With the increased usage of microelectromechanical devices (MEMs) today, the use and design of systems to control and monitor such devices has become increasingly important. In interests of simplifying packaging and increasing yield, the possibility of putting such control and monitoring systems on chip with the micro-electromechanical machines is suggested as an elegant solution. Simplified scaling of the micro-electromechanical machine/circuit system as one can also be a benefit of this integrated process. This project integrates a basic n+ poly gate PMOS process with the additional steps necessary to create simple suspended polysilicon beam micromachines. These beams can be used as accelerometers. The circuitry integrated into the design is used to measure capacitance in the Femto farad range, and can be applicable to nearly any micro-machine that utilizes changes in capacitance for operation. While off-chip electronics are still necessary for this design to function completely, the completed process demonstrates the feasibility of a more complex version of the system for future fabrication. A layout was designed and a specialized photomask was made to test the circuitry. This layout contains a multipurpose micro-electromechanical structure, as well as a structure specifically designed as an accelerometer. Implementation of the fabrication process occurred in the clean room at Rochester Institute of Technology. The multipurpose structure utilized in the design can be used to test various basic properties of the polysilicon beams, including beam resonance frequency and changes in beam resistance and capacitance as a result of applied mechanical and electrostatic stresses to the beam.
Frachel, Michael J.
"Integrated Electronics for Micro-Electromechanical Devices,"
Journal of the Microelectronic Engineering Conference: Vol. 7
, Article 4.
Available at: http://scholarworks.rit.edu/ritamec/vol7/iss1/4