Ion beam induced charge and numerical modeling study of novel detector devices for single ion implantation

In the near future devices which are fabricated from shallow arrays of few and single atoms will exploit quantum mechanical rules to perform useful functions including quantum computation. Fabrication of these devices presents formidable technological challenges. We have developed a single ion implantation system that is capable of verifiable fabrication of single donor devices using 14 keV 31P ions implanted into ultra-pure, high resistivity silicon substrates based on the technique of Ion Beam Induced Charge (IBIC). A detection system with integrated detector electrodes registers the charge transient from a single ion impact which is used to signal the implantation of an ion into the substrate. We describe here the use of IBIC with MeV ions to study the charge collection efficiency of the detector electrodes. By using three dimensional numerical technology computer-aided design (TCAD) models for the decrease in the IBIC signal as a function of distance from the detector electrode, we can obtain an accurate measurement of the resistivity of the silicon substrate, allowing confirmation of the values specified by the supplier, and providing us with confidence in the numerical models used by TCAD for simulation. This technique has advantages over resistivity measurements by four-point probes because it is spatially resolved, probes through the intact oxide, and can be done without making contact to the device in the area of the probe.