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Fabrication and characterization of a micro-machined ultrasonic transducer

This paper presents an innovative capacitive ultrasonic transducer. The transducer is fabricated by bulk micromachining with a customized bonding process. The major distinctive point of this new technology is that, crystallography property of single crystal silicon, rather than an initially designated mask pattern, is utilized to form the honeycomb-like supporting frame. So that ideal hexagonal element geometry, as well as extreme uniform cell array, can be realized. Initial investigation results showed that this new product has a sharp resonance frequency of 2.67 MHz, with a quality factor of more than 50. The discrepancy of the transducers, in term of their resonance frequency, is less than 1%. Since the back cavities have been sealed by hermetic bonding, such transducer can be used for both airborne and immersion applications.