In-situ annealing and etch back steps to improve exchange stiffness in cobalt iron boride based perpendicular magnetic anisotropy free layers
A method for forming a memory device that includes providing a free layer of an alloy of cobalt (Co), iron (Fe) and boron (B) overlying a reference layer; and forming metal layer comprising a boron (B) sink composition atop the free layer. Boron (B) may be diffused from the free layer to the metal layer comprising the boron sink composition. At least a portion of the metal layer including the boron (B) sink composition is removed. A metal oxide is formed atop the free layer. The free layer may be a crystalline cobalt and iron alloy. An interface between the metal oxide and free layer can provide perpendicular magnetic anisotropy character.
1. A method for forming a memory device comprising:
providing a single free layer of an alloy of cobalt (Co), iron (Fe) and boron (B) in direct contact with a first metal oxide layer, the first metal oxide layer overlying a reference layer;
forming a metal layer comprising a boron (B) sink composition atop the free layer;
diffusing boron (B) from the free layer to the metal layer comprising the boron sink composition using an anneal process having a duration ranging from 15 minutes to 30 minutes to remove the boron from the free layer, wherein a remaining composition of the free layer is cobalt (Co) and iron (Fe);
removing at least a portion of the metal layer comprising the boron sink composition after the anneal process, the portion of the metal layer being removed including the boron (B) sink composition including said boron (B);
forming a regrowth metal layer on a surface of the single free layer after said removing said at least a portion of the metal layer comprising the boron sink composition, wherein the regrowth metal layer includes a metal selected from the group consisting of titanium (Ti), tantalum (Ta), zirconium (Zr) and combinations thereof, the regrowth metal layer having a thickness ranging from 1 Å to 5 Å; and
forming a second metal oxide layer atop the regrowth metal layer using an oxygen containing exposure that is present on the single free layer, wherein the single free layer of the remaining composition of said cobalt (Co) and said iron (Fe) is crystalline and is present at an interface between and in direct contact with the first metal oxide layer and the second metal oxide layer to provide perpendicular magnetic anisotropy character.
2. The method of claim 1 , wherein the first metal oxide layer comprises magnesium oxide and the reference layer comprises at least one of Fe, Ni, Co, Cr, V, Mn, Pd, Pt, B, O and N.
3. The method of claim 1 , wherein the diffusing boron (B) from the free layer to the metal layer comprises thermal annealing.