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Browse Prior Art Database

Smoothness Control for Josephson Edge Junctions

IP.com Disclosure Number: IPCOM000050932D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Chen, MM: AUTHOR [+4]

Abstract

Post-baking the photoresist stencil after development improves the smoothness of the niobium (Nb) edge surface which is to be the site of a Josephson junction.

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Smoothness Control for Josephson Edge Junctions

Post-baking the photoresist stencil after development improves the smoothness of the niobium (Nb) edge surface which is to be the site of a Josephson junction.

In Nb edge junction devices, the Nb base electrode is plasma etched in CF(4) + O(2) to provide the tapered edge for tunnel barrier formation. The typical etched surface exhibits a scalloped edge and rough surface. Because of this, not only the total surface area can vary from junction to junction, but also the Josephson current density, which depends on the local surface topology, may vary. These factors can contribute to a random variation in zero voltage maximum current density I(mo).

The smoothness of the Nb edge surface is improved by post-baking the photoresist stencil after development. This is done prior to plasma etching at an elevated temperature (e.g., at Approximately 150 degrees C for 10 to 30 minutes). The scalloping of the edge is eliminated and smoothness is improved using the post-bake treatment (see comparative scanning electron micrographs on the previous page), and the junction I(mo) spread is reduced.

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