Laser-induced deposition of aluminium on gallium arsenide and silicon nitride from trimethylamine alane

Abstract

Aluminium is a highly conductive metal, which is extensively used in the microelectronics industry for semiconductor and interconnect technology. Laser-induced chemical vapour deposition is a very attractive technique for the direct writing of micron-sized aluminium features of high quality with high deposition rates. The use of a solid precursor, an adduct called trimethylamine alane (TMAAH) having interesting physical properties, is reported as a good source for laser-induced deposition of high-purity aluminium films on GaAs- and Si 3N 4-coated GaAs substrates as well as on Al predeposited lines. Thus 30 μm wide, 0.5 μm thick lines, exempt from C, have been deposited using a focused CW visible laser (λ=514 nm), at scanning speeds in the range 2–30μm/s. The laser-induced temperatures, calculated at the centre of the spot, are lower than 300°C. Resistivity measurements performed on Al lines deposited on Si 3N 4-coated GaAs substrates give typically 10 μΩ·cm. The very different deposition rates on GaAs or Si 3N 4-coated GaAs substrates and on Al predeposited lines, which are observed for the TMAAH complex, are consistent with surface physical chemistry studies, which show that both the surface nature and the chemisorbed species play a leading role in the thermal decomposition of the precursor. Thus, it is demonstrated that a laser-writing technique, based on a surface-controlled pyrolytic process of a well defined precursor can be used for in situ reparation or customization of integrated circuits.