Analysis of oxide-nitride-oxide/Si(111) interfaces by optical second harmonic generation and secondary ion mass spectroscopy

We use optical second harmonic generation and secondary ion mass spectroscopy (SIMS) to study oxide-nitride-oxide (ONO)/Si(111) interfaces. We explain the relationship between the second harmonic (SH) intensity from the interfaces and the SIMS depth profiles. The intensity from the wet oxide/Si(111) interface decreases as the temperature during wet oxidation increases, because the number of interface dangling bonds is reduced as the wet temperature is increased. With subsequent nitridation, this SH intensity of the oxidized interface decreases. This is because hydrogen and nitrogen terminate the interface dangling bonds. However, the SH intensity increases again with reoxidation, because the dangling bonds grow again at the interface. The SH intensity from annealed nitridation of the oxide/Si(111) interface remains constant, although the number of hydrogen atoms decreases and the number of nitrogen atoms slightly increases. We propose two reasons for this. One is that most of the desorbed hydrogen atoms do not terminate the dangling bonds at the interface. The other is that interface dangling bonds grow temporarily due to desorbed hydrogen; however, nitrogen piled up near the interface terminates them again. (C) 1996 American Institute of Physics.