Model Relating Thin Film Pzt Crystallographic Texture to Ferroelectric Switching Performance

Abstract

The fundamental physical property used for data storage in a ferroelectric non-volatile memory (FRAM) is the remanent polarization of a ferroelectric capacitor. In order to sense the data state of the capacitor, the charge pulse generated by either a switching or non-switching ferroelectric polarization is detected. Since the polarization of the ferroelectric is a vector property, the switchable polarization response of a ferroelectric capacitor is necessarily dependent on the texture of the ferroelectric material used to make the capacitor. A series of Ca, Sr, and La doped PbZr_0.4Ti_0.6O₃ (PZT) capacitor test samples were produced with texture ranging from nearly complete {111} texture to random orientation. The volume fraction of the textured material was quantified by X-ray diffraction. An experimental correlation between texture and the switchable polarization was established using pulse switching measurements. A mathematical model was developed to explain the dependence of the switchable polarization on the crystallographic texture. It was found that the dependence of the saturated switchable polarization on texture required that there was no 90° domain reorientation. The impact of these findings will be related to the performance of FRAM.