Magnetoresistive memory device including a high dielectric constant capping layer and methods of making the same

1. A magnetoresistive memory device comprising:

a first electrode;

a second electrode;

a magnetic tunnel junction located between the first electrode and the second electrode, the magnetic tunnel junction comprising a reference layer, a free layer, and a nonmagnetic tunnel barrier layer located between the reference layer and the free layer;

a hafnium oxide layer located between the second electrode and the free layer; and

a nonmagnetic metal dust layer located between the hafnium oxide layer and the free layer, wherein the nonmagnetic metal dust layer consists essentially of a single elemental metal selected from Ir, Pd, Mg, Pt, W, Ta, Hf, Pd, Ru, or Rh.

2. The magnetoresistive memory device of claim 1 , wherein the hafnium oxide layer is in direct contact with the free layer and increases perpendicular magnetic anisotropy of the free layer.

3. The magnetoresistive memory device of claim 1 , wherein the hafnium oxide layer consists essentially of hafnium oxide.

4. The magnetoresistive memory device of claim 1 , wherein the hafnium oxide layer consists essentially of a doped hafnium oxide material including dopants at an atomic concentration less than 3%.

5. The magnetoresistive memory device of claim 1 , wherein the hafnium oxide layer has a thickness in a range from 0.2 nm to 1 nm.

6. The magnetoresistive memory device of claim 5 , wherein the nonmagnetic tunnel barrier layer comprises magnesium oxide and has a thickness in a range from 0.5 nm to 1.5 nm.

7. The magnetoresistive memory device of claim 1 , wherein a thickness-to-dielectric constant ratio of the hafnium oxide layer is less than a thickness-to-dielectric constant ratio of the nonmagnetic tunnel barrier layer.

8. The magnetoresistive memory device of claim 1 , further comprising a synthetic antiferromagnet (SAF) structure comprising a stack of a hard ferromagnetic layer, an antiferromagnetic coupling layer, and the reference layer, the SAF structure being located between the first electrode and the nonmagnetic tunnel barrier layer.

9. The magnetoresistive memory device of claim 1 , further comprising a conductive capping layer comprising at least one non-magnetic, electrically conductive material and disposed between the hafnium oxide layer and the second electrode.

10. The magnetoresistive memory device of claim 1 , wherein the magnetoresistive memory device comprises a spin-transfer torque (STT) magnetoresistive random access memory (MRAM) cell configured to flow electrical current bidirectionally between the first electrode and the second electrode.

11. The magnetoresistive memory device of claim 10 , further comprising a control circuit configured to:

provide a positive programming voltage to the first electrode relative to the second electrode;

provide a negative programming voltage to the first electrode relative to the second electrode; and

provide a sensing voltage to the first electrode relative to the second electrode, wherein the sensing voltage has a magnitude that is less than a magnitude of the positive programming voltage and is less than a magnitude of the negative programming voltage.

12. The magnetoresistive memory device of claim 11 , wherein each of the positive programming voltage and the negative programming voltage has a magnitude in a range from 100 mV to 1,500 mV.

13. The magnetoresistive memory device of claim 12 , wherein the sensing voltage is in a range from 50 mV to 300 mV.

14. A method of operating the magnetoresistive memory device of claim 10 , comprising:

programming the MRAM cell into a first programmed state by applying a positive programming voltage to the second electrode relative to the first electrode, such that a magnetization direction of the free layer is parallel to a magnetization direction of the reference layer; and

programming the MRAM cell into a second programmed state by applying a negative programming voltage to the second electrode relative to the first electrode, such that the magnetization direction in the free layer is antiparallel to the magnetization direction of the reference layer.

15. The method of claim 14 , further comprising applying a sensing voltage to the first electrode relative to the second electrode, and determining a magnitude of electrical current that tunnels through the magnetic tunnel junction.

16. The method of claim 15 , wherein each of the positive programming voltage and the negative programming voltage has a magnitude in a range from 100 mV to 1,500 mV.

17. The method of claim 16 , wherein the sensing voltage is in a range from 50 mV to 500 mV.

18. A method of forming a spin-transfer torque (STT) memory cell, comprising:

forming a first electrode;

forming a reference layer over the first electrode;

forming a nonmagnetic tunnel barrier layer over the reference layer;

forming a free layer over the nonmagnetic tunnel barrier layer;

forming a nonmagnetic metal dust layer over the free layer, wherein the nonmagnetic metal dust layer consists essentially of a single elemental metal selected from Ir, Pd, Mg, Pt, W, Ta, Hf, Pd, Ru, or Rh;

forming a hafnium oxide layer over the free layer and the nonmagnetic metal dust layer, and

forming a second electrode over the hafnium oxide layer.

19. The magnetoresistive memory device of claim 1 , wherein the nonmagnetic metal dust layer is discontinuous and has a sub-monolayer thickness.

20. The method of claim 18 , wherein the nonmagnetic metal dust layer is discontinuous and has a sub-monolayer thickness.