Magnetic memory array using magnetic tunnel junction devices in the memory cells

A magnetic memory array comprising:

• a substrate;
• a first set of parallel electrically conductive lines formed on the substrate;
• a second set of parallel electrically conductive lines formed on the substrate generally perpendicular to the first set of lines and overlapping the first set of lines, the second set of lines being spaced from the first set of lines in a direction generally perpendicular to the substrate surface to define a plurality of intersection regions;
• a plurality of memory cells, each memory cell being located in an intersection region between the lines and comprising a diode and a magnetic tunnel junction electrically connected in series with the diode, each of the magnetic tunnel junctions comprising first and second ferromagnetic layers separated by an insulating tunnel barrier, one of the ferromagnetic layers having a magnetization direction that is generally fixed in a plane parallel to the substrate surface and the other of the ferromagnetic layers having a magnetization direction capable of orientation parallel or antiparallel to the magnetization direction of the first ferromagnetic layer;
• electrical circuitry coupled to the first and second sets of lines for passing write current through the lines to generate magnetic fields in the vicinity of the second ferromagnetic layers in the magnetic tunnel junctions to reorient the magnetizations of the second ferromagnetic layers and thereby alter the electrical resistance across the magnetic tunnel junctions in a direction perpendicular to the substrate, the circuitry providing a reverse bias voltage to the diodes when current is passing through the lines, whereby no current flows through the magnetic tunnel junctions in a direction perpendicular to the substrate when write current is passing through the lines.

A magnetic memory cell for use in a nonvolatile magnetic memory array that is connected to read/write circuitry for reading and writing to the memory cells in the array, the memory cell comprising:

• a diode having a first electrical lead for connection to the read/write circuitry;
• a fixed ferromagnetic layer electrically connected to the diode and having a magnetization in the plane of said fixed ferromagnetic layer that is fixed from rotation when exposed to a magnetic field less than a predetermined field strength;
• an insulating tunnel barrier layer in contact with the fixed ferromagnetic layer;
• a free ferromagnetic layer in contact with the tunnel barrier layer and having a magnetization free to rotate in the plane of said free ferromagnetic layer between directions parallel and antiparallel to the magnetization of the fixed ferromagnetic layer when exposed to a magnetic field less than said predetermined field strength, the free ferromagnetic having a second electrical lead for connection to the read/write circuitry;
• and
• wherein the diode, the fixed ferromagnetic layer, the tunnel barrier layer and the free ferromagnetic layer are formed as a vertical stack oriented generally perpendicular to the plane of the ferromagnetic layers with the first electrical lead being at the bottom of the stack and the second electrical lead being at the top of the stack;
• whereby during a write operation when write current from the read/write circuitry passes generally horizontally through the first and second electrical leads, the diode prevents current flow through the tunnel barrier layer and the magnetic field from the write current rotates the magnetization of the free ferromagnetic layer, and during a read operation when the voltage between the first and second electrical leads is greater than the diode threshold voltage, read current flows through the tunnel barrier layer in a direction generally perpendicular to said ferromagnetic layers, the electrical resistance to said read current flow being determined by the magnetization orientation of said free ferromagnetic layer.