Methods of forming semiconductor devices including tunnel barrier materials
A semiconductor device comprises an array of magnetic cell structures each comprising a magnetic tunnel junction over an electrode on a substrate. Each of the magnetic tunnel junctions includes a magnetic material over the substrate, a first tunnel barrier material over the magnetic material, a second tunnel barrier material over the annealed first tunnel barrier material, and another magnetic material over the second tunnel barrier material. Each magnetic tunnel junction is configured to exhibit a tunnel magnetoresistance greater than or equal to about 180% at a resistance area product of less than about 8 ohm μm 2 . The semiconductor device also includes another electrode over the another magnetic material. Semiconductor devices including the magnetic tunnel junctions, methods of forming the magnetic tunnel junctions, and methods of forming semiconductor devices including the magnetic tunnel junctions are disclosed.
1. A method of forming a semiconductor device, the method comprising:
forming a magnetic material over an electrode on a base material;
forming, by magnetron sputtering with a magnesium oxide target, a first portion of an oxide tunnel barrier material comprising magnesium oxide over the magnetic material without crystallizing the magnetic material;
annealing the magnetic material and the first portion of the oxide tunnel barrier material to crystallize the magnetic material and fill oxygen vacancies in the first portion of the oxide tunnel barrier material;
forming, by magnetron sputtering with the magnesium oxide target, a second portion of the oxide tunnel barrier material comprising magnesium oxide over the annealed first portion of the oxide tunnel barrier material and the crystallized magnetic material, wherein forming the second portion comprises forming the second portion at a higher temperature than forming the first portion of the oxide tunnel barrier material;
forming another magnetic material over the second portion of the oxide tunnel barrier material; and
forming another electrode over the another magnetic material.
2. The method of claim 1 , wherein forming, by magnetron sputtering with a magnesium oxide target, a first portion of an oxide tunnel barrier material over the magnetic material comprises forming the first portion of the oxide tunnel barrier material at a temperature between about 20° C. and about 25° C.
3. The method of claim 1 , wherein annealing the magnetic material and the first portion of the oxide tunnel barrier material comprises exposing the magnetic material and the first portion of the oxide tunnel barrier material to a temperature between about 300° C. and about 600° C.
4. The method of claim 1 , wherein annealing the magnetic material and the first portion of the oxide tunnel barrier material comprises crystallizing the magnetic material and the first portion of the oxide tunnel barrier material to exhibit the same crystal orientation.
5. The method of claim 1 , wherein annealing the magnetic material and the first portion of the oxide tunnel barrier material to crystallize the magnetic material and fill oxygen vacancies in the first portion of the oxide tunnel barrier material comprises forming the first portion of the oxide tunnel barrier material comprising a stoichiometric oxide tunnel barrier material.
6. The method of claim 1 , wherein forming, by magnetron sputtering with a magnesium oxide target, a first portion of an oxide tunnel barrier material over the magnetic material comprises forming the first portion of the oxide tunnel barrier material comprising a nonstoichiometric oxide tunnel barrier material.
7. The method of claim 1 , wherein forming a second portion, by magnetron sputtering with a magnesium oxide target, of the oxide tunnel barrier material comprises forming the second portion of the oxide tunnel barrier material comprising a stoichiometric oxide tunnel barrier material.
8. The method of claim 1 , wherein forming, by magnetron sputtering with a magnesium oxide target, a first portion of an oxide tunnel barrier material over the magnetic material comprises forming the first portion of the oxide tunnel barrier material comprising an amorphous oxide tunnel barrier material.
9. A method of forming a magnetic tunnel junction, the method comprising:
forming, at a first temperature, a portion of an amorphous barrier material over an amorphous magnetic material;
annealing the portion of the amorphous barrier material and the amorphous magnetic material to crystallize the portion of the amorphous barrier material and the amorphous magnetic material;
forming, at a second temperature, another portion of the barrier material over the crystallized portion of the barrier material, the second temperature greater than the first temperature;
annealing the another portion of the barrier material to crystallize the another portion of the barrier material; and
forming another magnetic material over the crystallized another portion of the barrier material.
10. The method of claim 9 , wherein forming, at a second temperature, another portion of the barrier material over the crystallized portion of the barrier material comprises forming the another portion of the barrier material at a temperature between about 300° C. and about 600° C.
11. The method of claim 9 , wherein:
forming, at a first temperature, a portion of an amorphous barrier material over an amorphous magnetic material comprises forming, at the first temperature, amorphous magnesium oxide over the amorphous magnetic material; and
forming, at a second temperature, another portion of a barrier material over the crystallized portion of the barrier material comprises forming, at the second temperature, magnesium oxide over the crystallized portion of the barrier material.
12. The method of claim 9 , wherein forming, at a first temperature, a portion of an amorphous barrier material comprises forming the portion of the amorphous barrier material to a thickness between about 1.0 and about 1.5 times a thickness of the another portion of the barrier material.
13. The method of claim 9 , wherein:
forming, at a first temperature, a portion of an amorphous barrier material over an amorphous magnetic material comprises forming the portion of the amorphous barrier material at a temperature between about 0° C. and about 25° C.; and
forming, at a second temperature, another portion of a barrier material over the crystallized portion of the barrier material comprises forming the another portion of the barrier material at a temperature between about 300° C. and about 600° C.
14. A method of forming a semiconductor device, the method comprising:
forming a seed material over a substrate;
forming an amorphous magnetic material over the seed material;
forming, at a first temperature, a portion of an amorphous oxide material over the amorphous magnetic material;
forming, at a second temperature between about 300° C. and about 600° C. and higher than the first temperature, another portion of an oxide material over the portion of the amorphous oxide material; and
forming another magnetic material over the another portion of the oxide material.
15. The method of claim 14 , wherein forming another portion of the oxide material comprises forming the another portion of the oxide material to have a thickness less than a thickness of the portion of the oxide material.
16. The method of claim 14 , further comprising annealing the amorphous magnetic material and the portion of the amorphous oxide material prior to forming the another portion of the oxide material over the portion of the oxide material.
17. The method of claim 14 , further comprising forming a magnetic tunnel junction exhibiting a tunnel magnetoresistance of between about 180% and about 600% at a resistance area product of less than about 8 ohm μm 2 , the magnetic tunnel junction comprising the magnetic material, the portion of the oxide material, the another portion of the oxide material, and the another magnetic material.
18. The method of claim 14 , further comprising forming a magnetic tunnel junction exhibiting a tunnel magnetoresistance of between about 180% and about 205% at a resistance area product of between about 4 ohm μm 2 and about 8 ohm μm 2 , the magnetic tunnel junction comprising the magnetic material, the portion of the oxide material, the another portion of the oxide material, and the another magnetic material.
19. The method of claim 14 , wherein forming, at a first temperature, a portion of an amorphous oxide material over the amorphous magnetic material comprises forming the portion of the amorphous oxide material to have a thickness between about 1.0 and about 1.5 times a thickness of the another portion of the oxide material.