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Base Electrodes for Tunneling Junctions

IP.com Disclosure Number: IPCOM000082048D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Greiner, JH: AUTHOR

Abstract

In the fabrication of Josephson tunneling devices, the base electrode which is oxidized to form the tunnel barrier has to remain stable during several processing steps, including processing of the tunnel junction, heat treatment for alloy homogenization, photoprocessing steps, and barrier oxidation. After the tunnel junction has been formed, stability is required when the rest of the tunnel device is fabricated and during later circuit completion. Additionally, the base electrode has to remain stable during subsequent annealing processes and during low-temperature cycling. To achieve this, it is proposed to improve the base electrode in the tunneling device.

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Base Electrodes for Tunneling Junctions

In the fabrication of Josephson tunneling devices, the base electrode which is oxidized to form the tunnel barrier has to remain stable during several processing steps, including processing of the tunnel junction, heat treatment for alloy homogenization, photoprocessing steps, and barrier oxidation. After the tunnel junction has been formed, stability is required when the rest of the tunnel device is fabricated and during later circuit completion. Additionally, the base electrode has to remain stable during subsequent annealing processes and during low-temperature cycling. To achieve this, it is proposed to improve the base electrode in the tunneling device.

To improve the base electrode, a thin oxide is formed on it after formation, but prior to further processing. This oxide protective layer decreases hillock formation on lead alloy films during heating cycles above room temperature, such as would be used to provide alloy homogenization.

Ion bombardment of the base electrode in an inert gas atmosphere prior to tunnel barrier oxidation has also been observed to decrease hillock formation on lead films, which are oxidized by an RF plasma discharge to provide the tunnel barrier. The oxide layer usually formed on the base electrodes is epitaxial and large stresses between the base electrode and the oxide can result, due to lattice mismatch. This type of stress is alleviated by ion bombardment which removes the protective oxid...