ELECTROCHEMICAL ETCH-STOP ENGINEERING FOR BULK MICROMACHINING

Microelectromechanical systems (MEMS) may be fabricated with several m icromachining techniques, the oldest and most widespread technique bei ng that of bulk-micromachining. Although there are alternative etching techniques, wet anisotropic etching is still favoured by industry in many cases because of its simplicity and low costs. Electrochemically controlled etching allows for reproducible fabrication of structures w ith a uniform thickness. Recently, new etch stop techniques based on g alvanic element formation in an alkaline etchant have been reported. G alvanic element formation has been observed earlier, though the concep t never received much attention in the literature on bulk-micromachini ng. This paper discusses the theory of electrochemical etching and gal vanic element formation in a wet etchant in general and also its appli cations to etch stop engineering for bulk-micromachining. (C) 1998 Els evier Science. All rights reserved.