MEMS Resonators and Resonant Sensors

Ashwin A. Seshia
University of Cambridge

Thursday, May 28, 2009 at 1:00pm
Engr IV Room 54-134

Abstract
This talk will escribe ongoing research in my group in the areas of MEMS-based resonators and resonant sensors. Oscillators incorporating single crystal silicon MEMS resonators have been demonstrated with short term frequency stability of below 0.5ppb for centre frequencies between 0.1-10 MHz and associated Quality facotrs exceeding 1 million in moderate vacuum. A variety of integrated oscillator architectures have been developed for MEMS resonators. These oscillators may be viewed as timing references as well as building blocks for a variety of sensor applications. Some of these sensor applications will be discussed in detail. These applications include vibrating wire straing gauges with a resolution of close to 10Pε in a 1 HZ bandwidth and thin film monitors demonstrating sensitivites of 136 Hz/nm and a mass flux resolved noise floor uf under 17 pg/cm2. Frequency and dimensional scaling in the presence of process and package parasitic require innovative design solutions at the transducer, device and circuit levels. Some of the solutions developed in our group to address effective electrical interfacing to small-scale mechanical structures fabricated in hybrid MEMS processes will be presented.

Biography
A. Seshia received the B.Tech. in Engineering Physics in 1996 from IIT Bombay, and M.S. and Ph.D degrees in Electrical Engineering and Computer Sciences from the Univeresity of California, Berkeley in 1999 and 2002 respectively and a MA from the University of Cambridge in 2008. During his time at the University of California, Berkeley he was affiliated with the Berkeley Sensor & Actuator Center. He joined the faculty of the Engineering Department at the University of Cambridge in October 2002 where he is presently a Lecturer in Micro-Electro-Mechanical Systems, a Fellow of Queen's College and affiliated with the Nanoscience Centre. His research interests include the design and fabrication of micro- and nano-scale sensory systems with applications to the monitoring and study of the natural and built environment. He is a member of the Institute of Electrical and Electronics Engineers (IEEE) and the American Society of Mechanical Engineers (ASME), and in 2008 was appointed as Fellow of the ERA Foundation.