Colloidal lithography-based fabrication of suspended nanoporous silicon nitride membranes

Nanoporous membranes provide a basis for constructing non-supported biomembranes, which enable biological processes such as ion and molecule transport through the biomembranes to be investigated under physiological conditions with ease of control. Preparation of such membranes usually requires expensive equipments and extensive experiences. In this paper, we provide a cheap and controllable scheme of high volume fabricating suspended nanoporous Si3N4 membranes on a Si wafer by combined colloidal lithography and standard Si fabrication technology including low cost ICP etching and anisotropic Si wet-etch. Si3N4 layers are grown on Si wafers. Polystyrene particles of 200-nm-diameter are then monodispersed on the Si3N4 layers based on electrostatic repulsions with an average density of 2%. This is followed by Cr masking, ICP etching and Si wet-etch processes to form suspended Si3N4 membranes with 200-nm-deep nanopores through the membranes. The well-aligned cylindrical nanopores have a low aspect radio of ca. 0.9, which would be beneficial to forming stable suspended lipid bilayers.