Magnetic memory with structures that prevent disruptions to magnetization in sense layer

Abstract

A magnetic memory cell is disclosed having a structure that prevents disruptions to the magnetization in the sense layer of the magnetic memory cell. In one embodiment, the structure includes a high permeability magnetic film that serves as a keeper for the sense layer magnetization. The keeper structure provides a flux closure path that directs demagnetization fields away from the sense layer. In another embodiment, the structure contains a hard ferromagnetic film that applies a local magnetic field to the sense layer in the magnetic memory cell.

What is claimed is:  
     
         1 . A magnetic memory cell, comprising: 
 sense layer for storing a magnetization state that indicates a logic state of the magnetic memory cell;    structure that prevents disruptions to the magnetization state in the sense layer.    
     
     
         2 . The magnetic memory cell of  claim 1 , wherein the structure overlaps a pair of opposing edge regions of the sense layer and prevents one or more demagnetization fields from forming in the edge regions of the sense layer.  
     
     
         3 . The magnetic memory cell of  claim 1 , wherein the structure is formed from a permeable ferromagnetic material having a shape that provides flux closure for one or more demagnetization fields in the sense layer.  
     
     
         4 . The magnetic memory cell of  claim 1 , wherein the structure is formed from a permeable ferromagnetic material having an easy axis that is perpendicular to an easy axis of the sense layer.  
     
     
         5 . The magnetic memory cell of  claim 1 , wherein the structure encases a conductor that provides read and write access to the magnetic memory cell.  
     
     
         6 . The magnetic memory cell of  claim 1 , further comprising a reference layer and a tunnel barrier between the sense layer and the reference layer.  
     
     
         7 . The magnetic memory cell of  claim 6 , wherein the sense layer is adjacent to the structure.  
     
     
         8 . The magnetic memory cell of  claim 6 , wherein the reference layer is adjacent to the structure.  
     
     
         9 . The magnetic memory cell of  claim 1 , wherein the sense layer is exchange coupled to the structure.  
     
     
         10 . The magnetic memory cell of  claim 1 , wherein the structure is formed from a hard ferromagnetic material.  
     
     
         11 . The magnetic memory cell of  claim 10 , wherein the hard ferromagnetic material is magnetized perpendicular the an easy axis of the sense layer.  
     
     
         12 . The magnetic memory cell of  claim 10 , wherein the sense layer is exchange coupled to the structure.  
     
     
         13 . A magnetic memory cell, comprising: 
 sense layer for storing a magnetization that indicates a logic state of the magnetic memory cell;    means for providing flux closure for one or more demagnetization fields in the magnetic memory cell.    
     
     
         14 . The magnetic memory cell of  claim 13 , wherein the means for providing flux closure comprises a permeable ferromagnetic material having a shape that provides a path for magnetic flux transport between a pair of opposing edge regions of the sense layer.  
     
     
         15 . The magnetic memory cell of  claim 14 , wherein the permeable ferromagnetic material has an easy axis that is perpendicular to an easy axis of the sense layer.  
     
     
         16 . A method for forming a magnetic memory with a set of structures, comprising the steps of: 
 forming a set of trenches in a substrate;    depositing a layer of magnetic material for the structures so that the magnetic material coats horizontal and vertical surfaces of the trenches and the substrate;    depositing a layer of conductor material on the layer of magnetic material to fill the trenches;    polishing the layer of conductor material and the layer of magnetic material to expose an upper surface of the substrate.    
     
     
         17 . The method of  claim 16 , wherein the conductor material is copper.  
     
     
         18 . The method of  claim 16 , wherein the step of polishing comprises the step of polishing using a chem-mechanical process.  
     
     
         19 . The method of  claim 16 , wherein the step of forming a set of trenches comprises the step of forming a set of trenches using reactive ion etching.  
     
     
         20 . The method of  claim 16 , further comprising the steps of: 
 depositing a material for a sense layer in each of a set of magnetic memory cells in the magnetic memory;    depositing a material for a tunnel barrier in each of the magnetic memory cells;    depositing a material for a reference layer in each of the magnetic memory cells.    
     
     
         21 . The method of  claim 16 , wherein the material for the sense layer is deposited before the materials for the tunnel barrier and reference layers.  
     
     
         22 . The method of  claim 21 , wherein the material for the reference layer is deposited before the materials for the tunnel barrier and sense layers.