The boundaries of ion implantation

The present trend in experimental ion implantation to the use of a wider range of dopants at higher fluences is parallelled by increasing industrial demands to exploit the inherent uniformity and reproducibility of the process. In any practical application, however, the quality and the spatial homogeneity of the doping are ultimately limited by a variety of basic and instrumental factors. The nature of some of these constraints and the boundaries which they set on the scope of ion implantation are described. In particular, certain aspects of profile control, of electrostatic scanning and of ion-beam sputtering and charge-exchange which may be significant in particular doping situations, but which are not widely recognised, are examined. An account is also given of the use of powder implantation as a means of circumventing some surface-area and bulk-doping limitations. (author)