Defects and Failure Modes in PZT Films for a MEMS Microengine

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.

Optimization of Film Stresses Utilized in Composite Piezoelectric Membrane Microgenerators

“…Fabrication of multilayer stacks of Si/SiO 2 /Ti/Pt/PZT/Au were carried out as described in [10,11]. The PZT was deposited using solution deposition methods, wherein a solution containing the proper chemistries of Pb, Ti, and Zr is deposited via spin coating and then heat treated to form the perovskite crystal structure.…”