Oxidation of tunnel barrier metals in magnetic tunnel junctions

J. Joshua Yang, Peter F. Ladwig, Ying Yang, Chengxiang Ji, Y. Austin Chang, Feng X. Liu, Bharat B. Pant, Allan E. Schultz

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

The oxidation of an ultrathin metal layer (<1 nm) to form an oxide tunnel barrier is of critical importance for the fabrication of magnetic tunnel junctions (MTJs) with low product of resistance and area (R×A). Nonuniform and excessive or insufficient oxidation will occur by using conventional plasma, air, or O2 and noble gas mixtures as oxidation methods. An oxidation method was investigated to oxidize only an ultrathin layer of metal (such as Y) without oxidizing adjacent ferromagnetic thin film layers. We have now demonstrated that a gas mixture of H2 O H2 with a fixed chemical potential of oxygen determined by the relative amounts of the two gases can oxidize Y and Ta thin layers while simultaneously keeping a Co ferromagnetic layer completely unoxidized. This universal method can be used to preferentially oxidize a host of other metals with high tendency to form oxides, such as Zr, Hf, Nb, rare earth metals, etc. and may allow us to access the feasible lower limit of barrier thickness in MTJs.

Original languageEnglish
Article number10C918
JournalJournal of Applied Physics
Volume97
Issue number10
DOIs
StatePublished - May 15 2005
Externally publishedYes

Funding

This work was supported by a grant from the Division of Materials Science, Office of Basic Energy Research of Department of Energy under Grant No. DE-FG02-99ER45777, Seagate Technology, and the Wisconsin Distinguished Professorship.

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