A critical condition in Fresnel diffraction used for ultra-high resolutionlithographic printing

The adoption of a novel method for producing fine features by 1 nm proximit y x-ray lithography would solve all of the current technical limitations to its extensibility. These limitations include the fabrication of fine featu res on masks and the maintenance of narrow mask-wafer gaps. Previously, wit h demagnification by bias, we described line features of 43 nm width produc ed with comparatively large clear mask features and large mask-wafer gaps. The method is generally applicable and has been shown to be extensible to b eyond 25 nm printed features sizes on the wafer The demagnification, x1-x6, is a result of Fresnel diffraction and occurs without lenses or mirrors. T he method takes advantage of the modern control of resist processing and ha s good exposure stability. We now expand on the optimization of the process by defining and explaining the critical condition and by demonstrating the consistency of various types of simulation. The simulations demonstrate th e effects of the gap width, non-symmetric rectangular masks, spectral bandw idth, outriggers, T junctions, blur, etc. In two-dimensional images, the sp ectral bandwidth allows sharp features due to interference and effectively eliminates ripple parallel to the longer dimension. Demagnification by expo sure near the critical condition extends the most mature of the next genera tion lithographies which we define generically-following actual current Lit hographic practice-in terms of the departure from the classical requirement for fidelity in the reproduction of masks. Specifically, for 1 nm proximit y lithography, demagnification of critical features greatly facilitates the printing of fine features.