Crystal orientation dependence of macropore growth in n-type silicon

The dependence of macropore formation in n-silicon on substrate orientation was investigated. Samples were cut from a large Si crystal in various orie ntations between {100} and {111}. Macropores were obtained by electrochemic al etching in diluted HF following standard techniques. The growth directio n of the macropores was found to be <100> and <113>, with a switch over at a critical angle of about 43 degrees, whereas "break-through" pores obtaine d without illumination at large field strength always grow in <100>. The re sults can be partially understood by postulating different pore growth spee ds for <100> and <113>, but indicate that a detailed understanding of pore growth in Si is still elusive. (C) 1999 The Electrochemical Society. S1099- 0062(98)09-062-2. All rights reserved.