ETCHING PROCESSING OF SI(111) AND SI(100) SURFACES IN AN AMMONIUM FLUORIDE SOLUTION INVESTIGATED BY IN-SITU ATR-IR

In situ real-time measurements of etching processes by infrared total reflection spectroscopy were carried out for the first time on Si(lll) and Si(100) surfaces in ammonium fluoride solution. The absorption ba nds became broad by the interaction between terminal hydrides with wat er molecules. On Si(lll), the band at 2083 cm(-1) continuously grew an d was sharpened by the formation of monohydride on the ideal Si(lll) w ith the decrease of defects. On Si(100), dihydride first appeared, whi ch was subsequently replaced by monohydride on steps produced as a res ult of etching. The stepped surface was continuously etched, and dihyd ride on Si(100) again increased with pyramid-like protrusions having ( 111) facets with many steps. The pyramids kept growing at the expense of dihydride to be the dominant structure on the surface.