High Performance Sputtered PZT Film for MEMS Applications

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 x1.7 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. A displacement measurement using a diaphragm structure yielded d(31)=-250pm/V. Additionally, 4-point cantilever bending experiment yielded e(31,f)= -23.1 C/m(2).