During crystallization of multicrystalline silicon, carbon-rich liquid-solid phase-boundary layers appear, resulting in precipitation of n-type conductive Si-C-N filaments. We present an in-depth structural analysis of distinct types of filaments to support modeling of their growth. Phase-contrast microtomography down to the submicron level is used to study morphology and seeding of precipitates while still embedded in fully functional solar cell samples. A detailed transmission electron microscopy analysis and a quantitative electron energy loss spectroscopy analysis are presented, based on tomography-assisted target preparation.