Spin-transfer torque magnetic random access memory with perpendicular magnetic anisotropy multilayers
View Patent ↗A spin transfer torque magnetic random access memory (STTMRAM) element includes a composite fixed layer formed on top of a substrate and a tunnel layer formed upon the fixed layer and a composite free layer formed upon the tunnel barrier layer. The magnetization direction of each of the composite free layer and fixed layer being substantially perpendicular to the plane of the substrate. The composite layers are made of multiple repeats of a bi-layer unit which consists of a non-magnetic insulating layer and magnetic layer with thicknesses adjusted in a range that makes the magnetization having a preferred direction perpendicular to film plane.
1. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a composite fixed layer formed on top of a substrate, the composite fixed layer having a fixed magnetization direction substantially perpendicular to a plane of the substrate;
a tunnel barrier layer formed upon the fixed layer; and
a composite free layer formed upon the tunnel barrier layer, the composite free layer having a switchable magnetization direction substantially perpendicular to the plane of the substrate,
wherein each of the composite free and fixed layers is made of one or more repeats of a bilayer unit that comprises an insulating layer and a magnetic layer, the magnetic layer of the bilayer unit includes two magnetic sublayers separated by a non-magnetic boron absorption layer.
2. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic boron absorption layer is a single element layer, and made of a material comprising: Ta, Ti, or Ru.
3. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic boron absorption layer is a composite material comprising one or more of the following: Ta, Ti, or Ru, in addition to one or more of the following materials: B, Co, Fe, or Ni.
4. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic boron absorption layer is a composite material comprising one or more of the following: Ta, Ti, Ru, B, Co, Fe, or Ni.
5. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a composite fixed layer formed on top of a substrate, the composite fixed layer having a fixed magnetization direction substantially perpendicular to a plane of the substrate;
a tunnel barrier layer formed upon the fixed layer; and
a composite free layer formed upon the tunnel barrier layer, the composite free layer having a switchable magnetization direction substantially perpendicular to the plane of the substrate,
wherein each of the composite free and fixed layers is made of one or more repeats of a bilayer unit that comprises an insulating layer and a magnetic layer, the magnetic layer of the bilayer unit has a magnetic multilayer structure that includes a thin boron (B) absorption nonmagnetic metal layer.
6. The STTMRAM element, as recited in claim 5 , wherein the thin boron (B) absorption nonmagnetic metal layer has a thickness of 0.3 to 1.0 nano meters (nm).
7. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a composite fixed layer formed on top of a substrate, the composite fixed layer having a fixed magnetization direction substantially perpendicular to a plane of the substrate;
a tunnel barrier layer formed upon the fixed layer; and
a composite free layer formed upon the tunnel barrier layer, the composite free layer having a switchable magnetization direction substantially perpendicular to the plane of the substrate,
wherein each of the composite free and fixed layers is made of one or more repeats of a bilayer unit that comprises an insulating layer and a magnetic layer, one of magnetic layers of the one or more repeats of the bilayer unit is positioned adjacent to and directly contacting the tunnel barrier layer, the magnetic layer of the bilayer unit that is positioned adjacent to and directly contacting the tunnel barrier layer is made of Fe—ZY alloy having less than 15 at % of Z, where Z is one or more of the following materials: boron (B), phosphorous (P), carbon (C), nitride (N) and Y represents any of the materials: tantalum (Ta), titanium (Ti), niobium (Nb), zirconium (Zr), tungsten (W), silicon (Si), copper (Cu), silver (Ag), aluminum (Al), chromium (Cr), tin (Sn), lead (Pb), antimony (Sb), hafnium (Hf) and bismuth (Bi), molybdenum (Mo), or rhodium (Rh).
8. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a composite fixed layer formed on top of a substrate, the composite fixed layer having a fixed magnetization direction substantially perpendicular to a plane of the substrate;
a tunnel barrier layer formed upon the fixed layer; and
a composite free layer formed upon the tunnel barrier layer, the composite free layer having a switchable magnetization direction substantially perpendicular to the plane of the substrate,
wherein each of the composite free and fixed layers is made of one or more repeats of a bilayer unit that comprises an insulating layer and a magnetic layer, the composite fixed layer comprises an anti-ferromagnetic (AFM) layer, a first composite magnetic layer formed on top of the AFM layer, a spacer layer formed on top of the first composite magnetic layer, and a second composite magnetic layer formed on top of the spacer layer.
9. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a composite fixed layer formed on top of a substrate, the composite fixed layer having a fixed magnetization direction substantially perpendicular to a plane of the substrate;
a tunnel barrier layer formed upon the fixed layer; and
a composite free layer formed upon the tunnel barrier layer, the composite free layer having a switchable magnetization direction substantially perpendicular to the plane of the substrate,
wherein each of the composite free and fixed layers is made of one or more repeats of a bilayer unit that comprises an insulating layer and a magnetic layer, the composite free layer comprises a first composite magnetic layer, a spacer layer formed on top of the first composite magnetic layer, and a second composite magnetic layer formed on top of the spacer layer.
10. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a composite fixed layer formed on top of a substrate, the composite fixed layer having a fixed magnetization direction substantially perpendicular to a plane of the substrate;
a tunnel barrier layer formed upon the fixed layer; and
a composite free layer formed upon the tunnel barrier layer, the composite free layer having a switchable magnetization direction substantially perpendicular to the plane of the substrate,
wherein each of the composite free and fixed layers is made of one or more repeats of a bilayer unit that comprises an insulating layer and a magnetic layer, the composite fixed layer has an additional top spacer layer and a magnetic layer with magnetization having in-plane preferred direction.