Initial stage of hydrogen etching of Si surfaces investigated by infrared reflection absorption spectroscopy

The initial stage of etching reactions (breaking the Si-Si back bonds) of S i(100) and Si(111) surfaces exposed to hydrogen at room temperature was inv estigated by buried metal layer-infrared reflection absorption spectroscopy . The peaks of SiH2 scissors and SiH3 deformation modes (<1000 cm(-1)) were successfully observed as clear indicators of the initial stage of hydrogen etching reactions. On the Si(100) surface. the hydrogen exposure dependenc e of these peaks indicated that the etching reaction stal ts in the relativ ely low-exposure region of <greater than or equal to>300L (1 L = 1 x 10(-6) Torr s). We found that the adjacent dihydride is a precursor to breaking t he Si back bonds. On the Si(111) surface, it was found that the adatom's tw o back bonds are easily broken, and that adatom trihydride is generated at a low H-exposure of 70-500 L. Adding to this dominant reaction, the etching of the rest-atom layer was observed at H-exposures higher than 10000 L.