Papers by Keyword: Spectroscopic Ellipsometry (SE)

Abstract: A chemically selective film, usually of optical quality, is a key component of optical and electrochemical sensors. We have examined the dynamics of various thin selective films by spectroscopic ellipsometry and attenuated total reflectance (ATR) spectroscopy. Spectroscopic ellipsometry provided a non-invasive method for measurement of optical constants (n(λ), refractive index; k(λ), extinction coefficient) and thicknesses of thin selective films which were conditioned in time by solvent and penetrant mass transport. The methods we have developed allowed us to characterize film dynamic response, stability, and chemically specific mass transport even to the point of quantitatively modeling both transport and structural changes. The ATR spectra of thin, highly absorbing films are distorted both by reflectance and interference phenomena. Enhanced absorbance was observed under film leaky mode conditions.

Abstract: Modern material technology relies increasingly on processes for surface modification and coating. Generally, we are lacking a possibility to monitor the progress of such processes. Thus the outcome can only be analyzed after the end of the whole process cycle. We are proposing to use spectroscopic ellipsometry (SE) as an on-line monitoring tool. SE, as an optical method, is not affected by high temperatures, process gases, plasmas, etc. It can be used as a monitoring tool or a sensor for closed loop control of processes. The main difficulty is the on-line interpretation of SE data. Depending on the nature of the process monitored or controlled, different models are used for the interpretation. These models predict the SE response depending on different parameters describing the surface under investigation. A fitting process is used to solve the inverse problem, i.e. extracting material data from the SE spectra. We expect increased process stability and shorter development time as a practical benefit from the use of SE.

Abstract: Titanium dioxide films were deposited using DC magnetron sputtering technique onto silicon substrates at ambient temperature and at an oxygen partial pressure of 7×10 –5 mbar and sputtering pressure (Ar + O2) of 1×10–3 mbar. The composition of the films, analyzed by Auger Electron Spectroscopy (AES), revealed the stoichiometry with an O and Ti ratio of 2.08. The optical constants of the as-deposited TiO2 thin film were determined by Spectroscopic Ellipsometry in the photon energy range 1.2 to 5.5 eV at room temperature. The measured dielectric-function spectra reveal distinct structures at energies of the E1, E1+D1 and E2 critical points due to interband transitions. The Dielectric constant values were found to be substantially lower than those for the bulk TiO2. The dielectric related optical constants, such as the refractive index, extinction coefficient, absorption coefficient and normal incidence of reflectivity are presented and analyzed. The deposited films were calcinated at 673 and 773 K. The influence of post-deposition calcination on the Raman scattering of the films was studied. The existence of Raman active modes A1g, B1g and Eg corresponding to the Raman shifts are reported in this paper. The improvement of crystallinity of the TiO2 films as shown by the Raman scattering studies has also been reported.

Abstract: The compatibility of chemical solutions with different pH is studied on microporous silica-based (SiOCH) and mesoporous methylsilsesquioxane (MSQ) based low-k materials. The surface and bulk properties of as-deposited and O2/CF4 plasma-treated low-k films have been studied after several wet treatments.

Abstract: Porous surface layers were studied in a series of p-type Si samples etched anodically in electrolytes based on hydrofluoric acid. The optical response of the structure consisting of substrate and surface layers was investigated by spectroscopic ellipsometry in the range 1-5 eV. The experimental results were compared with calculations, which model the optical response of a multilayer structure. The model parameters were compared to the structural data obtained by AFM and SEM studies. The experimental investigations and model calculations revealed the regularities in the dependence of the optical response on the doping degree of substrate and parameters of technological procedure.