Metal gate work function engineering using $AlNx$ interfacial layers

Metal gate work function enhancement using thin $AlNx$ interfacial layers has been evaluated. It was found that band edge effective work functions $(∼5.10eV)$ can be achieved on hafnium-based high dielectric constant (high-$k$⁠) materials using the $AlNx$ interfacial layer and TiSiN electrodes. It was also found that the effective work function enhancement by the $AlNx$ interfacial layer increased when the concentration of $SiO2$ in the gate dielectric was increased. Thus, the enhancement was minimal for $HfO2$ and maximum for $SiO2$⁠. A model is proposed to explain these results and a bonding analysis is presented to support the proposed model.