Dielectric breakdown of lithographically patterned tunnel junctions prepared by UV oxidation method

Future magnetoresistive random access memories will require a vast matrix o f reliable magnetic tunnel junctions. Therefore, the time-dependent dielect ric breakdown of lithographically defined Co/Al2O3/Ni80Fe20 tunnel junction s, oxidized using an ultraviolet light-assisted oxidation process in O-2, w as investigated by means of voltage ramp experiments on a series of pattern ed junctions with different area. As the applied voltage approaches 2 V, al most immediate breakdown of the junction is observed. This leads to an irre versible decrease of the junction resistance by more than 90%, For smaller tunnel junctions, a larger breakdown voltage was measured which confirms th e statistical origin of the breakdown phenomenon. (C) 2000 Elsevier Science B.V. All rights reserved.