A high transition temperature superconducting integrated circuit

The design and fabrication of the first superconducting integrated circuit capable of operating at over 10K. The primary component of the circuit is a dc Superconducting Quantum Interference Device (SQUID) which is extremely sensitive to magnetic fields. The dc SQUID consists of two superconductor-normal metal-superconductor (sNS) Josephson microbridges which are fabricated using a step edge process which permits the use of high transition temperature superconductors. By utilizing electron bean lithography in conjunction with ion beam etching, very small microbridges can be produced. Such microbridges lead to high performance dc SQUIDs with products of the critical current and normal resistance reaching mV at 4.2 K. These SQUIDs were extensively characterized, and exhibit excellent electrical characteristics over a wide temperature range. The completed circuits operated successfully over a wide temperature range, from 4.2 K to 14 K. Limitations were encountered in the form of an excess inductance. The origins of such an inductance have important and wide ranging ramifications for superconducting devices employing the high transition temperature materials.