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Fabrication of Piezoelectric Diaphragm Using Lead Zirconate Titanate (PZT) Films

Published online by Cambridge University Press:  15 March 2011

E. Hong
Affiliation:
Materials Research Institute, The Pennsylvania State University, University Park, PA 16802
S.V. Krishnaswamy
Affiliation:
Materials Research Institute, The Pennsylvania State University, University Park, PA 16802 Northrop Grumman Electronics Systems, Baltimore, MD 21203
C.B. Freidhoff
Affiliation:
Northrop Grumman Electronics Systems, Baltimore, MD 21203
S. Trolier-McKinstry
Affiliation:
Materials Research Institute, The Pennsylvania State University, University Park, PA 16802
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Abstract

Piezoelectric diaphragms were fabricated using bulk micromachining. The diaphragms had a unimorph structure, where Pb(Zr0.52Ti0.48)O3 (PZT) and thermally grown silicon oxide (SiO2) films were used as the active and passive layers, respectively. To actuate the diaphragms, two modes were designed: d31 and d33-mode. For d31-mode diaphragms, a Si wafer with Pt/Ti/SiO2 (0.5 νm) was coated with ∼1.2 νm PZT. A Cr/Au top electrode was then evaporated. Each layer including the bottom electrode was patterned into a circular shape. To fabricate d33-mode diaphragms, a Si wafer with thermal SiO2 (0.5 νm) was coated with ∼0.3 νm ZrO2 and ∼1.6 νm of PZT. On top of these layers, a Cr/Au top electrode was deposited and patterned into a ring- shaped interdigitated transducer. Finally, both d31 and d33-mode diaphragms were released using deep reactive ion etching. Diameters of the fabricated diaphragms were in the range of 600 νm and 1000 νm. For d31-mode diaphragms, the dielectric constant and loss of the released piezoelectric layer at 1 kHz were > 800 and < 2%, respectively. The remanent polarization was ∼20 νC/cm2and the coercive field was ∼61 kV/cm. Ferroelectric measurements showed well- developed hysteresis loops for the d33-mode diaphragms. Both d31 and d33-mode diaphragms behave as membranes rather than plates. Their measured resonance frequencies were consistent with calculations from an analytic model for circular membranes and ANSYS finite element analysis.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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