Initial surface reactions in atomic layer deposition of HfSi xO y and HfO 2: A comparative study by density functional theory

Abstract

Density functional theory is employed to investigate the reaction mechanism of HfSi x O y and HfO 2 grown by atomic layer deposition (ALD) on H-terminated silicon surface. The ALD process is designed into two reaction sequences based on either hafnium or oxygen precursors as the starting pulses. We find that Si(OCH 3) 4 would be less oxidizing toward silicon surface due to its low adsorption energy and high activation barrier, whereas H 2O is much easier to oxidize the silicon surface and form the OH surface sites. We also find that it is more kinetically and thermodynamically favorable for HfCl 4 adsorption and decomposition on H 2O-pretreated silicon surface than Si(OCH 3) 4-pretreated silicon surface. In conclusion, although silicon alkoxide as oxygen source can limit effectively the formation of SiO 2-rich interfacial layer, it has substantially slow kinetics for HfSi x O y ALD as compared to H 2O for HfO 2 ALD.