Effects of sulfur passivation on germanium MOS capacitors With HfON gate dielectric

Abstract

In this letter, we study the effects of sulfur (S) passivation, using aqueous ammonium sulfide ((NH4)2), on germanium (Ge) MOS capacitors with sputtered HfON as gate dielectric and TaN as metal-gate electrode. Compared with control samples, the S passivation can effectively reduce both equivalent oxide thickness and interface-state density. X-ray-photoelectron-spectroscopy analysis shows that (NH4)2S treatment can reduce the Ge-O bonds on Ge surface. The thermal stability of the S passivation under different postmetal-annealing temperatures was also examined, and it was found that samples with (NH4)2S treatment exhibit stable Ge/high-k interface upon 550-°C postmetal-deposition annealing, whereas interface quality degrades for those samples without S passivation. © 2007 IEEE.