HAFNIUM ALKYLS - CYCLOPENTADIENYLS

Dimethylhafnium bis(cyclopentadienyl) (HfMe2(Cp)2, Dimethylhafnium bis(methylcyclopentadienyl) HfMe2(MeCp)2, Dimethylhafnium bis(ethylcyclopentadienyl) (HfMe2(EtCp)2

TGA "open cup" HfMe2(RCp)2, R = H, Me, Et),(HARALD0, HARALD1,HARALD2)

Among “HARALD” precursors (HfMe2(RCp)2, R = H, Me, Et),(HARALD .0, HARALD .1, HARALD .2, respectively), developed by AirLiquide, the most volatile are unsubstituted (R = H) and methyl-substituted (R = Me) ones. No significant resudue in “open cup” TGA was observed, meaning the decomposition below 250°C is negligible. (Fig.) On the contrary, HARALD2 (R = Et) is less volatile and leaves about 12% residue in TGA.

Comparison of vapour pressure of HARALD precursors with hafnium dialkylamides (TEMAH, TDEAH)

HARALD.2 is the only liquid (at R.T.) precursor and displays very promising thermal properties at reduced pressure (1% residue at 60mbar, full evaporation below 200°C). Thermal decomposition occurs between 200°C and 280°C. 

The comparison of vapour pressure of HARALD precursors with some dialkylamides is presented in Fig.

Dimethylhafnium propane-2,2-dicyclopentadienyl (HfMe2(Cp2CMe2)2

Ansa-metallocene precursor dimethylhafnium propane-2,2-dicyclopentadienyl [(Cp2CMe2)HfMe2] has been applied as precursor for the deposition of HfO2 layers by liquid injection MOCVD (with O2 as co-precursor) and ALD (using O3 as oxidizer). The crystal structures of [(Cp2CMe2)HfMe2] has been determined, it was shown to be mononuclear and isostructural to zirconium analogue [(Cp2CMe2)ZrMe2] and contains a chelating [Cp2CMe2] ligand leading to a pseudo-four-coordinate distorted tetrahedral geometry around the central Hf atom, in agreement with structures from Density Functional Theory (DFT). The HfO2 layers were grown either by MOCVD at 400–650 °C, or by ALD in the 175–350 °C temperature range. HfO2 films deposited by MOCVD were amorphous according to XRD; the films grown by MOCVD contained more C impurity (2.4–17.0 at.%) than the films grown by ALD (1.8–2.8 at.% carbon). The prepared HfO2 films had low current leakage densities <6 × 10−7 A cm−2 at ±2 MV cm−1, evaluated using [Al/MO2/n-Si] metal oxide semiconductor capacitor (MOSC) structures. [[i]]

[i]  Kate Black, H. C. Aspinall, A.C. Jones, Katarzyna Przybylak, John Bacsa, P. R. Chalker, S.Taylor, Ce Zhou Zhao, S.D. Elliott, Aleksandra Zydord, Peter N. Heyse, J. Mater. Chem., 2008,18, 4561-4571, DOI: 10.1039/B807205A “Deposition of ZrO2 and HfO2 thin films by liquid injection MOCVD and ALD using ansa-metallocene zirconium and hafnium precursors”,

http://pubs.rsc.org/en/content/articlelanding/2008/jm/b807205a#!divAbstract

Share this page