Integration of trench-isolated through-wafer interconnects with 2d capacitive micromachined ultrasonic transducer arrays

• Published in: Sensors and actuators. A. Physical. Vol. 138; no. 1; pp. 221 - 229
• Main Authors: Zhuang, Xuefeng, Ergun, Arif S., Huang, Yongli, Wygant, Ira O., Oralkan, Omer, Khuri-Yakub, Butrus T.
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 20.07.2007
• Subjects: Capacitive micromachined ultrasonic transducer (CMUT); Flip-chip bonding; Post-processing; Through-wafer interconnect; Trench isolation; Capacitive micromachined ultrasonic transducer (CMUT); Trench isolation; Post-processing; Through-wafer interconnect; Flip-chip bonding
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2007.04.008

This paper presents a method to provide electrical connection to a 2D capacitive micromachined ultrasonic transducer (CMUT) array. The interconnects are processed after the CMUTs are fabricated on the front side of a silicon wafer. Connections to array elements are made from the back side of the substrate via highly conductive silicon pillars that result from a deep reactive ion etching (DRIE) process. Flip-chip bonding is used to integrate the CMUT array with an integrated circuit (IC) that comprises the front-end circuits for the transducer and provides mechanical support for the trench-isolated array elements. Design, fabrication process and characterization results are presented. The advantages when compared to other through-wafer interconnect techniques are discussed.