Post deposition annealing effects on the reliability of ALD HfO₂ films on strained-Si_0.8Ge_0.2 layers

摘要

The reliability of strained-Si_0.8Ge_0.2 and Si MOS devices with HfO₂ gate dielectrics prepared by atomic layer deposition (ALD) is investigated. The observed HfO₂/semiconductor interfacial layer is silicate-like at low annealing temperature (∼600° C) and SiO₂-like at high annealing temperature (900° C). The quality of HfO₂/SiGe interface is slightly inferior as compared to the HfO₂/Si interface, due to the elemental Ge at the interface. The reliability characteristics for both the HfO₂/Si and HfO₂/Si_0.8Ge_0.2 structures are improved by increasing the PDA temperature up to 800° C, due to the thicker interfacial oxide layer grown at the interface. However, with higher PDA temperature (∼800° C), serious crystallization of HfO₂ film leads to more bulk traps induced electrical degradation.