Nonconventional growth characteristics of tin silicon oxide grown by thermal atomic layer deposition using H2O as oxidant.

Atomic layer deposition (ALD) of tin silicon oxide was performed via an ALD supercycle on an amorphous carbon (a-C) layer, which serves as the mandrel in self-aligned double patterning (SADP) techniques. This approach addresses limitations of conventional ALD SiO2 processes using ozone (O3) as the oxidant, which can lead to degradation of a-C mandrel or collapse of the SiO2 spacer itself under aggressive scaling. In this study, tetrakis(dimethylamino)tin (TDMASn) and bis-diethylaminosilane (BDEAS) were used as Sn and Si precursors, respectively, with H2O as the oxidant to avoid damage to the a-C layer. SiO2 was not grown via a single ALD process due to the low reactivity of BDEAS with H2O. Nevertheless, x-ray photoelectron spectroscopy analyses revealed that Si was incorporated into the film grown by the supercycle of ALD SnOx and SiO2. Notably, it is observed that the growth characteristics of tin silicon oxide exhibited a nonlinear dependence on the cycle ratio. Understanding this unexpected behavior is crucial for SADP, as it affects growth per cycle and film characteristics, such as etch rate and surface roughness. Fourier-transform infrared spectroscopy and density functional theory calculations suggest that hydrogen abstraction between TDMASn and Si-H groups enable the growth of tin silicon oxide. Finally, transmission electron microscopy analysis demonstrated that the a-C layer remained undamaged during the ALD process, whereas a few seconds of ozone exposure caused the ashing of the a-C layer.