Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Thermal atomic layer deposition (ALD) of noble metals is frequently performed using molecular oxygen as the nonmetal precursor to effect combustion-type chemistry at relatively high temperatures of 300 °C. Bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp) 2 ) is one of the commonly used metal precursors for Ru ALD. Using Ru(EtCp) 2 and oxygen as reactants, Ru ALD was achieved at near 300 °C. Here, we demonstrate that Ru ALD can proceed at as low as 150 °C by using successive exposures to oxygen and hydrogen as the coreactants. In situ quartz crystal microbalance (QCM) and quadrupole mass spectroscopy (QMS) measurements both suggest that this ABC-type ALD occurs through dissociative chemisorption, combustion, and reduction for the Ru(EtCp) 2, oxygen, and hydrogen steps, respectively, in a similar manner to processes using ozone and hydrogen as coreactants reported previously. Moreover, we believe this molecular O 2 and H 2 based ABC-type ALD could be exploited for the ALD of other noble metals to decrease the deposition temperature and reduce oxygen impurities.