Initial growth analysis of ALD Al2O3 film on hydrogen-terminated Si substrate via in situ XPS

The initial stage of Al2O3 films deposited by atomic layer deposition (ALD) on a H-terminated Si(001) wafer was investigated with in situ X-ray photoelectron spectroscopy. At deposition temperatures of 250 degrees C and 300 degrees C, no Al peak was detected for the first 10 ALD cycles. An Al peak was first observed at ALD cycle 12, and its intensity increased with increasing ALD cycle number. The 10 initial ALD cycles were defined as an incubation period. The Si 2p and Al 2p narrow spectra indicated that Si sub-oxide formed during the incubation period and trimethylaluminum (TMA) adsorbed on it after the incubation period. The incubation period at a growth temperature of 350 degrees C decreased to five ALD cycles because the H2O exposure at a higher temperature promoted the oxidation of the H-terminated Si surface and formed Si sub-oxide.