Status of Low-Dose Implantation for VLSI

This article describes the current status of implantation in silicon for ion doses up to but not including the onset of the amorphous state. Physical phenomena, applications to VLSI, and equipment issues are discussed and linked from the viewpoint of vertically integrated technologies (see Figure 1). In such a view, engineering applications are the customer of research on phenomena, and the equipment industry is the customer of both the research and applications community. The article highlights areas in phenomena, applications, and equipment requiring particular attention.Studies in physical phenomena associated with ion implantation are motivated by the need for very shallow junctions. The shallowness is limited by ion channeling effects in crystalline silicon (which directly affect the as-implanted impurity profile) and by diffusion (which occurs during implant activation and annealing of damage). The inventory of ion-damage induced defects includes point defects, cluster defects, and dislocations arising from the combination of damage and annealing. A recent survey by Schreutelkamp et al. of low-dose implantation describes advances in characterization of channeling effects, and the formation of dislocation damage which, in turn, impacts thermally processed profiles. These effects need to be understood in terms of modern MOS (metal-oxide-semiconductor) processes.