Radial uniformity of an external-coil ionized physical vapor deposition source

A production-scale ionized physical vapor deposition (I-PVD) source has been developed to investigate the directional metalization of 200 mm diameter wafers by sputtering. The ionization of sputtered metal is accomplished by a 45 cm diameter inductively coupled plasma (ICP). Unlike previously reported I-PVD sources? however, the coil of the ICP is external to the plasma chamber. A plasma-immersed Faraday shield is used to prevent sputtered metal from depositing on the walls of the plasma chamber and electrically shorting the ICP source. Interaction between the Faraday shield and the ICP is found to result in an rf-induced negative self-bias of no more than 15 V de on the shield. Since the simple internal geometry of this I-PVD system is not complicated by an immersed inductor, factors that control radial uniformity are readily investigated. The spatially resolved flux of aluminum neutrals and ions on 200 mm wafers is measured and compared with two diffusion models. Both the aluminum neutral and ion density are centrally peaked with a profile that is predicted by simple diffusion in a cylindrical chamber. The fraction of ionized aluminum flux is quite uniform, however, since the aluminum neutral density and ion density radially decrease at similar rates. (C) 1998 American Vacuum Society. [S0734-211X(98)00502-2].