Boron Spin-On Doping for Poly-Si/SiOx Passivating Contacts

Herein, we fabricate and characterize p-type passivating contacts based on industrial intrinsic polycrystalline silicon (poly-Si)/thermal-SiOx/n-type crystalline Si (c-Si) substrates using a spin-on doping technique. The impacts of drive-in temperature, drive-in dwell time, and intrinsic poly-Si thickness on the boron-doped poly-Si passivating contacts are investigated. First, the contact passivation quality improves with an increasing thermal budget (<950 °C) but then decreases again for excessive thermal annealing (>950 °C). Second, the thickness of the intrinsic poly-Si film shows only a little impact on the performance. After a hydrogenation treatment by depositing an AlOx/SiNx stack and subsequent annealing in forming gas, the optimized poly-Si passivating contacts show an implied open-circuit voltage (iVoc) > 720 mV, together with a contact resistivity (ρc) below 5 mΩ cm2. These results demonstrate that boron spin-on doping is a promising alternative to the conventional BBr3 thermal diffusion for the fabrication of p-type poly-Si passivating contacts.