Proton beam writing for minimum step lithography in multilayer patterning

Mihir Sarkar; Neeraj Shukla; Nobin Banerji; Yashowanta N. Mohapatra

doi:10.1117/12.927402

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15 October 2012 Proton beam writing for minimum step lithography in multilayer patterning

Mihir Sarkar, Neeraj Shukla, Nobin Banerji, Yashowanta N. Mohapatra

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Proceedings Volume 8549, 16th International Workshop on Physics of Semiconductor Devices; 854912 (2012) https://doi.org/10.1117/12.927402
Event: 16th International Workshop on Physics of Semiconductor Devices, 2011, Kanpur, India

Abstract

We report the use of proton beam lithography as a convenient procedure consisting of minimum steps for micropatterning in polymer multilayers comprising of a metallic intermediate layer – a structure which can facilitate many application including vertical organic field effect transistors. We have used focused micro-beam of 2 MeV protons to pattern array of micro-holes in a 1 μm thick tri-layer film. A tri-layer film was prepared by spin coating 400 nm poly(methyl methacrylate) (PMMA) film on a glass substrate followed by thermal evaporation of 200 nm thick aluminium film and spin coating of a second PMMA layer of thickness 400 nm on the top. MeV protons suffer very little scattering inside the tri-layer film and pass through the tri-layer following almost straight path. Thus MeV proton beam causes molecular chain scissions in the top and the bottom PMMA layer in desired patterns in a single exposure which is not possible with other techniques such as e-beam lithography (EBL) or photolithography. By following a step by step development/etching of the three layers, we achieved an array of through micro-holes in the tri-layer film on the glass substrate. Potential application of such micro-patterns is discussed. We also report optimized parameters of proton beam writing for arrayed micro-structures fabrication in single layer of two different common polymer resists, SU-8 and PMMA. The surface morphology and side wall broadening of the fabricated structures were characterized using SEM and profilometer study respectively.

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Mihir Sarkar, Neeraj Shukla, Nobin Banerji, and Yashowanta N. Mohapatra "Proton beam writing for minimum step lithography in multilayer patterning", Proc. SPIE 8549, 16th International Workshop on Physics of Semiconductor Devices, 854912 (15 October 2012); https://doi.org/10.1117/12.927402

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