We investigated the effects of the crystallinity of the capping layer materials on the crystallization of amorphous top CoFeB (t-CoFeB) and the magnetoresistance properties and temperature sensitivities of the magnetic tunnel junctions (MTJs). When a (002)-textured hcp Ru capping layer was used, the amorphous t-CoFeB was crystallized to bcc-CoFe (110) during annealing. Using the CoFe (110)/Ru (002) texture relation is the best way to reduce the lattice mismatch down to 5.6%. However, when a polycrystalline TiAl (two phase: amorphous and fine polycrystalline) or amorphous ZrAl capping layer was used, the amorphous t-CoFeB was crystallized to bcc-CoFe (002) during annealing due to the MgO (001) template effect. The tunneling magneto resistance ratios of the annealed MTJs capped with Ru, TiAl, and ZrAl were 46.7%, 71.8%, and 72.7%, respectively, which depended on the texture and the epitaxiality of t-CoFeBMgO (001). Consequently, the texture evolution of the amorphous t-CoFeB during annealing can be controlled by adjusting the crystallinity of the adjacent capping layer which, in turn, affects the magnetoresistance properties and temperature sensitivities of the MTJs.
ASJC Scopus subject areas
- Physics and Astronomy(all)