Micromachined capacitive transducer arrays for medical ultrasound imaging

The fabrication and characterization of micromachined capacitive ultrasonic transducers are discussed with emphasis on the array operation. Several micromachined capacitive transducer arrays have been fabricated using CMOS compatible micromachining technology. Pulse echo experiments show around 100% bandwidth and the potential for phased array imaging. Radiation pattern and cross-coupling measurements are performed on the 1-D and 2-D arrays. Cross-coupling mechanisms due to Lamb and Stoneley type waves are identified by experiments and verified by theoretical calculations. Deep trench etching between array elements and wafer thinning are proposed to reduce the effects of these spurious waves for certain applications. Initial results on array imaging with 64 element 1D micromachined capacitive transducer arrays are also presented.