Fabrication of free standing structure using single step electrochemical etching in hydrofluoric acid

This paper presents a new technique of micromachining using single step ele ctrochemical etching in hydrofluoric acid (HF). The electrochemical etching in HF is known as a technique for porous silicon formation. This etching t echnique is applied to fabricate 3-D structures in single crystal silicon b y a combination of anisotropic and isotropic modes. The diameter of the por e, or the width of the trench, can be controlled by the current density. Fi rst, vertical walls are formed and after desired depth is obtained, current density is increased by adjusting the light intensity. The width of the tr enches is increased under the structures without affecting the width of exi sting trenches. The connection of the trenches can be achieved and free sta nding beams obtained with only one mask. The free standing beams with heigh t, width and length of 40 mu m, 2 mu m and 250 mu m, respectively, have bee n made of single crystal silicon. (C) 1999 Elsevier Science S.A. All rights reserved.