6.1 Introduction

Micromachining technology manufactures microdevices by implementing features in bulk materials such as silicon, quartz, SiC, GaAs, InP, Ge and glass. The features are implemented through several processes. One of the important sub-processes in micromachining is etching, which means the removal of selective materials. Etching is performed either on the substrate or on a preferred material layer deposited on the substrate. The very meaning of substrate (also called wafer) is the material upon or within which plants or animals live, however, in the context of microsystems, MEMS (Microelectromechanical Systems) components (also called features) and circuitry are used. In essence, a substrate is a sheet of base material in which mechanical parts, electronic components and integrated circuits (IC) are built by the process of etching. The etching process is used to remove a defined portion of the substrate in a particular manner so that the desired shape can be obtained. The process selectively removes material from the substrate. The material to be removed is determined by the etching solution (called etchanf). Fig. 6.1 provides an insight into the etching process. Some typical structures such as plates, steps, grooves, cantilever, diaphragm, post, etc. can be fabricated or micromachined through etching. For...