Evanescent interferometric lithography.
ABSTRACT Simulation results are presented to illustrate the main features of what we believe is a new photolithographic technique, evanescent interferometric lithography (EIL). The technique exploits interference between resonantly enhanced, evanescently decaying diffracted orders to create a frequency-doubled intensity pattern in the near field of a metallic diffraction grating. It is shown that the intensity in a grating's near field can be enhanced significantly compared with conventional interferometric lithography. Contrast in the interference pattern is also increased, owing to a reduction in the zeroth-order transmission near resonance. The pattern's depth of field reduces as the wavelength is increased beyond cutoff of the first-order diffracted components, and results are presented showing the trade-offs that can be made between depth of field and intensity enhancement. Examples are given for a 270-nm-period grating embedded in material with refractive index n = 1.6 and illuminated with wavelengths near 450 nm. Under these conditions it is predicted that high-intensity, high-contrast patterns with 135-nm period can be formed in photoresists more than 50 nm thick.
Article: An asymmetric multilayer pendry lens[Show abstract] [Hide abstract]
ABSTRACT: The optical-band subwavelength imaging by a multilayer Pendry lens consisting of alternating layers of a metal with the permittivity ε m d = −ε m is considered. In the earlier papers by Pendry and Ramakrishna, it is shown that, in a nonideal case, i.e., for |ε d | = |ε m | ≠ 1, the image can be obtained only with the use of an asymmetric scheme, when the image is formed in a medium with a permittivity equal to ε d , the source being located in vacuum. However, in this case, the image quality is impaired (the image spectrum is narrowed). This phenomenon is explained in this study.Journal of Communications Technology and Electronics 01/2007; 52(9):1031-1036. · 0.33 Impact Factor
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ABSTRACT: Near-field imaging through plasmonic 'superlensing' layers can offer advantages of improved working distance (i.e. introducing the equivalent of a focal length) and control over image intensity compared to simple near-field imaging. In a photolithographic environment at ultra-violet (UV) wavelengths the imaging performance of single- and multi-layer silver plasmonic superlenses has been studied both experimentally and via computer simulations. Super-resolution imaging has been demonstrated experimentally, with the sub-100 nm resolution currently being limited by issues of roughness in the silver layers and the ability to deposit high-quality silver-dielectric multilayers. The simulation studies have shown that super-resolved imaging should be possible using surprisingly thick silver layers (>100 nm), with the cost of much reduced image intensity, which is something that is yet to be shown experimentally. The use of multilayer plasmonic superlenses also introduces richness to the imaging behaviour, with very high transmission possible for certain spatial frequency components in the image. This has been widely touted as a means for improving image resolution, but the complexity of the spatial-frequency transfer functions for these systems does not make this a universal fact for all classes of objects. Examples of imaging situations are given where multi-layer superlenses are actually detrimental to the image quality, such as the case of closely-separated dark-line objects on an otherwise bright background.01/2008;
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ABSTRACT: A material characterized by an anisotropic tensor permittivity with a negative value of one of the diagonal components is considered. It is shown that a plate fabricated from such a material ensures superresolution for any polarization. Being different from a plasmon resonance used in a Pendry lens, the mechanism of resolution improvement involves filtering of near-field harmonics. The results obtained are used to interpret experiments on superresolution. In these experiments, metal wires are used in the microwave band and a silver film applied in photolithography is employed in the optical band.Journal of Communications Technology and Electronics 01/2006; 51(7):780-787. · 0.33 Impact Factor