Low Cost, Contamination-Free, and Damage-Free Fabrication of PZT MEMS on SOI Substrate

This paper reports a generalised process flow for the fabrication of Lead Zirconate Titanate based Piezoelectric Micro Electromechanical System devices. The optimised process can be used to realise several devices with different 1-D and 2-D geometries on a single wafer. All the state-of-the-art fabrication methods introduce some damage to the active piezoelectric material. This damage entails the need for an additional step of recovery anneal in the fabrication process. Our process was designed and optimised to avoid any such damage to the PZT layer. Remnant polarisation and effective transverse piezoelectric coefficient (e31,f) were used as metrics to quantify the damage to the PZT layer. It is shown that our process does not damage the PZT thin film during the fabrication, and hence no recovery anneal is required. We observe a ~3x improvement in remnant polarisation and ~2x improvement in e31,f of PZT thin film compared to the PZT thin film subjected to our previous fabrication process. Moreover, the process explained here uses only wet chemical methods for patterning of contaminating agents (PZT and platinum), making it a cost-effective process.