Memory cells, semiconductor devices, and methods of fabrication
A magnetic cell includes magnetic, secondary oxide, and getter seed regions. During formation, a diffusive species is transferred from a precursor magnetic material to the getter seed region, due to a chemical affinity elicited by a getter species. The depletion of the magnetic material enables crystallization of the depleted magnetic material through crystal structure propagation from a neighboring crystalline material, without interference from the now-enriched getter seed region. This promotes high tunnel magnetoresistance and high magnetic anisotropy strength. Also during formation, another diffusive species is transferred from a precursor oxide material to the getter seed region, due to a chemical affinity elicited by another getter species. The depletion of the oxide material enables lower electrical resistance and low damping in the cell structure. Methods of fabrication and semiconductor devices are also disclosed.
1. A memory cell, comprising:
a magnetic cell core comprising:
a magnetic tunnel junction sub-structure comprising:
a fixed region;
a free region; and
an intermediate oxide region between the fixed region and the free region;
a secondary oxide region adjacent the magnetic tunnel junction sub-structure; and
a getter seed region proximate the secondary oxide region and
comprising:
an oxygen-getter species bonded to oxygen; and
another getter species bonded to a diffused species.
2. The memory cell of claim 1 , wherein:
the free region is formed from a precursor magnetic material; and
the diffused species bonded to the another getter species is diffused from the precursor magnetic material.
3. The memory cell of claim 1 , wherein:
the secondary oxide region is formed from a precursor oxide material; and
the oxygen bonded to the oxygen-getter species is diffused from the precursor oxide material.
4. The memory cell of claim 1 , wherein the secondary oxide region is electrically conductive.
5. The memory cell of claim 1 , wherein the oxygen-getter species comprises at least one of calcium (Ca), strontium (Sr), beryllium (Be), lanthanum (La), barium (Ba), aluminum (Al), or magnesium (Mg).
6. The memory cell of claim 1 , wherein the another getter species comprises at least one of tantalum (Ta), ruthenium (Ru), tungsten (W), aluminum (Al), titanium (Ti), zirconium (Zr), nitrogen (N), hafnium (Hf), or nickel (Ni).
7. The memory cell of claim 1 , wherein the diffused species comprises boron (B).
8. The memory cell of claim 1 , wherein the getter seed region exhibits an amorphous structure.
9. The memory cell of claim 1 , wherein the memory cell exhibits a tunnel magnetoresistance (TMR) of greater than about 1.20 (120%).
10. The memory cell of claim 1 , wherein the secondary oxide region further comprises the another getter species.
11. The memory cell of claim 1 , wherein only the getter seed region comprises the another getter species.
12. A memory cell, comprising:
a magnetic region comprising cobalt (Co) and iron (Fe), the magnetic region exhibiting a switchable magnetic orientation;
an oxide region disposed between the magnetic region and another magnetic region exhibiting a substantially fixed magnetic orientation;
another oxide region adjacent the magnetic region and comprising oxygen concentrated proximate an interface with the magnetic region; and
an amorphous getter seed region adjacent the another oxide region, the amorphous getter seed region comprising oxygen, boron, an oxygen-getter species, and a boron-getter species, the boron-getter species comprising tungsten (W), ruthenium (Ru), and nitrogen (N).
13. The memory cell of claim 12 , wherein the magnetic region and the another magnetic region exhibit vertical magnetic orientations.
14. The memory cell of claim 12 , wherein the amorphous getter seed region comprises the oxygen bonded to the oxygen-getter species, the oxygen-getter species comprising at least one of calcium (Ca), strontium (Sr), beryllium (Be), lanthanum (La), barium (Ba), aluminum (Al), or magnesium (Mg).
15. The memory cell of claim 1 , wherein the another getter species comprises tungsten and nitrogen; tungsten, ruthenium, and boron; tungsten and ruthenium; or iron, cobalt, and tungsten.
16. The memory cell of claim 12 , wherein the oxygen-getter species comprises at least one of calcium (Ca), strontium (Sr), beryllium (Be), lanthanum (La), or barium (Ba).
17. A method of forming a memory cell, comprising:
forming a precursor structure, comprising:
forming a precursor getter seed material over a substrate, the precursor getter seed material comprising:
tungsten and nitrogen,
tungsten, ruthenium, and boron,
tungsten and ruthenium, or
iron, cobalt, and tungsten,
forming a precursor oxide material over the precursor getter seed material;
forming a precursor magnetic material over the precursor oxide material; and
diffusing a diffusive species from the precursor magnetic material and diffusing oxygen from the precursor oxide material to the precursor getter seed material to convert at least a portion of the precursor magnetic material into a depleted magnetic material, to convert at least a portion of the precursor oxide material into an oxygen-depleted material, and to convert at least a portion of the precursor getter seed material into an enriched getter seed material; and
patterning the precursor structure to form a cell core structure comprising:
a getter seed region from the enriched getter seed material;
a secondary oxide region formed from the oxygen-depleted material; and
a free region formed from the depleted magnetic material.
18. The method of claim 17 , wherein diffusing a diffusive species from the precursor magnetic material and diffusing oxygen from the precursor oxide material to the precursor getter material comprises diffusing the diffusive species from the precursor magnetic material through the precursor oxide material to the precursor getter material.
19. The method of claim 17 , wherein forming a precursor oxide material over the precursor getter seed material comprises incorporating, into an oxide material, a getter species having a chemical affinity for the diffusive species.
20. A method of forming a semiconductor structure, comprising:
forming an amorphous precursor getter seed material over a substrate, the amorphous precursor getter seed material comprising a boron-getter species and an oxygen-getter species;
forming a precursor oxide material comprising oxygen over the amorphous precursor getter seed material;
forming a precursor magnetic material comprising boron over the precursor oxide material;
forming another oxide material over the precursor magnetic material; and
annealing at least the precursor magnetic material and the precursor oxide material to react the boron from the precursor magnetic material with the boron-getter species of the amorphous precursor getter seed material and to react the oxygen from the precursor oxide material with the oxygen-getter species of the amorphous precursor getter seed material.
21. The method of claim 20 , wherein forming an amorphous precursor getter seed material over a substrate comprises simultaneously:
sputtering the boron-getter species from a sputter target; and
sputtering the oxygen-getter species from another sputter target.
22. 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 tunnel junction sub-structure over a substrate, the magnetic tunnel junction sub-structure comprising:
a free region exhibiting a vertical, switchable magnetic orientation;
a fixed region exhibiting a vertical, substantially fixed magnetic orientation; and
an intermediate oxide region between the free region and the fixed region;
another oxide region contacting the free region; and
an amorphous region proximate the free region and the another oxide region, the amorphous region comprising boron and oxygen.