Fabricating High-density Microarrays for Retinal Recording (original) (raw)

Mathieson, K., Cunningham, W. ORCID: https://orcid.org/0000-0001-5517-8795, Marchal, J., Melone, J., Horn, M., O'Shea, V. ORCID: https://orcid.org/0000-0001-7183-1205, Smith, K.M., Litke, A., Chichilnisky, E.J. and Rahman, M.(2003) Fabricating High-density Microarrays for Retinal Recording. In: 28th International Conference on Micro and Nanoengineering, Lugano, Switzerland, 16-19 September 2002, 520 -527. (doi: 10.1016/S0167-9317(03)00109-6)

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Publisher's URL: http://dx.doi.org/10.1016/S0167-9317(03)00109-6

Abstract

Understanding how the retina encodes the visual scene is a problem, which requires large area, high-density microelectrode arrays to solve. The correlated signals that emerge from the output (ganglion) cells of the retina form a code, which is not well understood. We use a combination of electron beam lithography, photolithography and dry-etch pattern transfer to realise a 519-electrode array in the transparent conductor indium tin oxide (ITO). The electrodes are spaced at 60 mum in a hexagonal close-packed geometry. A mix and match lithography procedure is utilised, whereby the high-density inner region is fabricated using electron beam lithography whilst the outer sections are realised by photolithography. Reactive ion etching (RIE), using CH4/H-2, of the ITO forms the array structure and SF6 RIE allows resist removal and patterning of vias through a plasma deposited Si3N4 protective layer. The electrical properties of the ITO layer are unaffected by the etching procedures. A reliable method for achieving low-impedance electroplated platinum electrodes has been employed to yield electrode impedances of similar to 20 kOmega. An array fabricated using these dry-etch techniques is shown to record action potentials from live retinal tissue in neurophysiological experiments.

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