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Method of Defining Josephson Junction Area

IP.com Disclosure Number: IPCOM000048964D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Kaiser, HD: AUTHOR [+3]

Abstract

This article describes an improved method for forming the junction area of Josephson devices. The method features the use of a photoresist mask and a reactive ion etch to form holes in a blanket-deposited layer of SiO which overlays the Josephson base metal. Holes so made permit a more precise definition of the Josephson junction area.

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Method of Defining Josephson Junction Area

This article describes an improved method for forming the junction area of Josephson devices. The method features the use of a photoresist mask and a reactive ion etch to form holes in a blanket-deposited layer of SiO which overlays the Josephson base metal. Holes so made permit a more precise definition of the Josephson junction area.

Due to its favorable chemical and mechanical properties at low temperature, SiO is the preferred insulating material for separating the two superconducting metals used to form a Josephson device. Unfortunately, however, SiO is not readily etched and therefore workers have encountered difficulties in making the openings in the SiO necessary to permit joining of the Josephson metals to form the device junction. To avoid the SiO etching difficulties. workers in the past have pattern deposited SiO at the metal substrate to form the Josephson junction area openings. That is to say, a lift-off mask has been used to define the holes for the junction in the SiO layer during deposition.

The prior method, however. suffers from shortcomings. Particularly during deposition the SiO has been found to deposit under the "hat" profile of the lift-off mask. This gives rise to inconsistent hole cross sections. Additionally, it has been found that various types of debris remain in the hole following removal of the mask. For example, SiO under the mask edges ("hat profile") attach to the mask structure and are disrupted and litter the hole when the mask is removed.

To overcome these difficulties, t...