Surface relief subwavelength gratings by means of total internal reflection evanescent wave interference lithography

Abstract

We present the use of total internal reflection (TIR) evanescent waves for lithography purposes. In particular, we focus our attention on their singular capabilities to nano-structure surface relief gratings and the potentialities for nano-photonic device fabrication. Interference of two (or more) evanescent waves achieves periodic linear (or 2D) surface relief gratings of around 100 nm period depending on the wavelength and materials used. In contrast to common and some newer lithographic techniques, the evanescent wave does not propagate all through the film, allowing fabrication of surface profiles with maximum height features limited to around the wavelength of the exposure. Here, we present an analysis of several structures and profiles for linear gratings—many of which are not achievable with known interference photolithographic techniques—and some experimental results validating the model of evanescent wave lithography proposed. Possible applications in the field of nano-photonic devices are antireflection treatments, polarizers, diffraction gratings, micro- and nano-lens arrays, etc. We also find in the technique a great potential for other nano-technologies, as in the fabrication of field emitter arrays for displays, as templates for self-assembling structures, etc.