The Focused Ion Beam Fold-Out: Sample Preparation Method for Transmission Electron Microscopy

We have developed the focused ion beam (FIB) fold-out technique, for transmission electron microscopy (TEM) sample preparation in which there is no fine polishing or dimpling, thus saving turnaround time. It does not require a nanomanipulator yet is still site specific. The sample wafer is cut to shape, polished down, and then placed in a FIB system. A tab containing the area of interest is created by ion milling and then "folded out" from the bulk sample. This method also allows a plan-view of the sample by removing material below the wafer's surface film or device near the polished edge. In the final step, the sample is thinned to electron transparency, ready to be analyzed in the TEM. With both a cross section and plan-view, our technique gives microscopists a powerful tool in analyzing multiple zone axes in one TEM session. The nature of the polished sample edge also includes the ability to sample many areas, allowing the user to examine a very large device or sample. More importantly, this technique could make multiple site-specific e-beam transparent specimens in one polished sample, which is difficult to do when prepared by other methods.