Fast Estimation of Collapse and Snapback Voltage Nonuniformity in CMUT Arrays.

For Capacitive Micromachined Ultrasonic Transducer (CMUT) arrays operating either in pre-collapse or collapse mode, the selection of the bias point has a significant impact on the transducer performance. In both operating modes, the electrical biasing condition is fixed based on the values of collapse and snapback voltages of the CMUT, making their accurate evaluation highly relevant. In this work, we propose a fast measurement technique combined with a data processing algorithm that enables rapid and accurate estimation of CMUT collapse and snapback voltages. This approach is applied to different CMUT arrays to achieve a thorough analysis of collapse and snapback voltage distributions, demonstrating its effectiveness in assessing both intra-element and inter-element nonuniformities caused by microfabrication variability. The method is suitable for wafer-level testing, allowing element-wise characterization of large arrays in short time. Furthermore, it is potentially scalable to in-probe implementation, enabling real-time monitoring of collapse and snapback voltages drift and adaptive bias point adjustment for optimized transducer performance.