A nonvolatile magnetic random access memory (MRAM) is an array of individual magnetic memory cells. Each memory cell is a magnetic tunnel junction (MTJ) element and a diode electrically connected in series. Each MTJ is formed of a pinned ferromagnetic layer whose magnetization direction is prevented from rotating, a free ferromagnetic layer whose magnetization direction is free to rotate between states of parallel and antiparallel to the fixed magnetization of the pinned ferromagnetic layer, and an insulating tunnel barrier between and in contact with the two ferromagnetic layers. Each memory cell has a high resistance that is achieved in a very small surface area by controlling the thickness, and thus the electrical barrier height, of the tunnel barrier layer. The memory cells in the array are controlled by only two lines, and the write currents to change the magnetic state of an MTJ, by use of the write currents' inherent magnetic fields to rotate the magnetization of the free layer, do not pass through the tunnel barrier layer. All MTJ elements, diodes, and contacts are vertically arranged at the intersection regions of the two lines and between the two lines to minimize the total MRAM surface area. The power expended to read or sense the memory cell's magnetic state is reduced by the high resistance of the MTJ and by directing the sensing current through a single memory cell.

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

A nonvolatile memory array includes a substrate, a first plurality of electrically conductive traces formed on the substrate, a second plurality of electrically conductive traces formed on the substrate and overlapping the first plurality of traces at a plurality of intersection regions, and a plurality of memory cells formed on the substrate. Each memory cell is located at an intersection region between one of the first plurality of traces and one of the second plurality of traces and includes a bidirectionally conducting nonlinear resistance selection device and a magneto-resistive element electrically coupled in series with the selection device. The array is biased during a read operation by biasing a selected trace of a first plurality of electrically conductive traces at a first bias potential. All other traces of the first plurality of conductive traces are biased at a second bias potential. A selected trace of a second plurality of conductive traces is biased at a third bias potential. Lastly, all other traces of the second plurality of conductive traces are biased at the first bias potential.

Voltage biasing for magnetic ram with magnetic tunnel memory cells

A sensing circuit reads the magnetic state of individual memory cells making up a nonvolatile magnetic random access memory (MRAM) array. Each memory cell is a magnetic tunnel junction (MTJ) element and a diode electrically connected in series. Each MTJ is formed of a pinned ferromagnetic layer whose magnetization direction is prevented from rotating, a free ferromagnetic layer whose magnetization direction is free to rotate between states of parallel and antiparallel to the fixed magnetization of the pinned ferromagnetic layer, and an insulating tunnel barrier between and in contact with the two ferromagnetic layers. The memory cells in the array are controlled by only two lines, and the write currents to change the magnetic state of an MTJ, by use of the write currents' inherent magnetic fields to rotate the magnetization of the free layer, do not pass through the tunnel barrier layer. The magnetic state of a memory cell is read by reducing the voltage on one of the lines while the voltage on the other line is clamped.

Read circuit for magnetic memory array using magnetic tunnel junction devices

A word line structure, and method of manufacture therefor, for a monolithically formed magnetoresistive memory device having a magnetic field sensitive bit region In a preferred embodiment, the word line structure includes a dielectric layer having an etched cavity formed therein, wherein the cavity has a bottom surface and two spaced side surfaces A magnetic field keeper is provided adjacent to the back and/or side surfaces of the cavity A conductive word line is also provided in the cavity and adjacent to the magnetic field keeper to at least substantially fill the cavity A polishing step may be used to remove any portion of the magnetic field keeper and/or conductive word line that lie above the top surface of the dielectric layer to provide a planer top surface

Self-aligned wordline keeper and method of manufacture therefor

A multi-state magnetoresistive random access memory device having a pinned ferromagnetic region with a magnetic moment vector fixed in a preferred direction in the absence of an applied magnetic field, a non-ferromagnetic spacer layer positioned on the pinned ferromagnetic region, and a free ferromagnetic region with an anisotropy designed to provide a free magnetic moment vector within the free ferromagnetic region with N stable positions, wherein N is a whole number greater than two, positioned on the non-ferromagnetic spacer layer. The number N of stable positions can be induced by a shape anisotropy of the free ferromagnetic region wherein each N stable position has a unique resistance value.

Multi-state magnetoresistance random access cell with improved memory storage density

A magnetic thin film memory device having information recorded in a magnetic thin film thereof by the direction of magnetization, and adapted to reproduce the recorded information on the basis of the voltage generated as a result of the change of the magnetization direction due to the extraordinary Hall effect, magnetoresistance effect or the like. A magnetic thin film memory device in which a magnetic thin film is formed of ferrimagnetic substance having perpendicular magnetic anisotropy, and producing extraordinary Hall effect in the composition of RE rich and having the minimum saturation field which enables recording in a small magnetic field and is hard to be influenced by temperatures.

Ohdoi Yuzo

Papers

Magnetic thin film memory device