Paper AS-WeA5
Use of Ion-Solid Interaction Theory to Optimize FIB Processes

Wednesday, October 22, 2008, 3:00 pm, Room 207

Focused ion beam (FIB) techniques have been used over the years to prepare specimens for characterization in a wide range of analytical instruments. One of the more popular uses of FIB is for the production of transmission electron microscopy (TEM) specimens. The advent of FIB for the preparation of specimens for 3D atom probe tomography (APT) allows for analysis of multi-phased and multi-layered materials which in the past would have been considered difficult or impossible due to specimen preparation constraints. In addition, FIB prepared surfaces are now routinely used for the acquisition of electron backscatter diffraction (EBSD) patterns. This technique has been extended to the acquisition of 3D crystallography in a DualBeam (FIB+SEM) instrument. Typical FIB instruments operating at 30 keV can result in sufficient lateral ion implantation and/or amorphization surface damage to hinder quantitative high resolution TEM results. Amorphization damage can also degrade the quality of the EBSD pattern such that the pattern cannot be resolved. In addition, 30 keV FIB milling can cause sufficient ion mixing which can destroy the chemical/elemental integrity of interfaces, rendering the 3D APT analysis useless. New advances in ion columns allow for imaging and FIB milling to take place down to 500 eV. Specimens can be prepared using the fine probe size of the high energy beam, and then polished with low energy ions which replace the high energy implantation damage with minimal damage from the lower energy ions. These low energy FIB techniques allow for quantitative high resolution (S)TEM, improve the quality of the EBSD patterns, and allow for 3D APT without interferences from the Ga+ ion implantation. In addition, since materials exhibit different collision cascade characteristics as a function of incidence angle, prototyping can be optimized by controlling the incidence angle and scan direction of the ion beam which can influence the profile and aspect ratio of the milled region.