Conditions of ICP for a superconducting flux flow transistor and its etching characteristics

Superconducting flux flow transistors with a micron channel (3 μm) have been fabricated based on the flux flow by the inductively coupled plasma (ICP) etching technique. For a channel of superconducting vortex flow transistor (SFFT) with the high-Tc superconducting characteristic in YBaCuO, the proper ICP etching conditions were an ICP power of 700 W, r.f. power of 150 W, pressure in chamber of 5 mTorr, and mixing rate of etching gas for Ar:Cl2, 1:1. The sample etched by ICP produced smoother morphology than by H3PO4 etchant, while it made little difference with a sample by non-aqueous etchant, Br. The transresistance of an SFFT etched by the ICP technique was below 0.1 Ω at an Ibdy of 40 mA. Output resistance was below 0.2 Ω. It is expected that the transresistance can be improved by decreasing the thickness of the link and introducing the multi-link structure.