Thin piezoelectric films for micro-electromechanical components
PbZrxT1-x O3 (PZT) films on silicon substrates can be used for various micro mechanical devices. An insitu reactive sputter deposition process at 600°C has been developed for this application. Three magnetron sources with metal targets have been applied simultaneously. Within a certain process window, the [Pb] / ([Zr]+[Ti]) ratio in the film is self stabilized at stoichiometry by desorption of the excess Pb. Films of up to 1 micron thickness have been fabricated. For the composition x = 0.4 the films exhiba a remanent polarization of 20 to 25 µC/cm2, a dielectric constant of 1100 and a piezoelectric coefficient of 40 pC/N. The classical Pt/Ti bottom electrode needed to be improved by an additional layer of TiO2 between Ti and Pt. As a second choice the metallic oxide RuO2 has been investigated, too. PZT films on prototype membrane structures are currently processed. They will be applied in prototype micromotors for the watch industry.