Effects of Pre‐annealing on Firing Stability of Atomic Layer‐Deposited Al 2 O 3

Al 2 O 3 layers fabricated with atomic layer deposition (ALD) show high levels of surface passivation on p‐ and n‐type silicon wafers. In order to form front and rear electrodes, Al 2 O 3 layers should undergo a firing process at a high peak temperature. Therefore, the Al 2 O 3 layer must be stable under these conditions to maintain a high level of surface passivation during the firing process. In this study, Al 2 O 3 layers fabricated with ALD were pre‐annealed to enhance their thermal stability during the firing process. From quasi‐steady state photoconductance (QSSPC) measurements, the difference between the implied V oc values of the pre‐annealed and fired samples was found to be smallest (3 mV) when the sample was pre‐annealed at 620 °C. The surface recombination rate calculated from capacitance‐voltage ( C ‐ V ) measurements of metal‐Al 2 O 3 ‐Si (metal‐insulator‐semiconductor) structures was shown to be low when the sample was pre‐annealed at 600–650 °C. Thus, firing stability was achieved with pre‐annealing at 620 °C by reducing the surface recombination rate. We conclude that it is necessary to pre‐anneal the Al 2 O 3 passivation layer at this specific temperature to reduce the degradation of the passivation quality of Al 2 O 3 after the firing process.