ALUMINUM AND ALUMINA COATINGS ON COPPER BY CHEMICAL VAPOR-DEPOSITION IN FLUIDIZED-BED REACTORS

High temperature Knudsen cell mass spectrometry was used to study the reactions of Al(c) with HCl(g) and with HCl(g) + H-2(g) over the range 127-627-degrees-C (400-900 K) to gain information pertinent to the chemical modeling of aluminum coating on copper by chemical vapor deposition in a fluidized bed reactor (CVD-FBR). In the Al-H-Cl system the measured pressures of AlC13 and AlCl were in remarkably good agreement with the values predicted by thermochemical calculations when the system is at equilibrium in the temperature range 377-623-degrees-C (650-900 K). Neither AlHxCl3-x (x = 1-3) nor AlCl2 Species were observed within the entire investigated temperature range. An upper limit of about -218 +/- 20 kJ mol-1 was estimated for the enthalpy of formation of AlCl2 required to bring the observed and predicted pressures into agreement. The revised database was used to model aluminum coating on copper from a halide system by CVD-FBR. All the experimental results and thermochemical calculations show that AlCl gas is an important reactive precursor in the aluminium-coating process. Using the most favorable conditions determined from these experiments and the thermodynamic calculations, a thin aluminum coating was deposited on a copper wire immersed for 30 min in a fluidized bed of aluminium particles at 487-degrees-C (760 K), using argon containing 0.12% HCl and 7% H-2 as the fluidizing gas. This coating significantly improves the corrosion resistance of copper exposed to air.