RIE-induced damage and contamination in silicon

Abstract

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