Authors: S. Lewis, R. Wheeler-Jones, R. Perks and V. Haynes
Affilation: Cardiff university, United Kingdom
Pages: 214 - 217
Keywords: 3D grey scale, nanoparticles, Al2O3, TiO2, optical transmission
Grey scale lithography is a useful technique for the fabrication of three dimensional microstructures. Dose dependent positive resist materials are well suited to this application; subsequent dry etching through a suitably patterned etch mask can enable a three dimensional structure to be transferred into a substrate material. Electron beam (e-beam) lithography; whilst having the capability of producing such an etch mask, is an inherently slow and relatively expensive process.<br> <br>This work describes the fabrication of a reusable grey scale optical mask based on a nano-particle Polymethylmethacrylate (PMMA) composite. A common e-beam resist PMMA950k was used in this study; TiO2 and Al2O3 nano-particles typically 30nm in size were interspersed within the PMMA. This composite was found to have reduced optical transparency whilst maintaining its properties as an e-beam resist. Once patterned, this mask was used to expose S1813 photo resist using a standard mask aligner.