Interference lithography: a powerful tool for fabricating periodic structures

In this review the basic principles of interference lithography (IL) are described. IL is emerging as one of the most powerful yet relatively inexpensive methodologies for creating large-area patterns with micron- to sub-micron periodicities. N-dimensional periodic structures (N <= 3) can be obtained by interfering (N + 1) non-coplanar beams in a photoresist. The symmetry and shape of the unit cell can be conveniently controlled by varying the intensities, geometries, polarizations, and phases of the beams involved. IL done with shorter wavelength lasers and/or liquid immersion lithography can create features with sub-50 nm dimensions. Such periodic structures are beginning to find wide use in photonic crystal science, optical telecommunications, data storage, and the integrated circuit industry. Newer innovations such as diffraction element assisted lithography or DEAL and phase-controlled IL for making two-dimensional structures are also discussed. SEM images of two-dimensional patterns created by three-beam non-coplanar interference lithography. The upper left hand image corresponds to the case when the phases of the three beams used to make the exposure are equal. The remaining images correspond to situations where one laser beam has been given [GRAPHICS] a different phase relative to the other two beams when making the exposure. (C) 2010 by WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim