A Design of High-Sensitivity Micromachined Capacitive Ultrasonic Mass Resonators
2008 IEEE International Ultrasonics Symposium Proceedings，-0001，（）：
The TDK model originally developed for capacitive micromachined ultrasonic transducers (CMUT) is applied to the modeling and design of capacitive ultrasonic mass resonators (CUMR). The diaphragm of CUMRs is treated as a laminated plate in tension and supported by elastic foundation, and then its fundamental frequency can be expressed in terms of the stiffness of the diaphragm, tension in it, the electrostatic negative stiffness caused by bias voltage, the frequency parameter of the vibration of diaphragm, and area density of diaphragm. Furthermore, the mass sensitivity of CUMRs, which is intrinsically nonlinear, is derived and its first order approximation and the reference sensitivity are also defined. The design of CUMRs then can be computationally performed for different geometric dimensions of the device and the physical parameters of material used. Finally, a design of CUMRs is given based on the TDK model. Its fundamental frequency is 10.08MHz at bias voltage of 30V; the resonance frequency decreases as bias is increased and is down to 9.86MHz at 300V. The reference mass sensitivity is -1312cm2/g,so 1 Hz resonance frequency shift corresponds to an added mass of 76 pg/cm2. Comparing with piezoelectric ultrasonic mass resonators (PUMR), CUMRs can be an attractive choice for chemical and biological detections.