High performance LaNiO3-buffered, (001)-oriented PZT piezoelectric films integrated on (111) Si

Abstract

Integration of high-performance lead zirconate titanate (PZT) piezoelectric films onto (111) Si substrates is beneficial for the development of piezoelectric micro-electro-mechanical systems (Piezo-MEMS) because of (111) Si's isotropic mechanical properties and desirable etching characteristics. These features will greatly reduce complications in micro-device fabrication and patterning of PZT/Si heterostructures. However, piezoelectric performance of a PZT film is usually dominated by its preferred crystalline orientation, with (001) being superior than (110) and (111). Such a vectorial dependence seriously restricts applications of PZT films grown on (111) Si, which are usually not (001)-textured. In this work, highly (001)-oriented PZT thick films (∼1.5  μm) with a 53/47 Zr/Ti ratio were prepared on (111) Si substrates via a multi-layer buffering technique, i.e., through the use of a (111)Pt/Ti bi-layer and a LaNiO3 buffer layer. The PZT films were sputter-deposited at a low temperature (350 °C) and then crystallized in a (001) texture via a rapid thermal annealing (RTA). The e31,f transverse piezoelectric coefficient was up to ∼11.6 C/m2 for PZT films with a RTA time of 2 minutes. Such an e31,f value is comparable to that of PZT films grown on (100) Si. This work opens up many possibilities for Piezo-MEMS by demonstrating the desirable combination of a large piezoelectricity in (001) PZT with a good patternability of (111) Si.