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METAL-ORGANIC THIN-FILM ENCAPSULA-TION FOR GRAVIMETRIC GAS MICROSENSORS
 

Summary: METAL-ORGANIC THIN-FILM ENCAPSULA-
TION FOR GRAVIMETRIC GAS MICROSENSORS
Jiandong Fang, Jenna Fu and Farrokh Ayazi
Georgia Institute of Technology, USA
ABSTRACT
Here we demonstrate a novel metal-organic thin-film encapsulation technique for
resonant gas microsensors to efficiently filter out airborne particles which can nega-
tively affect device performance. The gravimetric sensors are ZnO-on-silicon exten-
sional mode resonators coated with a gas-sensitive material. Mass change caused by
chemical reaction and/or physical adsorption can be detected through measured
resonant frequency shifts. The gas sensors are encapsulated in microcavities made
from multiple layers of Novolac-based positive-tone photoresist. Particle filtering is
achieved by minimizing clearance in the lateral access holes and electrostatic attrac-
tion from the organic polymer gas channels.
KEYWORDS: MEMS packaging, gravimetric sensing, gas sensor, piezoelectric
resonator
INTRODUCTION
Although negative-tone photoresist has been used to form cavity structures for
encapsulation [1, 2], its poor adhesion and swelling properties make it unsuitable to
package micromechanical devices. Typical Novolac-based positive-tone photore-

  

Source: Ayazi, Farrokh - School of Electrical and Computer Engineering, Georgia Institute of Technology

 

Collections: Engineering