Laser chemical vapour deposition of thin aluminium coatings

Laser chemical vapour deposition has recently become an attractive area of research. A maskless configuration of aluminium has been grown utilizing visible light from a copper laser which induces pyrolytical decomposition of trimethylaluminium (TMA). The process was carried out in vacuum or argon and hydrogen atmosphere at partial TMA pressures of 0.05, 0.1 and 0.5 kPa. A silicon monocrystalline wafer was used as a substrate. The layer was investigated by scanning electron microscopy, Auger electron spectroscopy, Talystep and electrical resistance measurements. The crystalline structure of the coating shows well-defined grains. This morphology was observed for the first time by using a pulsed visible laser. The Auger electron spectra indicate the presence of bonded oxygen and carbon incorporated into the aluminium. These elements cannot be totally avoided but their concentration can be reduced at the established optimum conditions to obtain a low specific resistance for the layer.