Comprehensive Model of Hydrogen Transport into a Solar Cell during Silicon Nitride Processing for Fire-Through Metallization

A mechanism for the transport of H into a Si solar cell during plasma-enhanced chemical vapor deposition (PECVD) of a hydrogenated silicon nitride (SiN:H) layer and its subsequent fire-through metallization process is described. The PECVD process generates process-induced traps, which 'store' H at the surface of the solar cell. This stored H is released and diffuses rapidly into the bulk of Siduring the high-temperature metallization-firing process. During the ramp-down, the diffused H associates with impurities and defects and passivates them. The firing step partially heals up the surface damage. The proposed model explains a variety of observations and experimental results.