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Semiconductor Devices Formed From Nb(3)Ge

IP.com Disclosure Number: IPCOM000083808D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Hatzakis, M: AUTHOR [+3]

Abstract

The fabrication by vapor deposition of the high Tc compound superconductor Nb(3)Ge generally requires elevated substrate temperatures (~730 degrees C), in order to obtain optimized properties. Thus, if during the deposition process (RF sputtering, for example) the substrate is maintained at such a high temperature, the highest Tc (/>approx. 20 degrees K) and best stoichiometry and structure are obtained.

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Semiconductor Devices Formed From Nb(3)Ge

The fabrication by vapor deposition of the high Tc compound superconductor Nb(3)Ge generally requires elevated substrate temperatures (~730 degrees C), in order to obtain optimized properties. Thus, if during the deposition process (RF sputtering, for example) the substrate is maintained at such a high temperature, the highest Tc (/>approx. 20 degrees K) and best stoichiometry and structure are obtained.

Experimentally, the best films are thicker than about 0.8 mu. Below 0.5 mu there is a reduced Tc. Explanations for this Tc behavior have been postulated which involve epitaxy, stoichiometry and filamentary conductive paths. However, high temperatures during fabrication and relatively thick (approx.1 mu) films are necessary for high Tc films.

These properties of Nb(3)Ge films cause several problems for device fabrication. Resist materials, either photon or electron, cannot withstand such high temperatures, which prohibits the direct use of lift-off techniques. The lift-off technique is a desirable procedure for making structures of micron and submicron size such as conductive stripes, Josephson devices such as microbridges and resistors. However, by using a negative resist technique on an already formed film (Fig. 1) the above-noted problems associated with use of Nb(3)Ge are obviated. Sputter etching can also be used satisfactorily.

For films which are relatively thick, it has been difficult previously to form micron and submicron sized structures without undercutting or destroying the thin resist layer. Illus...