Downstream electron cyclotron resonance H2 plasma etching of native silicon oxide was studied in a multichamber integrated cluster tool. H (656.3 nm), OH (306.4 nm), SiO (266.9 nm), SiH (412.8 nm) and Si (288.2 nm) emission lines were monitored and correlated with surface atomic O/Si ratios measured by in situ x-ray photoelectron spectroscopy. Two distinct regimes of oxide etching were observed by plasma emission with the removal of the interfacial oxide to be four times slower than the bulk oxide. Concentration of H, OH, SiO radicals, native oxide etch rate, and ion density near the surface were maximized at 2.5 mTorr, which confirms that the downstream plasma process is driven by an ion-assisted removal mechanism. The ion density varies from 7.5 to 0.6×1010 cm−3 at a distance from substrate of 20 and 1.5 cm, respectively.