Sensor arrays for bio/chemical sensing generally incorporate different types of sensors with different substrate
coatings, enabling increased sensor sensitivity and selectivity. However, a challenge in using multiple sensor
systems is integration with RF electronic circuitry. This work presents the development of flexural plate
wave (FPW) acoustic devices implemented in a sensor array and co-integrated on a Si-CMOS circuit. FPWs
are highly sensitive to surface perturbations and indirectly sense analytes by detecting mass changes on the
sensing plate surface. The sensors are placed in an oscillating circuit, where changes in the oscillation
frequency are used to determine changes in the wave velocity due to mass loading by the analyte [1, 2]. Since
FPWs are generated in thin plates, these devices are highly sensitive to loading and exhibit the highest mass
sensitivities of any acoustic wave device [1, 2]. In the work presented, FPWs are fabricated on Si/SiO2/Si
native substrates, with the interdigitated transducers (IDTs) isolated from the active sensing surface. This
innovative design enables the sensors to be fabricated and then separated from the native substrate, transferred,
and bonded to the host Si-CMOS circuit. Thus, a new approach for the heterogeneous integration of FPW
sensors and circuitry is provided. Following integration, the FPWs can be customized with either chemical
membranes or biological functionalization. Moreover, this novel approach allows each sensor to be
optimized independently before being connected to the host substrate. This paper presents the design,
development, and integration process of an FPW sensor on Si-CMOS circuitry.
In light of the efforts to improve the performance of micromachined gyroscopes, this paper presents an investigation of
energy loss mechanisms in a SOI-based tuning-fork gyroscope, since these loss mechanisms dictate the value of the
mechanical Quality factor (Q) that has been identified as a critical determinant for achieving high-precision
performance. The numerical models of thermoelastic damping (TED) and anchor loss in the tuning-fork gyroscope
design are created in a FEM software, ANSYS/Multiphysics, according to a thermal-energy method and a separationand-
transfer method, respectively. The calculated results indicate that thermoelastic damping is the dominant loss while
anchor loss is negligible for the gyroscope design. In order to validate the created models, an experimental study on the
Q of the SOI-based tuning-fork gyroscope is consequently conducted. Comparison between the calculated results and the
measured data not only validates the numerical models, but also demonstrates the significant effect of fabrication process
on the final achievable Q values of the fabricated gyroscopes.
This paper reports on the design, fabrication, and testing of a SOI-based tuning-fork gyroscope with high Quality factors
(Qs). A tuning-fork structure with high Qs is designed and is integrated with on-chip electrostatic transducers for
excitation and detection. With a one-mask fabrication technology, this gyroscope design is fabricated on a SOI wafer
with a 30μm-thick device layer. The fabricated devices are further tested for their preliminary performance
characterization. The measured Qs of a fabricated gyroscope are 162,060 for the drive mode and 85,168 for the sense
mode at 16.8kHz. In order to enhance its rate sensitivity, the frequency of the sense mode is tuned using electrostatic
tuning toward that of the drive mode and a minimum frequency split of 6Hz between the two modes is demonstrated.
Under this nearly matched-mode condition, a prototype device shows a measured rate sensitivity of 0.02mV/°/sec. The
theoretical mechanical resolution due to Brownian noise is 0.3°/hr/√Hz.
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