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 s toichiometric and silicon-rich silicon dioxide and silicon nitride films wa s studied using real time ellipsometry. The time of the appearance of the f irst stable Si nuclei, the incubation time (t(inc)), was found to vary with the Si content within a film type (oxide or nitride) and also t(inc) varie d for different film types with the shortest t(inc) for Si-rich silicon nit ride films. Differences between Si bound (to O or N)and free Si (bound to S i) were observed with free Si being more effective at promoting nucleation. Anion screening effects might also yield second order reactivity differenc es. (C) 1999 American Vacuum Society. [S0734-2101(99)01603-6].