Milling yield estimation in focused ion beam milling of two-layer substrates

Abstract

The material removal rate or milling yield of using the focused ion beam (FIB) for milling two-layer substrates is studied. The preparation of the two-layer substrate is first presented and is followed by the procedure on conducting the milling experiment. The effects of the dwell time on the milling rate and the final profiles of the milled structures are investigated. The atomic force microscope (AFM) is applied for measuring the profiles of the milled channels. Based on the AFM measurements, a relatively simple formula is developed to estimate the milling yield, which is normally dictated by both the characteristics of sputtering and redeposition for channel milling. The estimated milling rates are then compared with the corresponding sputtering yields predicted using a different numerical scheme. The milling rates obtained presently are discovered to be roughly equal to the predicted normal-incidence sputtering yields for both layers involved. Consistency is found as the present findings are compared with other milling studies on single-layer substrates. Finally, concluding remarks that summarize the present work and suggest future work on FIB milling are included.