Nanopores fabricated by focused ion beam milling technology

A new approach to fabricating nanopore is presented. It is based on focused ion beam (FIB) sputtering to mill through a silicon nitride (Si₃N₄) membrane first, then followed by aluminum nitride (AlN) thin film deposition through the milled hole to narrow the pore size. FIB sputtering properties of Si₃N₄ membranes were investigated in order to achieve high aspect ratio holes through the membrane. The parameters of AlN deposition were optimized so that the final nanopore size can be finely controlled. A nanopore array with 70 nm pore-diameter was made in a Si₃N₄ membrane by FIB milling technology. The following AlN deposition was able to narrow the nanopores further down to 12 nm pore-diameter.