Semiconductor devices with seed and magnetic regions and methods of fabrication
A magnetic cell core includes a seed region with a plurality of magnetic regions and a plurality of nonmagnetic regions thereover. The seed region provides a template that enables formation of an overlying nonmagnetic region with a microstructure that enables formation of an overlying free region with a desired crystal structure. The free region is disposed between two nonmagnetic regions, which may both be configured to induce surface/interface magnetic anisotropy. The structure is therefore configured to have a high magnetic anisotropy strength, a high energy barrier ratio, high tunnel magnetoresistance, a low programming current, low cell-to-cell electrical resistance variation, and low cell-to-cell variation in magnetic properties. Methods of fabrication, memory arrays, memory systems, and electronic systems are also disclosed.
1. An electronic system, comprising:
a magnetic structure between a lower electrode and an upper electrode, the magnetic structure comprising:
a free region between a lower nonmagnetic region and an intermediate nonmagnetic region, the free region comprising a magnetic material;
a fixed region above the intermediate nonmagnetic region; and
a seed region directly below the lower nonmagnetic region, the seed region comprising the same chemical elements as the magnetic material of the free region.
2. The electronic system of claim 1 , wherein the chemical elements comprise at least one of cobalt (Co) or iron (Fe).
3. The electronic system of claim 1 , wherein at least a portion of the fixed region also comprises the same chemical elements as the magnetic material of the free region.
4. The electronic system of claim 1 , wherein the lower nonmagnetic region and the intermediate nonmagnetic region comprise the same oxide material.
5. The electronic system of claim 1 , wherein:
the fixed region exhibits a fixed vertical magnetic orientation; and
the seed region exhibits another fixed vertical magnetic orientation oppositely directed to the fixed vertical magnetic orientation of the fixed region.
6. The electronic system of claim 1 , wherein:
the fixed region exhibits a fixed vertical magnetic orientation; and
the seed region exhibits a fixed horizontal magnetic orientation.
7. The electronic system of claim 1 , wherein:
the free region and the fixed region exhibit vertical magnetic orientations; and
the seed region does not exhibit magnetism.
8. The electronic system of claim 1 , wherein the seed region, the free region, and at least a lower portion of the fixed region each exhibit a crystalline structure.
9. The electronic system of claim 8 , wherein the lower nonmagnetic region and the intermediate nonmagnetic region exhibit the crystalline structure.
10. The electronic system of claim 8 , wherein an upper portion of the fixed region exhibits a different crystalline structure than the crystalline structure exhibited by the lower portion of the fixed region.
11. An electronic system, comprising:
at least one magnetic structure over an electrode, the at least one magnetic structure comprising:
a nonmagnetic oxide region between a seed region and a free region, the seed region and the free region each comprising cobalt (Co) and iron (Fe); and
another nonmagnetic oxide region between the free region and a fixed region,
wherein no oxide material is between the seed region and the electrode.
12. The electronic system of claim 11 , wherein:
the seed region defines a thickness of about 6 Å; and
the free region defines a thickness of at least about 14 Å.
13. The electronic system of claim 12 , wherein the free region defines a thickness of at least about 50 Å.
14. The electronic system of claim 11 , wherein the nonmagnetic oxide region is thinner than the another nonmagnetic oxide region.
15. The electronic system of claim 11 , wherein the nonmagnetic oxide region comprises ruthenium.
16. A method of forming an electronic system comprising a magnetic structure, the method comprising:
forming a precursor magnetic structure, comprising:
forming a seed material over a conductive material of a lower electrode, the seed material exhibiting an amorphous state;
forming a lower nonmagnetic material directly over the seed material while the seed material exhibits the amorphous state;
forming a free region comprising a magnetic material exhibiting a switchable vertical magnetic orientation over the lower nonmagnetic material, the magnetic material of the free region comprising the same chemical elements as the seed material; and
forming an intermediate nonmagnetic material over the magnetic material, the free region between the lower nonmagnetic region and the intermediate nonmagnetic material;
annealing the precursor structure to crystallize at least the magnetic material;
after the annealing and before patterning the precursor structure to form the magnetic structure of the electronic system, forming a fixed region comprising another magnetic material over the intermediate nonmagnetic material, the another magnetic material exhibiting a fixed vertical magnetic orientation; and
forming an upper electrode over the another magnetic material, the magnetic structure between the lower electrode and the upper electrode.
17. The method of claim 16 , wherein forming the seed material comprises forming a CoFeB material over the conductive material.
18. The method of claim 16 , wherein forming the lower nonmagnetic material directly over the seed material comprises forming an oxide material exhibiting a bcc (001) crystalline structure over the seed material while the seed material exhibits the amorphous state.
19. The method of claim 16 , further comprising another annealing after forming the another magnetic material, the another annealing conducted at a lower temperature than the annealing before forming the another magnetic material.
20. The method of claim 16 , wherein forming the seed material is not preceded by forming an oxide material over the lower electrode.