Atomic layer deposition of ruthenium using an ABC-type process: Role of oxygen exposure during nucleation

Atomic layer deposition (ALD) of ruthenium is of interest for various applications in nanoelectronics and is currently gaining attention for its potential role in interconnect technology in future technology nodes. This work provides insights into the influence of the O2 pulse time on the film nucleation on SiO2 and on the resulting material properties. Ru thin films were deposited using a three-step ALD process consisting of ethylbenzene(1,3-butadiene)Ru(0) precursor, O2 gas, and H2 gas pulses. It is shown that the addition of an H2 pulse to a conventional two-step process reduces any RuOx formed during the O2 pulse to metallic Ru. This provides the opportunity to employ longer O2 pulses, which enhances nucleation, leading to faster growth initiation and smooth films. Using this process, the deposition of Ru films at 225 °C with a low oxygen impurity level (<4 at. %) and a resistivity of 26 ± 2 μΩ cm is demonstrated. The data illustrate that the dosing time required for saturation during the nucleation phase can substantially deviate from the conditions required for the steady-growth phase.