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Protection Layer Influence on Capacitive Micromachined Ultrasonic Transducers Performance

Published online by Cambridge University Press:  01 February 2011

Edgard Jeanne
Affiliation:
edgard.jeanne@st.com, Université de Tours, Laboratoire de Microélectronique de Puissance, Rue Pierre et Marie Curie - B.P. 7155, TOURS, 37071 TOURS CEDEX 2, France
Cyril Meynier
Affiliation:
cyril.meynier@univ-tours.fr, Université Francois Rabelais, LUSSI CNRS FRE 2448, Tours, 37000, France
Franck Teston
Affiliation:
franck.teston@univ-tours.fr, Université Francois Rabelais, LUSSI CNRS FRE 2448, Tours, 37000, France
Dominique Certon
Affiliation:
dominique.certon@univ-tours.fr, Université Francois Rabelais, LUSSI CNRS FRE 2448, Tours, 37000, France
Nicolas Felix
Affiliation:
nicolas.felix@vermon.com, Vermon SA, Tours, 37000, France
Mathieu Roy
Affiliation:
mathieu.roy@st.com, STMicroelectronics, R&D, Tours, 37071, France
Daniel Alquier
Affiliation:
daniel.alquier@univ-tours.fr, Université de Tours, Laboratoire de Microélectronique de Puissance, Tours, 37071, France
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Abstract

For MEMS technology, reliability is of major concern. The implementation of a protection and passivation layer, that may easily enhance reliability of capacitive Micromachined Ultrasonic Transducers (cMUTs) must be done without degrading device performance. In this work, realization, simulation and characterization of passivated cMUT are presented. Two materials, SiNx and Parylene C, were selected with regard to their mechanical and physical properties as well as their compatibility with device processing. Particular attention was paid on layer deposition temperature to avoid a structural modification of the top aluminium electrode and, hence, a membrane bulge. The characterization results are in good agreement with the simulations. The SiN passivation layer clearly impact device performance while Parylene C effectiveness is clearly pointed out even through ageing characterizations. If SiNx layer can be used for passivation with particular precautions, Parylene is definitely an interesting material for cMUT passivation and protection.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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