Br. David et al., A MULTILAYER PROCESS FOR THE FABRICATION OF HTSC FLUX TRANSFORMERS AND SQUIDS, Superconductor science and technology, 7(5), 1994, pp. 287-289
A multi-layer technology, based on YBaCuO as the superconducting mater
ial and SrTiO3 as the insulating material, is described. Patterning is
performed by photolithography and Ar-ion-beam etching under flat inci
dence. Using a resist bake-out prior to the etching, step angles in th
e patterned lower film of less than 20-degrees are obtained. Supercond
ucting 10-turn thin-film coils have been fabricated with transition te
mperatures of up to 83 K and critical current densities at 77 K of 2 x
10(5) A cm-2 . Furthermore we have fabricated a thin-film flux transf
ormer and combined it in flip-chip configuration with a low-noise YBCO
step-edge DC SQUID. We measured a magnetic field resolution of the co
mplete magnetometer of 200 fT Hz-1/2 at 1 Hz, dominated by the SQUID n
oise itself.