Improved anisotropic deep etching in KOH-solutions to fabricate highly specular surfaces

We report on an improved standard etching method to fabricate deep etched < 100 > -oriented Silicon surfaces with a mirrorlike finish. It is shown that the addition of minimal quantities of an antimony or arsenic compound (in the mmol range) to a 40% wt. KOH-solution has a deep impact on the etching characteristics of single crystalline silicon. The compounds undergo reduction to the elements at the silicon surface and form covalent bonds to the substrate. As etching proceeds, a film of the elements Sb or As floats on the surface, changes the oxidation/dissolution behavior of the silicon and finally leads to surfaces with an rms roughness of below 2 nm. (C) 2001 Elsevier Science BY All rights reserved.