Spin orbit torque magnetoresistive random access memory containing shielding element and method of making thereof
View Patent ↗A Magnetoresistive Random Access Memory (MRAM) assembly includes a first ferromagnetic shielding component, a second ferromagnetic shielding component, a plurality of MRAM cells located between the first and second ferromagnetic shielding components, a plurality of bit lines located between the first and second ferromagnetic shielding components, each bit line coupled to at least one of the plurality of MRAM cells, a plurality of word lines located between the first and second ferromagnetic shielding components, each word line coupled to at least one of the plurality of MRAM cells, a ferromagnetic yoke electrically connecting the first and second ferromagnetic shielding components, and located in an area of the assembly substantially free of the MRAM cells, bit lines, and word lines, and an insulator surrounding the magnetic yoke.
1. A Magnetoresistive Random Access Memory (MRAM) assembly, comprising:
a first ferromagnetic shielding component;
a second ferromagnetic shielding component;
a plurality of MRAM cells located between the first and second ferromagnetic shielding components;
a plurality of bit lines located between the first and second ferromagnetic shielding components, each bit line coupled to at least one of the plurality of MRAM cells;
a plurality of word lines located between the first and second ferromagnetic shielding components, each word line coupled to at least one of the plurality of MRAM cells;
a ferromagnetic yoke electrically connecting the first and second ferromagnetic shielding components, and located in an area of the assembly free of the MRAM cells, bit lines, and word lines; and
an insulator surrounding the magnetic yoke.
2. The MRAM assembly of claim 1 , further comprising:
a first insulating layer located between the first ferromagnetic shielding component and the word lines such that the word lines are not electrically connected to the first and ferromagnetic shielding components; and
a second insulating layer located between the second ferromagnetic shielding component and the bit lines such that the bit lines are not electrically connected to the first and second ferromagnetic shielding components.
3. The MRAM assembly of claim 2 , wherein:
the MRAM assembly is located on a substrate; and
a surface of the first ferromagnetic shielding component is co-planar with a surface of the substrate to within ±5°; and
a surface of the second ferromagnetic shielding component is co-planar with a surface of the substrate to within ±5°.
4. The MRAM assembly of claim 3 , wherein the magnetic yoke and the first and second ferromagnetic shielding components comprise a sheet of the same soft ferromagnetic material that overlies or underlies the plurality of MRAM cells.
5. The MRAM assembly of claim 1 , wherein the first ferromagnetic shielding component comprises ferromagnetic material that retains at least 50% of its room temperature magnetization after exposure to 400° C. for more than one minute.
6. The MRAM assembly of claim 1 , wherein the magnetic yoke includes an alloy of iron with at least one of Ni, Si, Al, Co, and Mn.
7. The MRAM assembly of claim 1 , wherein the magnetic yoke includes at least one of a nickel alloy, iron alloy, and sendust.
8. The MRAM assembly of claim 2 , wherein:
the insulator electrically isolates the ferromagnetic yoke from the bit lines and the word lines;
the first insulating layer electrically isolates the first shielding component from the word lines; and
the second insulating layer electrically isolates the second shielding component from the bit lines.
9. The MRAM assembly of claim 2 , wherein the insulator and the first and second insulating layers each comprise the same insulating material comprising at least one of Al 2 O 3 , SiO 2 , and SiN, or a combination thereof.
10. The MRAM assembly of claim 1 , wherein the plurality of MRAM cells comprises at least one Spin Orbit Torque (SOT) MRAM device.
11. A method of operating the MRAM assembly of claim 1 , comprising storing data in the MRAM cells, and exposing the assembly to magnetic fields external to the assembly, wherein data storage in the MRAM cells is unaffected by a presence of the magnetic fields external to the assembly.
12. A Spin Orbit Torque (SOT) Magnetoresistive Random Access Memory (MRAM) device, comprising:
a first ferromagnetic shielding layer located over a substrate;
a second ferromagnetic shielding layer located over the first ferromagnetic shielding layer;
a word line located between the first and second ferromagnetic shielding layers;
a bit line located between the first and second ferromagnetic shielding layers;
a SOT MRAM cell located between and coupled to the word line and the bit line; and
a ferromagnetic yoke electrically connecting the first and second ferromagnetic shielding layers.
13. The SOT MRAM device of claim 12 , wherein the ferromagnetic yoke is located over the substrate and laterally spaced from the SOT MRAM cell such that a horizontal plane parallel to a top surface of the substrate intersects both the ferromagnetic yoke and the SOT MRAM cell.
14. A method for making a Magnetoresistive Random Access Memory (MRAM) assembly, comprising:
depositing a first ferromagnetic shielding component over a substrate;
depositing a first insulating layer over the first ferromagnetic shielding component;
depositing a first conductive layer over the first insulating layer;
patterning the first conductive layer to form a first layer of bit lines or word lines, the first layer of bit lines or word lines having an opening for a magnetic yoke;
etching the first insulating layer exposed in the opening for the magnetic yoke to expose the first ferromagnetic shielding component;
depositing ferromagnetic material into the etched opening to form a ferromagnetic yoke that is coupled to the first ferromagnetic shielding component;
forming a plurality of MRAM cells on the first layer of bit lines or word lines;
depositing a second insulating layer between the MRAM cells;
depositing a second conductive layer over the MRAM cells;
patterning the second conductive layer to form a second layer of the other one of the bit lines or the word lines;
depositing a third insulating layer over the second layer of another one of bit lines or word lines; and
depositing a second ferromagnetic shielding component over the third insulating layer in electrical contact with the ferromagnetic yoke.
15. The method of claim 14 , wherein depositing the first and second ferromagnetic shielding components is by lift-off.
16. The method of claim 14 , wherein depositing the first and second ferromagnetic shielding components is by electroplating.
17. The method of claim 14 , wherein the plurality of MRAM cells comprises at least one Spin Orbit Torque (SOT) MRAM device.
18. The method of claim 14 , wherein the magnetic yoke includes an alloy of iron with at least one of Ni, Si, Al, Co, and Mn.
19. The method of claim 14 , wherein the magnetic yoke includes at least one of a nickel alloy, iron alloy, and sendust.