The variation of hydrogen distribution at the SiO2/Si interface by low-temperature hydrogen annealing was investigated using secondary ion mass spectrometry (SIMS). As the amount of hydrogen atoms incorporated at SiO2/Si is considered to be comparable to the silicon dangling bond density (1 x 10(10) to 1 x 10(12) atoms/cm(2)), an analytical method with a high sensitivity is necessary for the detection of hydrogen at SiO2/Si. In this study, the experimental conditions of SIMS were optimized in order to obtain a sufficient reproducibility of interfacial hydrogen ion intensity. There are two main causes that influence the measurement reproducibility: (1) misalignment of the relative irradiation areas of the electron beam and ion beam and (2) the contribution of background hydrogen from surface contaminants and residual gas. We obtained a high measurement reproducibility within a 5.5% relative standard deviation (2sigma). This enabled us to observe an increase of hydrogen at SiO2/Si by hydrogen annealing at 400 degreesC, which resulted from the incorporation of hydrogen from the ambient. From the results of nuclear reaction analysis (NRA) and thermal desorption spectroscopy (TDS), it was also found that the incorporated hydrogen had two chemical states. (C) 2003 Elsevier Science B.V. All rights reserved.