Towards Electrostatic Force-Feedback for Reducing Thermally-Induced Vibrations of MEMS

Abstract

We propose using electrostatic force-feedback to counter thermally-induced structural vibrations in micro electro mechanical systems (MEMS). Noise, coming from many different sources, often negatively affects the performance of N/MEMS by decreasing the precision for sensors and position controllers. As dimensions become small, mechanical stiffness decreases and the amplitude due to temperature increases, thereby making thermal vibrations become more significant. Thermal noise is most often regarded as the ultimate limit of sensor precision. This limit in precision impedes progress in discovery, the development of standards, and the development of novel NEMS devices. Hence, practical methods to reduce thermal noise are greatly needed. Prior methods to reduce thermal vibration include cooling and increasing flexure stiffness. However, the cooling increases the overall size of the system as well as operating power. And increasing the flexure stiffness can come at the cost of reduced performance. Electrostatic position feedback has been used in accelerometers and gyroscopes to protect against shock and improve performance, but we appear to be the first to propose that the method be applied to reduce vibration from noise by using velocity controlled force-feedback. Our study includes analytical models with parasitics that we verify through simulation. Using transient analysis, we show the vibrational effects of white thermal noise upon a MEMS, and we show greatly reduced vibration due to the inclusion of a simple electrostatic feedback system.