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Browse Prior Art Database

Making Josephson Tunnel Junctions

IP.com Disclosure Number: IPCOM000082709D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Broom, RF: AUTHOR

Abstract

Josephson tunnel junctions are conventionally made by sandwiching upon a substrate s metal electrode capable of superconductivity, a very thin insulating layer, and a second superconductive electrode. Photolithographic techniques are usually employed in the process.

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Making Josephson Tunnel Junctions

Josephson tunnel junctions are conventionally made by sandwiching upon a substrate s metal electrode capable of superconductivity, a very thin insulating layer, and a second superconductive electrode. Photolithographic techniques are usually employed in the process.

Contamination of the very sensitive insulation which normally is exposed during photoresist developing and stripping steps can be avoided, by covering the oxide which constitutes the insulation by a thin film of gold. Oxide deposition is now carried out immediately after evaporation formation of the lower electrode, and without stripping the resist or removing the wafer from the vacuum system. Thereupon, the vacuum system is rapidly pumped down to low pressure and a thin layer of gold is evaporated over the wafer. The oxide is now sandwiched between the original metal and the gold film.

The wafer is now removed from the vacuum system and prepared for the second superconductor evaporation in the usual way. The fragile oxide is protected during this operation against any contamination by the passive and oxidation resistant gold film. Since the gold film is thin enough, i.e., far below 1000 angstroms, it will diffuse into the second metal electrode and not affect the superconductivity of the electrode. The second electrode, not shown in the drawing, will finally be deposited on top of the structure.

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