Oxygen sinks in reactions of thin bilayer refractory metal films with SiO 2 substrates

Abstract

The reactions of thin single chromium or tantalum films and thin bilayer Zr/V, V/Zr, Zr/Cr, Cr/Zr, Ta/Cr and Cr/Ta film stacks with SiO 2 substrates in the temperature range from 650°C to 1000°C in vacuum have been studied by Rutherford backscattering spectrometry (RBS) and X-ray diffraction techniques. The chromium or tantalum films did not react with SiO 2 within the resolution of RBS up to the anneal at 1000°C. For the bilayer structures of SiO 2/Zr/V, SiO 2/Zr/Cr and SiO 2/Ta/Cr, the surface vanadium and chromium films were not involved in the reactions and the zirconium or tantalum films next to the SiO 2 substrates reacted with SiO 2 in the same way as in the SiO 2/Zr and SiO 2/Ta structures. In contrast, both metal films in the SiO 2/V/Zr, SiO 2/Cr/Zr and SiO 2/Cr/Ta structures reacted with SiO 2. A layer of vanadium- or chromium-rich silicides formed next to the SiO 2 substrates and a layer of zirconium or tantalum oxides appeared at the surface. The detailed final phase configurations depended on the original thickness ratio of the two metal films. The occurrence of all the reactions depended on the presence of an oxygen sink.