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Isolation Technique for Josephson Junction Gates

IP.com Disclosure Number: IPCOM000084325D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Broom, RF: AUTHOR [+2]

Abstract

The manufacture of Josephson junction gates requires two distinct isolation layers, one between the ground plate and the lower junction electrode, and one between the upper junction electrode and the control line. Conventionally both layers are made of SiO.

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Isolation Technique for Josephson Junction Gates

The manufacture of Josephson junction gates requires two distinct isolation layers, one between the ground plate and the lower junction electrode, and one between the upper junction electrode and the control line. Conventionally both layers are made of SiO.

If the ground plate consists of niobium it is first anodized to provide additional isolation. Since no stable native oxide can be formed on lead electrodes, these are prone to accidental shorts through pinholes or other defects in the SiO. This is also a problem where the upper isolation layer has to cover the sharp step at the edges of the upper electrode, and should be thin to improve magnetic coupling between the control line and junction.

The risk of accidental short circuits is reduced by admitting oxygen after depositing the isolation layer, and carrying out an RF plasma treatment at the pressure of 20-50 mT and an RF voltage of 300-400 Vpp. This will remove some SiO by the oxygen plasma, convert it to SiO(2) and by scattering redeposit it everywhere. As a result, any exposed metal surfaces at the pinholes or edges previously shadowed from the source when evaporating SiO will acquire a coating of SiO(2).

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