A Novel Iridium Precursor for MOCVD
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A Novel Iridium Precursor for MOCVD Kazuhisa Kawano, Mayumi Takamori1, Tetsu Yamakawa1, Soichi Watari2, Hironori Fujisawa2, Masaru Shimizu2, Hirohiko Niu2 and Noriaki Oshima Tokyo Research Laboratory, TOSOH Corporation, Hayakawa 2743-1, Ayase, Kanagawa 252-1123 Japan 1 Sagami Chemical Research Center, Hayakawa 2743-1, Ayase, Kanagawa 252-1193 Japan 2 Department of Electrical Engineering and Computer Sciences, Graduate School of Engineering, Himeji Institute of Technology Shosha 2167, Himeji, Hyogo 671-2201, Japan ABSTRACT A novel liquid iridium precursor (1,3-cyclohexadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(CHD), was synthesized and its physical properties were examined. Ir(EtCp)(CHD) exhibited enough vapor pressure (0.1 Torr/75°C), excellent volatility and adequate decomposition temperature. Characteristics of the Ir films deposited using Ir(EtCp)(CHD) and the conventional Ir precursor (1,5-cyclooctadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(COD), by metal-organic chemical vapor deposition (MOCVD) method were compared. Ir films grown using Ir(EtCp)(CHD) showed shorter incubation time and higher nucleation density than those of films using Ir(EtCp)(COD).
INTRODUCTION Iridium (Ir), ruthenium (Ru), platinum (Pt) and their oxides have been investigated as the capacitor electrodes of next generation memory devices including ferroelectric random access memories (FeRAMs). Among these noble metals, Ir and IrO2 are especially attractive material for the electrodes of FeRAMs, because they were excellent barriers to oxygen diffusion and are effective for the improvement of fatigue loss of PZT capacitors. For the realization of the three-demensional memory devices, more attention comes to be paid to MOCVD method. There have been several reports on Ir and IrO2 films by MOCVD using (1,5-cyclooctadiene)(cyclopentadienyl)iridium(I), Ir(Cp)(COD), [1] (1,5-cyclooctadiene) (methylcyclopentadienyl)iridium(I), Ir(MeCp)(COD), [1-3], Tris(acetylacetonato)iridium(III), Ir(acac)3, [4-7], (1,5-cyclooctadiene)(2,2,6,6-tetramethyl-3,5-heptanedionate)iridium(I), Ir(thd)(COD), [7,8] and Ir(EtCp)(COD) [9]. Among them, Ir(EtCp)(COD) was intensively investigated because it have higher vapor pressure than other solid precursors described above and is a liquid at room temperature. Liquid precursors are of great advantage to MOCVD method from the viewpoint of material delivery system. Ir(EtCp)(COD) which has the rigid structure is very stable under the MOCVD conditions. When growth condition was optimized, Ir films with good step coverage or conformal films were deposited. However it was difficult to deposit iridium oxide thin film with Ir(EtCp)(COD) by MOCVD so far.
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(a)
(b) Ir
Ir
Figure 1 Molecular structure of (a) Ir(EtCp)(CHD) and (b) Ir(EtCp)(COD) In this work, we report the synthesis and characterization of Ir(EtCp)(CHD) and the thermal properties. Characteristics of the Ir films deposited from Ir(EtCp)(CHD) were compared with those from Ir(EtCp)(COD).
EXPERIMENT Molecular structure of Ir(EtCp)(CHD) and Ir(EtC
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