Ph.D. Thesis Oral Examination
"Temperature Insensitive Microelecromechanical Resonators"
Advisor: Prof. Thomas Kenny
Date: Friday, June 13th
Time: 9:00 am (Refreshments beforehand)
Place: CISX-101 (Auditorium)
http://campus-map.stanford.edu/index.cfm?ID=04-055
Abstract:
Silicon resonators for frequency reference applications capitalize on
the size and cost advantages of silicon processing. Start-ups developing
silicon resonators, such as SiTime, Discera, and Silicon Clocks, seek to
displace the $2.5 billion quartz crystal frequency reference market that
is at the core of modern electronic devices. However, unacceptable
frequency deviations caused by the temperature dependence of silicon's
material properties prevent these resonators from competing with quartz
resonators in high precision applications.
This work describes the design, fabrication, and testing of silicon -
silicon dioxide composite resonators whose temperature sensitivity is
comparable to quartz crystal resonators. The optimization of the
composite resonator demonstrates a thirty-fold reduction in
frequency-temperature sensitivity compared to uncompensated silicon
resonators. These temperature insensitive devices are single anchored
flexural mode resonators, are isolated from packaging stresses, and are
hermetically sealed in a CMOS compatible wafer-level encapsulation
technology. In conjunction with active temperature compensation schemes,
such as those employed in the quartz industry, this passive technology
enables silicon-based frequency references to surpass the size and power
limitations of quartz crystals in high precision applications.
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