Wet refinement of dry etched trenches in silicon

Deep trenches were etched in single‐crystalline silicon for isolation purposes using combined dry‐wet processing. Reactive ion etching was performed in chlorine‐nitrogen plasmas using chloroform, boron trichloride, or sulfur hexafluoride additives to optimize the trench profile. In all cases, however, imperfections such as barreling or micromasking‐induced trench bottom residue remained after dry etching. A significantly improved profile was obtained with the aid of an additional wet treatment of the dry etched trenches in tetramethyl ammonium hydroxide.