Inductively coupled plasma reactive ion etching of lead zirconate titanate thin films for MEMS application

Piezoelectric lead zirconate titanate (PZT) thin film has been widely studied in microelectromechanical systems (MEMS) as an electromechanical conversion material. However, the application of the piezoelectric MEMS devices is still delayed by PZT integration difficulties, especially in PZT etching process. In this study, PZT thin film was etched using Ar/SF ₆ mixed gas in a conventional ICP-RIE system. The etch rate, etch selectivity and profile of the PZT film as well as platinum bottom electrode and photoresist were investigated as a function of the Ar concentration (Ar %) in Ar/SF ₆ mixture. The surface roughness, ferroelectric properties and dielectric properties of the PZT film were evaluated to indentify the effects of various etching receipts. It was found that high Ar % resulted in better PZT surface morphology. The largest PZT etch rate was achieved at 66.7 % of Ar. Reactive-physical mixed etching was preferred for great efficiency, but at the cost of bad surface roughness and low etch selectivity. Moreover, the ferroelectric properties and the dielectric properties of the PZT film were found not degraded by the proposed process. Fine PZT-electrode stack with the feature size of 15 μm and the PZT thickness of 1 urn was successfully obtained in this paper for piezoelectric MEMS application.