Passivation and stability of thermal atomic layer deposited Al₂O₃ on CZ-Si

Atomic layer deposited (ALD) aluminum oxide (Al₂O₃) has been known as an almost-perfect candidate of passivation dielectric layer for PERC-type c-Si solar cell. Its passivation performance and thermal stability are key issues for industrial PERC c-Si solar cell based on screen-printed technology. In this paper, 20 nm and 30 nm Al₂O₃ films are synthesized on the solar grade CZ-Si by thermal atomic layer deposition. The results show that the effective lifetime can reach 100 μs for CZ-Si after annealing and is kept a half after the sintering process in the industrial beltline furnace, and the materials can be used in PERC-type solar cell. The SEM image demonstrates that the blisters occur in a thicker Al₂O₃ film, which explains why the passivation and thermal stability of 30 nm film are inferior to those of 20 nm film.