Low cost PMMA based photo-masks for 3D grey scale micro-structuring applications

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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.
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.

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Journal: TechConnect Briefs
Volume: 3, Technical Proceedings of the 2006 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: May 7, 2006
Pages: 214 - 217
Industry sector: Advanced Materials & Manufacturing
Topics: Advanced Manufacturing
ISBN: 0-9767985-8-1