Perpendicular sttmram device with balanced reference layer

Abstract

A spin transfer torque magnetic random access memory (STTMRAM) element comprises a reference layer, which can be a single layer structure or a synthetic multi-layer structure, formed on a substrate, with a fixed perpendicular magnetic component. A junction layer is formed on top of the reference layer and a free layer is formed on top of the junction layer with a perpendicular magnetic orientation, at substantially its center of the free layer and switchable. A tuning layer is formed on top of the free layer and a fixed layer is formed on top of the tuning layer, the fixed layer has a fixed perpendicular magnetic component opposite to that of the reference layer. The magnetic orientation of the free layer switches relative to that of the reference layer. The perpendicular magnetic components of the fixed layer and the reference layer substantially cancel each other and the free layer has an in-plane edge magnetization field.

What is claimed is: 
     
         1 . A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
 a magnetic pinned layer having a first fixed magnetization direction substantially perpendicular to a layer plane thereof;   a magnetic free layer separated from said magnetic pinned layer by a tuning layer and having a variable magnetization direction substantially perpendicular to a layer plane thereof; and   a magnetic reference layer separated from said magnetic free layer by an insulating tunnel junction layer and having a second fixed magnetization direction substantially opposite to said first fixed magnetization direction provided in said magnetic pinned layer,   wherein said tuning layer comprises at least one insulating layer and at least one conductive layer.   
     
     
         2 . The STTMRAM element of  claim 1 , wherein said at least one insulating layer is made of magnesium oxide, aluminum oxide, or silicon oxide. 
     
     
         3 . The STTMRAM element of  claim 1 , wherein said at least one conductive layer is made of ruthenium, tantalum, copper, silver, or gold. 
     
     
         4 . The STTMRAM element of  claim 1 , wherein said magnetic pinned layer comprises a multilayer structure formed by interleaving layers of a first material with layers of a second material, at least one of said first and second materials being magnetic. 
     
     
         5 . The STTMRAM element of  claim 4 , wherein said first material is made of cobalt, iron, or any combination thereof, said second material is made of platinum, palladium, nickel, or any combination thereof. 
     
     
         6 . The STTMRAM element of  claim 1 , wherein said magnetic free layer comprises cobalt and iron. 
     
     
         7 . The STTMRAM element of  claim 1 , wherein said insulating tunnel junction layer comprises magnesium oxide. 
     
     
         8 . The STTMRAM element of  claim 1 , wherein said magnetic reference layer comprises cobalt and iron. 
     
     
         9 . A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
 a magnetic pinned layer having a first fixed magnetization direction substantially perpendicular to a layer plane thereof;   a magnetic free layer separated from said magnetic pinned layer by a tuning layer and having a variable magnetization direction substantially perpendicular to a layer plane thereof;   a first magnetic reference layer separated from said magnetic free layer by an insulating tunnel junction layer and having a second fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first fixed magnetization direction; and   a second magnetic reference layer separated from said first magnetic reference layer by a coupling layer and having said second fixed magnetization direction,   wherein said first magnetic reference layer further includes at least one interface layer formed adjacent to said insulating tunnel junction layer or said coupling layer or both of said layers.   
     
     
         10 . The STTMRAM element of  claim 9 , wherein said first magnetic reference layer includes an interface layer made of Fe or CoFe formed adjacent to said insulating tunnel junction layer. 
     
     
         11 . The STTMRAM element of  claim 9 , wherein said first magnetic reference layer includes an interface layer made of Fe or CoFe formed adjacent to said coupling layer. 
     
     
         12 . The STTMRAM element of  claim 9 , wherein said magnetic pinned layer comprises a multilayer structure formed by interleaving layers of a first material with layers of a second material, said first material being made of cobalt and second material being made of platinum, palladium, or nickel. 
     
     
         13 . The STTMRAM element of  claim 9 , wherein said tuning layer is non-magnetic. 
     
     
         14 . The STTMRAM element of  claim 9 , wherein said tuning layer comprises an insulating layer and at least one conductive layer. 
     
     
         15 . The STTMRAM element of  claim 9 , wherein each of said magnetic free layer and said first magnetic reference layer comprises cobalt and iron. 
     
     
         16 . The STTMRAM element of  claim 9 , wherein said insulating tunnel junction layer comprises magnesium oxide 
     
     
         17 . The STTMRAM element of  claim 9 , wherein said second magnetic reference layer comprises a multilayer structure formed by interleaving layers of a first material with layers of a second material, at least one of said first and second materials being magnetic. 
     
     
         18 . The STTMRAM element of  claim 17 , wherein said first material is made of cobalt, iron, or any combination thereof, said second material is made of platinum, palladium, nickel, or any combination thereof. 
     
     
         19 . A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
 a magnetic pinned layer having a first fixed magnetization direction substantially perpendicular to a layer plane thereof;   a magnetic free layer separated from said magnetic pinned layer by a tuning layer and having a variable magnetization direction substantially perpendicular to a layer plane thereof;   a first magnetic reference layer separated from said magnetic free layer by an insulating tunnel junction layer and having a second fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first fixed magnetization direction; and   a second magnetic reference layer separated from said first magnetic reference layer by a coupling layer and having said second fixed magnetization direction,   wherein said second magnetic reference layer has a different lattice structure from said insulating tunnel junction layer.   
     
     
         20 . The STTMRAM element of  claim 19 , wherein said second magnetic reference layer has a face centered cubic (FCC) lattice structure.