Finish-pass strategy to improve sidewall angle and processing time in FIB milled structures

Focused Ion Beams (FIB) systems are employed for their ability to manipulate and remove material on the nanoscale for creating complex structures. By splitting the milling job into multiple sub-patterns, consisting of a bulk milling pattern, and one or more finish pass patterns that follow the contours of the milling geometry, we show that one can counteract the effect of re-deposition on the sidewalls. Our tests showed a reduction in sidewall angle from 96^◦to 92.5^◦using identical beam conditions and nearly the same processing time employing only one finish pass pattern. Further, by assigning different beam currents to three different sub-patterns, we were able to reduce angles to 92^◦, while cutting total milling time by 10%. Improving our strategy may render FIB systems a potential as effective nanofabrication tools applicable beyond creating prototypes and lamellae for material characterization.