E.O. Lawrence Berkeley National Laboratory

APPLICATION OF TECHNOLOGY:

• Microelectronics--interconnection of circuit elements
• Medical imaging--imaging magnetic signals emitted by human hearts and brains as a diagnostic tool
• Geological applications--detect changes in magnetic fields, on location (natural resource location)
• Laboratory instrumentation--susceptometers, magnetometers, voltmeters, ammeters
• Non-destructive eveluation

ADVANTAGES:

• Enables the construction of multilayer interconnects from the high transition temperature (Tc) superconducting material, YBCO.
• Readily extendable to different substrates, deposition techniques, and insulation materials, and to structures with more than two superconducting layers.
• The choice of materials used to form insulating films is not limited to strontium titanate but can be extended to other materials that grow epitaxially in multilayer structures with YBCO.
• Structures with more than two high Tc superconducting layers can be fabricated.

ABSTRACT: Technique to fabricate multilayer interconnects and multiturn flux transformers for use with direct current superconducting quantum interference devices (SQUIDs). Berkeley National Laboratory's multilayer structures use the high transition temperature (high Tc) superconductor YBa2Cu3O7-x -- yttrium-barium-copper-oxide (YBCO). In these trilayer thin-film structures, YBCO - insulator - YBCO, each film is deposited and patterned independently using conventional photolithographic techniques.

Using photolithographic techniques, John Clarke at Berkeley Lab was able to pattern the two YBCO films into strips (wires) with features as small as a few microns. Circuit elements such as crossovers, places where crossing strips of YBCO are electrically isolated by the intervening insulating film, and window contacts, places where the two YBCO films make superconducting electrical contact through a hole patterned into the insulating layer, can be formed using the Berkeley National Laboratory processes. Photolithographic techniques are considered important both for miniaturization and also for permitting large-scale, economical production of devices.

The high Tc crossover and via (connections through windows) technology has enabled Berkeley National Laboratory to build the first high Tc flux transformer with 10-turn multilayer input coils. The flux transformer increases the sensitivity of magnetometers based on dc Superconducting QUantum Interference Devices (SQUIDs). During tests, the devices performed well at temperatures as high as 86 Kelvin (minus 187 centigrade).

High Tc SQUIDs, combined with the new Berkeley National Laboratory materials technology, can measure magnetic signals emitted by the heart with greater sensitivity than ever before.

STATUS: U.S. Patent #5,256,636. Available for licensing

REFERENCE NUMBER: IB-797

FOR MORE INFORMATION, SEE:

F. Ludwig, E. Dantsker, D. Koelles, R. Kleiner, A. H. Miklich, and J. Clarke, "Multilayer Magnetometers Based on High-Tc SQUIDs," Applied Superconductivity Vol. 3, No. 7-10, pp. 383-398, 1995

SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:

• High Tc SQUID Circuits Suppress Intrinsic Magnetic Field Noise (IB-1221)
• SQUID-Based, Asymmetric, Planar Gradiometer Suppresses Ambient Magnetic Field Noise (IB-1298)
• NMR/MRI with Hyperpolarized Inert Gas and High Tc SQUID for
  Signal Enhancement and Detection (IB-1441)

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CONTACT:

Technology Transfer Department E.O. Lawrence Berkeley National Laboratory MS 90-1070 Berkeley, CA 94720 (510) 486-6467 FAX: (510) 486-6457 TTD@lbl.gov