Electron-Beam Resists for Lift-Off Processing with Potential Application to Josephson Integrated Circuits

Several electron-beam resists suitable for lift-off processing have been investigated with particular attention to the requirements for fabricating Pb-alloy Josephson integrated circuits. The desired resist must perform well with a baking temperature near 70°C, provide a reproducible undercut edge profile with good linewidth control, and adhere to the necessary substrates. Diazo resists as well as the commonly used PMMA and copolymer materials were studied. Initial results suggest that ®AZ-1350J soaked in chlorobenzene to enhance the undercut profile can satisfy many of these requirements. At present, the amount of undercut obtained is larger than desired, limiting the minimum separation between exposed features to about 1.5 µm.