Study of silver diffusion into Si(111) and SiO2 at moderate temperatures

Diffusion of Ag from epitaxial layers into Si(111) is studied under an anneal of 450–500 °C using the secondary ion mass spectrometry depth profiling tool. The measurements yielded values of the diffusion constant (0.80–1.6 × 10−15 cm2/s) which fall short of literature values extrapolated from higher-temperature Arrhenius laws. Diffusion of Ag into SiO2 was also measured directly. The observed diffusivity of 1.0 × 10−15 cm2/s is a factor of ∼ 105 smaller than expected from previous determinations of the diffusivity of Ag+ in SiO2 obtained from anneals in forming gas. The discrepancy may be due to changes in the local electrostatic environment in the absence of acceptor levels in SiO2 from dissolved gases which are absent in vacuum.