Ultra deep trench doping in silicon by grazing incident boron implantation

The realization of three dimensional (3D) device structures remains a great challenge in microelectronics. Among the technological breakthroughs for such devices, the control of dopant implantation along silicon trench sidewalls is a major issue. Even though ion implantation (II) technology is widely used for planar devices, only few investigations have been done to develop its capability for the doping of 3D structure. In this work, we propose to evaluate II for large scale silicon trench doping. Ultra deep trenches with high aspect ratio were etched on Si wafers. Trenches were then implanted at grazing angle with an industrial implanter. Nevertheless, standard measurement equipments cannot provide accurate results to measure the doping profile along trench sidewall. To overcome the problem and control the trench doping, we developed a simple method based on TRIM calculation and experimental measurements that allow to determine the initial implanted fluence on trench sidewalls.