Although a microscopic study on a MgO tunnel barrier by atomic force microscopy has been required to study the reliability of magnetic tunnel junctions, the deterioration of bare MgO due to the adsorption of H2O and CO2 has been a problem. For an accurate evaluation of the initial current leakage spots distributed in a MgO tunnel barrier, a CoFeB-capped MgO tunnel barrier structure is proposed for evaluation by means of conductive atomic force microscopy. The CoFeB capping layer thickness was optimized to be 2.0nm to prevent H2O and CO2 adsorption on the MgO and to minimize the series resistance due to the capping layer. The initial current leakage spot density of the MgO tunnel barrier with the optimized CoFeB capping layer exponentially increased as the thickness of the MgO tunnel barrier decreased from 1.6 to 0.8nm, and was 157 spots/μm2 at the MgO thickness of 1.2nm and the bias voltage of 0.5V.
ASJC Scopus subject areas
- Physics and Astronomy(all)