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

• SrRuO3 thin film formation was carried out using kinetics of RuO2 and SrO deposition.
• High RuO2 deposition rate and easy SrO particle formation in the fluid induced Ru rich SrRuO3 film.
• Stoichiometric SrRuO3 was deposited by controlling deposition temperature, O2 partial pressure and Sr to Ru precursor mol ratio.
• Deposited SRO had good step coverage, which was 0.96 on trenches, having aspect ratio of 5.

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).

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