Behavior of germanium ion-implanted into SiO2 near the bonding interface of a silicon-on-insulator structure

The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator structures are studied. It is shown that, under conditions of high-temperature (1100 deg. C) annealing, germanium nanocrystals are not formed, while the implanted Ge atoms segregate at the Si/SiO2 bonding interface. It is established that, in this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. In this situation, the main type of traps is the positive-charge traps; their effect is interpreted in the context of an increase in the surface-state density due to the formation of weaker Ge-O bonds. It is found that the slope of the drain-gate characteristics of the back MIS transistors increases; this increase is attributed to an increased mobility of holes due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface