A Quick Overview of Micromachining for MEMS Designers

0. Introduction Micromachining techniques have been developed on the basis of the microelectronic fabrication technology. Microfabrication is a generic term that is also used to imply micromachining. What makes micromachining different from microelectronic fabrication technology is the need to have a released mechanical structure that can move either like a rigid body (as in translation, rotation, or combination thereof) or like a flexible body by undergoing substantive deformations. In order to understand the physics and chemistry of micromachining thoroughly, one needs to have a reasonable knowledge of microelectronic fabrication. Except the small subset of electrical engineers, most others usually lack that knowledge. The purpose of this overview of micromachining is to provide a conceptual understanding of micromachining without having to know too much about the physics and chemistry of it. The emphasis is on the techniques used and how each technique modifies the geometry of materials processed during micromachining. We also need to know about the generic MEMS materials and their properties. Some terms will also be defined along the way so that we can try to understand a description of the microfabrication given in the MEMS literature and we will be able to visualize the process flow geometrically and verbalize process steps from a given cross-section of a finished MEMS component or a product. This is very useful when we design MEMS devices. The premise for this overview of micromachining and MEMS materials is as follows. A designer has control over the selection of materials and the shapes of parts in a designed entity. But manufacturing has control over what materials can be processed into what shapes. Therefore, a designer must adhere to the capabilities and limitations of the available manufacturing techniques. Thus, a MEMS designer too should be aware of what materials are at one’s disposal and what shapes can be achieved with them.