COMBINED CHARACTERIZATION OF CONDUCTIVE MATERIALS BY INFRARED SPECTROSCOPIC ELLIPSOMETRY AND GRAZING X-RAY REFLECTANCE

Non-destructive, non-contact characterization of conductive materials is an interesting challenge, especially in the field of microelectroni cs. One way to solve the problem is to use the optical properties of t he materials that follow theoretically a Drude law in the infrared reg ion. In this study, spectroscopic ellipsometry in the mid-infrared (up to 17 mu m) is used to extract the optical indices. To evaluate the e lectrical properties, the thickness of the layer is also needed. Due t o the generally high absorbance of these conductive layers, it cannot be extracted directly from the ellipsometric measurements. In this stu dy, we use a complementary technique called grazing X-ray reflectance (GXR). Eleven titanium/SiO2/Si samples with variable titanium thicknes s have been successively examined. The different thicknesses have been determined precisely by grazing X-ray reflectance at the Co K-alpha l ine with the surface roughness of the samples. Conventional X-ray diff raction was also used to determine the crystallinity of the titanium l ayers. Then IR spectroscopic ellipsometry was used to extract the opti cal indices of the different titanium layers and their resistivity usi ng the GXR thickness and the Drude model. Values determined by this me thod compare well with four-point probe resistive measurements made on the same samples. The density of the titanium layers and the thicknes s of the bottom SiO2 layer can be also evaluated in some cases. (C) 19 98 Elsevier Science S.A.