Josephson Field Effect Transistor Channel Fabrication

A methodology for the fabrication of a SiO2-based Josephson Field Effect Transistor (JoFET) channel using wet etching for patterning of niobium contacts was developed. Unlike to the typical use of dry etching techniques, this approach tests a chemical etching alternative to minimize substrate damage, which can limit supercurrent flow in the channel.

The Standard Cleaning 1 (SC-1) solution was identified as an efficient etchant for niobium. Suitable conditions for this process were determined experimentally, and the various etching stages were studied using optical microscopy, profilometry, scanning electron microscopy, and atomic force microscopy.

A thin passivation niobium oxide layer was identified on the sputtered niobium film surface, introducing an etching delay at the beginning of the process. Additionally, suitable etching selectivity between niobium and the underlying SiO2 substrate was achieved, minimizing channel damage and demonstrating SC-1 solution is adequate for this application.

This methodology offers a valuable process that can be integrated into the extensive repertoire of micro- and nanofabrication techniques in the semiconductor industry, particularly for developing superconductive devices where niobium is a critical component.