SPECTROSCOPIC ELLIPSOMETRY CHARACTERIZATION OF INDIUM TIN OXIDE FILM MICROSTRUCTURE AND OPTICAL-CONSTANTS

Indium tin oxide (ITO) is a transparent conducting oxide in wide use t oday, ITO can be difficult to work with since this material displays a complicated (graded) microstructure, and the optical properties of IT O can vary widely with deposition conditions and post-deposition proce ssing. For this reason it is common to characterize ITO films via opti cal measurements. However, accurate results are difficult to obtain du e to the graded microstructure of the film introducing variations in t he refractive index throughout the film thickness. Thus the typical IT O film does not have a single, well-defined set of optical constants d ue to grading in the microstructure. Several optical models for ITO wi ll be presented which include the graded microstructure of the materia l and work reasonably well in fitting spectroscopic ellipsometry data for ITO film thickness, index grading, and optical constants. Since th e film thickness, optical constants, and microstructure grading are al l intermixed in the experimental data the issue of determining a uniqu e best-fit optical model for ITO will also be discussed. (C) 1998 Else vier Science S.A.