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| Magnetic Tunnel Junctions with AlN and AlO Barriers |
| Journal of Magnetics, Volume 9, Number 1, 31 Mar 2004, Pages 17-22 |
Tae-Sick Yoon(Research Center for Advanced Magnetic Materials, Chungnam National University, Department of Electronic Engineering, Tohoku University), Yoshimura Satoru(Department of Electronic Engineering, Tohoku University), Tsunoda Masakiyo(Department of Electronic Engineering, Tohoku University), Takahashi Migaku(Department of Electronic Engineering, Tohoku University), Bum-Chan Park(Department of Electronic Engineering, Tohoku University), Young-Woo Lee(Department of Electronic Engineering, Tohoku University), Li Ying(Institute of Materials, School of Materials Science and Engineering, Shanghai University), Chong-Oh Kim*  (Research Center for Advanced Magnetic Materials, Chungnam National University) |
| Abstract |
| We studied the magnetotransport properties of tunnel junctions with AlO and AlN barriers fabricated using microwave-excited plasma. The plasma nitridation process provided wider controllability than the plasma oxidization for the formation of MTJs with ultra-thin insulating layer, because of the slow nitriding rate of metal Al layers, comparing with the oxidizing rate of them. High tunnel magnetoresistance (TMR) ratios of 49 and 44% with respective resistance-area product (R×A) of 3×104 and 6×103Ωµm2 were obtained in the Co-Fe/Al-N/Co-Fe MTJs. We conclude that AlN is a hopeful barrier material to realize MTJs with high TMR ratio and low R×A for high performance MRAM cells. In addition, in order to clarify the annealing temperature dependence of TMR, the local transport properties were measured for Ta 50Å/Cu 200Å/Ta 50Å/Ni76Fe24 20Å/Cu 50Å/MN75Ir25 100ÅCo71Fe29 40Å/Al-O junction with dAl= 8Å and po2×tox =8.4×104L at various temperatures. The current histogram statistically calculated from the electrical current image was well in accord with the fitting result considering the Gaussian distribution and Fowler-Nordheim equation. After annealing at 340℃, where the TMR ratio of the corresponding MTJ had the maximum value of 44%, the average barrier height increased to 1.12 eV and its standard deviation decreased to 0.1 eV. The increase of TMR ratio after annealing could be well explained by the enhancement of the average barrier height and the reduction of its fluctuation. |
| Keywords: Tunnel junctions; AlN barrier; AlO barrier; Microwave-excited plasma; Nitridation process; Local transport properties; Fowler-Nordheim equation |
| DOI: |
| Full Text: PDF |
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