The impact of deposition and annealing temperature on the growth properties and surface passivation of silicon dioxide films obtained by atomic layer deposition

Abstract

This paper studies the impact of deposition and annealing temperature on the growth properties and surface passivation of silicon dioxide (SiO2) films obtained by atomic layer deposition (ALD) using tris(dimethylamino)-silane (TDMAS) precursor. Increasing in deposition temperature from 200 to 350 °C alters the growth rate and refractive index significantly. The ALD-SiO2 films deposited at over 250 °C obtain excellent surface passivation after annealing at 650 °C, which could be explained by the synergistic effects of chemical and field-effect passivation caused by low interface defect states density (Dit) and high positive fixed charges density (Qf), respectively. Meanwhile, the effect of deposition temperature on surface passivation depends on the extent of TDMAS chemical adsorption and dissociation during ALD. X-ray photoelectron spectroscopy (XPS) shows low temperature as-deposited SiO2 films contain higher carbon impurities because of the remained dimethylamine groups. Regarding the impact of annealing temperature on surface passivation, secondary ion mass spectroscopy profiles and XPS results reveal that high-temperature annealing probably forms more hydrogen and oxygen vacancies at SiO2/Si interface, causing a decrease in Dit and an increase in positive Qf, respectively. This work provides a reference for applying ALD-SiO2 films to surface passivation technology of crystalline silicon solar cells.