Evolution of barrier-resistance noise in CoFeB/MgO/CoFeB tunnel junctions during annealing

• Published in: Journal of applied physics Vol. 107; no. 6; pp. 064502 - 064502-7
• Main Authors: Stearrett, Ryan, Wang, W. G., Shah, L. R., Gokce, Aisha, Xiao, J. Q., Nowak, E. R.
• Format: Journal Article
• Language: English
• Published: American Institute of Physics 15.03.2010
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3327440

The low-frequency resistance noise in sputtered-deposited magnetic tunnel junctions with MgO barriers has been measured as a function of annealing time at different annealing temperatures. The noise has a 1 / f spectrum and it is quantified by a Hooge-like parameter α given in units of μ m 2 . Unannealed devices have the highest noise levels and their α parameters exhibit a pronounced dependence on the voltage bias across the junction. A significant increase in tunneling magnetoresistance (TMR) is observed for short annealing times (on the order of minutes) at high temperatures and it is correlated with a large reduction in noise and in its bias dependence. The maximum TMR and minimum noise levels are reached at a later time that depends on temperature, being shorter at higher annealing temperatures. Devices annealed at 380 and at 430 ° C exhibit the same minimum noise levels, α ≈ 2 × 10 − 10   μ m 2 . The origin of the resistance noise, its annealing time evolution, and its bias dependence are discussed and they are attributed to vacancy defects in the MgO barriers.