Electron Microscopy, Electrical Activity, Artefacts and the Assessment of Semiconductor Epitaxial Growth

Abstract

AbstractThe characterisation of semiconductor thin films and device structures increasingly requires the use of a variety of complementary electron microscope-based techniques as feature sizes decrease. We illustrate how layer electrical and structural properties can be correlated: firstly averaged over the bulk and then on the individual defect scale, e.g. scanning transmission electron beam induced conductivity can be used to image the recombination activity of orthogonal <110> misfit dislocations within relaxed MBE grown Si/Si1-xGex/Si(001) heterostructures on the sub-micrometre scale. There is also need for improved understanding of sample preparation procedures and imaging conditions such that materials issues relevant to ULSI development can be addressed without hindrance from artefact structures. Hence, we consider how point defects interact under the imaging electron beam and the relative merits of argon ion milling, reactive ion beam etching, focused ion beam milling and plasma cleaning when used for TEM sample preparation. Advances in sample preparation procedures must also respect inherent problems such as thin foil surface relaxation effects, e.g. cleaved wedge geometries are more appropriate than conventional cross-sections for the quantitative characterisation of δ-doped layers. Choice of the right imaging technique for the problem to be addressed is illustrated through consideration of polySi/Si emitter interfaces within bipolar transistor structures. The development of microscopies for the rapid analysis of electronic materials requires wider consideration of non-destructive techniques of assessment, e.g. reflection high energy electron diffraction in a modified TEM is briefly described.