| A dome-shaped piezoelectric micromachined ultrasonic transducer was fabricated using MEMS silicon bulk micromachining. This cost-effective batch process for fabrication makes this device an attractive choice for cellular microstucture imaging, skin cancer detection and pathology, and acoustic property measurement of cells and biomolecules. The active element of the transducer was a self-focused, 13 mum thick zinc oxide piezoelectric film with a center resonant frequency of approximately 200 MHz. The element was suspended on a dome-shaped membrane in a 1.6 mm aperture hole etched on a (100) silicon wafer. The transducer was tested in a pulse-echo arrangement and an echo signal was obtained at 200 MHz with approximately 31% bandwidth. Experimental results are in good agreement with those predicted by the KLM model. A high-frequency lithium niobate device was also fabricated and tested, and the results were used as a benchmark for comparison with the micromachined devices. |
