Dopant channeling as a function of implant angle for low energy applications

The formation of ultra-shallow junctions requires that channeling of the dopant beam by the silicon lattice be avoided to minimize junction depth. This can be accomplished by techniques such as pre-amorphization of the silicon substrate, thereby adding an extra process step in the device fabrication process. A simpler approach is to extend the use of the implant angle of the silicon lattice relative to the beam. At high energies, the use of a 7 degree implant angle is typical to avoid channeling. As the implant energy is reduced, the acceptance angle for channeling grows, thus larger implant angles may be required. Unfortunately, the capability of most high current machines is limited to implant angles of about 10 degrees or less. In this paper, the effect of tilt angle on channeling for low energies is investigated on the Varian VIISta 80 serial high current implanter, which allows the use of implant angles up to 60 degrees