Carrier-induced degradation (CID) of multicrystalline silicon (mc-Si) solar cells has been receiving significant attention; however, despite this increasing interest, the defect (or defects) responsible for this degradation has not been determined yet. Previous studies have shown that the surface passivation layer and the firing temperature have a significant impact on the rate and extent of this degradation. In this paper, we further study this impact through an investigation of the CID behavior of the mc-Si wafers passivated with six different silicon nitride layers, each fired at four different peak temperatures. At low firing temperatures, no significant difference in the CID was identified between the samples with different passivation layers; however, a large range of degradation extents was observed at higher firing temperatures. Using Fourier transform infrared spectroscopy, a correlation was found between the degradation extent and the amount of hydrogen released from the dielectric during firing. We verified that no degradation of the surface passivation quality occurred, indicating that the degradation is primarily associated with a bulk defect.