Investigation of interface characteristics of Al2O3/Si under various O2 plasma exposure times during the deposition of Al2O3 by PA-ALD

Plasma-assisted atomic layer deposition (PA-ALD) is more suitable than thermal atomic layer deposition (ALD) for mass production because of its faster growth rate. However, controlling surface damage caused by plasma during the PA-ALD process is a key issue. In this study, the passivation characteristics of Al₂O₃ layers deposited by PA-ALD were investigated with various O₂ plasma exposure times. The growth per cycle (GPC) during Al₂O₃ deposition was saturated at approximately 1.4?Å/cycle after an O₂ plasma exposure time of 1.5?s, and a refractive index of Al₂O₃ in the range of 1.65–1.67 was obtained. As the O₂ plasma exposure time increased in the Al₂O₃ deposition process, the passivation properties tended to deteriorate, and as the radio frequency (RF) power increased, the passivation uniformity and the thermal stability of the Al₂O₃ layer deteriorated. To study the Al₂O₃/Si interface characteristics, the capacitance-voltage (C-V) and the conductance-voltage (G-V) were measured using a mercury probe, and the fixed charge density (Q_f) and the interface trap density (D_it) were then extracted. The Q_f of the Al₂O₃ layer deposited on a Si wafer by PA-ALD was almost unaffected, but the D_it increased with O₂ plasma exposure time. In conclusion, as the O₂ plasma exposure time increased during Al₂O₃ layer deposition by PA-ALD, the Al₂O₃/Si interface characteristics deteriorated because of plasma surface damage.