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Electrical Measurement of Edge Angles

IP.com Disclosure Number: IPCOM000041399D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Broom, RF: AUTHOR [+2]

Abstract

The Josephson edge junction technology for cryogenic circuits requires tight control and exact measurements of the base electrode edge angle since the junction current im0 and the junction current density j1 are highly sensitive to angle deviations. An electrical method is proposed that permits the determination of the edge angle through measurements of the current densities of edge and planar junctions simultaneously produced on a wafer. The method provides more accurate angle measurements than obtainable with optical methods.

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Electrical Measurement of Edge Angles

The Josephson edge junction technology for cryogenic circuits requires tight control and exact measurements of the base electrode edge angle since the junction current im0 and the junction current density j1 are highly sensitive to angle deviations. An electrical method is proposed that permits the determination of the edge angle through measurements of the current densities of edge and planar junctions simultaneously produced on a wafer. The method provides more accurate angle measurements than obtainable with optical methods. The method is based on the following equation that describes the relationship between the current density ratio R of simultaneously produced edge and planar Josephson junctions, and the edge angle A: j1 edge C1 R = Exp (C2(1-cosA)) (1) j1 planar sinA wherein j1 edge, j1 planar = current densities of adjacent edge and planar junctions, respectively,

produced on the same wafer. C1 = determined by the

thickness of the base electrode. C2 = determined by oxidation

process parameters (pressure, time, Vrf). A = edge angle. Initially, constants C1 and C2 are determined for the system and process parameters used for the junction barrier fabrication: current densities J1 edge and j1 planar of test wafer junctions with known base electrode thickness and edge angles are measured and equation (1) applied thereafter. Since the process parameters are reproducible with sufficient accuracy, equation (1) or a correspond...