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D3.18.1

Influence of Pre-Oxidation of an Ir Film on Chemical Composition and Crystal Property of a PZT Film Deposited on the Ir Film by Sputtering Susumu Horita and Makoto Shoga Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Tatsunokuchi, Ishikawa, JAPAN

ABSTRACT We investigated the influence of pre-oxidation of an Ir film as a bottom electrode on the chemical composition and crystal property of the PZT film deposited on it by RF sputtering, changing the sputtering target composition ratio Zr/Ti to be 20/80, 52/48 or 80/20. The Ir film deposited on a thermally oxidized Si substrate was pre-oxidized at 600°C for 20 min in the O2 gas of 10 Pa. The XRD patterns showed a strong PbO(101) peak from the PZT film on the oxidized Ir film for Zr/Ti = 52/48, but no PbO peak from the film on a no oxidized Ir film. The RBS measurement showed that the film composition ratio of Pb/(Zr+Ti) on the pre-oxidized Ir film was much larger than that on the no oxidized Ir film. For Zr/Ti=20/80, the same tendency was observed. However, for Zr/Ti=80/20, the chemical composition of the PZT film on the pre-oxidized Ir film was almost equal to that without oxidation. INTRODUCTION Pb(ZrxTi1-x)O3(PZT) has recently been widely studied as a promising material for capacitors in ferroelectric random-access memories (FRAMs) and gate dielectric insulators in metal/ferroelectric/semiconductor field-effect tran-sistors (MFS-FETs). In order to improve fatigue endurance of the PZT film, Ir and Ir oxide are used as an electrode material [1,2]. Since the surface property of metallic Ir are considerably different from that of Ir oxide, it can be expected that the growth condition to obtain a perovskite PZT film on the metallic Ir film are also quite different from that on the Ir oxide film. Therefore, we investigated the influence of pre-oxidation of the Ir film on the chemical composition and crystal property of the PZT film deposited on it by RF sputtering, comparing with those of the PZT film deposited on the no oxidized Ir film. In this paper, we show that the Pb content in the PZT film on the oxidized Ir film is much larger than that on the no oxidized film. It is, also, shown that the composition ratio of Pb/(Zr+Ti) in the PZT film depends on the sputtering target composition ratio Zr/Ti. The results are discussed briefly. EXPERIMENTAL The sputtering for deposition of Ir and PZT films was carried out after evacuation to a pressure less than 1×10-5 Pa. The n-type (100) Si substrate was chemically cleaned by so-called RCA treatment, a ~10-nm-thick thermal SiO2 layer was grown on it at 900°C for 15 min in dry O2 gas. Next, a ~100-nm-thick Ir film was deposited on the SiO2 layer by RF sputtering at the RF power of 21 W and 600°C in the Ar gas of 10 Pa, using a metallic Ir target. The X ray diffraction

D3.18.2

(XRD) pattern of the deposited Ir film showed the preferential orientation of Ir (111). Some Ir films were pre-oxidized at 600°C for 20 min in the O2 gas of 10 Pa prior to depositing a PZT film on it. The PZT film was deposited