Dimethylaluminum hydride (AlMe2H)3
Dimethylaluminum hydride (AlMe2H)3 is liquid precursor having trimeric molecules at low temperatures and dimeric at ca. 160 °C (dimeric as well in vapor phase); it has vapor pressure 2.0 Torr/25 °C. (AlMe2H)3 has H-Al-H units (3-c 2-e- bonds), having heat of association 15–20 kcal mol/1 per H-bridge.
The pyrolysis of AlMe2H occurs at temperatures between 230 – 280 °C in H2 flow and partial precursor pressure 0.2 x 10-3 Torr.
The decomposition pathway is following : (Me2AlH)3 → Al2Me6 + Al + 3/2 H2
Synthesis
The synthesis of Dialkyl Aluminum Hydrides [R2AlH]2 is usually perfromed by the followng scheme: Al + 3/2 H2 + 3 AlR3 → 3 R2AlH
AlMe2H for metal Al thin films by CVD
Al metal films have been grown in cold-wall reactor. The growth rate of Al films was 500 – 1000 nm/ min, the films had rough surface and resistivity 3 μWcm,, in the layers ~0.05 % carbon incorporation was observed. On Si / SiO2 substrates Al grows selectively at 235 – 245 °C temperature, at lower temperatures, f.e. 200°C, no deposition occurs.
Di-iso-butylaluminum hydride AliBu2H
Di-iso-butylaluminum hydride AlH(iBu)2, orDIBAH, has vapor pressure 0.01 Torr, 40 °C
(lower vapor pressure than TIBA): DIBAH is H-bridged trimer.
The formation of DIBAH can be suppressed by addition of iso-butene to the carrier gas (reversibility: hydro-alumination!).
[Al(CH2CMe)2 H]3 → AlH3 + 3 H2C=CMe2
AlH3 → Al + 3/2 H2
Al(iBu)2H for metal Al thin films by CVD
Al(i-Bu)2H has been aplied as CVD the growth of Al films at 200 °C.
The decomposition pathway is following:
DIBAH → Al and H2, H2C=CMe2, HCMe3, H2C=CHMe, …