Dry Etching Process for Pb(Zr,Ti)O3 Thin-Film Actuators

Abstract

We have developed a Pb(Zr,Ti)O3 (PZT) piezoelectric thin-film-actuator manufacturing technique by sputtering and dry etching processes. PZT etching rate and taper angle were investigated, and we obtained a very high etching rate (about 190 nm/min) and a high taper angle (62°). (001)/(100)-oriented PZT thin films on a (111)Pt/Ti/SiO2/Si substrate (6 in.) were prepared by RF magnetron sputtering, and Pt on PZT were prepared by DC magnetron sputtering. Pt/PZT/Pt piezoelectric thin-film actuators were fabricated by dry etching using an inductively super magnetron (ISM) plasma source. The characteristics of the ISM plasma source are high-density plasma and low-pressure operation attributable to the effect of the permanent magnet. The electrical properties of a piezoelectric thin-film-actuator cell fabricated by dry etching were investigated. The remanent polarization (Pr value) of a piezoelectric thin-film actuator with 3-µm-thick PZT film was 41 µC/cm2 at an applied voltage of 30 V, and remanent polarization characteristics without the dependence on element size (30–300 µm diameter) were obtained. Moreover, the displacement of a PZT thin-film-actuator was measured by contact atomic force microscopy (C-AFM), and a displacement of 4 nm was obtained at 3 µm thickness of the PZT film, 30-µm-diameter element size, and an applied electric field of 100 kV/cm. It was clarified that the fabrication of PZT piezoelectric thin-film-actuators by dry etching using an ISM plasma source is effective.