RADIAL UNIFORMITY OF AN EXTERNAL-COIL IONIZED PHYSICAL VAPOR-DEPOSITION SOURCE

A production-scale ionized physical vapor deposition (I-PVD) source ha s been developed to investigate the directional metalization of 200 mm diameter wafers by sputtering. The ionization of sputtered metal is a ccomplished by a 45 cm diameter inductively coupled plasma (ICP). Unli ke previously reported I-PVD sources? however, the coil of the ICP is external to the plasma chamber. A plasma-immersed Faraday shield is us ed to prevent sputtered metal from depositing on the walls of the plas ma chamber and electrically shorting the ICP source. Interaction betwe en 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 si mple internal geometry of this I-PVD system is not complicated by an i mmersed inductor, factors that control radial uniformity are readily i nvestigated. 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, sin ce the aluminum neutral density and ion density radially decrease at s imilar rates. (C) 1998 American Vacuum Society. [S0734-211X(98)00502-2 ].