Electron projection lithography (EPL) is one of the leading candidates for next-generation lithography at the 65-nm lithography node, particularly for contact levels. EPL has traditionally employed either an open stencil mask with a single patterned (perforated) scattering layer or a continuous membrane mask with a patterned scattering layer supported by an un-perforated membrane. This article reports on an experimental study of a type of EPL mask developed by Team Nanotec that employs a continuous ultrathin membrane (UTM) comprised of a trilayer of carbon, silicon nitride, and carbon. These UTM masks combine all of the benefits of continuous membrane masks with the higher energy throughput (and the smaller chromatic aberration) of an open stencil mask. (C) 2004 American Vacuum Society.