DETERMINING THE CHARGE PROPERTIES OF REOXIDIZED, LIGHTLY NITRIDED OXIDES USING SURFACE-CHARGE ANALYSIS

The changes in charge properties such as total fixed charge and interface state density as a result of nitridation and reoxidation of ultra-thin thermally grown oxides have been measured using a commercially available, optically based technique known as surface charge analysis (SCA). Charge data regarding both nitridation and reoxidation are consistent with those found in the literature thus indicating that SCA can be a viable tool for rapid and real-time analysis of the charge properties of ultrathin RNO dielectrics. The results further indicate that, when reoxidation time is larger than the nitridation time, total fixed charge during reoxidation of nitrided oxides obeys a universal curve which depends only on the ratio of reoxidation time to nitridation time. This is consistent with the previously reported universal curve concerning the growth rate during reoxidation of nitrided samples. When the ratio is as high as six, the recovery appears to be nearly complete and almost identical to the total fixed charge for the initial oxide prior to nitridation. As for interface state density, no such dependence is observed.