Magnetic random access memory with field compensating layer and multi-level cell

Abstract

A spin toque transfer 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 spacer layer is formed on top of the free layer and a fixed layer is formed on top of the spacer 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 fixed 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 toque transfer magnetic random access memory (STTMRAM) element configured to store a state when electrical current is applied thereto comprising:
 a magnetic pinned layer;   a magnetic reference layer;   a magnetic free layer;   a magnetic fixed layer;   a junction layer formed between the reference layer and the free layer;   a spacer layer formed between the free layer and the fixed layer;   wherein the free layer magnetization being switchable by an electric current relative to the reference layer and operable to produce a resistance change across the element; and   wherein the free layer further having associated therewith a coercivity field that is smaller when the magnetization directions of fixed layer and reference layer are perpendicular to a film plane and substantially anti-parallel.   
     
     
         2 . The STTMRAM element, as recited in  claim 1 , wherein the coupling layer is made of ruthenium (Ru) or copper (Cu). 
     
     
         3 . The STTMRAM element, as recited in  claim 1 , wherein the coupling layer is made of non-magnetic material and provides anti-ferromagnetic exchange coupling between the pinned layer and the reference layer. 
     
     
         4 . The STTMRAM element, as recited in  claim 1 , wherein the spacer layer is a metal layer comprises one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         5 . The STTMRAM element, as recited in  claim 1 , wherein the spacer layer is a non-metal layer. 
     
     
         6 . The STTMRAM element, as recited in  claim 5 , wherein the spacer layer comprises an oxide layer comprising one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         7 . The STTMRAM element, as recited in  claim 5 , wherein the spacer layer comprises a nitride layer comprising one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         8 . The STTMRAM element, as recited in  claim 5 , wherein the spacer layer comprises a carbide layer comprising one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         9 . The STTMRAM element, as recited in  claim 1 , wherein the spacer layer comprises a metal layer comprising one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn) . . . , and wherein the spacer layer further comprises a non-metal layer composed of an oxide, a nitride or a carbide comprising the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         10 . The STTMRAM element, as recited in  claim 1 , wherein either one of the pinned layer, the fixed layer, the free layer and the reference layer is made of a single layer and made from an alloy of the following materials: iron, nickel, cobalt, platinum, palladium, chromium, boron, neodymium or terbium. 
     
     
         11 . The STTMRAM element, as recited in  claim 1 , wherein the in-plane magnetic field is along a radial direction. 
     
     
         12 . The STTMRAM element, as recited in  claim 1 , wherein the in-plane magnetic field is at the edge of the free layer. 
     
     
         13 . The STTMRAM element, as recited in  claim 1 , wherein the in-plane magnetic field is larger than 1 kilo Oersted (kOe). 
     
     
         14 . The STTMRAM element, as recited in  claim 1 , wherein either one of the pinned layer, the fixed layer, the free layer and the reference layer is made of multiple layers, the multiple layers being interleaved. 
     
     
         15 . The STTMRAM element, as recited in  claim 14 , wherein at least one of the multiple layers comprises one or more of the materials: cobolt (Co), iron (Fe), or boron (B), and at least another one of the multiple layers comprises one or more of the materials: palladium (Pd), platinum (Pt) or nickel (Ni). 
     
     
         16 . The STTMRAM element, as recited in  claim 1 , wherein the free layer having associated therewith an in-plane magnetic field component generated by the fixed layer, the pinned layer, and the reference layer, the free layer coercivity field being smaller in the presence of the in-plane magnetic field. 
     
     
         17 . A spin toque transfer magnetic random access memory (STTMRAM) element configured to store a state when electrical current is applied thereto comprising:
 a magnetic reference layer;   a magnetic free layer, the magnetic free layer having a magnetization;   a magnetic fixed layer;   a junction layer formed between the magnetic reference layer and the magnetic free layer;   a spacer layer formed between the magnetic free layer and the magnetic fixed layer,   wherein the magnetization of the magnetic free layer being switchable by an electric current relative to that of the magnetic reference layer and operable to produce a resistance change across the STTMRAM element,   further wherein the magnetic free layer further having associated therewith a coercivity field that is smaller when the magnetization directions of magnetic fixed layer and the magnetic reference layer are perpendicular to a film plane and substantially anti-parallel.   
     
     
         18 . The STTMRAM element, as recited in  claim 17 , wherein the spacer layer is a metal layer comprises one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         19 . The STTMRAM element, as recited in  claim 17 , wherein the spacer layer is a non-metal layer. 
     
     
         20 . The STTMRAM element, as recited in  claim 19 , wherein the spacer layer comprises an oxide layer one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         21 . The STTMRAM element, as recited in  claim 19 , wherein the spacer layer comprises a nitride layer including one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         22 . The STTMRAM element, as recited in  claim 19 , wherein the spacer layer comprises a carbide layer including one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         23 . The STTMRAM element, as recited in  claim 19 , wherein the spacer layer is a metal layer composed of one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn) . . . , and wherein the spacer layer is further made of a non-metal layer composed of oxide, nitride, or carbide of one or more of the materials: magnesium (Mg), aluminum (Al), titanium (Ti), tantalum (Ta), silicon (Si), ruthenium (Ru), zirconium (Zr), hafnium (Hf), or zinc (Zn). 
     
     
         24 . The STTMRAM element, as recited in  claim 17 , wherein any one of the pinned layer, the fixed layer, and the free layer is made of a single layer and made from an alloy of the following materials: iron, nickel, cobalt, platinum, palladium, chromium, boron, neodymium or terbium. 
     
     
         25 . The STTMRAM element, as recited in  claim 17 , wherein the in-plane magnetic field is along a radial direction. 
     
     
         26 . The STTMRAM element, as recited in  claim 17 , wherein the in-plane magnetic field is at the edge of the free layer. 
     
     
         27 . The STTMRAM element, as recited in  claim 17 , wherein the in-plane magnetic field is larger than 1 kilo Oersted (kOe). 
     
     
         28 . The STTMRAM element, as recited in  claim 17 , wherein any one of the pinned layer, the fixed layer, the free layer and the reference layer is made of multiple layers that are interleaved. 
     
     
         29 . The STTMRAM element, as recited in  claim 28 , wherein at least one of the multiple layers comprises one or more of the materials: cobolt (Co), iron (Fe), or boron (B), and at least another one of the multiple layers comprises one or more of the materials: palladium (Pd), platinum (Pt) or nickel (Ni). 
     
     
         30 . The STTMRAM element, as recited in  claim 17 , wherein the free layer having associated therewith an in-plane magnetic field component generated by the fixed layer and the pinned layer, the free layer coercivity field being smaller in the presence of the in-plane magnetic field. 
     
     
         31 . The STTMRAM element, as recited in  claim 17 , wherein the in-plane magnetic field component is generated by magnetization directions of magnetic fixed layer and the magnetic reference layer being perpendicular to a film plane and substantially anti-parallel. 
     
     
         32 . A spin toque transfer magnetic random access memory (STTMRAM) element configured to store a state when electrical current is applied thereto comprising:
 a magnetic first reference layer;   a magnetic first free layer;   a first junction layer formed between the magnetic first reference layer and the magnetic first free layer;   a magnetic second reference layer;   a magnetic second free layer;   a second junction layer formed between the magnetic second reference layer and the magnetic second free layer;   a magnetic fixed layer;   a first spacer layer formed between the magnetic first free layer and the magnetic fixed layer; and   a second spacer layer formed between the magnetic second free layer and the magnetic fixed layer,   wherein the magnetization directions of the magnetic fixed layer is perpendicular to a film plane and substantially anti-parallel to the magnetizations of the magnetic first reference layer and the magnetic second reference layer.   
     
     
         33 . The STTMRAM element, as recited in  claim 32 , wherein the magnetic first free layer and the magnetic second free layer each having associated therewith an in-plane magnetic field component generated by the magnetic fixed layer, the magnetic first reference layer, and the magnetic second reference layer, and each of the magnetic first free layer and the magnetic second free layer further having associated therewith a coercivity field that is smaller in the presence of the in-plane magnetic field. 
     
     
         34 . The STTMRAM element, as recited in  claim 32 , wherein the magnetic first free layer and magnetic second free layer magnetizations are perpendicular to a film plane. 
     
     
         35 . The STTMRAM element, as recited in  claim 32 , wherein the magnetic first free layer and the magnetic second free layer magnetizations are individually switchable by electric current at different current values. 
     
     
         36 . A method of initializing a spin toque transfer magnetic random access memory (STTMRAM) element configured to store a state when electrical current is applied thereto comprising:
 applying a magnetic field to the STTMRAM element, wherein the STTMRAM includes,
 a magnetic pinned layer; 
 a magnetic reference layer having associated therewith a magnetization; 
 a magnetic free layer; 
 a magnetic fixed layer having associated therewith a magnetization; 
 a junction layer formed between the magnetic reference layer and the magnetic free layer; 
 a spacer layer formed between the free layer and the magnetic fixed layer; and 
   removing the applied —  magnetic field thereby switching the direction of the magnetization of the magnetic reference layer from parallel to anti-parallel relative to the magnetization direction of the fixed layer,   wherein the magnetic free layer magnetization being switchable by an electric current relative to the magnetic reference layer and producing a resistance change across the element,   wherein the magnetic free layer further having associated therewith a coercivity field that is smaller when the directions of magnetization of the magnetic fixed layer and the magnetic reference layer are perpendicular to film plane and substantially anti-parallel.   
     
     
         37 . A method of initializing a spin toque transfer magnetic random access memory (STTMRAM) element configured to store a state when electrical current is applied thereto comprising:
 a magnetic reference layer;   a magnetic free layer;   a magnetic fixed layer;   a junction layer formed between the magnetic reference layer and the magnetic free layer;   a spacer layer formed between the magnetic free layer and the magnetic fixed layer;   the magnetic free layer having a switchable perpendicular magnetic component;   applying a magnetic first magnetic field to magnetize each of the magnetic free layer, the magnetic reference layer, and the magnetic fixed layer in the same first perpendicular direction;   applying a second magnetic field having a lower strength than that of the first magnetic field and in a second perpendicular direction opposite to that of the first magnetic field to magnetize one of the magnetic reference layer and the magnetic fixed layer to the second perpendicular direction,   wherein the magnetic free layer further having associated therewith a coercivity field that is smaller when the magnetization directions of the magnetic fixed layer and the magnetic reference layer are perpendicular to a film plane and substantially anti-parallel.   
     
     
         38 . A method of initializing a spin toque transfer magnetic random access memory (STTMRAM) element configured to store a state when electrical current is applied thereto comprising:
 a magnetic first reference layer;   a magnetic first free layer;   a first junction layer formed between first reference layer and first free layer;   a magnetic second reference layer;   a magnetic second free layer;   a second junction layer formed between second reference layer and second free layer;   a magnetic fixed layer;   a first spacer layer formed between first free layer and fixed layer; and   a second spacer layer formed between second free layer and fixed layer,   wherein the STTMRAM element is operable to:
 receive a first magnetic field to magnetize each of the magnetic first and second free layers, the magnetic reference layers, and the magnetic fixed layer in a same first perpendicular direction; 
 receive a second magnetic field having a lower strength than that of the first magnetic field and in a second perpendicular direction opposite to that of the first magnetic field thereby causing the magnetization of the magnetic fixed layer being anti-parallel to the magnetizations of the magnetic reference layers, 
   wherein the magnetic first free layer and the magnetic second free layer each having associated therewith a coercivity field that is smaller when the magnetization directions of the magnetic fixed layer is perpendicular to a film plane and substantially anti-parallel to the magnetizations of the magnetic first reference layer and second the magnetic reference layer.