Process characterization of plasma enhanced chemical vapor deposition of silicon nitride films with disilane as silicon source

Process characterization details are reported for the first time, to the best of our knowledge, for plasma enhanced chemical vapor deposition of silicon nitride films using disilane as silicon source. Respectable deposition rates have been realized even under the conditions of low mass flow rates of disilane (<1 sccm) and large dilution of process gases with helium. The film uniformity (< +/- 3% thickness variation across 4 in, diameter wafers) and process repeatability in this gas system were found to be excellent. The deposition rates were examined as a function of gas flow ratio, rf power, process pressure, and deposition temperature. Similar to a silane based process, two regimes of operation, namely ammonia-rich and disilane-rich, were identified. Films deposited at the boundary of these two regimes were nitrogen rich and had deposition rates that were dependent only on disilane to ammonia flow ratio and rf power and nearly independent of process pressure and deposition temperature. The hydrogen concentration of these films was found to be nearly constant over the investigated range of ammonia to disilane, flow ratio values varying from 4 to 20. Also, the variation in H concentration in these films with deposition temperature was smaller than what is reported for silane based films. The choice for process parameters based on rf power, utilization of disilane, deposition rate, and film stoichiometry is given. (C) 1998 American Vacuum Society.