Low-Noise Detection System for the Counted Implantation of Single Ions in Silicon

A unique detection system has been developed which allows for the counted implantation of individual low-energy heavy ions into silicon. This system can ensure the placement of individual ions at precise locations within a wafer using an EBL-machined resist mask, and utilizes the generation of ionization within the silicon substrate to allow for the reliable detection of implants down to 14 keV. Due to the necessity for low-noise operation, it is important that both the capacitance of the detectors and their leakage current be reduced as much as possible. To this end, we have now created a detector architecture with a measured capacitance of 0.6 pF and sub-pA leakage current at liquid nitrogen temperature, which has allowed us to achieve a resolution of 410 eV (44.2 electrons RMS) when coupled to low-noise signal-processing electronics and operated at 90 K.