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.

Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

“…Laser dicing is an option for producing high-frequency array (>50 MHz), but the cost may be prohibitive. Deep reactive ion etching (DRIE) has been widely used in etching PZT thin films for ferroelectric memory application [147]. Recently, new advances in PZT dry etching have been reported [148–150].…”

Thin-Film Process Technology for Ferroelectric Application

“…Recently dry etching technique for MEMS using PZT was reported. [14,15] The Pt, Ir and other rare metal electrodes and the PZT ferroelectric thin films that compose piezoelectric elements react poorly with halogen gases and their halides have low vapor pressures. For these reasons, these materials are called hard-to-etch materials.…”

High-frequency (>50 MHz) medical ultrasound linear arrays fabricated from micromachined bulk PZT materials

“…The micromachining method can also fabricate kerfs as narrow as a few micrometers. Deep reactive-ion etching (DRIE) has been widely used to etch PZT thin films for ferroelectric memory applications [10]. Recently, new advances in bulk PZT dry etching have been reported [11]–[13].…”