Initial pits for electrochemical etching in hydrofluoric acid

This paper reports on a characterization of structures fabricated by electr ochemical etching in hydrofluoric acid (HF) using different types of initia l pits. An initial pit has been thought to require a sharp tip in order to collect electronic holes generated by illumination. Therefore, the initial pits have been formed by etching in a KOH solution, which suffers from crys tal orientation dependence. We successfully demonstrate the structures fabr icated by the electrochemical etching with the initial pits, which have fla t or round base. These pits are: formed by isotropic wet etching or reactiv e ion etching (RIE), which are free from crystal orientation of silicon sub strate. Furthermore, regular hole patterns can be achieved without initial pits. This makes the electrochemical etching process mon simple. The electr ic field in the silicon is calculated and the calculated results support th e experimental results. (C) 2000 Elsevier Science S.A. All rights reserved.