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ABSTRACT The effects of reactive ion etching damage on the electrical properties of Pt/SBT/Pt capacitors have been investigated. The plasma treated SBT/Pt layers showed a significant decrease in remanent polarization compared with that of the reference sample. The remanent polarization of the plasma treated layers varied with the gas ratios of the C12/Ar plasma. XPS analysis of the plasma treated SBT/Pt samples showed that the surface composition was significantly changed as the gas ratios were varied, which resulted in a polarization decrease in the plasma treated samples. Plasma treatment also caused a voltage shift of the hysteresis loops along the voltage axis. The magnitude of the voltage shift was increased for the chlorine-rich plasma. The results of surface analysis revealed that the voltage shift is caused by oxygen deficiency at the SBT surface. Based on our experimental results, reactive ion etching damage was explained in terms of physical and electrical effects of the plasma on the electrical properties of the ferroelectric Pt/SBT/Pt capacitors. INTRODUCTION FeRAM devices are being studied with much attention for use in nonvolatile memory devices because of numerous advantages such as low operation voltage, fast write speed, and write endurance. [1-2] There are two strong candidate ferroelectric materials, PZT and SBT, for

this application. As a ferroelectric thin film, SBT has many advantages, for example, sufficient remanent polarization, low switching voltage, good fatigue behavior, and low leakage current. Pt is widely used as a standard electrode material in the fabrication of integrated ferroelectric capacitors because of its low resistivity and high stability at the temperatures required for perovskite crystallization. Despite the advantages of SBT and Pt, FeRAM capacitors are degraded by mechanical stress, hydrogen damage [3-4], plasma damage [5-6] and so on. In this paper, the effects of reactive ion etching damage on the SBT surface in Pt/SBT/Pt capacitors have been investigated. SBT thin films were damaged by various plasma conditions, and in each case, plasma etching damage was evaluated by measurement of the electrical properties of the Pt/SBT/Pt capacitor. The electrical property results were then correlated with the surface composition of the plasma treated SBT layers. EXPERIMENT All of the samples used in this study were fabricated on the following substrate: Pt(2000A)/Ti(200A)/SiO 2(1oooA)/Si. The Ti adhesion layer and the Pt electrode were deposited by DC sputtering. The SBT layers were prepared using metal organic decomposition method on the surface of the Pt/Ti layers. The crystallization annealing involved heat treatment for for 30 min at 700'C in 02 to form perovskite structure. [7] 155 Mat. Res. Soc. Symp. Proc. Vol. 596 © 2000 Materials Research Society

The top surface of the SBT layers was treated by C12/Ar plasma with various gas ratios in a reactive ion etching (RIE) reactor [8]. To provide a comparison for the effects of plasma etching on electric properties, a reference