Controlling precursor stability and evaporation through molecular design. Pseudo single source precursor approach to MOCVD SrTiO3 thin films
Résumé
Strontium titanate SrTiO3 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 Sr2Ti2(thd)4(OiPr)8, has limited volatility. Bimetallic primary alkyl chain complexes,
Sr4Ti2O(thd)4(OR)10(ROH)2, R = Et, nPr, are stable and volatile, but possess a wrong composition.
Highly volatile precursor Sr2Ti2(thd)4(OiBu)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 SrTiO3 thin film
deposition by DLI-MOCVD technique in a sufficiently broad established temperature range. Using optimized
experimental conditions, 100nm thick strontium titanate films with high permittivity have been
successfully obtained on (1 0 0) Si.