Bimodal CAFM TDDB distributions in polycrystalline HfO2 gate stacks: The role of the interfacial layer and grain boundaries

Dielectric breakdown (BD) in polycrystalline HfO2/SiO2 gate stacks has been studied using a conductive atomic force microscopy (CAFM) technique, which allows employing a nanosize probe to apply a highly localized electrical stress. The resulting BD statistics indicate that BD preferentially occurs in the interfacial SiO2 (IL) layer beneath the grain boundaries (GBs) of the overlaying polycrystalline HfO2 film due to higher conductivity of the GB compared to that of the grains.