BULK MICROMACHINING OF SILICON

Bulk silicon etching techniques, used to selectively remove silicon fr om substrates, have been broadly applied in the fabrication of microma chined sensors, actuators, and structures. Despite the more recent eme rgence of higher resolution, surface-micromachining approaches, the ma jority of currently shipping silicon sensors are made using bulk etchi ng. Particularly in light of newly introduced dry etching methods comp atible with complementary metal-oxide-semiconductors, it is unlikely t hat bulk micromachining will decrease in popularity in the near future . The available etching methods fall into three categories in terms of the state of the etchant: wt, vapor, and plasma. For each category, t he available processes are reviewed and compared in terms of etch resu lts, cost, complexity, process compatibility, and a number of other fa ctors. In addition, several example micromachined structures are prese nted.