Ion channeling effects on the focused ion beam milling of Cu

The use of focused ion beam (FIB) instruments for device modification and s pecimen 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 particu larly significant. Special attention has been given to FIB milling of Cu an d 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 develo pment of milling induced topographical features. We show evidence that link s the occurrence of milling induced topography to the severity of redeposit ion. Specifically, Cu, which sputters similar to2.5 times faster than Si, e xhibits an increased susceptibility to redeposition related artifacts. In a ddition, the effects and the mechanism of Ga+ channeling in Cu is used to i llustrate that Ga+ channeling reduces the sputtering yield, improves the qu ality of FIB mill cuts, and improves the surface characteristics of FIB mil led Cu. Finally, a technique for improving FIB milling across grain boundar ies or interfaces using ion channeling contrast is Suggested. (C) 2001 Amer ican Vacuum Society.