CAD for silicon anisotropic etching : Effect of etching products and diffusion

Recently, an anisotropic etching simulation program for silicon based on the Wulff-Jaccodine graphical method has been successfully developed. The experimentally measured distribution of etch rates for all crystallographic orientations is required for this program. In this study, the dependence of etching rates on the amount of dissolved silicon and on resulting changes in pH and conductivity of tetramethyl ammonium hydroxide (TMAH) etchants was investigated. The experimental results strongly suggested that the products formed during the etching reaction affect the etching characteristics. Next, an etching experiment using a small etching hole was carried out to investigate the diffusion effect. The results suggested that the influence of diffusion should also be taken into account in the simulation program. Finally, an idea for a simulation program based on a graphical approach combined with the physics of atomic-scale phenomena is proposed to take the effects of etching parameters such as additives, etching products and diffusion into account.