HfO2 Gate Stack Engineering by Post-Gate Cleaning Using NF3/NH3 Plasma

Abstract

In this paper, we present preliminary findings on the fluorine incorporation into the HfO2 gate stack using post-gate dry cleaning technique with the novel NF3/NH3 plasma as an engineering technique to improve the HfO2 gate stack. The NF3/NH3 dry cleaning process was carried out using an indirect down-stream CCP system after annealing HfO2 gate stack. The analysis of chemical composition of HfO2 gate stacks by XPS has been revealed that fluorine was incorporated into the HfO2 films and Si-O bonding of interfacial layer was decreased depending on the process condition of the NF3/NH3 dry cleaning. TEM results consistently showed the interfacial SiOx layer thickness of the HfO2 gate stack was decreased with the NF3/NH3 dry cleaning. Also we have found that its electrical properties were improved with the reduced gate leakage currents and EOT.