Ion implantation in semiconductors—Part I: Range distribution theory and experiments

Ion implantation in semiconductors provides a doping technique with several potential advantages over more conventional doping methods. Among the most important of these are: 1) the ability to introduce into a variety of substrates precise amounts of nearly any impurity element desired; 2) the ability to control doping profiles in three dimensions by modulating the energy, current, and position of the ion beam; and 3) the possibility of avoiding certain undesirable effects that accompany the high-temperature diffusion process. Ion implantation can also be used in conjunction with other fabrication techniques to produce device structures that no one process can produce simply by itself. Current research in the field is directed toward several problems that must be solved before the full impact of ion implantation on semiconductor technology can be soundly predicted. In particular, it is necessary to be able to predict the distribution profiles of the implanted ions accurately, to know which crystalline sites the implanted ions occupy, to know the nature of the damage centers that are introduced by the implantation process, and to determine the extent to which these defects can he removed by appropriate annealing procedures. Theoretical and experimental work pertinent to the problem of predicting impurity distribution profiles in ion-implanted material are reviewed here. A review of current research on the other problems listed will be given in Part II, together with the characteristics of a number of interesting semiconductor devices that have already been fabricated by ion implantation.