The ever-shrinking dimensions of dynamic random access memory (DRAM) require a high quality dielectric film for capacitors with a sufficiently high growth-per-cycle (GPC) by atomic layer deposition (ALD). SrTiO 3 (STO) films are considered to be the appropriate dielectric films for DRAMs with the design rule of ∼20 nm, and previous studies showed that STO films grown by ALD have promising electrical performance. However, the ALD of STO films still suffers from much too slow GPC to be used in mass-production. Here, we accomplished a mass-production compatible ALD process of STO films using Ti(O-i Pr) 2 -(tmhd) 2 as a Ti-precursor for TiO 2 layers and Sr( i Pr 3 Cp) 2 as a Sr-precursor for SrO layers. O 3 and H 2 O were used as the oxygen sources for the TiO 2 and SrO layers, respectively. A highly improved GPC of 0.107 nm/unit-cycle (0.428 nm/supercycle) for stoichiometric STO films was obtained at a deposition temperature of 370 °C, which is ∼7 times higher than previously reported. The origin of such high GPC values in this STO films could be explained by the partial decomposition of the precursors used and the strong tendency of water adsorption onto the SrO layer in comparison to the TiO 2 layer. The STO film grown in this study also showed an excellent step coverage (∼95%) when deposited inside a deep capacitor hole with an aspect ratio of 10. Owing to the high bulk dielectric constant (∼ 146) of the STO film, an equivalent oxide thickness of 0.57 nm was achieved with a STO film of 10 nm. In addition, the leakage current density was sufficiently low (3 Â 10 À8 Acm À2 at þ0.8 V). This process is extremely promising for fabrication of the next generation DRAMs.

RuO 2 thin films were grown on thermal SiO 2 (100 nm) and Ta 2 O 5 (4 nm)/SiO 2 (100 nm) substrates at 230°C by pulsed-chemical vapor deposition using a RuO 4 precursor dissolved in blend of chosen organic solvent (with fluorinated solvents) and 95% N 2 /5% H 2 mixed gas as the Ru precursor and reactant gas, respectively. The phase of the deposited film, either being RuO 2 or Ru, was controlled by the N 2 /H 2 mixed gas feeding time. This was due to the fact that the time constant of the N 2 /H 2 mixed gas for oxygen atom removal from the reaction surface was related to the reaction kinetics even under identical thermodynamic conditions. High-quality RuO 2 films could be deposited at the N 2 /H 2 gas feeding time of 1-10 s, whereas a Ru film was grown with longer N 2 /H 2 gas feeding times of >15 s. The saturated growth rate and resistivity of the RuO 2 thin films were 0.24 nm/cycle and ∼250 μΩ cm, respectively. Although the fundamental growth mechanism of the RuO 2 film was based on selfdecomposition of the RuO 4 precursor, the N 2 /H 2 reactant feeding served to enhance RuO 2 growth by the surface hydroxyl group-mediated chemisorption of the RuO 4 precursor. The RuO 2 film showed excellent step coverage inside a capacitor hole structure with an aspect ratio of 10 (opening diameter: 100 nm).

The dielectric constant, equivalent oxide thickness (tox), and leakage current properties of Pt/(Al-doped)TiO2/RuO2 capacitors were examined in comparison with Pt/(Al-doped)TiO2/Ru capacitors. The Al-doped TiO2 and undoped TiO2 films grown on RuO2 showed high dielectric constants of 60 and 102, respectively. The minimum tox of these films were 0.46 nm and 0.56 nm, respectively, while still satisfying the dynamic random access memory leakage current density specification (< 1 × 10−7 Acm−2 at capacitor voltage of 0.8 V). These excellent electrical properties of (Al-doped) TiO2 on RuO2 were attributed to the high work function and the reduced interfacial effect on RuO2.

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