Al2O3/SiNx Stacks with Ozone-based ALD Al2O3 for Surface Passivation: Superior Layer Stability after Firing


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Duman E. S. , Richter A., Reichel C., Fittkau J., Le Tiec C., Moldovan A., ...More

11th International Conference on Crystalline Silicon Photovoltaics (SiliconPV), ELECTR NETWORK, 19 - 23 April 2021, vol.2487 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 2487
  • Doi Number: 10.1063/5.0090639
  • Country: ELECTR NETWORK
  • Middle East Technical University Affiliated: No

Abstract

We present a systematic study on effective passivation of p-type crystalline silicon (c-Si) by Al2O3 and Al2O3/SiNx stacks. Ozone-based atomic layer deposition (ALD) Al2O3 was deposited with varied thickness, ozone concentration and deposition temperature. Thermal stability of fabricated samples was investigated systematically varying post-deposition thermal treatments, such as forming gas annealing (FGA) and fast firing. Blister free Al2O3/SiNx stacks were obtained for Al2O3 thicknesses between 3.5-10 nm yielding effective charge carrier lifetimes (tau(eff)) above 1.5 ms, which correspond to an implied open-circuit voltage (iV(oc)) above 730 mV. The best performing Al2O3 layers in terms of their passivation quality, deposition uniformity and firing stability after being capped by SiNx were obtained when a low ozone concentration was utilized in the ALD process. As no additional out-gassing process is necessary between ALD Al2O3 and PECVD SiNx deposition, these ozone-based ALD Al2O3 layers have the potential to simplify the rear-side passivation of PERC solar cells in mass production.