Memory cells, methods of fabrication, semiconductor device structures, memory systems, and electronic systems
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. A memory cell, comprising:
a magnetic cell core comprising:
a seed region consisting of cobalt, iron, and boron;
a nonmagnetic region over and in contact with the seed region, the nonmagnetic region having a bcc (001) crystalline structure and consisting of a nonmagnetic oxide material;
a free region over the nonmagnetic region;
another nonmagnetic region over the free region; and
a fixed region over the another nonmagnetic region,
the seed region configured to not exhibit magnetism affecting the free region.
2. The memory cell of claim 1 , wherein a material from which the seed region is formed, a material from which the free region is formed, and a material from which the fixed region is formed each comprise the same elements as one another.
3. The memory cell of claim 1 , wherein the nonmagnetic oxide material of the nonmagnetic region and a material from which the another nonmagnetic region is formed each comprise the same elements as one another.
4. The memory cell of claim 1 , wherein the free region has a bcc (001) crystalline structure.
5. The memory cell of claim 1 , wherein the free region exhibits a vertical magnetic orientation.
6. A method of forming a magnetic memory cell, comprising:
forming a structure comprising:
forming a seed material over a substrate, the seed material consisting of cobalt, iron, and boron;
forming a nonmagnetic oxide material over the seed material;
forming a magnetic material over the nonmagnetic oxide material; and
forming another nonmagnetic material over the magnetic material;
annealing the structure;
forming another magnetic material over the another nonmagnetic material to form a precursor structure; and
patterning the precursor structure to form a magnetic cell core of a magnetic memory cell, the magnetic cell core comprising:
a seed region comprising at least a portion of the seed material consisting of the cobalt, iron, and boron;
a nonmagnetic region over and in contact with the seed region, the nonmagnetic region having a bcc (001) crystalline structure and consisting of at least a portion of the nonmagnetic oxide material;
a free region over the nonmagnetic region, the magnetic region comprising at least a portion of the magnetic material;
another nonmagnetic region over the free region; the another nonmagnetic region comprising at least a portion of the another nonmagnetic material; and
a fixed region over the another nonmagnetic region, the fixed region comprising at least a portion of the another magnetic material,
the seed region configured to not exhibit magnetism affecting the free region.
7. The method of claim 6 , wherein forming a nonmagnetic oxide material over the seed material comprises forming the nonmagnetic oxide material with a crystalline structure.
8. The method of claim 7 , wherein:
forming a magnetic material over the nonmagnetic oxide material comprises forming the magnetic material to exhibit an amorphous structure; and
annealing the structure comprises propagating the crystalline structure from the nonmagnetic oxide material to the magnetic material to crystallize the magnetic material.
9. The method of claim 6 , wherein forming a seed material over a substrate comprises forming a base magnetic material over the substrate, the base magnetic material configured to not exhibit magnetism affecting the free region.
10. The method of claim 6 , wherein:
forming a seed material over a substrate comprises forming a first CoFeB material over the substrate;
forming a magnetic material over the nonmagnetic oxide material comprises forming a second CoFeB material over the nonmagnetic oxide material; and
forming another magnetic material over the another nonmagnetic material comprises forming a third CoFeB material over the another nonmagnetic material.
11. The method of claim 6 , further comprising, before annealing the structure, forming a lower portion of the another magnetic material over the nonmagnetic material.
12. The method of claim 6 , wherein forming a magnetic material over the nonmagnetic oxide material comprises forming sub-regions of the magnetic material; at least one of the sub-regions comprising a different atomic ratio of iron to boron than another sub-region of the sub-regions.
13. The method of claim 6 , further comprising, before forming a magnetic material over the nonmagnetic oxide material, forming a conductive material over the nonmagnetic oxide material.
14. The method of claim 13 , wherein forming a conductive material comprises forming ruthenium.
15. The method of claim 6 , wherein annealing the structure comprises heating the structure to a temperature between about 300° C. and about 600° C.
16. A semiconductor device, comprising:
a spin torque transfer magnetic random access memory (STT-MRAM) array comprising:
STT-MRAM cells, at least one STT-MRAM cell of the STT-MRAM cells comprising:
a magnetic cell core comprising:
a seed region over a substrate, the seed region consisting of cobalt, iron, and boron;
a nonmagnetic region over and in contact with the seed region, the nonmagnetic region having a bcc (001) crystalline structure and consisting of at least one of magnesium oxide, aluminum oxide, or titanium oxide;
a free region over the nonmagnetic region;
another nonmagnetic region over the free region; and
a fixed region over the another nonmagnetic region, the fixed region comprising:
a portion having the bcc (001) crystalline structure; and
another portion having a different crystal structure than the bcc (001) crystalline structure.
17. The semiconductor device of claim 16 , wherein each of the seed region, the free region, and the fixed region comprises a CoFeB material.
18. The semiconductor device of claim 17 , wherein the seed region does not exhibit magnetism.
19. A spin torque transfer magnetic random access memory (STT-MRAM) system, comprising:
STT-MRAM cells, at least one STT-MRAM cell of the STT-MRAM cells comprising:
a magnetic cell core comprising:
a seed region over a substrate, the seed region consisting of cobalt, iron, and boron;
a nonmagnetic region over and in contact with the seed region, the nonmagnetic region having a bcc (001) crystalline structure and consisting of a nonmagnetic oxide material;
a free region over the nonmagnetic region, the free region comprising cobalt, iron, and boron;
another nonmagnetic region over the free region; and
another magnetic region on the another nonmagnetic region, the another magnetic region comprising cobalt, iron, and boron,
at least one of the free region or the another magnetic region comprising a portion, proximate to at least one of the nonmagnetic region or the another nonmagnetic region, having a greater atomic ratio of iron to boron than an atomic ratio of iron and boron in another portion of the at least one of the free region or the another magnetic region; and
conductive materials in operable communication with the magnetic cell core;
at least one peripheral device in operable communication with the at least one STT-MRAM cell; and
at least one of an access transistor, a bit line, a word line, or a source line in operable communication with the magnetic cell core.
20. The STT-MRAM system of claim 19 , wherein the seed region comprises a magnetic material.
21. The STT-MRAM system of claim 20 , wherein the seed region exhibits a vertical magnetic orientation.
22. The STT-MRAM system of claim 20 , wherein the seed region exhibits a magnetic orientation oppositely directed to a fixed magnetic orientation of the another magnetic region.
23. The STT-MRAM system of claim 22 , wherein the nonmagnetic region and the another nonmagnetic region are each configured as tunnel regions of the at least one STT-MRAM cell.
24. An electronic system, comprising:
at least one processor comprising:
at least one magnetic memory cell comprising:
a nonmagnetic region over and in contact with a seed region, the seed region consisting of cobalt, iron, and boron, the nonmagnetic region having a bcc (001) crystalline structure and consisting of a nonmagnetic oxide material;
a free region over the nonmagnetic region, the free region being thicker than the seed region; and
another nonmagnetic region over the free region; and
a power supply in operable communication with the at least one processor.
25. The electronic system of claim 24 , wherein the nonmagnetic region is thinner than the another nonmagnetic region.