Advanced MRAM Concepts

Two important goals of Magnetoresistive Random Access Memory (MRAM) development are to improve MRAM manufacturability and to extend MRAM density to 100 nm dimensions. One potential barrier to MRAM manufacturability is associated with the method of write selection in which two orthogonal currents in coincidence must write data. whereas each of the orthogonal currents alone cannot disturb the data. This "2D" selection method places constraints on uniformity of MRAM memory cells. Using a transistor per cell for write select greatly improves operating margins and lowers write currents. Attaining reasonable memory densities for this scheme depends on limiting the required write current in order to minimize the area of the select transistor. A second goal is to extend MRAM density to 100 nm dimensions. Use of a vertical GMR multilayer ring structure. where the data is stored in circumferencially oriented magnetizations, can extend the density of MRAM. Stability is projected for cells with inside diameters of less than 50nm. A second approach is to use Joule heating, in combination with magnetic field from a current, to write by exceeding the Neel point of an anti-ferromagnetic pinning layer in a pseudo-spin valve cell. Feature sizes smaller than 100 nm are projected along with decreases in required switching currents.