High Performance Sputtered PZT Film for MEMS applications

Y. Hishinuma, Y. Li, J. Birkmeyer, T. Fujii, T. Naono, T. Arakawa
FUJIFILM Dimatix, US

Keywords: PZT, thin film, piezoelectric, sputtering

Summary:

We have developed a method of forming PZT films on silicon substrates with a high piezoelectric coefficient using RF sputtering. Films have been formed on 6 inch wafers with thickness variation of less than +/-5% across the entire wafer. Our PZT film has an unusually high content of Nb dopant (13%) which results in ~70% higher piezoelectric coefficient than sputtered PZT films previously reported. The x-ray diffraction patterns of our PZT film formed on a 6 inch wafer, demonstrate that film is in a perovskite phase with (100) orientation which partly accounts for its high piezoelectric performance. One of the unique properties of our sputtered PZT film can be observed in the hysteresis loop shifted to the positive electric field, suggesting that the polarization axes have been aligned in a certain direction beforehand, making a post-deposition polarization process unnecessary. The piezoelectric performance of our PZT films have been measured using a diaphragm structure. The actuator is activated by AC voltage signal and the diaphragm displacement is measured by a laser Doppler vibrometer. Finite element modeling yielded d31= -250pm/V for our Nb-PZT film.