Structural characterization of alloyed Al/Ti and Ti contacts on SiC

In this work a structural characterisation of Al-rich (72 wt. % Al) Al/Ti alloyed electrical contact on SiC is presented and compared with that obtained on Ti alloyed contacts. Rutherford Back Scattering in the Channelling mode (RBS-C) and Transmission Electron Microscopy of cross-sectioned specimens (XTEM) in various analysis modes were used as structural characterisation tools. The results of this structural characterisation have revealed that the Al/Ti alloyed contacts consist mainly of a Ti3SiC2 phase. Protrusions of the reacted metal layer into the semiconductor substrate have also been clearly identified. Evidence of Al-rich surface amorphous agglomerates are also reported. At variance with this morphology, a nearly flat interface between the reacted layer and the substrate is found in the case of a Ti alloyed contact. This reacted contact consists of three superposed layers that from surface to substrate are mainly composed by TiC, Ti5Si3 and Ti3SiC2 grains. A comparison of these experimental results with parallel electrical investigations suggests that the ternary compound is not responsible for the better ohmic behaviour observed in Al/Ti-SiC alloyed contacts with respect to the Ti-SiC case.