Correlation of time-dependent nonlinear response with phosphorus concentration in Si ultrathin film

Non-destructive analysis of dopant concentration is crucial in the process control of advanced semiconductor fabrication. Here, the dopant concentration of doped Si ultrathin film (DSUTF) which is around 10 nm is evaluated non-destructively by second harmonic generation (SHG). The technique is based on analyzing the evolution of the internal photoemission induced charge trapping and the concomitant electric field induced SHG. We further demonstrate a strategy to estimate the dopant concentration by considering the Fermi-Dirac distribution and the tunneling probability, without involving the crystallinity of DSUTF. The dopant concentration between 1017 and 1020 (atom/cm3) is unambiguously evaluated by this method. The unprecedented approach of using non-destructive method to reveal dopant concentration of DSUTF via time-dependent SHG constitutes an important step towards in-line monitoring and optimizing the fabrication conditions.