Browse Prior Art Database

High Critical Current Density Niobium Tunnel Junctions

IP.com Disclosure Number: IPCOM000106790D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Kleinsasser, AW: AUTHOR

Abstract

Disclosed is a Nb-Nb oxide-Nb tunnel junction with the highest possible critical current density. The basis is a trilayer in which the junction is formed over an entire wafer and subtractively patterned by selective anodization, ion milling, or reactive ion etching. Combined with a planarized process [1], optimized submicrometer devices can be fabricated.

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High Critical Current Density Niobium Tunnel Junctions

      Disclosed is a Nb-Nb oxide-Nb tunnel junction with the highest
possible critical current density.  The basis is a trilayer in which
the junction is formed over an entire wafer and subtractively
patterned by selective anodization, ion milling, or reactive ion
etching.  Combined with a planarized process [1], optimized
submicrometer devices can be fabricated.

      High performance electronic applications of Josephson junctions
will require high critical current densities, as large as several
times
 10 sup 5   A/cm sup 2  in some cases.  Most Josephson junctions are
currently based on trilayers of Nb, Al oxide, and Nb [2].  This
process is acceptable for current densities up to a few thousand
A/cm sup 2 , but the characteristics degrade gradually as current
density is increased.  High critical current density junctions have
been demonstrated in the past [3], however the junctions suffer from
the disadvantage of a soft counterelectrode with lower  T sub c  and
inferior mechanical properties compared with Nb.  All-Nb junctions
with Nb oxide barriers exhibit poor electrical characteristics.  The
present invention overcomes this problem.

      The disclosed process begins with the deposition of a Nb base
electrode.  The tunnel barrier is  Nb sub 2 O sub 5  formed on a Nb
carbide layer in order to avoid suboxide formation.  This carbide
layer can be formed by a plasma treatment [4]  or using an ion beam
process [5].  In contrast to the prior work, this process has no
pre...