Optimization of a three-electrode electrochemical etch-stop process

An accurate method to define three-dimensional (3D) microstructures is the electrochemically controlled etching (ECE) process of an epitaxial silicon wafer in anisotropic etchants. In this paper, a study of the temperature and concentration influence of the anisotropic etchant (KOH) on the passivation potential (PP) and passivation current density (j(pass)) is presented. The dependence of j(leak) through the reverse-biased junction between the epilayer and the substrate on the resistor diffusion depth has been studied. The results have been applied to optimize a three-electrode ECE process. In this way, 15 mu m thick membranes have been obtained with 3 mu m depth previously diffused resistors. (C) 1997 Elsevier Science S.A.