Paper TF+EN-MoM3
Process and Materials Optimization for Ru/RuO2 ALD using a Novel Cyclohexadienyl Precursor

Monday, October 18, 2010, 9:00 am, Room Pecos

Ruthenium is of particular interest to the semiconductor industry and others due to its low bulk resistivity (7μٟcm) and high work function (4.7ev). In addition, its complementary oxide, RuO₂, can exhibit high specific capacitance (up to 750 F/g) and conductivity (80-100 µΩŸcm), making it attractive for energy storage applications. We report results for Ru and RuO₂ ALD using a novel Ru cyclohexadienyl precursor and oxygen. This precursor is attractive because it is liquid at room temperature, stable in air and non-reactive with water, while its vapor pressure is similar to that of common ALD Ru precursors RuCp₂ and Ru(EtCp)₂, i.e., 0.1 Torr at 60°C and 1 Torr at 100°C. ALD Ru deposition was achieved in a wafer scale (100mm), cross-flow ALD reactor. Self-limiting ALD surface chemistry is observed between 250-300°C with a growth rate of ~0.5Å/cycle and across-wafer uniformity >98%. Four point probe measurements show a low sheet resistance of 16μٟcm. Ru nucleation is improved compared to RuCp₂ and Ru(EtCp)₂ based processes, with no nucleation delay on SiO₂ or TiO₂, a slight delay on Si, and a significant delay on Al₂O₃. Growth rates are constant with the number of deposition cycles. Conformality studies were conducted using high aspect ratio anodic aluminum oxide (AAO) thin films, using a thin TiO2 nucleation layer before Ru ALD. This Ru ALD process converts to a RuO₂ ALD process at higher oxygen partial pressure, with an oxide conductivity of ~80 µΩŸcm. Post-process thin film characterization using XRD, XPS and AFM will be also presented.

This work was supported by the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center.