A study of the influence of electron beam on electrical characteristics of LOCOS device

Abstract

Electrical characteristic changes in scaled MOSFET devices have been widely reported due to electron beam (EB) irradiation. For local oxidation of silicon (LOCOS) devices, the effects of EB-induced damage when performing measurements using an SEM based nanoproer, however, have rarely been reported. EB penetration into the dielectrics, resulting in the modification of the physical properties of the dielectric layer, could be a concern, not only for scaled devices, but also for LOCOS devices. This study reveals that the effect of EB on LOCOS devices can be measured using a scanning electron microscope (SEM) based nanoprober with inducing electrical characteristic changes. These changes are accounted for by the hole trapping at the birdsbeak, which has a significant effect on both the junction electrical characteristics and punchthrough characteristics in LOCOS isolation structures when an SEM is employed for probe guidance. Further, some preliminary experimental results, not included in this paper, show that lowering the EB acceleration voltage is found to not be able to significantly eliminate the effects of EB-induced damage during device inspections in failure analysis procedures. More advanced studies are currently under investigation.