Magnetic memory device and method for fabricating the same
A magnetic memory device includes a pinned layer, a free layer, a tunnel barrier layer between the pinned layer and the free layer, a first oxide layer spaced apart from the tunnel barrier layer with the free layer therebetween, and a second oxide layer spaced apart from the free layer with the first oxide layer therebetween. The first oxide layer includes an oxide of a first material and may have a thickness of 0.3 Å to 2.0 Å. The second oxide layer may include an oxide of a second material and may have a thickness of 0.1 Å to 5.0 Å. A first oxygen affinity of the first material may be greater than a second oxygen affinity of the second material.
1. A magnetic memory device comprising:
a pinned layer;
a free layer;
a tunnel barrier layer between the pinned layer and the free layer;
a first oxide layer spaced apart from the tunnel barrier layer with the free layer therebetween, the first oxide layer including an oxide of a first material, the first material having a first oxygen affinity, and the first oxide layer having a thickness of 0.3 Å to 2.0 Å; and
a second oxide layer spaced apart from the free layer with the first oxide layer therebetween, the second oxide layer including an oxide of a second material, the second material having a second oxygen affinity that is less than the first oxygen affinity, and the second oxide layer having a thickness of 0.1 Å to 5.0 Å.
2. The magnetic memory device of claim 1 , wherein a first oxide decomposition potential of the oxide of the first material is greater than a second oxide decomposition potential of the oxide of the second material.
3. The magnetic memory device of claim 1 , wherein the free layer includes a magnetic element that is configured to bond with oxygen and induce interfacial perpendicular magnetic anisotropy (i-PMA).
4. The magnetic memory device of claim 1 , further comprising:
a substrate, wherein
the pinned layer, the free layer, the tunnel barrier layer, the first oxide layer, and the second oxide layer are sequentially stacked on the substrate.
5. The magnetic memory device of claim 4 , further comprising:
a seed layer under a bottom surface of the pinned layer; and
a first capping layer covering a top surface of the second oxide layer.
6. The magnetic memory device of claim 5 , further comprising:
a second capping layer covering a side surface of the seed layer, a side surface of the pinned layer, a side surface of the free layer, a side surface of the tunnel barrier layer, a side surface of the first oxide layer, a side surface of the second oxide layer, and a side surface and a top surface of the first capping layer.
7. The magnetic memory device of claim 6 , wherein the second capping layer includes silicon nitride.
8. The magnetic memory device of claim 1 , wherein
the first oxide layer is a native oxide of the first material, and
the second oxide layer is a native oxide of the second material.
9. The magnetic memory device of claim 1 , wherein
the free layer and the first oxide layer contain boron (B), and
the second oxide layer does not contain boron (B).
10. The magnetic memory device of claim 9 , wherein a boron concentration of the free layer is smaller than a boron concentration of the first oxide layer.
11. The magnetic memory device of claim 10 , wherein the boron concentration of the free layer is 30 at % or less, and the boron concentration of the first oxide layer is 50 at % or less.
12. A magnetic memory device comprising:
a pinned layer;
a free layer;
a tunnel barrier layer between the pinned layer and the free layer;
a first oxide layer spaced apart from the tunnel barrier layer with the free layer therebetween, and the first oxide layer including a first material including at least one of calcium (Ca), strontium (Sr), magnesium (Mg), hafnium (Hf), zirconium (Zr) and aluminum (Al), the first material having a first oxygen affinity; and
a second oxide layer spaced apart from the free layer with the first oxide layer therebetween, the second oxide layer including a second material different from the first material, the second material having a second oxygen affinity that is less than the first oxygen affinity, wherein
the first oxide layer is in contact with the free layer, or the second oxide layer is in contact with the first oxide layer, or both the first oxide layer is in contact with the free layer and the second oxide layer is in contact with the first oxide layer.
13. The magnetic memory device of claim 12 , wherein the second material includes at least one of titanium (Ti), tantalum (Ta), gallium (Ga), vanadium (V) and zinc (Zn).
14. The magnetic memory device of claim 12 , wherein
the first oxide layer has a thickness of 0.3 Å to 2.0 Å, and
the second oxide layer has a thickness of 0.1 Å to 5.0 Å.
15. The magnetic memory device of claim 12 , wherein
the free layer includes an interfacial layer in contact with the first oxide layer, and
the interfacial layer is configured to induce interfacial perpendicular magnetic anisotropy (i-PMA).
16. A magnetic memory device comprising:
a pinned layer;
a free layer;
a tunnel barrier layer between the pinned layer and the free layer;
a first oxide layer spaced apart from the tunnel barrier layer with the free layer therebetween, the first oxide layer including a first metal oxide having a first oxide decomposition potential; and
a second oxide layer spaced apart from the free layer with the first oxide layer therebetween, the second oxide layer including a second metal oxide different from the first metal oxide, the second metal oxide having a second oxide decomposition potential that is less than the first oxide decomposition potential, wherein
the first oxide layer is in contact with the free layer, or the second oxide layer is in contact with the first oxide layer, or both the first oxide layer is in contact with the free layer and the second oxide layer is in contact with the first oxide layer.
17. The magnetic memory device of claim 16 , wherein a difference between the first oxide decomposition potential and the second oxide decomposition potential is 0 . 1 V or more.
18. The magnetic memory device of claim 16 , wherein
the first oxide decomposition potential at 1300 K is 2.1 V or more, and
the second oxide decomposition potential at 1300 K is 2.0 V or less.
19. The magnetic memory device of claim 16 , wherein
the first oxide layer has a thickness of 0.3 Å to 2.0 Å, and
the second oxide layer has a thickness of 0.1 Å to 5.0 Å.
20. The magnetic memory device of claim 16 , wherein the free layer includes iron (Fe),
the first metal oxide includes at least one of calcium (Ca), strontium (Sr), magnesium (Mg), hafnium (Hf), zirconium (Zr) and aluminum (Al), and
the second metal oxide includes at least one of titanium (Ti), tantalum (Ta), gallium (Ga), vanadium (V) and zinc (Zn).