Detailed study of the effects of interface properties of ozone-based atomic layer deposited AlOx on the surface passivation of crystalline silicon

Abstract

The effects of interface properties such as a negative fixed charge density and an interface trap density on the surface passivation of crystalline Si by O3-based batch ALD AlOx were studied. High-quality surface passivation with Smax of ∼10 cm/s was obtained from the AlOx samples deposited at 200 °C after annealing. This feature is attributed to the excellent field effect passivation by the high negative fixed charge density of ∼−5 × 1012 cm−2 and chemical passivation, which reduces the interface trap density to ∼1 × 1011 eV−1 cm−2. The annealed AlOx samples deposited at 200 °C also show high thermal stability during firing at 850 °C. Additionally, we found that the formation of a thin SiOx interlayer is essential for the formation of a high negative fixed charge density that induces strong field effect passivation, and that defect passivation at the Si/SiOx interface by diffused hydrogen from AlOx layers is the origin of chemical passivation.