Improvement of the Anneal-Induced Valence Band Offset Variation by the Hybrid Deposition of HfO2 on Si.

Controlling threshold voltage variation during fabrication is essential, and one source for the variation is the thermal instability of valence band offset (VBO) for HfO2 deposited on Si. It has been reported that VBO can be changed as much as 0.33-0.60 eV after annealing. This paper proposes a hybrid process with both H2O and ozone as oxygen source during the deposition of HfO2 film. X-ray photoelectron spectroscopy shows that the VBO of this hybrid-fabricated film changes as little as 0.02 eV after a 600 °C anneal, which is compatible with the gate-last process. The improved stability is further confirmed by the VFB extracted from the C-V measurement. The physical processes that may be responsible for this improvement are discussed. [ABSTRACT FROM AUTHOR]