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Summary: COMBINED CAPACITIVE AND PIEZOELECTRIC TRANSDUCTION FOR
HIGH PERFORMANCE SILICON MICRORESONATORS
A.K. Samarao and F. Ayazi
Georgia Institute of Technology, Atlanta, Georgia, USA
ABSTRACT
This paper introduces the Aluminum Nitride High
Aspect-Ratio Polysilicon and Single-crystal Silicon
(AlN HARPSS) process technology that for the first time
enables combined capacitive (via air-gaps) and piezoelectric
(via Mo/AlN/Mo piezo-stack) transduction in silicon
micromechanical resonators. Lateral air-gaps as small as
150 nm have been realized for a 20 µm thick microresonator
(air-gap aspect-ratio = 133:1) while simultaneously
improving the c-axis orientation of aluminum nitride
sputtered on its top surface. Such a combined transduction
has been demonstrated to efficiently harvest the individual
advantages of both the technologies. A 100 MHz silicon
microresonator under combined capacitive and piezoelectric
transduction measures a ~25 dB reduction in feedthrough
compared to a capacitive-only transduction while measuring
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