FOCUSED-ION-BEAM-INDUCED GAS ETCHING

Focused ion beam (FIB)-assisted gas etching has several advantages over physical sputtering in many applications. Advantages include etch rate enhancements of one to two orders of magnitude, dramatically reduced redeposition of etched material on sidewalls in high-aspect-ratio structures, etch selectivity, and reduced implantation of the primary ion species in the sample. Applications which benefit from focused ion beam (FIB) gas etching include photomask and X-ray mask defect repair, integrated circuit modification for failure analysis, and sample preparation for scanning electron microscope and transmission electron microscope analysis. This paper describes a simple phenomenological model which takes into account the ion beam and scanning parameters, gas flux, and basic material constants. Approximate formulas are given in terms of these parameters and compared to experimental results.