CMUT arrays incorporating anodically bondable LTCC for small diameter ultrasonic endoscope

This paper reports fabrication of CMUT (Capacitive Micromachined Ultrasonic Transducer) based forward looking ultrasonic endoscope using custom designed LTCC (Low Temperature Co-fired Ceramic). Bottom electrodes and cavities are separately patterned on LTCC and SOI wafers, respectively. LTCC wafer is used as bottom substrate (prime wafer) for anodic bonding and ring array and linear array CMUTs transducers are fabricated. To drive transducer arrays electrical connections between transducer arrays and IC (Integrated Circuits) are achieved by LTCC side via accomplished hexagonal shape dicing of CMUT after fabrication. Design, fabrication process and first fabrication results are presented. The advantages of CMUT packaging using LTCC side via compared to previously announced CMUT probe packaging such as TSV (Through Silicon Via) scheme are discussed.