Key technologies of a focused ion beam system for single ion implantation

A focused ion beam (FIB) system was remodeled specially to realize single ion implantation (SII) by which we intended to implant an accurate number of ions one by one into ultrafine semiconductor regions. In the SII, single ions are extracted by chopping the ion beam, and one-by-one extraction of ions have become possible by installing an ultrahigh speed amplifier for chopping. In order to achieve accurate detection of each single ion incidence in the SII, detection of SEs emitted upon ion incidence with a high sensitivity and a high signal to noise (S/N) ratio is essential. Signals from the SE detector which synchronize to an instance of chopping are selectively counted to achieve high S/N ratio. Contaminant particles originating from neutralization and scattering of the ion beam are eliminated by sliding the ion source off the beam axis and cutting off the ion beam at the entrance of the FIB's mass separator.