Grazing incidence x-ray fluorescence and secondary ion mass spectrometry combined approach for the characterization of ultrashallow arsenic distribution in silicon

Dopant depth profiling and dose determination are essential for ultrashallow junction technology development. However they pose a challenge to the widely used dynamic secondary ion mass spectroscopy (SIMS) technique that suffers uncertainties due to an initial transient width comparable to the dopant depth distribution. In this work the authors report on the application of grazing incidence x-ray fluorescence (GIXRF) for arsenic in silicon dose and profile determination and its combination with SIMS in order to try to overcome the limitations of the latter in the topmost few nanometers. A polynomial variation of the sputtering rate is supposed in the first sputtering stage of the SIMS analysis and the parameters that regulate the magnitude of such correction are determined by a least square fitting of the angle dependent fluorescence signal. The total retained fluence was also measured by instrumental neutron activation analysis and synchrotron radiation soft x-ray GIXRF. The comparison among the total retained fluence determinations shows a good agreement among the techniques. Furthermore, from this first set of measurements it was clearly shown that the GIXRF profile correction is very sensitive to the SIMS profile in the very first nanometers. Therefore if matrix effects are present in the SIMS analysis beside the sputtering rate change, the tested sputtering rate correction can produce nonreliable profiles.