Magnetic tunnel junction device with perpendicular magnetization and method of fabricating the same

1. A perpendicular magnetic anisotropy (PMA) magnetic tunnel junction device, comprising:

a tunneling dielectric layer having a first surface and a second surface;

a reference layer having a magnetization direction fixed on a direction perpendicular to a surface of the reference layer and disposed on the first surface of the tunneling dielectric layer;

a free layer having a magnetization direction parallel to or anti-parallel to the magnetization direction of the reference layer, and disposed on the second surface of the tunneling dielectric layer; and

a capping layer consisted of magnesium, aluminum and oxygen, and disposed on the free layer, wherein the capping layer comprises:

a magnesium oxide (MgO) layer disposed on the free layer and having a surface provided with a plurality of gaps; and

an aluminum oxide (AlOx) layer filled in the gaps of the magnesium oxide layer.

2. The perpendicular magnetic anisotropy magnetic tunnel junction device of claim 1 , wherein the reference layer includes a perpendicular magnetization material.

3. The perpendicular magnetic anisotropy magnetic tunnel junction device of claim 2 , wherein the perpendicular magnetization material includes a CoFeB single film and a combination of a Co/Pt multilayer film, a Co/Pd multilayer film, a Co/Ni multilayer film, a CoPd alloy film, a FePt alloy film, a TbFeCo alloy, or a Ru layer is further included in between each of above-said film layers.

4. The perpendicular magnetic anisotropy magnetic tunnel junction device of claim 1 , wherein a material of the tunneling dielectric layer is magnesium oxide.

5. The perpendicular magnetic anisotropy magnetic tunnel junction device of claim 1 , wherein the free layer is a CoFeB film, a CoFe film, a Fe film or a multilayer film including a combination of the above-said materials.

6. The perpendicular magnetic anisotropy magnetic tunnel junction device of claim 5 , wherein a non-magnetic metal layer is further included between each film layer among the multilayer film.

7. A method of fabricating a perpendicular magnetic anisotropy magnetic tunnel junction device, comprising:

forming a tunneling dielectric layer;

forming a reference layer on a first surface of the tunneling dielectric layer, and the reference layer having a magnetization direction fixed on a direction perpendicular to a surface of the reference layer;

forming a free layer on the second surface of the tunneling dielectric layer, the free layer having a magnetization direction parallel to or anti-parallel to the magnetization direction of the reference layer and covering on the tunneling dielectric layer; and

forming a capping layer consisted of magnesium, aluminum and oxygen to cover the free layer, wherein a method of forming the capping layer comprises:

forming a magnesium oxide layer to cover the free layer;

forming an aluminum layer to cover the magnesium oxide layer and to fill in at least one gap of the magnesium oxide layer; and

performing an oxidation process to oxidize the aluminum layer into an aluminum oxide layer.

8. The method of fabricating a perpendicular magnetic anisotropy magnetic tunnel junction device of claim 7 , wherein a method of forming the capping layer includes a sputtering process and an atomic layer deposition process.

9. The method of fabricating a perpendicular magnetic anisotropy magnetic tunnel junction device of claim 7 , wherein the oxidation process includes a plasma oxidation process or a natural oxidation.

10. The method of fabricating a perpendicular magnetic anisotropy magnetic tunnel junction device of claim 7 , wherein the reference layer, the tunneling dielectric layer, the free layer and the capping layer are sequentially formed.

11. The method of fabricating a perpendicular magnetic anisotropy magnetic tunnel junction device of claim 7 , wherein the capping layer, the free layer, the tunneling dielectric layer and the reference layer are sequentially formed.