| Many applications in the electronics industry now require small, low profile components with a high efficiency of operation. Electromagnetic transformers, which consist of wire turns around a magnetic core, are unsuitable for integration as mid-scale microelectronic components. A thin film piezoelectric transformer has promise as a possible alternative. Radial mode thin film piezoelectric transformers with a diameter of 1–2 μm and piezoelectric layer thickness of 1–2 μm have a predicted operating range of 0.5–1.0 MHz with voltage gains of 0.1–10, depending on the dimensions and quality of the film. The device has been modelled using Mason's model for piezoelectric transformers. The piezoelectric layers of the transformer have been produced using an acetic acid based lead zirconate titanate (PZT) sol-gel process. A stable solution chemistry and consistent thermal processing route have been developed for producing multi-layer fully crystallized PZT coatings of high electrical quality and thicknesses up to 5 μm which is suitable for transformer production. The coatings are piezoelectrically active and have been characterized. One and two layer thin film transformers have been produced using a process suitable for the manufacturing environment which employs standard photo-lithographic and wet chemical etching techniques. A one layer thin film transformer with a PZT layer thickness of 2 μm and a diameter of 5.1 mm yields a voltage gain of 2.25 at 400 kHz, the resonant frequency of the device. The voltage gain can easily be altered by changing the dimensions of the device or the driving and output electrode patterns of the transformer. |
