Fabrication of nanoperforated silicon membranes with tunable sized high aspect ratio holes

We present a fabrication process for free-standing, nanoperforated membranes which are made of single-crystalline silicon. The membranes are fabricated out of silicon-on-insulator wafers. The mask for nanoperforations is patterned on the device layer side of the wafer using nanoimprint lithography. The membrane is released by etching through the handle wafer and the buried oxide layer from the backside of the wafer. The nanoperforations are created by the final cryogenic deep reactive ion etching step through the device layer. The process circumvents problems related to notching effect. As the last process step, narrowing of the pores is done by conformal atomic layer deposition of aluminum oxide. The thickness of the membrane is 3 mum and pore diameters of 200 nm and 420 nm are demonstrated.