Magnetoresistive random access memory (MRAM) cell having a diode with asymmetrical characteristics

摘要

In a magnetoresistive random access memory (MRAM), a magnetic tunnel junction (MTJ) ( 54 ) cell is stacked with an asymmetric tunnel device ( 56 ). This device, when used in a crosspoint MRAM array, improves the sensing of the state or resistance of the MTJ cells. Each MTJ cell has at least two ferromagnetic layers ( 42, 46 ) separated by an insulator ( 44 ). The asymmetric tunnel device ( 56 ) is electrically connected in series with the MTJ cell and is formed by at least two conductive layers ( 48, 52 ) separated by an insulator ( 50 ). The asymmetric tunnel device may be a MIM ( 56 ), MIMIM ( 80 ) or a MIIM ( 70 ). Asymmetry results from conducting electrons in a forward biased direction at a significantly greater rate than in a reversed biased direction. Materials chosen for the asymmetric tunnel device are selected to obtain an appropriate electron tunneling barrier shape to obtain the desired rectifying current/voltage characteristic.