Correlation of materials and ferroelectric properties of sputtered and sol-gel PZT films

Abstract

The processes for the physical vapor deposition (PVD) of Pb(Zr,Ti)O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PZT) thin films from two different composite oxide targets has been demonstrated. PZT thin films have been deposited by both PVD or sputter technique and standard sol-gel method. Half micron PZT films were deposited by both methods on identical substrates (Si[(100) 4 inch Cz wafer]/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Ti-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Pt) followed by sputter-deposited Pt top electrodes. X-ray diffraction results showed that both sputtered and sol-gel PZT films were textured along the direction. The degree of preference for the direction was greater in the sol-gel film where the intensity of that peak is seen to be larger compared to the intensity for the sputtered PZT. TEM data revealed that both sputtered and sol-gel PZT films were polycrystalline and had perovskite crystal structures. Selected area diffraction (SAD) showed that the degree of disorientation between the crystallites was smaller for the sol-gel PZT compared to the sputtered PZT, which corroborated the results from XRD. The remnant polarization, P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> and coercive field, E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> for the sputtered films were less than sol-gel film; however, PVD produced higher relative permittivities. The leakage current for the 11% excess Pb target sputtered film was similar to the sol-gel film and much less than that produced by the 22% excess Pb condition. The breakdown voltage of the sol-gel PZT film was still the best. However, for the 11% Pb target sputtered film's breakdown voltage was much higher than 22% Pb target sputtered film. This study has demonstrated that sputtering has the potential to serve as a viable alternative to the sol-gel process for the deposition of PZT thin films. The experimental data showed comparable results in most aspects of the films investigated. Most importantly it is the improved manufacturability the sputter method offers. In particular, for the 11% excess Pb target sputtered film, the breakdown voltage was significantly improved, which revealed a broad potential of the sputtered PZT film applications.