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Etching of Superconductive Lead Alloy

IP.com Disclosure Number: IPCOM000043285D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Kaiser, HD: AUTHOR [+2]

Abstract

A thin film consisting of layers of lead (Pb), gold (Au) and indium (In) may be used to make superconducting interconnections between Josephson devices. The Au largely reacts with the In to form AuIn2, which acts as a grain refiner. A three-phase chemical etching procedure is disclosed to etch this multicomponent film uniformly and with good definition. The procedure consists of using: (1) an etchant which will etch indium but not lead, (2) an etchant which will etch lead but not indium, and (3) an etchant which will etch gold and AuIn2 . Typical examples are: for (1) 5% sulphuric acid, for (2) 250 gm/l ammonium acetate adjusted to pH 6.0 with glacial acetic acid, and for (3) 215 gm potassium iodide and 55 gm iodine dissolved in one liter of water.

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Etching of Superconductive Lead Alloy

A thin film consisting of layers of lead (Pb), gold (Au) and indium (In) may be used to make superconducting interconnections between Josephson devices. The Au largely reacts with the In to form AuIn2, which acts as a grain refiner. A three-phase chemical etching procedure is disclosed to etch this multicomponent film uniformly and with good definition. The procedure consists of using: (1) an etchant which will etch indium but not lead, (2) an etchant which will etch lead but not indium, and (3) an etchant which will etch gold and AuIn2 . Typical examples are: for (1) 5% sulphuric acid, for (2) 250 gm/l ammonium acetate adjusted to pH
6.0 with glacial acetic acid, and for (3) 215 gm potassium iodide and 55 gm iodine dissolved in one liter of water. The lead alloy films are dipped in the above solutions in sequence with a water rinse between steps. The ammonium acetate is more effective when used at 55-60OEC. The length of time in a particular etchant depends on the amount of that component in the film and the total thickness of the film, but is on the order of one to five minutes in each etchant.

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