Ellipsometric investigation of nucleation sites for chemical vapor deposition of Si on SiO2 and Si3N4 surfaces

The nucleation of polycrystalline silicon by chemical vapor deposition on stoichiometric and silicon-rich silicon dioxide and silicon nitride films was studied using real time ellipsometry. The time of the appearance of the first stable Si nuclei, the incubation time (tinc), was found to vary with the Si content within a film type (oxide or nitride) and also tinc varied for different film types with the shortest tinc for Si-rich silicon nitride films. Differences between Si bound (to O or N) and free Si (bound to Si) were observed with free Si being more effective at promoting nucleation. Anion screening effects might also yield second order reactivity differences.