The Effects of the Preparation Conditions and Heat-Treatment Conditions of Pt/Ti/SiO2/Si Substrates on the Nucleation and Growth of Pb(Zr,Ti)O3 Films

Abstract

Pb(Zr,Ti)O₃ films were deposited using DC magnetron multi-target reactive sputtering on Pt/Ti/SiO₂/Si substrates. The effect of the substrate on the structure of the deposited film was investigated because the nucleation of the perovskite PZT film would be largely affected by the substrate surface conditions. As the thickness of the Ti underlayer increases and that of the Pt layer decreases, Ti out-diffusion to the Pt substrate surface through the grain boundary of the Pt layer is enhanced so that the formation of the perovskite phase is promoted by facilitating the incorporation of Pb component. At the same time, the degree of (100) preferred orientation of the perovskite phase decreases. This change in the preferred orientation of the PZT film is also observed with decreasing the preparation temperature of the Pt/Ti layers. The structural phase of the PZT film and the resultant electrical properties have a sensitive dependence on the thermal history (such as processing time and environment) of the substrate prior to the deposition of the PZT film. The heat-treatment in Ar environment promotes the out-diffusion of Ti and the out-diffused Ti, which is expected to cover a large area of the PZT surface due to its good wettability, facilitates the formation of perovskite PZT film. The heat-treatment in oxygen environment, however, is scarcely effective in obtaining perovskite-phase PZT films because the out-diffusion of Ti to the Pt surface is suppressed by titanium oxide formed along the grain boundaries of the Pt layer and the surface titanium oxide will be localized only at the grain boundaries of the Pt surface due to poor wettability of titanium oxide on Pt.