RIE-induced damage and contamination in silicon

Reactive ion etching always causes a dynamic radiation effect in crystalline silicon, because of the energetic particle bombardment. RIE induced radiation effects are mostly confined to the near surface within the projected range of the impinging ions, but point defects, which are highly mobile at room temperature, can migrate further into the bulk before a damaged surface layer is etched away. Competition between etch rates and damage rates ultimately determines the degree of RIE damage residue: the slower the etch rate, the heavier the damage which may be accumulated at the near surface, eventually leading to amorphization of the surface region. Also, removal of the surface layer due to etching or sputtering enhances the probability of a chemical reaction between the bare surface and incoming radicals. This may give rise to a serious surface contamination problem. Post-cleaning at a low temperature is highly desirable whenever the surface of active devices are exposed to reactive plasmas. (author)