Development of a Focused Ion Beam Tool for Single Ion Implantation

Deterministic implantation of single bismuth ions in silicon is demonstrated using a focused ion beam (FIB) tool named the Single Ion Multi-species Positioning at Low Energy (SIMPLE) tool, manufactured by Ionoptika Ltd. Atomic scale fabrication is required if we are to realise the existing designs of many semiconductor quantum technologies and single ion implantation is a versatile and capable method of manufacture for such technologies.The difficulty of single ion implantation is knowing that a single ion has been implanted in the target substrate. This has been achieved through the detection of secondary electrons generated upon ion impact. The measure of how likely it is that a single ion implant is detected is the detection efficiency, and the majority of the work in this project was devoted to determining and improving this.The work covers the build and test of a focused ion beam instrument designed to implant single ions, to enable the fabrication of quantum technologies and other single atom device. Throughout, the path to achieving single ion implantation is recorded, covering investigations into the pulse length calibration, metrological investigations into measuring femto-amp currents, and the development of the secondary electron detection system.The results section presents data from implantation of single bismuth and gold ions with different charge states into different material substrates, to determine the detection efficiency for single ion implants and the factors which affect such detection efficiencies.It has been found that for 50 keV implants of Bi++ into silicon we can achieve an 89% detection efficiency, the highest reported detection efficiency for single ion implants into silicon without implanting through a SiO2 film. Detection efficiency values of 100% are reported for Bi++ implants into thick SiO2 layers.This level of precision enables the doping of single impurity ions with a success rate far exceeding that achievable by random (Poissonian) implantation. Targeted implantation of low numbers of ions into a 1 μm width channel of a field effect transistor is experimentally proven. Demonstrating high precision in the positioning of ions, as well as the number of ions implanted