Process Temperature Dependence of Al2O3 Film Deposited by Thermal ALD as a Passivation Layer for c-Si Solar Cells

This paper presents a study of the process temperature dependence of Al2O3 film grown by thermal atomic layer deposition (ALD) as a passivation layer in the crystalline Si (c-Si) solar cells. The deposition rate of Al2O3 film maintained almost the same until 250 degrees C, but decreased from 300 degrees C. Al2O3 film deposited at 250 degrees C was found to have the highest negative fixed oxide charge density (Qf) due to its O-rich condition and low hydroxyl group (-OH) density. After post-metallization annealing (PMA), Al2O3 film deposited at 250 degrees C had the lowest slow and fast interface trap density. Actually, Al2O3 film deposited at 250 degrees C showed the best passivation effects, that is, the highest excess carrier lifetime (tau(PCD)) and lowest surface recombination velocity (S-eff) than other conditions. Therefore, Al2O3 film deposited at 250 degrees C exhibited excellent chemical and field-effect passivation properties for p-type c-Si solar cells.