The effect of processing parameters on the weight loss of the silicon solid precursor (Na2SiF6) and the deposition characteristics and morphology of Si3N4 formed onto SiCp/Si porous substrates by CVD has been investigated. The results show that the weight loss of Na2SiF6 is most significantly affected by the processing temperature, followed by the processing time and the type of nitrogen precursor. Formation of Si3N4 is mostly influenced by the substrate temperature, followed by the type of nitrogen precursor and processing time. An increase in processing time and temperature from 60 to 120 min and from 900 to 1300 oC, respectively, favors dissociation of Na2SiF6 and formation of Si3N4. Moreover, N2 enhances Na2SiF6 dissociation and hampers Si3N4 formation, while the N2-NH3 mixture hinders the solid precursor dissociation and favors Si3N4 formation. With regard to microstructure evolution, it is found that in N2 the amount of Si3N4 increases with temperature and the morphology changes from wool-like and light fibers to thicker and compact fibers. When N2-NH3 is used and the processing temperature is increased, the morphology of Si3N4 is modified from deposits with wool-like and compact appearance to whiskers and spheres and finally to thick and compact fibers.