CHEMICAL VAPOR-DEPOSITION OF COPPER ON SI(111) AND SIO2 SUBSTRATES

Chemical vapour deposition of Cu and CU3Si using solid CuCl as the copper source has been investigated. It was found that the evaporation of CuCl from the solid Powder was a critical step in the process. The evaporation rate. and hence the partial pressure of CuCl, was dependent mainly on two factors: (i) deviation from equilibrium evaporation and (ii) formation of oxygen-containing compounds on the powder surface. The potential use of CuCl as a copper source in CVD was demonstrated for three substrate conditions: SiO2, Si(111) and patterned Si(111) /SiO2 wafers. For SiO2, thin Cu films (resistivity 3.3-mu-OMEGA-cm) were deposited at 500-degrees-C from a CuCl/H-2/Ar gas mixture. For Si(111) substrates, CU3Si was invariably formed in the temperature range 350 to 500-degrees-C using either a CuCl/Ar or a CuCl/H-2 /Ar gas mixture. The CU3Si phase showed a strong epitaxial relationship with the Si(111) substrates, especially at higher deposition temperatures. At lower deposition temperatures or with H-2 present in the vapour, elemental Cu in the form of particles was formed on top of the Cu3Si layer. The selectivity of the CuCl process was demonstrated on a patterned Si(111)/SiO2 substrate. Finally, rather high Cl concentrations were detected on the surface of the films, indicating that the desorption of chlorine-containing molecules may play an important role in the deposition process.