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Defects and Failure Modes in PZT Films for a MEMS Microengine

Published online by Cambridge University Press:  17 March 2011

D.F. Bahr
Affiliation:
Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
B.T. Crozier
Affiliation:
Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
C.D. Richards
Affiliation:
Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
R.F. Richards
Affiliation:
Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920
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Abstract

Piezoelectric films for a MEMS microengine have been deposited using solution deposition routines onto platinized silicon wafers. These films are used as membranes above a bulk micromachined cavity. A dynamic bulge tester and interferometer were used to characterize the deformation of the films when pressurized. The mechanical strain at failure, as well as the fatigue behavior, have been characterized. Membranes between 300 and 500 nm thick have been shown to sustain mechanical fatigue damage over approximately 10 million cycles at strains of 30% of the monotonic failure strain. Defects in the films due to growth and thermal stresses during processing, and their role in membrane failure, are identified. Crack growth is demonstrated in these films by compliance measurements during fatigue testing, and interfacial failure is identified between the PZT and Pt layers.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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