TEM sample preparation with focused ion beams

Abstract

The continuing reduction in the sizes of features of interest for integrated circuit failure analysis requires greater precision in transmission electron microscopy (TEM) sample preparation. With minimum feature sizes approaching 0.5 μm, the mere finding of such a feature at a polished edge, let alone preparing a TEM sample containing it becomes a formidable task. The required substantial thinning also increases the risk of loss of what may be a unique sample.We present in this paper a technique that allows localized thinning of cross-sectional TEM samples using a focused ion beam (FIB) machine. Standard preparation techniques are used to make a cross-sectional TEM sample that would otherwise be too thick to be very useful for TEM analysis. This sample is then placed in the FIB machine, which is used as a micromachining tool. No special surface preparation is necessary and the secondary electron signal generated by the ion beam provides an image that can be used to locate the feature of interest.