MOCVD of Ir and IrO 2 Thin Films for PZT Capacitors
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MOCVD OF Ir AND IrO2 THIN FILMS FOR PZT CAPACITORS M.Shimizu*, K.Kita, H.Fujisawa and H.Niu Department of Electronics, Faculty of Engineering, Himeji Institute of Technology, 2167 Shosha, Himeji, Hyogo 671-2201, Japan * [email protected] ABSTRACT Ir films were prepared on SiO2/Si at 275-500oC by MOCVD (Metalorganic Chemical Vapor Deposition) using a new Ir precursor, Ir(EtCp)(cod) (iridium(ethylcyclopentadienyl) (1,5-cyclooctadiene) : Ir(C2H5C5H4)(1,5-C8H12). Ir films prepared at 275-300oC showed highly reflecting surfaces with Rrms roughness (root-mean-square roughness) of 1.4-10nm. At 500oC, Ir and IrO2 mixture-oriented films were grown. Ir films deposited at 300oC on patterned SiO2/Si substrates with aspect ratios of 0.3-2.0 showed good step coverage of 70-85%. Auger analysis revealed that Ir film had no incorporation of carbon and oxygen, and that Ir films performed well as a diffusion barrier in PZT/Ir/SiO2/Si structure. INTRODUCTION A variety of metal and conductive oxide materials has been reported for electrode and barrier materials of non-volatile ferroelectric random access memories (FeRAMs) and high density dynamic random access memories (DRAMs). The choice of electrode materials is one of most important key issues because electrical properties are strongly influenced by electrode materials. Among many materials, Ir and IrO2 have been extensively investigated since the report on fatigue free PZT capacitors with Ir/IrO2 composite electrodes in 1994 [1,2]. Good diffusion barrier properties, good electrical conductivity and high resistance to hydrogen atmosphere make them promising candidates for electrode and barrier materials [3-6]. In general, Ir and IrO2 films have been prepared by the sputtering method due to its convenience and commercial-based production. However, for the realization of future FeRAMs and DRAMs with a three dimensional stack structure, metalorganic chemical vapor deposition (MOCVD) technique will be indispensable because of its highly conformal growth, high growth rate, relatively low deposition temperature and compatibility of LSI process. There have been several reports on the MOCVD of Ir films. A variety of Ir precursors were used in these reports to prepare Ir films, such as IrCp(cod) (Cp : cyclopentadienyl, cod : 1,5-cyclooctadiene) [7], Ir(MeCp)(cod) (Me : CH3) [7-9], Ir(acac)3 (acac : acetyacetonate) [10-13], Ir(thd)(cod) (thd : 2,2,6,6-tetramethyl-3,5-heptanedionate) [13,14]. These precursors are solid and have a low vapor pressure. Therefore, the sublimation method [7,10-14] and liquid delivery method [8] were used. In this study, we used a new Ir precursor, Ir(EtCp)(cod) (Ir(C2H5C5H4)(1,5-C8H12)), to CC1.10.1
prepare Ir and IrO2 films. This precursor is liquid at room temperature and has a higher vapor pressure than those Ir precursors mentioned above. Crystalline properties, surface morphology, step coverage and diffusion barrier characteristics of MOCVD-Ir films are described. EXPERIMENTS In our experiments, a new Ir precursor, Ir(EtCp)(cod), was used
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