Microfabrication processes for high-Tc superconducting films

Microfabrication processes for Y-Ba-Cu-O films have been investigated using ion-beam techniques. High-T_c superconducting lines as narrow as 0.8 μm have been fabricated from epitaxial YBa₂Cu₃O_7-y films by Ar ion-beam etching (IBE) combined with focused ion-beam (FIB) lithography. The resulting lines, 1.3 μm wide and 2 mm long, showed a zero-resistance temperature of 81 K and a critical current density of 1.9×10⁴ A/cm² at 77.3 K. Maskless etching was carried out using a 130-keV Au⁺ FIB with a 0.1-μm-diameter beam. A 50-nm-thick film was patterned into 0.3-μm-wide lines at a dose of 5×10¹⁶ ions/cm² . In comparison with Ar IBE, Cl₂ reactive ion-beam etching exhibited an enhancement effect in sputtering yield. Ion implantation with 300-keV Si⁺⁺ FIB also indicated the possibility of producing submicron patterns by selectively modifying film properties from superconductive to normal or insulating