Additively patterned ferroelectric thin films with vertical sidewalls

The functional properties of electroceramic thin films can be degraded by subtractive patterning techniques used for microelectromechanical (MEMS) applications. This work explores an alternative deposition technique, where lead zirconate titanate (PZT) liquid precursors are printed onto substrates in a desired geometry from stamp wells (rather than stamp protrusions). Printing from wells significantly increased sidewall angles (from similar to 1 to >35 degrees) relative to printing solutions from stamp protrusions. Arrays of PZT features were printed, characterized, and compared to continuous PZT thin films of similar thickness. Three-hundred-nanometer-thick printed PZT features exhibit a permittivity of 730 and a loss tangent of 0.022. The features showed remanent polarizations of 26C/cm(2), and coercive fields of 95kV/cm. The piezoelectric response of the features produced an e(31,f) of -5.2C/m(2). This technique was also used to print directly atop prepatterned substrates. Optimization of printing parameters yielded patterned films with 90 degrees sidewalls. Lateral feature sizes ranged from hundreds of micrometers down to one micrometer. In addition, several device designs were prepatterned onto silicon on insulator (SOI) wafers (Si/SiO2/Si with thicknesses of 0.35/1/500m). The top patterned silicon was released from the underlying material, and PZT was directly printed and crystallized on the free-standing structures.