high-resolution lithography, where their sub-10 nm spot sizes enable the patterning of diverse nanostructures, and surface compositional analysis, where their ability to sputter material in a localized area allows discrete components of a device or circuit to be characterized. Recently, the authors have capitalized on the FIB＇s versatility by using it for microelectromechanical sensor fabrication as well as post-processing device characterization. The HRL FIB : nanoprobe system has been used in the fabrication of high-performance surface-micromachined accelerometers operating on the principle of tunneling between a cantilevered beam and a sub-0.1-mu m-diam tip lying beneath it on a Si substrate. The 8-nm-diam FIB has been used to pattern small dots in a bilevel negative-positive resist layer which are then transferred into a Au layer to form pyramid-shaped tunneling tip structures whose narrow dimensions are essential to high device performance and stability. High-purity, contamination-free Au on both the tunneling tip and cantilever underside is also critical to high-sensitivity tunneling devices. Because the undersides of the beams cannot be viewed with a scanning electron microscopy, even at high mechanical tilt angles, the cantilevers must be physically peeled back in order to expose their bottom surfaces and analyze them for cleanliness. Depending on the material used for fabricating the cantilevers, the rigidity of the structures can render them difficult to bend. We have used a commercial FIB milling system to cut through a portion of the cantilever width, thus creating a hinge, which facilitates the subsequent peeling back of the structure. Comparison of Auger spectroscopy data on peeled-back beams with and without a FIB-milled hinge shows similar surface contamination levels, indicating that redeposited material due to ion milling is localized enough to not affect the compositional analysis of the tunneling region.