Silicon substrate ringing in microfabricated ultrasonic transducers

Experimental and theoretical evidence of silicon substrate ringing in microfabricated ultrasonic transducers is presented. This ringing is clearly observed in immersion transducers with a 650 /spl mu/m thick substrate at 7 MHz and harmonics. An analytical model of the ringing is introduced, and simulations based on the model are shown to agree with experimental observation. Experimental results are further compared to simulations carried out in time-domain, large-scale PZFlex models and qualitative agreement is demonstrated. The insights gained from the simulations and experiments are used to design and fabricate a device whose ringing mode is eliminated with a backing layer.