Abstract: A process is disclosed for pretreating aluminum-bearing surfaces in a vacuum deposition chamber after a previous step of cleaning the chamber, and prior to depositing tungsten silicide on substrates in the chamber, which first comprises treating the aluminum-bearing surfaces with a mixture of silane and a tungsten-bearing gas, such as WF.sub.6, to form a first deposition of a silane-based tungsten silicide on the aluminum-bearing surfaces. In a preferred embodiment, the process further comprises subsequently treating the already coated aluminum-bearing surfaces of the chamber in a second step with a mixture of a tungsten-bearing gas, such as WF.sub.6, and a chlorine-substituted silane such as dichlorosilane (SiH.sub.2 Cl.sub.2), monochlorosilane (SiH.sub.3 Cl), or trichlorosilane (SiHCl.sub.3) to form a chlorine-substituted silane-based tungsten silicide deposition over the previous deposited silane-based tungsten silicide.