Hydrogen atom assisted ALE of silicon

Two ALE methods of Si are successfully demonstrated, where H atoms play an essential role. In the first method, H atoms are used as self-limiting species over the grown layer. Si3H8 was used as source gas and the substrate temperature was modulated in order to switch two steps, i.e. an adsorption step and a desorption step, in an ALE cycle. When the temperature was lower than 380°C in the adsorption step and higher than 520°C in the desorption step, the grown layer thickness per cycle was saturated at 0.8 ML/cycle, closer to the ideal value than in the SiH4 or Si2H6 cases. In the second method, atomic H is used as an active reducer of the self-limiting species. SiH2Cl2 as source gas and atomic H were irradiated to the surface, alternately. An ideal monolayer growth per cycle was obtained with the substrate temperature over 540°C, much lower than in the case of the molecular H2 reducer.