Elemental analysis of residual deposits in an ion implanter using IBA techniques

Fluorinated species are now widely used as source gases in advanced ion implantation systems because of their controllability and relative ease of operation. The extreme reactivity of fluorine can have a deleterious effect on the source and extraction region, leading to the formation of deposits, which in turn can either directly or indirectly compromise the performance of the source. Little is known, however, about the composition of these deposits and the mechanisms by which they are formed. It is for this reason that this study was undertaken. Similar effects are not observed for hydrogenated species such as arsine and phosphine. In this work, BF₃ was used as the source gas. The behaviour of the source was monitored, during 25 hours of operation. The deposits resulting from extracting an ion beam were studied using a range of ion beam analysis techniques in conjunction with Scanning Electron Microscopy. It was found that the deposits have a matrix of carbon and the two sides of the deposits show different elemental profiles (W, As, Fe, In, Sb, As), reflecting both the history of the ion implanter and the way in which the deposits were formed.