Controlling precursor stability and evaporation through molecular design. Pseudo single source precursor approach to MOCVD SrTiO3 thin films

Abstract Strontium titanate SrTiO 3 thin films have attracted interest as a possible gate dielectric material. Preparation of its high quality coatings is hindered by difference in volatility of the homometallic precursors – strontium beta-diketonates and titanium alkoxides. The only earlier known single-source precursor, a sec-alkoxide derivative Sr 2 Ti 2 (thd) 4 (OiPr) 8 , has limited volatility. Bimetallic primary alkyl chain complexes, Sr 4 Ti 2 O(thd) 4 (OR) 10 (ROH) 2 , R = Et, n Pr, are stable and volatile, but possess a wrong composition. Highly volatile precursor Sr 2 Ti 2 (thd) 4 (O i Bu) 8 has been prepared using an iso-alkoxide, combining proper ligand size with the sterical requirements, and characterized by multivariate evaporation analysis. Its evaporation is associated with complete decomposition into homometallic species, which, however, are evaporated in a single step. This permits to successfully use this novel precursor for SrTiO 3 thin film deposition by DLI-MOCVD technique in a sufficiently broad established temperature range. Using optimized experimental conditions, 100 nm thick strontium titanate films with high permittivity have been successfully obtained on (1 0 0) Si.