A short post-processing method for high aspect ratio trenches after Bosch etching

An in-situ O2 plasma is often used for cleaning high aspect ratio Si structures (AR = 35) which are Bosch-etched. During the cleaning process a SiOx layer is formed, which could be a problem for further processing. A vapor HF step is introduced to remove the SiOx layer uniformly in structures with an aspect ratio of 35 and to obtain a well-defined Si surface again.