2. An Overview of MEMS Microsystems

Chapter 2 provides a foundation for future chapters and begins with a review of the transduction mechanisms most commonly used in the implementation of MEMS microsensors and microactuators. Among the transduction effects covered includes piezoresistive; capacitive; piezoelectric; tunneling; magnetic; photoconduction; thermoelectric; electrostatic; thermal; shape-memory alloy; and others. The differences between a processing step; a process module; a process sequence; and a process technology are then described. The concept of batch fabrication is explained including the significant benefits that are derived from the use of this manufacturing method. Some of the important distinguishing characteristics of MEMS fabrication compared to IC manufacturing are reviewed, and reasons why MEMS is both more interesting and challenging compared to IC manufacturing are given. Specifically it is noted that MEMS design is very interesting since the number of device types and potential application areas is enormous. Nevertheless, MEMS implementation usually involves significant customization of both the design and the process sequence, and therefore the device designer often does not have much prior knowledge to leverage from. Lastly, a review of some of the basics about semiconductor materials, which are heavily used in MEMS manufacturing, is provided. Miller indices are explained as part of this discussion.