Design of hybrid sol–gel films for direct x-ray and electron beam nanopatterning

Abstract

New epoxy based sol–gel organic inorganic materials, showing lithographic resist-likeproperties without the addition of any photocatalysts, are presented. To obtain a materialsensitive to radiation, specific sol–gel syntheses based on an organically modified alkoxidecontaining an epoxy ring, 3-glycidoxypropyltrimethoxysilane (GPTMS), have beendeveloped. The synthesis and the patternability of hybrid materials have been obtainedcontrolling the inorganic crosslinking degree and with an almost total absence of organicpolymerization. Two examples of directly patternable hybrid films, called GB and GGe,have been synthesized using acidic (GGe) and basic (GB) conditions and obtainingdifferent compositions.After electron beam lithography (EBL) or x-ray synchrotron radiation lithography (XRL)the polymerization of the organic component of the sol–gel film occurs, generating ahardening of the structure after post-exposure baking. The exposed polymerized materialbecomes insoluble, determining a negative resist-like behaviour of the film: the lithographicprocess of nanopatterning results from the dissolution of the unexposed areas in propersolvents (developers). Spatial resolution of the order of 200 nm is reported and a contrast of2.2 is achieved.The novelty of this work is that epoxy based materials, which have enhancedthermomechanical stability with respect to the more usual acrylic based resins, are directlynanopatterned for the first time by electron beam (EB) and/or x-ray beam radiationexposure without the aid of catalysts for polymerization. In contrast to common resiststhat are sacrificial layers of the fabrication process, direct patternable sol–gel hybridsconstitute the final material of the devices. In fact, an example of doping with a lightemitting dye is reported together with the achievement of directly patterned structures byEBL and XRL.