Breakdown spots of ultra-thin (EOTÂ <Â 1.5Â nm) HfO2/SiO2 stacks observed with enhanced-CAFM

In this work, the (gate) current versus (gate) voltage (I-V) characteristics and the dielectric breakdown (BD) of an ultra-thin HfO2/SiO2 stack is studied by enhanced conductive atomic force microscopy (ECAFM). The ECAFM is a CAFM with extended electrical performance. Using this new set up, different conduction modes have been observed before BD. The study of the BD spots has revealed that, as for SiO2, the BD of the stack leads to modifications in the topography images and high conductive spots in the current images. The height of the hillocks observed in the topography images has been considered an indicator of structural damage.