Synthesis and characterization of Hf–Al heterometallic aminoalkoxides as single-source MOCVD precursors for hafnium aluminate films

• Published in: Polyhedron 2006, Vol.25 (2), p.293-299
• Main Authors: Hubert-Pfalzgraf, Liliane G., Abrutis, Adulfas, Pasko, Sergej, Touati, Nadia, Luneau, Dominique
• Format: Article
• Language: English
• Subjects: Aluminate; Catalysis; Chemical Sciences; Hafnium; Heterometallic alkoxide; High κ dielectrics; MOCVD; Structure
• ISSN: 0277-5387; 0277-5387
• DOI: 10.1016/j.poly.2005.06.037

The first Hf–Al aminoalkoxide HfAl 2(μ-OPr i ) 2(μ,η 2-OC 2H 4NMe 2) 2(OPr i ) 6 has been structurally characterized. It is an attractive single-source precursor for liquid-injection MOCVD of (HfO 2) x (Al 2O 3) 1 − x films. These were characterized by XRD, AFM and XPS. Alcohol exchange reactions applied to HfAl 2(OPr i ) 10 ( 1) afforded heterometallic Hf–Al aminoalkoxides namely HfAl 2(OPr i ) 8(dmae) 2 (dmae = N, N-dimethylaminoethoxide) ( 2) and HfAl 2(OPr i ) 8(dmap) 2 (dmap = dimethylaminopropoxide) ( 3). They were characterized by elemental analysis, FT-IR, 1H NMR, mass spectrometry and TGA. The molecular structure of 2, as established by single-crystal X-ray diffraction, HfAl 2(μ-OPr i ) 2(μ,η 2-OC 2H 4NMe 2) 2(OPr i ) 6, is based on an open-shell trinuclear unit with a central 6-coordinate Hf atom and 5-coordinate Al centres. Compound 2 was tested as a single-source precursor for the deposition of hafnium aluminate films by liquid-injection MOCVD. The films growth rate, composition and morphology were studied in relation with the deposition temperature. The as-deposited at 500–800 °C films (both on sapphire and silicon) were amorphous; partial crystallization occurred after 1 h annealing at 900 °C. The bulk of the films was Al-rich (Al/Hf = 1.2–1.6) and contained small amounts of carbon (2–4%) and nitrogen (4–5%).