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MRAM with Reference Cells Stabilized by Magnetic Reservoirs

IP.com Disclosure Number: IPCOM000125705D
Original Publication Date: 2005-Jul-10
Included in the Prior Art Database: 2005-Jul-10
Document File: 1 page(s) / 155K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Reference cells are susceptible to being overwritten when array cells are written, due to half select problems. This leads to failing of many array cells. Thus there is a need to stabilize reference cells.

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MRAM with Reference Cells Stabilized by Magnetic Reservoirs

Idea: Dr. Daniel Braun, FR-Paris; Dr. Dietmar Gogl, US-Williston/Essex Junction

Reference cells are susceptible to being overwritten when array cells are written, due to half select problems. This leads to failing of many array cells. Thus there is a need to stabilize reference cells.

In the new concept, the reference cells are stabilized with magnetic reservoirs. These are ferromagnetic structures, which make a stray field, which tends to align the reference cells in a preferred direction (corresponding to 0 or 1). The price to pay is higher switching currents for the reference cells, but this leads to substantially enhanced stability of the reference cells when the memory is operated. Ideally, and in particular if the Reference BLs can be contacted externally such that a much higher current can be driven through them, this idea makes it possible to have the reference cells written once for all in the production/testing process, and the user has never to write them again. In preferred embodiment, the reservoirs are vertical structures attached directly to the reference BLs. This makes it possible to have reference cells, which are completely identical in their resistive behavior (including temperature and process sensitives) to regular array cells. Only the magnetic switching behavior is changed.

Fig. 1: Reference cells stabilized by magnetic reservoirs

© SIEMENS AG 2005 file: ifx_2005J51186.doc page:...