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The electro-mechanical conversion efficiency and the long-term reliability of Capacitive Micromachined Ultrasonic Transducers (CMUT) are mainly limited by the parasitic capacitance and by charge injection phenomena. In this paper, we investigated the possibility of reducing both the parasitic capacitance, by patterning the CMUT electrodes in order to avoid any superposition of the two electrodes outside the cavity area, and the charge injection phenomena, by introducing high-quality Silicon Oxide (SiO2) buffer layers between the electrodes and the cavity Silicon Nitride (Si x N y ) passivation layers. Test capacitors were initially fabricated with the aim of measuring the dielectric characteristics of the Si x N y , and to quantitatively evaluate the effects of the SiO2 buffer layers. Successively, 256-element CMUT arrays were designed and fabricated using both the classical and the modified electrode layouts and …
Publication date: 
6 Sep 2017

Alessandro Stuart Savoia, Barbara Mauti, Giosuè Caliano, Luca Maiolo, Antonio Minotti, Alessandro Pecora, Guglielmo Fortunato, Alvise Bagolini, Pierluigi Bellutti

Biblio References: 
Pages: 1-4
2017 IEEE International Ultrasonics Symposium (IUS)