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

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 AlO_x were studied. High-quality surface passivation with S_max of ∼10cm/s was obtained from the AlO _x 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 ' 10¹²cm^-2 and chemical passivation, which reduces the interface trap density to ∼1 ' 10 ¹¹ eV%1cm^-2. The annealed AlO_x samples deposited at 200 °C also show high thermal stability during firing at 850 °C. Additionally, we found that the formation of a thin SiO_x 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/SiO_x interface by diffused hydrogen from AlO_x layers is the origin of chemical passivation.