Imaging, spectroscopy and spectroscopic imaging with an energy filtered field emission TEM

Energy filtered microscopy using a post column filter has been applied in a variety of materials characterisation problems to demonstrate its use with a field emission transmission electron microscope. We have shown that the technique, when combined with sample preparation methods such as the focuss ed ion beam technique, enables the imaging of large fields of view for gene ral analysis and also high resolution mapping so that interfaces and grain boundaries can be studied. The general microstructure of semiconductor devi ces is initially investigated with elemental mapping and energy loss fine s tructure analysis. From the B K edge detected in an interlevel dielectric g lass layer of a device, the trigonal coordination of B (present at 2-4 wt.% ) was deduced. The chemistry of 14 nm wide oxynitride composite dielectric layers (composed of a silicon oxide-silicon nitride-silicon oxide or O-N-O sandwich, each layer only a few nm in thickness) in a dynamic random access memory (DRAM) was also studied with elemental maps of oxygen and nitrogen. The intensity profiles and images of these two elements showed two very we ll resolved oxygen layers and a central N layer. Changes in the energy loss fine structure at the Si L2-3 edge in elemental Si, Si nitride and Si oxid e were also used to map different areas of a DRAM transistor and spectrosco pic images were thus obtained showing features arising from the change in c hemical state of Si. Finally the expected resolution of energy filtered mic roscopy is discussed for various imaging conditions and used to analyse Fe segregation observed at grain boundaries and triple junctions. (C) 1999 Els evier Science Ltd. All rights reserved.