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Fabrication of Micromachined Piezoelectric Diaphragm Pumps Actuated by Interdigitated Transducer Electrodes

Published online by Cambridge University Press:  11 February 2011

Eunki Hong ,
S.V. Krishnaswamy ,
T. T. Braggins ,
C.B. Freidhoff  and
S. Trolier-McKinstry
Eunki Hong
Affiliation:
Materials Research Institute and Materials Science and Engineering Dept., Pennsylvania State University, University Park, PA
S.V. Krishnaswamy
Affiliation:
Northrop Grumman Corporation Electronics System Sector, Baltimore MD
T. T. Braggins
Affiliation:
Northrop Grumman Corporation Electronics System Sector, Baltimore MD
C.B. Freidhoff
Affiliation:
Northrop Grumman Corporation Electronics System Sector, Baltimore MD
S. Trolier-McKinstry
Affiliation:
Materials Research Institute and Materials Science and Engineering Dept., Pennsylvania State University, University Park, PA
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Abstract

Micromachined pump structures were fabricated using surface micromachining. The structures consisted of three or five connected chambers. Sequential actuation of the diaphragms on these chambers will yield peristaltic pumping. As the actuation material, lead zirconate titanate (PZT [53/47] ) thin films were employed and actuated by interdigitated transducer (IDT) electrodes. First, chambers and channels on the 4″ (100) silicon wafers were defined by reactive ion etching (RIE) and thermally oxidized. The etched structures were then filled with amorphous silicon. Low temperature (silicon) oxide (LTO) and PZT films were then deposited. The LTO and PZT layers act as passive and active layers in a piezoelectric unimorph, respectively. A ZrO2 layer was employed to prevent reaction between SiO2 and PZT layers. A Cr/Au electrode was evaporated on top of the PZT layer and patterned into ring-shaped IDT electrodes. Finally, a porthole at each end of the pump structures was defined by ion milling and the whole micropump structure was released by removing the sacrificial amorphous silicon using XeF2. Completely released 500 μm diameter pump structures were fabricated. The remanent polarizations of the PZT films on released diaphragms were ∼20 μC/cm2 and their coercive fields were ∼50 kV/cm. 500 μm diameter diaphragms were deflected as much as 2 μm with 120 V applied. The shape and behavior of the diaphragm deflection can be explained by considering both d31 and d33 piezoelectric coefficients of the PZT films.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 741: Symposium J – Nano- and Microelectromechanical Systems (NEMS and MEMS) and Molecular Machines , 2002 , J5.7
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCE

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