Processing study of SU-8 pillar profiles with high aspect ratio by electron-beam lithography

• E-beam lithography of SU-8 pillars for 5 μm and 10 μm height has been studied.
• SU-8 pillars with different profiles have been fabricated and discussed.
• Processing study using proximity effect for profile controlling have been studied.
• Optical characterization of SU-8 pillars have been carried out.

We report the fabrication of micro-pitched SU-8 pillar arrays with height up to 5 μm and aspect ratio of 7.14:1 by electron beam lithography (EBL) at 100 keV, combined with a hot developing process. Careful study of processing latitude for geometry parameters of SU-8 pillars was conducted to achieve three different profiles, vertical pillar for biosensing application, trapezoidal shape for antireflection of light in solar cells as well as in displays, and final pillars with thick residuals in the gaps. It was found in our work that SU-8 is particularly a good candidate for tall micro/nano structures with various shapes when the unavoidable proximity effect in the EBL was exploited, which was enhanced by the ultra-high sensitivity of epoxy groups in SU-8. Optical properties of the fabricated structures have been characterized. To the best of our knowledge, pillar like structures of SU-8 in the height range of 5 μm have not been addressed sufficiently despite their broad potential applications in bioscience, environment protection, display and renewable energy sources etc.

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