Strontium ruthenium oxide deposition in supercritical carbon dioxide using a closed reactor system

A SrRuO₃ deposition process using supercritical fluid deposition (SCFD) was designed for fabricating electrodes in ferroelectric random access memory (FeRAM). To make stoichiometric SrRuO₃ film (Sr:Ru = 1:1), deposition rates of component materials, SrO and RuO₂, must be balanced, and thus, we investigated the deposition kinetics of the component materials. The deposition rate of SrO was found to be less than that of RuO₂ in all cases, and SrO particle generation during deposition was problematic. Both of these issues could be overcome by controlling the temperature and O₂ concentration. For SrRuO₃ deposition, the Sr-/Ru- precursor concentration ratio was the dominant factor to control the composition of the film. Stoichiometric SrRuO₃ film can be formed by increasing the Sr-/Ru- precursor sconcentration ratio to 6. Our deposited film satisfied three major requirements for a FeRAM electrode: perovskite crystal structure, low resistivity, and conformal deposition onto the trenches (aspect ratio of 5).