Accurate Removal of Implanted Gallium and Amorphous Damage from TEM Specimens after Focused Ion Beam (FIB) Preparation

Abstract

One of the most popular tools for TEM specimen preparation is gallium focused ion beam (FIB). It is well known that the FIB's high-energy Ga ions can damage a specimen's crystalline structure by introducing lattice defects (strain induction). FIB milling can also implant gallium ions into the specimen surface and cause surface amorphization [1]. An accurate and reproducible specimen preparation method that removes gallium and amorphous damage after FIB processing is necessary for TEM analysis. This work demonstrates how the quality of TEM specimens after FIB can be improved by using low energy argon ion milling. FIB cross-section specimens were lifted out from monocrystal (100)[011] silicon using a 30 keV Ga ion beam and thinned to 100 nm using various acceleration voltages. The specimens and Ga implantation thickness were quantified by X-ray characteristic emission measurement generated by the electron beam in the specimen. Thickness can be determined using the ϕ(ρz) model (the XPP approach proposed by Pouchou, et al. [2]) by comparing predicted and measured k-ratios.