Micromachined Accelerometer Design, Modeling and Validation

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Micromachining technologies enable the development of low-cosr devices capable of sensing motion in a reliable and accurate manner. The development of various surface micromachined accelerometers and gyroscopes to sense motion is an ongoing activity at Sandia IVational Laboratories. In addition, Sandia has developed a fabrication process for integrating both the micromechanical structures and microelectronics circuitry of Micro-Electro-Mechanical Systems (MEMS) on the same chip. This integrated surface micromachining process provides substantial performance and reliability advantages in the development of MEMS accelerometers and gyros. A Sandia MEM5 team developed a single-axis, micromachined silicon accelerometer capable of surviving and measuring very high accelerations, up to 50,000 times the acceleration due to gravity or 50 k-G (actually measured to 46,000 G). The Sandia integrated surface micromachining process was selected for fabrication of the sensor due to the extreme measurement sensitivity potential associated with integrated microelectronics. Measurement electronics capable of measuring attoFarad (10 8 Farad) changes in capacitance were required due to the very small accelerometer proof mass (<200 x 10 9 gram) used in this surface micromachining process. The small proof mass corresponded to small sensor deflections which in turn required very sensitive electronics to enable accurate acceleration measurement over a range of I to 50 k-G. A prototype sensor, based on a suspended plate mass configuration, was developed and the details of the design, modeling, and validation of the device will be presented in this paper. The device was analyzed using both conventional lumped parameter modeling techniques and finite element analysis tools. The device was tested and performed well over its design range.

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Journal: TechConnect Briefs
Volume: Technical Proceedings of the 1998 International Conference on Modeling and Simulation of Microsystems
Published: April 6, 1998
Pages: 552 - 556
Industry sector: Sensors, MEMS, Electronics
Topic: MEMS & NEMS Devices, Modeling & Applications
ISBN: 0-96661-35-0-3