Correlation between write endurance and electrical low frequency noise in MgO based magnetic tunnel junctions

Abstract : The write endurance and the 1/f noise of electrical origin were characterized in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJ) for spin transfer torque or thermally assisted magnetic random access memories. A statistical study carried out on a set of 60 nominally identical patterned junctions of 200 nm diameter revealed a correlation trend between the electrical 1/f noise power in the unexercised MTJs and the number of write cycles that these MTJs can withstand before electrical breakdown. The junctions showing the largest 1/f noise power before the write endurance test (successive 30 ns pulses of 1.73 V) have the lowest endurance. In contrast, MTJs initially exhibiting lower 1/f noise tend to have a better electrical reliability, i.e., much longer write endurance. This correlation is explained by the presence of electron trapping sites in the MgO barrier and the role of electron trapping/detrapping phenomena in both MTJ reliability and its 1/f electrical noise power. These results suggest that 1/f noise could be used as a predictive characterization of the MTJ endurance.