Improvement of Transport Properties in Magnetic Tunneling Junctions by Capping Materials

• Published in: IEEE transactions on magnetics 2007-06, Vol.43 (6), p.2785-2787
• Main Authors: SHEN, Chih-Ta, YEN, Cheng-Tyng, TSAI, Ming-Jinn, CHEN, Wei-Chuan, YANG, Shan-Yi, WANG, Yung-Hung, LEE, Yuan-Jen, WANG, Ding-Yeong, HUNG, Chien-Chung, SHEN, Kuei-Hung, KAO, Ming-Jer
• Format: Article
• Language: English
• Subjects: Capping; Capping layer; Cross-disciplinary physics: materials science; rheology; Enhanced magnetoresistance; Exact sciences and technology; Iron compounds; Magnesium; Magnesium oxide; Magnetic flux; Magnetic materials; Magnetic properties; Magnetic tunneling; magnetic tunneling junction (MTJ); Magnetism; magnetoresistive random access memory (MRAM); Materials science; MgO; Nickel base alloys; Nickel compounds; Other topics in materials science; Physics; Random access memory; Tantalum; Temperature; Thermal stability; Tunneling; Tunneling magnetoresistance
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2007.894205

The capping effects on the properties of magnetic tunneling junctions (MTJs) have been investigated to improve the magnetoresistive (MR) ratio [Nagamine , Applied Physics, vol. 99, p. 08K703, 2006] and thermal stability [Fukumoto , Japanese Journal of Applied Physics, vol. 45, p. 3829, 2006. In this paper, MgO/Mg and MgO capping layers for MTJs were used to replace our previously used Ta and Ru capping layer [Yen , IEEE Transactions on Magnetics, vol. 42, no. 10, p. 862, 2004]. The MTJs with NiFe and CoFeB free layers were patterned to ellipses of 0.36 mum times 0.72 mum. The MR ratios of the MTJs with an NiFe free layer were enhanced from 26% to about 33% by capping MgO/Mg bilayers. A great improvement was also found on the MTJs with the CoFeB free layer, where the MR ratio was 50.4% with the MgO cap layer enhanced from 44.7% of Ru-capped MTJs. In addition, the influences of those capping layers included Ta, Ru, MgO, and MgO/Mg on thermal stability were also discussed