In this article, the underlying physical mechanisms of proton exchange (PE) in LiNbO3 with inductance coupled plasma (ICP) as proton source have been investigated according to quantitative calculations and simulations. It is shown that a high proton density layer near the sample surface acts as the source for proton diffusion. Experimentally, effects of parameters including working pressure, rf bias power, and ICP power are investigated by measurement of the PE depths with secondary ion mass spectrometry. And the variation of PE results has been linked to fundamental plasma characteristics such as ion density and ion flux through the variation in the measured dc self-bias values. A reproducible proton-exchange efficiency of 660 nm/h has been obtained at a relatively low sample temperature of 170 degrees C and working pressure of 8 mTorr, with high sample quality. (c) 2007 American Vacuum Society.