COMBINED METHOD OF ELECTRON-BEAM LITHOGRAPHY AND ION-IMPLANTATION TECHNIQUES FOR THE FABRICATION OF HIGH-TEMPERATURE SUPERCONDUCTOR JOSEPHSON-JUNCTIONS

Established semiconductor process technologies are demonstrated to be suitable for the fabrication of high temperature superconductor Joseph son junctions. Single YBa2Cu3O7 bridges have been modified by local ox ygen ion irradiation through a narrow slit in an implantation mask, wh ich was formed by electron-beam lithography and reactive ion etching. The influence of the slit dimension, the mask thickness, and the irrad iation dose have been investigated systematically. The critical curren t and the normal resistance of the modified microbridges were found to be controllable by these parameters achieving a great variety of diff erent I/V curves, i.e., resistive or superconductor/normal/superconduc tor (SNS) Josephson junction behavior. Further investigations were per formed on SNS junctions. Microwave irradiation of the microbridges exh ibits Shapiro steps in the I/V characteristics. In de superconducting quantum interference devices a voltage modulation as a function of an applied magnetic flux is observed. (C) 1996 American Vacuum Society.