Optimization of bimodal nitrogen concentration profiles in silicon oxynitrides

Since the presence of nitrogen is responsible for highly desirable properties of silicon oxynitrides in the ultra-large-scale integration era, the amount, position, and concentration profile of N in these films are of great interest. In this regard, we have studied several processing sequences (using successive oxynitridation/oxidation/oxynitridation steps) in order to obtain a bimodal N concentration profile with one peak close to the dielectric/Si interface and the other near the top surface of the dielectric. At 900 degrees C and 1 atm, it is found that the first oxynitridation step is required to incorporate less than a "critical'' amount of N so that a bimodal profile is eventually obtained. Suggestions on how to optimize the concentration and profile of N within the silicon oxynitride film through process-property relationships are presented. Further, the flexibility in N incorporation offered by a mixed ambience of nitrous oxide (N2O) and nitric oxide (NO) coupled with the observation that pure NO processing incorporates about one order of magnitude more nitrogen than pure N2O processing could indeed result in novel approaches in designing and optimizing the chemical (electrical and physical) properties of the oxynitrides. Such results may have significant implications for microelectronic applications of the silicon oxynitridation technology. (C) 1999 American Institute of Physics. [S0021-8979(99)08815-5].