Improvement of the Anneal-Induced Valence Band Offset Variation by the Hybrid Deposition of ${\rm HfO}_{2}$ 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 ${\rm HfO}_{2}$ 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 ${\rm H}_{2}{\rm O}$ and ozone as oxygen source during the deposition of ${\rm HfO}_{2}$ film. X-ray photoelectron spectroscopy shows that the VBO of this hybrid-fabricated film changes as little as 0.02 eV after a 600 $^{\circ}{\rm C}$ anneal, which is compatible with the gate-last process. The improved stability is further confirmed by the $V_{\rm FB}$ extracted from the C–V measurement. The physical processes that may be responsible for this improvement are discussed.