Micromachined piezoelectric diaphragms actuated by ring shaped interdigitated transducer electrodes

Piezoelectric diaphragms actuated by interdigitated transducer (IDT) electrodes were fabricated by bulk micromachining. To fabricate the diaphragms, a Si wafer with similar to 0.5 mu m of thermal SiO2 was coated with similar to 0.3 mu m ZrO2 and similar to 1.6 mu m thick Pb(Zr0.52Ti0.48)O-3 (PZT) layers. A Cr/Au top electrode was then deposited and patterned into ring-shaped IDT electrodes. The diaphragms were released using deep reactive ion etching. The fabricated diaphragms had three different IDT diameters of 500, 600 or 700 mu m and their diameters were similar to 40% larger than the IDT diameters. The PZT films on these diaphragms exhibited good ferroelectric properties. Their remanent polarizations were similar to 20 mu C/cm(2) and the coercive fields were about 50kV/cm. Resonance measurements for these diaphragms indicated that the diaphragms behaved as membranes. Without an electric field, the diaphragms were almost flat to within similar to 0.3 mu m. At an electric field of 120 kV/cm, the diaphragm was depressed by similar to 4.3 mu m in the case of a 700 mu m diaphragm with 10 mu m electrode spacing. The deflection profiles were modeled via finite element analysis; deflections larger than the structure thickness can be achieved. This makes these devices useful for micropumps and other actuator applications. (c) 2004 Elsevier B.V. All rights reserved.