Influence of Process Parameters on the Surface Passivation Quality of Phosphorus Doped Polysilicon Contacts Deposited by APCVD

Doped polycrystalline silicon (poly-Si) passivating contacts featuring a thin tunneling oxide have emerged as one of the most promising carrier selective contacts for crystalline silicon (c-Si) solar cells due to their very low recombination and resistive losses, as well as a high thermal stability compared to amorphous silicon (a-Si:H) heterojunctions. This contact technology consists of a heavily doped poly-Si layer on top of a c-Si substrate with an interfacial ultra-thin silicon oxide layer (SiO
x
). To implement poly-Si passivating contacts into an industrial silicon solar cell production line, a cost-effective and high-throughput deposition process is required. Atmospheric pressure chemical vapor deposition (APCVD) process is a single side deposition process that requires no vacuum or plasma systems and is very well suited for high volume manufacturing. In this work, we present an in-line APCVD process for depositing heavily phosphorus doped poly-Si films to form low recombination electron contacts using silane (SiH
4
) and phosphine (PH
3
) as precursor gases. The as-deposited samples went through different post deposition annealing processes for solid phase crystallization, dopant activation and dopant diffusion. We have studied the effect of different process parameters like deposition temperature, precursor gas ratio and different post deposition treatments etc. on the surface passivation quality of this contact.