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. I on implantation has long been used extensively in junction formation a nd will be a vitally important process for the fabrication of ultrasha llow junctions. However, implant channeling needs to be understood and minimized. This article presents the results of a detailed experiment al 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 wer e measured by secondary ion mass spectroscopy using low energy primary ions. The behavior of the impurity profiles has been analyzed in term s of their dependence on tilt angle (0 degrees-10 degrees) and rotatio n angle (0 degrees-360 degrees). The profiles exhibit a strong depende nce on tilt angle while the dependence on rotation angle is less prono unced for boron and arsenic. The rotation angle dependence of the prof iles is almost negligible for BF2 at these very low implant energies. It is found that the dependence of the impurity doping profiles on rot ation angle decreases with decreasing implant energy. This information on ultrashallow implanted profiles is important for the development o f low energy implantation models for process simulators, for the devel opment of scaled devices with ultrashallow junctions, and for a better understanding of process control requirements in manufacturing. (C) 1 996 American Vacuum Society.