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Joshua LEE, Assistant Professor, Department of Electronic Engineering, City University of Hong Kong

Theme: Modeling & Analysis Silicon Micromechanical Resonators
Date: July 16th, 2013 (Tuesday) - 10:00 , TIMA Laboratory - Room T312


Joshua LEE received the BA, MEng and PhD degrees from the University of Cambridge in 2005 and 2009. Since June 2009, he has been a tenure-track Assistant Professor in the Department of Electronic Engineering at City University of Hong Kong. His research interest is in the area of Micro Electro Mechanical Systems (MEMS), with a major focus on silicon micromechanical resonators. Within the last 6-7 years, he has authored and co-authored around 70 journal and conference papers. In January 2008, he received the Royal Academy of Engineering Research Student Development Fellowship (1 of 4 given), and was recently voted by students for one of the EE department’s Outstanding Teacher Awards.


Silicon micromechanical resonators offer the benefits of high performance, small form factor, and possibility of integration with CMOS. These devices have come a long way to a stage of relative maturity, seeing the commercialization of these technologies by SiTime and Discera. This talk aims to provide a brief overview of the research on this subject carried out at City University of Hong Kong. This includes methods capable of incorporating nonlinearities associated with resonators in a circuit simulator towards the aim of system-level simulation. Practical tricks to get around the problem of capacitive feedthrough by targeting parasitics at the packaging rather than the device level will be described Investigations into more fundamental problems will be introduced. One examples includes probing the effect of etch holes on quality factor and the underlying mechanisms of dissipation. Another example is the effect of crystal orientation in (100) silicon on the quality factor and the nonlinear bifurcation limit. Unusual phenomena of boosting (and attenuating) quality factor through injecting a DC bias current will also be shown. In addition, new concepts pertaining to resonator design will also be discussed. These include coupling silicon resonators in an array for synchronized resonance while maintaining quality factor of a million. Studies looking into possible tradeoffs between achieving high quality factor and electromechanical conversion using the piezoresistive effect will also be shown.