Electrochemical etch stop engineering for bulk micromachining

Abstract

Microelectromechanical systems (MEMS) may be fabricated with several micromachining techniques, the oldest and most widespread technique being 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 with a uniform thickness. Recently, new etch stop techniques based on galvanic element formation in an alkaline etchant have been reported. Galvanic element formation has been observed earlier, though the concept never received much attention in the literature on bulk-micromachining. This paper discusses the theory of electrochemical etching and galvanic element formation in a wet etchant in general and also its applications to etch stop engineering for bulk-micromachining.