As compared to piezoelectric technology, MEMS technology employed for Capacitive Micromachined Ultrasonic Transducer (CMUT) fabrication provides increased compatibility with 3D packaging methods, enabling the possible development of advanced transducer-electronics multi-chip modules (MCM) for medical imaging applications. In this paper, an acoustically optimized 3D packaging method for the interconnection of Reverse-Fabricated 2D CMUT arrays and front end ICs using a wafer-level compatible process is presented. The developed packaging method uses Cu pillars and Sn-Ag solder reflow for electrical interconnection, and patterned Benzocy-clobutene (BCB) for mechanical bonding. Process parameters were optimized by analyzing the acoustic behavior of a CMUT supported by a BCB film laying on a silicon substrate using Finite Element Modeling (FEM). Dummy CMUT and ASIC wafers were processed and MCMs were assembled following a chip-to-chip bonding approach using the optimized process parameters. Electrical characterization of the MCMs demonstrated successful contact across the entire fabricated devices. Probe head prototypes were assembled and pulse-echo experiments were carried out using the MCM surface as a reflector to verify the effectiveness of the optimization on the acoustic behavior of the device.
A 3D packaging technology for acoustically optimized integration of 2D CMUT arrays and front end circuits
Matrone, Giulia;Piastra, Marco;
2017-01-01
Abstract
As compared to piezoelectric technology, MEMS technology employed for Capacitive Micromachined Ultrasonic Transducer (CMUT) fabrication provides increased compatibility with 3D packaging methods, enabling the possible development of advanced transducer-electronics multi-chip modules (MCM) for medical imaging applications. In this paper, an acoustically optimized 3D packaging method for the interconnection of Reverse-Fabricated 2D CMUT arrays and front end ICs using a wafer-level compatible process is presented. The developed packaging method uses Cu pillars and Sn-Ag solder reflow for electrical interconnection, and patterned Benzocy-clobutene (BCB) for mechanical bonding. Process parameters were optimized by analyzing the acoustic behavior of a CMUT supported by a BCB film laying on a silicon substrate using Finite Element Modeling (FEM). Dummy CMUT and ASIC wafers were processed and MCMs were assembled following a chip-to-chip bonding approach using the optimized process parameters. Electrical characterization of the MCMs demonstrated successful contact across the entire fabricated devices. Probe head prototypes were assembled and pulse-echo experiments were carried out using the MCM surface as a reflector to verify the effectiveness of the optimization on the acoustic behavior of the device.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
