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A site specific technique for cross-section transmission electron microscopy specimen preparation of difficult materials is presented. Focused ion beams are used to slice an electron transparent sliver of the specimen from a specific area of interest. Micromanipulation lift-out procedures are then used to transport the electron transparent specimen to a carbon coated copper grid for subsequent TEM analysis. The experimental procedures are described in detail and an example of the lift-out technique is presented.

Abstract:The focused ion beam~FIB! tool has been successfully used as both a stand alone analytical instrument and a means to prepare specimens for subsequent analysis by SEM, TEM, SIMS, XPS, and AUGER.In this work, special emphasis is given to TEM specimen preparation by the FIB lift-out technique. The fundamental ion/solid interactions that govern the FIB milling process are examined and discussed with respect to the preparation of electron transparent membranes. TRIM, a Monte Carlo simulation code, is used to physically model variables that influence FIB sputtering behavior. The results of such computer generated models are compared with empirical observations in a number of materials processed with an FEI 611 FIB workstation. The roles of incident ion attack angle, beam current, trench geometry, raster pattern, and target-material-dependent removal rates are considered. These interrelationships are used to explain observed phenomena and predict expected milling behaviors, thus increasing the potential for the FIB to be used more efficiently with reproducible results.

Particles of Zn powder have been studied to show that high-quality scanning electron microscope (SEM) and transmission electron microscope (TEM) specimens can be rapidly produced from a sitespecific region on a chosen particle by the focused ion beam (FIB) lift-out technique. A TEM specimen approximately 20-m long by 5-m wide was milled to electron transparency, extracted from the bulk particle, and micromanipulated onto a carbon coated copper mesh TEM grid. Using the FIB lift-out method, we were able to prepare a site-specific TEM specimen from a difficult material in under 3 hours. The TEM analysis of the lift-out specimen revealed a large amount of thin area free from characteristic signs of damage that may be observed as a result of conventional argon ion milling. The overall microstructure of the specimen prepared by the FIB lift-out method was consistent with samples prepared by conventional metallographic methods. A grain size of ϳ10 to 20 m was observed in all specimens by both TEM and SEM analysis. Light optical microscopy revealed the presence of internal voids in ϳ10 to 20 pct of all particles. The SEM analysis showed the voids to extend over ϳ70 pct of the particle volume in some cases.

Articles you may be interested inMilling of submicron channels on gold layer using double charged arsenic ion beam The use of focused ion beam ͑FIB͒ instruments for device modification and specimen preparation has become a mainstay in the microelectronics industry and in thin film characterization. The role of the FIB as a tool to rapidly prepare high quality transmission electron microscopy specimens is particularly significant. Special attention has been given to FIB milling of Cu and Si in the microelectronics arena. Although FIB applications involving Si have been extremely successful, it has been noted that Cu tends to present significant challenges to FIB milling because of effects such as the development of milling induced topographical features. We show evidence that links the occurrence of milling induced topography to the severity of redeposition. Specifically, Cu, which sputters ϳ2.5 times faster than Si, exhibits an increased susceptibility to redeposition related artifacts. In addition, the effects and the mechanism of Ga ϩ channeling in Cu is used to illustrate that Ga ϩ channeling reduces the sputtering yield, improves the quality of FIB mill cuts, and improves the surface characteristics of FIB milled Cu. Finally, a technique for improving FIB milling across grain boundaries or interfaces using ion channeling contrast is suggested.