Monitoring of the formation and removal of bulk, surface, and interfacial carrier traps on silicon(100)

An RF probe was used to monitor the steady-state photo-generated carrier concentration in silicon with and without an oxide layer. The changes in this steady-state concentration during exposure to gaseous molecular and atomic species such as He, H-2, O-2, H, and O at temperatures between 25 and 450 degrees C are interpreted in terms of changes in the bulk silicon, interface, and exposed surface. The initial experiments established the relationship between the carrier concentration and the RF-probe signal, and distinguished between changes in the bulk, and on silicon surfaces and interfaces. It was found that in the case of hydrogen, bulk passivation and depassivation by H-2 can be observed only at elevated temperatures, with or without an oxide layer. H-atom depassivation can be observed at all temperatures and is irreversible at room temperature. The formation of an oxide layer by exposure to O atoms at 25 and 450 degrees C was followed, and the oxides formed were then treated in an attempt to create an SiO2/Si interface with an acceptable density of interfacial states.