Creating He- using H- ion source beam on He0
Metals, and particularly alkali metals, are contaminants in silicon wafers used to make computer chips and power electronics devices [1,2,3]. The movement of contaminating ions in the SiO2 under the influence of an applied voltage across the oxide causes the electrical characteristics of the transistor, such as the threshold voltage, to change . This is particularly problematic for the class of ion implanters used in the production of silicon-based computer chips and power electronics devices requiring negative ion beams for the implant process . To date these negative ion beams have been created by way of charge exchange by passing energetic positive ion beams through metallic vapours from which electrons are picked up, thus creating a negative ion beam. This process inherently uses neutral metallic vapours in the implanter system, and therefore presents a continual ongoing risk of exposing the silicon wafers to a metallic contaminant.