Patent ID: 7285836
Filing Date: 2007-10-23
Classification: G11C,H01L

Abstract:
1. A magnetic random access memory (MRAM) comprising: a substrate; a plurality of first and second electrically conductive lines on the substrate, the second lines being located between the substrate and the first lines with the first lines overlapping the second lines and spaced from the second lines in a generally perpendicular direction from the substrate to define a plurality of intersection regions, the first line and second line at each intersection region being generally orthogonal; a plurality of memory stacks, each memory stack located in an intersection region and comprising (a) a first memory cell having a pinned ferromagnetic layer, a free ferromagnetic layer with an in-plane easy axis of magnetization aligned generally parallel with one of said first and second lines, and a nonmagnetic coupling layer between the pinned and free layers, (b) a second memory cell having a pinned ferromagnetic layer, a free ferromagnetic layer with an in-plane easy axis of magnetization aligned substantially parallel with the easy axis of magnetization of the free layer of the first cell, and a nonmagnetic coupling layer between the pinned and free layers, and (c) a nonmagnetic separation layer between said two memory cells; a first biasing layer magnetically coupled to the free layer of the first cell in each stack and having an in-plane magnetization direction substantially orthogonal to the easy axis of the free layer of the first cell for applying a hard-axis biasing field to the free layer of the first cell; and a second biasing layer magnetically coupled to the free layer of the second cell in each stack and having an in-plane magnetization direction substantially orthogonal to the easy axis of the free layer of the second cell for applying a hard-axis biasing field to the free layer of the second cell, the hard-axis biasing field applied to the free layer of the second cell being substantially antiparallel to the hard-axis biasing field applied to the free layer of the first cell.