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 disproportionation 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 ∼2 Å, confirmed by high resolution transmission electron microscopy measurements.