Micromachining technology

Abstract

The term micromachining usually refers to the fabrication of micromechanical structures with the aid of etching techniques to remove part of the substrate or a thin film. Silicon has excellent mechanical properties,[1] making it an ideal material for machining. An early silicon (pressure) sensor was made by Honeywell in 1962 using isotropic etching.[2] In 1966, Honeywell developed a technique to fabricate thin membranes using mechanical milling. Crystal-orientation-dependent etchants led to more precise definition of structures and increased interest.[3] Anisotropic etching was introduced in 1976. An early silicon pressure sensor, based on anisotropic etching, was made by Greenwood in 1984.[4] Surface micromachining also dates back to the 1960s. Early examples included metal mechanical layers.[5] Basically, surface micromachining involves the formation of mechanical structures from thin films on the surface of the wafer. The 1980s saw the growth of silicon-based surface micromachining using a polysilicon mechanical layer.[6,7] In recent years, a number of new technologies have been developed using both silicon and alternative materials. These include the epi-processes where the epilayer is used as a mechanical layer and a number of deep plasma etching processes. This chapter concentrates on silicon-based micromachining processes. © 2006 Springer-Verlag Berlin Heidelberg.