Electrochemical Micromachining as an Enabling Technology for Advanced Silicon Microstructuring

Based on previous theoretical and experimental results on the electrochemical etching of silicon in HF‐based aqueous electrolytes, it is shown for the first time that silicon microstructures of various shapes and silicon microsystems of high complexity can be effectively fabricated in any research lab with sub‐micrometer accuracy and high aspect ratio values (about 100). This is well beyond any up‐to‐date wet or dry microstructuring approach and is achieved using a wet etching, low‐cost technology: silicon electrochemical micromachining (ECM). Dynamic control of the etching anisotropy (from 1 to 0) as the electrochemical etching progresses allows the silicon dissolution to be switched in real‐time from the anisotropic to the isotropic regime and enables advanced silicon microstructuring to be achieved through the use of high‐aspect‐ratio functional and sacrificial structures, the former being functional to the microsystem operation and the latter being sacrificed for accurate microsystem fabrication. World‐wide dissemination of the ECM technology for silicon microstructuring is envisaged in the near future, due to its low cost and high flexibility, with high‐potential impact on, though not limited to, the broad field of microelectronics and microfabrication. The advanced fabrication of silicon microstructures of various shapes and silicon microsystems of high complexity using electrochemical micromachining (ECM) technology is described. ECM technology makes use of a dynamic control of the electrochemical etching anisotropy, which allows silicon dissolution to be switched in real‐time from the anisotropic to the isotropic regime, to enable the low‐cost fabrication of microstructures and microsystems using both functional and sacrificial structures.