Milling a silicon nitride membrane by focused ion beam

An ultrathin amorphous membrane, such as that made of silicon nitride (SiN) suspended on silicon substrate, is a popular platform for various applications. However, its hardness causes many difficult technical problems for patterning, especially when combined with other fabrication processes. In nanofabrication, focused ion beam (FIB) is a popular milling technique. It would be a perfect tool for perforating the SiN membrane, but the ion beam charges the membrane, induces stress, and breaks them sporadically. The authors design a metallic structure near the cutting area to neutralize the charges. It reduces stress on the membrane and enables the perforation. Commercial SiN membranes are perforated with FIB and are suspended on thin legs on silicon chip. The authors study and discuss various designs and the applicability of this approach.Peer reviewe