Design of Volatile Mixed-Ligand Tantalum(V) Compounds as Precursors to Ta 2 O 5 Films

Synthesis and structural characterization of six monomeric, heteroleptic tantalum(V) complexes of the general formula Ta((OPr)-Pr-i)(4)(ArTFP), where Ar = pyridine (1), 4,5- dimethyloxazole (2), 4,5-dimethylthiazole (3), benzimidazole (4), benzoxazole (5), benzthiazole (6), and TFP = trifluoropropenol, are described. Introduction of a donor-functionalized beta-heteroarylalkenolate in the coordination sphere of Ta in the dimeric Ta-2((OPr)-Pr-i)(10) increases significantly the stability and volatility of these precursors, simplifying the depositions of Ta2O5. The molecular structures of 16 exhibited a distorted octahedral coordination around the tantalum center by four isopropoxide groups and one beta-heteroarylalkenolate. Thermal decomposition studies (TG/DTA) and analysis of byproducts by NMR spectroscopy confirmed the decomposition mechanism and gas-phase stability of the heteroleptic compounds necessary for Ta2O5 depositions. Chemical vapor deposition studies with 1 and 2 demonstrated their suitability as efficient precursors for the growth of Ta2O5 thin films, whose properties were compared with Ta2O5 thin films obtained from homoleptic alkoxides.