Proposals for exact-point transmission-electron microscopy using focused ion beam specimen-preparation technique

Abstract

A focused ion beam (FIB) has been actively applied for preparation of about 0.1-μm-thick specimens for transmission electron microscopes (TEMs). For device failure analyses, however, it is mostly difficult to prepare the exact-point TEM specimens. The reason is that the failures are mostly beneath the surface and their exact locations are unknown. Then, even step-by-step FIB cross sectioning may sputter away the failures in the TEM specimen preparation. In the present study, we review two proposals for exact-point TEM microscopy using FIB specimen-preparation technique: (1) high-voltage scanning electron microscopes (HV-SEMs) imaging in TEM and (2) energy filtering TEM (EF-TEM) imaging. The HV-SEM imaging provides information on not only the sample surface but also the inner structure up to about 1 μm deep. The EF-TEM imaging is applicable even for 0.5-μm-thick specimens at 100 kV in the accelerating voltage, in contrast with about 0.1-μm-thick specimens for conventional TEM imaging. Preliminary experiments have supported that either proposal presumably improves the yield of the exact-point TEM inspection.