to be in agreement with each other, thus verifying the accuracy of the SE results. Results obtained from both the models were also compared and it was observed that TLU gave better results.Master of Science (Electronics