We observe an improvement in the passivation quality of silicon nitride (SiNx) films formed on crystalline silicon wafers by catalytic chemical vapor deposition (Cat-CVD) under the storage at room temperature. Fluorescent light illumination enhances the improvement in the passivation quality of Cat-CVD SiNx films, although the passivation quality is also improved in the dark. We do not see any change of bonding configurations in the SiNx films by the storage at room temperature. Capacitance-voltage measurement reveals that an increase in positive charge density in the SiNx films improves their passivation quality. The improvement in the passivation quality of SiNx films is observed for SiNx films deposited at various substrate temperatures, and SiNx films deposited at higher temperature tends to show more significant improvement in the passivation quality.