Thermal activation of hydrogen for defect passivation in poly-Si based passivating contacts

Abstract

Hydrogenation of poly-Si based passivating contacts (TOPCon) is an essential process to achieve a very high level of surface passivation, especially on textured surface. This contribution is dedicated to improve the understanding of the hydrogenation mechanism. We compare different hydrogen sources with regard to their ability to chemically passivate defects at the Si/SiO x interface and presumably in the doped poly-Si layer as well as their thermal stability in a low and high temperature range. To this end, hotplate annealing series were performed on textured n -type TOPCon structures and Al 2 O 3 /SiN x multi-layer stacks were exposed to fast-firing processes. Very distinct activation characteristics were detected. It was also observed that the Al 2 O 3 capping layers enable a higher level of surface passivation and higher thermal stability compared to SiN x . When implemented in multi-layer stacks, Al 2 O 3 acts as a hydrogen diffusion barrier und prevents effusion from the TOPCon structure that deteriorates the passivation quality irreversibly. • Hydrogenation of poly-Si based passivating contacts. • Thermal activation of hydrogenation. • Hydrogenation of TOPCon using AlOx/SiNx stacks. • Thermal stability of hydrogenation upon fast-firing.