Study of dielectric breakdown distributions in magnetic tunneling junction with MgO barrier

The breakdown distribution of a magnetic tunnel junction (MTJ) with an ultrathin (similar to 1.2 nm) MgO barrier was studied, and two distinct distributions were identified. The breakdown distribution with high value demonstrates a wide peak-to-peak separation (similar to 13.4 sigma) to the critical spin torque induced switching voltage. However, the peak-to-peak separation is only similar to 8.4 sigma for the devices showing low breakdown value. Both abrupt and gradual breakdown events were observed in two distributions. The dependence of the percentage of low breakdown devices as a function of bias polarity, test and stress conditions, MTJ film properties, and process conditions was investigated. The low breakdown percentage can be significantly reduced by increasing the RA value and MTJ process optimization. (C) 2009 American Institute of Physics. [DOI: 10.1063/ 1.3074508]