Epitaxial cobalt silicide formation using a Co/TiSix bilayer on Si (1 0 0) by sputtering

Abstract

Annealing a Co/Ti bilayer by sputtering on the Si substrate offers higher probability of epitaxial growth and less Si consumption than annealing of a single Co layer on the Si substrate. Nevertheless, the Co/Ti bilayer epitaxy method does not solve the Si consumption problem satisfactorily. In this communication, a new CoSi2 epitaxial growth technique of annealing a Co/TiSix bilayer on Si (100) is investigated for the first time. Cobalt silicide thin films obtained using the Co/TiSix bilayer have been analyzed using X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) techniques to identify the phases and to investigate the surface and interface morphologies and the chemical composition. The XRD spectra show the epitaxial growth of CoSi2 layer with (200) crystallographic orientation on the Si (100) substrate for a Co/TiSix bilayer while the Co–Ti–Si spinel phase is detected over the annealing temperature range of 400–600 °C. The AES analysis indicates that native oxides on the silicon substrates are removed by Ti at the beginning of RTA and Co diffuses inward so that an epitaxial CoSi2 layer could form. The AFM micrographs show smooth surface and the cross-sectional high-resolution TEM analysis reveals that the layer is composed of the CoSi2 epi-layer formed on the Si substrate. Also it is found that Si consumption during silicidation annealing for the Co/TiSix bilayer formed by sputtering has been significantly reduced compared with that for the Co/Ti bilayer formed by sputtering.