Efficient medium current He+ beam extraction sustained by auxiliary plasma formation in the ion source by solid material

Helium ions incorporated into material such as quartz or LiNbO₃ (Lithium Niobate) produce bulk modifications suitable for optical waveguide, also, implanted into silicon it starts-up the long void production which enables the separation process of material for selective layer removal like by hydrogen implantation into Si. But, the He⁺ beam is difficult to obtain because of the high ionization potential of this noble gas. In this paper, we report an efficient technique to extract medium current He⁺ beam, using in the ion source as a starting plasma from solid material and a He gas nozzle. The experiments carried out in an Eaten Ion Implanter Ga4204 with a Freeman source achieved a very stable He⁺ beam of 0.8 mA. The first step is to load solid P (Phosphorous) in the induction heater together with a He flow in the source. Keeping the heater at 370°C threshold temperature the auxiliary plasma which was obtained by the solid material, produces ionized helium in such a way that the beam is sustained for a long time with 0.8 mA. Applying the technique with the auxiliary plasma the beam is easily controlled. Excited ions and the increase of the electrons in the plasma produce collisions with the helium atoms causing their ionization. A drawback observed using this procedure is the relative low filament lifetime. Silicon wafers were implanted with 170 keV, 0.8 mA He⁺ beam with relatively high doses (10¹⁷ cm^-2) and a simple qualitative cheek of incorporated helium into silicon was made by FTIR analysis