Ru films were produced by atomic layer deposition (ALD) with an alternating supply of bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp) 2 ) and ozone at deposition temperatures of 225-275 • C. Ozone acted as an effective reactant for Ru(EtCp) 2 . The Ru film thicknesses formed during one cycle were saturated at relatively high values of 0.09-0.12 nm/cycle depending on the deposition temperatures, and their resistivities were about 16 μ cm. Moreover, a reduced nucleation delay was found for Ru ALD using ozone when compared to Ru ALD using oxygen gas. The amount of oxygen impurity incorporated into the Ru films was less than 1 at%, as determined by Auger electron spectroscopy. The interfacial adhesion property between Ru films prepared via ALD using ozone (ozone-Ru) and ZrO 2 was good and 80% step coverage was achieved on a 3-D structure with a very high aspect ratio of 16:1, making them suitable for use as a top electrode material.As the minimum feature size of semiconductor devices decreases, the dimensions of the memory cells also decrease. To maintain the required cell capacitance (25-30 fF/cell) in dynamic random access memory (DRAM) with design rules of 45 nm or less, high-k dielectric materials, such as ZrO 2 , TiO 2 , Ta 2 O 5 , SrTiO 3 , and (Ba,Sr)TiO 3 , have been extensively investigated. [1][2][3][4][5][6][7][8][9] For this application to be successful, the choice of a suitable capacitor electrode material is very important. The capacitor electrode material should not react with oxygen. Moreover, a compatible etching process, good morphological stability, and reliable adhesion properties are also required when applying such materials in electronic devices. The noble metals, such as Pt and Ru, are preferentially considered for use as electrode materials. 6-12 In addition to high work functions, these noble metals have sufficiently low resistivities that ultrathin films can be employed. Furthermore, these noble metals are able to minimize the device's leakage current, and they appear to have better chemical compatibility with the dielectrics than more conventional capacitor electrode materials such as TiN. In particular, Ru, which has a work function of 4.7 eV and a bulk resistivity of 7.1 μ cm, is preferred from a device integration perspective, as it can be dry etched relatively easily, unlike Pt. 13,14 Moreover, Ru is chemically stable toward oxygen and can block the diffusion of oxygen during the fabrication and annealing of dielectrics by forming conductive oxide films of RuO 2 . 15,16 Even though memory is fabricated with high-permittivity dielectrics, it is obvious that complicated three-dimensional (3-D) structures are indispensable for achieving the required cell capacitance in high-density memory. 17, 18 Therefore, good conformal deposition is required from the thin film deposition method used to construct the capacitor electrode. Of the various deposition methods, atomic layer deposition (ALD) is currently under widespread development, because it enables conformal deposition for complicated 3-D st...
