such as secondary electrons from ionizing radiation or photoacid generation and diffusion, cannot be avoided with interference lithography. For instance, the secondary electron range is roughly indicated by the width of carbon contamination (~20 nm) at the surface induced by a focused (2 nm) electron beam. This indicates that the lithographic patterning of 20 nm half-pitch features or smaller will be significantly affected by factors other than the interference pattern, such as the cleanliness of the vacuum. References External links Large-area patterning using interference and nanoimprint lithography Interference lithography at Fraunhofer ISE Lithography (microfabrication)