Ellipsometry and transport studies of thin-film metal nitrides

The results of a systematic spectroellipsometric and conductivity study of metallic titanium nitride thin films grown on silicon by the ion-beam-assisted deposition technique are presented. The directly measured electrical resistivity is correlated with the contactless, non-invasive ellipsometric method of extractings the free- and bound-carrier response in the infrared, visible, and ultraviolet spectral ranges. The d.c. resistivity of TiN films ranges from similar to 100 to similar to 500 mu Omega cm. The high polarizibility of free carriers at optical frequencies presents non-trivial problems of the measurement optimization. The merit of the ellipsometric data taken at proper angles of incidence in different spectral ranges is discussed for homogeneous and graded layers. For TiN films of a good structural quality, the extrapolation of ellipsometric results is found to be in a fair agreement with d.c. data, providing an optical, contactless way of measuring the electrical conductivity. This can be achieved even with a very simple near-infrared ellipsometer. (C) 1998 Elsevier Science S.A. All rights reserved.