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.