Silicon Micromachining Based on Surfactant-Added Tetramethyl Ammonium Hydroxide: Etching Mechanism and Advanced Applications

Abstract

This paper presents the mechanism behind the accused macroscopic changes in the etched profiles and etch rates caused by the addition of small amounts of surfactants (e.g., Triton X-100) in typical alkaline etchants (e.g., tetramethylammonium hydroxide or TMAH) for silicon micromachining applications targeting the fabrication of microelectromechanical systems (MEMS). In order to stress the technological importance of the surfactant addition in TMAH, the paper presents an overview of novel fabrication methods for the realization of new fixed and freestanding structures in Si{100} wafers using an inexpensive combination of wet anisotropic etching in pure and surfactant-added TMAH. The fixed structures contain perfectly sharp edges and a smooth etched surface finish. Thermally deposited oxide is used as the material for the freestanding structures. The fixed structures serve as molds for the realization of new structural shapes using poly(dimethylsiloxane) (PDMS).