100‐keVe‐beam lithography and electroplating of gold have been used to fabricate a device for the measurement of quantum changes in magnetic flux. The structure is defined in a 200‐nm‐thick layer of a copolymer of methyl methacrylate and methacrylic acid (PMMA/MAA) on top of a Si wafer covered by 150 nm of Si3N4. The device is a square frame of 2×2 &mgr;m2and 100‐nm linewidth. Gold was electroplated to a thickness of 100 nm. This technique allows the fabrication of high resolution, high aspect ratio gold structures.