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SFQ Memory Cell Structure With Magnetic Cross-Talk Compensation

IP.com Disclosure Number: IPCOM000049803D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Jaeckel, H: AUTHOR

Abstract

In Single Flux Quantum (SFQ) memories employing Josephson interferometers, magnetic cross-talk between neighboring memory cells is caused by control line currents. This cross-talk results in partial addressing of non-selected cells and reduces usable cell margins. In the proposed cell structure, the interferometsr base electrode is recessed below the interferometer inductance bridge such that the parasitic magnetic flux coupling between adjacent interferometers is cancelled.

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SFQ Memory Cell Structure With Magnetic Cross-Talk Compensation

In Single Flux Quantum (SFQ) memories employing Josephson interferometers, magnetic cross-talk between neighboring memory cells is caused by control line currents. This cross-talk results in partial addressing of non-selected cells and reduces usable cell margins. In the proposed cell structure, the interferometsr base electrode is recessed below the interferometer inductance bridge such that the parasitic magnetic flux coupling between adjacent interferometers is cancelled.

A structure embodying the concept is illustrated in Fig. 1 representing a cross-sectional view of a pair of neighboring interferometers, designated cell 1 and cell 2. Only the metal layers forming the electrodes and the control lines are shown, the insulations separating these layers being omitted. M1 is a ground plane, and M2/M2' is the base electrode common to both cells. Layers M3 and M3', respectively, represent the inductance bridges of the cell-interferometers and form, together with the underlying electrodes M2/M2', the interferometer loops. As shown in the figure, M2/M2' is recessed below layers M3 and M3'.

Currents on any of the control lines x, x', b, b', d and d' cause a parasitic magnetic flux that is coupled into the interferometer loop of the adjacent cell. The recessed M2/M2' structure results in a cancellation of the directly coupled stray flux f (dir), in that the coupling of the counteracting flux f (count) pass...