Surface Micromachining—Advances and Advanced Characterization Techniques

Surface being the outermost layer of a body is the first point of contact between a body and the environment in which it is intended to work. By modifying the surface properties, the characteristics exhibited by a material can be controlled. With the need for reducing the structure sizes for different applications, the conventional machining has been scaled down to micromachining in which micro tool is used and micron-sized structures are created. Among the different types of micromachining techniques, surface micromachining stands out as a process which is intended only for the surface of a workpiece. In contrast to other micromachining techniques which target the bulk of the workpiece, surface micromachining aims at creating patterns, structures or features on the surface of the workpiece thus inducing unique and controllable properties. This chapter discusses different micromachining techniques and methods of characterization. The first section will include brief introduction to well-known processes like photolithography, reactive ion etching, deep reactive ion etching; some advanced processes capable of micron as well as nanometric scale fabrication like focused ion beam fabrication, electron beam lithography. Almost all these techniques are physical in nature, as in they do not involve use of chemical etching for creating the surface structures. Thus, they enable one to achieve high level of accuracy in the process and to actively control the features of the structure. As the fabrication methods have evolved with time, so did their characterization methods. Conventional measurement techniques are not suitable for evaluating the structures fabricated by the advanced surface micromachining methods. The second section of the chapter discusses three measurement and characterization methods. First of which is stereo zoom microscope which is used mostly at macro scale, followed by scanning electron microscopy which is capable of operating at micron and nanometric scale. The last of the characterization methods is scanning tunneling microscopy which is capable of imaging and characterization at atomic scale.