HfxZr1-xO2 Thin Films from Chemical Vapor Deposition of Fluorinated β-Ketoenamine Precursors

Abstract

New Zr(IV) and Hf(IV) complexes were synthesized and applied as molecular precursors for chemical vapor deposition (CVD) of Zirconium-, Hafnium-, and mixed Hafnium-Zirconium-Oxide (HZO) coatings. Reaction of tetrakis(diethylamido)metal(IV) complexes (M = Zr, Hf) with the fluorinated β-ketoenamine ligand (Z)-4-(tert-butylamino)-1,1,1-trifluorobut-3-en-2-one (H-TFB-tBuA) and tert-butyl alcohol produced new heteroleptic [M(TFB-tBuA)₂(OtBu)₂] zirconium (Zr-1, M = Zr) and hafnium (Hf-1, M = Hf) complexes. Both compounds possess excellent thermal stability up to 250°C and exhibit volatility suitable for chemical vapor deposition of ZrO₂ and HfO₂ thin films in a low-pressure (10^-2 mbar) chemical vapor deposition reactor. The vapor pressure and thermal stabilities of both Zr-1 and Hf-1 are compatible for the co-deposition of individual metal oxides, enabling direct synthesis of phase-pure HZO films with a tunable Zr:Hf ratio. The co-evaporation without preferential decomposition of either precursor was attributed to the matched decomposition profiles of Zr-1 and Hf-1, enabling the single-step deposition of mixed-metal HZO films.