Effects of the Final Oxidation Step on N and O Distributions in Silicon Oxide/Nitride/Oxide Ultrathin Films

Abstract

Isotopic tracing was used to determine the distribution of O and N after the final fabrication step of ultrathin silicon oxide/nitride/oxide (ONO) films, revealing how the processing parameters affect the characteristics of the resulting structure. ONO films were prepared on precleaned Si wafers in three steps: (i) thermal oxidation in dry , at 1000°C in a rapid thermal processing furnace; (ii) remote plasma enhanced chemical vapor deposition of a nitrade layer in a mixture of and silane, and (iii) a second thermal oxidation step in a Joule‐effect heated furnace, in dry , at three different temperatures and for three different times. Nuclear reaction analysis and narrow nuclear resonance depth profiling with nanometric resolution were used to determine the distribution of , , and in the samples, before and after the reoxidation step. It is shown that the final structure is not a stacked one, but rather a silicon oxynitride ultrathin film with variable composition, presenting moderate concentrations of N in the near‐surface and near‐interface regions, and a higher N concentration in the bulk. Long treatments at high temperatures produce a significant loss and redistribution of N. © 1999 The Electrochemical Society. All rights reserved.