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 <i>n</i> = 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.
© 2001 Optical Society of America
(050.1960) Diffraction and gratings : Diffraction theory
(090.2900) Holography : Optical storage materials
(110.2990) Imaging systems : Image formation theory
(110.5220) Imaging systems : Photolithography
(240.6680) Optics at surfaces : Surface plasmons
Richard J. Blaikie and Sharee J. McNab, "Evanescent interferometric lithography," Appl. Opt. 40, 1692-1698 (2001)