Simultaneous control of the work function and interfacial oxide thickness using NiHf stacked electrode on HfO₂

Both work function and interfacial oxide thickness control were attempted using NiHf bilayered metal electrode on HfO₂. The flatband voltage, directly related to the work function, with an approximate span of 1 V could be controlled by changing the Hf thickness. The interfacial oxide thickness was decreased with increasing the Hf thickness due to the high reducing capability of the Hf film, and the interface state density was reduced. However, Hf films thinner than 2 nm were needed to avoid the leakage current degradation caused by the diffusion of metallic Hf into the HfO₂ during postdeposition annealing.