KEY TECHNOLOGIES OF A FOCUSED ION-BEAM SYSTEM FOR SINGLE-ION IMPLANTATION

A focused ion beam (FIB) system was remodeled specially to realize sin gle ion implantation (SII) by which we intended to implant an accurate number of ions one by one into ultrafine semiconductor regions. In th e 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 t o an instance of chopping are selectively counted to achieve high S/N ratio. Contaminant. particles originating from neutralization and scat tering of the ion beam are eliminated by sliding the ion source off th e beam axis and cutting off the ion beam at the entrance of the FIB's mass separator. (C) 1998 American Vacuum Society.