Production of high-current metal ion beams

Abstract

The increasing usage of ion implantation to modify the chemical and surface sensitive mechanical properties of materials typically requires fluences of 10 17 ions/cm 2. In order to implant test hardware (e.g., ball bearings) to such high influences in a reasonable period of time it is necessary to employ ion beam currents with intensities of a hundred-microampere or more. This paper will describe the modifications made in the ion source of the NRL Extrion/Varian 200-20A2F ion implanter to produce high current metal ion beams utilizing an internal chlorination technique. Several charge material source geometries and carrier gas combinations have been tried and compared. Beam currents of 100 μA or more intensity have been routinely obtained for most metal species attempted, with 500–1000 μA intensities obtained for some commonly run species (e.g., 52Cr + and 48Ti +). This paper will present (1) a compilation of ion species and intensities obtained, (2) typical ion source operating parameters and lifetimes, and (3) evidence of ion source “poisoning effects”.