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1‐μm‐thick polycrystalline BaSi2 films have been fabricated on glass substrate by sputtering BaSi2 target at 600 °C. From the transmission spectrum, we found that the indirect absorption edge was approximately 1.25 eV and the refractive index was 4.0 for long wavelengths. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Ruthenium thin films were deposited at 260-400°C on hole substrates by metallorganic chemical vapor deposition ͑MOCVD͒ using ͑2,4-dimethylpentadienyl͒͑ethylcyclopentadienyl͒ruthenium ͓Ru͑DMPD͒͑EtCp͔͒ for the Ru source. The microstructure, conformability, crystallinity, and resistivity of the films were examined. Conformal films whose resistivity was below 30 ⍀-cm were deposited below 300°C on SiO 2 /TiAlN/Ti/SiO 2 /Si͑100͒ hole substrates with aspect ratio of 1.7. Finally, conformal films with a step coverage of 97% were deposited on SiO 2 /Si hole substrates, even those with a high aspect ratio of 6.4, by using Ru͑DMPD͒͑EtCp͒ without a seed layer.Ruthenium, iridium, their oxides, and platinum were investigated as capacitor electrodes of tantalum pentoxide ͑Ta 2 O 5 ͒ and barium strontium titanate ͓BST: ͑Ba,Sr͒TiO 3 ͔ for gigabit-scale dynamic random access memories ͑DRAMs͒. Among these materials, Ru is considered the most promising because of its low resistivity, excellent chemical stability, and good dry etching property. In gigabit DRAMs, three-dimensional capacitors are unavoidable even if BST with higher permittivity than Ta 2 O 5 is used as a capacitor dielectric. 1 Therefore, metallorganic chemical vapor deposition ͑MOCVD͒ is an indispensable technique for film preparation of both Ru electrodes and capacitor dielectrics because it creates good conformability.There are many reports on Ru sources for MOCVD, including triruthenium dodecacarbonyl ͓Ru 3 ͑CO͒ 12 ͔, 2 bis͑cyclopen-tadienyl͒ruthenium ͓RuCp 2 ͔, 2 tris͑acetylacetonato͒ruthenium ͓Ru͑C 5 H 7 O 2 ͒ 3 ͔, 2 ruthenium tetraoxide ͓RuO 4 ͔, 3 tris͑dipyvaloyl-methanato͒ruthenium ͓Ru͑DPM͒ 3 ͔, 4 and tris͑2,4-octadionato͒ruthenium ͓Ru͑OD͒ 3 ͔. 5 Among these materials, Ru͑EtCp͒ 2 has received more attention than the others because it has a high vapor pressure and is in a liquid state with low viscosity ͑ϳ5 cP͒ at room temperature. 6 However, there are several reports about the drawbacks of Ru͑EtCp͒ 2 , 7,8 including the incubation time, which is the delay in deposition starting at the initial growth stage. Creating precise thicknesses for the Ru film depositions took an unpredictable amount of and undesirably long deposition time. This is a serious barrier to mass production of semiconductor devices. To avoid a lengthy incubation time, Ru films using Ru͑EtCp͒ 2 need a Ru seed layer prepared by a physical vapor deposition ͑PVD͒ method such as sputtering. Furthermore, without a Ru seed layer, Ru films using Ru͑EtCp͒ 2 cannot be deposited stably.Our group 9 proposed a novel precursor, ͑2,4-dimethylpentadienyl͒͑ethylcyclopentadienyl͒ruthenium ͓Ru͑DMPD͒͑EtCp͒, DMPD: 2,4-dimethylpentadienyl͔. Ru͑DMPD͒͑EtCp͒ showed sufficient physical properties as a MOCVD precursor, including sufficient stability, fine volatility, and low viscosity. The Ru films deposited using this precursor showed better characteristics than those using Ru͑EtCp͒ 2 , including a shorter incubation time, smoother surface, and higher nucleation density at the initial growth stage of deposition. In ad...

We deposited an RuO2/Pb(Zr0.40Ti0.60)O3/RuO2 capacitor by metalorganic chemical vapor deposition. RuO2 and Pb(Zr0.40Ti0.60)O3 films were prepared at 350, 395, and 445 °C from respective Ru(C7H11)(C7H9)–O2 and Pb(C11H19O2)2–Zr(O⋅t-C4H9)4–Ti(O⋅i-C3H7)4–O2 systems. Good ferroelectricity was observed for PZT films deposited at 445 °C but not at 395 °C. However, we obtained ferroelectricity with a remanent polarization above 30 μC/cm2 by inserting a 10-nm-thick sputtered-Pt layer between the PZT and RuO2 bottom electrodes, which improved the crystallinity of PZT films even those deposited at 395 °C. This capacitor had hardly any fatigue after 1×1010 switching cycles. This demonstrates the possibility of preparing fatigue-free capacitor all deposited below 400 °C for high-density ferroelectric random-access memory applications.