Integration and Optimisation of PZT Piezoelectric Thin Films in Micro and Nano Dimensional Structures

Abstract

We present in this paper a complete study of PZT thin films grown by r.f. sputtering onto platinised silicon substrates; the films are deposited at room temperature and post annealing is necessary to crystallise the PZT in the perovskite phase. The PZT composition (ratio Zr/Ti) is fixed to 54/46, i.e. in the morphotropic region where the piezoelectric activity is a maximum. For a future use in MEMS/NEMS it is imperative to know the intrinsic piezoelectric coefficients of the films; in particular the coefficients are d33, e31 and d31 are the most important to obtain. To determine these we have developed an experimental set-up based upon a commercial laser Doppler vibrometer and specific sample preparation procedures developed in the laboratory. These are necessary so that we do not integrate the substrate contribution with the measurement of the piezoelectric coefficient. The macro-structure of the PZT films is treated in this paper, as well as the micro and nano structure of the thin films and devices. This work has focused on two main objectives: optimisation of the etched processes: IBE (RIE) for micro structure fabrication and FIB for nanostructure and evaluation of the electrical degradations induces by the etching processes. We have optimised the process in order that functional performance is not degraded after etching. Keywords: Piezoelectric, PZT, Thin Films, Structure ( MEMS, &, NEMS), Piezoelectric coefficients