Impact of Al2O3 position on performances and reliability in high-k metal gated DRAM periphery transistors

Abstract

The impact of the Al₂O₃ position with respect to HfO₂ in the process flow, is investigated. It is shown that Al₂O₃ incorporation in order to increase the pMOS threshold voltage, slightly degrades the mobility, slightly increases NBTI and increases the EOT with respect to the reference without Al₂O₃ Moreover, the trap density profiles depend on the Al₂O₃ position: higher in the interfacial layer when Al₂O₃ is below and higher in the HfO₂ when Al₂O₃ is above HfO₂. Furthermore, Al₂O₃ below HfO₂ shows higher gate leakage, reduced LF noise but marginal NBTI difference compared to AL₂O₃ above HfO₂.