Application of IR variable angle spectroscopic ellipsometry to the determination of free carrier concentration depth profiles

Free carrier concentration profiles were determined by Fourier Transform Infrared (FTIR) variable angle spectroscopic ellipsometry. The technique exploits carrier absorption in the mid-infrared spectral range and combines the sensitivity of ellipsometry with a simple Drude free carrier absorption model to determine the carrier profile. In this study, the carrier profiles were modeled as graded multilayers that were constrained to a specific functional form (e.g. Gaussian, complementary error function) when appropriate. Carrier profiles from boron and arsenic ion-implanted that had been subjected to furnace or Rapid Thermal Annealing (RTA) annealed silicon wafers were compared to Spreading Resistance Probe and Secondary Ion Mass Spectrometry profiles. p−p+doped epitaxial silicon samples (before and after annealing) were also measured and the results were compared to theory.