Optimisation and characterisation of a TCP type RF broad beam ion source

Abstract

A very compact type of broad beam ion source based on transformer coupled plasma excitation (TCP) is described. Our ion source consists of a cylindrical RF coil surrounding the discharge vessel and a very compact, patented matching unit from special ceramics capacitors attached directly to the discharge arrangement. However, the TCP excitation as well as the sophisticated layout of the matching unit require an optimum source arrangement due to the beam parameters, the source lifetime and the performance of the RF elements. For that reason, a global discharge model was applied together with an RF replacement circuit diagram to calculate for the optimum source layout. An advanced plasma and beam diagnostics is used for controlling the source performance due to beam composition, beam profile and ion energy distribution. In this way, our RF source is adapted to different beam requirements in inert and reactive beam processes for etching, modification and sputter deposition.