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Funnel Shaped Josephson Edge Junctions

IP.com Disclosure Number: IPCOM000044932D
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Deutsch, U: AUTHOR [+3]

Abstract

In edge-junction technology, variations of the Josephson current density j(m) across chip and wafer are substantially larger than those observed in planar technology. The current density depends strongly on the orientation of the edge on the wafer. This problem can be significantly reduced when using non-linear, particularly funnel-shaped edge-junctions rather than linear junctions.

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Funnel Shaped Josephson Edge Junctions

In edge-junction technology, variations of the Josephson current density j(m) across chip and wafer are substantially larger than those observed in planar technology. The current density depends strongly on the orientation of the edge on the wafer. This problem can be significantly reduced when using non-linear, particularly funnel-shaped edge-junctions rather than linear junctions.

The current density j(m) depends on the oxide layer thickness and thus on the oxidation rate which, in turn, shows a strong dependence on the angle of incidence of the ions during the oxidation process. Due to plasma perturbation caused by the presence of the wafer on the cathode, this angle varies across the wafer (Fig. 1) and leads to systematic variations of the current density. This effect can be compensated by using non-linear edge-junctions where the angle of incidence varies over the length of the junction. Maximum compensation can be achieved with funnel-shaped junctions (Fig. 2) for which the total junction current i(m) is given by the (j(m) x area) integral along the funnel surface. Since this surface is radially symmetric, any orientation effect in j(m) will not effect i(m), or to a drastically reduced extent. Any remaining i(m) variation can be reduced by planetary wafer rotation.

Funnel-shaped junctions can be made following the standard linear edge- junction process steps except for junction area definition. For both types of juncti...