Synthesis of Cu–Ti thin film multilayers on silicon substrates

Abstract

Metal-oxide-based sensors (MOS) can be used for several technological applications in microelectronics, due to their low cost and sensitive capabilities to different chemical species. On the perspective to develop CuO–TiO₂ MOS, our goal was to obtain a homogeneous intermixing of Cu and Ti in the bulk structure of the detectors, exploring the most promising combination between such elements and avoiding the presence of Cu–Ti–O compounds. To do that, several Cu and Ti thin layers were alternatively deposited by Ar⁺ sputtering on silicon wafers and, subsequently, oxidized by thermal annealing. The obtained samples were characterized in terms of %at. Cu–Ti ratios (by RBS and SIMS analyses) and morphology (by AFM and SEM investigations), showing the abundance ratios of such elements in the whole structure. In particular, SIMS maps allowed to study the spatial distribution and thickness of each phase of the Cu–Ti multilayers and further to observe the Cu diffusion and the mixing with Ti, as well as phase separation of CuO and TiO₂ in the samples. This unwanted effect represents an open issue that has to be investigated, in order to improve the MOS fabrication.