Impact of annealing towards anti-reflection properties of AI₂O₃ on silicon

This paper investigates the impact of annealing towards the anti-reflection properties of aluminium oxide (Al₂O₃) on planar monocrystalline silicon (mono c-Si) wafers. Al₂O₃ anti-reflection coating (ARC) with 120 nm thickness is deposited on the c-Si wafers by radio frequency (RF) sputtering process at room temperature, with the power of 200 Watt and at a base pressure of 5×10-5 mbar. This is followed by annealing at different temperatures (700-900 oC) for 20 min. The results show that the root means square (RMS) surface roughness of the Al₂O₃ increases with increased annealing temperature. The Al₂O₃ films with annealing illustrate lower broadband reflection than the Al₂O₃ without annealing within the 300-1100 nm wavelength region. The Al2O3 film annealed at 900 oC exhibits the lowest reflection (6%) and the highest absorption (94%) at a wavelength of 600 nm with an average weighted reflection (AWR) of 20.4%, owing to the high RMS roughness and the effect of the intermediate refractive index of the Al₂O₃ layer. This results in a maximum potential short-circuit current density (Jsc(max)) of 37.3 mA/cm², which corresponds to a 5.4% enhancement compared to the Al₂O₃ on planar c-Si without an annealing process.