Elimination of boundary effect in silicon electrochemical etching via mechanical stress

Application of thick macroporous silicon is always one of the hotspots in electrochemistry including micromachining and chemical sensing. One serious problem in macropore formation with high depth-width ratio is the boundary effect. In this work, we applied mechanical stress onto the boundary region of electrochemical etching, which helps to passivate the sidewall of macropore in boundary area, and therefore eliminate the boundary effect effectively. The CBM model was employed to explain the mechanism. Thick macroporous layers without boundary effect were successfully produced in both n-type and p-type silicon.