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Fabrication of MEMS Tonpilz Transducers

Published online by Cambridge University Press:  15 March 2011

Q. F. Zhou ,
L.-P. Wang ,
G. Gerber ,
R. Meyer Jr. ,
D. Van Tol ,
S. Tadigadapa ,
W. J. Hughes  and
S. Trolier-McKinstry
Q. F. Zhou
Affiliation:
Materials Research Institute, Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
L.-P. Wang
Affiliation:
Materials Research Institute, Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
G. Gerber
Affiliation:
Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
R. Meyer Jr.
Affiliation:
Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
D. Van Tol
Affiliation:
Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
S. Tadigadapa
Affiliation:
Materials Research Institute, Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
W. J. Hughes
Affiliation:
Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
S. Trolier-McKinstry
Affiliation:
Materials Research Institute, Department of Bioengineering, Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, U. S. A.
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Abstract

Tonpilz transducers consist of a heavy tail mass, a piezoelectric spring, and a light head mass. Miniaturized tonpilz transducers are potentially interesting for the 10 to100 MHz frequency range in imaging transducers due to their high efficiency and output capabilities. Piezoelectric thin films can be used as the active element in the construction of miniaturized tonpilz structures. A 4-10 νm film is necessary for the mass-spring-mass system to resonate at these high frequencies. In this work, fabrication and characterization of lead zirconate titanate (PZT) thick films on conductive oxide LaNiO3 (LNO) coated silicon on insulator (SOI) substrates will be reported for this application. First, conductive LNO thin films, approximately 300 nm in thickness, were grown on SOI substrates by a metal-organic decomposition (MOD) method. The room temperature resistivity of the LNO was 6.5×10-4 ωcm. Randomly oriented PZT (52/48) films up to 7 νm thick were then deposited using a sol-gel process on the LNO coated SOI substrates. 20 mol.% excess lead was added to the solutions to compensate for lead volatilization during film heat treatments. PZT films with LNO bottom electrodes showed good dielectric and ferroelectric properties. The dielectric permittivity (at 1 kHz) was over 1000. The remanent polarization of PZT films was larger than 26 νC/cm2. The e31,f coefficient of PZT thick films was larger than –6.5 C/m2 when poled at -75 kV/cm for 15 minutes. A silver layer approximately 40 νm thick was screen- printed onto the PZT film to form the tail mass of the tonpilz structure. Elements were diced and the bulk silicon was removed by dry and wet-etching methods to leave the p-type silicon layer as tonpilz head mass. Fabrication of MEMS tonpilz microstructures will also be presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 687: Symposium B – Materials Science of Microelectromechanical Systems (MEMS) Devices IV , 2001 , B5.22
Copyright
Copyright © Materials Research Society 2002

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