环形压电超声换能器阵列的加工与研究

PMUT(Piezoelectric Micro-machined Ultrasonic Transducer) is a kind of sensor based on micro-electro-mechanical technology that can generate or receive sound waves through the vibration of piezoelectric film. It is a hybrid system that integrates electronics and acoustics. In recent years, the development of ultrasonic technology is very quick, such as medical imaging, ultrasonic stimulation and other fields demonstrated increasing demand for high-performance ultrasonic transducers. Compared to traditional piezoelectric transducers made by bulk materials, PMUT has many advantages, such as small size, higher integration, compatibility with digital circuit technology, and convenience of array control. It has significant value in research and application. However, the small size of PMUT results in a lower sound pressure, which is a point that limited the application of PMUT and a problem that we urgently need to deal with.

Based on the analysis of traditional PMUT structures, this paper proposed a ringlike structure with two electrode that can improve the far field directivity of acoustic waves. The parameters of the structure are optimized through simulation, and some test sample is fabricated based on micro-electro-mechanical technology. Finally, a PMUT array with a size of only 0.8*0.8*0.3cm after packaging based on a 2um PZT film is obtained. In air, with 10V driving voltage, the device has 130nm displacement in predicted vibration mode at the center frequency of 1.395 MHz. In water, with power amplifier, the sound pressure generated by PMUT is up to 581kPa at the frequency of 1 MHz, which is more than twice as much as the traditional structure.

Through the improvement of the sound pressure, it is hopeful to replace traditional bulk material transducer with PMUT in some special applications.

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