Production Of High Temperature Superconductor Thin Film Microstructures And Transmission Lines

The discovery of high temperature (T>90 K) superconductivity in the rare-earth copper oxides has opened up the possibility of the use of this material for very high speed, low loss interconnects in electronic systems. The realization of this possibility depends on the development of successful techniques for the growth and processing of high quality, high Tc thin films. Due to the highly anisotropic nature of the R.E.-Ba -Cu- oxide superconductor the film must be well oriented, preferably with the copper oxide planes parallel to the plane of the substrate, in order to obtain the necessary high critical current density. The substrate must also be properly chosen to avoid unacceptably high dielectric dispersion and loss. Since the high Tc superconductor is highly reactive achieving compatibility with suitable substrates can be difficult. We have developed a high pressure reactive evaporation (HPRE) process for the in-situ formation of high Tc thin films at a comparably low growth temperature (T = 625C - 700C). Films grown by this technique on yttria-stabilized zirconium oxide and Mg0 crystalline substrates tend to be highly oriented and have yielded quite high critical current densities. These films can be readily patterned to micrometer dimensions by photolithography and ion etching. In this paper we report on the characterization and processing of high Tc thin films, and characteristics of thin film microstructures. Film properties important for high speed device applications will be discussed.