Mechanistic study of atomic layer deposition of AlxSiyO thin film via in-situ FTIR spectroscopy

A study of surface reaction mechanism on atomic layer deposition (ALD) of aluminum silicate (AlxSiyO) was conducted with trimethylaluminum (TMA) and tetraethoxysilane (TEOS) as precursors and H2O as the oxidant. In-situ Fourier transform infrared spectroscopy (FTIR) was utilized to elucidate the underlying surface mechanism that enables the deposition of AlxSiyO by ALD. In-situ FTIR study revealed that ineffective hydroxylation of the surface ethoxy (-OCH2CH3) groups prohibits ALD of SiO2 by TEOS/H2O. In contrast, effective desorption of the surface ethoxy group was observed in TEOS/H2O/TMA/H2O chemistry. The presence of Al-OH* group in vicinity of partially hydroxylated ethoxy (-OCH2CH3) group was found to propagate dis-proportionation reaction, which results in ALD of AlxSiyO. The maximum thickness from incorporation of SiOx from alternating exposures of TEOS/H2O chemistry in AlxSiyO was found to be similar to 2 angstrom, confirmed by high resolution transmission electron microscopy measurements. (C) 2015 American Vacuum Society.