TABLE OF CONTENTS MEMS devices and structures are fabricated using conventional integrated circuit process techniques, such as lithography, deposition, and etching, together with a broad range of specially developed micromachining techniques. Those techniques borrowed from the integrated circuit processing industry are essentially two dimensional, and control over parameters in the third dimension is only achieved by stacking a series of two-dimensional layers on the workpiece, which is usually a silicon wafer. There are practical and economic limits, however, to the number of layers that can be managed in such a serial process, and therefore, the expansion of devices into the third dimension is restricted. Micromachining techniques enable structures to be extended further into the third dimension; however, it has to be understood that these structures are simply either extruded two-dimensional shapes or are governed by the crystalline properties of the material. True three-dimensional processing would allow any arbitrary curved surface to be formed, and this is clearly not possible with the current equipment and techniques. An important aspect of MEMS is to understand the limitations of the micromachining techniques currently available. Although the range of these techniques is continually being expanded, there are some core techniques that have been part of the MEMS toolkit for many years. This chapter deals mainly with these core techniques, but also with those process techniques borrowed from integrated circuit manufacturing.
Just as silicon has dominated the integrated circuit industry, so too is it predominant in MEMS. There are a...
