Micromachined accelerometer design, modeling and validation

摘要

Micromachining technologies enable the development of low-cost 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 National 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. 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 at to Farad (10 to the -18th power Farad) changes in capacitance were required due to the very small accelerometer proof mass (< 200 x 10 to the -9th power 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 1 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 are 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.