Structure Analyses of Room Temperature Deposited AlO_x Passivation Films for Crystalline Silicon Solar Cells

We studied the structure of ozone-based atomic layer deposited aluminium oxide (AlO_x) films as a passivation layer for p-type crystalline silicon (c-Si) solar cells and focused on the differences in the structure by the production conditions of AlO_x films. Carbon (C)-related groups such as methyl, hydroxyl, and carboxyl groups which originate from the aluminium source, trimethylaluminium, were only found in the AlO_x film deposited at room temperature (RT-sample). By post-deposition thermal annealing (PDA), the C-related groups were desorbed from the film and a part of their space remained as voids. The C-related groups were not found in the films deposited at 200 or 300 °C (heated-samples) since they were desorbed during the deposition. Even though C-related groups did not exist in the both RT- and heated-samples after PDA, the structure of the AlO_x film of the RT-sample was different from that of the heated-sample.