Direct evidence of GeO volatilization from GeO2/Ge and impact of its suppression on GeO2/Ge metal-insulator-semiconductor characteristics

From the studies on the thermal desorption behaviors of GeO2 film and its impact on the electrical properties of GeO2/Ge metal-insulator-semiconductor (MIS) capacitors, it was clarified that the GeO volatilization is driven by the interface reaction at GeO2/Ge, and that volatilization is the origin of the interface deterioration of the MIS capacitors. We found that a Si cap layer formed on top of the GeO2 film suppresses the GeO desorption very efficiently. Then, a marked improvement of the capacitance-voltage (C-V) characteristics was successfully demonstrated with the GeO2/Ge MIS capacitors fabricated by capped annealing process, where a Ni silicide electrode was used as the cap layer. These results provided us quite an important guide for realizing high-quality Ge/dielectric interfaces.