Combined Characterization of Conductive Materials by Infrared Spectroscopic Ellipsometry and Grazing X-ray Reflectance,

Abstract Non-destructive, non-contact characterization of conductive materials is an interesting challenge, especially in the field of microelectronics. One way to solve the problem is to use the optical properties of the materials that follow theoretically a Drude law in the infrared region. In this study, spectroscopic ellipsometry in the mid-infrared (up to 17 μ m) is used to extract the optical indices. To evaluate the electrical properties, the thickness of the layer is also needed. Due to the generally high absorbance of these conductive layers, it cannot be extracted directly from the ellipsometric measurements. In this study, we use a complementary technique called grazing X-ray reflectance (GXR). Eleven titanium/SiO 2 /Si samples with variable titanium thickness have been successively examined. The different thicknesses have been determined precisely by grazing X-ray reflectance at the Co K- α line with the surface roughness of the samples. Conventional X-ray diffraction was also used to determine the crystallinity of the titanium layers. Then IR spectroscopic ellipsometry was used to extract the optical indices of the different titanium layers and their resistivity using the GXR thickness and the Drude model. Values determined by this method compare well with four-point probe resistive measurements made on the same samples. The density of the titanium layers and the thickness of the bottom SiO 2 layer can be also evaluated in some cases.