Properties of Ru/HfxSi1-xOy/Si metal oxide semiconductor gate stack structures grown by atomic vapor deposition

Capacitance-voltage characteristics of HfxSi1-xOy gate stacks with HfxSi1-xOy composition Hf/Si = 75/25 and Hf/Si = 50/50 were analyzed. The characteristics revealed a high density of negative fixed charges Nox = -5 X 1012 cm-2 in the oxide film. We have observed that the value of the Ru work function remained constant after forming gas annealing at temperatures between 430 and 510 deg C, respectively, while fixed charges were reduced at temperatures above 470 deg C. We speculated that the decrease of negative fixed charges can be explained by the generation of positively charged [Si2 = OH]+ centers in the oxide layer. The positively charged centers can account for a compensation of the negative fixed oxide charge. Rapid thermal annealing at temperatures up to 800 deg C in nitrogen did not influence the fixed oxide charges in the HfxSi1-xOy films.