Optimization of PbTiO₃ seed layers and Pt metallization for PZT-based piezoMEMS actuators

This work attempts to optimize past research results on lead zirconate titanate (PZT) using the fabrication processes at the U.S. Army Research Laboratory so as to achieve a high degree of {001} texture and improved piezoelectric properties. A comparative study was performed between Ti/Pt and TiO2/Pt bottom electrodes. The results indicate that the use of a highly oriented {100} rutile phase TiO2 led to highly textured {111} Pt which in turn improved both the PTO and PZT orientations. PZT (52/48) and (45/55) thin films with and without PTO seed layers were deposited and examined via x-ray diffraction (XRD) methods as a function of annealing temperature. The seed layer provides significant improvement in the {100} orientation generally, and in the {001} subset of planes specifically, while suppressing the {111} orientation of the PZT. Improvements in the Lotgering factor (f) were observed from an existing Ti/Pt/PZT process (f = 0.66) to samples using the PTO seed layer deposited onto the improved Pt electrodes, TiO2/Pt/PTO/PZT (f = 0.96).