Fabrication of Wafer-Bonded 2D CMUT Array with Glass-Filled Trenches

Precise modulation of the focused beam is a critical technology for improving the performance of ultrasound-based treatments and diagnostics. Beyond conventional 1D transducer arrays, 2D transducer arrays have significantly broadened the scope of beam control applications. Leveraging CMOS compatibility, capacitive micromachined ultrasonic transducers (CMUT) have been regarded as an effective approach to fabricating 2D transducer arrays in a compact form. Although wafer-bonded CMUT arrays demonstrate excellent performance, their complex structures, including through-substrate vias and the need for mechanical stability, have posed significant challenges for 2D arrays. To address these challenges, we propose a novel method to enhance mechanical stability by employing a glass-reflow technique to fill the trench.