Nuclear reaction analysis of hydrogen migration in silicon dioxide films on silicon under 15N ion irradiation

Abstract

Hydrogen concentration profiles in wet, thermally grown SiO 2/Si layer structures were measured using the 15N nuclear reaction analysis (NRA) method: the measured hydrogen concentration in the SiO 2 layer is initially about 2.2×10 20 cm −3 and almost constant throughout the SiO 2. For the NRA measurement of the initial H-profile a low dose of 15N ions has been taken in order to minimize a change in the profile by the NRA measurement itself. After high dose 15N ion irradiation an accumulation of hydrogen in the SiO 2/Si transition region (called interface) is observed together with a loss of hydrogen through the surface. SiO 2/Si structures with a SiO 2 film thickness of 32, 92 and 173 nm were investigated. A rapid initial increase of the H concentration in the transition region with increasing irradiation fluence is observed for all three samples. In the 32 and 92 nm samples prolonged irradiation leads to a subsequent reduction of the H concentration at the interface.