Browse Prior Art Database

Josephson Read Only Memory

IP.com Disclosure Number: IPCOM000052452D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Braslau, N: AUTHOR [+2]

Abstract

Josephson technology read-only memory (ROM) arrays can find numerous applications, ranging from table look-up to Programmable logic arrays (PLAs). Ideally, ROM arrays are required to combine high density, high speed, high Yield, and simple personalization.

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Josephson Read Only Memory

Josephson technology read-only memory (ROM) arrays can find numerous applications, ranging from table look-up to Programmable logic arrays (PLAs). Ideally, ROM arrays are required to combine high density, high speed, high Yield, and simple personalization.

A near ideal ROM coupling element is proposed. It consists of an interferometer (junctions J1 and J2), a "dummy" junction (D), and an M2 "bridge"
(B) connected parallel to the "dummy" junction, as shown in the figure. The base electrode metal layer is M2, the counter electrode layer is M3, and the control line layer is M4. Personalization is accomplished by simply keeping the "bridge" connected for a binary "0", or removing the bridge for binary "1". The removal of the bridge is accomplished by sputter etching or by using lasers, to break and repair lines.

In the "0" ROM cell (bridge connected) current I(y) flows in the second metallization level (M2) of the interferometry (by-passing the junctions J1, J2) and through the bridge (by-passing the dummy junction). In the "1" ROM cell, however, the current flows through the interferometer junctions and then through the dummy junction. The presence of an control current switches the interferometer, indicating the presence of a "1".

The features of this ROM element are the following: - Compactness, since the I(x) control line can return over the dummy junctions without any adverse effects. - Nearly infinite discrimination between "1" and "0...