Analysis of ultrashallow doping profiles obtained by low energy ion implantation

Deep submicron (<0.35 mm) devices in future generations of integrated circuit technology will require ultrashallow source/drain junctions. Ion implantation has long been used extensively in junction formation and will be a vitally important process for the fabrication of ultrashallow junctions. However, implant channeling needs to be understood and minimized. This article presents the results of a detailed experimental analysis of the dependence of low energy boron, BF2, and arsenic as-implanted profiles on the implant tilt angle and rotation angle. The dopant impurities were implanted at very low energies of 5 and 10 keV into crystalline silicon directly. The resultant impurity profiles were measured by secondary ion mass spectroscopy using low energy primary ions. The behavior of the impurity profiles has been analyzed in terms of their dependence on tilt angle (0 degrees-10 degrees) and rotation angle (0 degrees-360 degrees). The profiles exhibit a strong dependence on tilt angle while the dependence on rotation angle is less pronounced for boron and arsenic. The rotation angle dependence of the profiles is almost negligible for BF2 at these very low implant energies. It is found that the dependence of the impurity doping profiles on rotation angle decreases with decreasing implant energy. This information on ultrashallow implanted profiles is important for the development of low energy implantation models for process simulators, for the development of scaled devices with ultrashallow junctions, and for a better understanding of process control requirements in manufacturing. (C) 1996 American Vacuum Society.