Atomic Layer Deposition of Ruthenium and Ruthenium Oxide Thin Films from a Zero-Valent (1,5-Hexadiene)(1-isopropyl-4-methylbenzene)ruthenium Complex and O₂

Ruthenium (Ru) and ruthenium oxide (RuO 2 ) thin films were grown by atomic layer deposition (ALD) using a novel zerovalent (1,5-hexadiene)(1-isopropyl-4-methylbenzene)Ru complex and O 2 as the Ru precursor and oxidant, respectively. The self-limiting growth mode for the Ru and RuO 2 ALD processes was achieved while varying the Ru precursor and O 2 feeding time. Metallic Ru films were deposited at growth temperatures of 230–350 °C, while the temperature window for the growth of the RuO 2 film was limited to <230 °C. At 270 °C, the growth per cycle (GPC) of Ru ALD was 0.076 nm/cycle, and the incubation times of Ru on SiO 2 and TiN substrates were considerably short (3 cycles on SiO 2, negligible on TiN) compared to that of Ru ALD from a high-valent Ru precursor and O 2 . The resistivity of the Ru film was as low as 29–36 μΩ·cm at growth temperatures of 270–350 °C. On the other hand, the RuO 2 film was grown at a low temperature of 200 °C and showed a GPC of 0.15 nm/cycle with a resistivity of ∼270 μΩ·cm. In situ quadruple mass spectrometry analysis of the CO 2 byproduct revealed that the amount of subsurface oxygen extracted during the Ru pulse half-cycle affected the resultant film phase, either Ru or RuO 2, which was strongly influenced by the growth temperature.