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Processing Examples
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Copyright© 2006, University of Washington, used with permission
A 2 nm platinum film was used as a substrate for electron beam lithography of the cobalt patterns seen by transmission electron microscopy. The tricky part is to spin-coat the photoresist onto the 3-mm grid without damaging the film. A sugar aerosol solution was used to "glue" the grid onto a silicon wafer, as the aerosol solution was insoluble to the photoresist solvent. After drying, the edges of the grid were cut away with a razor blade to expose the dried aerosol solution and dissolved away with deionized water. Afterwards, conventional electron-beam lithography of the above pattern was performed using J.C.Nabity Lithography Systems on a JEOL 4200 SEM. After development of the polymethylmethacrylate resist (PMMA 950k Mw in anisol) in 1:3 isopropanol:methyl butyl ketone to expose the pattern, fabrication was performed directly on the substrate by electrodeposition of cobalt from a cobaltous sulfate electrolyte in boric acid. The photoresist was then removed in acetone to reveal the pattern seen above, a series of "poles" of 100 nm diameter spaced 250 nm apart.
