Initial pits for electrochemical etching in hydrofluoric acid

This paper reports on a characterization of structures fabricated by electrochemical etching in hydrofluoric acid (HF) using different types of initial 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 crystal orientation dependence. We successfully demonstrate the structures fabricated by the electrochemical etching with the initial pits, which have flat or round base. These pits are: formed by isotropic wet etching or reactive ion etching (RIE), which are free from crystal orientation of silicon substrate. Furthermore, regular hole patterns can be achieved without initial pits. This makes the electrochemical etching process mon simple. The electric field in the silicon is calculated and the calculated results support the experimental results. (C) 2000 Elsevier Science S.A. All rights reserved.