Advances in Resist Materials and Processing Technology: Photonic Devices Fabricated by Direct Lithography of Resist/Colloidal Nanocrystals Blend

Abstract

Lithographic techniques are the major driving force for the development of new photonic nanostructures. A wide range of techniques have been and are being developed for nano fabrication: e.g., deep UV (┣=200–290 nm) and extreme UV (┣ <200 nm) photolithography, electron-beam lithography (EBL), focused ion beam (FIB) lithography, X-ray lithography, scanning probe lithography, and others. The degree of accuracy, reproducibility and resolution guaranteed by lithographic techniques is definitely better than other nanofabrication processes, such as wet and dry etching, sputtering, evaporation and so on. For this reason, “all-lithographic” fabrication protocols are being proposed for the realization of photonic devices based on nonconventional materials such as organic fluorophores or wet-chemical synthesized colloidal nanocrystals (NCs), whose exploitation in nano-optoelectronics is more recent as compared with epitaxially grown semiconductor emitters. A potential approach for the fabrication of novel nanophotonic and nanoelectronic devices without recurring to traditional semiconductor processing technologies is represented by direct lithography of polymeric resists embedding active materials. For this purpose, colloidal nanocrystals appear as a promising active medium to be embedded into the hosting polymer, since they provide, with a high photochemical stability, emission wavelengths tunable from ultraviolet to infrared spectral region, high fluorescence efficiency, broad excitation spectra and narrow emission bands also at room temperature. Direct lithography of resist/NCs blends has proved to be an efficient strategy for the nanopositioning of NCs while preserving both the optical properties of the active material and the lithographic sensitivity of the hosting resist. The possibility of selectively localize semiconductor NCs on a substrate can lead to the fabrication of high performing photonic devices with novel active materials significantly cheaper than the traditional epitaxially grown active layers. The chapter is devoted to the presentation of several demonstrators of this innovative technique. Moreover, a survey of the fabrication results achieved by Source: Lithography, Book edited by: Michael Wang, ISBN 978-953-307-064-3, pp. 656, February 2010, INTECH, Croatia, downloaded from SCIYO.COM