Study on diameter of nanopore with focus ion beam

This paper studies the relation of nanopore diameter to film thickness and FIB action time with focus ion beam (FIB). First, the fabrication process for free-standing silicon nitride (Si₃N₄) films was introduced and got 300 nm and 200 nm thick film at last. Then, a series of pores with different diameters were milled on films under different FIB action time. Subsequently, the relation was analyzed. Conclusions: 1) Nanopore diameter was reduced with the decrease of action time till to t_min that was the minimum time for milling a pore. Simultaneously a pore with minimum diameter named d_min can be obtained. 2) The increase of action time caused nanopore expansion but the expansion rate decreased gradually. However, when the time increased to a certain value named t_max, the nanopore diameter didn´t expand any more but tended to a stable diameter named d_max 3) With the action time increasing, the expansion rate decreased till to zero. 4) According to the data, we can easily know that the thicker film had less t_min and t_max value as well as slower expansion rate and vice versa.