FIB-based Single Ion Implantation with >99% Detection Confidence – Towards Near-Surface Donor Qubit Architectures in Silicon

Silicon chips incorporating large-scale donor-qubit arrays show great potential for spin-based quantum computation. Single ion implantation into an active detection substrate is a promising fabrication technique when combined with a method to accurately localise the ion implant site. Here, we introduce a new approach to enhance the device development process and enable the construction of near-surface donor-qubit arrays with high yield. Using a modified focussed ion beam system equipped with an electron beam ion source and ultra-low noise on-chip ion detection electronics (~70 eV r.m.s), we demonstrate a powerful method to evaluate the device’s spatial response to single ion impacts. A sub-500 nm beam spot together with a range of species and acceleration energies down to a few keV allow detailed maps of the device's underlying electrical landscape to be acquired. These aid in understanding the role interface and bulk defects play in the ion detection response, and provide further insight to the physics of ion-solid interactions. Furthermore, we show the ability to perform 2000 counted 24 keV Ar²⁺ implants into a 25μm² area with 99.99% detection fidelity, demonstrating an attractive framework for future rapid mask-free engineering of scalable shallow donor-qubit nanoarrays.