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Published online by Cambridge University Press: 01 February 2011
The P3 Micro Heat Engine relies on a thin film PZT based transducer to convert mechanical energy into usable electrical power. In an effort to increase process yield for these were used on sputtered Ti/Pt bottom electrodes to compare roughness, grain size, and diffusion for annealing temperatures between 550 and 700 °C. For an optimized bottom electrode, process yield for various sized top electrodes were then studied for PZT thickness between 0.54 and 1.62 for reducing stress concentrations. Two PZT etching geometries on 2.3 μm thick Si/SiO2 membranes, with 1.5-3.5 mm side-lengths, were examined and one was used to increase the strain at failure by at least 40%. Integrating improvements in process yield and strain at failure, single PZT based MEMS devices capable of generating power of up to 1 mW and in excess of 2 volts have been demonstrated operating at frequencies between 300 and 1,100 Hz.