Interface characterization and carrier transportation in metal/HfO2/silicon structure

Metal-oxide-semiconductor capacitors incorporating HfO2 dielectrics were fabricated and investigated. In this work, the structural and electrical characterizations were performed at the interfaces of HfO2∕Si and Al∕HfO2, respectively. The physical analyses reveal that an interfacial layer of Hf-silicate between 700°C-annealed HfO2 and Si was formed. The dominant conduction mechanisms of the Al∕HfO2∕p-Si structure are the Schottky emission at high temperatures (≳465K) and low electric fields (≲2.2MV∕cm) and the Fowler-Nordheim tunneling at low temperature (77K) and high electric fields (≳2.6MV∕cm), respectively. The electron effective mass in HfO2 and the barrier height at the Al∕HfO2 interface are evaluated using both the intercept of the Schottky plot and the slope of the Fowler-Nordheim plot. Therefore, the barrier height at the Al∕HfO2 interface was determined to be about 0.94eV. The electron effective masses in HfO2 are 0.4m0 and 0.09m0 for the effective oxide thickness (EOT)=6nm and EOT=3.15nm, respectively.