The effect of under and over develop time in Josephson junction fabrication process using electron beam lithography

Abstract

In the 1960s, the physicist Brian Josephson introduced the concept of Josephson tunnel junctions, which involve the tunneling of Cooper pairs across a barrier between superconducting electrodes. The typical methods of fabricating Josephson junction such as Dolan bridge and cross-type technique require specialized equipment for angle deposition. In this work, we present Josephson junction fabrication process using electron beam lithography that eliminates the need for angle deposition. The dose test was performed to optimize the right dose and we also explored various develop time. We observed that for PMMA A9 film with thickness 1.3 μm, the electron dose 280 μC/cm2 and develop time between 1.30 – 2.00 minutes produces clear pattern with sharp features. The effect of under and over develop time is shown such that there are resist residue left on the substrate after lift-off process and the longer develop time created an undercut.