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

Abstract

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, H2, O2, H, and O at temperatures between 25 and 450 °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 H2 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 °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.