Preparation of Bi 2 SiO 5 -SrBi 2 Ta 2 O 9 Ferroelectric Thin Films by RF Magnetron Sputtering

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U12.8.1

Preparation of Bi2SiO5 -SrBi2Ta2O9 Ferroelectric Thin Films by RF Magnetron Sputtering Shin Kikuchi1 and Hiroshi Ishiwara 1 R & D Association for Future Electron Devices, Frontier Collaborative Research Center, Tokyo Institute of Technology 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, JAPAN E-mail: [email protected] ABSTRACT Si-added SrBi2Ta2O9 (SBT) ferroelectric films were prepared by RF magnetron sputtering on a Pt/Ti/SiO2/Si (100) structure. The films were deposited at temperatures below 100°C for preventing Bi evaporation and crystallized at 800°C in air. A typical composition was Sr0.79Bi2.37Ta2.00Si0.2Ox. The remnant polarization value( 2Pr) of the Si-added SBT film was 16µC/cm2 and leakage current density was 5x10-8A/cm2. The current density was significantly decreased by adding Si atoms. Key words; SBT; BSO; feroelectric thin film; RF magnetron sputtering; leakage current density INTRODUCTION As modern portable electronic devices such as mobile phones and notebook computers become more and more popular, there is a confirmed increase in the demand for non-volatile memories. FeRAM (ferroelectric random access memories) is one of the most promising candidates, because the power consumption is lowest among various random accesses and read only memories. SrBi2Ta2O9 (SBT) thin film have such important features as a ferroelectric material used for fabrication of FeRAM that the fatigue characteristic of remnant polarization is better and the operation voltage is lower than those of Pb (Zr, Ti)O3 (PZT). Recently, Kijima et. al. developed solid solutions between Bi2SiO5 (BSO) and conventional ferroelectric materials such as SBT, PZT and Bi4Ti3O12 (BIT) formed using a sol-gel spin-coating method, and demonstrated that these materials exhibited excellent ferroelectric properties.1,2 In this work, Si-added SBT thin films are fabricated by RF magnetron sputtering. It is reported that good controllability of the film composition is reasonably good and that the ferroelectric property of Si-added SBT is improved by addition of Si atoms. EXPERIMENTAL DETAILS An RF magnetron sputtering system used in this experiment is illustrated in Figure.1. The system has a loading chamber for preventing moisture absorption on a target and thus a sample is transported from the loading chamber to the sputtering chamber in vacuum using a manipulator. The sample stage in the sputtering chamber is cooled by water flow. Preparation conditions for the Si-added SBT are shown in Table 1. The sputtering target was a sintered ceramic Si-added SBT with a composition of Sr0.67Bi2.64Ta2.00Si0.2Ox and its diameter was 106mm. Sputtering power and Ar pressure were varied from 50 W to 200W and from 0.5Pa to 5.0 Pa, respectively. The Si added SBT films were deposited on Pt/Ti/SiO2/Si substrates. A typical film thickness was 200nm. During deposition, the substrate cooled below 100°C for preventing Bi

U12.8.2

Table1. Preparation conditions of Si-added SBT films Target Substrate

Sr0.67Bi2.64Ta2.00Si0.20 Ox (106mmφ, 5t) Pt/Ti/SiO2/Si,

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